OUTBOARD MOTOR AND MARINE VESSEL

An outboard motor includes an oil chamber, an oil passage connected to the oil chamber via an oil passage connection port, and an air guide, located in a vicinity of or adjacent to the oil passage connection port in a right-left direction of an outboard motor body, to guide air remaining in the oil chamber to the oil passage connection port when hydraulic oil is discharged from the oil chamber via the oil passage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2021-071161 filed on Apr. 20, 2021. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an outboard motor and a marine vessel, and more particularly, it relates to an outboard motor and a marine vessel each including a steering cylinder that rotates a steering shaft to rotate an outboard motor body in a right-left direction.

2. Description of the Related Art

An outboard motor including a steering cylinder that rotates a steering shaft to rotate an outboard motor body in a right-left direction is known in general. Such an outboard motor is disclosed in Japanese Patent Laid-Open No. 2020-168889, for example.

Japanese Patent Laid-Open No. 2020-168889 discloses an outboard motor including a steering cylinder that exerts a steering force on an outboard motor body. In the outboard motor disclosed in Japanese Patent Laid-Open No. 2020-168889, the steering cylinder extends in a right-left direction. The steering cylinder is connected to a steering shaft via a link mechanism. An oil chamber in the steering cylinder is connected to a steering pump via an oil passage, and hydraulic oil is supplied to and discharged from the oil chamber. The steering cylinder is driven (is moved in the right-left direction) by the hydraulic oil to generate a steering force so as to rotate the outboard motor body about the steering shaft. In the outboard motor disclosed in Japanese Patent Laid-Open No. 2020-168889, a connection port of the oil chamber in the steering cylinder to the oil passage is provided on the side of (lateral to) the steering cylinder that extends in the right-left direction.

In the outboard motor disclosed in Japanese Patent Laid-Open No. 2020-168889, as described above, the connection port of the oil chamber in the steering cylinder to the oil passage is provided on the side of (lateral to) the steering cylinder, and thus when air enters the oil chamber, the air stays in the oil chamber without escaping. When the air stays in the oil chamber, the operation of the steering cylinder may become unstable. Therefore, although not clearly described in Japanese Patent Laid-Open No. 2020-168889, an operator performs an operation to discharge air from the oil chamber to the outside (an air bleeding operation for the oil chamber) when air enters the oil chamber in a conventional outboard motor as disclosed in Japanese Patent Laid-Open No. 2020-168889. The air bleeding operation for the oil chamber includes a complex operation such as tilting a steering cylinder such that a connection port to an oil passage is located on the upper side of the steering cylinder after removing the steering cylinder from an outboard motor body, for example. Therefore, it is desired to easily bleed air from the oil chamber in the steering cylinder.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide outboard motors and marine vessels that each facilitate air bleeding from oil chambers in steering cylinders.

An outboard motor according to a preferred embodiment of the present invention includes an outboard motor body, a steering shaft, a steering cylinder including a piston rod extending in a right-left direction of the outboard motor body, a piston fixed to the piston rod, and a cylinder body including therein the piston and an oil chamber to store hydraulic oil, an oil passage connected to the oil chamber via an oil passage connection port to supply the hydraulic oil to the oil chamber and discharge the hydraulic oil from the oil chamber, and an air guide, located in a vicinity of or adjacent to the oil passage connection port in the right-left direction, to guide air remaining in the oil chamber to the oil passage connection port when the hydraulic oil is discharged from the oil chamber via the oil passage, wherein the steering cylinder is operable to rotate the steering shaft and the outboard motor body in the right-left direction by adjusting an amount of the hydraulic oil in the oil chamber and moving the cylinder body in the right-left direction.

An outboard motor according to a preferred embodiment of the present invention includes the air guide located in the right-left direction in the vicinity of or adjacent to the oil passage connection port to guide the air remaining in the oil chamber to the oil passage connection port when the hydraulic oil is discharged from the oil chamber via the oil passage. Accordingly, when the hydraulic oil is discharged from the oil chamber via the oil passage, the air guide guides the air remaining in the oil chamber to the oil passage connection port. That is, the air remaining in the oil chamber is guided to the oil passage connection port by the normal operation of the steering cylinder that discharges the hydraulic oil from the oil chamber via the oil passage, and thus the air is automatically discharged from the oil chamber to the outside without an operator performing a complex operation such as tilting the steering cylinder. Consequently, the air in the oil chamber of the steering cylinder is easily bled therefrom. Furthermore, the air is bled at any time only by a user of a marine vessel performing a steering operation (to change the propulsion direction of the marine vessel) while maneuvering the marine vessel, without the operator performing an air bleeding operation.

In an outboard motor according to a preferred embodiment of the present invention, the air guide preferably guides air remaining in an upper portion of the oil chamber to the oil passage connection port via an outer peripheral side flow passage provided on an outer peripheral side of the air guide when the hydraulic oil is discharged from the oil chamber. Accordingly, the upper portion (outer peripheral side) of the oil chamber is closer to the outer peripheral side flow passage than the inner peripheral side of the oil chamber, and the air is lower in viscosity than the hydraulic oil, and thus when the hydraulic oil is discharged from the oil chamber via the oil passage, the air remaining in the upper portion (outer peripheral side) of the oil chamber is preferentially discharged to the outside from the oil chamber via the outer peripheral side flow passage. Consequently, when the hydraulic oil is discharged from the oil chamber via the oil passage, the air guide reliably guides the air remaining in the upper portion of the oil chamber to the oil passage connection port.

In such a case, the air guide preferably has a disk shape, and the outer peripheral side flow passage is preferably defined by an outer peripheral surface of the air guide and an inner peripheral surface of the oil chamber. Accordingly, with the air guide, the outer peripheral side flow passage that guides the air remaining in the upper portion (outer peripheral side) of the oil chamber to the oil passage connection port is easily provided on the outer peripheral side of the air guide.

In an outboard motor in which the air remaining in the upper portion of the oil chamber is guided to the oil passage connection port via the outer peripheral side flow passage provided on the outer peripheral side of the air guide, the air guide preferably supplies the hydraulic oil to the oil chamber via an inner peripheral side flow passage provided on an inner peripheral side of the outer peripheral side flow passage in addition to the outer peripheral side flow passage when the hydraulic oil is supplied to the oil chamber. Accordingly, when the hydraulic oil is supplied to the oil chamber, the sectional area of a flow passage through which the hydraulic oil is supplied is increased as compared with a case in which the flow passage through which the hydraulic oil is supplied is limited to the outer peripheral side flow passage. Consequently, the pressure loss of the hydraulic oil is decreased when the hydraulic oil is supplied to the oil chamber.

In such a case, the air guide preferably moves in the right-left direction in the oil chamber to close the inner peripheral side flow passage when the hydraulic oil is discharged from the oil chamber and to open the inner peripheral side flow passage when the hydraulic oil is supplied to the oil chamber. Accordingly, the air guide is moved in the right-left direction in the oil chamber such that the outer peripheral side flow passage is easily provided when the hydraulic oil is discharged from the oil chamber, and the outer peripheral side flow passage and the inner peripheral side flow passage are easily provided when the hydraulic oil is supplied to the oil chamber.

In an outboard motor including the air guide that moves in the right-left direction in the oil chamber, the air guide preferably includes a contact portion to contact an end surface of the oil chamber in the right-left direction, and the air guide preferably moves in the right-left direction to a contact position at which the contact portion contacts the end surface to close the inner peripheral side flow passage when the hydraulic oil is discharged from the oil chamber, and moves in the right-left direction to a separated position at which the contact portion is spaced apart from the end surface to open the inner peripheral side flow passage when the hydraulic oil is supplied to the oil chamber. Accordingly, the air guide is moved in the right-left direction between the contact position and the separated position in the oil chamber such that the inner peripheral side flow passage is easily closed when the hydraulic oil is discharged from the oil chamber, and the inner peripheral side flow passage is easily opened when the hydraulic oil is supplied to the oil chamber.

In such a case, the air guide preferably moves to the contact position in the right-left direction due to a flow of the hydraulic oil discharged from the oil chamber to the oil passage connection port when the hydraulic oil is discharged from the oil chamber, and moves to the separated position in the right-left direction due to a flow of the hydraulic oil supplied from the oil passage connection port to the oil chamber when the hydraulic oil is supplied to the oil chamber. Accordingly, the air guide is moved to the contact position in the right-left direction through the normal operation of the steering cylinder that discharges the hydraulic oil from the oil chamber, and the air guide is moved to the separated position in the right-left direction through the normal operation of the steering cylinder that supplies the hydraulic oil to the oil passage, and thus the air guide is moved in the right-left direction to the contact position and the separated position in the oil chamber without separately providing a dedicated movement mechanism to move the air guide.

An outboard motor including the air guide that moves in the right-left direction to the contact position when the hydraulic oil is discharged from the oil chamber, and moves in the right-left direction to the separated position when the hydraulic oil is supplied to the oil chamber preferably further includes a restrictor to restrict the air guide from moving to a side opposite to the contact position relative to the separated position in the right-left direction. Accordingly, the moving range of the air guide is limited between the contact position and the separated position in the right-left direction by the restrictor, and thus an excessive increase in the moving range of the air guide is significantly reduced or prevented.

In an outboard motor including the air guide that moves in the right-left direction to the contact position when the hydraulic oil is discharged from the oil chamber, and moves in the right-left direction to the separated position when the hydraulic oil is supplied to the oil chamber, the oil passage connection port is preferably located in a vicinity of or adjacent to the end surface in the right-left direction. Accordingly, the separated position is located relatively close to the end surface in the right-left direction, and thus an excessive increase in the moving range of the air guide is significantly reduced or prevented.

In an outboard motor including the air guide that moves in the right-left direction to the contact position when the hydraulic oil is discharged from the oil chamber, and moves in the right-left direction to the separated position when the hydraulic oil is supplied to the oil chamber, the oil passage is preferably provided in the piston rod, the oil passage connection port is preferably provided on an outer peripheral surface of the piston rod, the piston rod is preferably provided on an inner peripheral side of the oil chamber, and the air guide preferably further includes, as the contact portion, a plurality of first protrusions that protrude toward the end surface in the right-left direction, and an inside-outside connection recess located between the plurality of first protrusions to connect an outer peripheral side of the oil chamber to the inner peripheral side. Accordingly, the plurality of first protrusions corresponding to the contact portion easily close the inner peripheral side flow passage when the hydraulic oil is discharged from the oil chamber, and easily open the inner peripheral side flow passage when the hydraulic oil is supplied to the oil chamber. Furthermore, the inside-outside connection recess easily connects, on the end surface side of the air guide, the outer peripheral side flow passage to the oil passage connection port provided on the outer peripheral surface of the piston rod on the inner peripheral side when the hydraulic oil is discharged from the oil chamber, and easily connects, on the end surface side of the air guide, the outer peripheral side flow passage and the inner peripheral side flow passage to the oil passage connection port when the hydraulic oil is supplied to the oil chamber.

In such a case, the air guide preferably further includes, as the inner peripheral side flow passage, a through-hole provided on at least one of the plurality of first protrusions extending therethrough in the right-left direction. Accordingly, with the through-hole, the inner peripheral side flow passage, which is closed due to contact of the plurality of first protrusions with the end surface in the right-left direction when the hydraulic oil is discharged from the oil chamber, and is opened due to being spaced apart from the plurality of first protrusions from the end surface in the right-left direction when the hydraulic oil is supplied to the oil chamber, is easily provided.

In an outboard motor including the air guide that includes the through-hole as the inner peripheral side flow passage, the through-hole is preferably provided on each of the plurality of first protrusions. Accordingly, the sectional area of the inner peripheral side flow passage is easily increased as compared with a case in which the through-hole is provided on one or more but not all of the plurality of first protrusions. Consequently, the pressure loss of the hydraulic oil is effectively decreased when the hydraulic oil is supplied to the oil chamber.

In an outboard motor including the air guide that includes the through-hole as the inner peripheral side flow passage, the plurality of first protrusions each preferably have a sectoral shape as viewed in the right-left direction, and the through-hole preferably has a sectoral shape smaller than the sectoral shape of each of the plurality of first protrusions as viewed in the right-left direction. Accordingly, the sectional area of the inner peripheral side flow passage is easily increased as compared with a case in which the through-hole does not have the same sectoral shape as the plurality of first protrusions. Consequently, the pressure loss of the hydraulic oil is effectively decreased when the hydraulic oil is supplied to the oil chamber.

In an outboard motor in which the oil passage connection port is provided on the outer peripheral surface of the piston provided in the cylinder body, the oil passage connection port is preferably provided on a portion of the outer peripheral surface in a circumferential direction of the piston rod, and the air guide preferably further includes a first annular recess recessed away from the end surface with respect to the plurality of first protrusions on the inner peripheral side to connect the inside-outside connection recess to the oil passage connection port. Accordingly, the inside-outside connection recess that connects the outer peripheral side to the inner peripheral side is easily connected to the oil passage connection port provided on a portion of the outer peripheral surface of the piston rod in the circumferential direction by the first annular recess.

In an outboard motor including the air guide that moves in the right-left direction to the contact position when the hydraulic oil is discharged from the oil chamber, and moves in the right-left direction to the separated position when the hydraulic oil is supplied to the oil chamber, the oil passage is preferably located in front of, behind, or below the steering cylinder, the oil passage connection port is preferably provided on an inner peripheral surface of the cylinder body, and the air guide preferably further includes, as the contact portion, a second protrusion that protrudes toward the end surface in the oil chamber. Accordingly, the second protrusion corresponding to the contact portion easily closes the inner peripheral side flow passage when the hydraulic oil is discharged from the oil chamber, and easily opens the inner peripheral side flow passage when the hydraulic oil is supplied to the oil chamber.

In such a case, the air guide preferably further includes, as the outer peripheral side flow passage, a notch provided on the outer peripheral side of the air guide extending therethrough in the right-left direction. Accordingly, with the notch, the outer peripheral side flow passage is easily provided in the oil chamber when the hydraulic oil is discharged from the oil chamber.

In an outboard motor in which the oil passage connection port is provided on the inner peripheral surface of the cylinder body, the oil passage connection port is preferably provided on a portion of the inner peripheral surface in a circumferential direction of the cylinder body, and the air guide preferably further includes a second annular recess recessed away from the end surface with respect to the second protrusion on the outer peripheral side of the air guide and connected to the oil passage connection port. Accordingly, the outer peripheral side flow passage is easily connected to the oil passage connection port provided on a portion of the inner peripheral surface of the cylinder body in the circumferential direction by the second annular recess.

A marine vessel according to a preferred embodiment of the present invention includes a hull including a steering wheel, and an outboard motor attached to the hull. The outboard motor includes an outboard motor body, a steering shaft, a steering cylinder including a piston rod extending in a right-left direction of the outboard motor body, a piston fixed to the piston rod, and a cylinder body including therein the piston and an oil chamber to store hydraulic oil, an oil passage connected to the oil chamber via an oil passage connection portion to supply the hydraulic oil to the oil chamber and discharge the hydraulic oil from the oil chamber, and an air guide, located in a vicinity of or adjacent to the oil passage connection port in the right-left direction, to guide air remaining in the oil chamber to the oil passage connection port when the hydraulic oil is discharged from the oil chamber via the oil passage, wherein the steering cylinder is operable to rotate the steering shaft and the outboard motor body in the right-left direction by adjusting an amount of the hydraulic oil in the oil chamber and moving the cylinder body in the right-left direction based on an operation of the steering wheel.

A marine vessel according to a preferred embodiment of the present invention includes the air guide, located in the right-left direction in the vicinity of or adjacent to the oil passage connection port connecting the oil chamber to the oil passage, to guide the air remaining in the oil chamber to the oil passage connection port when the hydraulic oil is discharged from the oil chamber via the oil passage. Accordingly, similarly to the outboard motors according to preferred embodiments of the present invention described above, the air remaining in the oil chamber is guided to the oil passage connection port by the normal operation of the steering cylinder that discharges the hydraulic oil from the oil chamber via the oil passage, and thus the air is automatically discharged from the oil chamber to the outside without an operator performing a complex operation such as tilting the steering cylinder. Consequently, similarly to the outboard motors according to preferred embodiments of the present invention described above, the air in the oil chamber of the steering cylinder is easily bled.

In a marine vessel according to a preferred embodiment of the present invention, the air guide preferably guides air remaining in an upper portion of the oil chamber to the oil passage connection port via an outer peripheral side flow passage provided on an outer peripheral side of the air guide when the hydraulic oil is discharged from the oil chamber. Accordingly, similarly to the outboard motors according to preferred embodiments of the present invention described above, when the hydraulic oil is discharged from the oil chamber via the oil passage, the air remaining in the upper portion (outer peripheral side) of the oil chamber is preferentially discharged to the outside from the oil chamber via the outer peripheral side flow passage. Consequently, similarly to the outboard motors according to preferred embodiments of the present invention described above, when the hydraulic oil is discharged from the oil chamber via the oil passage, the air guide reliably guides the air remaining in the upper portion of the oil chamber to the oil passage connection port.

In such a case, the air guide preferably has a disk shape, and the outer peripheral side flow passage is preferably defined by an outer peripheral surface of the air guide and an inner peripheral surface of the oil chamber. Accordingly, similarly to the outboard motors according to preferred embodiments of the present invention described above, with the disk-shaped air guide, the outer peripheral side flow passage that guides the air remaining in the upper portion (outer peripheral side) of the oil chamber to the oil passage connection port is easily provided on the outer peripheral side of the air guide.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are hereinafter described with reference to the drawings.

First Preferred Embodiment

The structure of a marine vessel100including outboard motors120(two outboard motors, for example) according to a first preferred embodiment of the present invention is now described with reference toFIGS. 1 to 8.

As shown inFIG. 1, the marine vessel100includes a hull110and the outboard motors120. The outboard motors120are attached to a rear transom of the hull110. The outboard motors120are marine propulsion devices that propel the hull110. The marine vessel100may be used for sightseeing in a canal and a lake, for example. The marine vessel100may be a relatively small marine vessel.

In the figures, arrow FWD and arrow BWD represent the front side and the rear side of the marine vessel100, respectively. In the figures, arrow L and arrow R represent the left side and the right side of the marine vessel100, respectively. In the figures, arrow Z1and arrow Z2represent the upper side and the lower side of the marine vessel100, respectively.

The hull110includes a steering wheel111. The steering wheel111receives a user's operation to cause the outboard motors120to change the propulsion direction of the hull110. As a user operates the steering wheel111, an electric signal is transmitted from the steering wheel111to a steering control unit (not shown) provided in each of the outboard motors120. The steering control unit controls a steering motor46b(seeFIG. 4) of a steering device40(seeFIG. 2) provided in each of the outboard motors120to change the propulsion direction of the hull110based on the electric signal transmitted from the steering wheel111.

As shown inFIG. 2, the outboard motors120each include an outboard motor body10, a pair of clamp brackets20to attach the outboard motor body10to the transom of the hull110, and a swivel bracket30to support the outboard motor body10. Furthermore, the outboard motors120each include a hydraulic power trim-tilt device (not shown) to rotate the outboard motor body10in an upward-downward direction and the hydraulic steering device40to rotate the outboard motor body10in a right-left direction.

The outboard motor body10includes an engine11, a drive shaft12, a propeller shaft13, and a propeller14. The engine11is, for example, an internal combustion engine that generates a driving force. The drive shaft12and the propeller shaft13transmit a driving force from the engine11to the propeller14. The propeller14generates a thrust force (a propulsive force to propel the hull110) by rotating in the water with the driving force transmitted from the engine11.

The outboard motor body10is rotated in the upward-downward direction together with the swivel bracket30with respect to the clamp brackets20by the power trim-tilt device. Thus, when the hull110is propelled, the upward-downward orientation of the propeller14positioned in the water is adjusted, and when the hull110is stopped or starts to be propelled, the position of the propeller14is changed between underwater and above water. Furthermore, the outboard motor body10is rotated in the right-left direction with respect to the swivel bracket30(clamp brackets20) by the steering device40. Thus, when the hull110is propelled, the right-left orientation of the propeller14positioned in the water is adjusted.

As shown inFIG. 3, the clamp brackets20are attached to the transom of the hull110. A pair of clamp brackets20are spaced apart from each other in the right-left direction. The swivel bracket30is attached to the clamp brackets20so as to be rotatable about a tilt shaft (not shown) that extends in the right-left direction. The outboard motor body10is attached to the swivel bracket30via a steering shaft (not shown) that extends in the upward-downward direction. That is, the clamp brackets20rotatably support the swivel bracket30and the outboard motor body10.

The swivel bracket30is located between the pair of clamp brackets20in the right-left direction. The swivel bracket30is attached to the pair of clamp brackets20via the tilt shaft. The swivel bracket30rotates in the upward-downward direction by rotating about the tilt shaft.

The power trim-tilt device is attached to the clamp brackets20. The power trim-tilt device is located between the pair of clamp brackets20. The power trim-tilt device rotates the swivel bracket30and the outboard motor body10in the upward-downward direction about the central axis91of the tilt shaft.

As shown inFIG. 4, the steering device40includes a steering cylinder41, an oil passage42(seeFIG. 5), an adapter44, oil pipes45, and a steering oil supply/discharge device46. As shown inFIG. 5, the steering cylinder41includes an oil chamber51to store hydraulic oil. As shown inFIG. 4, the steering oil supply/discharge device46includes a steering pump46aand a steering motor46b. The oil chamber51(seeFIG. 5) is connected to the steering pump46avia the oil passage42, the adapter44, and the oil pipes45. The steering motor46bdrives the steering pump46aunder the control of the steering control unit to supply the hydraulic oil from the steering pump46ato the oil chamber51and discharge the hydraulic oil from the oil chamber51to the outside. That is, the oil passage42is provided to supply the hydraulic oil to the oil chamber51and discharge the hydraulic oil from the oil chamber51.

As shown inFIG. 5, the steering cylinder41includes a piston rod52that extends in the right-left direction of the outboard motor body10, a piston53fixed to the piston rod52, and a cylinder body54with the piston53therein and the oil chamber51therein to store hydraulic oil. Specifically, a left end and a right end of the piston rod52that extends in the right-left direction are supported by the pair of clamp brackets20, respectively, while being rotatable with respect to the pair of clamp brackets20. The piston53is fixed to the piston rod52in a central portion between the pair of clamp brackets20in the right-left direction. The piston53divides the internal space of the cylinder body54into a space on the left side of the piston53and a space on the right side of the piston53. Thus, a left oil chamber51aon the left side of the piston53and a right oil chamber51bon the right side of the piston53are provided in the cylinder body54as the oil chamber51that stores hydraulic oil.

The steering cylinder41adjusts the amount of hydraulic oil in the oil chamber51to move the cylinder body54in the right-left direction so as to rotate the steering shaft and the outboard motor body10(seeFIG. 3) in the right-left direction. Specifically, the steering cylinder41is rotatably attached to the clamp brackets20(seeFIG. 3) via the piston rod52. The steering oil supply/discharge device46(seeFIG. 4) supplies hydraulic oil to one of the left oil chamber51aand the right oil chamber51b, and discharges hydraulic oil from the other of the left oil chamber51aand the right oil chamber51b. Thus, with an increase in the hydraulic oil stored in one of the left oil chamber51aand the right oil chamber51band a decrease in the hydraulic oil stored in the other of the left oil chamber51aand the right oil chamber51b, the cylinder body54moves in the right-left direction. The movement of the cylinder body54in the right-left direction is transmitted to the steering shaft, and the steering shaft rotates in the right-left direction. Thus, the outboard motor body10attached to the steering shaft rotates about the central axis92of the steering shaft in the right-left direction, and the propulsion direction of the hull110is changed.

In the first preferred embodiment, the oil passage42is provided in the piston rod52. Specifically, the oil passage42including a first end connected to the oil pipes45(seeFIG. 4) and a second end connected to the oil chamber51is provided inside the piston rod52. The oil passage42includes an oil passage42aconnected to the left oil chamber51aand an oil passage42bconnected to the right oil chamber51b. The piston rod52has a double pipe structure. The oil passage42ais an inner pipe of the double pipe. The oil passage42bis a region between the inner pipe and an outer pipe of the double pipe.

In the first preferred embodiment, an oil passage connection port55, which is a connection port of the oil chamber51to the oil passage42, is provided on a portion of the outer peripheral surface52aof the piston rod52provided in the cylinder body54in the circumferential direction. Specifically, an oil passage connection port55aof the oil passage42aconnected to the left oil chamber51aextends from the inner pipe of the double pipe to an end (outer peripheral surface52a) of the left oil chamber51aon the piston rod52side toward the outer peripheral side of the piston rod52inside the piston rod52. An oil passage connection port55bof the oil passage42bconnected to the right oil chamber51bextends from the outer pipe of the double pipe to an end (outer peripheral surface52a) of the right oil chamber51bon the piston rod52side toward the outer peripheral side of the piston rod52inside the piston rod52. A plurality of (four, for example) oil passage connection ports55aand a plurality of (four, for example) oil passage connection ports55bare provided at equal or substantially equal intervals in the circumferential direction as viewed in the axial direction (right-left direction) of the piston rod52.

In the first preferred embodiment, the oil passage connection port55is located in the vicinity of or adjacent to an end surface56of the oil chamber51in the right-left direction. Specifically, the oil passage connection port55aof the oil passage42aconnected to the left oil chamber51ais located such that the position of the oil passage connection port55aon the piston53side (right side) in the right-left direction and the location of the end surface56aof the left oil chamber51aon the piston53side are the same or substantially the same as each other in the right-left direction. Similarly, the oil passage connection port55bof the oil passage42bconnected to the right oil chamber51bis positioned such that the location of the oil passage connection port55bon the piston53side (left side) in the right-left direction and the location of the end surface56bof the right oil chamber51bon the piston53side are the same or substantially the same as each other in the right-left direction.

As shown inFIG. 6, in the first preferred embodiment, the outboard motor120(seeFIG. 2) includes an air guide70located in the vicinity of or adjacent to the oil passage connection port55to guide air60remaining in the oil chamber51to the oil passage connection port55when the hydraulic oil is discharged from the oil chamber51via the oil passage42. The air60(seeFIG. 7) remaining in the oil chamber51includes air that remains in the oil chamber51without being discharged from the oil passage connection port55after the air60enters the oil chamber51when the steering cylinder41is assembled, for example.FIG. 6shows a state in which the hydraulic oil is discharged from the left oil chamber51ato the oil passage42avia the oil passage connection port55a, and the hydraulic oil is supplied from the oil passage42bto the right oil chamber51bvia the oil passage connection port55b. InFIG. 6, the hatching of the air guide70indicating a cross-section is omitted in order to clearly show the shape of the air guide70.

In the first preferred embodiment, when the hydraulic oil is discharged from the oil chamber51, the air guide70guides the air60remaining in an upper portion of the oil chamber51to the oil passage connection port55via an outer peripheral side flow passage81provided on the outer peripheral side of the air guide70. Specifically, as shown inFIG. 7, the air60is lighter than the hydraulic oil, and thus the air60that has entered the oil chamber51remains in the upper portion of the oil chamber51. The oil chamber51has a circular shape as viewed in the axial direction of the piston rod52, and thus the upper portion of the oil chamber51includes a portion of the oil chamber51on the outer peripheral side. Furthermore, the air60is lower in viscosity than the hydraulic oil. Therefore, as shown inFIG. 6, when the hydraulic oil is discharged from the oil chamber51to the oil passage42via the outer peripheral side flow passage81, the air60remaining in the upper portion (outer peripheral side) of the oil chamber51is preferentially discharged. InFIG. 7, the piston rod52having a double pipe structure is simplified and drawn as a single pipe structure, and a plurality of oil passage connection ports55are simplified and drawn as only one.

As shown inFIG. 8, in the first preferred embodiment, the air guide70has a disk shape. As shown inFIG. 6, the outer peripheral side flow passage81is defined by the outer peripheral surface70aof the disk-shaped air guide70and the inner peripheral surface51cof the oil chamber51. Specifically, the outer peripheral side flow passage81is an annular gap between the outer peripheral surface70aof the disk-shaped air guide70and the inner peripheral surface51cof the oil chamber51. The width of the annular gap between the outer peripheral surface70aand the inner peripheral surface51cis set to several millimeters, for example. A hole through which the piston rod52on the inner peripheral side of the air guide70penetrates is slightly larger than the diameter of the piston rod52(is much smaller than the width of the annular gap between the outer peripheral surface70aand the inner peripheral surface51c). Thus, the air guide70moves within a predetermined range described below in the oil chamber51while being guided by the outer peripheral surface52aof the piston rod52.

In the first preferred embodiment, the air guide70supplies hydraulic oil to the oil chamber51via an inner peripheral side flow passage82provided on the inner peripheral side of the outer peripheral side flow passage81in addition to the outer peripheral side flow passage81when the hydraulic oil is supplied to the oil chamber51. Specifically, as shown inFIG. 8, the inner peripheral side flow passage82provided on the inner peripheral side of the outer peripheral side flow passage81is provided in the air guide70. As shown inFIG. 6, the air guide70allows the hydraulic oil to pass through the outer peripheral side flow passage81and the inner peripheral side flow passage82when the hydraulic oil is supplied from the oil chamber51to the oil passage42via the oil passage connection port55.

In the first preferred embodiment, the air guide70moves in the right-left direction in the oil chamber51to close the inner peripheral side flow passage82when the hydraulic oil is discharged from the oil chamber51and to open the inner peripheral side flow passage82when the hydraulic oil is supplied to the oil chamber51. Specifically, the air guide70includes a contact portion71that contacts the end surface56in right-left direction in the oil chamber51. The air guide70moves in the right-left direction to a contact position P1at which the contact portion71contacts the end surface56to close the inner peripheral side flow passage82when the hydraulic oil is discharged from the oil chamber51, and moves in the right-left direction to a separated position P2at which the contact portion71is spaced apart from the end surface56to open the inner peripheral side flow passage82when the hydraulic oil is supplied to the oil chamber51.

Specifically, in the first preferred embodiment, as shown inFIG. 8, the air guide70includes, as the contact portion71, a plurality of (eight) first protrusions72that protrude toward the end surface56(seeFIG. 6) in the right-left direction, and inside-outside connection recesses73located between the plurality of (eight) first protrusions72to connect the outer peripheral side of the oil chamber51to the inner peripheral side of the oil chamber51(seeFIG. 6). The piston rod52(seeFIG. 6) is provided on the inner peripheral side of the oil chamber51. Furthermore, the air guide70includes, as the inner peripheral side flow passage82, a through-hole72aprovided on at least one of the plurality of (eight) first protrusions72to penetrate or extend therethrough in the right-left direction. That is, as shown inFIG. 6, when the hydraulic oil is discharged from the left oil chamber51a(oil chamber51) to the oil passage42a(oil passage42) via the oil passage connection port55a(oil passage connection port55), the air guide70moves to the contact position P1, and surfaces72bof the plurality of first protrusions72on the end surface56side in the right-left direction contact the end surface56in the right-left direction. In this state, the through-hole72acorresponding to the inner peripheral side flow passage82is closed. The air60that has flowed from the left oil chamber51a(oil chamber51) to the end surface56side in the right-left direction via the outer peripheral side flow passage81flows from the outer peripheral side to the inner peripheral side via the inside-outside connection recesses73. When the hydraulic oil is supplied from the oil passage42b(oil passage42) to the right oil chamber51b(oil chamber51) via the oil passage connection port55b(oil passage connection port55), the air guide70moves to the separated position P2, and the surfaces72bof the plurality of first protrusions72on the end surface56side in the right-left direction are spaced apart from the end surface56in the right-left direction. In this state, the through-hole72acorresponding to the inner peripheral side flow passage82is opened.

As shown inFIG. 8, in the first preferred embodiment, each of the plurality of (eight) first protrusions72has a sectoral shape as viewed in the right-left direction. The through-hole72ahas a sectoral shape smaller than the sectoral shape of each of the plurality of first protrusions72as viewed in the right-left direction. That is, the surfaces72bof the plurality of first protrusions72on the end surface56side in the right-left direction that contact the end surface56in the right-left direction each have a sectoral frame shape. In the first preferred embodiment, the through-hole72ais provided on each of the plurality of (eight) first protrusions72.

The air guide70includes an annular recess74recessed away from the end surface56with respect to the plurality of first protrusions72on the outer peripheral side of the plurality of first protrusions72. The annular recess74is connected to the outer peripheral side flow passage81. The annular recess74is recessed away from the end surface56by the same amount as the inside-outside connection recesses73.

The air guide70includes a first annular recess75recessed away from the end surface56with respect to the plurality of first protrusions72on the inner peripheral side on which the piston rod52is provided. The first annular recess75connects the inside-outside connection recesses73to the oil passage connection port55. The first annular recess75is largely recessed away from the end surface56relative to the inside-outside connection recesses73.

As shown inFIG. 6, in the first preferred embodiment, the air guide70moves to the contact position P1in the right-left direction due to the flow of the hydraulic oil discharged from the oil chamber51to the oil passage connection port55when the hydraulic oil is discharged from the oil chamber51, and moves to the separated position P2in the right-left direction due to the flow of the hydraulic oil supplied from the oil passage connection port55to the oil chamber51when the hydraulic oil is supplied to the oil chamber51. Specifically, the air guide70is moved toward the contact position P1due to the flow of the hydraulic oil discharged from the left oil chamber51a(oil chamber51) to move in the right-left direction from the separated position P2to the contact position P1when the hydraulic oil is discharged from the left oil chamber51a(oil chamber51) to the oil passage42a(oil passage42) via the oil passage connection port55a(oil passage connection port55). Furthermore, the air guide70is moved toward the separated position P2due to the flow of the hydraulic oil supplied to the right oil chamber51b(oil chamber51) to move in the right-left direction from the contact position P1to the separated position P2when the hydraulic oil is supplied from the oil passage42b(oil passage42) to the right oil chamber51b(oil chamber51) via the oil passage connection port55b(oil passage connection port55).

In the first preferred embodiment, the outboard motors120each include a restrictor52bto restrict the air guide70from moving to the side opposite to the contact position P1relative to the separated position P2in the right-left direction. Specifically, the restrictor52bhas a stepped shape that protrudes toward the outer peripheral side relative to the oil passage connection port55and is provided at the end of the piston rod52on the oil passage connection port55side. Thus, the moving range of the air guide70is limited between the contact position P1and the separated position P2in the right-left direction.

According to the first preferred embodiment of the present invention, the following advantageous effects are achieved.

According to the first preferred embodiment of the present invention, the outboard motors120(marine vessel100) each include the air guide70located in the vicinity of or adjacent to the oil passage connection port55, which is the connection port of the oil chamber51to the oil passage42, in the right-left direction to guide the air60remaining in the oil chamber51to the oil passage connection port55when the hydraulic oil is discharged from the oil chamber51via the oil passage42. Accordingly, when the hydraulic oil is discharged from the oil chamber51via the oil passage42, the air guide70guides the air60remaining in the oil chamber51to the oil passage connection port55. That is, the air60remaining in the oil chamber51is guided to the oil passage connection port55by the normal operation of the steering cylinder41that discharges the hydraulic oil from the oil chamber51via the oil passage42, and thus the air60is automatically discharged from the oil chamber51to the outside without an operator performing a complex operation such as tilting the steering cylinder41. Consequently, the air in the oil chamber51of the steering cylinder41is easily bled. Furthermore, the air is bled at any time only by the user of the marine vessel100performing a steering operation (to change the propulsion direction of the marine vessel100) while maneuvering the marine vessel100, without the operator performing an air bleeding operation.

According to the first preferred embodiment of the present invention, the air guide70guides the air60remaining in the upper portion of the oil chamber51to the oil passage connection port55via the outer peripheral side flow passage81provided on the outer peripheral side of the air guide70when the hydraulic oil is discharged from the oil chamber51. Accordingly, the upper portion (outer peripheral side) of the oil chamber51is closer to the outer peripheral side flow passage81than the inner peripheral side of the oil chamber51, and the air60is lower in viscosity than the hydraulic oil, and thus when the hydraulic oil is discharged from the oil chamber51via the oil passage42, the air60remaining in the upper portion (outer peripheral side) of the oil chamber51is preferentially discharged to the outside from the oil chamber51via the outer peripheral side flow passage81. Consequently, when the hydraulic oil is discharged from the oil chamber51via the oil passage42, the air guide70reliably guides the air60remaining in the upper portion of the oil chamber51to the oil passage connection port55.

According to the first preferred embodiment of the present invention, the air guide70has a disk shape. Furthermore, the outer peripheral side flow passage81is defined by the outer peripheral surface70aof the disk-shaped air guide70and the inner peripheral surface51cof the oil chamber51. Accordingly, with the disk-shaped air guide70, the outer peripheral side flow passage81that guides the air60remaining in the upper portion (outer peripheral side) of the oil chamber51to the oil passage connection port55is easily provided on the outer peripheral side of the air guide70.

According to the first preferred embodiment of the present invention, the air guide70supplies the hydraulic oil to the oil chamber51via the inner peripheral side flow passage82provided on the inner peripheral side of the outer peripheral side flow passage81in addition to the outer peripheral side flow passage81when the hydraulic oil is supplied to the oil chamber51. Accordingly, when the hydraulic oil is supplied to the oil chamber51, the sectional area of a flow passage through which the hydraulic oil is supplied is increased as compared with a case in which the flow passage through which the hydraulic oil is supplied is limited to the outer peripheral side flow passage81. Consequently, the pressure loss of the hydraulic oil is decreased when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the air guide70moves in the right-left direction in the oil chamber51to close the inner peripheral side flow passage82when the hydraulic oil is discharged from the oil chamber51and to open the inner peripheral side flow passage82when the hydraulic oil is supplied to the oil chamber51. Accordingly, the air guide70is moved in the right-left direction in the oil chamber51such that the outer peripheral side flow passage81is easily provided when the hydraulic oil is discharged from the oil chamber51, and the outer peripheral side flow passage81and the inner peripheral side flow passage82are easily provided when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the air guide70includes the contact portion71that contacts the end surface56in the right-left direction in the oil chamber51. Furthermore, the air guide70moves in the right-left direction to the contact position P1at which the contact portion71contacts the end surface56to close the inner peripheral side flow passage82when the hydraulic oil is discharged from the oil chamber51, and moves in the right-left direction to the separated position P2at which the contact portion71is spaced apart from the end surface56to open the inner peripheral side flow passage82when the hydraulic oil is supplied to the oil chamber51. Accordingly, the air guide70is moved in the right-left direction between the contact position P1and the separated position P2in the oil chamber51such that the inner peripheral side flow passage82is easily closed when the hydraulic oil is discharged from the oil chamber51, and the inner peripheral side flow passage82is easily opened when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the air guide70moves to the contact position P1in the right-left direction due to the flow of the hydraulic oil discharged from the oil chamber51to the oil passage connection port55when the hydraulic oil is discharged from the oil chamber51, and moves to the separated position P2in the right-left direction due to the flow of the hydraulic oil supplied from the oil passage connection port55to the oil chamber51when the hydraulic oil is supplied to the oil chamber51. Accordingly, the air guide70is moved to the contact position P1in the right-left direction through the normal operation of the steering cylinder41that discharges the hydraulic oil from the oil chamber51, and the air guide70is moved to the separated position P2in the right-left direction through the normal operation of the steering cylinder41that supplies the hydraulic oil to the oil passage42, and thus the air guide70is moved in the right-left direction to the contact position P1and the separated position P2in the oil chamber51without separately providing a dedicated movement mechanism to move the air guide70.

According to the first preferred embodiment of the present invention, the outboard motors120(marine vessel100) each include the restrictor52bto restrict the air guide70from moving to the side opposite to the contact position P1relative to the separated position P2in the right-left direction. Accordingly, the moving range of the air guide70is limited between the contact position P1and the separated position P2in the right-left direction by the restrictor52b, and thus an excessive increase in the moving range of the air guide70is significantly reduced or prevented.

According to the first preferred embodiment of the present invention, the oil passage connection port55is located in the vicinity of or adjacent to the end surface56in the right-left direction. Accordingly, the separated position P2is located relatively close to the end surface56in the right-left direction, and thus an excessive increase in the moving range of the air guide70is significantly reduced or prevented.

According to the first preferred embodiment of the present invention, the oil passage42is provided in the piston rod52. Furthermore, the oil passage connection port55is provided on the outer peripheral surface52aof the piston rod52provided in the cylinder body54. Moreover, the piston rod52is provided on the inner peripheral side of the oil chamber51, and the air guide70includes, as the contact portion71, the plurality of first protrusions72that protrude toward the end surface56in the right-left direction, and the inside-outside connection recesses73located between the plurality of first protrusions72to connect the outer peripheral side of the oil chamber51to the inner peripheral side. Accordingly, the plurality of first protrusions72corresponding to the contact portion71easily close the inner peripheral side flow passage82when the hydraulic oil is discharged from the oil chamber51, and easily open the inner peripheral side flow passage82when the hydraulic oil is supplied to the oil chamber51. Furthermore, the inside-outside connection recesses73easily connect, on the end surface56side of the air guide70, the outer peripheral side flow passage81to the oil passage connection port55provided on the outer peripheral surface52aof the piston rod52on the inner peripheral side when the hydraulic oil is discharged from the oil chamber51, and easily connect, on the end surface56side of the air guide70, the outer peripheral side flow passage81and the inner peripheral side flow passage82to the oil passage connection port55when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the air guide70includes, as the inner peripheral side flow passage82, the through-hole72aprovided on at least one of the plurality of first protrusions72to penetrate therethrough in the right-left direction. Accordingly, with the through-hole72a, the inner peripheral side flow passage82, which is closed due to contact of the plurality of first protrusions72with the end surface56in the right-left direction when the hydraulic oil is discharged from the oil chamber51, and is opened due to being spaced apart from the plurality of first protrusions72from the end surface56in the right-left direction when the hydraulic oil is supplied to the oil chamber51, is easily provided.

According to the first preferred embodiment of the present invention, the through-hole72ais provided on each of the plurality of first protrusions72. Accordingly, the sectional area of the inner peripheral side flow passage82is easily increased as compared with a case in which the through-hole72ais provided on one or more but not all of the plurality of first protrusions72. Consequently, the pressure loss of the hydraulic oil is effectively decreased when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the plurality of first protrusions72each have a sectoral shape as viewed in the right-left direction, and the through-hole72ahas a sectoral shape smaller than the sectoral shape of each of the plurality of first protrusions72as viewed in the right-left direction. Accordingly, the sectional area of the inner peripheral side flow passage82is easily increased as compared with a case in which the through-hole72adoes not have the same sectoral shape as the plurality of first protrusions72. Consequently, the pressure loss of the hydraulic oil is effectively decreased when the hydraulic oil is supplied to the oil chamber51.

According to the first preferred embodiment of the present invention, the oil passage connection port55is provided on a portion of the outer peripheral surface52aof the piston rod52in the circumferential direction. Furthermore, the air guide70includes the first annular recess75recessed away from the end surface56with respect to the plurality of first protrusions72on the inner peripheral side, on which the piston rod52is provided, to connect the inside-outside connection recesses73to the oil passage connection port55. Accordingly, the inside-outside connection recesses73that connect the outer peripheral side to the inner peripheral side with the piston rod52are easily connected to the oil passage connection port55provided on a portion of the outer peripheral surface52aof the piston rod52in the circumferential direction by the first annular recess75.

Second Preferred Embodiment

The structure of a marine vessel200including outboard motors220(two outboard motors, for example) according to a second preferred embodiment of the present invention is now described with reference toFIGS. 9 and 11. In the figures, the same or similar structures as those of the outboard motors120and the marine vessel100according to the first preferred embodiment are denoted by the same reference numerals.

As shown inFIG. 9, in the second preferred embodiment, an oil passage242is located in front of a steering cylinder241, unlike the first preferred embodiment in which the oil passage42is provided inside the piston rod52. Specifically, in front of an oil chamber251, the oil passage242including a first end connected to oil pipes245and a second end connected to the oil chamber251is aligned with the steering cylinder241in a forward-rearward direction and extends in a right-left direction. The oil passage242includes an oil passage242aconnected to a left oil chamber251aand an oil passage242bconnected to a right oil chamber251b. The oil passage242ais connected to the left oil chamber251aon the left end cap257side of the steering cylinder241and is connected to one of the oil pipes245on the piston253side of the steering cylinder241. Furthermore, the oil passage242bis connected to the right oil chamber251bon the right end cap257side of the steering cylinder241and is connected to the other of the oil pipes245on the piston253side of the steering cylinder241.FIG. 9shows a state in which hydraulic oil is supplied from the oil passage242ato the left oil chamber251avia an oil passage connection port255a, and hydraulic oil is discharged from the right oil chamber251bto the oil passage242bvia an oil passage connection port255b. InFIG. 9, the hatching of an air guide270indicating a cross-section is omitted in order to clearly show the shape of the air guide270.

In the second preferred embodiment, an oil passage connection port255, which is a connection port of the oil chamber251to the oil passage242, is provided on a portion of the inner peripheral surface254aof a cylinder body254(the inner peripheral surface251cof the oil chamber251) in a circumferential direction, unlike the first preferred embodiment in which the oil passage connection port55is located in a portion of the outer peripheral surface52aof the piston rod52provided in the cylinder body54in the circumferential direction. Specifically, the oil passage connection port255aof the oil passage242aconnected to the left oil chamber251aextends from the oil passage242ato an end (inner peripheral surface251c) of the left oil chamber251aon the oil passage242aside toward the inner circumference side inside an outer peripheral portion (having a tubular shape) of the cylinder body254. The oil passage connection port255bof the oil passage242bconnected to the right oil chamber251bextends from the oil passage242bto an end (inner peripheral surface251c) of the right oil chamber251bon the oil passage242bside toward the inner circumference side inside the outer peripheral portion of the cylinder body254.

In the second preferred embodiment, the oil passage connection port255is located in the vicinity of or adjacent to an end surface256(on the side opposite to the piston253side) of the oil chamber251in the right-left direction, unlike the first preferred embodiment in which the oil passage connection port55is located in the vicinity of or adjacent to the end surface56(on the piston53side) of the oil chamber51in the right-left direction.

In the second preferred embodiment, the outboard motors220each include the air guide270located in the vicinity of or adjacent to the oil passage connection port255to guide air60(seeFIG. 10) remaining in the oil chamber251to the oil passage connection port255when the hydraulic oil is discharged from the oil chamber251via the oil passage242, similarly to the first preferred embodiment. As shown inFIG. 10, the air60remains in the oil chamber251without being discharged from the oil passage connection port255after the air60enters the oil chamber251when the steering cylinder241is assembled, similarly to the first preferred embodiment.

As shown inFIG. 11, in the second preferred embodiment, the air guide270includes, as a contact portion271, a second protrusion272that protrudes toward the end surface256(seeFIG. 6) of the oil chamber251, unlike the first preferred embodiment in which the air guide70includes the plurality of (eight) first protrusions72as the contact portion71and the inside-outside connection recesses73located between the plurality of (eight) first protrusions72. That is, as shown inFIG. 9, when the hydraulic oil is discharged from the right oil chamber251b(oil chamber251) to the oil passage242b(oil passage242) via the oil passage connection port255b(oil passage connection port255), a surface272bof the second protrusion272on the end surface256side in the right-left direction contacts the end surface256in the right-left direction. In this state, an inner peripheral side flow passage282is closed.

In the second preferred embodiment, the inner peripheral side flow passage282is an annular gap between the outer peripheral surface252aof a piston rod252and the inner peripheral surface273aof a through-hole273that penetrates in the right-left direction in a central portion of the air guide270, unlike the first preferred embodiment in which the through-hole72ais provided as the inner peripheral side flow passage82on at least one of the first protrusions72to penetrate therethrough in the right-left direction. The width of the annular gap between the outer peripheral surface252aand the inner peripheral surface273ais set to several millimeters, for example.

In the second preferred embodiment, the air guide270includes notches276as the outer peripheral flow passage281, unlike the first preferred embodiment in which the annular gap is provided as the outer peripheral side flow passage81between the outer peripheral surface70aof the disk-shaped air guide70and the inner peripheral surface51cof the oil chamber51. The notches276are provided on the outer peripheral side to penetrate in the right-left direction. The notches276are portions of the outer peripheral surface270aof the air guide270. A plurality of (eight, for example) of notches276aare provided at equal or substantially equal intervals as viewed in the axial direction (right-left direction) of the piston rod252. The diameter of a portion of the outer peripheral surface270aof the air guide270without the notches is slightly smaller than the diameter of the inner peripheral surface254aof the cylinder body254within a predetermined range (at a contact position P1and a separated position P2). Thus, the air guide270moves within the predetermined range in the oil chamber251while being guided by the inner peripheral surface254aof the cylinder body254.

In the second preferred embodiment, the air guide270includes a second annular recess275. The second annular recess275is recessed away from the end surface256with respect to the second protrusion272on the outer peripheral side and is connected to the oil passage connection port255.

In the second preferred embodiment, a restrictor254bhas a stepped shape that is recessed to the outer peripheral side as compared with the inner peripheral surface254aon the piston253side and is located in the vicinity of or adjacent to the oil passage connection port255of the inner peripheral surface254aof the cylinder body254, unlike the first preferred embodiment in which the restrictor52bthat protrudes toward the outer peripheral side relative to the oil passage connection port55is provided at the end of the piston rod52on the oil passage connection port55side.

The remaining structures of the second preferred embodiment are similar to those of the first preferred embodiment.

According to the second preferred embodiment of the present invention, the following advantageous effects are achieved.

According to the second preferred embodiment of the present invention, the outboard motors220(marine vessel200) each include the air guide270located in the vicinity of or adjacent to the oil passage connection port255, which is the connection port of the oil chamber251to the oil passage242, in the right-left direction to guide the air60remaining in the oil chamber251to the oil passage connection port255when the hydraulic oil is discharged from the oil chamber251via the oil passage242. Accordingly, similarly to the first preferred embodiment, the air60remaining in the oil chamber251is guided to the oil passage connection port255by the normal operation of the steering cylinder241that discharges the hydraulic oil from the oil chamber251via the oil passage242, and thus the air60is automatically discharged from the oil chamber251to the outside without an operator performing a complex operation such as tilting the steering cylinder241. Consequently, similarly to the first preferred embodiment, the air in the oil chamber251of the steering cylinder241is easily bled.

According to the second preferred embodiment of the present invention, the oil passage242is located in front of the steering cylinder241. Furthermore, the oil passage connection port255is provided on the inner peripheral surface254aof the cylinder body254. Moreover, the air guide270includes, as the contact portion271, the second protrusion272that protrudes toward the end surface256of the oil chamber251. Accordingly, the second protrusion272corresponding to the contact portion271easily closes the inner peripheral side flow passage282when the hydraulic oil is discharged from the oil chamber251, and easily opens the inner peripheral side flow passage282when the hydraulic oil is supplied to the oil chamber251.

According to the second preferred embodiment of the present invention, the air guide270includes, as the outer peripheral side flow passage281, the notches276provided on the outer peripheral side to penetrate in the right-left direction. Accordingly, with the notches276, the outer peripheral side flow passage281is easily provided in the oil chamber251when the hydraulic oil is discharged from the oil chamber251.

According to the second preferred embodiment of the present invention, the oil passage connection port255is provided on a portion of the inner peripheral surface254aof the cylinder body254in the circumferential direction. Furthermore, the air guide270includes the second annular recess275recessed away from the end surface256with respect to the second protrusion272on the outer peripheral side and is connected to the oil passage connection port255. Accordingly, the outer peripheral side flow passage281is easily connected to the oil passage connection port255provided on a portion of the inner peripheral surface254aof the cylinder body254in the circumferential direction by the second annular recess275.

The remaining advantageous effects of the second preferred embodiment are similar to those of the first preferred embodiment.

The preferred embodiments of the present invention described above are illustrative in all points and not restrictive. The extent of the present invention is not defined by the above description of the preferred embodiments but by the scope of the claims, and all modifications within the meaning and range equivalent to the scope of the claims are further included.

For example, while the marine vessel preferably includes two outboard motors in each of the first and second preferred embodiments described above, the present invention is not restricted to this. In the present invention, the marine vessel may alternatively include one or three or more outboard motors.

While the oil passage242is preferably located in front of the steering cylinder241in the second preferred embodiment described above, the present invention is not restricted to this. In the present invention, the oil passage may alternatively be provided behind the steering cylinder or below the steering cylinder.

While the through-hole72acorresponding to the inner peripheral side flow passage82is preferably provided on each of the plurality of first protrusions72corresponding to the contact portion71in the first preferred embodiment described above, the present invention is not restricted to this. In the present invention, as in an air guide370according to a first modified example shown inFIG. 12, a through-hole372acorresponding to an inner peripheral side flow passage382may alternatively be provided only on one or more but not all of the plurality of first protrusions372corresponding to the contact portion371.

While each of the plurality of first protrusions72preferably has a sectoral shape as viewed in the right-left direction, and the through-hole72acorresponding to the inner peripheral side flow passage82preferably has a sectoral shape smaller than the sectoral shape of each of the plurality of first protrusions72as viewed in the right-left direction in the first preferred embodiment described above, the present invention is not restricted to this. In the present invention, as in the air guide370according to the first modified example shown inFIG. 12, each of the plurality of first protrusions372may alternatively have a sectoral shape as viewed in the right-left direction, and the through-hole372acorresponding to the inner peripheral side flow passage382may alternatively have a shape other than the sectoral shape as viewed in the right-left direction. Furthermore, although not shown, each of the plurality of first protrusions may alternatively have a shape other than the sectoral shape as viewed in the right-left direction.

While the air guide70preferably includes the annular recess74recessed away from the end surface56with respect to the plurality of first protrusions72on the outer peripheral side of the plurality of first protrusions72and connected to the outer peripheral side flow passage81in the first preferred embodiment described above, the present invention is not restricted to this. In the present invention, the air guide may not include the annular recess recessed away from the end surface with respect to the plurality of first protrusions on the outer peripheral side of the plurality of first protrusions and connected to the outer peripheral side flow passage.

While the plurality of oil passage connection ports55are preferably provided at equal or substantially equal intervals in the circumferential direction on the outer peripheral surface52aof the piston rod52in the first preferred embodiment described above, the present invention is not restricted to this. In the present invention, the plurality of oil passage connection ports may alternatively be provided at non-uniform intervals in the circumferential direction on the outer peripheral surface of the piston rod. Furthermore, only one oil passage connection port may alternatively be provided in the circumferential direction on the outer peripheral surface of the piston rod.

While the air guide270preferably includes, as the outer peripheral flow passage281, the notches276provided on the outer peripheral side to penetrate in the right-left direction in the second preferred embodiment described above, the present invention is not restricted to this. In the present invention, as in an air guide470according to a second modified example shown inFIG. 13, the air guide according to the first preferred embodiment may alternatively include notches as an outer peripheral side flow passage, or as in an air guide570according to a third modified example shown inFIG. 14, the air guide according to the first modified example may alternatively include notches as an outer peripheral side flow passage.

While the air guide70(270) preferably supplies the hydraulic oil to the oil chamber51(251) via the inner peripheral side flow passage82(282) in addition to the outer peripheral side flow passage81(281) when the hydraulic oil is supplied to the oil chamber51(251) in each of the first and second preferred embodiments described above, the present invention is not restricted to this. In the present invention, the air guide may alternatively supply the hydraulic oil to the oil chamber not via the inner peripheral side flow passage but via the outer peripheral side flow passage when the hydraulic oil is supplied to the oil chamber.

While an electric signal is preferably transmitted from the steering wheel111to the steering control unit provided in each of the outboard motors120(220) as the user operates the steering wheel111, the steering control unit preferably controls the steering motor46bof the steering device40provided in each of the outboard motors120(220) to change the propulsion direction of the hull110(210) based on the electric signal transmitted from the steering wheel111, and the steering pump46aprovided in each of the outboard motors120(220) is preferably driven by the control of the steering motor46bto supply the hydraulic oil from the steering pump46ato the oil chamber51(251) and discharge the hydraulic oil from the oil chamber51(251) to the outside in each of the first and second preferred embodiments described above, the present invention is not restricted to this. In the present invention, as the user operates the steering wheel, a mechanical steering pump provided in the hull may alternatively be driven to supply the hydraulic oil to the oil chamber of the steering cylinder provided in each of the outboard motors and discharge the hydraulic oil from the oil chamber.