JP3318390B2 - Intake device for 4-cycle internal combustion engine - 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 internal combustion engine, and more particularly to a four-stroke internal combustion engine having a throttle valve for controlling a passage area of an intake passage connected to an intake valve opening. The present invention relates to an improvement in an intake device that can promote atomization of fuel during a cold period.

[0002]

2. Description of the Related Art There has been proposed a four-cycle internal combustion engine having a fuel injection valve for injecting fuel into an intake passage from the viewpoint of improving fuel efficiency. In this type of four-stroke internal combustion engine, the fuel amount is adjusted by controlling the driving time of the fuel injection valve in accordance with the engine load. Since the flow velocity is low, atomization of the fuel is not performed much, and the fuel easily adheres to the wall surface. As a result, a misfire may occur. This tendency is particularly likely to occur at the time of a cold start (at the time of cold operation) where fuel is difficult to atomize. Therefore, in order to form a mixture having an air-fuel ratio ignitable even in a low-load region at a spark generating position in the combustion chamber, a large amount of fuel is taken in during a low-load operation so as to be richer than the stoichiometric air-fuel ratio. It is supplied in the passage.

[0003]

However, the supply of the extra fuel not only reduces the fuel consumption but also emits harmful exhaust gas such as carbon monoxide (CO) and hydrocarbon (HC). Become.

The present invention has been made in view of the above-mentioned conventional circumstances, and can promote atomization of fuel particularly in a low load region and in a cold state, thereby reducing exhaust gas pollution and improving fuel efficiency.
It is an object of the present invention to provide an intake device for a cycle internal combustion engine.

[0005]

According to a first aspect of the present invention, there is provided an intake system for a four-stroke internal combustion engine including a throttle valve for controlling a passage area of an intake passage connected to an intake valve opening.
A portion of the intake passage upstream of the throttle valve and the vicinity of the intake valve opening communicate with a sub-intake passage having a diameter smaller than that of the intake passage. A variable venturi valve having a piston that protrudes and retracts in the intake passage and directs the intake air flow toward the upstream opening is provided, a control valve for controlling a passage area of the sub intake passage is provided in the sub intake passage, and a fuel injection valve is provided. Arranged upstream of the variable venturi valve in the intake passage so as to inject and supply fuel toward a piston of the variable venturi valve,
Based on signals indicating the engine operating state, such as a throttle valve opening signal, an engine speed signal, and an engine coolant temperature signal,
An engine control device is provided which controls the opening of the control valve so that it opens more when the engine is cold than when it is warm, and controls the fuel injection amount of the fuel injection valve.

According to a second aspect of the present invention, in the first aspect, the throttle valve is held in a fully closed state when the accelerator pedal is in a range from a fully closed position to a predetermined opening position.

[0007]

According to the intake device of the present invention, the upstream opening portion of the sub intake passage is disposed upstream of the throttle valve, and the variable venturi valve having a piston for directing the intake air to the upstream opening is provided. Further, since the fuel is injected toward the piston, when the throttle valve and the variable venturi valve are closed in the low load operation range, the air-fuel mixture surely flows into the auxiliary intake passage. Since the diameter of the sub intake passage is smaller than that of the intake passage, the flow rate of the air-fuel mixture increases, and as a result, atomization of fuel can be promoted in the sub intake passage. Further, since the amount of fuel adhering to the wall surface is reduced, it is not necessary to set the air-fuel ratio to an excessively high concentration. In addition, the passage area of the small-diameter sub intake passage is larger when the engine is cold than when it is warm. This makes it possible to improve the flow of the air-fuel mixture in the sub-intake passage at the time of cooling, thereby further promoting the atomization of the fuel.

According to the second aspect of the present invention, the throttle valve is maintained at the fully closed position in an extremely low load range where the accelerator pedal is extremely depressed, so that the air-fuel mixture flows through the auxiliary intake passage in this operation range. As a result, atomization of the mixture is promoted.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 5 and 7 are diagrams for explaining an intake device of a four-cycle engine according to an embodiment of the present invention. FIG. 1 is a schematic plan view of a four-cycle engine to which the device of the embodiment is applied. FIG. 2 is a partial cross-sectional side view, FIG. 3 is a vertical sectional view of a variable venturi valve of the device of the present embodiment,
4 is an arrow view taken along line IV-IV of FIG. 3, FIG. 5 is an enlarged view of a throttle valve of the present embodiment, and FIG. FIG.

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

A combustion recess 4b constituting a combustion chamber is formed on a lower mating surface 4a of the cylinder head 4 on the cylinder block 3 side.
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 direction and parallel to each other.

Each of the exhaust valve openings 4d extends to the front wall 4f side of the cylinder head 4 in the exhaust passage 16, and an exhaust pipe 16b is connected to the wall opening 16a of the exhaust passage 16. Each of the intake valve openings 4c extends to the rear wall 4g side of the cylinder head 4 in the intake passage 17, and an intake pipe 22 is connected to a wall opening 17a of the intake passage 17.

An air inlet 2 is provided at an upstream end of the intake pipe 22.
3 is formed, and an air cleaner 24 is connected downstream of the air inlet 23. Further, a variable venturi valve 30 is provided in a middle portion of the intake pipe 22. As shown in FIG. 3, the variable venturi valve 30 is provided with a chamber 31 fixed to the top wall of the intake pipe 22 and slidably provided in the chamber 31.
And a piston 32 projecting inward.

The chamber 32 is formed by the piston 32.
Inside, two compartments 31a and 31b are formed. In the compartment 31a, the piston 32 is connected to the intake pipe 2.
2, a coil spring 33 for urging in the closing direction is contracted. The compartment 31a is provided with a bolt 3 mounted on the upper end opening.
6 is closed. A vertically extending through hole 34 is formed in the piston 32, and the inside of the compartment 31 a and the inside of the intake pipe 22 communicate with each other through the through hole 34. Further, a hole 35 is formed in an upper portion of the intake pipe 22, and the inside of the compartment 31 b and the inside of the intake pipe 22 communicate with each other through the hole 35.

The piston 32 on the bottom wall of the intake pipe 22
A sub-intake pipe 40 having a smaller diameter than the intake pipe 22 is connected to a portion opposed to the intake pipe 22. The downstream end opening 40b of the auxiliary intake pipe 40 opens into the intake passage 17 near the intake valve opening 4c. An inclined surface 36 is formed on the upstream side (right side in FIG. 2) of the piston 32, and a lower edge portion 36 a of the inclined surface 36 is located substantially above the center of the upstream end opening 40 a of the sub intake pipe 40. (See FIG. 3). Each sub intake pipe 40 communicates with a communication pipe 41.

A single-hole fuel injection valve 45 for injecting fuel into the intake pipe 22 is mounted upstream of the variable venturi valve 30 of the intake pipe 22. Each fuel injection valve 45 has its injection timing controlled by a fuel distribution pipe 46 controlled by an ECU 46. Further, the ejection hole 45a of the fuel injection valve 45 is directed to the piston inclined surface 36 of the variable venturi valve 30. Further, as shown in a bottom view in FIG. 4, the fuel flow ejected from the ejection hole 45a is set at an injection angle θ such that the front end portion is slightly wider than the upstream end opening 40a.

A throttle valve 25 for controlling a passage area of the intake pipe 22 is provided in each of the intake pipes 22 on the downstream side of the variable venturi valve 30. Each throttle valve 25 is connected to a valve shaft 48 that passes through each intake pipe 22, and the valve shaft 48 is driven by a link 49 that works with an accelerator pedal (not shown). A throttle opening sensor 50 such as a position meter is provided at one end of the valve shaft 48. The amount of rotation of the valve shaft 48, that is, the opening of the throttle valve 25, is detected by the throttle opening sensor 50. The signal is input to the ECU 46.

The throttle valve 25 has a disc-shaped or elliptical-shaped valve plate. The valve plate has a width (diameter or long axis) perpendicular to the valve shaft 48 as shown in FIG. ) A
Are formed smaller than the diameter D of the intake pipe 22.
Therefore, the throttle valve 25 can rotate 90 ° or more, and the operating angle is set to 90 ° + α. By setting the operating angle of the throttle valve 25 to a large value in this manner, the operation shown in FIG.
As shown by the solid line in FIG.
From α ° to about 13 °, the opening area of the intake pipe 22 hardly increases even if the throttle valve 25 rotates. In FIG. 7, the valve opening degree of 0 ° indicates a state in which the throttle valve 25 is in the fully closed position (the position indicated by the solid line in FIG. 5).

In the intake pipe 22 near the upstream of the throttle valve 25, there is formed an oil trap annular groove 51 for catching fuel injected from the fuel injection valve 45 and adhering to the wall near the throttle valve 25. ing. Intake pipe 22
On the bottom wall side, a bypass passage 52 communicating between the annular groove 51 and the sub intake pipe 40 is provided. With this configuration, the fuel that has not been introduced into the auxiliary intake pipe 40 from the opening 40 a of the intake pipe 22 is supplied to the annular groove 51 and the bypass passage 5.
2 and is collected in the sub intake passage 40. As a result, it is possible to prevent the fuel accumulated in the intake pipe 22 from flowing into the wall surface and being supplied into the combustion chamber.

A control valve 42 for controlling the passage area of the sub intake pipe 40 is provided in the middle of the sub intake pipe 40. Under the control of the ECU 46, the control valve 42 rotates the sub-intake passage 40 to the open side when the engine is cold and to the closed side when the engine is warm.

In this embodiment, in an extremely low load operation range, the throttle valve 25 is kept fully closed even when the accelerator pedal is depressed. On the other hand, there are cases where it is desired to increase the output to some extent even in a low load range. In such a case, in the low load operation range, the control valve 42 may be configured to open more as the accelerator pedal depression amount increases in accordance with the depression amount of the accelerator pedal.

The engine 1 is controlled by the ECU 46 as described above.
The ECU 46 has an engine speed,
The ECU 46 controls the fuel injection valve 45, the control valve 42, and the like based on the input signals of the throttle opening, the engine coolant temperature, and various accessories.

Next, the operation of the above embodiment will be described.
In the low-load operation range, the position where the throttle valve 25 is turned slightly further from the fully-closed position (the position indicated by the one-dot chain line in FIG. 5).
Put in. The variable venturi valve 30 is located on the upstream side (atmospheric pressure side) of the throttle valve 25, and each of the compartments 31a and 31b of the variable venturi valve 30 has a hole 3a.
It communicates with the inside of the intake pipe 22 via 4 and 35. Accordingly, the piston 32 is urged downward by the spring force of the coil spring 33 to close the intake pipe 22 (FIG. 3).
Move to the (solid line position) or small opening position.

Further, even if the throttle valve 25 is rotated from the fully closed position to the open side in this low load range, as described above, the opening area of the intake pipe 22 is limited to the range from -α ° to about 13 °. Hardly changes, so that the amount of intake air in the intake pipe 22 hardly increases.

On the other hand, a throttle opening detection signal from the throttle opening sensor 50 is input to the ECU 46,
From the detection signal, the ECU 46 determines that the operation area is in the low load area. Similarly, the engine coolant temperature signal is also sent to the ECU.
The ECU 46 determines from the liquid temperature signal whether the engine is in a warm-up operation or in a cold operation.

If it is determined that the engine is in the cold operation, the ECU 46 fully opens the control valve 42 (see the broken line in FIG. 7). Set to the closed side (see the broken line in the figure). As a result, the flow of the air-fuel mixture in the auxiliary intake pipe 40 is improved during the cold operation, and as a result, the atomization and vaporization of the fuel during the cold operation can be further promoted.

As described above, when the throttle valve opening is -α
From ゜ to about 13 °, the opening area of the intake pipe 22 is hardly changed by the opening movement of the throttle valve 25 in a substantially fully closed state, and the opening area of the entire intake system is changed by opening and closing the small-diameter auxiliary intake pipe 42. As a result, the opening area of the entire intake system can be gradually increased. Thus, the intake air amount can be smoothly increased, and the control of the engine output can be easily performed. In addition, since the opening area is kept almost completely closed, the ratio of the air-fuel mixture flowing through the sub-intake pipe 42 is increased, whereby the atomization is improved and the combustion state is improved.

When the fuel is injected from the fuel injection valve 45 in this state, the fuel advances through the intake pipe 22 and collides with the piston inclined surface 36 of the variable venturi valve 30. Then, the fuel spreads in a thin film shape on the inclined surface 36, and together with the high-speed airflow moving downward along the inclined surface 36, the fuel flows into the auxiliary intake pipe 4.
And flows into the auxiliary intake pipe 40 through the upstream end opening 40a.

Since the auxiliary intake pipe 40 has a smaller diameter than the intake pipe 22, the fuel flowing into the auxiliary intake pipe 40 increases the flow velocity in the auxiliary intake pipe 40, thereby promoting the atomization of the fuel. You. The fuel is supplied to the downstream end opening 40 of the sub intake pipe 40.
b flows into the intake passage 17 near the intake valve opening 28,
The gas flows into the combustion chamber through the intake valve opening 28. As a result, an ignitable air-fuel mixture can be formed at a spark generating position in the combustion chamber, whereby the emission of harmful exhaust gases such as carbon monoxide (CO) and hydrocarbons (HC) can be suppressed. It is possible to reduce pollution and improve fuel efficiency.

In addition, since the auxiliary intake pipe 40 is opened wider in the cold state than in the warm state by the control of the control valve 42,
The flow of the air-fuel mixture in the auxiliary intake pipe 40 can be improved, and the atomization of fuel at the time of cooling can be further promoted.

The fuel injection start timing in the low load operation range is preferably performed immediately before the intake stroke or during the intake stroke. This is because the atomization of the fuel can be promoted by utilizing the increase in the intake flow velocity.

In the medium load operation range, the throttle valve 2
When 5 opens, a flow velocity is generated in the intake pipe 22 downstream of the throttle valve. Since the passage area on the bottom wall side of the mounting portion of the variable venturi valve 30 in the intake pipe 22 is narrowed by the piston 32, the flow velocity in the intake pipe 22 is larger on the bottom wall side than on the top wall side, As a result, the bottom wall side has a negative pressure.

On the other hand, each of the compartments 31a and 31b of the variable venturi valve 30 communicates with the inside of the intake pipe 22 through the holes 34 and 35, respectively. The inside of 31b is in a higher pressure state. As a result, the piston 32 moves upward against the spring force of the coil spring 33, and opens the intake pipe 22 (see the dashed line in FIG. 3). In this state, the inclined surface 36 of the piston 32
The line extending downward is still the opening 40 of the sub intake pipe 40.
a. The fuel injected from the fuel injection valve 45 collides with the piston inclined surface 36 of the variable venturi valve 30 and is atomized and moves downward, and partly passes through the upstream end opening 40 a of the sub intake pipe 40 and the sub intake air. The gas flows into the pipe 40 to be atomized, and the rest is atomized and atomized by the high-speed airflow passing through the bottom wall of the intake pipe 22 to flow into the combustion chamber from the intake passage 17.

In the high load operation range, the throttle valve 2
5 is in the fully open position, whereby the flow velocity in the intake pipe 22 further increases, and the negative pressure on the bottom wall side in the intake pipe 22 further increases. As a result, the piston 32 is further raised, and the lower end surface of the piston inclined surface 36 coincides with the top wall surface of the intake pipe 22 or is located at the fully open position where the inclined surface 36 slightly projects. As a result, most of the fuel injected from the fuel injection valve 45 flows into the combustion chamber from the intake passage 17 while being atomized while flowing through the intake pipe 22 at high speed.

In the case of rapid acceleration, that is, when the throttle 25 is suddenly opened, the intake air generally flows into the cylinder with almost no delay, whereas the fuel flows with a slight delay. A phenomenon occurs in which F (air-fuel ratio) momentarily decreases and then increases. To prevent this,
In the present embodiment, a delay characteristic is provided on the open side of the variable venturi valve 30 so that the intake air gradually increases during rapid acceleration.

Further, when the vehicle shifts from a high load region to a rapid deceleration state, generally, the negative pressure on the downstream side of the throttle valve 25 increases, so that the fuel adhering to the intake pipe 22 evaporates rapidly. The A / F of the air becomes over-concentrated and exhausts harmful CO and HC. In order to prevent this, in the present embodiment, at the time of sudden deceleration, the control valve 42 controls the auxiliary intake pipe 40 to open to introduce air into the combustion chamber. This can prevent the A / F of the air-fuel mixture from becoming excessively concentrated, and
/ F.

When the deceleration operation is continuously performed, the negative pressure in the cylinder generally increases, so that engine oil flows between the piston 7 and the cylinder bore 3a, and between the valve head 11a and the intake valve opening 4c. It may leak from between. In order to prevent this, in the present embodiment, the control valve 42 is opened during the continuous deceleration operation, whereby fresh air is introduced into the cylinder to suppress an increase in the negative pressure.

As described above, in this embodiment, in the low-load operation range, the fuel is made to pass through the sub-intake pipe 40 having a smaller diameter than the intake pipe 22, so that atomization of the fuel can be promoted, thereby causing harmful effects. Exhaust gas emission can be suppressed and fuel efficiency can be improved. In addition, since the opening and closing of the intake pipe 22 is performed by the variable venturi valve 30 of the piston type, fuel can be satisfactorily distributed to the intake pipe 22 and the auxiliary intake pipe 40 according to the engine load. Further, since the auxiliary intake passage is opened more greatly in the cold state than in the warm-up state, it is possible to promote the atomization of the fuel particularly in the cold state.

In the above embodiment, the variable venturi valve 30 is driven by using the negative pressure in the intake pipe 22. However, the application of the present invention is not limited to this. For example, a link mechanism may be provided in conjunction with the opening movement of the throttle valve 25, and the variable venturi valve 30 may be driven by the link mechanism. Further, an actuator (for example, a stepping motor) for the piston 32 is provided, and the opening degree of the piston 32 corresponding to the opening degree of the throttle valve 25 is registered in the control unit (ECU) in advance. The actuator may be driven so as to have a desired piston opening.

The throttle valve 25 is not limited to the one shown in FIG. 5, and as shown in FIG.
A diameter larger than the diameter D of 2 can be used, but in this case, it is necessary to electrically control the rotation of the valve so that the valve does not open at a low load.

[0041]

As described above, according to the intake system for a four-stroke internal combustion engine according to the present invention, the variable venturi valve for directing the intake air flow is provided at the upstream opening of the auxiliary intake passage having a smaller diameter than the intake passage. The fuel is injected toward the piston, and the passage area of the auxiliary intake passage is made to be larger at the time of cooling than at the time of warm-up, so that atomization of the fuel can be promoted particularly at the time of cooling, and thereby the exhaust gas is exhausted. This has the effect of reducing gas pollution and improving fuel efficiency. According to the second aspect of the present invention, the throttle valve is prevented from being opened when the load is extremely low, so that the ratio of the air-fuel mixture flowing through the auxiliary intake passage is increased, which also promotes atomization of the fuel.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a four-cycle engine to which an intake device according to an embodiment of the present invention is applied.

FIG. 2 is a partial sectional side view of the engine of the embodiment.

FIG. 3 is a longitudinal sectional view (a sectional view taken along line III-III in FIG. 4) of the variable venturi valve of the intake device.

FIG. 4 is a view taken along the line IV-IV in FIG. 3;

FIG. 5 is an enlarged view of a throttle valve of the intake device.

FIG. 6 is a diagram showing a modification of FIG. 5;

FIG. 7 is a diagram for explaining a relationship between a valve opening degree and an opening area of the intake device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 22 Intake pipe 25 Throttle valve 28 Intake valve opening 40 Secondary intake pipe 40a Secondary intake pipe opening 42 Control valve 45 Fuel injection valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02B 29/00 F02D 13/02 F02M 69/00 F02M 69/00 310 F02M 69/00 360

Claims (2)

(57) [Claims] 1. An intake system for a four-stroke internal combustion engine including a throttle valve for controlling a passage area of an intake passage connected to an intake valve opening, wherein the intake passage is upstream of the throttle valve.
The side part and the vicinity of the intake valve opening are smaller in diameter than the intake passage.
And the upstream opening of the auxiliary intake passage is shaped.
The suction passage formed in the intake passage portion
Variable with a piston directing airflow to the upstream opening
A venturi valve is provided, and the auxiliary intake passage is provided in the auxiliary intake passage.
Provide a control valve to control the passage area of the road, and raise the fuel injection valve
Upstream of the variable venturi valve in the intake passage.
Inject fuel into the variable venturi valve piston.
The throttle valve opening signal and engine speed signal
And engine operating status such as engine coolant temperature signal
Control valve opening based on the
When the fuel injection
An intake device for a four-stroke internal combustion engine, comprising: an engine control device for controlling a fuel injection amount of an injection valve. 2. The intake system for a four-stroke internal combustion engine according to claim 1, wherein the throttle valve is held in a fully closed state when the accelerator pedal is in a range from a fully closed position to a predetermined opening position. .