Patent Publication Number: US-9902479-B1

Title: Boat shift control device and boat shift control method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a boat shift control device and boat shift control method, which are used to control shifting of an internal combustion engine in a situation where a plurality of internal combustion engines are mounted on a boat and only a specific engine, other than the former engine, thereamong is being used to operate the boat. 
     2. Description of the Related Art 
     Known technologies of engine shift control during a sudden shifting operation involve performing shift connection once revolutions have dropped sufficiently during propeller driving, to reduce the load that is exerted on the engine and prevent problems such as engine stalls. 
     In such technologies there is used for instance a conjectured rotational speed resulting from simulating the speed of the hull, for the purpose of prohibiting shift-in to reverse within a certain boat speed range and thus reducing engine loading and preventing engine stalling. Proposed such technologies include the one described in Japanese Patent No. 3833616. 
     SUMMARY OF INVENTION 
     Conventional technologies have however the following problems. 
     The conventional shift-in prevention control scheme described above involves setting a shift-in prohibition on the basis of a parameter obtained by simulating boat speed, and performing control of permitting shift-in after the boat speed has dropped to a predetermined value. 
     In the case of boats, however, a situation has become common in recent years where not just one engine but a plurality of engines is set in one boat. 
     For instance, there is conceivably provided a plurality of engines, i.e. two or three engines, the boat being operated with a specific engine alone. In such a case, once the boat speed has become equal to or higher than a given speed, a user may then operate the shifts and throttles in order to operate the remaining engines. 
     The load acting on the engines increases when the shift-in operation is carried out within a certain boat speed range. Moreover, the load on the gear boxes may in increase, which in the worst case may lead to gear breakdown that renders any subsequent operation impossible. 
     In view of such usage environment of a boat, it is an object of the present invention to achieve a boat shift control device and a boat shift control method that allow reliably protecting engines and gear boxes even in a case where there is set a plurality of engines and the boat is operated using a specific engine alone. 
     A boat shift control device according to the present invention is a boat shift control device that controls shift-in and shift-out of a plurality of engines mounted on a boat, the boat shift control device having: a rotational speed detector that detects the rotational speed of each of the plurality of engines; an LP sensor that detects any one shift state from among forward, reverse and neutral, on the basis of an operation state of respective throttle levers corresponding to the plurality of engines; and a controller that controls the plurality of engines; wherein the controller detects a simulated boat speed on the basis of the respective rotational speeds of the plurality of engines; and in a case where the simulated boat speed is higher than a pre-set first determination value when from a state in which the boat is operated by a part of the plurality of engines an attempt is made to operate the remaining engine being in a neutral shift state, the controller sets a shift-in prohibition flag of a corresponding engine, and prohibits shift-in control of the remaining engine. 
     A boat shift control method according to the present invention is executed by a controller that controls shift-in and shift-out of a plurality of engines mounted on a boat, the method having: a first step of calculating a simulated boat speed of the boat on the basis of respective rotational speeds of the plurality of engines as detected by a rotational speed detector; a second step of detecting, on the basis of a detection result by an LP sensor that detects any one shift state from among forward, reverse and neutral on the basis of an operation state of respective throttle levers corresponding to the plurality of engines, a shift-in operation state where, from a state in which the boat is operated by a part of the plurality of engines, an attempt is made to operate the remaining engine being in a neutral shift state; and a third step of setting a shift-in prohibition flag of a corresponding engine, and prohibiting shift-in control of the remaining engine if, upon detection of the shift-in operation state according to the second step, the simulated boat speed calculated in the first step is higher than a pre-set first determination value. 
     According to the present invention, during operation of only a specific engine among a plurality of installed engines, shift-in is prohibited when detecting that the boat has a certain speed at a timing at which a remaining engine is to be operated. As a result it becomes possible to achieve a boat shift control device and a boat shift control method that allow reliably protecting engines and gear boxes also in a case where there is set a plurality of engines and the boat is operated using a specific engine alone. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall configuration diagram of a boat shift control device according to Embodiment 1 of the present invention, in an instance where the boat shift control device is utilized in a marine internal combustion engine; 
         FIG. 2  is a flowchart illustrating a shift control process that is executed, as a main control process, by an ECU  10  in Embodiment 1 of the present invention; 
         FIG. 3  is a flowchart relating to a simulated boat speed detection process in Embodiment 1 of the present invention; 
         FIG. 4A  is a flowchart of a turning mode detection process of Embodiment 1 of the present invention; 
         FIG. 4B  is a flowchart of a turning mode detection process of Embodiment 1 of the present invention; 
         FIG. 4C  is a flowchart of a turning mode detection process of Embodiment 1 of the present invention; 
         FIG. 5  is a flowchart of a shift-in prohibition determination process in Embodiment 1 of the present invention; 
         FIG. 6  is a flowchart of a shift command process in Embodiment 1 of the present invention; and 
         FIG. 7  is a flowchart of a shift-in prohibition buzzer process in Embodiment 1 of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the boat shift control device and the boat shift control method of the present invention will be explained next with reference to accompanying drawings. 
     Embodiment 1 
       FIG. 1  is an overall configuration diagram of a boat shift control device according to Embodiment 1 of the present invention, in an instance where the boat shift control device is utilized in a marine internal combustion engine. Two outboard motors  100 ,  200  having each an internal combustion engine (hereafter, “engine”), a propeller and so forth integrated thereinto, are provided with respective electronic control units (ECUs)  130 ,  230  as control means. The outboard motors  100 ,  200  are mounted on the stern of a boat  11 .  FIG. 1  depicts a two-motor configuration that will be explained in detail below as a specific example. 
     Throttle levers  101 ,  201  are disposed in boat maneuver remote controls  110 ,  210 . The throttle levers  101 ,  201  are provided with LP sensors  102 ,  202  (lever position sensors) that detect a lever position. 
     Lever position signals detected by the LP sensors  102 ,  202  are outputted to the ECU  10  that performs shift control, via signal lines a 1 , a 2 . On the basis of the received respective lever position signal, the ECU  10  detects a request amount of throttle valve (hereafter referred to as requested throttle opening degree) and a request amount of forward/neutral/reverse (hereafter referred to as requested shift position). 
     On the basis of the lever position and the engine state, the ECU  10  determines an amount of opening of the respective throttle valve from fully closed to fully open (hereafter referred to as target throttle opening degree) and a shift position (hereafter referred to as target shift position). 
     A buzzer  15  is connected to the ECU  10 . If the ECU  10  determines that an anomaly or the like has occurred, the ECU  10  outputs an audible alarm via the buzzer  15 . 
     The ECU  10  instructs command values of the target throttle opening degree (from full closed to full open) and the target shift position (F/N/R) to the ECUs  130 ,  230  in the two outboard motors  100 ,  200 , via signal lines b 1 , b 2 . 
     Having received the command values, the ECUs  130 ,  230  inside the outboard motors  100 ,  200  output an amount of opening (intake air amount) of the respective throttle valves via a link mechanism. The ECUs  130 ,  230  output a shift position (forward/neutral/reverse) via a shift link mechanism (not shown) and the gear mechanisms  135 ,  235 . 
     The ECUs  130 ,  230  transmit to the ECU  10  respective actual engine states including engine rotational speed, amount of throttle valve opening (actual throttle opening degree) and shift position (actual shift position). 
     The details of the shift control process executed by the ECU  10  will be explained next on the basis of the flowcharts illustrated in  FIG. 2  to  FIG. 7 . 
       FIG. 2  is a flowchart illustrating the shift control process that is executed, as a main control process, by the ECU  10  in Embodiment 1 of the present invention. The main control process is executed every 5 ms. 
     In step S 201 , firstly, the ECU  10  executes a simulated boat speed detection process. The details of the simulated boat speed detection process will be explained further on with reference to  FIG. 3 . 
     In step S 202  next, the ECU  10  executes a turning mode detection process. The details of the turning mode detection process will be explained further on with reference to  FIG. 4A  to  FIG. 4C . 
     In step S 203  next, the ECU  10  executes a shift-in prohibition determination process, and performs prohibition determination relating to shifting from N to F and from N to R. The details of the shift-in prohibition determination process will be explained further on with reference to  FIG. 5 . 
     In step S 204  next, the ECU  10  executes a shift command process, and instructs the shift position (F/N/R). The details of the shift command process will be explained further on with reference to  FIG. 6 . 
     In step S 205 , lastly, the ECU  10  executes a shift-in prohibition buzzer process, and outputs a warning via a warning buzzer. The details of the shift-in prohibition buzzer process will be explained further on with reference to  FIG. 7 . 
       FIG. 3  is a flowchart relating to the simulated boat speed detection process in Embodiment 1 of the present invention. In step S 301 , firstly, the ECU  10  determines whether a detection period has elapsed or not. In the present Embodiment 1 an instance will be explained where the detection period is set to 100 ms. The detection period may however be set arbitrarily. 
     If the ECU  10  determines that the detection period has elapsed, the ECU  10  executes the series of processes from step S 302  onwards. If on the other hand the ECU  10  determines that the detection period has not elapsed, the ECU  10  terminates the series of processes. 
     If having proceeded to step S 302 , the ECU  10  compares the engine rotational speed of the outboard motor  100  (rotational speed  1 ) and the engine rotational speed of the outboard motor  200  (rotational speed  2 ). The ECU  10  detects the rotational speed  1  and the rotational speed  2  on the basis of rotational speed detectors not shown. 
     If the rotational speed  1  is equal to or greater than the rotational speed  2 , the ECU  10  executes step S 303 . If on the other hand the rotational speed  1  is lower than the rotational speed  2 , the ECU  10  executes step S 304 . 
     If having proceeded to step S 303 , the ECU  10  sets the rotational speed  1  in a calculation buffer, and thereafter executes step S 305 . 
     If having proceeded to step S 304 , the ECU  10  sets the rotational speed  2  in the calculation buffer, and thereafter executes step S 305 . 
     In step S 305 , lastly, the ECU  10  performs a filtering process of a previous simulated boat speed and the current engine rotational speed set in the buffer, and terminates the series of processes pertaining to simulated boat speed detection. Specifically, the ECU  10  executes a filtering process according to the expression below. The gain can be set between 0 and 1.
 
Simulated boat speed=previous value of simulated boat speed×(1−gain)+(value in buffer×gain)
 
       FIG. 4A  to  FIG. 4C  are flowcharts of a turning mode detection process of Embodiment 1 of the present invention. Through this process the ECU  10  determines the establishment and cancellation of a turning mode. In step S 401 , firstly, the ECU  10  determines whether the simulated boat speed is lower than a determination value SS 1  or not. If the simulated boat speed is lower than the determination value SS 1 , the ECU  10  executes step S 410 , while if the simulated boat speed is equal to or higher than the determination value SS 1 , the ECU  10  executes step S 420 . 
     In step S 410 , the ECU  10  determines whether a requested shift position  1  has been set to forward (F) or not through operation of the throttle lever  101  of the boat maneuver remote control  110  by the boat operator. If the requested shift position  1  is set to F, the ECU  10  executes step S 411 . If on the other hand the requested shift position  1  is not F, the ECU  10  executes step S 415 . 
     In step S 411 , the ECU  10  determines whether a requested shift position  2  has been set to reverse (R) or not through operation of the throttle lever  201  of the boat maneuver remote control  210  by the boat operator. If the requested shift position  2  is set to R, the ECU  10  executes step S 412 . If on the other hand the requested shift position  2  is not R, the ECU  10  executes step S 415 . 
     In step S 412 , the ECU  10  determines that a turning operation is in progress, sets the turning mode flag to 1, and executes step S 415 . 
     In step S 415 , the ECU  10  determines whether or not the requested shift position  1  is set to R. If the requested shift position  1  is set to R, the ECU  10  executes step S 416 . If on the other hand the requested shift position  1  is not R, the ECU  10  executes step S 420 . 
     In step S 416 , the ECU  10  determines whether or not the requested shift position  2  is set to F. If the requested shift position  2  is set to F, the ECU  10  executes step S 417 . If on the other hand the requested shift position  2  is not F, the ECU  10  executes step S 420 . 
     In step S 417 , the ECU  10  determines that a turning operation is in progress, sets the turning mode flag to 1, and executes step S 420 . 
     In step S 420 , the ECU  10  determines whether or not the requested shift position  1  is set to F. If the requested shift position  1  is set to F, the ECU  10  executes step S 421 . If on the other hand the requested shift position  1  is not F, the ECU  10  executes step S 429 . 
     In step S 421 , the ECU  10  determines whether or not a requested throttle opening degree  1  set through operation of the throttle lever  101  of the boat maneuver remote control  110  by the boat operator is lower than a determination value TH 1 . If the requested throttle opening degree  1  is lower than the determination value TH 1 , the ECU  10  executes step S 422 . If on the other hand the requested throttle opening degree  1  is equal to or higher than the determination value TH 1 , the ECU  10  executes step S 429 . 
     In step S 422 , the ECU  10  determines whether or not the requested shift position  2  is set to F. If the requested shift position  2  is set to F, the ECU  10  executes step S 423 . If on the other hand the requested shift position  2  is not F, the ECU  10  executes step S 429 . 
     In step S 423 , the ECU  10  determines whether or not a requested throttle opening degree  2  set through operation of the throttle lever  201  of the boat maneuver remote control  210  by the boat operator is lower than the determination value TH 1 . If the requested throttle opening degree  2  is lower than the determination value TH 1 , the ECU  10  executes step S 424 . If on the other hand the requested throttle opening degree  2  is equal to or higher than the determination value TH 1 , the ECU  10  executes step S 429 . 
     If having proceeded to step S 424 , the ECU  10  determines that the turning mode establishment condition is satisfied, allows a turning mode establishment timer to implement countdown, and thereafter executes step S 425 . 
     If having proceeded to step S 429 , on the other hand, the ECU  10  sets an initial value  1  in the turning mode establishment timer, and executes step S 425 . 
     In step S 425 , the ECU  10  determines whether or not a set time has elapsed in the turning mode establishment timer. If the set time has elapsed in the turning mode establishment timer, the ECU  10  executes step S 426 . If on the other hand the set time has not elapsed in the turning mode establishment timer, the ECU  10  executes step S 450 . 
     If having proceeded to step S 426 , the ECU  10  sets the turning mode flag to 1, and executes step S 450 . 
     With reference to  FIG. 4B , the ECU  10  determines next, in step S 450 , whether or not the requested shift position  1  is set to F. If the requested shift position  1  is set to F, the ECU  10  executes step S 451 . If on the other hand the requested shift position  1  is not F, the ECU  10  executes step S 453 . 
     In step S 451 , the ECU  10  determines whether or not an engine rotational speed  1  is higher than a determination value NE 1 . If the engine rotational speed  1  is higher than the determination value NE 1 , the ECU  10  executes step S 452 . If on the other hand the engine rotational speed  1  is equal to or lower than the determination value NE 1 , the ECU  10  executes step S 453 . 
     If having proceeded to step S 452 , the ECU  10  determines that a turning mode cancellation condition is satisfied, allows a turning mode cancellation timer  1  to implement countdown, and thereafter executes step S 455 . 
     If having proceeded on the other hand to step S 453 , the ECU  10  determines that the turning mode cancellation condition is not satisfied, sets an initial value  2  in the turning mode cancellation timer  1 , and thereafter executes step S 455 . 
     In step S 455 , the ECU  10  determines whether or not a set time has elapsed in the turning mode cancellation timer  1 . If the set time has elapsed in the turning mode cancellation timer  1 , the ECU  10  executes step S 456 . If on the other hand the set time has not elapsed in the turning mode cancellation timer  1 , the ECU  10  executes step S 460 . 
     If having proceeded to step S 456 , the ECU  10  determines that the turning mode cancellation condition is satisfied, clears the turning mode flag, and executes step S 460 . 
     In step S 460 , the ECU  10  determines whether or not the requested shift position  2  is set to F. If the requested shift position  2  is set to F, the ECU  10  executes step S 461 . If on the other hand the requested shift position  2  is not F, the ECU  10  executes step S 463 . 
     In step S 461 , the ECU  10  determines whether or not an engine rotational speed  2  is higher than the determination value NE 1 . If the engine rotational speed  2  is higher than the determination value NE 1 , the ECU  10  executes step S 462 . If on the other hand the engine rotational speed  2  is equal to or lower than the determination value NE 1 , the ECU  10  executes step S 463 . 
     If having proceeded to step S 462 , the ECU  10  determines that a turning mode cancellation condition is satisfied, allows a turning mode cancellation timer  2  to implement countdown, and thereafter executes step S 465 . 
     If having proceeded on the other hand to step S 463 , the ECU  10  determines that the turning mode cancellation condition is not satisfied, sets an initial value  2  in the turning mode cancellation timer  2 , and executes step S 465 . 
     In step S 465 , the ECU  10  determines whether or not a set time has elapsed in the turning mode cancellation timer  2 . If the set time has elapsed in the turning mode cancellation timer  2 , the ECU  10  executes step S 466 . If on the other hand the set time has not elapsed in the turning mode cancellation timer  2 , the ECU  10  executes step S 470 . 
     If having proceeded to step S 466 , the ECU  10  determines that the turning mode cancellation condition is satisfied, clears the turning mode flag, and executes step S 470 . 
     With reference to  FIG. 4C , the ECU  10  determines next, in step S 470 , whether or not the requested shift position  1  is set to F. If the requested shift position  1  is set to F, the ECU  10  executes step S 471 . If on the other hand the requested shift position  1  is not F, the ECU  10  executes step S 473 . 
     In step S 471 , the ECU  10  determines whether or not the requested shift position  2  is set to F. If the requested shift position  2  is set to F, the ECU  10  executes step S 472 . If on the other hand the requested shift position  2  is not F, the ECU  10  executes step S 473 . 
     If having proceeded to step S 472 , the ECU  10  determines that a turning mode cancellation condition is satisfied, allows a turning mode cancellation timer  3  to implement countdown, and thereafter executes step S 475 . 
     If having proceeded on the other hand to step S 473 , the ECU  10  determines that the turning mode cancellation condition is not satisfied, sets an initial value  3  in the turning mode cancellation timer  3 , and executes step S 475 . 
     In step S 475 , the ECU  10  determines whether or not a set time has elapsed in the turning mode cancellation timer  3 . If the set time has elapsed in the turning mode cancellation timer  3 , the ECU  10  executes step S 476 . If on the other hand the set time has not elapsed in the turning mode cancellation timer  3 , the ECU  10  terminates the series of processes relating to turning mode detection. 
     If having proceeded to step S 476 , the ECU  10  determines that the turning mode cancellation condition is satisfied, clears the turning mode flag, and terminates the series of processes relating to turning mode detection. 
       FIG. 5  is a flowchart of the shift-in prohibition determination process in Embodiment 1 of the present invention. In step S 501 , firstly, the ECU  10  determines whether the turning mode flag is reset or not. If the turning mode flag is reset, the ECU  10  executes step S 502 . If the turning mode flag is set, the ECU  10  executes step S 510 . 
     In step S 502 , the ECU  10  determines whether the simulated boat speed is higher than a determination value SS 2  or not. If the simulated boat speed is higher than the determination value SS 2 , the ECU  10  executes step S 505 . If on the other hand the simulated boat speed is equal to or lower than the determination value SS 2 , the ECU  10  executes step S 510 . 
     In step S 505 , the ECU  10  determines whether or not the requested shift position  2  is set to other than N. If the requested shift position  2  is set to F or R other than N, the ECU  10  executes step S 506 . If on the other hand the requested shift position  2  is N, the ECU  10  executes step S 507 . 
     In the case of two or more motors there are set all the requested shift positions other than those for self-maneuver remote control. 
     If having proceeded to step S 506 , the ECU  10  determines that there is a shift-in command in a high boat speed state, sets to 1 a shift-in prohibition flag  1 , and executes step S 507 . 
     In step S 507 , the ECU  10  determines whether or not the requested shift position  1  is set to other than N. If the requested shift position  1  is set to F or R other than N, the ECU  10  executes step S 508 . If on the other hand the requested shift position  1  is N, the ECU  10  executes step S 510 . 
     In the case of two or more motors there are set all the requested shift positions other than those for self-maneuver remote control. 
     If having proceeded to step S 508 , the ECU  10  determines that there is a shift-in command in a high boat speed state, sets to 1 a shift-in prohibition flag  2 , and executes step S 510 . 
     In step S 510 , the ECU  10  determines whether or not the requested throttle opening degree  1  is lower than a determination value TH 2 . If the requested throttle opening degree  1  is lower than the determination value TH 2 , the ECU  10  executes step S 511 . If on the other hand the requested throttle opening degree  1  is equal to or higher than the determination value TH 2 , the ECU  10  terminates the series of processes relating to shift-in prohibition determination. 
     In step S 511 , the ECU  10  determines whether or not the requested throttle opening degree  2  is lower than the determination value TH 2 . If the requested throttle opening degree  2  is lower than the determination value TH 2 , the ECU  10  executes step S 515 . If on the other hand the requested throttle opening degree  2  is equal to or higher than the determination value TH 2 , the ECU  10  terminates the series of processes relating to shift-in prohibition determination. 
     If having proceeded to step S 515 , all the requested throttle opening degrees  1  and  2  are lower than the determination value TH 2 , and accordingly the ECU  10  clears the shift-in prohibition flag  1  and executes step S 516 . 
     In step S 516 , the ECU  10  clears the shift-in prohibition flag  2  and terminates the series of processes relating to shift-in prohibition determination. 
       FIG. 6  is a flowchart of the shift command process in Embodiment 1 of the present invention. In step S 601 , the ECU  10  determines whether or not the shift-in prohibition flag  1  is 0. If the shift-in prohibition flag  1  is 0, the ECU  10  executes step S 602 . If on the other hand the shift-in prohibition flag  1  is set to 1, the ECU  10  executes step S 604 , in order to perform only an N process. 
     In step S 602 , the ECU  10  determines whether or not the requested shift position  1  is set to F. If the requested shift position  1  is F, the ECU  10  executes step S 605 . If on the other hand the requested shift position  1  is not F, the ECU  10  executes step S 603 . 
     In step S 603  the ECU  10  determines whether or not the requested shift position  1  is set to R. If the requested shift position  1  is R, the ECU  10  executes step S 606 . If on the other hand the requested shift position  1  is not R, the ECU  10  executes step S 604 . 
     In step S 604  the ECU  10  determines whether or not the requested shift position  1  is set to N. If the requested shift position  1  is N, the ECU  10  executes step S 607 . If on the other hand the requested shift position  1  is not N, the ECU  10  executes step S 610 . 
     If having proceeded to step S 605 , the ECU  10  sets the target shift position  1  to F, instructs the ECU  130  to thereby bring the actual shift to F, and thereafter executes step S 610 . 
     If having proceeded to step S 606 , the ECU  10  sets the target shift position  1  to R, instructs the ECU  130  to thereby bring the actual shift to R, and thereafter executes step S 610 . 
     If having proceeded to step S 607 , the ECU  10  sets the target shift position  1  to N, instructs the ECU  130  to thereby bring the actual shift to N, and thereafter executes step S 610 . 
     In step S 610 , the ECU  10  determines whether or not the shift-in prohibition flag  2  is 0. If the shift-in prohibition flag  2  is 0, the ECU  10  executes step S 612 . If on the other hand the shift-in prohibition flag  2  is set to 1, the ECU  10  executes step S 614 , in order to perform only an N process. 
     In step S 612 , the ECU  10  determines whether or not the requested shift position  2  is set to F. If the requested shift position  2  is F, the ECU  10  executes step S 615 . If on the other hand the requested shift position  2  is not F, the ECU  10  executes step S 613 . 
     In step S 613  the ECU  10  determines whether or not the requested shift position  2  is set to R. If the requested shift position  2  is R, the ECU  10  executes step S 616 . If on the other hand the requested shift position  2  is not R, the ECU  10  executes step S 614 . 
     In step S 614  the ECU  10  determines whether or not the requested shift position  2  is set to N. If the requested shift position  2  is N, the ECU  10  executes step S 617 . If on the other hand the requested shift position  2  is not N, the ECU  10  terminates the series of processes relating to shift command. 
     If having proceeded to step S 615 , the ECU  10  sets the target shift position  2  to F and instructs the ECU  230  to thereby bring the actual shift to F, and thereafter terminates the series of processes. 
     If having proceeded to step S 616 , the ECU  10  sets the target shift position  2  to R and instructs the ECU  230  to thereby bring the actual shift to R, and thereafter terminates the series of processes. 
     If having proceeded to step S 617 , the ECU  10  sets the target shift position  2  to N and instructs the ECU  230  to thereby bring the actual shift to N, and thereafter terminates the series of processes. 
       FIG. 7  is a flowchart of the shift-in prohibition buzzer process in Embodiment 1 of the present invention. In step S 701 , the ECU  10  determines whether or not the requested shift position  1  is set to other than N. If the requested shift position  1  is set to other than N, the ECU  10  executes step S 702 . If on the other hand the requested shift position  1  is N, the ECU  10  executes step S 704 . 
     In step S 702 , the ECU  10  determines whether or not the shift-in prohibition flag  1  is set to 1. If the shift-in prohibition flag  1  is set to 1, the ECU  10  executes step S 703 . If on the other hand the shift-in prohibition flag  1  is not set to 1, the ECU  10  executes step S 704 . 
     If having proceeded to step S 703 , the ECU  10  turns on the warning buzzer  15 , in order to inform the boat operator that the operation is abnormal, and executes step S 710 . 
     If having proceeded to step S 704 , on the other hand, the ECU  10  determines that the operation is not abnormal, turns off the warning buzzer  15 , and executes step S 710 . 
     In step S 710 , the ECU  10  determines whether or not the requested shift position  2  is set to other than N. If the requested shift position  2  is set to other than N, the ECU  10  executes step S 712 . If on the other hand the requested shift position  2  is N, the ECU  10  executes step S 714 . 
     In step S 712 , the ECU  10  determines whether or not the shift-in prohibition flag  2  is set to 1. If the shift-in prohibition flag  2  is set to 1, the ECU  10  executes step S 713 . If on the other hand the shift-in prohibition flag  2  is not set to 1, the ECU  10  executes step S 714 . 
     If having proceeded to step S 713 , the ECU  10  turns on the warning buzzer  15 , in order to inform the boat operator that the operation is abnormal, and thereafter terminates the series of processes of the shift-in prohibition buzzer. 
     If having proceeded to step S 714 , on the other hand, the ECU  10  determines that the operation is not abnormal, turns off the warning buzzer  15 , and thereafter terminates the series of processes of the shift-in prohibition buzzer. 
     The boat shift control device of Embodiment 1 explained above has a configuration for controlling in particular engines by way of a remote control ECU (corresponding to the ECU  10 ) at a maneuvering seat, in a drive-by-wire (DBW) system where a plurality of engines is installed in one boat and in which no wires are utilized. 
     The functions of the ECU  10  are summarized next. 
     (1) Simulated boat speed detection process function Function of calculating a simulated boat speed revolutions obtained by simulating boat speed on the basis of the rotational speeds of a plurality of engines. 
     (2) Turning mode detection process function 
     Function of detecting a “turning mode” denoting the state in which there is performed an operation of changing the orientation of the hull using a given specific engine alone, during docking, on the basis of the shift state and throttle state of a plurality of engines and on the basis of a calculated simulated boat speed, and of setting/resetting a turning mode flag. 
     (3) Shift-in prohibition determination process function 
     Function of setting/resetting a shift-in prohibition flag that prohibits shift-in of a respective engine, on the basis of the shift state and throttle state of the plurality of engines, the calculated simulated boat speed, and the state of the turning mode flag. 
     The process of setting the shift-in prohibition flag is not executed during the turning mode. The shift-in prohibition flag is reset as a result of a condition being satisfied where all the requested throttle opening degrees of the plurality of engines are lower than a pre-set opening degree determination value. The shift-in prohibition flag is reset also in a case where there is satisfied the condition where all the shift states of the plurality of engines are the neutral state. 
     (4) Shift command process function 
     Function of outputting a shift command to respective engines on the basis of the shift state of the plurality of engines and the state of the shift-in prohibition flag. 
     (5) Shift-in prohibition buzzer process function 
     Function of, in a state where the shift-in prohibition flag has been set, notifying by way of a warning sound that a shift-in prohibited state applies when the boat operator performs a shift-in operation to F or R. 
     The above functions allow eliciting the following effects during actual boat maneuvering. 
     In a case where a plurality of engines is mounted on one boat, the highest speed from among the engine rotational speeds is selected as a simulated boat speed, and is stored in a buffer. Simulated boat speed revolutions are calculated by performing a conjectured computation process using the selected rotational speed. 
     Next, shift-in is prohibited in a case where the lever is operated to forward (F) or reverse (R) in an attempt to operate the remaining engines, when the calculated simulated boat speed revolutions exceed a pre-set determination value, for instance during operation with only one engine from among the plurality thereof. As a result it becomes possible to protect the gears and engines during the shift operation in a state where propellers have turned due to accompanying rotation, without operating the remaining engines. 
     Further, shift-in is prohibited when the simulated boat speed revolutions exceed a determination value; once prohibited, shift-in stays so until the throttle states of all the connected engines become equal lower to or smaller than a pre-set determining degree of opening. 
     With shift-in prohibited, a state is brought about in which the gear cannot actually be put in when the lever is moved to forward (F) or reverse (R). Therefore, the maneuver intention of the boat operator is determined on the basis of a switch operation state of the lever, and an alert through a buzzer or LED can be outputted in a case where it is determined that the boat operator intends to maneuver the boat in a shift-in prohibited state. As a result, the boat operator can easily grasp, thanks to the warning output, that a shift-in prohibited state holds. 
     The purpose of the shift-in prohibited state in the present invention is to protect gears and engines during shift-in when in a state of boat speed equal to or higher than a boat speed established beforehand. During docking and turning, an operation is performed whereby the bearing of the hull is modified using a predetermined engine alone. During such docking and turning, the boat operator may conceivably operate only a specific engine at high revolutions. In some instances turning is accomplished by setting respective engines to forward (F) or reverse (R). 
     In such cases a shift-in prohibited state may be conceivably brought about during docking or turning, depending on pre-set data in order to determine the shift-in prohibition. Maneuverability during docking or turning is envisaged to become very poor as a result. 
     In the present invention, therefore, a turning mode is determined to apply in a case where it is detected that the shift states of the plurality of engines are a state such that turning involves mixed forward (F) and reverse (R), or when a state goes on, for a predetermined lapse of time, where the shift states of the plurality of engines are all forward (F) and the throttle states all lie within a determination value established beforehand. 
     As a characterizing feature, the state of shift-in prohibition is made absolutely invalid in a case where it is determined that the turning mode applies. In consequence it becomes possible to combine securing maneuverability during docking or turning with shift-in prohibition for the purpose of protecting gears and engines within a certain boat speed range, and also to secure maneuverability in the shift operation at low speed.