JPH03172570A - Engine for outboard motor - Google Patents

Abstract

PURPOSE:To uniformize an air-fuel mixture being fed to each combustion chamber by constituting an intake manifold at each cylinder so as to be equal in length, in a device which installs a flywheel and a camshaft driving mechanism both on the upper end of a crankshaft extending in the almost vertical direction. CONSTITUTION:When being executed to an inline type 3-cylinder engine whose crankshaft is extended in the vertical direction, length of each intake manifold 3 being installed in response to every cylinder of a device in a fuel supply system, namely, a joining plane 2a between each carburetor 2 and the intake manifold 3 and an interval among three intake ports 3a are made up of upper, medium and lower stages so as to become constant all. Accordingly, so far as the carburetor 2 at the lower stage, it is set up in direction of more distant to the outside, and a line connecting the center of the joining plane 2a is tilted as far as an angle alpha in the vertical direction. In addition, an upper end of the uppermost carburetor 2 is situated in the upper part than an engine block upper end and further situated in the lower part than a turning plane of a flywheel 13. With this constitution, such an air-fuel mixture as constant in air-fuel ratio is made suppliable into all cylinders.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an outboard engine which is characterized by the arrangement of devices in the intake and fuel supply systems and which is designed to improve engine response.

(Prior art) As an engine for an outboard motor that can be easily installed and removed from a small boat, etc., for example,
Engines like No. 1 are known. In this case, in a two-cylinder engine with cylinder rows arranged vertically and a crankshaft oriented vertically, one carburetor is installed on the upper side of the engine body, and a pair of intake passages are connected from this carburetor to the upper and lower cylinders. The air-fuel mixture is distributed and supplied through communication.

(Problem M to be solved by the invention) However, when supplying air-fuel mixture from one carburetor to multiple cylinder cylinders, the cylinder rows are arranged in tandem, so the distribution is not uniform, which reduces engine performance. It was supposed to be done. Furthermore, if a carburetor is provided for each cylinder and assembled in tandem on the side of the engine, the length of the upper intake manifold and the length of the lower intake manifold tend to be different.

In other words, such vertically arranged carburetors are usually placed higher than each intake boat to prevent gas accumulation, but the vertical pitch of each carburetor is larger than the vertical pitch of the cylinder bore, and the vertical pitch of each carburetor is larger than the vertical pitch of the cylinder bore. The length of the carburetor's intake manifold had to be increased. When the length of the intake manifold changes in this way, the vaporized fuel in each intake manifold changes due to the influence of so-called wall flow, which causes a problem that a stable engine response cannot be obtained, especially during idling.

Furthermore, in the case of such multiple carburetors, there is also a desire to configure the throttle link mechanism connected to each carburetor as simply as possible.

(Means for Solving the Problems) In order to solve the problems, the present invention provides a structure in which the upper ends of the intake and fuel supply systems, which are assembled in tandem on the side of the engine body, are located below the rotating surface of the flywheel. Located above the top of the engine block,
Each intake manifold connecting each cylinder and each carburetor was configured to have the same length. For this reason, each carburetor on the side of the engine is moved further away from the crankshaft down to the lower carburetor, or the joint surface between each carburetor and each intake manifold is
The lower the position, the further away it is from the cylinder head. or,
Alternatively, it is curved so that it extends outward as it reaches the lower intake manifold.

(Function) By making each intake manifold the same length, the air-fuel mixture is uniformly supplied to each combustion chamber. This is especially effective when the negative pressure in the intake manifold decreases during idling, increasing the tendency of the air-fuel mixture to liquefy due to wall flow. Furthermore, since the throttle links are aligned in a straight line, the link mechanism connected to the multiple carburetors can be easily and simply constructed.

(Embodiment) An embodiment of the outboard motor engine of the present invention will be described based on the attached drawings.

1 to 3 show a first embodiment of the present invention, FIG. 1 is an external side view showing the assembled state of components around the engine section, and FIG. 2 is a cross section taken along the line II-TI in FIG. 1. 3 are explanatory diagrams of the arrangement of the carburetors as seen from the direction of line III--III in FIG. 2.

The outboard motor engine of the present invention is provided at the upper part of the outboard motor main body as shown in FIG. 6, and the particle shaft 52 extending downward from the output shaft 51 of the engine main body 1 is
It is configured to be connected to a horizontal propeller shaft at the bottom of the outboard motor to rotationally drive the propeller 53 at the extending end of the horizontal propeller shaft. The outboard motor thus constructed can be attached to and detached from the stern of the hull of a small vessel.

The engine at the top of the outboard motor is a 4-stroke single overhead cam (SOHC) type, and is configured as a Siamese-type inline 3-cylinder in three vertical rows with the crankshaft running vertically and the cylinder axis running horizontally.

That is, as shown in FIG. 1, devices for the intake and fuel supply systems are assembled in tandem on one side of the engine body 1 housed in the casing C. It consists of a carburetor 2, an intake manifold 3, a fuel hose 4, and an intake silencer 5, etc., which are connected to the carburetor 2, intake manifold 3, fuel hose 4, and vertically arranged carburetors 2, which are provided corresponding to each cylinder. The fuel supplied from the engine is atomized and the air-fuel mixture is supplied to each intake manifold 3 communicating with the cylinder head portion 1a of the engine. A fuel pump 4a and a fuel filter 4b are connected to this fuel hose 4, which communicates with an external fuel tank. Further, the vertically arranged vaporizers 2 are arranged at an oblique angle in the direction of the front and back of the paper of FIG. 1, as will be described later.

Throttle rods 8 are connected to the sides of the upper and lower carburetors 2 to form a link mechanism 9.

As shown in Fig. 2, the engine body 1 is arranged near the center of the casing C in the left-right width direction, and on one side there are the above-mentioned carburetor 2, intake manifold 3, and other intake and fuel system devices. At the same time, an exhaust manifold 6 extends from the other side, and components such as an electrical box 7 are also provided. The engine body 1 also includes a cylinder head portion 1a with which an intake manifold 3 and an exhaust manifold 6 communicate, a cylinder portion lb that is integrally connected to the cylinder head portion 1a, a crankcase portion IC, and a piston 10 and a connecting rod 11.
A crankshaft 12 connected to the engine block is oriented vertically, and the upper end of the crankshaft 12 protrudes upward from the upper end of the engine block, to which a flywheel 13 shown in FIG. 3 is attached.

On the other hand, a camshaft drive device 14 as shown in FIG. 2 is provided on the cylinder head portion 1a side of the engine body 1.
The camshaft 15 rotates by the drive of the engine,
The rocker arm 16 is periodically swung to drive the intake valve 17 and exhaust valve 18 at the tip of the rocker arm 16. Further, the intake valve 17 and the exhaust valve 18 are connected to the intake boat 3a and the exhaust boat 6, which are the extending ends of the intake manifold 3 and exhaust manifold 6 described above.
I am facing a.

The length of the intake manifold 3, that is, the distance between the joint surface 2a of the carburetor 2 and the intake manifold 3 and the intake boat 3a, is constant for each of the upper, middle, and lower stages, and therefore, as shown in FIG. The carburetor 2 is positioned on the outer side, that is, in the direction away from the crankshaft. Therefore, the line connecting the centers of the bonding surfaces 2a is inclined in the vertical direction by an angle α. Further, the upper end of the uppermost carburetor 2 is located above the upper end of the engine block and below the rotating surface of the flywheel 13.

Each exhaust manifold 6 extending from the side exhaust boat 6a communicates with a vertical communication section 19, and exhaust gas is discharged downward through an exhaust vibe connected to the vertical communication section 19. Note that 20 in FIG. 3 indicates a belt for transmitting the rotation of the crankshaft to the camshaft drive device.

By making the length of the intake manifold 3 constant in this manner, the air-fuel ratio of the air-fuel mixture supplied into each engine cylinder becomes uniform, and engine response is improved even during idling operation.

FIG. 4 is an external side view showing a second embodiment of the present invention,
The joint surface 22a between the carburetor 22 and the intake manifold 23 is located farther away from the cylinder head portion 21a side of the engine body 21 as it is lower. Therefore, the joint surface 22
The line connecting a vertically is inclined by an angle β from the vertical line, and in this case as well, the length of each intake manifold 23 can be made constant as in the case described above. Also, in this case, although it is not necessary to provide for the lateral deviation of each vaporizer 22 as shown in the first embodiment, it is possible to do so in combination with the method shown in FIG. The amount of deviation may be made smaller. FIG. 5 is a plan view showing a third embodiment of the present invention, in which the bending of the curved portion of the intake manifold 33 is changed. That is, compared to the highest intake manifold 33a, the amount of outward protrusion is increased toward the middle intake manifold 33b and the lower intake manifold 33c. In this case as well, the lengths of each intake manifold 33a, 33b, and 33c can be made equal,
There is a similar effect, and the lateral deviation of each carburetor in the first embodiment,
Alternatively, it goes without saying that this method may be used alone or in combination with the method of tilting the joint surface 22a of the second embodiment.

Further, the carburetor 02 of the first embodiment shown in FIG. 1, the carburetor 22 of the second embodiment shown in FIG. 4, and the carburetor 32 of the third embodiment shown in FIG. In addition, the amount of lateral protrusion is flush, and the throttle link mechanism configured by connecting the upper and lower carburetors can be easily and simply constructed.

(Effects of the Invention) As described above, in the outboard engine of the present invention, since the plurality of vertically arranged intake manifolds have the same length, even if the negative pressure inside the intake manifold decreases, no difference in air-fuel ratio occurs. A mixture with a constant air-fuel ratio is supplied to all cylinders, improving engine response.

Another advantage is that the throttle link mechanism connected to each carburetor can be easily configured.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an external side view showing the assembled state of components around the engine section, and FIG. 2 is a cross section taken along line II-II in FIG. 1. Figure 3 is the second
An explanatory diagram of the arrangement of the vaporizers seen from the direction of line III-III in the figure, FIG. 4 is an external side view showing the second embodiment,
FIG. 5 is a plan view showing the third embodiment, and FIG. 6 is an overall view of the outboard motor main body. In the figure, 1 is the engine body, 2 is the carburetor, 2a is the joint surface, 3 is the intake manifold, 12 is the crankshaft, 13 is the flywheel, 21 is the engine body, 21a
is the cylinder head, 22 is the carburetor, 22a is the joint surface,
23.33 indicates the intake manifold, and C indicates the casing. Patent applicant: Honda Motor Co., Ltd. Agent
Person Patent Attorney Part 2 1) Yong-Immediate Question Patent Attorney Kuni Ohashi Opening of Business Patent Attorney
Yu Koyama 1 2

Claims (4)

[Claims] (1) In an in-line multi-cylinder engine in which a plurality of cylinders are arranged in tandem and a flywheel and a camshaft drive device are assembled above the top surface of the engine block on the upper end of a crankshaft that extends approximately vertically, each Each intake manifold extends from the cylinder head to the side of the engine body along the cylinder axis, and each intake manifold is connected to each of the intake manifolds.
and a fuel supply system in a vertical line, with the upper end of the intake and fuel supply system located at the top being located at least below the rotating surface of the flywheel and above the upper end of the engine block, and each cylinder head. An outboard engine characterized in that each of the intake manifolds extending from the section has the same length. (2) The first aspect of the present invention is characterized in that each of the carburetors forming a part of each of the intake and fuel system devices is arranged so as to be laterally separated from the crankshaft as it reaches the lower carburetors. Outboard engine listed. (3) The joint surface between each carburetor and each intake manifold, which form part of each intake and fuel system device, is spaced further away from the cylinder head side toward a lower position. The outboard motor engine described in . (4) Each of the intake manifolds has a curved portion that curves toward the side of the engine body, and the curved portion is configured such that its outward protrusion increases as it reaches lower intake manifolds. The outboard motor engine according to claim 1.