JP3320805B2 - 4-cycle engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for a four-stroke engine, and more particularly to an intake system capable of ensuring combustion stability in lean air-fuel ratio combustion.

[0002]

2. Description of the Related Art In general, a four-stroke engine of a two-valve intake type has two intake passages separated by a partition wall. In this type of engine, the applicant of the present invention has proposed an engine having an intake control valve that allows intake air to be biased toward the top wall side of each of the above intake passages when the intake air amount is low (for example, Japanese Patent Application No. Hei. 263850). In this engine, even when the amount of intake air is small, the flow velocity of the intake flow can be increased to give the intake flow a directionality that flows vertically in the cylinder axis direction.
Thereby, a vertical vortex (tumble) is reliably generated in the combustion chamber, and the combustion stability at a lean air-fuel ratio can be obtained.

[0003] In the proposed device, in order to generate the tumble more reliably, the air is rectified so that the intake air flows along the top wall of each intake passage between the intake control valve and the intake valve opening. A rectifying member is provided.

[0004]

However, in the intake device according to the above proposal, the surface area in the intake passage is increased not only by the partition wall but also by the installation of the intake control valve. Wall flow may occur due to fuel adhering in the intake passage. Further, fuel easily adheres to the partition wall penetration portion of the intake control valve. When this wall flow occurs, the time during which the supplied fuel is actually introduced into the combustion chamber is delayed, and as a result, the air-fuel ratio (A / F) in the combustion chamber fluctuates during acceleration and deceleration. It was found that there was a risk of misfiring at times. In the case where the above-described rectifying member is provided, the surface area of the intake passage further increases by the amount of the rectifying member, and the above-mentioned problem may be concerned. Such a problem tends to occur particularly in the case of a small engine having a fuel injection valve. This is because the fuel is likely to be supplied in an insufficiently vaporized state because the injection angle cannot be set large.

The present invention has been made in view of the above problems, and has as its object to provide an intake device for a four-stroke engine which can more reliably obtain combustion stability at a lean air-fuel ratio. I have.

[0006]

According to a first aspect of the present invention, there is provided an intake system for a four-stroke engine having an intake control valve for deflecting the intake air toward the top wall of the intake passage when the intake air amount is low. A portion of the intake passage near the intake valve opening is partitioned by a partition wall into first and second intake passages arranged in parallel in the camshaft direction. The intake control valve is configured to connect a part of a round bar to the intake passage. It has a valve portion cut out so as to form a continuous surface with the inner surface of the bottom wall, and is inserted into a valve hole formed through the bottom wall of the intake passage in the camshaft direction on the upstream side of the upstream edge of the partition wall. The valve portion is rotatable between a fully open position where the valve portion is immersed in the valve hole and is flush with the inner surface of the intake passage and a fully closed position where the valve portion rises from the valve hole and narrows the intake passage. It is characterized by having. The invention of claim 2 is
According to the present invention, a rectifying member for rectifying the intake air to flow along the top wall of the intake passage is disposed between the intake control valve and the intake valve opening.

[0007]

According to the present invention, since the upstream end of the partition wall is disposed between the intake control valve and the intake valve opening near the intake valve opening, that is, near the intake valve opening, the length of the partition wall is short. Has become. For this purpose, an intake control valve is provided.
Even when the rectifying member is provided as in the invention, the surface area in the intake passage is hardly changed from the conventional one. As a result, it is possible to suppress the generation of the wall flow in the intake passage and to avoid the fluctuation of the A / F, and it is possible to reliably obtain the combustion stability particularly at the lean air-fuel ratio. In addition, the intake control valve has a structure in which the valve is formed by cutting out a part of a round bar, so the simple structure prevents the air flow from leaking from the gap between the valve and the intake passage and ensures It can be biased toward the top wall, and the combustion stability can be improved.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 4 are views for explaining an intake device of a four-cycle engine according to one embodiment of the present invention.

In the drawing, 1 is a water-cooled 4-cycle parallel 4
This is a four-cylinder cylinder engine having a structure in which a cylinder block 3 and a cylinder head 4 are stacked on a crankcase 2 and fastened with head bolts, and a head cover 5 is mounted on an upper mating surface of the cylinder head 4. is there. A piston 7 is slidably inserted into a cylinder bore 3a formed in the cylinder block 3, and is connected to a crankshaft (not shown) by a connecting rod 8.

A lower surface 4a of the cylinder head 4 on the side of the cylinder block 3 has a combustion recess 4b constituting a combustion chamber.
Is recessed. An ignition plug 9 is screwed into the center of the combustion recess 4b, and two intake valve openings 4c and two exhaust valve openings 4d are respectively opened around the ignition plug 9. The openings 4c and 4d are provided in the substantially ring-shaped valve seats 28 and 2 mounted on these portions.
Nine openings are formed respectively. Further, a valve head 10a of the exhaust valve 10 is provided in each exhaust valve opening 4d.
However, the valve head 1 of the intake valve 11 is provided in each intake valve opening 4c.
1a is arranged so as to be able to open and close each opening, that is, to be able to abut against each seat surface of the valve seats 28 and 29. The valve stem 1 of the exhaust and intake valves 10 and 11
Reference numerals 0b and 11b extend obliquely upward in the cylinder axis direction so as to form a predetermined clamping angle when viewed in the cam axis direction, and exhaust and intake lifters 12 and 13 are mounted on upper ends thereof, respectively. Exhaust and intake camshafts 14 and 15 for pressing the lifters 12 and 13 are disposed on the lifters 12 and 13 in a direction perpendicular to the cylinder axis and parallel to each other.

The two exhaust valve openings 4d are led out to the front wall 4f side of the cylinder head 4 through a bifurcated exhaust passage 16, and an exhaust pipe (not shown) is connected to the wall opening 16a of the exhaust passage 16. I have. Each of the intake valve openings 4 c is led out to the rear wall 4 g side of the cylinder head 4 by an intake passage 17. The downstream side of the intake passage 17 is partitioned by a partition wall 19 into first and second intake passages 17a, 17a (see FIGS. 3 and 4). As shown in FIGS. 1 and 4, the partition wall 19 has an upstream end located downstream of an intake control valve 25, which will be described later, that is, in the vicinity of the intake valve opening 4c. Has become shorter. The intake passage 17 extends linearly in a direction perpendicular to the camshaft when viewed in the cylinder axis direction, and is bent in an arc shape from the intake valve opening 4c toward the cylinder rear wall 4g when viewed in the camshaft direction. Later, it extends substantially linearly. Also, the intake passage 17
A throttle body 24 is connected to the rear wall opening 17b, and a throttle valve 24a is rotatably disposed in the body 24. Reference numeral 20 denotes an air cleaner.

The downstream straight portion 17c of each intake passage 17
Has a valve hole 17d formed therethrough in the cam shaft direction.
The valve hole 17d is arranged closer to the cylinder shaft than the cylinder head fastening bolt (not shown), and its axis is located near the bottom wall surface of the intake passage 17, and the inside of the intake passage 17 is substantially halfway. It is formed in a circular shape, and the adjacent intake passage 1
7, 17 communicate with each other. In this valve hole 17d,
An intake control valve 25 for changing the passage sectional area and sectional shape of the intake passage 17 is inserted and arranged. The intake control valve 25 is formed by cutting off a part of a round bar so as to form a continuous surface with the inner surface of the bottom wall of the intake passage 17 to form a valve portion 25a that opens and closes the intake passage 17. The valve portion 25a is immersed in the valve hole 17d to be flush with the inner surface of the intake passage, and the valve portion 25a rises from the bottom wall surface of the intake passage to narrow the intake passage 17 to approximately 1/2.
The intake passage is rotatable between a fully closed position (see FIG. 1) and a cross-sectional shape that is elongated in the cam axis direction. In this case, the valve portion 25a rotates so that the outer peripheral curved surface is located on the upstream side.

A fuel injection valve 26 is mounted on the top wall of the throttle body 24. The fuel injection valve 26 is of a type having two injection nozzles. Each injection nozzle is connected to an upper end of each valve portion 25a of the intake control valve 25 through an injection hole 26a formed in a top wall of the throttle body 24. Portion, that is, a portion extending from the narrowest portion of the intake passage area to the back surface of the valve head 11a of each intake valve 11. Therefore, the fuel is injected substantially equally to each of the intake valves 11, 11, and a part of the injected fuel is supplied to each of the valve portions 25a.
And each of the rectifying members 30 described later.

A rectifying member 30 is provided downstream of each of the intake passages 17a, 17a. Each straightening member 30 extends substantially along the center line of each intake passage 17a, and its upstream end is located above the valve portion 25a of the intake control valve 25 located at the fully closed position. I have. The downstream portion is located closer to the ignition plug 9 than the intake valve 11, and a fixed ring 30 fixed to the downstream end thereof.
a is press-fitted into the inner peripheral surface of the valve seat 27. The flow regulating members 30 are arranged with a gap e therebetween in the intake passage 17 in order to enable press-fitting from the combustion chamber side (see FIG. 3), and it is preferable that the gap e be as small as possible. Reference numeral 30b denotes an escape for avoiding interference with the intake valve 11, and it is preferable that this is as small as possible.

The engine is provided with a control device 40. The control device 40 receives an opening signal a of the throttle valve 24a from the throttle opening sensor 41, a cam angle signal b of the cam shaft 15 from the cam angle sensor 42, and an engine rotation speed signal c from the rotation sensor 43. The fuel injection timing of each fuel injection valve 26 is controlled based on each input signal.

Next, the function and effect will be described. In an operation region where the amount of intake air is small, such as at low speed rotation and low load, a control signal (not shown) from the control device 40 is provided.
As a result, the intake control valve 25 rotates to the fully closed position shown in FIG. Then, the bottom wall side of the intake passage 17 is narrowed by the valve portion 25a of the intake control valve 25, and the intake air is rectified by the rectifying member 30 and the intake passage 17 and the intake passages 17a, 17a,
It flows while being rectified so as to be biased toward the top wall 17a. As a result, the intake air is blown into the combustion chamber at a high speed and directionally, and a tumble is generated as shown by an arrow in FIG. At this time, the injection timing of the fuel injection valve 26 is controlled by the control signal A from the control device 40. The fuel injected from the fuel control valve 26 is introduced from each of the intake passages 17a to the vicinity of the ignition plug 9 through the intake valve opening 4c. Therefore, it is possible to create a state in which the fuel is concentrated in the fuel cell, and it becomes easy to ignite the fuel. As a result, stratified combustion can be performed, and combustion stability during lean combustion can be ensured.

In this case, the intake passages 17a, 1
The surface area inside the intake passage 17 is increased by mounting the rectifying member 30 in the partition wall 7a.
Since the length 9 is short, the surface area in the intake passage 17 hardly changes even when the rectifying member 30 is mounted. Therefore, the amount of fuel adhering to the wall surface in the intake passage 17 does not increase, whereby the generation of the wall flow can be controlled, and the fluctuation of the air-fuel ratio (A / F) in the combustion chamber during acceleration / deceleration can be suppressed. As a result, it is possible to reliably obtain combustion stability particularly at a lean air-fuel ratio. Further, since the left and right intake passages 17a, 17a communicate with each other up to the vicinity of the intake valve opening 4c, there is little difference in the amount of intake air between the intake passages, and the variation in the air-fuel ratio between the intake passages is reduced. You can also.

In the above embodiment, the rectifying member is press-fitted from the combustion chamber side. However, it may be assembled from the outside.
It is also possible to integrate one rectifying member, or the rectifying member may be integrated with the cylinder head by casting or the like. Further, the fuel injection valve 26 may be of a type having a single injection nozzle.
Since 9 is short, the vaporization of the fuel can be improved.

[0019]

As described above, according to the intake system for a four-stroke engine according to the present invention, the upstream end of the partition wall is arranged near the intake valve opening. The valve is cut off partly to prevent the air flow from leaking from the gap between the valve and the intake passage. There is an effect that combustion stability can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a four-stroke engine provided with an intake device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the engine of the embodiment.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

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

FIG. 5 is a sectional view taken along line VV of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 engine 3 cylinder block 4 cylinder head 4b combustion recess 4c intake valve opening 17 intake passage 17a first (second) intake passage 19 partition wall 25 intake control valve 26 fuel injection valve 30 rectifying member

Claims (2)

(57) [Claims] 1. A suction device of a four-cycle engine having an intake control valve to flow the intake air at low intake air quantity biased on the top wall side of the intake passage, the intake valve opening of the intake passage
Neighboring parts were arranged in parallel in the cam axis direction by partition walls
The intake control valve is divided into first and second intake passages.
A part of the round bar forms a continuous surface with the inner surface of the bottom wall of the intake passage.
The intake passage has a notched valve portion
Of the bottom wall of the camshaft in the upstream direction from the upstream edge of the partition wall
The valve part is inserted into the valve hole formed through
The fully open position and the above valve that is immersed in
With the fully closed position where the part rises from the valve hole and narrows the intake passage.
An intake device for a four-cycle engine, wherein the intake device is rotatable between the two . 2. The intake control valve according to claim 1, wherein a rectifying member for rectifying the intake air so as to flow along the top wall of the intake passage is provided between the intake control valve and the intake valve opening. Intake device for 4-cycle engine.