Patent Publication Number: US-6905378-B2

Title: Engine control unit

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to Japanese patent application No. 2003-118353 filed on Apr. 23, 2003. 
   FIELD OF THE INVENTION 
   The present invention relates to an engine control unit of a jet propulsion boat that jets water that is pressurized and accelerated by a jet pump therein. 
   BACKGROUND OF THE INVENTION 
   In a boat propelled by jetting water pressurized and accelerated by a water jet pump, as thrust is decreased to a state in which a throttle valve is fully closed (an off-throttle state) during operation, the cornering performance is deteriorated. For technique for solving this problem, technique for controlling the speed of an engine for driving the water jet pump using handlebar off-steering information as a trigger heretofore exists. 
   For example, as described in Japanese Patent No. 2001-329881 and Japanese Patent No. 2002-87390, the cornering performance can be improved by increasing engine speed based upon steering angle and boat speed. 
   However, in the conventional examples, as shown in  FIG. 8 , the target engine speed of an off-throttle steering system (OTS) may be unable to be achieved depending upon a throttle angle. For example, in an example shown in  FIG. 8 , in case a throttle angle is 5°, engine speed can be enhanced up to the target engine speed of OTS which is slightly higher than engine speed in idling. However, as engine speed cannot be enhanced up to the target engine speed of OTS in case a throttle angle is 3°, control over steering may be difficult. Therefore, it would be beneficial to measure steering. Such a device would preferably be reliable, light weight, and inexpensive. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention relates to an engine control unit for a boat propelled by jetting water pressurized and accelerated by a water jet pump. The engine control unit measures throttle and steering. If the throttle is low and the steering is sharp, the engine control unit opens the throttle valve so that the boat can more efficiently perform the desired turn. More specifically, if the throttle angle of the engine for driving the water jet pump is a predetermined value or less and a steering angle by the steering handlebar of the jet propulsion boat is a predetermined value or more, the throttle valve of the engine is operated in the opened direction and advance angle control can be made over the ignition timing of the engine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view a part of which is cut out showing a jet propulsion boat mounting an engine output controller equivalent to this embodiment. 
       FIG. 2  is a plan showing the same jet propulsion boat. 
       FIG. 3  is a schematic perspective view mainly showing an engine and a turbocharger. 
       FIG. 4  shows the configuration of OTS of the jet propulsion boat mounting the engine output controller equivalent to this embodiment. 
       FIG. 5  is a flowchart showing OTS control. 
       FIG. 6  is a timing chart showing OTS control. 
       FIG. 7  is a graph showing mainly showing the variation in time of a throttle angle and engine speed. 
       FIG. 8  is a graph showing the variation in time of a throttle angle and engine speed in a conventional system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, one embodiment of an engine control unit according to the invention will be described below.  FIG. 1  is a side view a part of which is cut out showing a personal water craft (PWC) mounting an engine output controller equivalent to this embodiment and  FIG. 2  is a plan showing the same boat. 
   As shown in these drawings (mainly FIG.  1 ), the personal water craft  10  is a saddle-type small-sized boat, a crew sits on a seat  12  on the body  11 , and the output of an engine  20  is adjusted by gripping and operating a steering handlebar  13  with a throttle lever and adjusting an opening of a throttle valve (not shown) of the engine  20 . 
   The body of the boat  11  has floating structure acquired by bonding a hull  14  and a deck  15  and forming space  16  inside. In the space  16 , the engine  20  is mounted above the hull  14  and a water jet pump  30  as propelling means driven by the engine  20  is provided to the rear of the hull  14 . 
   The water jet pump  30  is provided with an impeller  32  arranged in a duct  18  extended from an intake  17  open to the bottom to a deflector  38  via an exhaust nozzle  31  open to the rear end of the body, and a shaft (a drive shaft)  22  for driving the impeller  32  is coupled to the output shaft  21  of the engine  20  via a coupler  21   a.    
   Therefore, when the impeller  32  is rotated by the engine  20  via the coupler  21   a  and the shaft  22 , water taken in from the intake  17  is jetted from the exhaust nozzle  31  via the deflector  38  and hereby, the body  11  is propelled. 
   The number of revolutions of the engine  20 , that is, propelling force by the water jet pump  30  is operated by the turning operation of the throttle lever  13   a  (see  FIG. 2 ) of the steering handlebar  13 . The deflector  38  is linked with the steering handlebar  13  via operating wire not shown, is turned by the operation of the handlebar  13  and hereby, a course of the body  11  can be changed. 
     FIG. 3  is a schematic perspective view mainly showing the engine  20 . 
   The engine  20  is a DOHC-type in-line four-cylinder dry sump-type four-cycle engine and its crankshaft (see the output shaft  21  shown in  FIG. 1 ) is arranged along the longitudinal direction of the body  11 . 
   As shown in  FIGS. 1  to  3 , a surge tank  41  and an inter-cooler  22  are connected and arranged on the left side of the engine  20  in the traveling direction F of the body  11  and an exhaust manifold  23  is arranged on the right side of the engine  20 . 
   A turbocharger  24  for feeding compressed intake air to the engine  20  is arranged at the back of the engine  20  and an air cleaner case  40  for taking new air in the turbocharger  24  via a pipe  25  is arranged in front of the engine  20 . 
   An exhaust outlet of the exhaust manifold  23  (see  FIG. 2 ) is connected to a turbine of the turbocharger  24 . Besides, the inter-cooler  22  is connected to a compressor of the turbocharger  24  via a pipe  22   a  and the surge tank  41  is connected to the inter-cooler  22  via a pipe  21   b . Therefore, after new air from the air cleaner case  40  is supplied to the turbocharger  24  via the pipe  25 , is compressed in its compressor and is supplied and cooled to/in the inter-cooler  22  via the pipe  22   a , the new air is supplied to the engine  20  via the surge tank  41 . 
   Exhaust gas which fulfills the role of turning the turbine of the turbocharger  24  is exhausted into a water muffler  60  via a first exhaust pipe  51 , a back flow preventing chamber  52  for preventing the back flow of water in a turnover (the penetration of water into the turbocharger  24  and others) and a second exhaust pipe  53 , and is further exhausted into a stream made by the water jet pump  30  from the water muffler  60  via an exhaust gas/waste water pipe  54 . 
   An engine speed sensor that detects the engine speed is provided to the engine  20 . Besides, a boost pressure sensor that detects boost pressure is provided to the turbocharger  24 . The engine speed sensor and the boost pressure sensor are connected to a controller  100  (an engine output controller) mounted in the jet propulsion boat  10 . Measured values sensed by these sensors are regularly output to the controller  100 . 
     FIG. 4  is a block diagram showing an off-throttle steering system (OTS) of the jet propulsion boat  10 . 
   A full steering switch  70  is provided to the steering handlebar  13  as a steering angle sensor and outputs a measured value of a steering angle or the on/off of the full steering switch to the controller  100 . A throttle body  80  for opening/closing a throttle valve  81  interlocked with the throttle lever  13   a  that supplies suitable air quantity to the engine  20  to control the output is provided to the engine  20 . A throttle angle sensor  102  for detecting an angle of the throttle valve  81  is provided to the throttle body  80  and outputs a measured value of the throttle angle to the controller  100 . 
   The throttle valve  81  is connected to a diaphragm actuator  82  and is opened/closed by the drive of the diaphragm actuator  82 . The diaphragm actuator  82  is connected to the surge tank  84  via a solenoid (an electromagnetic valve)  83  and is driven according to the on/off of the solenoid  83 . The surge tank  84  is connected to an air intake duct via a one-way valve  85  in the rear of the throttle valve  81 . 
   An OTS indicator  86  showing an on/off state of OTS is provided in a meter in front of the steering handlebar  13 . 
   The controller  100  is an engine control unit (ECU) that controls the engine  20  and others and is connected to a fuel injection system and an igniter provided to the engine  20 . 
   The fuel injection system injects fuel under the control of the controller  100 . The igniter similarly ignites fuel under the control of the controller  100 . 
   Next, referring to the drawings, the operation of the engine control unit (the controller  100 ) equivalent to this embodiment will be described.  FIG. 5  is a flowchart showing a process of OTS control processing by the engine control unit equivalent to this embodiment. 
   First, the controller  100  receives each measured value of engine speed NE, a throttle angle TH, and a steering angle respectively input from the engine speed sensor, the throttle angle sensor  102  and the full steering switch  70  and compares them with an OTS action condition (a step S 1  in FIG.  5 ). 
   That is, the controller  100  determines whether the input engine speed NE is equal to or exceeds a set value or not and whether the input throttle angle TH is equal to or exceeds a set value or not, and in case these conditions are met, a flag of an OTS standby is turned on for fixed time (A shown in FIG.  6 ). In the meantime, in case duration time does not meet set time or in case these conditions are not met, a flag of the OTS standby is not turned on. Even if a boat speed signal from a boat speed meter is turned on (for example, boat speed &gt;30 kmph), a flag of the OTS standby may be also turned on. 
   Next, the controller  100  determines whether a flag for activating OTS is turned on or not (a step S 2 ). In case the flag for activating OTS is turned on (1 in the step S 2 ), the controller  100  determines whether the throttle angle TH is a preset throttle angle TH or less or not (a step S 3 ). In the meantime, in case the flag for activating OTS is not on (0 in the step S 2 ), the controller  100  proceeds to a normal control mode (a step S 6 ). 
   In case the throttle angle TH is the preset throttle angle TH or less (Yes in the step S 3 , B shown in FIG.  6 ), the controller  100  further determines whether the steering handlebar  13  is in a state of full steering or not, which is input from the full steering switch  70  (a step S 4 ). 
   In the meantime, in case the throttle angle TH exceeds the preset throttle angle TH (No in the step S 3 ), the controller  100  proceeds to the normal control mode (the step S 6 ). At this time, the set throttle angle includes a fully closed state or the vicinity of the fully closed state. 
   In case the full steering state of the steering handlebar  13  is sensed (Yes in the step S 4 , C shown in FIG.  6 ), the controller  100  sets a timer, controls the engine for fixed time (avoiding operation time) using the elapse of set time as a trigger and enhances thrust (a step S 5 , D and E shown in FIG.  6 ). That is, the controller  100  operates the throttle valve  81  of the engine  20  in an opened direction and has advance angle control over the ignition timing of the engine. 
   Concretely, the controller  100  outputs a turn-on signal to the solenoid  83 , drives the diaphragm actuator  82  and operates the throttle valve  81  in the opened direction. Besides, the controller  100  corrects so that the ignition timing of the igniter is earlier than ignition timing calculated based upon engine speed for fixed time (avoiding operation time) and outputs an ignition signal to the igniter. At this time, the controller  100  controls the volume of fuel injected by the fuel injection system based upon the corrected result of the corresponding ignition timing. 
   The fuel injection system injects fuel according to the control of the controller  100  and the igniter ignites fuel earlier than the top dead center of a piston according to the ignition signal output by the controller  100 . 
   Ignition timing is made earlier by such advance angle control of ignition timing as shown in  FIG. 7 , compared with a case that no control is made (when a throttle angle is 5°) and in case a throttle angle is smaller (when a throttle angle is 3°), OTS target engine speed slightly higher than engine speed in idling can be also held. 
   As described above, according to the invention, as the throttle valve of the engine is operated in the opened direction and advance angle control is made over the ignition timing of the engine in case a throttle angle of the engine for driving the water jet pump is a predetermined value or less and a steering angle by the steering handlebar of the jet propulsion boat is a predetermined value or more, effect that steering control can be easily made even if the throttle valve is closed can be acquired. 
   The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.