JPH07189713A - Intake device for engine - Google Patents

Abstract

PURPOSE:To burn lean air-fuel mixture in the stratified state by the turning flow of swirl and tumble at the time of low-medium load, and improve fuel consumption. CONSTITUTION:A bent swirl intake port 11a and a straight tumble intake port 11b are communicated with one combustion chamber 6, and the intake ports 11a, 11b are respectively provided with intake valves 13a, 13b opened/closed by valve mechanism. An injector 9 for injecting fuel is disposed at the tumble intake port 11b. The valve mechanism is so constituted as to open the swirl side intake valve 13a first and the tumble side intake valve 13b later with phase shift at the time of lowmedium load and to open both intake valves 13a, 13b simultaneously at the time of high load.

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 generating a swirl flow of a swirl or a tumble in a four-stroke gasoline engine for vehicles by a two-intake-valve system, and more specifically, a lean mixture is stratified by the swirl flow. About burning things.

[0002]

2. Description of the Related Art Generally, when a swirl flow that swirls in a circumferential direction is generated in a cylinder due to an intake air flow at the time of intake, particularly when the engine is operating, especially at low and medium loads, mixing of air and fuel is promoted. . Further, it is known that when a tumble flow swirling in the cylinder axis direction is generated, a turbulent flow is generated at the time of combustion to promote combustion, and both improve the output of the engine, fuel consumption and stability. On the other hand, in addition to the above, in order to improve fuel efficiency, it is effective to use a lean air-fuel mixture and stratify and burn the air-fuel mixture so that the center in the vicinity of the spark plug becomes rich during intake.

Therefore, as an intake device of the engine, two independent straight or helical intake ports are formed by a two intake valve type, and swirl or tumble swirl flow is generated by the intake flow from these intake ports. Further, if not only swirl flow is generated, but also the lean air-fuel mixture can be stratified by these swirl flows, it is expected that fuel efficiency and the like are effectively improved.

Conventionally, there is a prior art disclosed in Japanese Patent Application Laid-Open No. 61-218726 for the intake system of the engine, and in the two-intake-valve system, a fuel injection valve is provided in an intake port for a swirl that always inhales, and the other one is provided. The intake port is equipped with an on-off valve that opens only in the medium and high speed ranges. In addition,
It is shown that a difference is provided in the opening timing of the two intake valves in order to maintain the swirl when inhaling from the two intake ports in the high speed range.

In the prior art of Japanese Patent Laid-Open No. 62-111119, a straight port and a helical port are provided as intake ports, and an intake control valve is provided on the straight port.
A fuel injection valve is arranged upstream of the confluence of both ports. Further, it is shown that an intake bias valve is provided upstream of the fuel injection valve to guide the intake flow toward the elical port side when the intake control valve is closed to prevent fuel from adhering to the intake control valve. .

Further, in the prior art of Japanese Patent Laid-Open No. 2-42122, a straight first intake port and a second intake port for generating a swirl in the cylinder longitudinal direction are provided. And a fuel injection valve is installed in the first intake port to always inhale,
It is shown that the second intake port is provided with an intake control valve that closes only when the load is low.

[0007]

However, in the above-mentioned prior art, all of the two intake valve types have a structure in which only one intake port is used when the load is low. It causes an increase and it is difficult to generate a swirl flow up to the medium load region. Further, since there is only one kind of swirling flow, there is a problem that stratification cannot be performed in the case of a lean mixture.

In view of the above points, an object of the present invention is to stratify and burn a lean air-fuel mixture by swirling flow of swirl or tumble at low and medium loads to improve fuel efficiency and the like.

[0009]

To achieve this object, the present invention is directed to a single combustion chamber in which a bent swirl intake port and a straight tumble intake port are in communication with each other, and the intake valves are respectively connected to the intake ports. In the intake device of the engine, which is provided so as to be opened and closed by the valve operating mechanism,
An injector for injecting fuel is placed in the intake port for tumble, and the valve operating mechanism opens the swirl side intake valve first when the load is low and medium load, and opens and closes the tumble side intake valve separately after opening the phase. It is characterized in that both intake valves are simultaneously opened when loaded.

[0010]

In the present invention having the above-described structure, when the engine is operating at low and medium loads, the valve mechanism first opens the swirl side intake valve first, and the air and EGR gas form a swirl flow from the swirl intake port. It flows near the wall. Next, the tumble-side intake valve opens rearward, and the mixture of air passing through the tumble intake port and the fuel injected by the injector becomes a tumble flow, which flows toward the center of the inside of the air already sucked in the cylinder, As a result, the air-fuel mixture having a rich center portion is stratified by the air-fuel mixture having different air-fuel ratios so that air or the like is arranged around the air-fuel mixture. In the latter half of the compression stroke, the air-fuel mixture stratified by the spark of the spark plug in the combustion chamber is ignited well, and is burned at a high combustion speed due to the disturbance of the swirl and tumble swirling flow, thus improving fuel efficiency and the like. Also, when the load is high, the valve mechanism opens both intake valves at the same time, so that a large amount of air is taken in at one time by the two intake ports to increase the engine output.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. An outline of a two-intake-valve intake system for an engine will be described with reference to FIGS. 1 and 2. Reference numeral 1 denotes an engine body, a piston 4 is reciprocally inserted into a cylinder 3 of each cylinder of a cylinder block 2, and a cylinder head 5
At the top of the cylinder 3, a combustion chamber 6 is provided. The combustion chamber 6 is a roof type, and an ignition plug 8 is attached to the center of the top between the pent roof 7 on the intake side and the pent roof 7 on the exhaust side.

In each cylinder, one intake manifold 10 is connected to two intake ports 11a and 11b.
2 is bifurcated into two, and these intake ports 11a,
11 b communicates with one side of the combustion chamber 6. Then, the intake valves 13a, 1b are respectively connected to the two intake ports 11a, 11b.
3b is installed. On the other side of the combustion chamber 6, there is a fork-shaped 2
The exhaust ports 14a and 14b are communicated with each other, and the exhaust valves 15a and 15 are also connected to the exhaust ports 14a and 14b, respectively.
b is installed. The intake valve 13a, 13b and the exhaust valve 15a, 15b are mounted so that a valve mechanism 20 to be described later can be opened and closed to constitute a four-valve multi-valve engine.

Of the two intake ports 11a, 11b, one intake port 11a is for swirl and is formed by bending in the cylinder circumferential direction, and swirls the intake flow in the cylinder circumferential direction to generate a swirl flow. Is possible. The other intake port 11b is for tumble and is formed in a straight shape in the cylinder radial direction so that the intake flow can be swirled in the cylinder axial direction to generate a tumble flow.

Here, a method of stratifying a lean air-fuel mixture by a swirl flow and a tumble flow at low and medium loads will be described. First, by the valve mechanism 20 (see FIG. 3), the opening timing of the swirl side intake valve 13a is made to open first, and the opening time of the tumble side intake valve 13b is made to open rearward, so that the vicinity of the wall surface in the combustion chamber 6 is closed. A swirl flow can be generated in the, and a tumble flow can be generated near the center. Therefore, by including the air-fuel mixture in the tumble flow, it becomes possible to perform stratification so that the vicinity of the center of the spark plug 8 becomes thicker. Therefore, the injector 9 is arranged so as to direct the fuel toward the tumble intake port 11b, and is controlled so that the injection timing is synchronized with the valve opening timing of the tumble side intake valve 13b at low and medium loads.

The valve operating mechanism 20 on the intake side will be described with reference to FIGS. The valve mechanism 20 can change the phase in the low and medium load regions, and is configured to switch the cams in the low, medium load and high load regions. Therefore, the valve spring 22 is biased in the closing direction by the retainer 21 of the two intake valves 13a and 13b. Also, two low speed rocker arms 23a and 23b cantilevered by rocker shafts 29 for each of the two intake valves 13a and 13b, and two low speed cams 25a and 25 formed on the cam shaft 24.
b, and the low speed rocker arms 23a, 23b are brought into contact with the stem ends of the intake valves 13a, 13b via the adjusting screws 26. The low-speed rocker arms 23a and 23b are provided with rollers 27, which are supported by shafts 28a and 28b, respectively in the middle of the low-speed rocker arms 23a and 23b.
The a and 25b are slidably contacted so as to lift the valve by the rotation thereof. Here, the low speed cams 25a and 25b are formed in a base circle having a large lift portion with a narrow opening angle and a low lift.

Thus, the two intake valves 13a and 13b are
Low speed cams 25a and 25b and rocker arm 23 respectively
It is configured to be opened and closed independently by a and 23b.
Therefore, the low speed cam 25a of the swirl side intake valve 13a and the low speed cam 25b of the tumble side intake valve 13b are formed with a phase shift. That is, the low-speed cam 25a is set such that the valve opening timing is advanced on the advance side in the rotational direction and the low-speed cam 25b is set on the delay side in the rotational direction to be the post-opening timing, so that the valve opening timing can be changed. Has become.

Two low speed rocker arms 23a, 23
One high-speed rocker arm 30 is disposed between b and supported by the rocker shaft 29.
The high-speed cam 32 of the camshaft 24 is arranged so as to face the slipper 31 on the upper part of 0. When the high speed rocker arm 30 is free, the high speed rocker arm 30 is elastically contacted with the high speed cam 32 by the spring means 33, and the high speed rocker arm 30 and the roller shafts 28a of the two low speed rocker arms 23a and 23b.
A switching means 40 is mounted between the switching means 40 and 28b. Here, the high-speed cam 32 is formed with a wide opening angle and high lift in a base circle having a small lift portion.

The switching means 40 is provided immediately below the slipper 31 of the high speed rocker arm 30 and the two roller shafts 28a, 28a.
8b, in the gap between the
2 is inserted in and out of the piston 42, the return spring 43 is biased behind the piston 42, and the hydraulic chamber 41 is communicated with an oil passage 44 such as the rocker shaft 29. The oil passage 44 communicates with the oil passage 46 on the pump side and the drain side via the switching valve 45. When the load is low or medium, the switching valve 45 is switched to the drain side by the signal of the control unit 47, and the return spring 43 operates the piston 42. Retractable high-speed rocker arm 3
Separate 0. Further, when the load is high, the switching valve 45 is operated to the oil supply side, and the piston 42 is projected by the hydraulic pressure to be inserted between the high speed rocker arm 30 and the roller shafts 28a and 28b, so that the high speed rocker arm 30 is connected to the roller shaft 28.
Two low speed rocker arms 23a, 2 via a, 28b
3b and the low speed cams 25a and 25b are separated from the roller 27. The valve mechanism 20 is described in detail in JP-A-3-164511.

Next, the operation of this embodiment will be described. First, when the engine is operating and the load is low or medium, including idling, the switching valve 45 is controlled by the control unit 47.
Operates toward the drain to drain the hydraulic chamber 41 of the switching means 40. For this reason, the piston 42 has the return spring 4
3, the high-speed rocker arm 30 is in a free state in which the high-speed rocker arm 30 merely elastically contacts the high-speed cam 32. Therefore, the roller 27 is rotated by rotating the two low speed cams 25a and 25b.
The two low speed rocker arms 23a and 23b independently swing through the valve, and the two intake valves 13a and 13b can be opened and closed separately.

Therefore, the two low speed cams 25 are used in the intake stroke.
Due to the phase shift of a and 25b, the swirl side intake valve 13a first opens with a narrow opening angle and low lift as shown in FIG. 7, so that air and EGR gas are taken in from the swirl intake port 11a. Air and EGR gas become swirl flow A swirling in the cylinder circumferential direction and flow near the cylinder wall surface. Next, the tumble-side intake valve 13b likewise opens rearward with a narrow opening angle and low lift, so that intake is also made from the tumble intake port 11b, and at this time, the fuel B is injected by the injector 9. Therefore, even a lean air-fuel mixture becomes a tumble flow C swirling in the cylinder axis direction, and flows toward the center of the inside of the air already sucked in the cylinder. As a result, as shown in FIG. 2, the air-fuel mixture is stratified such that the air-fuel mixture D is concentrated around the center and the air E and the like are arranged around it.

When a spark is blown by the spark plug 8 of the combustion chamber 6 in the latter half of the compression stroke, a rich air-fuel mixture D exists near the spark plug 8 and the rich air-fuel mixture D is ignited well by the spark. To be done. Further, the turbulence of the swirling flow of the swirl or tumble causes the flame to rapidly propagate and burn at a high burning velocity, whereby the lean air-fuel mixture is satisfactorily ignited and burned.

When the load is high, the control unit 47 causes the switching valve 45 to move to the oil supply side, and the hydraulic chamber 41 of the switching means 40 is operated.
Hydraulic pressure is introduced into. Therefore, the piston 42 is projected by the hydraulic pressure and the high-speed rocker arm 30 and the two roller shafts 2
High speed rocker arm 30 inserted between 8a and 28b
Is integrally coupled in the swinging direction to the two low speed rocker arms 23a and 23b via the piston 42 and roller shafts 28a and 28b, and the roller 27 is separated from the low speed cams 25a and 25b. Therefore, this time, based on the rotation of the high speed cam 32, the high speed rocker arm 30 and the two low speed rocker arms 23
a and 23b swing together and the two intake valves 13a and 1b
3b opens at the same time. Further, in this case, due to the lift characteristic of the high speed cam 32, the intake valves 13a and 13b are
2 intake ports 11 opened by wide open angle and high lift
A large amount of air-fuel mixture is taken in at once by a and 11b, the charging efficiency is increased and the engine output is increased.

Although the embodiment of the present invention has been described above, the present invention is not limited to this.

[0024]

As described above, according to the present invention,
In an intake system with two intake valve types and a swirl intake port and a tumble intake port, an injector for injecting fuel is arranged in the tumble intake port, and the valve operating mechanism is set to a swirl side intake valve at low and medium loads. Open it first, open the tumble side intake valve to the rear opening, and open and close each separately,
Since both intake valves are configured to open simultaneously when the load is high, the lean air-fuel mixture can be stratified by the swirling flow of the swirl and the tumble to ignite and burn well when the load is low and medium, so that fuel consumption and the like are improved. Further, even at low and medium loads, intake air is taken in from the two intake ports, so intake resistance is reduced. Since no intake control valve is provided in the intake port, the structure and control are simplified.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of an intake device for an engine according to the present invention.

FIG. 2 is a horizontal sectional view of the same.

FIG. 3 is a side view of a valve mechanism.

FIG. 4 is a plan view of the same.

FIG. 5 is a front view of the same.

FIG. 6 is a sectional view of a switching unit.

FIG. 7 is a diagram showing low, medium load, and high load valve lift characteristics.

[Explanation of symbols]

 6 Combustion chamber 9 Injector 11a Swirl intake port 11b Tumble intake port 13a Swirl side intake valve 13b Tumble side intake valve 20 Valve mechanism

Claims (2)

[Claims] 1. An intake air for an engine, wherein a curved swirl intake port and a straight tumble intake port are connected to one combustion chamber, and an intake valve is provided at each intake port so as to be opened and closed by a valve operating mechanism. In the system, an injector for injecting fuel is placed in the tumble intake port, and the valve mechanism is opened at low and medium load with the swirl side intake valve opened first and the tumble side intake valve opened and closed separately to open and close separately. However, the engine intake device is characterized in that both intake valves are opened at the same time under high load. 2. The valve mechanism is such that two low speed cams independently open and close two intake valves at low and medium loads, and a high speed cam simultaneously opens and closes two intake valves at high loads. 2. The intake system for an engine according to claim 1, further comprising switching means for switching, wherein the two low speed cams are set out of phase with each other.