A marine propulsion system

Abstract

The disclosure relates to a marine propulsion system for a marine vessel, comprising an engine, a propeller unit comprising one or more propellers, a transmission arranged between the engine and the propeller unit, a hydraulic clutch arrangement. The clutch arrangement controls a power transfer between the engine and the propeller unit. The clutch arrangement comprises a clutch plate and a clutch piston. The clutch piston is actuated by a first hydraulic area and/or a second hydraulic area. The first hydraulic area is pressurized by an electrically controlled proportional pressure valve and the second hydraulic area is pressurized by an electrically controlled on/off valve. The control unit is operatively connected with the electrically controlled proportional pressure valve and the electrically controlled on/off valve, and is configured to control the electrically controlled proportional pressure valve and the electrically controlled on/off valve.

What is claimed is: 
     
         1 . A marine propulsion system for a marine vessel, comprising
 an engine,   a propeller unit comprising one or more propellers,   a transmission arranged between the engine and the propeller unit,   a hydraulic clutch arrangement, the clutch arrangement is configured to control a power transfer between the engine and the propeller unit,   a control unit,   wherein the clutch arrangement comprises a clutch plate and a clutch piston, the clutch piston is configured to be actuated by a first hydraulic area and/or a second hydraulic area, and wherein the first hydraulic area is pressurized by an electrically controlled proportional pressure valve and the second hydraulic area is pressurized by an electrically controlled on/off valve, the control unit is operatively connected with the electrically controlled proportional pressure valve and the electrically controlled on/off valve, and is configured to control the electrically controlled proportional pressure valve and the electrically controlled on/off valve.   
     
     
         2 . The marine propulsion system of  claim 1 , wherein the control unit is configured to control the electrically controlled proportional pressure valve independently of the electrically controlled on/off valve, or the control unit is configured to control the electrically controlled on/off valve independently of the electrically controlled proportional pressure valve. 
     
     
         3 . The marine propulsion system of  claim 1 , further comprising an input unit for adjusting a speed of the marine vessel in a forward direction and/or in a reverse direction. 
     
     
         4 . The marine propulsion system of  claim 3 , wherein the control unit is operatively connected with the input unit. 
     
     
         5 . The marine propulsion system of  claim 1 , wherein the first hydraulic area is substantially equal in size to the second hydraulic area, the first hydraulic area being smaller than the second hydraulic area, or the first hydraulic area being larger than the second hydraulic area. 
     
     
         6 . The marine propulsion system of  claim 1 , wherein the control unit comprises a current controller, the current controller is configured to closed-loop current control the electrically controlled proportional pressure valve and/or the electrically controlled on/off valve. 
     
     
         7 . The marine propulsion system of  claim 1 , wherein the electrically controlled proportional pressure valve and/or the electrically controlled on/off valve is/are controlled by a predetermined current, the predetermined current is a current reference. 
     
     
         8 . The marine propulsion system of  claim 6 , wherein the current controller is configured to implement dithering of current 200 Hz/±10 mA to minimize hysteresis of the electrically controlled proportional pressure valve and/or the electrically controlled on/off valve. 
     
     
         9 . The marine propulsion system of  claim 1 , wherein the clutch arrangement has a predetermined actuation pressure, the predetermined actuation pressure is a pressure reference. 
     
     
         10 . The marine propulsion system of  claim 1 , further comprising one or more pressure sensor(s) being configured to measure an actuation pressure of the clutch arrangement. 
     
     
         11 . The marine propulsion system of  claim 1 , wherein the control unit comprises an actuation pressure controller. 
     
     
         12 . The marine propulsion system of  claim 10 , wherein the one or more pressure sensors are operatively connected with the actuation pressure controller. 
     
     
         13 . The marine propulsion system of  claim 10 , wherein the pressure sensor(s) is/are configured to measure forward and/or reverse actuation pressure, the measured actuation pressure is used as feedback to the actuation pressure controller. 
     
     
         14 . The marine propulsion system of  claim 11 , wherein the actuation pressure controller is configured to control the actuation pressure of the clutch arrangement by a closed-loop control. 
     
     
         15 . The marine propulsion system of  claim 1 , further comprising a propeller speed controller, the propeller speed controller is configured to control the propeller speed on basis of the propeller speed references. 
     
     
         16 . The marine propulsion system of  claim 1 , further comprising an engine controller configured to control an engine speed so as to avoid region with slip-stick near full clutch engagement. 
     
     
         17 . A marine vessel comprising a marine propulsion system of  claim 1 . 
     
     
         18 . A method for controlling a marine propulsion system of  claim 1 , comprising arranging a clutch arrangement comprising a clutch plate and a clutch piston, the clutch piston is configured to be actuated by a first hydraulic area and/or a second hydraulic area, pressurizing the first hydraulic area by an electrically controlled proportional pressure valve, pressurizing the second hydraulic area by an electrically controlled on/off valve, controlling the electrically controlled proportional pressure valve independently of the electrically controlled on/off valve or vice versa. 
     
     
         19 . The method of  claim 18 , further comprising setting and/or calculating a predetermined actuation pressure, the predetermined actuation pressure is a pressure reference. 
     
     
         20 . The method of  claim 19 , further comprising
 measuring an actuation pressure of the clutch arrangement,   providing an actuation pressure controller,   controlling the actuation pressure on basis of the reference pressure and/or the measured actuation pressure.