Marine Propulsion Device

This application claims the benefit of priority to Japanese Patent Application No. 2024-062697 filed on Apr. 9, 2024. The entire contents of this application are hereby incorporated herein by reference.

The present invention relates to marine propulsion devices.

A marine propulsion device having two drive shafts is known. For example, Japanese Patent Laid-Open Publication No. 2022-135453 (JP2022-135453A) discloses an outboard motor in which torque of a motor as a drive source is transmitted from a first drive shaft to a second drive shaft via a speed reduction mechanism.

Japanese Patent Laid-Open Publication No. 2021-30819 (JP2021-30819A) discloses an outboard motor in which power of an engine as a drive source is transmitted from a first drive shaft to a second drive shaft via a transmission unit such as gears. Rotation of the second drive shaft is transmitted to a propeller shaft via a shift mechanism that switches a shift position. At this time, the shift mechanism can switch a direction of the rotation transmitted from the second drive shaft to the propeller shaft.

However, since the shift mechanism to switch the shift position is disposed in a lower portion of the outboard motor in JP2021-30819A, available space in the lower portion is reduced. Therefore, when the shift mechanism is disposed in the marine propulsion device including two drive shafts, there is room for improvement from a viewpoint of saving available space in the lower portion.

Example embodiments of the present invention provide marine propulsion devices that save space in lower portions of the marine propulsion devices.

According to an example embodiment of the present invention, a marine propulsion device includes a drive source, a first drive shaft rotationally drivable by the drive source, a drive gear rotatable integrally with the first drive shaft, a second drive shaft parallel or substantially parallel to the first drive shaft, a driven gear drivable by the drive gear rotatable around a center axis of the second drive shaft, and a shift mechanism to switch a shift position. The drive gear and the driven gear are in an upper portion of the marine propulsion device, and the shift mechanism is above the driven gear.

According to another example embodiment of the present invention, a marine propulsion device includes a drive source, a first drive shaft rotationally drivable by the drive source, a drive gear rotatable integrally with the first drive shaft, a second drive shaft, a driven gear drivable by the drive gear and rotatable around a center axis of the second drive shaft, and a shift mechanism to switch a shift position. The drive gear and the driven gear are in an upper portion of the marine propulsion device, and the shift mechanism is above the driven gear.

According to another example embodiment of the present invention, a marine propulsion device includes a drive source, a first drive shaft rotationally drivable by the drive source, a drive gear rotatable integrally with the first drive shaft, a drive gear rotatable integrally with the first drive shaft, a second drive shaft parallel or substantially parallel to the first drive shaft, a driven gear drivable by the drive gear rotatable around a center axis of the second drive shaft, and a shift mechanism to switch a shift position. The drive gear and the driven gear are in an upper portion of the marine propulsion device, and at least a portion of the shift mechanism is above the driven gear.

According to the above example embodiments, space in the lower portions of the marine propulsion devices is saved.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.

Hereinafter, example embodiments of the present invention will be described with reference to the drawings.

is a schematic plan view showing a marine vessel to which a marine propulsion device according to an example embodiment of the present invention is provided.is a schematic left side view showing the marine propulsion device.

The marine vesselincludes a hulland two outboard motors. In, FWD, BWD, L, R, Z, and Zrespectively indicate forward, backward, leftward, rightward, upward, and downward directions of the marine vessel.

As shown in, the two outboard motorsare attached to a sternof the hullso as to be arranged side-by-side in a left-right direction. Since the two outboard motorshave the same configuration, only one of the outboard motorswill be described as a representative. The outboard motoris a marine propulsion device to propel the hull. The outboard motorincludes an engine, a steering mechanism, an ECU (Engine Control Unit), and an SCU (Steering Control Unit).

As shown in, the hullincludes a controllerand a manual operatorthat accepts an operation to control (steer) the marine vessel. The manual operatorincludes a remote controllera steering wheeland a joystick

A tilting operation of a lever (not shown) provided on the remote controllerchanges a thrust of the outboard motor(rpm of a propeller()) or switches a shift state of the outboard motor(a forward state, a backward state, and a neutral state). A rotating operation of the steering wheelsteers the outboard motor(changes a direction of the propellerwith respect to the hull). The marine vesselmoves translationally and turns by a combination of operations of the remote controllerand the steering wheel

The joystickincludes a lever (not shown) that can be tilted and rotated. When the lever of the joystickis tilted, rotated, or tilted and rotated, the thrust of the outboard motoris changed, the shift state of the outboard motoris switched, and/or the outboard motoris steered. The marine vesselcan move translationally, turn, or change a course by operating the lever of the joystick

The controlleris configured or programmed to control the ECUand the SCUof the outboard motorbased on an operation on the manual operator. The controllerincludes, for example, a CPU, a ROM, and a RAM.

In the outboard motor, the ECUcontrols driving of the engineand driving of a shift actuator (not shown) under the control of the controller. The SCUcontrols driving of the steering mechanismunder the control of the controller. Each of the ECUand SCUincludes, for example, a CPU, a ROM, and a RAM.

As shown in, the outboard motorincludes an outboard motor body. The outboard motor bodyis attached to the sternof the hullvia a bracket.

The outboard motor bodyincludes an upper portion, a lower portion, and a support portion(see). The configuration of the support portionwill be described in detail with reference to, but the support portiongenerally includes a movable caseand a steering shaft assembly. The support portionsupports the lower portionso as to be relatively rotatable with respect to the upper portionaround a steering shaftof the steering shaft assembly, and rotates integrally with the lower portion. That is, in the outboard motor, the upper portionof the outboard motor bodydoes not rotate with respect to the hull, and the lower portionrotates.

Hereinafter, the vertical direction in the outboard motor bodyis specified with reference to the attitude during navigation shown in.

The upper portionis attached to the sternvia the bracket. The lower portionincludes the propellerand is disposed below the upper portion. The upper portionincludes a cowlthat houses the engineand an upper casethat is disposed below the cowland attached to the stern. The lower portionincludes a lower case.

The outboard motor bodyincludes the engine, a first drive shaft, a second drive shaft, a gearing, a propeller shaft, and the propeller. The engineis an example of a drive source that provides a rotational force to rotate the propeller shaft. An engine output shaftof the engineis rotated by an output from a crankshaft (not shown). The first drive shaftis concentric with the engine output shaftand rotates integrally with the engine output shaft. The first drive shaftcorresponds to a first rotation shaft, and the second drive shaftcorresponds to a second rotation shaft.

The second drive shaftis separate from (i.e., not concentric with) the first drive shaftand the engine output shaft, and is parallel or substantially parallel to the first drive shaftand the engine output shaft. The first drive shaftis rotatable in one direction, and the second drive shaftis rotatable in both directions. The gearingis disposed in the lower case. The gearingis connected to a lower end of the second drive shaft. The propeller shaftis connected to the gearing. The propeller shaftis disposed behind the gearingso as to extend in a front-back direction. The propelleris connected to a rear end of the propeller shaft. The propelleris disposed outside the lower caseso as to be exposed to the outside of the outboard motor body.

A fixed caseis relatively fixed to the upper portion. The fixed caseis fixed to a steering housing (not shown) that covers the steering mechanism, and the steering housing is fixed to the upper portion. A water pump assemblyis disposed in the fixed case. The water pump assemblyis disposed at a lower endof the first drive shaftand is driven by the first drive shaft. The first drive shaftis rotated by the rotational force from the enginevia the engine output shaft. The water pump assemblysupplies cooling water to the engine.

is a perspective view showing a main drive mechanism that drives the water pump assemblyand the propeller. Components shown inare located in the upper portionexcept for the support portion.

is a vertical sectional view showing a principal portion of the main drive mechanism.is a vertical sectional view showing the steering mechanismand its periphery. The cross section shown inare parallel to a center axis Pof the first drive shaftand a center axis Pof the steering shaft assemblyand include the central axes Pand P. The center axis Pl is parallel or substantially parallel to the center axis P.

The main drive mechanism will be described with reference to.

First, as shown in, the main drive mechanism includes a dog clutch, a first bevel gear, a drive gear, the steering shaft assembly(see also), a pinion gear, the first drive shaft, a gear, the water pump assembly, a second bevel gear, a pinion gear, and a driven gear. The main drive mechanism further includes the second drive shaft, a reduction gear, a gear, the support portion, and a hydraulic cylinder(see, not shown in). The water pump assemblyincludes an upper housingand a lower housing. Both the drive gearand the driven gearare helical gears.

The steering mechanismincludes the support portion, a first mechanism, and a second mechanism. The first mechanism includes a motor (not shown), the reduction gear, the gear, and the gear. The second mechanism includes the hydraulic cylinder(), a rack gear (not shown), and the pinion gear.

The engine output shaftis rotationally driven by the output from the crankshaft (not shown). Then, the water pump assemblyis driven by the first drive shaftthat rotates integrally with the engine output shaft. In parallel with this, the drive gearrotating integrally with the first drive shaftdrives the driven gearto rotate.

A transmission mechanism to transmit the rotation of the first drive shaftto the second drive shaftincludes the dog clutch, the first bevel gear, the drive gear, the second bevel gear, the pinion gear, and the driven gear.

The rotation of the driven gearis transmitted to the first bevel gearand further to the second bevel gearvia the pinion gear. The first bevel gearand the second bevel gearrotate in opposite directions.

As will be described in detail below, a shift mechanismto switch a shift position is disposed above the driven gear. In the shift mechanism, forward, backward, and neutral are switched by moving the dog clutchin the axial direction of the second drive shaft.

The second drive shaftrotates integrally with the dog clutcharound the center axis P(). The second drive shaftrotates in the same direction as the first bevel gearor the second bevel gearthat is engaged with the dog clutch. The rotational force of the second drive shaftrotates the propeller shaft() via the gearingin the lower portion. The axial direction of the propeller shaftintersects (in the present example embodiment, is perpendicular to) the axial direction (the direction of the center axis P) of the second drive shaft.

The first bevel gearand the driven gearare disposed around a common sleeve() on the outer periphery of the second drive shaft. The first bevel gearincludes an extensionextending downward (). The extensionis always engaged with the driven gear, and thus the first bevel gearis always engaged with the driven gearand rotates integrally with the driven gear. That is, the driven gearis driven by the drive gear, and thus the first bevel gearrotates around the center axis P(axial center) integrally with the driven gear. Further, the engagement between the drive gearand the driven geartransmits the rotation of the first drive shaftto the first bevel gearwhile reducing the rotation speed.

The center axis Pis the center axis of the steering shaftof the steering shaft assemblyand is also the center axis of the second drive shaft. That is, the steering shaft assemblyis concentric with the second drive shaft. The pinion gearand the gearrotate integrally with the steering shaft assembly.

In the steering mechanism, either the first mechanism or the second mechanism is selectively operated in response to an instruction from a vessel operator. It is not necessary to provide both the first mechanism and the second mechanism, and a configuration in which only one of these mechanisms is provided is possible.

First, when the first mechanism is operated, a rotational force from a motor (not shown) in the first mechanism is transmitted to the gearvia the reduction gearand the gear. Thus, the movable caseis rotationally driven integrally with the steering shaft assembly. As a result, the lower portionis steered (rotationally driven) with respect to the upper portion.

On the other hand, when the second mechanism is operated, a rack gear (not shown) is moved by a driving force from the second mechanism (the hydraulic cylinder()), and the pinion gearis rotationally driven by the rack gear. As a result, the lower portionis steered (rotationally driven) with respect to the upper portion.

A water flow path is defined by the inner spaces of the lower case, the movable case, the fixed case, and the lower housingof the water pump assembly. The movable caseof the support portionis fixed to the lower portion, and in particular, the movable caseis fixed to an upper portion of the lower case. A plate() is interposed between the lower caseand the movable case. The plateis made of, for example, metal.

As shown in, a filteris fixed to the support portionin a space inside the support portion. In the inner space of the movable case, the filteris first fixed to a top of a cylindrical member, and the filteris further fixed to the movable case. Specifically, an annular memberis sandwiched between a bottom of the cylindrical memberand an upper surface of the plate. The filterand the top of the cylindrical memberare jointly fastened to the movable casewith bolts, for example. Therefore, the filteris also fixed to the lower portionvia the cylindrical memberand the annular member. The annular memberis made of an elastic member such as rubber.

As described above, the movable caseis driven to rotate by the first mechanism or the second mechanism. Since the fixed casedoes not rotate, a sliding portion is generated between the fixed caseand the movable case. Sealsandare disposed in the sliding portion. Therefore, the sliding portion between the fixed caseand the movable caseis sealed by the sealsand.

The shift mechanismwill be described with reference to. The shift mechanismis mainly disposed on the second drive shaft, and includes the dog clutch, the first bevel gear, the second bevel gear, the pinion gear, and a drive mechanism (a shift rodand a slide shaft). The shift mechanismis disposed in the upper portion. Since the shift mechanismdoes not need to be disposed in the lower portion, the space of the lower portioncan be saved.

The first bevel gearand the second bevel gearare rotatable around the center axis of the second drive shaft. The second bevel gearis disposed above the first bevel gearin the direction of the center axis P. The pinion gearis always engaged with the first bevel gearand the second bevel gear. The dog clutchis prevented from moving in the rotational direction with respect to the second drive shaft, and is movable in the direction of the center axis P.

The shift rodand the slide shaftof the drive mechanism drive the dog clutchin the direction of the center axis P. First, the slide shaftis inserted into the second drive shaftand moves in the direction of the center axis P. The slide shaftis inserted into the second drive shaftso that the shift mechanismis compact.

The dog clutchand the slide shaftare connected with a pin, and both move integrally in the direction of the center axis P. An upper end of the slide shaftincludes a cam engagement portionhaving a constricted shape (). On the other hand, a tip end of the shift rodserves as a cam portion(). The cam portionis engaged with the cam engagement portionThe cam portionis eccentric with respect to the center axis of the shift rod. The cam portionmoves up and down by the shift rodrotating around the center axis in a predetermined range and drives the cam engagement portionTherefore, the slide shaftmoves in the vertical direction (the direction of the center axis P) by the shift rodrotating within the predetermined range. Then, the dog clutchmoves integrally with the slide shaft.

The dog clutchswitches a rotating direction of the second drive shaftby selecting engagement with the first bevel gearor engagement with the second bevel gear. When the dog clutchmoves downward, it engages with the first bevel gear. In this case, the rotation of the first drive shaftis transmitted to the second drive shaftthrough the drive gear, the driven gear, the first bevel gear, and the dog clutch. Since the first bevel geartransmits the rotation in one of the two directions to the second drive shaftwithout passing through the pinion gearand the second bevel gear, a rotation transmission efficiency between the drive shaftsandis high.