Patent Description:
In particular, an outboard motor, which including a discharge passage for guiding exhaust gas from an engine, is disclosed in <CIT>. Such kind of outboard motor includes the engine, the drive shaft, the propeller shaft, the housing, cooling water passage, a first passage, a second passage, and a valve structure. The first passage is disposed on the upstream side of a discharge chamber and guides an exhaust gas from the engine toward the discharge chamber. A second passage is disposed on the downstream side of the discharge chamber and exhausts the exhaust gas and water of the discharge chamber. The second passage can guide water, which enters in the housing, toward the discharge chamber. The valve structure is one-way valve and permits passage of the exhaust gas pass at the first connection by water pressure of a cooling water passage. The cooling water passage is a passage which is different from the first passage and the second passage. In this type of outboard motor, generally, an exhaust hollow for discharging the above exhaust gas from the discharge passage to the outside is provided on a housing of the outboard motor.

In the conventional outboard motor, the exhaust gas, which is discharged from the engine, is discharged from the inside of the outboard motor to the outside of the outboard motor via the exhaust hollow. In this case, fuel, which is contained in the exhaust gas discharged from the exhaust hollow, may adhere to an outer surface around the exhaust hollow of the housing and discolor the outer surface of the housing. The discoloration often occurs when a watercraft moves forward.

An object of the present invention is to provide an outboard motor which is capable of suppressing discoloration around an exhaust hollow. According to the present invention said object is solved by an outboard motor having the features of independent claim <NUM>. Preferred embodiments are laid down in the dependent claims.

The outboard motor according to one aspect includes an engine, a drive shaft, a propeller shaft, a propeller, a housing, a first passage, a second passage, and a valve structure. The drive shaft extends from the engine in a first direction. The propeller shaft extends in a second direction intersecting with the drive shaft.

The propeller is connected to the propeller shaft. The propeller is configured to generate a forward propulsive force in a forward direction along the second direction and configured to generate a backward propulsive force in a backward direction along the second direction.

The housing is configured to accommodate the engine, the drive shaft, and the propeller shaft. The housing forms a discharge chamber. The discharge chamber is configured to discharge exhaust gas of the engine.

The first passage is configured to guide the exhaust gas from the engine to the discharge chamber inside the housing. The second passage is configured to guide water to the discharge chamber. The outboard motor is configured such that the water enters the housing when a forward propulsive force is generated.

The valve structure is configured to regulate or permit passage of the exhaust gas at a first connection by exhaust pressure and water pressure. The first connection connects the first passage and the discharge chamber. The outboard motor is configured such that the exhaust pressure acts from the first passage toward the discharge chamber. The water pressure acts from the second passage toward the discharge chamber.

The valve structure is configured to regulate the passage of the exhaust gas at the first connection by the water pressure, when the forward propulsive force is generated. The valve structure is configured to permit the passage of the exhaust gas at the first connection by the exhaust pressure, when the backward propulsive force is generated.

In the present invention, an outboard motor is capable of suppressing discoloration around an exhaust hollow.

The following embodiments will be described with reference to the drawings. As shown in <FIG>, the watercraft <NUM> includes a hull <NUM> and an outboard motor <NUM>. In this embodiment, an example, in which the number of the outboard motor <NUM> is one, is described. The number of the outboard motor <NUM> may be plural.

In the following description, direction of each of front, rear, left, right, up, and down means direction of each of front, rear, left, right, up, and down of the hull <NUM>. For example, as shown in <FIG>, the center line C1 extending in a front-rear direction of the hull <NUM> passes through a center of gravity G of the hull <NUM>.

The front-back direction is a direction along the center line C1. The front is a direction toward an upper side along the center line C1 of <FIG>. The rear is a direction toward a downward side along the center line C1 of <FIG>. In this embodiment, the front-rear direction of the outboard motor <NUM> is defined by an attitude of the hull <NUM> (an attitude of <FIG>) when the outboard motor <NUM> moves the hull <NUM> in the front-rear direction. The left-right direction of <FIG> corresponds to the front-rear direction of the outboard motor <NUM>.

The left-right direction (a width direction) is a direction perpendicular to the center line C1 in FIG. A left side is a direction perpendicular to the center line C1 of <FIG> and the direction toward a left side. A right side is a direction perpendicular to the center line C1 of <FIG> and the direction toward the right side. A vertical direction is a direction perpendicular to the front-back direction and the left-right direction.

As shown in <FIG>, the outboard motor <NUM> generates a propulsive force for propelling the hull <NUM>. The outboard motor <NUM> is attached to a stern of the hull <NUM>. The outboard motor <NUM> includes an engine <NUM>, a drive shaft <NUM>, a propeller shaft <NUM>, and a housing <NUM>. The outboard motor <NUM> further includes a shift mechanism <NUM> and a bracket <NUM>. As shown in <FIG>, the outboard motor <NUM> further includes a discharge passage P, a water intake passage Q (an example of a second passage), and a valve structure <NUM> (see <FIG>).

The engine <NUM> is a power source that produces the propulsive force of the hull <NUM>. The engine <NUM> is disposed in an engine cover <NUM>. The engine <NUM> includes a crankshaft <NUM>. The crankshaft <NUM> extends in the vertical direction.

The engine <NUM> is connected to the drive shaft <NUM>. The drive shaft <NUM> extends in the vertical direction. For example, the drive shaft <NUM> extends downward (an example of a first direction) from the engine <NUM>. The propeller shaft <NUM> extends in a direction (an example of a second direction) intersecting the drive shaft <NUM>. In this embodiment, the propeller shaft <NUM> extends in the front-rear direction. The propeller shaft <NUM> is connected to the drive shaft <NUM> via the shift mechanism <NUM>. A propeller <NUM> is connected to the propeller shaft <NUM>.

The shift mechanism <NUM> is driven by a shift actuator <NUM> via the shift member <NUM>. The shift mechanism <NUM> switches a rotation direction of the power which is transmitted from the drive shaft <NUM> to the propeller shaft <NUM>. Thereby, the rotation direction of the propeller <NUM> is switched to a forward direction in which the hull <NUM> moves forward or a reverse direction in which the hull <NUM> moves backward.

The bracket <NUM> is used for attaching the outboard motor <NUM> to the hull <NUM>. The outboard motor <NUM> is detachably fixed to the stern of the watercraft <NUM> via the bracket <NUM>. The bracket <NUM> includes a steering shaft <NUM>. The outboard motor <NUM> is rotatably supported by the bracket <NUM> about the steering shaft <NUM>.

As shown in <FIG>, the housing <NUM> accommodates the engine <NUM>, the drive shaft <NUM>, and the propeller shaft <NUM>. Specifically, the housing <NUM> accommodates the engine <NUM>, the drive shaft <NUM>, the propeller shaft <NUM>, and the shift mechanism <NUM>.

As shown in <FIG>, the housing <NUM> includes a discharge portion <NUM>,<NUM> which discharges an exhaust gas of the engine <NUM>. Specifically, the housing <NUM> includes the engine cover <NUM>, a housing body <NUM>, and a pair of discharge portions <NUM>, <NUM>. In the following, when the reference numeral of one member of a pair of members is shown, the reference numeral of the other member of the pair of members is shown in the parentheses.

The engine cover <NUM> covers the engine <NUM>. The engine <NUM> is disposed inside the engine cover <NUM>. The engine cover <NUM> is a metal member. The engine cover <NUM> may be a resin member.

The housing body <NUM> is disposed below the engine cover <NUM>. The drive shaft <NUM>, the propeller shaft <NUM>, and the shift mechanism <NUM> are disposed inside the housing body <NUM>. The housing body <NUM> is a metal member. The housing body <NUM> may be a resin member.

A cavitation plate <NUM> is provided on the housing body <NUM>. For example, the cavitation plate <NUM> is provided on the housing body <NUM> above the propeller <NUM>. Specifically, the cavitation plate <NUM> is provided on the housing body <NUM> in the vertical direction between the propeller <NUM> and the engine <NUM>.

As shown in <FIG>, the housing body <NUM> includes a wall portion <NUM> which is used for forming the discharge passage P. For example, the wall portion <NUM> of the passage is integrally formed on the inner surface of the housing body <NUM>. The housing body <NUM> further includes both side portions 31a, <NUM> b which form a discharge chamber R described later.

The pair of discharge portions <NUM>, <NUM> discharge the exhaust gas and a cooling water which is discharged from the engine <NUM>. The pair of discharge portions <NUM>, <NUM> are provided on the housing <NUM>. For example, the pair of discharge portions <NUM>, <NUM> are provided on the housing body <NUM> between the engine <NUM> and the cavitation plate <NUM>.

The pair of discharge portions <NUM>, <NUM> are respectively provided on the both side portions 31a, 31b of the housing body <NUM>. For example, the pair of discharge portions <NUM>, <NUM> are respectively provided on the both side portions 31a, 31b of the housing body <NUM> so as to face each other in the width direction (left-right direction).

Each of the pair of discharge portions <NUM>, <NUM> is at least one hollow portion. The at least one hollow portion penetrates the housing body <NUM> from an inside of the housing body <NUM> toward an outside of the housing body <NUM>. For example, the at least one hollow portion penetrates each of the side portions 31a, 31b which forms the discharge chamber R. In this embodiment, an example is described in which each of the pair of discharge portions <NUM>, <NUM> includes a plurality of hollow portions, for example, three hollow portions, respectively.

As shown in <FIG>, the discharge passage P guides the exhaust gas and the cooling water from the engine <NUM> toward the pair of discharge portions <NUM>, <NUM> in the housing <NUM>. The discharge passage P is formed by the housing <NUM>. For example, the discharge passage P is formed by the housing body <NUM>. The discharge passage P is formed by the wall portion <NUM> of the passage.

The discharge passage P includes the discharge chamber R, an exhaust passage P1 (an example of a first passage), and a cooling water passage P2.

The discharge chamber R is a space which is used for discharging the exhaust gas of the engine <NUM>. In this embodiment, the discharge chamber R is a space which is used for guiding the exhaust and the cooling water toward the pair of discharge portions <NUM>, <NUM>. The discharge chamber R is a space which is provided in the housing body <NUM> to discharge the exhaust gas and the cooling water from the pair of discharge portions <NUM>, <NUM>.

The discharge chamber R is provided inside the housing body <NUM> between the engine <NUM> and the cavitation plate <NUM>. The discharge chamber R is formed by the housing body <NUM>.

For example, as shown in <FIG>, the discharge chamber R is formed by the both side portions 31a, 31b of the housing body <NUM> and wall portions 31c of the discharge chamber R. The wall portions 31c of the discharge chamber R are provided on the inner surfaces of the both side portions 31a, 31b. The both side portions 31a, 31b of the housing body <NUM> form side walls of the discharge chamber R.

The wall part 31c of the discharge chamber R includes a front wall 31c1 of the discharge chamber R, a rear wall 31c2 of the discharge chamber R, an upper wall 31c3 of the discharge chamber R, and a lower wall <NUM> c4 of the discharge chamber R. In <FIG>, the discharge passage P and the water intake passage Q are schematically shown.

In this embodiment, as shown in <FIG>, the housing body <NUM> includes an upper housing body <NUM> and a lower housing body <NUM>. The upper housing body <NUM> forms an upper portion of the housing body <NUM>. The upper housing body <NUM> forms the upper wall 31c3 of the discharge chamber R. The lower housing body <NUM> forms the lower part of the housing body <NUM>. The lower housing body <NUM> forms the front wall 31c1 of the discharge chamber R, the rear wall 31c2 of the discharge chamber R, and the lower wall 31c4 of the discharge chamber R.

As shown in <FIG>, the front wall 31c1 is provided between the exhaust passage P1 and the discharge chamber R. For example, the front wall 31c1 includes a first hollow portion 131c1 (an example of a first connection) which is used for passing the exhaust gas from the exhaust passage P1 to the discharge chamber R.

Exhaust pressure is generated by the exhaust gas which flows from the exhaust passage P1 toward the discharge chamber R. The exhaust pressure acts on the valve structure <NUM> (see <FIG>), for example, a first facing portion <NUM> of a valve body <NUM> via the first hollow portion 131c1. The first facing portion <NUM> of the valve body <NUM> is described later.

The rear wall 31c2 is provided between the water intake passage Q and the discharge chamber R. The rear wall 31c2 includes a second hollow portion 131c2 (an example of a second connection) which is used for passing water from the water intake passage Q to the discharge chamber R.

Water pressure is generated by the water which flows from the water intake passage Q toward the discharge chamber R
The water pressure acts on the valve structure <NUM> (see <FIG>), for example, a second facing portion <NUM> of the valve body <NUM> via the second hollow portion 131c2. The second facing portion <NUM> of the valve body <NUM> is described later.

The area of the second hollow portion 131c2 is smaller than the area of the first hollow portion 131c1. For example, the area of the second hollow portion 131c2 viewed from the water intake passage Q (from a rear side) is smaller than the area of the first hollow portion 131c1 viewed from the exhaust passage P1 (from a front side). The upper wall 31c3 and the lower wall 31c4 respectively form an upper surface and a lower surface of the discharge chamber R.

As shown in <FIG>, the exhaust passage P1 is provided inside the housing body <NUM>. The exhaust passage P1 guides the exhaust gas from the engine <NUM> toward the discharge chamber R. The exhaust passage P1 is connected to the discharge chamber R.

For example, the exhaust passage P1 is formed by wall portions 37a for the exhaust gas which is provided on the inner surface of the housing body <NUM>. The exhaust passage P1 is disposed in front of the discharge chamber R. The exhaust passage P1 extends downward (an example of a first direction) from the engine <NUM> and is connected to the discharge chamber R. The exhaust gas is discharged from the discharge chamber R to the outside of the housing body <NUM> via the discharge portions <NUM>, <NUM> (the plurality of hollow portions).

The exhaust passage P1 guides the exhaust gas to a rear portion of the propeller <NUM>. The exhaust passage P1 is connected to a space which is formed in a portion at which the housing <NUM> (the housing body <NUM>) supports the propeller <NUM>.

The cooling water passage P2 guides the cooling water, which is used for cooling the engine <NUM>, from the engine <NUM> toward the discharge chamber R. The cooling water passage P2 is connected to the discharge chamber R. For example, the cooling water passage P2 is formed by wall portions 37b for cooling water which are provided on the inner surface of the housing <NUM>. The cooling water passage P2 extends downward (an example of a first direction) from the engine <NUM> and is connected to the discharge chamber R. The cooling water is discharged from the discharge chamber R to the outside of the housing <NUM> through the discharge portions <NUM>, <NUM> (the plurality of hollow portions).

As shown in <FIG>, the water intake passage Q is provided inside the housing body <NUM>. The water intake passage Q guides the water from the outside of the outboard motor <NUM> toward the discharge chamber R. The water intake passage Q is connected to the discharge chamber R. The water intake passage Q is provided behind the discharge chamber R.

For example, as shown in <FIG>, the water intake passage Q is formed from a lower surface of the cavitation plate <NUM> toward the discharge chamber R. The water intake passage Q is formed by providing a space inside the housing body <NUM>. This space is formed by the housing body <NUM> and the wall part <NUM> which is provided on the inner surface of the housing body <NUM>.

As shown in <FIG>, the housing body <NUM> further includes a water intake portion <NUM>. The water intake portion <NUM> is provided to take water into the water intake passage Q when a forward propulsive force is generated. In this embodiment, the water intake portion <NUM> is mounted to the housing body <NUM> as a separate member. The water intake portion <NUM> may be formed integrally with the housing body <NUM>. The water intake portion <NUM> is provided behind the discharge chamber R. For example, the water intake portion <NUM> is provided on the lower surface of the cavitation plate <NUM>.

The water intake portion <NUM> includes an opening 36a. At least a part of the opening opens forward. In this embodiment, the entire opening 36a opens forward. The opening 36a takes the water into the water intake passage Q, when the forward propulsive force is generated. In other words, the water pressure acts from the front of the opening 36a toward the opening 36a, when the forward propulsive force is generated. Thereby, the pressure of water in the water intake passage Q rises.

As shown in <FIG>, <FIG>, and <FIG>, the valve structure <NUM> regulates or permits the passage of the exhaust gas at the front wall <NUM> c1 by the exhaust pressure and the water pressure. The exhaust pressure acts from the exhaust passage P1 toward the discharge chamber R. The water pressure acts from the water intake passage Q toward the discharge chamber R.

For example, as shown in <FIG>, the valve structure <NUM> regulates the passage of the exhaust gas at the front wall 31c1 by the water pressure, when the forward propulsive force is generated. Specifically, when the forward propulsive force is generated, the valve structure <NUM> closes the first hollow portion 131c1 of the front wall 31c1 by the water pressure, because the water pressure becomes larger than the exhaust pressure.

As shown in <FIG>, the valve structure <NUM> permits the passage of the exhaust gas at the front wall 31c1 by the exhaust pressure, when a backward propulsive force is generated. Specifically, when the backward propulsive force is generated, the valve structure <NUM> opens the first hollow portion 131c1 of the front wall 31c1 by the exhaust pressure, because the exhaust pressure becomes larger than the water pressure.

Specifically, as shown in <FIG>, <FIG>, and <FIG>, the valve structure <NUM> includes the valve body <NUM> and a guide member <NUM> (an example of a support member). The valve body <NUM> is disposed inside the discharge chamber R. The valve body <NUM> moves inside the discharge chamber R. For example, the valve body <NUM> moves inside the discharge chamber R in the front-rear direction. The valve body <NUM> includes the first facing portion <NUM>, the second facing portion <NUM>, and a connecting portion <NUM>.

As shown in <FIG> and <FIG>, the first facing portion <NUM> is disposed behind the front wall 31c1 so as to face the front wall 31c1. Specifically, the first facing portion <NUM> is disposed behind the front wall 31c1 so as to face the first hollow portion 131c1. The first facing portion <NUM> includes a hollow portion 45a for the guide member.

The second facing portion <NUM> is disposed behind the first facing portion <NUM> so as to face the first facing portion <NUM>. The second facing portion <NUM> is disposed in front of the rear wall 31c2 so as to face the rear wall 31c2. Specifically, the second facing portion <NUM> is disposed in front of the rear wall 31c2 so as to face the second hollow portion 131c2. The second facing portion <NUM> includes a hollow portion 46a for the guide member.

A distance between the outer surface 45b of the first facing portion <NUM> and the outer surface 46b of the second facing portion <NUM> (the distance in the front-rear direction) is smaller than a distance between the front wall 31c1 and the rear wall 31c2 (the distance in the front-rear direction).

The connecting portion <NUM> connects the first facing portion <NUM> and the second facing portion <NUM>. The connecting portion <NUM> is disposed below the guide member <NUM>. The first facing portion <NUM>, the second facing portion <NUM>, and the connecting portion <NUM> are integrally formed with each other.

As shown in <FIG>, <FIG>, and <FIG>, the guide member <NUM> supports the valve body <NUM> so that the valve body <NUM> moves inside the discharge chamber R. For example, the guide member <NUM> supports the valve body <NUM> so that the valve body <NUM> moves in the front-rear direction inside the discharge chamber R.

The guide member <NUM> is provided on the housing body <NUM>. For example, the guide member <NUM> is a rod-shaped member. The guide member <NUM> extends in the front-rear direction at an upper portion of the discharge chamber R. The guide member <NUM> is inserted into the hollow portions 45a, 46a for the guide member of the first facing portion <NUM> and the second facing portion <NUM>. In this state, the guide member <NUM> is held by the front wall 31c1 of the housing body <NUM> and the rear wall 31c2 of the housing body <NUM>. A pipe for supplying the cooling water to the propeller <NUM> may be used as the guide member <NUM>.

As shown in <FIG>, when the forward propulsive force is generated, the valve body <NUM> moves toward the front wall 31c1 by water pressure and closes the first hollow portion 131c1 of the front wall 31c1. For example, when the forward propulsive force is generated, the water pressure acting on the second facing portion <NUM> of the valve body <NUM> becomes larger than the exhaust pressure acting on the first facing portion <NUM> of the valve body <NUM>. Thereby, the valve body <NUM> moves forward along the guide member <NUM> and closes the first hollow portion 131c1 of the front wall 31c1.

As shown in <FIG>, when the backward propulsive force is generated, the valve body <NUM> separates from the front wall 31c1 by the exhaust pressure and opens the first hollow portion 131c1. For example, when the backward propulsive force is generated, the exhaust pressure acting on the first facing portion <NUM> of the valve body <NUM> becomes larger than the water pressure acting on the second facing portion <NUM> of the valve body <NUM>. Thereby, the valve body <NUM> moves backward along the guide member <NUM> and opens the first hollow portion 131c1 of the front wall 31c1.

With the outboard motor <NUM> including the above configuration, the valve structure <NUM> regulates or permits the passage of exhaust gas at the first hollow portion 131c1 connecting the exhaust passage P1 and the discharge chamber R.

For example, when the forward propulsive force is generated, the valve structure <NUM> regulates the passage of the exhaust gas at the first hollow portion 131c1 by the water pressure. In this case, discoloration around the discharge portions <NUM>, <NUM> can be suppressed, because the exhaust gas is not discharged from the discharge portions <NUM>, <NUM>.

When the backward propulsive force is generated, the valve structure <NUM> permits the passage of the exhaust gas at the first hollow portion 131c1 by the exhaust pressure. In this case, the backward propulsive force can be improved, because the exhaust gas is discharged from the discharge portions <NUM>, <NUM>.

With the outboard motor <NUM>, the exhaust passage P1 is disposed in front of the discharge chamber R. The water intake passage Q is disposed behind the discharge chamber R. Thereby, the exhaust gas can be suitably regulated or permitted.

With the outboard motor <NUM>, the water can be suitably taken into the water intake passage Q, because at least a part of the opening 36a of the water intake portion <NUM> is opened toward the front.

With the outboard motor <NUM>, a discharge regulation of the exhaust gas and a discharge permission of the exhaust gas can be suitably realized in the valve structure <NUM> by moving the valve main body <NUM> inside the discharge chamber R.

With the outboard motor <NUM>, the valve main body <NUM> includes the first facing portion <NUM>, the second facing portion <NUM>, and the connecting portion <NUM>. By configuring the valve body <NUM> in this way, the discharge regulation of the exhaust gas and the discharge permission of the exhaust gas can be suitably realized in the valve structure <NUM>.

With the outboard motor <NUM>, the valve main body <NUM> can be suitably moved inside the discharge chamber R by making the area of the first hollow portion 131c1 larger than the area of the second hollow portion 131c2.

The configuration of the second embodiment is the substantially same as the configuration of the first embodiment except for the valve structure <NUM>. Thereby, the description of the substantially same configuration as one of the first embodiment is omitted in the second embodiment. The configuration omitted here conforms to the configuration of the first embodiment.

As shown in <FIG>, <FIG>, and <FIG>, the valve structure <NUM> regulates or permits the passage of the exhaust gas at the front wall 31c1 by the exhaust pressure and the water pressure. The exhaust pressure acts from the exhaust passage P1 toward the discharge chamber R. The water pressure acts from the water intake passage Q toward the discharge chamber R.

For example, as shown in <FIG>, the valve structure <NUM> regulates the passage of the exhaust gas at the front wall 31c1 by the water pressure, when the forward propulsive force is generated. Specifically, when the forward propulsive force is generated, the valve structure <NUM> closes by the water pressure, because the water pressure becomes larger than the exhaust pressure.

As shown in <FIG>, the valve structure <NUM> permits the passage of the exhaust gas at the front wall 31c1 by the exhaust pressure, when the backward propulsive force is generated. Specifically, when the backward propulsive force is generated, the valve structure <NUM> opens by the exhaust pressure, because the exhaust pressure becomes larger than the water pressure.

Specifically, as shown in <FIG>, <FIG>, and <FIG>, the valve structure <NUM> includes a frame member <NUM> (an example of a support member), a valve body <NUM>, and a pipe member <NUM> (an example of a guide member).

As shown in <FIG> and <FIG>, the frame member <NUM> configures a third hollow portion 59a (described later). The third hollow portion 59a connects the exhaust passage P1 and the discharge chamber R. For example, the frame member <NUM> configures the front wall 31c1 of the discharge chamber R. The frame member <NUM> may configure the entire front wall 31c1 of the discharge chamber R, or may configure a part of the front wall 31c1 of the discharge chamber R.

The frame member <NUM> supports the valve body <NUM>. For example, the frame member <NUM> includes a first frame member <NUM> and a second frame member <NUM>. The first frame member <NUM> is mounted to the housing body <NUM>. The second frame member <NUM> supports the valve body <NUM>. The second frame member <NUM> is detachably mounted to the first frame member <NUM>. The second frame member <NUM> includes the third hollow portion 59a (an example of the first connection).

The valve body <NUM> is configured to open and close the third hollow portion 59a. The valve body <NUM> is a member that is deformed toward a discharge chamber R side by the exhaust pressure. For example, the valve body <NUM> is an elastic member. The valve body <NUM> may be a metal elastic member or a non-metal elastic member.

As shown in <FIG> and <FIG>, the valve body <NUM> is mounted to the frame member <NUM>. For example, the valve body <NUM> is mounted to a surface of the discharge chamber R side of the frame member <NUM>. Specifically, the valve main body <NUM> is mounted to the surface of the discharge chamber R side of the second frame member <NUM> so as to cover the third hollow portion 59a.

In this state, the valve body <NUM> can be detached from the first frame member <NUM> together with the second frame member <NUM>. The valve body <NUM> can be attached to the first frame member <NUM> together with the second frame member <NUM>.

As shown in <FIG> and <FIG>, the pipe member <NUM> guides the water from the water intake passage Q toward the valve body <NUM>. The pipe member <NUM> is supported by the rear wall 31c2. One end of the pipe member <NUM> is disposed in the water intake passage Q. The other end of the pipe member <NUM> is disposed in the discharge chamber R.

As shown in <FIG>, the valve body <NUM> covers the third hollow portion 59a of the frame member <NUM> by water pressure, when the forward propulsive force is generated. For example, when the forward propulsive force is generated, the water pressure acting on the valve body <NUM> becomes larger than the exhaust pressure acting on the valve body <NUM>. Thereby, the valve body <NUM> is pressed against the second frame member <NUM> and closes the third hollow portion 59a of the second frame member <NUM>.

As shown in <FIG>, the valve body <NUM> opens the third hollow portion 59a of the frame member <NUM> by the exhaust pressure, when a backward propulsive force is generated. For example, when the backward propulsive force is generated, the exhaust pressure acting on the valve body <NUM> becomes larger than the water pressure acting on the valve body <NUM>. Thereby, the valve body <NUM> is partially separated from the second frame member <NUM> and opens the third hollow portion 59a of the second frame member <NUM>.

With the outboard motor <NUM> including the above configuration, the valve structure <NUM> regulates or permits the passage of exhaust gas at the third hollow portion 59a connecting the exhaust passage P1 and the discharge chamber R.

With the outboard motor <NUM>, the valve body <NUM> is configured to open and close the third hollow portion 59a of the frame member <NUM>. For example, the valve body <NUM> closes the third hollow portion 59a of the frame member <NUM> by water pressure, when a forward propulsive force is generated. In this case, discoloration around the discharge portions <NUM>, <NUM> can be suppressed, because the exhaust gas is not discharged from the discharge portions <NUM>, <NUM>.

Also, the valve body <NUM> opens the third hollow portion 59a by the exhaust pressure, when the backward propulsive force is generated. In this case, the backward propulsive force can be improved, because the exhaust gas is discharged from the discharge portions <NUM>, <NUM>.

With the outboard motor <NUM>, the valve structure <NUM> can be realized with a simple configuration, because the frame member <NUM> configures the third hollow portion 59a and supports the valve main body <NUM>. Also, the valve main body <NUM> can be easily maintained by detaching the valve main body <NUM> and the second frame member <NUM> from the first frame member <NUM> and attaching the valve main body <NUM> and the second frame member <NUM> to the first frame member <NUM>.

With the outboard motor <NUM>, the valve structure <NUM> can be realized with a simple configuration by deforming the valve body <NUM> toward the discharge chamber R side by the exhaust pressure.

With the outboard motor <NUM>, the water pressure can suitably act on the valve main body <NUM>, because the water is guided from the water intake passage Q toward the valve main body <NUM> with the pipe member <NUM>.

The configuration of the above embodiment may be configured as follows.

(A1) In the above embodiment, an example is described in which the exhaust passage P1 and the cooling water passage P2 are connected to the discharge chamber R. Instead of this, one of the exhaust passage P1 and the cooling water passage P2 may be connected to the other of the exhaust passage P1 and the cooling water passage P2, and the other of the exhaust passage P1 and the cooling water passage P2 may be connected to the discharge chamber R.

In this case, the wall portions 37a of <FIG> is connected to the wall portions 37b of the cooling water passage P2 which is provided between the engine <NUM> and the discharge chamber R. The same effect as the above effect can be obtained with this configuration.

(A2) In the above embodiment, an example is described in which the exhaust passage P1 and the cooling water passage P2 are connected to the discharge chamber R. Instead of this, only the exhaust passage P1 may be connected to the discharge chamber R, and the above valve structures <NUM>, <NUM> may be disposed in the housing <NUM>. The same effect as the above effect can be obtained with this configuration.

Claim 1:
An outboard motor (<NUM>) comprising:
an engine (<NUM>);
a drive shaft (<NUM>) extending from the engine (<NUM>) in a first direction;
a propeller shaft (<NUM>) extending in a second direction intersecting with the drive shaft (<NUM>);
a propeller (<NUM>) connected to the propeller shaft (<NUM>); the propeller (<NUM>) configured to generate a forward propulsive force in a forward direction along the second direction and configured to generate a backward propulsive force in a backward direction along the second direction;
a housing (<NUM>) configured to accommodate the engine (<NUM>), the drive shaft (<NUM>), and the propeller shaft (<NUM>) and forming a discharge chamber (R), the discharge chamber (R) configured to discharge exhaust gas of the engine (<NUM>);
a first passage (P1) configured to guide the exhaust gas from the engine (<NUM>) to the discharge chamber (R) inside the housing (<NUM>);
a second passage (Q) configured to guide water to the discharge chamber (R), the outboard motor (<NUM>) configured such that the water enters the housing (<NUM>) when the forward propulsive force is generated; and
a valve structure (<NUM>, <NUM>) configured to regulate or permit passage of the exhaust gas at a first connection (131c, 59a) by exhaust pressure and water pressure, the first connection (131c, 59a) connecting the first passage (P1) and the discharge chamber (R), the outboard motor (<NUM>) configured such that the exhaust pressure acts from the first passage (P1) toward the discharge chamber (R), the water pressure acts from the second passage (Q) toward the discharge chamber (R);
the valve structure (<NUM>, <NUM>) is configured to regulate the passage of the exhaust gas at the first connection (131c, 59a) by the water pressure, when the forward propulsive force is generated; and
the valve structure (<NUM>, <NUM>) is configured to permit the passage of the exhaust gas at the first connection (131c, 59a) by the exhaust pressure, when the backward propulsive force is generated, wherein the housing (<NUM>) includes a water intake portion (<NUM>); the water intake portion (<NUM>) is configured and provided to take the water into the second passage (Q) when the forward propulsive force is generated; the water intake portion (<NUM>) includes an opening (36a); and at least a part of the opening (36a) opens forward in the forward direction along the second direction.