JP2000045891A - Multi-cylinder type four cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the height of a surge tank as far as possible, and to decrease the height of attachment of the surge tank as far as possible. SOLUTION: A crankshaft 10 in a multi-cylinder four cycle engine 9 has its axis which is vertically laid, and engine cylinders 11 are vertically arranged in multiple stages in rear of the crankshaft 10. Intake pipe 66 which are connected at their rear ends to one end of respective intake-air passages 31 in a cylinder head 22 covering the combustion chamber side 11a of a cylinder, are vertically arranged in multi-stages, and are connected at their front ends to a surge tank 67. The topmost one of the intake pipe is laid in a substantially horizontal direction, and the second one is laid so that its lower end part is directed forwardly upward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder four-stroke engine having an intake pipe extending in the front-rear direction.

[0002]

2. Description of the Related Art Conventionally, a multi-cylinder four-stroke engine having an intake pipe extending in the front-rear direction is used for an outboard motor or the like.
The intake pipes are arranged in multiple stages in the vertical direction, and the intake pipes are provided substantially parallel to each other and inclined forward and upward.

[0003]

If the intake pipes are arranged substantially parallel to each other, the height of the surge tank connected to the intake pipe becomes large and bulky. In addition, if the uppermost intake pipe is provided so as to be inclined forward, it is necessary to raise the mounting position of the surge tank, so that the overall height increases and the center of gravity increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a multi-cylinder 4 capable of minimizing the height of a surge tank and reducing the mounting height of a surge tank as much as possible. It aims to provide a cycle engine.

[0005]

The crankshaft (10) of the multi-cylinder four-stroke engine (9) according to the present invention has its axis lined up and down. A cylinder (11) is arranged. A cylinder head (22) covers the combustion chamber side (11a) of the cylinder. The cylinder head has an intake passage (31) having a leading end opening into the combustion chamber and an exhaust gas for each combustion chamber of each cylinder. A passage (32) is formed. The other end of each intake passage of the cylinder head is connected to the rear end of an intake pipe (66). The intake pipes are arranged in multiple stages in the vertical direction, and the front end extends forward. And is connected to the surge tank (67).

The first-stage intake pipe from the top is substantially horizontal over substantially the entire length, and the second-stage intake pipe from the top is provided with a portion inclined upward and forward. The front end portion is closer to the first-stage intake pipe from the top than the rear end portion.

The lengths of the intake pipes are substantially equal, and
Adjustment of the mounting position of the end of the intake pipe may be performed at the connection with the surge tank.

Further, the tip (66a) of the first-stage intake pipe from above may protrude into the surge tank.

The surge tank partially bulges toward the intake pipe, and the bulge (67a) is larger than the cross section of the intake pipe, and the bulge is located at the second stage from the top. The intake pipe may be connected.

In some cases, the intake pipe arranged at least below the third stage from the top is substantially horizontal over substantially the entire length.

In this specification, the side on which the cylinder is disposed relative to the crankshaft is referred to as the "rear side".

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of a multi-cylinder four-stroke engine according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an outboard motor equipped with a multi-cylinder four-cycle engine according to the present invention, as viewed from the side. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a plan sectional view of the engine of the outboard motor of FIG. FIG. 4 is a plan view of the inside of the outboard motor of FIG. FIG. 5 is a side view of an interlocking mechanism that interlocks the throttle cable with the valve shaft of the throttle body. FIG. 6 is a diagram showing the relationship between the input and output of the interlocking mechanism.
FIGS. 7A and 7B are cross-sectional views showing a state of attachment between the surge tank and the intake pipe. FIG. 7A is a diagram showing an example of attachment, and FIG. 3 and 4, only the left half (port side) of the lower cowling 2 is shown. Also,
In FIG. 3, a flywheel, a pulley of a camshaft, a timing belt, and the like, which are not shown in the sectional view, are shown for reference. And in FIG.
The lower part of the flywheel 42 is originally shown by a broken line, but is shown by a solid line for easy understanding.

First, the overall structure of the outboard motor will be described. In FIG. 1, the outboard motor is covered with a housing including an upper cowling 1, a lower cowling 2, an upper casing 3, and a lower casing 4 in this order from the upper side. A mounting bracket 6 for mounting the outboard motor to a small boat is mounted and fixed to a transom 7 of the small boat. An outboard motor main body is rotatably attached to a rear portion of the mounting bracket 6 via a pivot shaft or the like.

Inside the cowlings 1 and 2 including the upper cowling 1 and the lower cowling 2, a fuel injection type L-type four-cylinder four-cycle engine 9 is disposed. The crankshaft 10 of this engine 9 has its axis provided substantially vertically, that is, in the vertical direction, and behind the crankshaft 10, four cylinders 11 are provided in the vertical direction. Further, four pistons 13 are connected to the crankshaft 10 via connecting rods 14, respectively. The pistons 13 are slidably disposed inside the respective cylinders 11. The case 17 of the engine 9 includes a cylinder block 20 that forms the four cylinders 11 described above, a crankcase 21 that covers the crankshaft 10 side of the cylinder block 20, and a combustion chamber 11a side that covers the cylinder block 20. It comprises a closed cylinder head 22. The engine case 17 is fixed to the upper surface of the upper casing 3 via a guide exhaust 23.

The lower end of the crankshaft 10 is
The drive shaft 2 extending from the engine case 17 and disposed in the upper casing 3
6. The rotation of the drive shaft 26 is provided via a bevel gear (not shown) or the like to the propeller 2 rotatably provided at the rear end of the lower casing 4.
8 is transmitted.

The cylinder head 22 has a front end opening into the combustion chamber 11a to supply air to the cylinder 11, and a front end opening into the combustion chamber 11a. An exhaust passage 32 for exhausting gas is formed for each cylinder 11. This intake passage 31
Port is opened and closed by the intake valve 35, and the port of the exhaust passage 32 is opened and closed by the exhaust valve 36. And, this intake valve 35
Is driven by an intake valve camshaft 38 and the exhaust valve 36 is driven by an exhaust valve camshaft 39. The intake valve camshaft 38 and the exhaust valve camshaft 39 extend vertically.

In FIG. 1, the upper end of the crankshaft 10 projects from the engine case 17,
A pulley 41 is pressed into the upper end of the crankshaft 10 and fixed. A flywheel 42 is attached to the upper side of the pulley 41 with a nut 43. Pulleys 46 are also provided on the intake valve camshaft 38 and the exhaust valve camshaft 39. A timing belt 48, which is an endless transmission member, is stretched over a pulley 41 of the crankshaft 10 and a pulley 46 of the camshafts 38 and 39.
0 and the camshafts 38 and 39 are linked.

A rear end of an intake pipe 66 made of metal such as aluminum is connected to an end of each intake passage 31 of the cylinder head 22. The intake pipe 66 extends in the front-rear direction along the left side (i.e., port side) side of the engine case 17, and has a front end connected to a surge tank 67 disposed at a front part in the cowlings 1 and 2. ing. A total of four intake pipes 66 are provided in the up-down direction. In the plan views shown in FIGS. 3 and 4, the intake pipes 66 extend from the rear end while bending in the lateral direction, and then extend straight forward. A curved portion 68 that curves sequentially from the end to the front side, and a linear portion 69 are formed. The root of the curved portion 68 with the cylinder head 22 is inclined so as to be slightly rearward toward the outer side (that is, the left side) of the cowlings 1 and 2, and the length of the intake pipe 66 is longer. At the same time, air can be smoothly taken in. Also,
In the plan view, each intake pipe 66 has substantially the same shape.

In this way, the intake pipe 66 is arranged with a space from the cylinder block 20, and a relatively large component arrangement space 70 a is formed between the intake pipe 66 and the cylinder block 20. As shown in FIG. 2, when viewed from the side, the rear curved portion 68 is disposed substantially horizontally in the uppermost stage and the third-stage intake pipe 66 from the top, while the second-stage curved portion 68 from the top. In the intake pipe 66 at the fourth stage from the top, the intake pipe 66 is arranged to be inclined upward toward the front.
A relatively large space 70 for rotating parts is provided between the second-stage intake pipe 66 from the top and the third-stage intake pipe 66 from the top.
b is formed. The straight portion 69, which is the front portion of the intake pipe 66, is arranged so as to be substantially horizontal and inclined inward toward the front side, and the front end portion is connected to the surge tank 67. . The outboard motor can be tilted, and the tilt angle of the intake pipe 66 is changed in accordance with the tilt. Therefore, in this specification, a general case in which the outboard motor is installed with the crankshaft 10 in a vertical state is described as a reference.
Means that it is in a plane perpendicular to the axis of the crankshaft 10.

Further, at the rear of the straight portion 69 of each intake pipe 66, a machined throttle body 71 is provided. The first-stage intake pipe 66 and the second-stage intake pipe 66 from above are configured as one set,
The valve shaft of the second-stage throttle body 71 and the valve shaft of the second-stage throttle body 71 are integrated into one valve shaft. Similarly, the third-stage intake pipe 66 and the fourth-stage intake pipe 66 from the top are configured as one set, and have substantially the same configuration as the set of the first-stage and second-stage intake pipes 66. Has become. In addition, the valve shaft of the third-stage throttle body 71 and the valve shaft of the fourth-stage throttle body 71 are integrated into one valve shaft.

The valve shafts of the first-stage and second-stage throttle bodies 71 and the valve shafts of the third-stage and fourth-stage throttle bodies 71 are connected to each other. A rotating component 73 such as a return spring 73a for rotating the valve shaft and a rotating lever 73b is attached. The rotating component 73 is disposed in a rotating component space 70 b between the intake pipes 66, and the rotating lever 73 b rotates integrally with the valve shaft of the throttle body 71. Further, a throttle position sensor 74 is attached to the upper end of the valve shaft of the uppermost throttle body 71.

In the vicinity of the connection between the intake passage 31 of the cylinder head 22 and the intake pipe 66, an electronically controlled injector 76 is provided for each intake pipe 66.
The injector 76 is arranged on the rear side of the intake pipe 66 and is connected to a fuel rail 77. The fuel rail 77 is connected to a vapor separator tank 79 by a fuel pipe 80, and is supplied with fuel such as gasoline. The vapor separator tank 79 is provided with the intake pipe 6.
It is arranged in a parts arrangement space 70 a formed between the cylinder block 6 and the cylinder block 20, and is attached to the intake pipe 66 with bolts or the like. Vapor separator tank 79
Is supplied with fuel from a fuel tank (not shown) mounted on a small boat to which the outboard motor is attached via a fuel pump 81.

An ISC (idle speed control) 8 serving as an intake system component for adjusting the flow rate of air in order to reduce the rotation fluctuation during idling is provided above the vapor separator tank 79 in the component arrangement space 70a.
3 is attached to the intake pipe 66 and arranged.

When a throttle bar (not shown) is operated, the throttle cable 91 moves back and forth, and the valve shaft of the throttle body 71 is rotated via a link mechanism 92 and a rotating lever 73b as an interlocking mechanism. Link mechanism 92
Is a rod 94 as an interlocking member attached to the tip of the rotating lever 73b, a first swing lever 95 having one end connected to the front end of the rod 94, and an interlock with the first swing lever 95. And one end of the second swing lever 96 is connected to the rear end of the throttle cable 91. The rod 94 is provided with an adjusting portion 94a as an adjusting mechanism for adjusting the length. The first swing lever 95 has a substantially U-shape, can rotate about a shaft 95b in the left-right direction, and has an engagement pin 95a as an engagement portion at one end. . On the other hand, at one end of the second swing lever 96,
A cam hole 96a as a cam that engages with the engagement pin 95a is formed. Further, the second swing lever 96 can rotate around a shaft 96b in the left-right direction. The shaft 95b of the first swing lever 95 is connected to the shaft 9 of the second swing lever 96.
6b and the first swing lever 9
5 and the second swing lever 96 are connected to these shafts 95b, 9
The engine case 17 is rotatable around the center 6b.
Attached to. The rotation lever 73b is located above the throttle cable 91. Further, the link mechanism 92 and the rotating lever 73b are connected to the intake pipe 66.
Are disposed closer to the engine case 17 than the surfaces on the cowlings 1 and 2 side.

Then, the throttle cable 91 is connected as shown in FIG.
As shown by the arrow, the second swing lever 96 rotates counterclockwise when it moves rearward, and the first swing lever 95 moves.
Of the second swing lever 96 is engaged with the cam pin 96a of the second swing lever 96.
Sliding while engaging with. Then, the first swing lever 95
Rotates clockwise, and the rod 94 moves backward. Accordingly, in the plan sectional view of FIG.
b rotates clockwise, and the throttle body 71
Is rotated clockwise integrally with the rotation lever 73b. As described above, since the link mechanism 92 is provided with the cam, the relationship between the input (the amount of movement of the throttle cable 91) and the output (the amount of rotation of the rotating lever 73b) is non-linear as shown in FIG. The output is rapidly increased when the input is increased to some extent. Since the outboard motor often operates at a constant speed at medium to low speeds, the output is insensitive when the input is small, and the operation of the constant speed is facilitated. Further, fine adjustment of the link mechanism 92 is performed by the adjusting portion 94a of the rod 94. Note that a member denoted by reference numeral 98 is a shift cable that switches the outboard motor between forward and backward.

Further, the structure for mounting the intake pipe 66 and the surge tank 67 is as shown in FIG. 7 (a) or 7 (b). Then, the curved portion 68 of the intake pipe 66
However, the lengths of the intake pipes 66 are substantially the same as each other regardless of the case where the intake pipe 66 is inclined forward and the case where it is substantially horizontal. That is, in the multi-cylinder four-cycle engine shown in FIG. 7A, the top end 66a of the intake pipe 66 at the first and third stages from the top is the surge tank 6
7, while the intake pipe 66 at the second and third stages from the top is a surge tank 67.
It is attached without protruding inside. In the modification shown in FIG. 7B, the surge tank 6
7, that is, the side of the intake pipe 66 swells and bulges 67
a are formed. The vertical cross section of the bulging portion 67a is formed larger than the cross section of the intake pipe 66, and the second and fourth tier intake pipes 66 are connected to the bulging portion 67a, respectively. I have.

In the outboard motor configured as described above,
When the crankshaft 10 rotates, the surge tank 67
Air is sucked into the inside, and the sucked air passes through the intake pipe 66 and the intake passage 31 and is supplied with fuel from the injector 76 to become a fuel mixed gas, and the cylinder 1
It flows into one combustion chamber 11a. When a throttle lever (not shown) is operated, the valve shaft of the throttle body 71 is driven via the throttle cable 91, the link mechanism 92, and the rotation lever 73b, and the combustion chamber 1
The inflow amount of air flowing into 1a is adjusted. The rotation angle of the valve shaft of the throttle body 71 is detected by a throttle position sensor 74. Further, the combustion chamber 11a
The fuel mixture gas flowing into the inside is ignited by a spark plug (not shown) and burned. Exhaust gas generated at this time passes through the exhaust passage 32 and the casings 3 and 4 and is discharged from the boss of the propeller 28 or the like. ing.

Since the lengths of the intake pipes 66 are substantially the same, the characteristics of each cylinder (torque characteristics at medium to low speeds, etc.) can be made as uniform as possible, making it easy to design a multi-cylinder four-cycle engine. And the engine 9 can rotate smoothly and stably.

As described above, in the first embodiment, the intake pipe 66 has almost no downwardly extending portion over substantially the entire length, and fuel or the like flows backward (from the combustion chamber 11a side to the surge tank 67). Side)) is reduced.

The rear part of the intake pipe 66 of the second stage from the top is inclined forward and upward, and a relatively large space is provided below the front part of the intake pipe 66 of the second stage from the top. This space can be formed by a component (for example, the rotating component 7).
3) can be effectively utilized.

The straight portion 69 of the intake pipe 66 is arranged so as to become more outward as it goes rearward.
Can be positioned as far outward as possible. Therefore, the radius of curvature of the curved portion 68 can be increased, and the flow of air can be made smooth. Further, the surge tank 67 approaches the center axis of the cowlings 1 and 2, and the lateral width of the front portions of the cowlings 1 and 2 can be reduced as much as possible.

Further, in an outboard motor in which a fuel injection type engine 9 is provided in the cowlings 1 and 2, an injector 76 for supplying fuel is provided near the rear end of the intake pipe 66 (that is, after the curved portion 68). (Near the end) or the cylinder head 22 to improve the response of fuel supply. Also, the throttle body 71
Is a straight section 6 located downstream of the surge tank 67.
9, the response of the air flow rate can also be improved. And the throttle body 7
1 is machined with the center line of the hole being straight,
Although it is relatively difficult to attach to the curved portion 68, it can be attached to the straight portion 69 relatively easily.

Next, a second embodiment of the multi-cylinder four-cycle engine according to the present invention will be described with reference to FIG. FIG. 8 is an enlarged view of a main part of the second embodiment. In the description of the second embodiment, the same reference numerals are given to components corresponding to the components of the first embodiment, and a detailed description thereof will be omitted.

FIG. 8 is a view corresponding to FIG. 2 of the first embodiment, in which the four-cycle engine 9 is an L-type three-cylinder, and three intake pipes 66 are provided in the vertical direction. A rear portion of the second and third intake pipes 66 from the top, that is, a curved portion 68 is disposed so as to be inclined upward and forward, and the uppermost intake pipe 66 and the lowermost intake pipe 66 The distance is as small as possible.

As in the first embodiment, the valve shaft of the throttle body 71 is provided in the vertical direction, and the respective valve shafts are interlocked with each other. The bottom throttle body 71
Attached to the lower end of the valve shaft. The shaft 95b of the first swing lever 95 is connected to the shaft 96b of the second swing lever 96.
The cam hole 96a is formed below the shaft 96b in the second swing lever 96. The rotating lever 73 b and the rod 94 are located below the rear end of the throttle cable 91.

Further, the structure for mounting the intake pipe 66 and the surge tank 67 is similar to the structure shown in FIG. 7A or 7B of the first embodiment. In other words, the first-stage intake pipe 66 protrudes largely into the surge tank 67 from the top so that the lengths of the intake pipes 66 are substantially the same, and the second-stage intake pipe 66 is larger than that. Projecting into the surge tank 67,
The stage intake pipe 66 is attached without protruding into the surge tank 67. Alternatively, the bulging portion 67a of the surge tank 67 is provided in two stages vertically, the lower side bulges greatly, and the second-stage intake pipe 66 is attached to the upper bulging portion 67a. A third-stage intake pipe 66 from above is attached to the bulging portion 67a.

As described above, in the second embodiment, between the intake pipes 66, the rotating component space 7 shown in FIG.
Since 0b is not formed, the distance between the uppermost intake pipe 66 and the lowermost intake pipe 66 can be made as small as possible. As a result, the height of the cowlings 1 and 2 can be made compact.

Further, a relatively large space can be formed below the front part of the intake pipe 66 at the third stage from the top, and this space is made up of components (for example, the rotating component 73 and the shift cable 9).
8) can be effectively utilized.

Next, a third embodiment of the multi-cylinder four-cycle engine according to the present invention will be described with reference to FIG. FIG. 9 is an enlarged view of a main part of the third embodiment. In the description of the third embodiment, the same reference numerals are given to components corresponding to the components of the first embodiment, and a detailed description thereof will be omitted.

FIG. 9 is a view corresponding to FIG. 2 of the first embodiment, in which the four-cycle engine 9 is an L-type five-cylinder, and five intake pipes 66 are provided in the vertical direction. The rear portions of the intake pipes 66 at the second, third, and fifth stages from the top, that is, the curved portions 68 are arranged to be inclined forward and upward, while the first and fourth stages from the top are arranged at the rear. Intake pipe 6
6 is arranged substantially horizontally over substantially the entire length. A relatively large space is formed between the third-stage intake pipe 66 from the top and the fourth-stage intake pipe 66, and the fifth-stage from the top, that is, below the lowest-stage intake pipe 66. A relatively large space is formed.

Further, the structure for mounting the intake pipe 66 and the surge tank 67 is the same as that of the first and second embodiments, and the length of each intake pipe 66 is as follows.
It is almost the same.

The embodiments of the present invention have been described above in detail.
The present invention is not limited to the above embodiment,
Within the gist of the present invention described in the claims,
Various changes can be made. Modification examples of the present invention are exemplified below. (1) In the first embodiment, the multi-cylinder four-cycle engine 9 is an L-type four-cylinder four-cycle engine.
The type, the number of cylinders, and the like can be appropriately changed. For example, it may be a V-type four cylinder. The engine 9 is suitable for use in an outboard motor, but may be used for applications other than the outboard motor.

(2) The relationship of the arrangement in the left-right direction can be reversed. (3) In the embodiment, the intake pipe 66 such as the second stage from the top is partially (especially at the rear) inclined forward and upward, but only the front is inclined upward and forward. It is also possible to incline upwards over the entire length. In addition,
The intake pipes 66 are all substantially horizontal, or rise up, and hardly fall down.

(4) In the embodiment, the mounting position of the end of the intake pipe 66 having substantially the same length is adjusted at the connection with the surge tank 67, but the structure is shown in FIG.
It is not limited to the structure shown in FIG.
It can be changed as appropriate. (5) In the embodiment, although the intake system components such as the ISC 83 and the vapor separator tank 79 are arranged as the components in the component arrangement space 70a, electrical components such as the control unit and the regulator rectifier are housed therein. It is also possible to arrange an electric box or the like that is not used. It is preferable that the electrical component box and the vapor separator tank 79 be attached to the intake pipe 66 for cooling.

(6) In the first embodiment, the rotary component 7 of the throttle body 71 is provided in the rotary component space 70b.
Although 3 is arranged, other parts can be arranged. (7) In the embodiment, the injector 76 injects fuel into the intake passage 31 and the intake pipe 66. However, the injector 76 may be provided in the cylinder head 22 to directly inject the fuel into the cylinder 11. is there. It is also possible to use a carburetor type.

(8) In the second embodiment, the return spring 73a and the rotary lever 73b are attached to the lower end of the valve shaft of the lowermost throttle body 71, but the uppermost throttle body It is also possible to attach to the upper end of the 71 valve shaft. (9) In the embodiment, although the throttle body 71 is attached to the intake pipe 66, the surge tank 67
It is also possible to attach to. (10) The inclination of the intake pipe not specified in the claims can be appropriately selected. It is preferable that the inclination of all the intake pipes be upward or substantially horizontal so that fuel or the like does not flow backward.

[0047]

According to the present invention, the intake pipe at the second stage from the top is provided with a portion inclined upward and forward, and is inclined substantially horizontally or upward over the entire length. Since the front end is closer to the first-stage intake pipe than the rear end, a relatively large space can be formed below the front of the second-stage intake pipe from the top. it can.
Therefore, this space can be effectively used for arranging parts and the like. Further, the height of the surge tank can be reduced. Moreover, since the first-stage intake pipe is substantially horizontal over substantially the entire length, it is possible to reduce an increase in the mounting position of the surge tank. As a result, the center of gravity can be lowered, and the overall height can be reduced. Also, the intake pipe of the first stage from the top also has almost no downwardly inclined portion, so that backflow of fuel or the like can be prevented as much as possible.

The lengths of the intake pipes are substantially equal, and
Adjustment of the mounting position of the end of the intake pipe may be performed at the connection with the surge tank. In such a case, since the length of each intake pipe is substantially equal, the characteristics of each cylinder can be made as uniform as possible. As a result, the design of the engine becomes easy, and the engine can rotate smoothly and stably. Moreover, as described above, the inclination of each intake pipe is different, but the mounting position of the end of the intake pipe is adjusted at the connection part with the surge tank, and the length of the intake pipe can be easily made equal. Can be.

Further, when the tip of the first-stage intake pipe from the top projects into the surge tank, the length of the intake pipe can be easily adjusted by changing the amount of projection. it can.

The surge tank partially bulges toward the intake pipe, and the bulge is larger than the cross section of the intake pipe. May be connected. In such a case, the protrusion of the end of the intake pipe into the surge tank is reduced, and the air in the surge tank can flow smoothly. As a result, a large amount of air can smoothly flow into the cylinder.

When the intake pipe arranged at least below the third stage from the top is substantially horizontal over substantially the entire length, the space between the intake pipes below the second stage from the top is reduced. , A relatively large space can be formed. Therefore, this space can be effectively used for arranging parts and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an outboard motor equipped with a multi-cylinder four-stroke engine according to the present invention as viewed from the side.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a plan sectional view of the engine of the outboard motor of FIG. 1;

FIG. 4 is a plan view showing the inside of the outboard motor of FIG. 1;

FIG. 5 is a side view of an interlocking mechanism that interlocks a throttle cable and a valve shaft of a throttle body.

FIG. 6 is a diagram showing the relationship between input and output of an interlocking mechanism.

FIGS. 7A and 7B are cross-sectional views showing a mounting state of a surge tank and an intake pipe. FIG. 7A is a diagram showing an example of mounting, and FIG. 7B is a diagram showing a modification of the mounting.

FIG. 8 is an enlarged view of a main part of the second embodiment.

FIG. 9 is an enlarged view of a main part of the third embodiment.

[Explanation of symbols]

 Reference Signs List 9 engine 10 crankshaft 11 cylinder 11a combustion chamber 22 cylinder head 31 intake passage 32 exhaust passage 66 intake pipe 66a tip of intake pipe 67 surge tank 67a bulge of surge tank

Claims (5)

[Claims] The crankshaft has an axial line arranged in a vertical direction, and a plurality of cylinders arranged in a vertical direction behind the crankshaft. A cylinder head covers a combustion chamber side of the cylinder. In the cylinder head, an intake passage and an exhaust passage each having a front end opening into the combustion chamber are formed for each combustion chamber of each cylinder, and at the other end of each intake passage of the cylinder head, Each of the rear ends of the intake pipes is connected. This intake pipe is a multi-cylinder four-cycle engine in which the intake pipes are arranged in multiple stages in the vertical direction and the front end extends forward and is connected to the surge tank. The intake pipe of the first stage from the top is substantially horizontal over substantially the entire length, and the intake pipe of the second stage from the top is provided with a part that is inclined upward and forward, and It is inclined to the horizontal or forwardly upward, a multi-cylinder four-stroke engine is more on the front end portion of the rear end, characterized in that in proximity to the intake pipe of the first row from the top. 2. The intake pipe according to claim 1, wherein the length of each intake pipe is substantially equal, and the adjustment of the mounting position of the end of the intake pipe is performed at a connection portion with the surge tank.
A multi-cylinder four-stroke engine as described. 3. A top end of the first-stage intake pipe from above projects into the surge tank.
A multi-cylinder four-stroke engine as described. 4. A surge tank partially bulges toward the intake pipe, and the bulge is larger than a cross section of the intake pipe, and the bulge is located at a second-stage intake pipe from above. 3. The multi-cylinder four-stroke engine according to claim 2, wherein? 5. The multi-cylinder according to claim 1, wherein the intake pipe disposed below at least the third stage from above is substantially horizontal over substantially the entire length. 4 cycle engine.