Patent Document

PRIORITY INFORMATION 
     This application is based on and claims priority to Japanese Patent Application No. 2000-236816, filed Aug. 4, 2000, the entire contents of which is hereby expressly incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present application generally relates to an engine control arrangement for controlling a watercraft, and more particularly relates to a method of controlling the operation and interaction of an engine and an overturn switch. 
     2. Description of the Related Art 
     Watercraft, including personal watercraft and jet boats, are often powered by at least one internal combustion engine having an output shaft arranged to drive one or more water propulsion devices. Occasionally, watercraft can overturn due to the sporting manner in which they can be ridden. Additionally, some watercraft operators purposely overturn the vehicles or submerge the vehicles during operation. 
     Watercraft use air ducts to supply air to a generally enclosed engine compartment. The air is drawn from within the engine compartment for combustion. Thus, when a watercraft overturns, there is a danger of water entering the engine compartment and entering into the engine itself through the induction system, which can cause extensive engine damage. 
     To reduce the likelihood of such engine damage, overturn switches have been used. The overturn switches generally detect watercraft movement that is consistent with a watercraft that is overturning. When such movement is detected, the overturn switch quickly outputs a signal that is used to shut-off the engine. By rapidly shutting of the engine, induction of water into the engine is much less likely during watercraft inversion. 
     Typical overturn switch designs generally are gravity-biased or centrifugal in nature. When the associated watercraft overturns, the switch&#39;s position relative to gravity may cause the switch to detect the overturn or the rapid movement of the switch may cause the switch to detect the overturn. Unfortunately, watercraft are designed for sporting operation and often are operated in manners that cause rapid directional changes. For instance, the watercraft operator may engage in such activities as jumping, rapid turning and operation over rough water. Such activities can cause the typical overturn switches to falsely indicate an overturn leading to an undesirable and unnecessary engine shut off. 
     Watercraft also generally employ lanyard switches. Lanyard switches generally comprise a wrist tether (i.e., a wristband that is tethered to a “key” or other member that cooperates with a switch). When an operator of the watercraft falls from the watercraft, the wrist tether activates the lanyard switch and the engine is stopped. In effect, the lanyard switch generally operates as a kill switch that stops engine operation when the operator falls from the watercraft. 
     Over time it also is possible for the overturn switch  12  to experience certain failures due to normal aging and use of the watercraft  10 . Generally speaking, the overturn switch  12  may experience two classes of failures: (1) the overturn switch itself or the wiring may become short-circuited, or (2) the connection to the overturn switch may become disconnected. 
     SUMMARY OF THE INVENTION 
     If an operator falls from a vehicle during operation of the vehicle in a planing speed range, the lanyard switch almost always will kill engine operation. Additionally, it has been discovered that most false positives from the watercraft overturn switches are encountered during operation at or above a watercraft planing speed (or an engine speed associated with planing, such as about 6000 rpm). The false positives can be irritating to the operator and can adversely affect water vehicle performance. 
     Thus, a method of reducing false overturn signals is desired. In addition, due to the relatively important role the overturn switch plays, a technique of monitoring the operability of the switch is desired. 
     Accordingly, an engine control arrangement is desired to properly control the interaction of an overturn switch and an engine in order to prevent unnecessary engine shut off In addition, the engine control arrangement preferably can be configured to warn the watercraft operator of a disconnected, shorted, or faulty overturn switch. 
     Thus, one aspect of the present invention involves a method of controlling engine operation in a watercraft. The method comprising sensing a engine speed, determining if said engine speed is above a preset engine speed associated with a watercraft planing mode, sensing an overturn signal from an overturn sensor, determining whether said overturn signal persists for longer than a predetermined period of time and stopping the engine when said overturn signal persists for longer than a predetermined period of time. 
     Another aspect of the present invention involves a personal watercraft comprising a hull. A substantially enclosed compartment is by the hull. An engine is disposed within the compartment and an overturn switch mounted within the compartment. The overturn switch communicates with an ECU through a switch circuit. The overturn switch has a first output, a second output and a third output, with the second output indicating a switch circuit malfunction to the ECU. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention are described in detail below with reference to the accompanying drawings. The drawings comprise 6 figures. 
     FIG. 1 is a simplified and partially broken out side view of a personal watercraft. Various internal components positioned within the watercraft are illustrated in phantom and hidden lines. 
     FIG. 2 is a simplified schematic illustration of an exemplary overturn switch. 
     FIG. 3 is a block diagram showing various inputs and outputs of an ECU (Electronic Control Unit) that can be used in accordance with certain features, aspects, and advantages of the present invention. 
     FIG. 4 is a flowchart showing an exemplary control routine arranged and configured in accordance with certain features, aspects, and advantages of the present invention. 
     FIG. 5 is an exemplary schematic circuit diagram, including the ECU and the overturn switch, which are arranged and configured in accordance with certain features, aspects, and advantages of the present invention. 
     FIG. 6 is a flowchart showing another control routine arranged and configured in accordance with certain features, aspects and advantages of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1 to  6 , an overall configuration of a personal watercraft  10 , an overturn switch  12 , and various control routines will be described. The watercraft  10  preferably employs an ECU (Electronic Control Unit)  13 . The ECU  13 , the overturn switch  12 , and the disclosed control routines have particular utility for use within the personal watercraft  10 , and thus, are described in the context of personal watercraft. The ECU  13 , the overturn switch  12 , and the control routines, however, also can be used in conjunction with other types of watercraft, such as, for example, small jet boats, and other vehicles that operate on a body of water. 
     With reference to FIG. 1, the illustrated watercraft  10  includes a hull  14  that is defined by a lower portion  16  and a top portion or deck  18 . These portions of the hull  14  are preferably formed from a suitable material, such as, for example, a molded fiberglass reinforced resin. A bond flange  20  preferably connects the lower portion  16  to the deck  18 . Of course, any other suitable means may be used to interconnect the lower portion  16  and the deck  18 . Alternatively, the lower portion  16  and the deck  18  can be integrally formed. 
     As viewed in the direction from the bow to the stem, the deck  18  includes a bow portion  22 , a control mast  24 , and a rider&#39;s area  26 . The bow portion  22  preferably includes a hatch cover (not shown). The hatch cover preferably is pivotally attached to the deck  18  such that it is capable of being selectively locked in a substantially closed watertight position. A storage bin (not shown) preferably is positioned beneath the hatch cover. 
     The control mast  24  supports a handlebar assembly  28 . The handlebar assembly  28  controls the steering of the watercraft  10  in a conventional manner. The handlebar assembly  28  preferably carries a variety of controls for the watercraft  10 , such as, for example, a throttle control (not shown), a start switch (not shown), and a lanyard switch (not shown). Additionally, a gauge assembly (not shown) preferably is mounted to the upper deck section  18  forward of the control mast  24 . The gauge assembly can include a variety of gauges, such as, for example, a fuel gauge, a speedometer, an oil pressure gauge, a tachometer, and a battery voltage gauge. In particularly preferred arrangements, a warning lamp or other suitable alerting device can be disposed proximate or within the gauge assembly. 
     The rider area  26  lies rearward of the control mast  24  and includes a seat assembly  30 . The illustrated seat assembly  30  includes at least one seat cushion  32  that is supported by a raised pedestal  34 . The raised pedestal  34  forms a portion of the upper deck  18  and has an elongated shape that extends longitudinally substantially along the center of the watercraft  10 . The seat cushion  32  can be removably attached to a top surface of the raised pedestal  34  by one or more latching mechanisms (not shown) and, in the illustrated arrangement, covers the entire upper end of the pedestal  34  for rider and passenger comfort. 
     An engine access opening  36  preferably is defined in the upper surface of the illustrated pedestal  34 . The access opening  36  opens into an engine compartment  38  formed within the hull  14 . The seat cushion  32  can be disposed on a support plate that normally covers and substantially seals the access opening  36  to reduce the likelihood that water will enter the engine compartment  38 . When the seat cushion  32  and the associated support plate are removed, the engine compartment  38  is accessible through the access opening  36 . 
     The interior of the hull  14  includes one or more bulkheads  40  that can be used to reinforce the hull  14  internally and that also can serve to define, in part, the engine compartment  38  and a propulsion compartment  42 . The propulsion compartment  42  is arranged generally rearward from the engine compartment  38 . An engine  43  is mounted within the engine compartment  38  in any suitable manner preferably at a central transverse position of the watercraft  10 . A fuel tank  44  preferably is arranged in front of the engine  43  and is suitably secured to the hull  14  of the watercraft  10 . A fuel filler tube (not shown) preferably extends between the fuel tank  44  and the upper deck  18 . 
     A forward air duct  46  extends through the upper deck portion  18 . The forward air duct  46  allows atmospheric air to enter and exit the engine compartment  38 . Similarly, a rear air duct  48  extends through an upper surface of the seat pedestal  34 , preferably beneath the seat cushion  32 , thus also allowing atmospheric air to enter and exit the engine compartment  38 . Air may pass through the air ducts  46 ,  48  in both directions (i.e., into and out of the engine compartment  38 ). Except for the air ducts  46 ,  48 , the engine compartment  38  is substantially sealed so as to enclose the engine  43  of the watercraft  10  from the body of water in which the watercraft  10  is operated. 
     Toward a transom  50  of the watercraft  10 , the inclined sections of the lower hull section  16  extend outwardly from a recessed channel or tunnel  52 . The tunnel  52  is recessed within the lower hull section  16  in a direction that extends upward toward the upper deck section  18 . An intake duct  56 , defined by the hull tunnel  52 , begins at an inlet  58  and extends to a jet pump unit  54  which propels the watercraft  10 . 
     The jet pump unit  54  comprises an impeller housing  60 . A steering nozzle  62  is supported at the downstream end of a discharge nozzle  64  of the impeller housing  60  by a pair of vertically extending pivot pins (not shown). In an exemplary embodiment, the steering nozzle  62  has an integral lever on one side that is coupled to the handlebar assembly  28  through, for example, a bowden-wire actuator, as known in the art. In this manner, the operator of the watercraft  10  can move the steering nozzle  62  to effect directional changes of the watercraft  10 . 
     An impeller shaft  66  supports an impeller (not shown) within the impeller housing  60 . The aft end of the impeller shaft  66  is suitably supported and journaled within a compression chamber of the impeller housing  60  in a known manner. The impeller shaft  66  extends in a forward direction through the bulkhead  40 . A protective casing preferably surrounds a portion of the impeller shaft  66 . The forward end of the impeller shaft is connected to a crankshaft  68  of the engine  43  via a toothed coupling  70  in the illustrated arrangement. 
     With continued reference to FIG. 1, an engine air intake system is illustrated. A portion of the air entering the watercraft  10  through the air ducts  46 ,  48  enters the engine  43  through an intake silencer  72 , which is positioned generally in front of the illustrated engine  43 . The air travels from the silencer  52  through an intake duct  74  and into an intake chamber  76 . The air enters the engine  43  from the intake chamber  76  directly through various intake pipes  78  which extend upward from the intake chamber  76  and inward toward the engine  43 . 
     With reference to FIG. 1, an exhaust system is illustrated. The exhaust gases leaving the engine  43  travel into an initial exhaust pipe  80 , through a water trap  82 , through a secondary exhaust pipe  84  and exit the watercraft proximate the jet pump unit  54 . The engine  43 , which drives the jet pump unit  54 , can be a four-stroke in-line straight four cylinder engine. However, it should be appreciated that several features and advantages of the present invention can be used with an engine with a different cylinder configuration (e.g., v-type, w-type or opposed), a different number of cylinders (e.g., six) and/or a different principle of operation (e.g., two-cycle, rotary, or diesel principles). 
     The watercraft  10  preferably includes an emergency stop system  86  that determines when the watercraft  10  is overturned and monitors the overturn switch  12  to inform the rider if the overturn switch  12  is faulty. The emergency stop system  86  in the illustrated arrangement includes the overturn switch  12  (see FIG. 2) and the ECU  13  (see also FIG.  1 ). The emergency stop system  86  is illustrated schematically in FIG. 3 where the overturn switch  12 , an engine speed sensor  87 , and a lanyard engine stop switch  88  are inputs to the ECU  13 . The output signal from the ECU  13  is directed to the spark plug  96  and/or fuel injector system  94 . Preferably, the ECU  13  can cease engine operation by interrupting either ignition or fuel injection (e.g., if an exhaust catalyst is employed, fuel injection preferably is stopped) under appropriate conditions, which will be understood from the following discussion. 
     FIG. 2 illustrates an arrangement of the overturn switch  12 . It should be noted that the overturn switch could be mounted in any of a number of positions in and on the watercraft. The overturn switch  12  can include a pendulum  89  that is configured to pivot about an axis  90 . When the watercraft  10  is overturned, the pendulum  89  pivots, as indicated by the arrow D, and rests against the right or left stopper  92   a ,  92   b . When the pendulum  89  contacts one of the stoppers  92   a ,  92   b , the overturn switch  12  sends a signal to the ECU  13 . While one particular switch is illustrated in FIG. 2, any suitable overturn switch can be used. 
     With reference to FIG. 4, a control arrangement is shown that is arranged and configured in accordance with certain features, aspects, and advantages of the present invention. The routine basically evaluates whether a false overturn signal is likely and provides an appropriate sensing technique to substantially reduce the likelihood of false overturn signals. 
     The illustrated control routine begins and moves to a first decision block P 1  in which the engine speed is compared to a predetermined engine planing speed “A” (e.g., A can be about 6000 RPM in some applications). Preferably, the predetermined engine planing speed is an engine speed that generally corresponds to a watercraft speed that places the watercraft  10  in the planing mode. Such a speed generally identifies that the watercraft is being operated at a water speed that greatly increases the likelihood of a false positive overturn signal. Additionally, operation at or above that speed generally results in operation of a lanyard activated kill switch when the watercraft overturns. 
     If the watercraft  10  is found to be in a planing mode, then the watercraft  10  is operating in a vehicle speed range in which the overturn switch  12  may be closed temporarily due to jumping or rough waters, for instance. Therefore if the engine speed is determined to be greater than “A”, the routine returns to start and repeats. If the engine speed is less than “A”, the routine proceeds to a decision block P 2  where it determines if the overturn switch  12  is closed. 
     In the decision block P 2 , if the overturn switch  12  is determined to be closed, then the routine proceeds to a decision block P 3  where the routine checks whether a preset period of time, which can be determined empirically, has passed. Preferably, the time period is long enough to distinguish a false positive signal caused by jumping or the like and the time period is short enough to greatly reduce the likelihood of substantial water ingestion by the engine in the event of an actual overturn. In some applications, the time period can be about 0.5 second. If the predetermined period of time has passed, then the watercraft  10  most likely has overturned and the routine would move to process block P 4 . In the process block P 4 , the engine  43  is shut off and the routine then repeats. 
     As illustrated, if, in the decision block P 2 , the overturn switch  12  is open, then the routine repeats. In the decision block P 3 , if a predetermined amount of time has not elapsed, then the routine repeats without stopping the engine  43 . 
     In short, when the ECU  13  receives a signal from the overturn switch  12  while the watercraft is operating in a nonplaning mode, a delay loop is employed for a predetermined amount of time. If the overturn switch  12  is still sending a signal to the ECU  13  after the predetermined amount of time, the emergency shut off system  86  determines that the watercraft  10  has overturned. If the overturn switch  12  has stopped sending a signal after the predetermined amount of time, the emergency shut off system  86  determines that the watercraft has not overturned. In such a situation, the ECU  13  continues to look for a signal from the overturn switch  12  while normal engine operation continues. If the emergency shut off system  86  determines that the watercraft  10  is overturned, the ECU  13  stops the engine  43  by stopping the supply of electricity to the ignition system or by stopping the fuel supply through the fuel injectors. 
     An advantage of this arrangement is that the emergency shut off system  86  does not determine that the watercraft  10  is overturned if the watercraft  10  is merely turning abruptly or rocking back and forth quickly. In such situations, the pendulum  88  contacts the stoppers  92   a ,  92   b  for period of time that is less than the predetermined time. Unless the pendulum  88  rests on one of the stoppers  92   a ,  92   b  for the predetermined period of time (e.g., about 0.5 second), no overturn is detected and engine operation is uninterrupted. Additionally, when the vehicle is being operated at planning speeds, the lanyard switch can be used to shut down the engine during a vehicle overturn such that the output from the overturn switch can be ignored. This technique greatly reduces the likelihood of false positive signals from the watercraft during operation. 
     In order to provide a system for better determining if the watercraft  10  is capsized using the overturn switch  12 , the system desirably is capable of checking the operability of the overturn switch  12 . With reference to FIGS. 5 and 6, a schematic of a control circuit and a control routine are shown. The ECU  13  preferably controls various outputs; (e.g., fuel injectors  94 , spark plugs  96 , and the alarm  98 ), in order to turn off the engine  43  in the case of an overturn, or to communicate with the driver that the overturn switch  12  is faulty. 
     With reference to FIG. 5, power is provided from a battery  100  to the ECU  13 , the fuel injectors  94 , spark plugs  96 , and the alarm  98  through a main relay  102 . A main relay circuit  104  controls shutting off the main relay operation during capsizing. In the illustrated arrangement, a signal from the ECU  13  is sent when the predetermined time needed to determine a watercraft overturn has elapsed, as discussed above. A starter relay  106  switches on as soon as the starter switch  108  is closed and keeps the main relay  102  closed (i.e., on) after the starter switch  108  is opened and the starter (not shown) stops operating (i.e., the engine operates under its own power rather than under the starter&#39;s power). 
     With reference now to FIG. 6, an overturn switch failure control arrangement that is arranged and configured in accordance with certain features, aspects, and advantages of the present invention is illustrated. The control routine begins and moves to a first decision block P 10  in which operability of the overturn switch  12  at engine start is checked. 
     In a presently preferred arrangement, the operability can be monitored by detecting the voltages of the overturn switch  12 . In one advantageous arrangement, the voltages of the overturn switch  12  are prearranged to be about 0 volts when the overturn switch  12  is closed (e.g., when the watercraft is capsized) and about 5 volts (or about 12 volts in some applications) when the overturn switch is open. When the wires are disconnected from the overturn switch  12 , the voltage can default to about 2.5 volts (or about 6 volts in some applications). Any suitable wiring arrangement can be used to create these or similar voltage levels under the above-described conditions. Thus, these various voltage levels can be used to determine a failure of the overturn switch  12 . It should be noted that other voltage levels also can be used, however, for reasons that are apparent, the use of a zero voltage, a high level voltage, and a mid level voltage have been selected. 
     If there is a failure of the overturn switch  12  at engine start, then the control routine moves the decision block P 20  where the alarm buzzer/warning light  98  is switched on. The alarm buzzer/warning light can be disposed proximate the control mast  24 . When the alarm  98  is switched on, a software alarm flag can be set in the ECU  13 . The flag can be used by the software to indicate an on-going error in the system. Thus, in the illustrated arrangement, the alarm  98  remains on until the switch has been repaired and the alarm flag in the ECU  13  is reset (e.g., by a repair technician). Other suitable techniques of indicating a failure also can be used. 
     If there is no failure at engine start (i.e., at decision block P 10 ), the control routine proceeds to decision block P 30  where operability is checked during engine operation. If no failure occurs while the engine  43  is running, then the control routine simply continues to repeat. 
     If a failure does occur while the engine  43  is running, the control routine proceeds to the operation block P 40  and turns on the alarm  98  (where again an alarm flag can be set in the ECU  13 ). 
     The control routine then proceeds to the decision block P 50  where the engine speed is compared to a predetermined engine planing speed “A” (e.g., A can be about 6000 RPM in some applications). Preferably, the predetermined engine planing speed is an engine speed that generally corresponds to a watercraft speed that places the watercraft  10  in the planing mode. If the watercraft  10  is found to be in a planing mode then operability of the overturn switch is considered less important for the reasons discussed above. The engine  43  preferably is not shut off if the watercraft  10  is above the planing speed even if the overturn switch  12  is closed or faulty. Therefore, if the engine speed is determined to be greater than “A”, the routine returns to start and repeats. 
     It should be noted that a throttle position sensor can be used, in some arrangements, to act as a proxy for engine speed sensing. For instance, a throttle position of 30 degrees may be determined to be an approximate throttle position at which the watercraft can reach planing speed. In such cases, the approximate throttle position can be checked rather than engine speed, if desired. Furthermore, the engine speed actually serves as a proxy for watercraft speed or watercraft operational mode (i.e., planing mode). Therefore, in some arrangements, a watercraft speed sensor, planing condition sensor, or any other suitable sensor arrangement for determining a planing speed or watercraft operational mode can be used. 
     If the engine speed is less than “A”, (e.g., the watercraft is decelerated), the routine proceeds to an operation block P 60  where the engine  43  is stopped. The control routine then proceeds to the operation block P 70  where power to the entire watercraft  10  is shut down after a predetermined time has passed. The control routine then returns to start and repeats upon the next starting of the engine. Upon the next starting of the engine, if the malfunction of the overturn switch continues to be detected, the routine simply activates the buzzer and allows the watercraft to operate (i.e., the engine is not shut down). In one preferred arrangement, at least one cylinder is disabled such that the watercraft speed is limited and the watercraft can return to port under a “limp-home” mode. 
     It is to be noted that the control systems described above may be in the form of a hard-wired feedback control circuit in some configurations. Alternatively, the control systems may be constructed of a dedicated processor and memory for storing a computer program configured to perform the steps described above in the context of the flowcharts. Additionally, the control systems may be constructed of a general purpose computer having a general purpose processor and memory for storing the computer program for performing the routines. Preferably, however, the control systems are incorporated into the ECU  13 , in any of the above-mentioned forms. 
     Although the present invention has been described in terms of a certain preferred embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various steps within the routines may be combined, separated, or reordered. In some arrangements, both routines described above are integrated and implemented in a single application. In addition, some of the indicators sensed (e.g., engine speed and throttle position) to determine certain operating conditions (e.g., watercraft planing speed) can be replaced by other indicators of the same or similar operating conditions. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.

Technology Category: 2