Engine control system for watercraft

[00002] This application is a Continuation-in-Part claiming priority to U.S. patent application Ser. No. 09/908,364 filed Jul. 18, 2001, now U.S. Pat. No. 6,517,394 and also claims priority to Japanese Patent Application No. 2000-219522, filed Jul. 19, 2000, the entire contents of which is hereby expressly incorporated by reference.

[00003] 1. Field of the Invention

[00004] This invention relates to a personal watercraft, and particularly to an improved engine control system for a personal watercraft.

[00005] 2. Description of the Related Art

[00006] Personal watercraft have become popular in recent years. This type of watercraft is sporting in nature and carries a rider and possibly one or more passengers. A relatively small hull of the personal watercraft commonly defines a rider's area above an engine compartment. An internal combustion engine frequently powers a jet propulsion unit that propels the watercraft. The engine lies within the engine compartment in front of a tunnel (e.g., a recess) formed on the underside of the watercraft hull. The jet propulsion is located within the tunnel and is driven by a driveshaft. The driveshaft usually extends between the engine and the jet propulsion device through a wall of the hull tunnel.

[00007] Personal watercraft often are operated in a planing state at wide open throttle. In a planning state, the hull of the personal watercraft supports the weight of a watercraft by planing or “skipping” over the surface of the water. However, if the speed of the personal watercraft suddenly decreases, the planing hull typically begins to “dig” into the water, and drag on the hull significantly increases. If the speed of the watercraft continues to drop, the watercraft hull will experience less and less planing support, and will eventually essentially operate as a displacement-type hull and the speed of the watercraft will be significantly reduced. Personal watercraft usually begin to plane at engine speeds of approximately 2000-3500 RPM.

[00008] While planing, it is not uncommon for the personal watercraft to jump out of the water. When this occurs, the engine speed suddenly increases because the hull is no longer substantially affected by water resistance. If this occurs, the engine speed can exceed a maximum value. This is generally undesirable and can result in damage to engine of the personal watercraft. As such, some personal watercraft include engine speed or “rev” limiting arrangements. In such arrangements, the engine speed is reduced when an engine speed sensor indicates that the engine is operating at an engine speed greater than the maximum value.

[00009] Personal watercraft are commonly powered by two-cycle engines, which have the advantage of being fairly powerful and relatively light and compact. However, two-cycle engines typically produce exhaust gases with relatively large quantities of carbon monoxide and various hydrocarbons. To reduce these emissions, personal watercraft typically include an exhaust system with a catalyst for cleaning the exhaust gases. One disadvantage of using a catalyst in a personal watercraft is that if the exhaust gases exceed a maximum temperature (e.g., 1000° C.), the catalyst can be damaged and/or the effectiveness of the catalyst is impaired. Such high exhaust gas temperatures can occur when the personal watercraft is planing for long periods at wide open throttle or if the engine speed suddenly increases such as when the watercraft jumps out of the water as described above.

[00010] An aspect of the present invention is the realization that prior art engine speed limiting arrangements tend to cause the personal watercraft to suddenly decelerate from the planing state. This is generally undesirable. As such, a need exists for a personal watercraft with an improved engine control system that prevents damage to the engine and/or the exhaust system without causing the personal watercraft to decelerate from the planing state.

[00011] One aspect of the present invention is a method for operating an engine speed limiting arrangement of a small watercraft. The small watercraft includes a hull, an internal combustion engine, at least one engine condition sensor and an electronic control unit, which is in electrical communication with the engine condition sensor. The hull defines an engine compartment in which the engine is supported. The method comprises sending a signal from the engine condition sensor to the electronic control unit, determining if the engine condition sensor indicates an abnormal engine condition, and regulating an engine speed of the engine such that the engine speed remains between a maximum value above which the engine can be damaged and a minimum value below which the watercraft will no longer stay in a planing state. In one modified embodiment, the engine condition sensor is a temperature sensor positioned in an exhaust system of the watercraft. In such an embodiment, the abnormal engine condition can be an exhaust gas temperature above 1000° C. In another modified embodiment, the engine condition sensor is an engine speed sensor. In such an embodiment, the abnormal engine condition can be an engine speed above 7500 revolutions per minute.

[00012] Another aspect of the present invention is a small watercraft that comprises a hull, an internal combustion engine and an engine speed limiting arrangement. The hull defines an engine compartment in which the engine is supported. The engine speed limiting arrangement comprises an engine condition sensor and an electronic control unit that is operatively connected to the engine condition sensor. The electronic control unit is configured to receive a signal from the engine condition sensor to determine if the engine condition sensor indicates an abnormal engine condition, and to regulate the engine speed of the engine such that the engine speed remains between a maximum value above which the engine can be damaged and a minimum value below which the watercraft will no longer stay in a planing state. In one modified embodiment, the engine condition sensor is a temperature sensor positioned in an exhaust system of the watercraft. In such an embodiment, the abnormal engine condition can be an exhaust gas temperature above 1000° C. In another modified embodiment, the engine condition sensor is an engine speed sensor. In such an embodiment, the abnormal engine condition can be an engine speed above 7500 revolutions per minute.

[00013] Yet another aspect of the present invention is a small watercraft that comprises a hull, an internal combustion engine and an engine speed limiting arrangement. The hull defines an engine compartment in which the engine is supported. The engine speed limiting arrangement comprises means for regulating an engine speed of the watercraft so as to alleviate an abnormal engine condition without causing the watercraft to drop below a planing speed. In one modified embodiment, the abnormal engine condition is an exhaust gas temperature that exceeds a maximum value. In another modified embodiment, the abnormal engine condition is an engine speed that exceeds a maximum value.

[00014] Further aspects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments.

[00024] With reference initially to FIG. 1, an overall configuration of a personal watercraft 20 will be described.

[00025] The watercraft 20 employs an internal combustion engine 22 with an engine control system 24 (see FIG. 2) configured in accordance with a preferred embodiment of the present invention. The described engine control system 24 has particular utility with the personal watercraft, and thus, is described in the context of the personal watercraft. However, certain features and aspects of the described engine control system 24 can be applied to other types of watercrafts as well, such as, for example, small jet boats.

[00026] The personal watercraft 20 includes a hull 34 formed with a lower hull section 36 and an upper hull section or deck 38. Both the hull sections 36, 38 are made of, for example, a molded fiberglass reinforced resin or a sheet molding compound. The lower hull section 36 and the upper hull section 38 are coupled together to define an internal cavity 40.

[00027] The upper hull section 34 includes a hatch cover 48, a control mast 50 and a seat 52 arranged from fore to aft. In the illustrated embodiment, a bow portion 54 of the upper hull section 38 slopes upwardly and an opening is provided through which the rider can access the internal cavity 40. The bow portion 54 preferably is provided with a pair of cover member pieces which are apart from one another along a center plane of the watercraft 20. Preferably, the hatch cover 48 is detachably affixed (e.g., hinged) to the bow portion 54 so as to cover the opening.

[00028] The control mast 50 extends upwardly to support a handlebar 56. The handlebar 56 is provided primarily for controlling the direction in which the water jet propels the watercraft 20. Grips are formed at both ends of the handlebar 56 so that the rider can hold them for that purpose. The handlebar 56 also carries other control units such as a engine output request device (not shown) that is used for control of the running conditions of the engine 22. Preferably, the engine output request device is in the form of a manually operated lever pivotally mounted to the handlebar 56 such that a rider can grip the handlebars 56 and also pivotally manipulate the engine output request device, and thereby change the output of the engine.

[00029] The engine output request device can be in the form of a throttle lever, connected to a throttle valve of the engine with a cable. Alternatively, the engine output request device can be in the form of a pivotally mounted lever and an input sensor, further described below with reference to FIG. 2, configured to detect a position of the lever and to emit a signal indicative of the position of the lever. Such a signal can be used to electronically control the output of the engine, described below in greater detail. The input sensor can be in the form of a motion transducer, or any other device that can be used to monitor position, such as, for example, but without limitation, a potentiometer, or a rheostat. Preferably, the input sensor is waterproof.

[00030] The seat 52 extends along the center plane of the watercraft to the rear of the bow portion 54. The seat 52 also generally defines the rider's area. The seat 52 has a saddle shape and hence a rider can sit on the seat 52 in a straddle-type fashion. A plurality of foot areas (not shown) are defined on both sides of the seat 52 and at the top surface of the upper hull section 38. The foot areas are formed generally flat and are surrounded by gunnels, which are formed by the lower and upper hull sections 36, 38. A cushion supported by the upper hull section 38, at least in principal part, forms the seat 52. Preferably, the seat 52 is detachably attached to the upper hull section 38. An access opening is defined under the seat 52 through which the rider can also access the internal cavity 40. That is, the seat 52 usually closes the access opening. The upper hull section 38 preferably also defines a storage box (not shown) under the seat 52.

[00031] A fuel tank 66 is disposed in the cavity 40 under the front portion of the bow portion 54. The fuel tank 66 is coupled with a fuel inlet port 68 positioned at a top surface of the upper hull section 38 through a duct 69. A closure cap (not shown) closes the fuel inlet port 68. The opening disposed under the hatch cover 48 is available for accessing the fuel tank 66.

[00032] The engine 22 is disposed in an engine compartment defined in the cavity 40. The engine compartment preferably is located under the seat 52, but other locations are also possible (e.g., beneath the control mast or in the bow.) The rider thus can access the engine 22 in the illustrated embodiment through the access opening by detaching the seat 52.

[00033] A plurality of air ducts or ventilation ducts 70 are provided on both sides of the bow portion 54 so that the ambient air can enter the internal cavity 40 therethrough. Except for the air ducts 70, the engine compartment is substantially sealed so as to protect the engine 22 and other components from water.

[00034] In the preferred embodiment, a jet pump system 72 propels the watercraft 20. The jet pump system 72 includes a tunnel 74 formed on the underside of the lower hull section 36. The tunnel 74 has a downward facing inlet port 76 opening toward the body of water. A jet pump housing 78 is disposed within a portion of the tunnel 74 and communicates with the inlet portion 76. An impeller 79 is supported within the housing 78.

[00035] An impeller shaft 80 of the jet pump system 72 extends forwardly from the impeller 79 and is coupled with a crankshaft 82 of the engine 22 by at least in part a coupling member 84. The crankshaft 82 of the engine 22 thus drives the impeller shaft 80. The rear end of the housing 78 defines a discharge nozzle 85. A steering nozzle 86 is affixed to the discharge nozzle 85 for pivotal movement about a steering axis extending generally vertically. The steering nozzle 86 is connected to the handlebar 56 by a cable (not shown) so the rider can pivot the nozzle 86.

[00036] As the engine 22 drives the impeller shaft 80 and hence rotates the impeller 79, water is drawn from the surrounding body of water through the inlet port 76. The pressure generated in the housing 78 by the impeller produces a jet of water that is discharged through the steering nozzle 86. This water jet propels the watercraft 20. The rider can move the steering nozzle 86 with the handlebar 56 when he or she desires to turn the watercraft 20 in either direction.

[00037] The engine 22 of the illustrated embodiment operates on a two-stroke crankcase compression principle. The engine 22 includes a cylinder block, which, in the illustrated embodiment, defines three cylinder bores spaced from each other from fore to aft generally along the center plane of the watercraft. However, it should be appreciated that the illustrated engine merely exemplifies one type of engine on which various aspects and features of the present invention can be used. An engine having other numbers of the cylinders, having other cylinder arrangements, other cylinder orientations (e.g., upright cylinder banks, V-type, W-type) and operating on other combustion principles (e.g., four-cycle, diesel, and rotary) are all practicable.

[00038] As is well known in the art, pistons are suitably journaled for reciprocation within the cylinder bores. A cylinder head preferably is affixed to the upper end of the cylinder block to close respective upper ends of the cylinder bores and defines three combustion chambers with the cylinder bores and the pistons. The cylinder head can be an assembly formed by multiple members or a single head piece. Connecting rods connect the pistons to the crankshaft 82 that is housed within a crankcase member.

[00039] The cylinder block, the cylinder head, and the crankcase member together define and engine body 90. The engine body 90 preferably is made of an aluminum based alloy. In the illustrated embodiment, the engine body 90 is oriented in the engine compartment so as to position the crankshaft 82 in the center plane of the watercraft and to extend generally in the longitudinal direction. Other orientations of the engine body, of course, are also possible (e.g., with a transverse or vertical oriented crankshaft).

[00040] Preferably, a plurality of engine mounts extend from both sides of the engine body 90. The engine mounts preferably include resilient portions made of, for example, a rubber material. The engine 22 preferably is mounted on the lower hull section 36, specifically, a hull liner, by the engine mounts so that vibration of the engine 22 is inhibited from conducting to the hull section 36.

[00041] The engine 22 preferably includes an air induction system to introduce air to the combustion chambers and a throttle system to regulate an amount of air flowing therethough. In a preferred embodiment, the air induction system includes a plurality of throttle bodies that are each associated with a cylinder bore of the engine 22. The throttle bodies are connected to the crankcase member by an intake conduit, such as, for example, a manifold, which preferably is made of a resilient, flexible material (e.g., rubber).

[00042] Each of the throttle bodies includes a throttle valve. Pivotal movement of the throttle valves is controlled by the throttle lever on the handlebar 56 through a control cable that is connected to set of throttle valve shafts. The rider thus can control an opening amount of the throttle valves by operating the throttle lever so as to obtain various running conditions of the engine 22 that the rider desires. That is, an amount of air passing through the throttle bodies is controlled by this mechanism. Alternatively, the throttle system can be electronically controlled, discussed in greater detail below.

[00043] A reed valve selectively allows air into the crankcase member from the throttle bodies and manifold. The crankcase member itself is compartmentalized to provide the crankcase compression features for each combustion chamber as is well known in the operation of two-cycle engines. The charge within the crankcase member is delivered to each combustion chamber through several scavenge passages formed in the cylinder block. The scavenge passages terminate at a number of scavenge ports formed on the cylinder bore.

[00044] The air induction system preferably also includes at least one air intake box, which supplies air to the throttle bodies. The intake box forms a “plenum chamber” for smoothing the intake air and acting as an intake silencer.

[00045] The engine 22 includes a fuel supply system, which includes the fuel tank 66 and a plurality of fuel injectors. In a preferred embodiment, the fuel injectors are mounted to the throttle bodies such that the fuel injectors spray fuel directly into the throttle bodies. Fuel delivery conduits are arranged to supply fuel to the fuel injectors. In one variation, the fuel delivery conduits comprise a fuel rail to which the fuel injectors are attached. In another variations, the fuel delivery conduits can be fuel lines that are connected to the fuel injectors. These fuel lines can be arranged in series or in parallel.

[00046] Those of skill in the art will recognize that the fuel injection system described above is an indirect fuel injection system. That is, the fuel is injected into the induction system of the engine. However, it should be appreciated that in some arrangements the engine could utilize a direct fuel injection system (i.e., a fuel system where fuel is directly injected into the combustion chamber). In other arrangements, the engine can utilize a carburetor, which delivers a generally constant air/fuel ratio during a given intake cycle.

[00047] The fuel injectors 91 (FIG. 2) spray the fuel into the throttle bodies at an injection timing and duration under control of an electronic control unit (ECU) 92 (see FIG. 2), as will be explained in more detail below, forms part of the engine control system 24. During normal operation, the ECU 92 can control the injection timing and duration according to any known fuel control strategy, which preferably responds to a signal from at least one engine sensor, such as, for example, but without limitation, a throttle valve position sensor (not shown).

[00048] Ignition elements 93 (FIG. 2) in the form of, for example, spark plugs are mounted within the cylinder head with their gaps extending into the combustion chambers. During normal operation, the spark plugs are fired by an ignition control unit that is controlled the ECU of the engine 22 according to any known fuel control strategy. The spark plugs are connected to the ignition control unit by spark plug leads (not shown).

[00049] An exhaust system 96 (FIG. 2) is provided for discharging exhaust gases from the engine 22 to the atmosphere and/or to the water. The exhaust system 96 preferably includes exhaust passages (not shown) that are associated each combustion chamber and are formed in the cylinder block. In some arrangements, a sliding type exhaust timing control valve can be provided in the exhaust passages for controlling the timing of the opening and closing of the exhaust passages as is known in the art.

[00050] The exhaust system 96 preferably also includes an exhaust manifold 98, which in the illustrated embodiment is affixed to the port side of the engine body 90. The outlet of the exhaust manifold 98 communicates with an expansion chamber 100, which includes an upstream section 102 and a C-shaped downstream section 104. The upstream section 102 is directly connected to the outlet of the exhaust manifold and extends upwardly and forwardly to the C-shaped downstream section 104. The C-shaped downstream section 104, in turn, wraps around the front of the engine 22 and extends along the starboard side of the engine 22 at an elevation that preferably is generally at or above to the cylinder head. The outlet of the C-shaped section 104 extends generally rearwardly along the starboard side of the engine 22 and is connected to an exhaust pipe 106.

[00051] The exhaust pipe 106 preferably is connected to a first water trap device 108 through a conduit 110. The first water trap device 108 inhibits the back flow of water into the exhaust pipe 106 and into the exhaust system 96 in general. A second exhaust pipe 112 preferably couples to a second water trap device 114. In the illustrated embodiment, the second water trap device 114 is located on a side of the jet pump system 72 opposite the first water trap device 108. As such, the illustrated second exhaust pipe 112 extends up and over the jet pump system 72 and thus further inhibits the influx of water into the exhaust system 96. In the illustrated embodiment, a third exhaust pipe 116 couples the second water trap device 114 to a discharge opening 118 for discharging the exhaust gases to a body of water in which the personal watercraft 20 is operating.

[00052] In the illustrated embodiment, a catalyst assembly 120 is provided between the C-shaped downstream section 104 and the exhaust pipe 106. Preferably, the catalyst assembly 120 includes a catalyst 122, such as, for example, a honeycombed-type catalyst bed designed for treating hydrocarbons, carbon monoxide and nitrogen oxides. The exhaust system 96 preferably includes a cooling jacket, which defines cooling passages (not shown) that surround the outlet of the C-shaped downstream section 104, the catalyst assembly 120 and the exhaust pipe 106. The cooling passages serve to cool the exhaust gases before they are discharged.

[00053] The engine 22 also preferably includes a lubricating system for providing lubricant to various engine parts and a cooling system for cooling the engine 22. These systems are well known in the art.

[00054] FIG. 2 is a schematic illustration a portion of the engine control system 24. The engine control system 24 generally comprises the ECU 92 and various actuators and sensors that are operatively connected to the ECU 92. The engine control system controls 24 various aspects of engine operation. For example, as mentioned above, during normal operation, the engine control system 24 controls the firing of the spark plugs 93 and the injection timing and duration of the fuel injectors 91. As is well known, to appropriately control the engine 22 under various operating conditions, the engine control system 24 preferably utilizes maps and/or indices stored within the memory of the ECU 92 with reference to data collected from various sensors. For example, the engine control system 24 may refer to data collected from a throttle valve position sensor and other sensors provided for sensing engine running conditions, ambient conditions or conditions of the watercraft 20 that may affect engine performance.

[00055] It should be noted that the ECU 92 may be in the form of a hard-wired feedback control circuit that performs the operations described below. Alternatively, the ECU 92 may be constructed of a dedicated processor and a memory for storing a computer program configured to perform the operations described below. Additionally, the ECU 92 may be a general purpose computer having a general purpose process and the memory for storing a computer program for performing the operations described below.

[00056] The portion of the engine control system 24 illustrated in FIG. 2 is an engine speed limiting arrangement 128 configured so as to reduce the engine speed of the engine 22 in response to an abnormal engine condition. Preferably, the engine speed limiting arrangement 128 is configured such that when an abnormal engine condition is sensed the engine speed is reduced only to such an extent that watercraft 20 will remain in a planing state. In the illustrated embodiment, the engine speed is reduced by sequentially disabling cylinders of the engine 22. While the cylinders are being sequentially disabled, the engine speed limiting arrangement monitors engine conditions and prevents the watercraft 20 from leaving the planing state.

[00057] As shown in FIG. 2, the engine speed limiting arrangement 128 includes one or more engine condition sensors 130. In the illustrated embodiment, the engine condition sensors 130 include an exhaust gas temperature sensor 132 and an engine speed sensor 134. The exhaust gas temperature 132 is configured to indicate the temperature of the exhaust gases. As such, the exhaust gas temperature sensor 132 is preferably disposed within the exhaust gas system 96. As shown in FIG. 1, in the illustrated embodiment, the exhaust gas temperature sensor 132 is positioned in the exhaust pipe 106.

[00058] The engine speed sensor 134 is configured to sense the engine speed of the engine 22. For example, in some arrangements, the engine speed sensor 134 can be configured to sense the rotational speed of the crankshaft 82 through, by way of example, sensing the rotation of a pulsar coil.

[00059] As noted above, the throttle system of the watercraft 20, which can include one or a plurality of throttle valves, can be electronically controlled. For example, the watercraft 20 can include an input sensor 136 which is configured to detect a position of the input lever mounted on the handlebar 56. The input sensor 136 is configured to detect the position of the lever and generate a signal indicative of the position of the lever. The input sensor 136 is connected to the ECU 92 so as to transmit the signal thereto. In this arrangement, the watercraft 20 also includes a throttle valve actuator 138. The throttle valve actuator 138 can be in the form of any electronic actuator, such as, for example, but without limitation, a solenoid, stepper solenoid, stepper motor, servo motor, and the like. The actuator 138 is connected to the ECU 92 through a control line.

[00060] Preferably, the watercraft 20 also includes a throttle position'sensor 140. The throttle position sensor 140 is connected to the throttle valve and/or the throttle valve actuator 138 and is configured to detect a position thereof. For example, the throttle position sensor 140 can be configured to detect a rotational position of a shaft to which the throttle valve is mounted or to an output shaft of the actuator 138. Additionally, the throttle position sensor 140 is configured to generate a signal indicative of the position of the throttle valve or the actuator 138.

[00061] The throttle position sensor 140 is connected to the ECU 92 so as to transmit the signal thereto. For example, a typical throttle position sensor is a potentiometer. In this variation, the ECU 92 is configured to sample the resistance of the voltage across the potentiometer 140 and to convert this information into a throttle valve opening. Where the throttle system is electronically controlled, the throttle position sensor 140 can be used to provides the additional function of ensuring the accuracy of the actuator 138. For example, if the actuator 138 does not accurately reproduce the throttle position dictated by the ECU 92, the throttle position sensor 140 will detect the actual position of the throttle valve, and the ECU 92 can use the actual position to correct the throttle valve position by causing the actuator 138 to move the throttle valve.

[00062] The speed limiting arrangement 128 can optionally be configured to incorporate the input sensor 136, the actuator 138, and the throttle position sensor 140. The operation of the speed limiting arrangement 128 with the sensors 136, 140 and the actuator 138 as well as the operation of the speed limiting arrangement 128 independently from these components, is described in greater detail below.

[00063] In the illustrated embodiment, the engine speed limiting arrangement 128 is a subsystem of the engine control system 24. That is, the engine speed limiting arrangement 128 shares several components with the engine control system 24, such as, for example, the ECU 92 and the engine speed sensor 134 and the exhaust gas temperature sensor 132, as well as optionally the sensors 136, 140 and the actuator 138. However, it should be appreciated that the engine speed limiting arrangement 128 could include separate components or be entirely separate from the engine control system 24. Preferably, the engine speed limiting arrangement is a subsystem of the engine control system 24 because this arrangement reduces the number of parts and the cost of the watercraft 20.

[00064] FIG. 3 illustrates the engine 22 in the form of a three cylinder, four-stroke engine, identified generally by the reference numeral 22′. Certain of the components of engine 22′ are identified using the same reference numerals used to identify corresponding components of the engine 22 illustrated in FIG. 1. However, one of ordinary skill in the art will understand that such components of the engine 22′ are configured for operation under the four-stroke combustion principle.

[00065] As noted above, the engine 22′ operates on a four-stroke combustion principle. The engine 22′ comprises cylinder block 150 that defines three cylinder bores 152. The engine 22′ thus is an L3 (in-line three cylinder) type engine. However, the engine 22′ can have other numbers of cylinders and can have other cylinder arrangements (V and W type). Additionally the engine 22′ can be oriented with other cylinder orientations, e.g., inclined or horizontal cylinder banks are all practicable.

[00066] The pistons (not shown) are reciprocally disposed within each of the cylinder bores 152. A cylinder head member (shown partially) is affixed to an upper end of the cylinder block 150 to close the respective upper ends of the cylinder bores 152. Together with the cylinder block 150, the cylinder head defines combustion chambers with the cylinder bores 152 and the corresponding pistons.

[00067] A crankcase member (not shown) is affixed to a lower end of a cylinder block 150 to close the respective lower ends of the cylinder bores 152 and to define a crankcase chamber with the cylinder block 150. A crankshaft (not shown) is journalled for rotation by the crankcase member. Connecting rods (not shown) couple the crankshaft with the piston so that the crankshaft rotates with reciprocal movement of the pistons.

[00068] The cylinder block 150, the cylinder head member, and the crankcase member together define the body of the engine. The engine body preferably is made of an aluminum-based alloy.

[00069] Optionally, the engine 22′ can include an output shaft 154 that is driven by the crankshaft through a gear reduction set (not shown). The gear reduction set thereby allows the engine 22′ to operate at a higher RPM than the RPM of the output shaft 154, and therefore, higher than the rotational speed of the impeller 79.

[00070] In the illustrated embodiment, the engine body is oriented in the engine compartment 40 to position the output shaft 154 coaxially with the driveshaft 80. In other arrangements, other orientations of the engine body are also possible (e.g., with a transverse or vertically oriented crankshaft).

[00071] Engine mounts (not shown) extend from either side of the engine body. The engine mounts preferably include resilient portions made of flexible material, for example, a rubber material. The engine body is mounted in the lower hull section 36, and more preferably, to a hull liner (not shown) by the engine mounts so that vibrations from the engine 22′ are attenuated.

[00072] The watercraft 20 also includes an air induction system 156 configured to guide air to the engine body for combustion therein. The engine body includes three inner intake passages or “ports” 158 defined in the cylinder head. The intake passages 156 communicate with the associated combustion chambers. In the illustrated embodiment, each of the intake ports 158 split into two passages leading to two intake valves 159 for each of the cylinders 152.

[00073] The air induction system 156 includes a first intake air chamber 160 disposed in the engine compartment 40 and including an opening which opens into the engine compartment 40, or another compartment defined by the hull. The illustrated air induction system 156 also includes a second air chamber 162 which is connected through the first intake air chamber through a conduit 164.

[00074] The second intake air chamber 162 communicates with the intake ports 158 through three intake runners 166, one for each of the cylinders 152. Each of the intake runners 166 open into the second intake air chamber 162. Optionally, the induction system can include an air filter 168. In the illustrated embodiment, the air filter 168 is disposed in the first air intake chamber 160.

[00075] The induction system 156 also includes a throttle system having at least one throttle valve. In the illustrated throttle system, one throttle valve 170 is disposed in each of the intake runners 166. Thus, a portion of each of the intake runners 166 defines a throttle body for the throttle valves 170. Each of the throttle valves 170 are mounted on a shaft and thus form butterfly-type throttle valves within the intake passages 166.

[00076] The throttle valves can be connected to a throttle lever on the handlebar 56 by a cable as is well known in the art. Preferably, the throttle valves 170 are controlled by at least one electronic actuator 171, thus allowing the throttle system to be electronically controlled. In the illustrated embodiment, there is one actuator 171 for each of the throttle valves 170. The electronic actuators 171 can be any type of electronic actuator, such as, for example, but without limitation, stepper motors or servomotors.

[00077] The watercraft 20 also includes a fuel delivery system. In the illustrated embodiment, the fuel delivery system comprises a induction fuel injection system which injects fuel into a portion of the intake runners 166 adjacent the engine body. This fuel supply system comprises three fuel injectors 172, one for each of the cylinders 152. The fuel injectors 172 are connected to a fuel rail (not shown) which supplies pressurized fuel to the fuel injectors 172. The fuel injectors 172 have injection nozzles opening downstream of the throttle valves 170.

[00078] The fuel injectors 172 spray fuel at a certain timing and duration under the control of an electronic control unit (ECU) and is discussed in greater detail below. The sprayed fuel is drawn into the combustion chambers together with air from the induction system 156 to form air fuel charges. The direct fuel injection system that sprays fuel directly into the combustion chambers can be used in place of the illustrated induction fuel injection system. Alternatively, other charge forming devices such as, for example, carburetors can be used instead of a fuel injection system.

[00079] The watercraft 20 shown in FIG. 3 also includes a firing or ignition system. The ignition system includes three sparkplugs (not shown), one for each of the cylinders 152. The sparkplugs are affixed to the cylinder head of the engine 22′ so that their electrodes, which are defined at the inner ends of the sparkplugs, are exposed to their respective combustion chambers within the cylinders 152. Sparkplugs fire air fuel charges in the combustion chambers at a timing under the control of the ECU. The air fuel charges thus burned within the combustion chambers to move the pistons generally downwardly.

[00080] The engine 22′ also includes an exhaust system 173 configured to guide burnt air fuel charges, i.e., exhaust gases, from the combustion chambers. In the illustrated embodiment, the engine body includes three inner exhaust passages 174 extending from an outer surface of the engine body to the combustion chamber. In the illustrated embodiment, each of the inner exhaust passages 174 are divided at their inner ends and terminate at two exhaust valve seats at which exhaust valves 183 control the flow of exhaust gases out of the cylinders 152.

[00081] The exhaust system 173 also includes an exhaust manifold 175. The exhaust manifold 175 connects each of the inner exhaust passages 174 and merges them into a common passage defined by the manifold 175. Alternatively, the manifold 175 can include a plurality of individual inner exhaust passages.

[00082] In the illustrated embodiment, the exhaust manifold 175 is connected to the port side of the engine body 150 and curves rearwardly toward an aft of the watercraft 20. At a downstream end of the exhaust manifold, the exhaust system 173 includes a catalyst device 176. Downstream from the catalyst device 176, the exhaust system 173 includes an exhaust gas temperature sensor 177 for monitoring the temperature of the exhaust gases flowing therethrough, discussed below in greater detail.

[00083] The exhaust system 173 preferably also includes any of a plurality of additional exhaust silencing and/or cooling devices commonly used in the art. For example, the exhaust system can include resonator chambers for quieting the sounds associated with the exhaust gases, as well as water traps for preventing water from flowing upstream through the exhaust system towards the engine.

[00084] The engine 22 also includes a valve train drive for actuating the intake and exhaust valves 159, 175. The valve train drive preferably comprises double overhead camshafts including the intake camshaft (not shown) and an exhaust camshaft (not shown). The intake and exhaust camshafts actuate the intake and exhaust valves 159, 175, respectively.

[00085] The intake camshaft extends generally horizontally over the intake valves 159 from fore to aft along the engine body 150. The exhaust camshaft extends generally horizontally over the exhaust valves 175 parallel to the intake camshaft.

[00086] Both the intake and exhaust camshafts are journalled for rotation in the cylinder head with the plurality of camshaft caps. The camshaft caps holding the camshaft are affixed to the cylinder head. A cylinder head cover member (not shown) extends over the camshafts and the camshaft caps, and is affixed to the cylinder head to define a camshaft chamber.

[00087] The intake and exhaust camshafts each have cam lobes. Each cam lobe is associated with each one of the intake valves 159 and the exhaust valves 175, respectively. The intake and exhaust valves 159, 175 are biased to a closed position via, for example, springs. When the intake and exhaust camshafts rotate, the respective lobes push the associated valves 159, 172 to open the respective ports against the biasing force of the springs. The air thus can enter the combustion chambers when the intake valves 159 are opened and the exhaust gases can move out of the combustion chambers when the exhaust valves 175 are opened.

[00088] The crankshaft of the engine 22′ preferably drives the intake and exhaust camshafts. Preferably, the camshafts have driven sprockets affixed to ends thereof. The crankshaft also has a drive sprocket. Each driven sprocket has a diameter which is twice as large as a diameter of the drive sprocket. A flexible transmitter such as, for example, a timing chain or belt is wound around the drive and driven sprockets. When the crankshaft rotates, the drive sprocket drives the driven sprockets via the timing chain or belt, and thus the intake and exhaust camshafts also rotate. The rotational speed of the camshafts are reduced to half of the rotational speed of the crankshaft because of the difference in diameters of the drive and driven sprockets.

[00089] A tensioner of the flexible transmitter is provided to give a proper tension to the transmitter. A tension adjuster is provided to adjust the tension of the tensioner. The tension adjuster exposes itself at a sideboard of the cylinder head, preferably, on the starboard side.

[00090] The engine 22′ preferably also includes a lubrication system that delivers lubricant, such as oil, to the engine portions for inhibiting frictional wear of such portions. Preferably, a closed-loop type lubrication system as employed. Lubricant oil for the lubrication system preferably is stored in a lubricant reservoir or tank disposed in the engine compartment 40.

[00091] The watercraft 20 also preferably includes a cooling system for cooling the engine body 150 and the exhaust system 173. Preferably, the cooling system is an open-loop type system that introduces cooling water from the body of water in which the watercraft is operating. The cooling system can include a water pump and the plurality of water jackets under conduits. Alternatively, the cooling system can be partially closed-loop. For example, the engine body 150 can be cooled with a closed-loop type cooling system and the exhaust system 173 can be cooled with an open-loop type cooling system.

[00092] In the illustrated embodiment, pressurized water from the jet pump 72 is directed to the engine body 150 for cooling purposes. The water from the jet pump flows through cooling conduits 178 defined in the engine body 150. The cooling conduit 178 directs water to water jackets 179 disposed around the cylinders 152. Thus, the cylinders 152 are cooled with water from the jet pump.

[00093] In the illustrated embodiment, some of the water from the cooling jackets 179 is directed into the cooling jacket 180 disposed over the exhaust manifold 175. This cooling water flows from the upstream end of the exhaust manifold past the catalyst device 176 to a discharge port 181 disposed downstream of the catalyst device 176. At the discharge port 181, water from the cooling jacket 180 is discharged into the exhaust gases flowing through the exhaust system 73. This mixing of water into the exhaust gases helps to cool and quiet the exhaust gases flowing therethrough.

[00094] In operation, ambient air enters the engine compartment 40 through the air ducts 70. The air is then introduced into the first intake chamber 160, passes through the air filter 168, the conduit 164 and into the second air chamber 162. The air flowing through the second intake air chamber 162 is divided into three air flows, each flowing into one of the intake runners 166.

[00095] The throttle valves 170 regulate an amount of air flowing toward the combustion chambers. The air flows into the combustion chambers when the intake valves 159 are opened. At the same time, the fuel injectors 166 spray fuel into the intake runners 166 under the control of the ECU. Air fuel charges are thus formed and are delivered to the combustion chambers.

[00096] The air fuel chargers are fired by the sparkplugs also under the control of the ECU. The burnt charges, i.e., exhaust gases, are discharged to the body of water surrounding the watercraft through the exhaust system 173. The combustion of the air fuel charges causes the pistons to reciprocate within the cylinders 152 and thereby causes the crankshaft to rotate. The crankshaft drives the output shaft 154 and thus drives the driveshaft 80 through the coupling 84.

[00097] FIG. 4 illustrates the engine speed limiting arrangement 128′ which is part of the ECU of the engine 22′. The other functions of the ECU of the engine 22′ with respect to normal fuel injection and ignition control is similar to that described above with respect to the ECU 92 illustrated in FIG. 2. As illustrated in FIG. 4, the watercraft 20 illustrated in FIG. 3 includes one throttle position sensor 182 for each of the throttle valves 170.

[00098] FIG. 5 illustrates a graphical depiction of a control arrangement having certain features and aspects of the present invention. In this arrangement, when the exhaust gas temperature exceeds a maximum temperature Tmax, one of the cylinders of the engine 22, 22′ is disabled. By disabling one of the cylinders, the engine speed is reduced. For example, if the engine is operating at wide open throttle at an engine speed of approximately 7500 revolutions per minute (RPM), disabling one cylinder will gradually reduce the engine speed to, for example, approximately 6000 RPM. As the engine speed is reduced, the temperature of the exhaust gas is reduced. If the exhaust gas temperature is reduced to a minimum temperature Tmin within a predetermined amount of time, operation of the disabled cylinder can be resumed. If the exhaust gas temperature is not reduced to the minimum temperature Tmin within the predetermined amount of time, a second cylinder is preferably disabled. Disabling a second cylinder will reduce the engine speed from, for example, approximately 6000 RPM to approximately 4000 RPM at wide open throttle. In a similar manner, a third cylinder can be disabled to effectively shut off the engine if the exhaust gas temperature remains above the minimum temperature Tmin. In other arrangements with more than three cylinders, more than three cylinders can be disabled in a manner similar to that described above.

[00099] In general, disabling a cylinder means that the ECU 92 prevents an ignition element 93 (e.g., a spark plug in the illustrated embodiment) from firing so as to prevent combustion in that cylinder. In some arrangements, the ECU 92 may also prevent fuel from being injected through the fuel injector 91 into the cylinder that is being disabled. Such an arrangement helps to prevent fouling of the sparkplug 93 and reduces “blow-by” of unburned fuel into the exhaust gases.

[00100] Optionally, disablement of a cylinder can be accomplished by reducing or closing one or a plurality of the throttle valves of the engine 22. For example, the speed limiting arrangement 128 can be configured to control the actuator 138 so as to close all the throttle valves of the engine 22 so as to limit the engine speed as noted above. Alternatively, the speed limiting arrangement 128 can include a plurality of actuators 138, one for each of the throttle valves of the engine 22. In this arrangement, the speed limiting arrangement 128 can be configured to reduce the opening or close one of the throttle valves while allowing the other actuators 138 to leave the throttle valves in the position corresponding to the output signal of the input sensor 136.

[00101] This alternative provides a further advantage in that by changing an opening amount of any of the throttle valves, combustion in the associated combustion chambers can continue at a desired air fuel ratio. Thus, although the power output associated from a “disabled” cylinder is reduced, the corresponding sparkplugs will not be fouled with an excessively rich air fuel mixture, nor will undesirable particulate deposits be formed from the combustion of non-stochiometric air fuel mixtures.

[00102] In the preferred arrangement, the maximum temperature Tmax is an exhaust gas temperature at which the catalyst 122, 176 can be damaged and/or the effectiveness of the catalyst 122, 176 is impaired. In some arrangements, the maximum temperature Tmax can correspond to an exhaust gas temperature that indicates when the engine speed is greater than a maximum engine speed Rmax. Such a maximum temperature Tmax can be determined empirically, through modeling and/or experiments. In the illustrated embodiment, the maximum temperature is approximately 1000° C., which corresponds to an engine speed of approximately 7500 revolutions per minute (RPM) at wide open throttle.

[00103] In a similar manner, in the preferred arrangement, the minimum temperature is an exhaust temperature at which the catalyst 122, 176 will no longer be damaged and/or the effectiveness of the catalyst 122, 176 is no longer impaired. Moreover, the minimum temperature also corresponds to an engine speed at which the watercraft 20 will still remain in a planing state. Such a minimum temperature can also be determined empirically, through modeling and/or experiments. As mentioned above, personal watercraft typically begin to plane at engine speeds of approximately, 2000-3500 RPM. In the illustrated embodiment, the minimum temperature is approximately 800° C., which corresponds to an engine speed of approximately 3500 RPM such that the watercraft 22 will remain in a planing state.

[00104] FIG. 6 illustrates a control routine 200 that is capable of implementing a control strategy that can achieve control similar to that described graphically in FIG. 5 is illustrated therein. The control routine 200 preferably is executed by the ECU 92 or the CPU of FIG. 4. As shown in FIG. 6 and as represented by an operational block S1, the routine 200 preferably starts when a main switch of the watercraft 20 is turned on. The routine 200 then determines if the exhaust gas temperature is greater than the maximum temperature Tmax as represented by a decisional block S2. Preferably, this involves receiving a signal from the exhaust gas temperature sensor 132, 177. If the exhaust gas temperature is less than the maximum temperature Tmax, then the routine 200 continues to determine if the exhaust gas temperature is greater than the maximum temperature Tmax.

[00105] If the exhaust gas temperature is greater than the maximum temperature Tmax, then one of the cylinders is disabled as represented by an operational block S3. Preferably, this involves preventing the ignition element 93 from firing so as to prevent combustion within the disabled cylinder. More preferably, the ECU 92 also prevents fuel from being injected through the fuel injector 91, 172 and into the disabled cylinder. In this manner, the engine speed of the watercraft 22 and the exhaust gas temperature will be decreased.

[00106] Alternatively, the ECU 92 or the CPU of FIG. 4 can control the throttle valve actuators 138, 171 to close one of the throttle valves so as to disable one cylinder. Preferably, if one of the throttle valves are closed, either completely or to an idle position, the associated fuel delivery component delivers an amount of fuel appropriate for that reduced throttle opening. This prevents non-stochiometric air fuel mixtures from entering the associated cylinder. As a further alternative, the associated fuel injector can be completely shut down so that when the throttle valve is moved to a reduced opening, no fuel is injected into the corresponding cylinder.

[00107] After the first cylinder is disabled, the routine 200 then determines if the exhaust gas temperature is less than the minimum temperature Tmin as represented by a decisional block S4. If the exhaust gas temperature is less than the minimum temperature Tmin, the routine 200 releases control of any disabled cylinder and allows the ignition element 93 to start combustion in the formerly disabled cylinder as represented by an operational block S5. If fuel injection has been stopped, the routine also allows fuel to be injected into the formerly disabled cylinder. Similarly, if the associated throttle valve has been moved to a reduced position, it can be restored to the position corresponding to that detected by the input sensor 136. In this manner, the engine speed no longer decreases and the watercraft 20 is maintained in the planing state. The routine 200 continues to monitor the temperature of the exhaust gas as indicated by an operational block S6, which returns the routine 200 to the decisional block S2.

[00108] If the routine 200 determines that the exhaust gas temperature is greater than the minimum temperature Tmin, then the routine 200 determines if a predetermined amount of time B1 has passed as represented by a decisional block S7. In a preferred arrangement, the predetermined amount of time is approximately 5 seconds. If the predetermined amount of time B1 has not passed, the routine 200 preferably loops back to the decisional block S4. If the predetermined amount of time B1 has passed, a second cylinder is disabled as indicated by an operational block S8. After the second cylinder is disabled the routine loops back to the decisional block S4. It should be appreciated that the routine 200 described above can be modified to sequentially disable all the cylinders of the engine 22 in a manner similar to that of the first two cylinders.

[00109] FIG. 7 illustrates a graphical depiction of a modified control arrangement having certain features and aspects of the present invention. In this arrangement, when the engine speed exceeds a maximum engine speed Rmax, one of the cylinders of the engine 22 is disabled, which reduces the engine speed as described above. If the engine speed is reduced to a minimum engine speed Rmin within a predetermined amount of time, operation of the disabled cylinder can be resumed. If the engine speed is not reduced to the minimum engine speed Rmin within the predetermined amount of time, a second cylinder is disabled. In a similar manner, a third can be disabled. In other arrangements with more than three cylinders can be disabled in a manner similar to that described above. Preferably, at the minimum engine speed Rmin, the watercraft 20 remains in a planing state.

[00110] In the preferred arrangement, the maximum engine speed Rmax is an engine speed above which the engine will be damaged. Such an engine speed can be determined empirically, through modeling and/or experiments. In the illustrated embodiment, the maximum engine speed Rmax is approximately 7500 RPM. The minimum engine speed Rmin is an engine speed at which the engine will no longer be damaged and at which the watercraft 20 will still remain in a planing state. That is, the minimum engine speed Rmin preferably is between Rmax and an engine speed at which the watercraft will cease planing, such as, for example, approximately 3500 RPM. Such a minimum engine speed can also be determined empirically, through modeling and/or experiments. In the illustrated embodiment, the minimum engine speed Rmin is approximately 7300 RPM.

[00111] FIG. 8 illustrates a control routine 250 that is capable of implementing a control strategy that can achieve control similar to that described graphically in FIG. 7. As shown in FIG. 8 and as represented by an operational block S10, the routine 250 preferably starts when a main switch of the watercraft 20 is turned on. The routine 250 then determines if the engine speed is greater than the maximum engine speed Rmax as represented by a decisional block S11. Preferably, this involves receiving a signal from the engine speed sensor 134. If the engine speed is less than the maximum engine speed Rmax, then the routine 250 continues to determine if the engine speed is greater than the maximum engine speed Rmax.

[00112] If the engine speed is greater than the maximum engine speed Rmax, then the routine 250 determines if a predetermined amount of time B2 has passed as represented in a decisional block S12. In a preferred arrangement, the predetermined amount of time B2 is approximately 0.1 seconds. If the predetermined amount of time has not passed, the routine 250 loops back to the decisional block S11. If the predetermined amount of time has passed, one of the cylinders is disabled as indicated by an operational block S13. As such, in the illustrated embodiment, one of the cylinders is disabled only if the engine speed is greater than the maximum engine speed Rmax for a predetermined amount of time. If the engine speed is greater than the maximum engine speed Rmax for less than the predetermined amount of time, then one of the cylinders is not disabled. This arrangement is preferred because operating above the maximum engine speed for less than the predetermined amount of time is unlikely to cause significant damage to the engine and steps taken to reduce the engine speed may result in engine hunting.

[00113] After the first cylinder is disabled, the routine 250 then determines if the engine speed is less than the minimum engine speed Rmin as represented in a decisional block S14. If the engine speed is less than the minimum engine speed Rmin, then the routine 250 releases control of any disabled cylinder. In this manner, the engine speed no longer decreases and the watercraft 20 is maintained in the planing state. The routine 250 continues to monitor engine speed as indicated by an operational block S16, which returns the routine 250 to the decisional block S11.

[00114] If the routine 250 determines that the engine speed is greater than the minimum engine speed Rmin, then the routine 250 determines if another predetermined amount of time B3 has passed as represented by a decisional block S17. In a preferred embodiment, this predetermined amount of time is also approximately 0.1 seconds. If the predetermined amount of time B3 has not passed, the routine 250 preferably loops back to the decisional block S14. If the predetermined amount of time B3 has passed, a second cylinder is disabled as indicated by an operational block S18.

[00115] After the second cylinder is disabled, the routine 250 preferably again determines if the engine speed is less than the minimum engine speed Rmin as indicated by a decisional block S19. If the engine speed is less than the minimum engine speed Rmin, then the disabled cylinders are enabled as indicated by an operational block S15. If the engine speed is still greater than the minimum engine speed Rmin, then the routine determines if another predetermined amount of time B4 has passed as represented by a decisional block S20. In the illustrated embodiment, the predetermined amount of time B4 is also 0.1 seconds. If the predetermined amount of time has not passed, the routine 250 loops back to the decisional block S19. If the predetermined amount of time has passed, the third cylinder is disabled. In the illustrated embodiment wherein the engine has three cylinders, this effectively shuts off the engine. Of course, the routine 250 can be modified to sequentially disable all the cylinders of an engine with more or less than three cylinders.

[00116] Of course, the foregoing description is that of preferred embodiments of the invention and various changes, modifications and combinations may be made without departing from the spirit and scope of the invention, as defined by the appended claims.