JPH11257158A - Intake a/f control device of multiple cylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly control the intake air A/F of a plurality of cylinders of an engine by a single duty control valve. SOLUTION: In a multiple cylinder engine provided with a plurality of carburetors 33 for independently supplying air-fuel mixture to a plurality of cylinders, a common duty control valve 68 is connected to respective air bleed chambers 64 of a plurality of carburetors 33 through a distribution tube 66. The duty ratio of a pulse to be applied to a coil 76 of the duty control valve 68 is controlled by a duty control unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake A / F control system for a multi-cylinder engine having a plurality of carburetors for individually supplying an air-fuel mixture to a plurality of cylinders.

[0002]

2. Description of the Related Art Conventionally, intake A /
In order to control F, an independent secondary air passage is connected to each of the intake passages of a plurality of carburetors, and a duty control valve is provided in each of the secondary air passages, and a duty ratio of a pulse applied to the secondary air passage is controlled. A device controlled by a unit is known (for example, Japanese Patent Application Laid-Open No. 7-2694).
No. 14).

[0003]

SUMMARY OF THE INVENTION In the above conventional device,
Since an expensive duty control valve is required for each vaporizer, the cost is unavoidable.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the intake A / F of the above-described multi-cylinder engine can be controlled uniformly by using a single duty control valve. An object is to provide an F control device.

[0005]

To achieve the above object, the present invention provides a multi-cylinder engine having a plurality of carburetors for individually supplying a mixture to a plurality of cylinders. A first duty control valve is connected to the air bleed chamber via a distribution tube, and a duty control unit for controlling a duty ratio of a pulse applied to its coil is connected to the duty control valve. Features.

According to the first feature, the amount of air mixed with fuel passing through the main nozzles of a plurality of carburetors can be controlled by duty-controlling a pulse applied to one duty control valve. Thus, atomization of fuel in the air-fuel mixture supplied to a plurality of cylinders of the engine can be promoted, and their A / F can be controlled equally.

In addition to the above-mentioned features, the present invention further comprises three vaporizers, and connects three outlet tubes of a hard material distribution tube to each of the air bleed chambers of the vaporizers. The air outlet of the duty control valve is connected to one inlet tube of the tubes, and the one inlet tube and the three outlet tubes are connected to each other at an angle formed by each outlet tube with respect to the inlet tube at substantially the same angle. The second feature is that they are arranged to be the same.

According to the second feature, the flow path resistance from one duty control valve to a plurality of carburetors can be equalized, and uniform control of the intake A / F of a plurality of cylinders of the engine can be ensured. It can be carried out.

Further, according to the present invention, in addition to the first feature, an LAF sensor for detecting an A / F of exhaust gas flowing through the exhaust passage of the engine and outputting a detection signal proportional to the A / F is provided in the exhaust passage of the engine. The third feature is that the output of the LAF sensor is connected to the input of the duty control unit.

According to the third feature, the exhaust gas A is reduced in a wide operating range from a low load to a high load of the engine.
The intake air-fuel ratio of each cylinder can be controlled in accordance with / F, so that the quality of the exhaust gas of the engine can always be improved.

Further, according to the present invention, in addition to the first feature, the duty control valve accommodates a valve element which is opened when the coil is energized, and the air outlet which is opened and closed by the valve element. A valve cylinder, and an outer cylinder surrounding the valve cylinder so as to form a cylindrical air chamber around the valve cylinder, and a through hole communicating the upper part of the air chamber into the valve cylinder is provided in the valve cylinder. On the other hand, a fourth feature is that the outer cylinder is provided with an air inlet for opening a lower portion of the air outlet to the atmosphere.

According to the fourth feature, even if water is sprinkled from the outside onto the duty control valve and the water enters the air inlet of the valve, the force of the water is attenuated by the air chamber, and Can be prevented from penetrating into the through hole, and hence into the valve cylinder.

Further, the present invention has a fifth feature in that a catalytic converter is interposed in the exhaust passage.

According to the fifth feature, the properties of the exhaust gas can be made better by the purifying action of the catalytic converter.

Still further, according to the present invention, in addition to the third feature, a first catalytic converter is mounted in an exhaust collecting chamber communicating with a plurality of exhaust ports of an engine, and a first catalytic converter is provided in an exhaust passage downstream of the exhaust collecting chamber. A sixth feature is that a second catalytic converter is provided, and the LAF sensor is provided in an exhaust passage between the two converters.

According to the sixth feature, the properties of the exhaust gas can be always improved in a wide operating range from a low temperature to a high temperature of the engine by the purifying action of the first and second catalytic converters. In addition, the LAF sensor can be easily installed using the exhaust path between the two converters.

Further, according to the present invention, in addition to the first feature, the throttle valve of each carburetor is rapidly opened in a flow path connecting each air bleed chamber of the plurality of carburetors and one common duty control valve. A seventh feature is that an acceleration pump for pressurizing the flow path in connection with the operation is connected.

According to the seventh feature, the flow path connecting each air bleed chamber of the plurality of carburetors and one common duty control valve is used for both control of the air bleed amount and acceleration control. Thus, both can be satisfied with a simple configuration.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

FIG. 1 is an overall side view of an outboard motor, FIG. 2 is an enlarged side view of an engine part of FIG. 1, FIG. 3 is an enlarged side view of a main part of FIG.
4 is a sectional view taken along the line 4-4 in FIG. 2, FIG. 5 is a front view of the outboard motor with a part removed, FIG. 6 is a sectional view taken along the line 6-6 in FIG. 3, and FIG. 8 is a longitudinal sectional side view of the duty control valve in FIG. 7, FIG. 9 is an enlarged view of part 9 in FIG. 7, FIG. 10 is a sectional view taken along line 10-10 in FIG. 9, and FIG. FIG. 12 is a partially longitudinal plan view of the tank, FIG. 12 is an upper half view of a section taken along line 12-12 of FIG. 4, and FIG.
FIG. 14 is a sectional view taken along line 15-15 of FIG. 13, FIG. 16 is a sectional view taken along line 15-15 of FIG.
FIG. 16 is a view taken in the direction of the arrow 16 in FIG.

Referring to FIGS. 1 and 2, the outboard motor O includes an extension case 1 and a mount case 2 connected to an upper portion of the extension case 1. A water-cooled in-line three-cylinder four-cycle engine is mounted on an upper surface of the mount case 2. E is mounted and supported with the crankshaft 14 placed vertically. The mount case 2 has a flange portion 2a on the outer periphery thereof. An upwardly open extension case 3 is bolted to the upper surface of the flange portion 2a, and an engine cover 4 is detachably mounted on the upper portion of the extension case 3. You. The engine cover 4, the mount case 2 and the extension case 3 define an engine room 29 for housing the engine E.

In FIG. 2 and FIG.
An annular undercover 5 is mounted between the extension case 3 and the extension case 1 so as to cover the outer peripheral surface of the extension case 3. The under cover 5 is made of an elastic synthetic resin, and has one abutment 5a at a front portion on the hull side. To attach the under cover 5, first, the opening 5a of the extension case 3 is widely opened, the under cover 5 is arranged so as to surround the mount case 2, and an annular step portion 1a formed on the outer periphery of the upper portion of the extension case 1. The lower edge of the under cover 5 is engaged with the upper case, and the upper end of the under cover 5 is connected to the extension case 3 by a tap screw (not shown). Further, the joint ends are fastened with bolts 32 so that the joint 5a of the under cover 5 is closed. Thus, the undercover 5
When the mount case 2 is covered, a continuous surface that connects the outer peripheral surfaces of the extension case 3 and the extension case 1 is formed.

1 to 4 and FIGS. 6 and 12, FIG.
Engine E has cylinder block 6, crankcase 7,
Cylinder head 8, head cover 9, belt cover 10
The cylinder block 6 and the crankcase 7 are mounted on the upper surface of the mount case 2 with the cylinder head 8 facing the rear of the hull. Each of the three cylinders 11 formed on the cylinder block 6 has a piston 1
2 are slidably fitted, and the crankshaft 14 is connected to these pistons 12 through connecting rods 14.
Is supported between the cylinder block 6 and the crankcase 7 in the vertical direction. A valve operating cam shaft 15 is supported by the cylinder head 8 in parallel with the crankshaft 14.
The camshaft 15 is driven by the crankshaft 14 via a timing belt device 16 covered by the belt cover 10.

A drive shaft 17 connected to the lower end of the crankshaft 14 via a transmission gear extends downward inside the extension case 1, and the lower end thereof is moved rearward through a bevel gear mechanism 19 provided inside a gear case 18. Propeller 2 at the end
It is connected to a propeller shaft 21 having zero. A lower end of a shift rod 22 is connected to a front portion of the bevel gear mechanism 19 so as to switch the rotation direction of the propeller shaft 21 between forward rotation and reverse rotation.

A pair of left and right upper arms 23 supporting the mount case 2 and a pair of left and right lower arms 24 supporting the extension case 1 have a swivel shaft 25.
Is fixed, and a swivel case 26 rotatably supporting the swivel shaft 25 is supported by a stern bracket 27 attached to a transom T of the hull via a tilt shaft 28 so as to be vertically swingable.

As shown in FIGS. 3, 4 and 6, on one side of the cylinder head 8, three cylinders 11 corresponding to three cylinders 11 are provided.
The intake ports 30 are open, and three intake pipes 31 individually communicating with the intake ports 30 are fixed to one side surface of the cylinder head 8, and three carburetors 33 are individually provided at their upstream ends. Connected to. The intake pipe 31 is a carburetor 33
Is bent forward (toward the hull) so as to be disposed compactly on one side of the cylinder block 6, and the upstream end is formed so that the liquid fuel attached to the inner wall of the intake pipe 31 naturally flows down to the intake port 30 side. It is inclined upward.

A carburetor body 34 of each carburetor 33 has a butterfly type throttle valve 3 for opening and closing its intake path 34a.
5 and a choke valve 36 located on the upstream side thereof are pivotally supported, and a common intake chamber 37 is connected to the upstream end of the intake path 34 a of all the carburetors 33. The intake chamber 37 has a front end extending forward from the crankcase 7, and an intake port 37 a that opens into the engine room 29 is provided on one side thereof. Therefore, the air that has flowed into the engine room 29 from the air intake port 4a at the top of the engine cover 4 is introduced into the intake chamber 37 from the intake port 37a, and is distributed to the intake paths 34a of the three carburetors 33. You. The intake sound generated in each intake path 34a is attenuated in the intake chamber 37.

In FIG. 6, the cylinder head 8 is provided with an intake valve 39 and an exhaust valve 40 for opening and closing the intake port 30 and the exhaust port 38 corresponding to each cylinder 11, respectively. These are an intake rocker arm 41 and an exhaust rocker arm 42. Is driven to open and close by the camshaft 15 via the. The cam shaft 15 is provided with a pump drive cam 15a. A reciprocating fuel pump 44 is mounted on one side of the cylinder head 8 on the side of the intake port 30, and a push rod 44 a of the fuel pump 44 is attached to the support wall 8 in the cylinder head 8.
a and slidably supported by the pump driving cam 15a.

As shown in FIG. 3, the fuel pump 44 has one inlet pipe 44i and two outlet pipes 44o, and the inlet pipe 44i has a fuel tank (not shown) in the hull.
, A fuel outlet tube 45o connected to the float chambers of the upper two carburetors 33 at one outlet pipe 44o, and a fuel outlet tube 45o connected to the other outlet pipe 45o.
Is connected to a fuel outlet tube 45o connected to the float chamber of the lowermost carburetor 33. Therefore, while the cam shaft 15 is rotating, the pump driving cam 15a drives the fuel pump 44. The pump 44 sucks up fuel from a fuel tank (not shown) and supplies it to the float chamber of each carburetor 33. be able to.

The three carburetors 33 are vertically arranged such that each intake passage 34a is horizontal along the side surface of the cylinder block 6. The valve shaft 35a of the throttle valve 35 of each carburetor 33 is disposed so as to extend horizontally through the intake passage 34a, and has a throttle operating lever 47 at its outer end.
Are fixed, and the three throttle operation levers 47 are interconnected via an interlocking link 48. In addition, each vaporizer 33
The valve shaft 36a of the choke valve 36 is also disposed so as to extend horizontally through the intake passage 34a, and a choke operating lever 49 is fixed to the outer end.
9 are interconnected via an interlocking link 50. Thus, a multiple vaporizer C is constituted by the three vaporizers 33.

In FIGS. 3, 4 and 12, on the side of the cylinder block 6 of the engine E on the carburetor 33 side,
The upper and lower three ribs 51 extending in the axial direction of the cylinder 11
Each rib 51 is formed so as to pass through an intermediate portion and a lowermost portion of the individual carburetor 33, and a breather passage communicating between a crank chamber in the crankcase 7 and a valve operating chamber in the cylinder head 8 is provided inside each rib 51. 52 are formed. And outboard motor O
The three carburetors 33 are arranged close to the side surface of the cylinder block 6 in order to reduce the size of the cylinder. In this case, a dead space is formed above the upper rib 51. And the uppermost vaporizer 33
The throttle sensor 53 is attached to the inner end of the valve shaft 35a of the throttle valve 35. Therefore, the throttle sensor 53 can be attached to and detached from the valve shaft 35a from above the engine E without any hindrance by the ribs 51, so that maintenance performance is good and not only the cylinder block 6 and the vaporization It is protected by being surrounded by the container 33, and can be prevented from being damaged by contact with other objects. The throttle sensor 53 detects the opening degree of the throttle valve 35 as an intake air amount of the engine E, in other words, as a load. The throttle valves 35 of the three carburetors 33 are interlocked with each other as described above. Therefore, one is enough.

Any one of the three throttle operation levers 47 (in the illustrated example, the lowermost throttle operation lever)
A drive arm 56 is supported by a bracket (not shown) provided at the lowermost carburetor 33. Followed arm 55 provided with cam groove 56a provided
Roller 55a is engaged. A throttle drum 57 is fixed to the boss of the drive arm 56, and a control lever (not shown) mounted on the cabin of the hull is provided on the throttle drum 57.
Is connected to the operation wire 58.

When the operation wire 58 is operated in the acceleration direction and the throttle drum 57 is rotated in the direction of arrow A in FIG. 3, the cam groove 5 of the drive arm 56 which rotates together therewith.
The roller 55a moves according to 6a, so that the driven arm 55 can rotate all the throttle operation levers 47 in the opening direction of the throttle valve 35. Also, if the operation wire 58 is operated in the deceleration direction and the throttle drum 57 is turned in the direction opposite to the arrow A, it goes without saying that all the throttle operation levers 47 can be turned in the direction in which the throttle valve 35 is closed.

In FIG. 7, each carburetor 33 is connected to the intake passage 3
A main nozzle 60 is provided at the venturi portion 4a, and communicates with the float chamber 62 below the fuel level via a main jet 61. This main nozzle 60
A large number of air bleed holes 63 are formed in the peripheral wall of the air nozzle, and a cylindrical air bleed chamber 64 is provided so as to communicate with the air bleed holes 63 and surround the main nozzle 60. A communicating tube joint 65 protrudes from the outer surface of the vaporizer 33.

Tube joint 6 of three vaporizers 33
5 is connected to one common duty control valve 68 via a distribution tube 66 and a surge tank 67.

As shown in FIG. 7, FIG. 9 and FIG.
The tube 66 is made of metal or hard synthetic resin.
And one inlet tube 66₁And three exit tubes
Bove 66_Two~ 66_FourAre connected to each other via the connecting member 69.
It is connected to the body. At that time, one inlet tube
66₁And three outlet tubes 66_Two~ 66_FourIs this
At their connection, the inlet tube 66₁For each exit
Tube 66_Two~ 66 _FourMake almost the same angle
In the illustrated example, the angle is approximately 90 °.
ing.

The three outlet tubes 66 _{2 to} 66 _2
4 are each gently bent toward the corresponding vaporizer 33 as needed, and are respectively connected to the tube joints 65 of the three vaporizers 33 via the flexible tubes 70.

On the other hand, the surge tank 67 is made of synthetic resin.
As shown in FIG. 11, a pair of tube joints 67a which are separated from each other, provided with a 67b, while the tube joint 67a is connected to the via flexible joint 71 inlet tube 65 ₁ and the other tube joint 67b Is connected to a tube joint 68a of the duty control valve 68 via a flexible tube 72.
An orifice 73 is formed at a tube joint 67 a of the surge tank 67 connected to the inlet tube 65 ₁ .

In the above, the distribution tube 66 and the flexible tubes 70 to 72 are provided with the air-
A secondary air passage P for supplying the secondary air for / F adjustment is formed, and the surge tank 67 and the orifice 73 are interposed in series with the secondary air passage P.

As shown in FIG. 8, the duty control valve 68
Has a fixed core 75, a coil 76 surrounding the fixed core 75, and a coil housing 77 for accommodating the fixed core 75, and a valve cylinder 78 and an outer cylinder 79 covering the valve cylinder 78 are fixed to one end of the coil housing 77. A valve seat 8 is provided at one end of the valve cylinder 78.
A valve body 82 cooperating with a valve seat 80 is accommodated in a valve cylinder 78, and a movable core 83 formed integrally with the valve body 82.
Are opposed to the fixed core 75, and these two cores 75, 8
A valve spring 84 that biases the valve body 82 in the closing direction, that is, the seating direction with the valve seat 80, is contracted between the three.

The outer cylinder 79 has a joint mounting hole 85 at the end opposite to the coil 76 for press-fitting the tube joint 68a. One end of the valve cylinder 78 is sealed at the inner end of the tube mounting hole 85. It is fitted airtight through the member 86. Except for the fitting portion, the valve cylinder 78 and the outer cylinder 7
9, a cylindrical air chamber 87 is defined.
The air inlet 88 that opens the air to the atmosphere on the coil 76 side is
9, and a through hole 89 is provided in the valve cylinder 78 on the opposite side of the air inlet 88 to communicate the air chamber 87 to the inside of the valve seat 80.

The duty control valve 68 thus configured
Is supported by a bracket 90 fixed to an appropriate position of the engine E, with the tube joint 68a positioned above the coil 76, that is, with the air inlet 88 positioned below the air outlet 81. According to the attitude of the duty control valve 68, even if the splash of seawater or the like entering the engine room 29 suddenly enters the air inlet 88, the splash is immediately attenuated by the cylindrical air chamber 87. As a result, it cannot reach the upper through hole 89 and flows out from the air outlet 81 to the outside. As a result, infiltration of the splash into the valve cylinder 78 can be avoided.

During the operation of the engine E, the duty control valve 6
In step 8, when the coil 76 is excited, the movable core 83 is attracted to the fixed core 75 against the load of the valve spring 84, the valve body 82 is separated from the valve seat 80, and the air outlet 81 is opened. As a result, the air flowing into the air chamber 87 from the air inlet 88 passes through the through hole 89 and the air outlet 81, passes through the surge tank 67, and is distributed by the distribution tubes 66 to the air bleed chambers 64 of the three carburetors 33. Distributed to

In the intake path 34a of each carburetor 33, an amount of intake air corresponding to the opening of the throttle valve 35 flows toward the intake port 30 of the engine E, and the negative pressure generated at the upper end of the main nozzle 60 accordingly. By the main jet 61
The fuel measured in the above is ejected through the main nozzle 60,
The air-fuel mixture is sucked into the corresponding cylinder 11 while generating an air-fuel mixture together with the intake air flowing through the intake passage 34a.

At this time, the air distributed to each air bleed chamber 64 is filled with a large number of air bleed holes 6 of the main nozzle 60.
3, the fuel is mixed with the fuel rising in the main nozzle 60, so that atomization of the fuel can be promoted. If the mixing amount, that is, the amount of air bleed, is increased, the fuel flows through the intake passage 34a. A / F of the generated mixture is diluted,
Conversely, if it is reduced, it can be enriched.

To control the amount of air bleed, a duty control unit 92 is connected to the coil 76 of the duty control valve 68. An input of the duty control unit 92 includes an engine speed sensor 93 for detecting the speed of the engine E,
3, and the output of a LAF sensor 94 (see FIG. 13) for detecting the A / F of the exhaust gas and outputting a detection signal proportional thereto is connected.

Therefore, the duty control unit 92
Are the engine speed sensor 93 and the throttle sensor 5
3. Determine the magnitude of the engine load based on the detection signal of 3,
Further, based on the detection signal of the LAF sensor 94, the A
/ F is determined, the duty ratio of the pulse applied to the coil 76 is determined based on these, the total valve opening time of the valve body 82 is controlled to adjust the amount of air bleed to each carburetor 33, and Atomization of the fuel in the air-fuel mixture supplied from the carburetor 33 to the corresponding cylinder 11 is improved.
F can be set as desired corresponding to the engine load and the A / F of exhaust gas, whereby the output performance of the engine E and the properties of exhaust gas can be improved.

In addition, one common duty control valve 68
Can control the amount of air bleed to a plurality of carburetors 33, thereby simplifying the configuration and contributing to cost reduction. It can be easily performed without causing interference with parts.

The air measured by one common duty control valve 68 is supplied to the three carburetors 3 by the distribution tube 66.
3, one inlet tube 66 ₁ and three outlet tubes 66 constituting the distribution tube 66.
_{2-66 4,} as in the foregoing, in these connecting portions, each outlet tube 66 relative to the inlet tube 66 _{1 2}
Since -66 ₄ angle of it is arranged all at substantially equal, when the air leaving the inlet tube 66 ₁ is diverted into the three outlet tubes 66 ₂ to 66 _4, substantially the same angle with the route, respectively I have to bend. Thereby, the flow path resistance is equalized, and the three outlet tubes 66 _2-
To allow even distribution of air to 66 _4. Moreover, since each outlet tube 66 _{2-66 4} is gently bent toward the carburetor 33 corresponding optionally three outlet tubes 66 ₂ to 66 ₄ from the vaporizer 33 to the corresponding
A difference in the flow path resistance leading to the flow can be prevented as much as possible. Thus, the amount of air bleed to the three carburetors 33 is evenly controlled.

The pulsation of pressure occurs in the flow path from the duty control valve 68 to the air bleed chamber 64 when the pulse applied to the coil 76 is turned on and off, but the common pulsation connecting the distribution tube 66 and the duty control valve 68 is generated. Since the surge tank 67 and the orifice 73 are arranged in series in the flow path, the pressure pulsation can be effectively attenuated by the vibration damping action of the surge tank 67 and the throttle resistance of the orifice 73. Therefore, the generation of vibration and noise due to the pressure pulsation can be prevented, and the surge tank 67 can be made compact by using the orifice 73 together.

Referring to FIG. 4, the fuel pump 44 is mounted on one side of the cylinder head 8 so as to be located behind the carburetor 33 disposed on one side of the cylinder block 6. The mounting piece 95 of the tank 67 is fixed to the rear surface of the head cover 9 with bolts 96 so that 67 is located at the rear end of the engine E. According to such an arrangement, the first space S ₁ defined by one side surface of the cylinder head 8 and the inner surface of the engine cover 4 behind the carburetor 33 is effectively used for installing the fuel pump 44, the second space S ₂ is effectively utilized in the installation of the surge tank 67 that is defined by the surface and the inner surface of the engine cover 4 after the head cover 9, thereby contributing to compactness of the outboard motor O.

Referring again to FIGS. 3 and 7, the drive arm 56 is provided with a push rod 101 which is operated when the drive arm 56 rotates in the acceleration direction, that is, the direction of arrow R.
Are connected via. The acceleration pump 100 has the engine E
A diaphragm housing 102 secured in place at
The driving arm 56 is connected to the diaphragm 105 by a push rod 101. The working chamber 104 is connected to the diaphragm 105 through a one-way throttle valve 106. The distribution tube 66 is connected to an appropriate position. The one-way throttle valve 106 opens when air flows from the working chamber 104 side to the distribution tube 66 side, and provides a throttle resistance to the air flow in the opposite direction.

When the drive arm 56 is rotated in the acceleration direction A, the diaphragm 105 is operated so that the push rod 101 presses the working chamber 104. Working chamber 1
04 is pressurized, the air inside it becomes a one-way throttle valve 1
06 through the distribution tube 66 while opening each vaporizer 3
3 is pressure-fed to the air bleed chamber 64, the air pressure presses the fuel liquid level in the air bleed chamber 64, and the fuel is pushed into the main nozzle 60 from the many air bleed holes 63, and the nozzle 60 Promotes fuel squirting.
Therefore, at the time of the acceleration operation for rapidly opening the throttle valve 35, even when the intake air amount is sharply increased, a delay in increasing the fuel injection amount can be eliminated, and the engine E can be given a good acceleration performance.

On the other hand, at the time of the deceleration operation for rapidly closing the throttle valve 35, on the contrary, since the push rod 101 operates the diaphragm 105 so as to reduce the pressure in the working chamber 104, a negative pressure generated in the working chamber 104 is generated. While the transmission speed is regulated by the one-way throttle valve 106, each carburetor 33
To the air bleed chamber 64. Thereby, fuel ejection from the main nozzle 60 can be suppressed moderately, which can contribute to a reduction in fuel consumption.

As described above, the distribution tube 66 is used as both an air passage for controlling the air bleed amount of each carburetor 33 and an air passage for controlling the acceleration and deceleration of each carburetor 33. In addition, simplification of piping can be greatly achieved.

In FIGS. 12 to 16, an exhaust port 38 formed in the cylinder head 8 corresponding to each cylinder 11 and a vertically long side formed in a side of the cylinder block 6 opposite to the carburetor 33 are formed. The exhaust collecting chamber 110 communicates with the cylinder block 6 and the cylinder head 8 at the joint. The first in the exhaust collecting chamber 110
Is mounted.

A series of exhaust pipes connected to the lower part of the exhaust collecting chamber 110 are provided on one side of the mount case 2 to which the lower surface of the cylinder block 6 is joined and one side of an oil pan 113 which is joined to the lower surface of the mount case 2. At the lower end of the exhaust pipe 114, a connecting flange 116 connected to the upper part of the exhaust box 115 is provided with a bolt 1.
A support piece 118 fixed to the bottom of the oil pan 113 is fixed to the bottom of the oil pan 113 by a bolt 119. The oil pan 113 stores the lubricating oil of the engine E.

The exhaust box 115 has a large-diameter inlet cylinder 120 connected to the ceiling plate 115 a and communicating the exhaust pipe 114 with the exhaust collecting chamber 110, and a bottom plate of the exhaust box 115 side by side with the inlet cylinder 120. 11b, a small-diameter outlet cylinder 121 having an upper end opened to the upper part in the exhaust box 115 and a lower end opened to the extension case 1 is provided, and a second three-way catalyst is provided in the inlet cylinder 120. Converter 112 is mounted.

The exhaust gas discharged from each cylinder 11 to each exhaust port 38 merges in the exhaust collecting chamber 110, passes through the exhaust pipe 114 to the exhaust box 115, and connects the inlet tube 120 and the outlet tube 121. It sequentially passes and is discharged into the extension case 1. Then, the exhaust gas is discharged into the external water through the inside of the propeller 20 together with the cooling water that has finished cooling the engine E.

A first three-way catalytic converter 111 is mounted in the exhaust collecting chamber 110, and a second three-way catalytic converter 112 is mounted in the inlet cylinder 120 of the exhaust box 115. The exhaust gas is effectively purified in a wide operating range from when the engine E is cold to when it is warm, that is, HC, CO ₂ , NOx
Can be removed. In particular, by adjusting the duty ratio of the pulse given to the duty control valve 68 by the duty control unit 92 based on the detection signal of the LAF sensor 94 as described above, the engine E can be operated in a wide operating range from a low load to a high load. , The air-fuel mixture A / F supplied to the engine E of the carburetor 33 is controlled to improve the properties of the exhaust gas.
The load on the engine 112 can be reduced, and their capacity can be reduced, so that the exhaust system can be made compact and can be easily stored in the outboard motor O.

Since the exhaust collecting chamber 110 is opened by separating the cylinder head 8 from the cylinder block 6, the opening causes the first catalytic converter 11 to open.
1 can be easily attached and detached.

On the other hand, in the exhaust box 115, since the upper end of the outlet tube 121 is located above the lower end of the inlet tube 120,
Even if the water level in the extension case 1 rises, it is possible to avoid flooding the inlet tube 120, that is, the second catalytic converter 112, as long as the outlet tube 121 is not submerged.

However, the inlet tube 120 and the outlet tube 121
In the above arrangement, water droplets generated by the first and second catalytic converters 111 and 112 purifying the exhaust gas accumulate at the bottom of the exhaust box 115. To drain it, a drain pipe 122 is attached to the exhaust box 115. The drain pipe 122 is formed by bending a pipe having a diameter much smaller than that of the outlet tube 121 in an inverted U-shape, and one lower end 122 a is arranged so as to be opened close to the upper surface of the bottom plate 11 b of the exhaust box 115. The other lower end 122b is disposed outside the exhaust box 115 so as to open below the bottom plate 11b.

During the operation of the engine E, since the exhaust pressure always acts inside the exhaust box 115, the exhaust box 11
Since there is a pressure difference between the inside of the extension case 1 and the inside of the extension case 1, the first and second catalytic converters 11
Exhaust box 11 along with the purifying action of 1,112 exhaust gas
5 accumulates on the bottom plate 11b, the water passes through the drainage pipe 122 due to the pressure difference and extends through the extension case 1.
The second catalytic converter 11
2 can be prevented from being flooded. Further, since the bent portion of the drain pipe 122 is located above both lower ends thereof, the water level in the extension case 1 rises and the drain pipe 12
As long as the bent portion 2 is not submerged, it is possible to prevent water from entering the exhaust box 115 from the drain pipe 122.

As shown in FIG. 13, the LAF sensor 9
4 is an exhaust pipe 1 formed integrally with the mount case 2
14 is attached as follows. That is, the exhaust pipe 114
A mounting wall portion 114a is formed on a side wall facing the outside of the outboard motor O to be inclined downward and inwardly into the exhaust pipe 114. The LAF sensor 94 is screwed on the mounting wall portion 114a in a substantially vertical posture. The detection portion 94a at the tip of the cover is protruded to the center of the exhaust pipe 114.

The LAF sensor 94 is disposed in an annular space 124 defined by the mount case 2 and the under cover 5 surrounding the mount case 2. If it is too long to fit, LA
An outward bulging portion 5b for receiving the outer end of the F sensor 94 is formed.

As described above, since the mounting wall portion 114a of the exhaust pipe 114 is inclined downward and inwardly into the exhaust pipe 114, the ship of the LAF sensor mounted in the vertical position on the mounting wall 114a. The length of protrusion of the outer unit O to the outside can be kept as small as possible, and contact of the sensor 94 with other objects can be avoided as much as possible, and A / F detection of exhaust gas can be performed reliably. In addition, since the LAF sensor 94 is directed to the outside of the outboard motor O, its mounting wall 1
It can be easily attached to and detached from 14a.

Further, since the LAF sensor 94 is disposed in the annular space 124 inside the undercover 5, the undercover 5 serves as a protective wall, so that the LAF sensor 94 can be prevented from coming into contact with other objects. Further, since the under cover 5 is detachable as described above, the LAF sensor 94 can be easily attached and detached in the detached state.

In FIGS. 12 and 14, reference numeral 12 is used.
Reference numeral 5 denotes a cooling water jacket of the engine E.

Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof. For example, the engine E can be applied to a vehicle.

[0071]

As described above, according to the first aspect of the present invention, in a multi-cylinder engine provided with a plurality of carburetors for individually supplying a mixture to a plurality of cylinders, each air of the plurality of carburetors is provided. One common duty control valve is connected to the bleed chamber via a distribution tube, and a duty control unit for controlling the duty ratio of the pulse applied to its coil is connected to this duty control valve. Duty control of the pulse applied to the control valve promotes atomization of the fuel in the air-fuel mixture supplied to the plurality of cylinders of the engine, and can evenly control the A / F of the mixture. Can be provided simply and at low cost, and can contribute to the downsizing of the entire engine.

According to a second feature of the present invention, three vaporizers are provided, and three outlet tubes of a distribution tube made of a hard material are connected to each air bleed chamber of the vaporizers. The air outlet of the duty control valve is connected to one inlet tube of the distribution tube, and the one inlet tube and the three outlet tubes are connected to each other at an angle formed by each outlet tube with respect to the inlet tube. Since they are arranged so as to be substantially the same, it is possible to equalize the flow path resistance from one duty control valve to a plurality of carburetors, and to surely control the intake A / F of a plurality of cylinders of the engine. Can be.

According to a third feature of the present invention, an LAF sensor for detecting an A / F of exhaust gas flowing through the engine and outputting a detection signal proportional to the A / F is provided in an exhaust path of the engine. Since the output of the LAF sensor is connected to the input of the duty control unit, the A / F of the exhaust gas can be reduced over a wide operating range from low to high engine load.
The intake A / F of each cylinder can be controlled according to the F, so that the properties of the exhaust gas of the engine can always be improved.

According to a fourth feature of the present invention,
The duty control valve accommodates a valve body that is opened when the coil is excited, and has a valve cylinder having the air outlet that is opened and closed by the valve body. And an outer cylinder surrounding the chamber to form a chamber.
A through-hole communicating the upper part of the air chamber into the valve cylinder is provided in the valve cylinder, while the outer cylinder is provided with an air inlet opening the lower part of the air outlet to the atmosphere. Is sprayed, and even if the water enters the air inlet of the valve, the force of the water is attenuated in the air chamber, so that the valve can be prevented from being flooded from the upper through hole.

According to a fifth aspect of the present invention,
Since the catalytic converter is interposed in the exhaust passage of the engine, the properties of the exhaust gas can be further improved by the purifying action of the catalytic converter.

According to a sixth feature of the present invention,
A first catalytic converter is mounted in an exhaust collecting chamber communicating with a plurality of exhaust ports of the engine, a second catalytic converter is interposed in an exhaust passage downstream of the exhaust collecting chamber, and the first catalytic converter is disposed in an exhaust passage between the two converters. Since the LAF sensor is provided, the properties of the exhaust gas can be constantly improved in a wide operating range from a low temperature to a high temperature of the engine, and the LAF sensor can be installed without difficulty.

Further, according to a seventh aspect of the present invention,
An acceleration pump for pressurizing the flow path in conjunction with the rapid opening operation of the throttle valve of each carburetor was connected to the flow path connecting each air bleed chamber of a plurality of carburetors and one common duty control valve. With the common flow path, both the control of the air bleed amount and the acceleration control can be satisfied, which can contribute to simplification of the configuration.

[Brief description of the drawings]

FIG. 1 is an overall side view of an outboard motor according to an embodiment of the present invention.

FIG. 2 is an enlarged side view of the engine unit of FIG. 1;

FIG. 3 is an enlarged side view of a main part of FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a front view of the outboard motor with a part removed.

FIG. 6 is a sectional view taken along line 6-6 of FIG. 3;

FIG. 7 is an overall control system diagram of the vaporizer in FIG. 3;

FIG. 8 is a vertical side view of the duty control valve in FIG. 7;

9 is an enlarged view of a part 9 in FIG. 7;

FIG. 10 is a sectional view taken along line 10-10 of FIG.

FIG. 11 is a partial longitudinal plan view of the surge tank in FIG. 7;

FIG. 12 is an upper half view of a section taken along line 12-12 of FIG. 4;

FIG. 13 is a lower half view of a section taken along line 13-13 of FIG. 4;

FIG. 14 is a sectional view taken along line 1214-14 of FIG.

FIG. 15 is a sectional view taken along line 15-15 of FIG. 13;

FIG. 16 is a view taken in the direction of arrow 16 in FIG. 15;

[Explanation of symbols]

E: Engine 11: Cylinder 33: Vaporizer 35: Throttle valve 38: Exhaust port 64: Air bleed chamber 66: Distribution tube 66 ₁・ ・ ・ Inlet tube 66 _{2 to} 66 ₄・ ・ ・ Outlet tube 68 ・ ・ ・ ・ Duty control valve 76 ・ ・ ・ ・ Coil 78 ・ ・ ・ ・ Valve 79 ・ ・ ・ ・ ・ ・ Outer cylinder 81 ・ ・ ・ ・ Air Outlet 82 ··· Valve element 87 ··· Air chamber 88 ··· Air inlet 89 ··· Through hole 92 ··· Duty control unit 94 ··· LAF sensor 100 ··· Acceleration pump 110: exhaust collecting chamber 111: first catalytic converter 112: second catalytic converter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 19/00 F02M 19/00 K

Claims (7)

[Claims] In a multi-cylinder engine provided with a plurality of carburetors (33) for individually supplying an air-fuel mixture to a plurality of cylinders (11), an air bleed chamber (64) of each of the plurality of carburetors (33) is provided. A common duty control valve (68) is connected via a distribution tube (66), and a duty control unit for controlling the duty ratio of a pulse applied to its coil (76) to the duty control valve (68). (9
An intake A / F control device for a multi-cylinder engine, wherein the device is connected to (2). 2. A distribution tube (6) made of a hard material according to claim 1, comprising three vaporizers (33), and in each of the air bleed chambers (64) of the vaporizers (33).
6) are connected to the three outlet tubes (66 _{2 to} 66 ₄ ), and one distribution tube (66) is connected to one inlet tube (6).
6 ₁ ) The air outlet (81) of the duty control valve (68)
And one outlet tube (66 ₁ ) and three outlet tubes (66 _{2 to} 66 ₄ ) are connected to each of the outlet tubes (66 _{2 to} 66 ₂ ) at their connection with the inlet tube (66 ₁ ). ₄ ) Intake A of a multi-cylinder engine characterized by being arranged so that the angles formed by them are all substantially the same.
/ F control device. 3. An LAF sensor (94) for detecting an A / F of exhaust gas flowing through the exhaust passage of an engine (E) and outputting a detection signal proportional to the A / F in an exhaust passage of the engine (E). ), And the output of the LAF sensor (94) is connected to the input of the duty control unit (92). 4. A valve according to claim 1, wherein said duty control valve (68) houses a valve element (82) that is opened when said coil (76) is energized. A valve cylinder (78) having the air outlet (81) opened and closed by an air cylinder (78), and an outer cylinder (7) surrounding the valve cylinder (78) so as to form a cylindrical air chamber (87) therearound.
9), and the upper part of the air chamber (87) is placed in the valve cylinder (7).
8) A through hole (89) communicating with the inside is provided in the valve cylinder (78), while the outer cylinder (79) is provided with an air inlet (88) for opening the lower part of the air outlet (81) to the atmosphere. An intake A / F control device for a multi-cylinder engine. 5. The intake A / F control device for a multi-cylinder engine according to claim 3, wherein a catalytic converter (111, 112) is interposed in the exhaust passage. 6. The first catalytic converter (11) according to claim 3, wherein a common one exhaust collecting chamber (110) communicating with a plurality of exhaust ports (38) of the engine (E).
1), a second catalytic converter (112) is provided in an exhaust passage downstream of the exhaust collecting chamber (110), and the LAF sensor (94) is provided in an exhaust passage between both converters (111, 112). An intake A / F control device for a multi-cylinder engine, comprising: 7. A fuel cell system according to claim 1, wherein each of the air bleed chambers (64) of the plurality of vaporizers (33) and one common duty control valve (68) are connected to a corresponding one of the flow passages. An intake A / F control device for a multi-cylinder engine, characterized in that an acceleration pump (100) for pressurizing the flow path in connection with a rapid opening operation of a throttle valve (35) of a device (33) is connected.