Abstract:
An engine control strategy for a marine vessel propulsion system receives a request for a gear from among plural transmission gears, determines an engine speed for the requested transmission gear shift, adjusts the engine to the determined speed for a predetermined amount of time, and prevents the requested transmission gear shift from occurring for the predetermined amount of time while maintaining the engine at the predetermined speed. After the predetermined amount of time elapses, the requested shift is allowed to occur.

Description:
RELATED APPLICATIONS 
     This application claims benefit of priority to Provisional Patent Application No. 61/114,694, filed on Nov. 14, 2008, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     This invention relates to an engine control system, and method, for controlling engine operation to improve gear shifting. 
     BACKGROUND 
     In a marine vessel propulsion system, such as an inboard, inboard/outboard, and outboard configuration, a transmission transmits power from the engine of the propulsion system to a propulsive force generator, such as a propeller. The transmission of such a system often produces a noticeable “clunking” vibration and sound when it is shifted into either a forward or reverse gear. Clunking occurs when a dog clutch or cone clutch that is rotating along with a shaft connected to the propulsive force generator suddenly engages with either a forward or reverse gear, which are rotating in correspondence with a drive gear coupled to the engine&#39;s output shaft. 
     Transmission gear clunking not only can cause an annoying sound and to the operator and passengers of a marine vessel, but also shock forces and heat generated from the undesirably high forces generated during impact shifting can cause drive components to fail. Elevated engine speeds during shifting also make the engines prone to stalling. 
     SUMMARY 
     Embodiments consistent with the claimed invention relate to an engine control strategies for facilitating gear shifting in a marine propulsion system. In one aspect, a requested shift is prevented from occurring until the speed of the engine of the propulsion system is reduced below a threshold value for a predetermined period of time. 
     In an embodiment consistent with the claimed invention, an engine control system of a marine vessel propulsion system includes a shifter and throttle control including movable element that generates a signal indicating a requested gear from among plural transmission gears and an engine throttle level corresponding to a position of the movable element, a controller connected to the shifter and throttle control and to an engine of the marine vessel propulsion system to monitor and control the speed of the engine, and a shift actuator moveably coupled to a clutch member that engages and disengages the requested transmission gear with a propulsion element. The controller is adapted to receive the shift and throttle request signal and to maintain the engine at a predetermined speed for a predetermined amount of time in response to the received request. The controller prevents the actuator from performing the requested shift for the predetermined amount of time while the engine is maintained at the predetermined speed, and allows the requested shift to occur after the predetermined amount of time elapses. 
     In another embodiment, a method of controlling an engine of a marine vessel propulsion system includes receiving a signal indicating a requested transmission gear shift and an engine throttle level, determining an engine speed for the requested transmission gear shift and adjusting the engine to the determined speed for a predetermined amount of time, preventing the requested transmission gear shift from occurring for the predetermined amount of time while maintaining the engine at the predetermined speed, and allowing the requested shift to occur after the predetermined amount of time elapses. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and exemplary only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention that together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a block diagram of a marine vessel propulsion system in accordance with an exemplary embodiment. 
         FIG. 2A  is a side view diagram of a lever type shifter and throttle control according to an exemplary embodiment. 
         FIG. 2B  is a top view diagram of joystick type shifter and throttle control according to an exemplary embodiment. 
         FIG. 3  is a graphical representation of a timeline showing an order of events of a shift and anticlunk strategy according to an exemplary embodiment. 
         FIG. 4  is a diagram of control logic for activating an anticlunk strategy according to an exemplary embodiment. 
         FIG. 5  is a diagram of timer control logic for an anticlunk strategy according to an exemplary embodiment. 
         FIG. 6  is a diagram of a state machine for controlling shifting according to an exemplary embodiment. 
         FIG. 7  is a diagram of logic that delays implementation of a shift command to a shift actuator according to an exemplary embodiment. 
         FIG. 8  is a diagram of control logic that determines whether to activate the delay logic of  FIG. 7 . 
         FIG. 9  is a diagram of control logic for determining when to lock out the throttle. 
         FIG. 10  is a diagram of throttle lockout logic including the control logic of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     The various aspects are described hereafter in greater detail in connection with a number of exemplary embodiments to facilitate an understanding of the invention. However, the invention should not be construed as being limited to these embodiments. Rather, these embodiments are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Many aspects of the invention are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function), by program instructions, such as program modules, being executed by one or more processors (e.g., a central processing unit (CPU) or microprocessor), or by a combination of both. Logic of embodiments consistent with the claimed invention can be implemented with any type of appropriate hardware and/or software, with portions residing in the form of computer readable storage medium with a control algorithm recorded thereon such as the executable logic and instructions disclosed herein, and can be programmed, for example, to include one or more look-up tables and/or calibration parameters. The computer readable medium can comprise a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disc read-only memory (CD-ROM), or any other solid-state, magnetic, and/or optical disk medium capable of storing information. Thus, various aspects can be embodied in many different forms, and all such forms are contemplated to be consistent with the scope of the claimed invention. 
     In conventional marine propulsion systems, engine speeds during shifting while in thrust vectoring mode (e.g., when using a joy-stick to control shifting and throttle) can be too high and cause high impact shifting having undesirably high forces. The resulting gear degradation makes the shifting experience noisy and can damage the drive. Additionally, elevated engine speeds during shifting also make the engines prone to stalling. 
     The invention provides a control strategy to improve vessel responsiveness and maneuverability, reduce gear vibration and/or noise arising from shock while shifting, prevent stalling during shifting, and prevent drive failures. The invention can be used across the power range of a marine vessel&#39;s propulsion system, and is especially effective during low speed vessel maneuvering to avoid excessive torque on the drive when shifting. 
       FIG. 1  shows an engine control system  100  for marine vessel propulsion system in accordance with an exemplary embodiment. The engine control system  100  can be used in any marine vessel propulsion system of plural configuration types, such as an inboard, inboard/outboard, or outboard types. As shown in  FIG. 1 , the engine control system  100  includes a shifter and throttle control  110  having a shifter/throttle position detector  112  for controlling the propulsion direction and speed. The shifter/throttle position detector  112  is communicatively connected to a controller  120  via channel  122 . The controller  120 , in turn, is communicatively connected to an engine  140  via channel  124 , and to a shift actuator  150  of a transmission  152  via a channel  126 . The actuator  150  can be energized by logic of the controller  120  to shift between a neutral state and forward or reverse gears of a gear case  154 . The channels  122 ,  124  and  126  can be a controller area network (CAN) or CAN bus automotive network, although other known communications channels can be used to provide communication between devices. The term “communicatively connected,” as used herein, can include any type of communications channel that can convey an electromagnetic signal, such as an optical fiber, wire or wireless channel. 
     An exemplary embodiment of the subject engine control system  100  can include an controller  120  electronically operable to implement the control strategy including, for example, executing logic/instructions, monitoring conditions of the engine, determining values/conditions, and commanding and/or controlling certain aspects of operation of the engine, by for example, controlling certain engine components, such as engine throttle, engine timing, the amount of fuel supplied to the engine and spark interruption. The electronic controller may be in communication with various engine and/or vessel sensors, such as engine throttle, engine speed, engine temperature, engine load, transmission speed, propeller speed, and vessel speed. The controller  120  may determine the shift request, check the thresholds disclosed herein, and determine or calculate the appropriate time delay(s). The controller  120  may be formed as an integral part of an engine control module (ECM), as a unit separate from an ECM, or more controllers that communicate with an ECM. 
     The position sensor  112  of the shift and throttle control  110  tracks the position and movement of a manipulatable element the throttle lever  120 . The position sensor  112  can be a potentiometer that varies in output voltage in correspondence with the position of a manipulatable element of the throttle control  110 , although another known analog or digital position sensor can be used.  FIGS. 2A and 2B  show shift and throttle controls according exemplary embodiments, which can include one or more position sensors to provide control in one or more dimensions. 
     As shown in  FIG. 2A , a “one dimensional” lever type shifter and throttle control  210  includes a manipulatable lever  212  that is pivotably attached to a pivot  213  to allow rotational movement between a central neutral position N and a reverse position R or forward position F at either side of the neutral position N. The throttle increases as the lever is moved to a greater angle from a neutral position in either the forward F or reverse R directions. It will be appreciated that an alternative one-dimensional embodiment can include a linearly sliding member, a dial and the like to provide shifting between a neutral state and a driving forward or reverse gear, and a desired throttle magnitude while in one of the driving gears. 
       FIG. 2B  is a top view of an embodiment of a joystick type shift and throttle control  214  having a stick  216  that can be manipulated in two dimensions. For example, the stick  216  can be moved in one of a forward (F), reverse (R), starboard (S), and port (P) direction, or in a direction oblique from one of the F, R, S or P directions, and can provide as much as 360 degrees of movement. The joystick throttle control can respond to pressure applied in a desired direction for proportional throttle control in the desired direction, and can have a resolution from as little as one speed to a continuum of proportional engine speed control. The joystick type shift and throttle control  214  can include a default position of the stick  216  at the center position, which corresponds to a neutral transmission state at an idling engine speed. In some embodiments, the stick  216  can be rotated about its central axis to provide rotational movement of the marine vessel. 
     The engine control system  100  shifts the transmission  152  “by wire” utilizing the communication channel  122  between the shifter and throttle  110 , and the communication channel  126  between the controller  120  and the shift actuator  150 . This allows for reduced shock, noise, and overspeed conditions because the timing of the shift and engine speed can be controlled based upon logic associated with the controller  120  and sensed conditions. 
       FIG. 3  is a diagram specifying an order or timing of events of an exemplary shift and anticlunk strategy in accordance with an embodiment.  FIGS. 4 to 8  depict exemplary logic for performing engine control in a shift strategy according to an embodiment. 
     Referring now  FIG. 3 , a sequence of events of exemplary shift and anticlunk strategies in accordance with an engine control embodiment can be carried out upon receiving a shift request from a “neutral” state into an in-gear state, for example, when a shifter and throttle control  110  is manipulated to move it from a neutral state to a forward gear. The engine control system checks that engine speed is below a given maximum threshold value, “Shift Lockout Threshold,” and then uses a series of timers to delay, or temporarily “lockout” a shift event and command a speed request to the controller  120 . 
     Starting at time t 1 , in process  310  the controller  120  receives a signal from the shift and throttle control  110  and determines that a shift and throttle request has been made. For example, the controller  120  can detect a change in voltage output of at least one monitored potentiometer associated with the shifter and throttle control  110 , which indicates that a shift is being requested. This detection causes the controller  120  to perform process  312  and command zero percent throttle to the engine  140 . 
     At time t 2 , the controller  120  compares the monitored engine speed with a predetermined threshold value and determines, in process  314 , when the speed of engine  140  is less than the Shift Lockout Threshold. At this time, the controller  120  starts a shift delay timer at process  316 , which locks out the requested shift for the period of the shift delay timer. 
       FIGS. 4 and 5  show exemplary shift anticlunk control logic, which determines, based on the received shift type, whether to activate anticlunk logic including an AntiClunk_Wait_Timer and an AntiClunk_Hold_Timer.  FIG. 4  shows the activation logic of the “Control” logic block of  FIG. 5 . As shown in  FIG. 4 , the Control block receives a “Shift Direction Request” from the helm (e.g., via movement of the shift and throttle control  110 ) and compares the received request to a previously made Shift Direction Request (i.e., “1/z” Shift Direction Request). The comparison logic in  FIG. 4  involves determining whether a previously requested shift state and presently requested shift state satisfy an “in-gear” shift state, i.e., one which includes a shift from neutral (4) to reverse (1), neutral (4) to forward (2), forward (2) to reverse (1), and reverse (1) to forward (2). Although not shown in the  FIG. 4  embodiment, shifting to an in-gear state can include shifts between gears in either the forward or the reverse direction, for example, a shift between 1 st  to 2 nd  gear in the reverse direction (i.e., 1 and 7), a shift between 1 st  to 2 nd  gear in forward direction (i.e., 2 and 8), and so on. 
     When the activation logic of  FIG. 4  outputs a Boolean value indicating activation of the shift AntiClunk control, the “Control” block in  FIG. 5  provides this activation value to the reset input of the Wait Counter, which causes the “AntiClunk_Wait_Timer” to start. This is represented in  FIG. 3  as process  318  at time t 2 , “ACLK Wait Starts.” When the Wait Counter counts until the value of the AntiClunk_Wait_Timer and expires at process  320 , “ACLK Wait Ends,” as shown at t 3  in  FIG. 3 , the controller  120  commands “Shift AntiClunk” active to the engine  140  and holds this command active until the Hold Counter completes counting the “AntiClunk_Hold_Timer” value. 
     When the AntiClunk_Hold_Timer is running (i.e., Shift AntiClunk is active), the controller  120  holds a target, commanded speed until the shift is completed. During this time, the Shift Delay Timer expires, see process  328  at t 4  in  FIG. 3 , and a shift command is sent to the shift actuator  150  at process  326 . 
       FIG. 6  is a diagram of an exemplary state machine  600  that controls the shifting of the shift actuator  150  for shifts between a neutral state and an in-gear state (i.e., a first gear of either a forward or reverse direction), or between an in-gear state and the neutral state. 
     When a request for a new gear comes from the helm via a manipulation of the shifter and throttle control  110 , the logic of the state machine  600  locks in a currently engaged gear until an RPM threshold is met. This is shown by the path from state  610 , which represents the transmission in a neutral state, to a state  620  when the shift request is for a reverse gear (i.e., shift request=1) is locked in neutral until the engine RPM becomes less than the Shift Lockout Threshold. Thereafter, the newly requested reverse gear is commanded to the shift actuator  150  in state  630 . Similarly, if a shift request for a forward gear is made while in the neutral state, the neutral state is locked in state  640  until the engine RPM becomes less than the Shift Lockout Threshold, and the requested forward gear is then commanded to the shift actuator in state  640 . 
     When shifting from an “in gear” state to a “neutral” state, embodiments can employ a “Shift Exit Lockout Threshold” to only allow shifting into neutral only if engine speed is below this set point (threshold). This is shown in state machine of  FIG. 6  by the path from state  630 , which represents the transmission in a reverse state, to a state  660  when the shift request is for a neutral state (i.e., shift request!=1) and the reverse gear is locked until the engine RPM becomes less than the Shift Exit Lockout Threshold. Thereafter, the newly requested neutral state is commanded to the shift actuator  150  in state  610 . Another path from an in-gear state to neutral is from state  650 , which represents the transmission in a forward gear state, to a state  660  when the shift request is received for a neutral state (i.e., shift request!=2) and the forward gear is locked until the engine RPM becomes less than the Shift Exit Lockout Threshold. Thereafter, the newly requested neutral state is commanded to the shift actuator  150  in state  610 . Allowing a shift into a neutral state from an in-gear state only if the engine speed is below a set point (Shift Exit Lockout Threshold) can prevent engine overspeed conditions. 
       FIG. 7  shows exemplary logic that implements a shift delay to the shift actuator  150 , in response from the Shift_Command output in states  630  and  650  of  FIG. 6 , so that the shift event can be timed properly. Whenever the shift delay logic is activated (logic of “control” block is shown in  FIG. 8 , the calibration “ShiftDelay_Hold_Timer” starts. While counting down the ShiftDelay_Hold_Timer, the logic on the lower left (i.e., “1/z”) holds the previous shift command. After the ShiftDelay_Hold_Timer expires, the new Shift_Command is sent to the shift actuator  150  (i.e., the “Shift Command In” is output to the “Shift Command Out”). 
       FIG. 8  shows Shift Delay Activation Control logic, which is the control logic of the “Control” block of  FIG. 7 . The Shift Delay Activation Control determines when the shift delay logic should become active and start the countdown timer. As can be seen in  FIG. 8 , the new incoming “Shift_Command” generated for the shift actuator  150  is compared to the previous “Shift_Command” (i.e., “1/z”) to determine when to activate the shift delay. A calibration can be provided the “ShiftDelay_Control” in  FIG. 8 , which would allow a calibrator the option to set whether to activate the delay on any gear change (i.e., in-gear to in-gear, neural to in-gear, and in-gear to neutral) or just when entering gear. 
     A throttle delay can be provided when the Shift Delay Timer expires to allow enough time for the shift to complete, and the shift is driven and engine speed is brought up to the requested throttle command after the throttle delay ends. Thus, once the logic of the engine control system specifies a target engine speed and timing delays to control throttle and shift, the control system monitors the time for which throttle is held and commands the shift event and then allows engine speed to increase to the requested throttle demand.  FIG. 9  is a diagram of exemplary control logic for determining when to lock out the throttle. This logic will start the lockout timer when the current “Shift_Command” is not equal to the last “Shift Command”, it is not “neutral,” and is either “forward” or “reverse.”  FIG. 10  is a diagram of exemplary throttle lockout logic including the control logic of  FIG. 9 . The logic of  FIG. 10  sets throttle to 0% whenever the “Shift Delay Logic” is active, “Shift_Locked” (via the state machine in  FIG. 6 ) is active, or “When to Lock” is active. 
     Each of the values of the Shift Delay Timer (t 2  to t 4 ), the AntiClunk_Wait_Timer (t 2  to t 3 ), the AntiClunk_Hold_Timer (t 3  to t 5 ), and the Throttle Delay (Wait) Timer (t 4  to t 5 ) can be calibrated. In one embodiment, the Shift Delay Timer has a calibrated value of 500 ms, the AntiClunk_Wait_Timer has a calibrated value of 50 ms, the AntiClunk_Hold_Timer has a calibrated value of 750 ms, and the Throttle Delay Timer has a calibrated value of 300 ms, although timer values can vary depending on a particular application or operating condition. 
     In other exemplary embodiments, the control system and method may use any system speed reference including but not limited to such references as Transmission Input Speed, Transmission Output Speed, Engine Crank Speed, Engine Cam Speed, Propeller Speed, or Vessel Speed. The strategy may alternatively use a torque reference point instead of system speed. 
     Of course, the control system and method may be performance tuned to enhance vessel responsiveness and maneuverability, gear noise reduction, stalling mitigation and increased drive reliability. 
     While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto. The present invention may be changed, modified and further applied by those skilled in the art. Therefore, this invention is not limited to the detail shown and described previously, but also includes all such changes and modifications.