JPS61215422A - Multi-intake valve engine - Google Patents

Abstract

PURPOSE:To improve both fuel consumption and power generation by providing a primary helical intake port, a secondary straight intake port and a third intake port including a fuel injection valve and devising the opening timing of the intake valve of each of these intake ports. CONSTITUTION:There are provided a primary intake port 1 which is helical port and enables generation of swirl in a combustion chamber 3, a secondary intake port 4 which is formed straight and includes an intake control valve 6 that is to be closed as the low-speed low-load time, and a third intake port 7 which is positioned between both the ports 1 and 4 and has a relatively small cross section. Said ports 1, 4, and 7 open to the combustion chamber 3 via intake valves 2, 6, and 8, respectively and a fuel injection valve 9 is disposed in the third intake port 7. The opening timing of the third intake valve 8 is set later than that of the primary intake valve 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to intake control in a so-called multiple intake valve engine, which includes a plurality of intake valves.

[Conventional technology]

With the trend towards higher output, various types of dual intake valve engines have been developed. One such dual intake valve engine is one that has an improved helical intake port that can generate swirl within the combustion chamber. As the name suggests, a helical intake port is formed in a spiral shape, and improves combustion by generating swirl within the combustion chamber. However, it has been recognized that when the load is high, the special shape increases the intake resistance and tends to reduce the filling efficiency. In order to improve this, a second intake port and a second intake valve are provided, and this second intake port is further provided with an intake control valve, and when the load is low, this intake control valve is closed. Taking advantage of this, high rotation speed is achieved.

When the load is high, this intake control valve is opened so that air can be introduced into the combustion chamber from both the first helical intake port and the second port.

On the other hand, in order to improve combustion and improve fuel efficiency, it is necessary to expand the maximum value of the combustible air-fuel ratio, that is, the lean limit of combustion. It is known that it is better to make the layer thinner (hereinafter referred to as stratification).

In the past, many proposals have been made to improve fuel efficiency by stratifying engines with multiple intake valves (Japanese Patent Publication No. 47-24041, Japanese Patent Publication No. 52-1)
6521, Japanese Utility Model Publication No. 57-52331, Japanese Patent Application Laid-open No. 52-32406, and Japanese Patent Application Laid-open No. 56-96118).

[Problem that the invention seeks to solve]

The conventionally known device as described above suggests the basic conditions for stratified combustion in a multiple intake valve engine, but when an engine is actually manufactured, it is possible to achieve a lean mixture by stratification at low load and low rotation speeds, which is the practical area. The above-mentioned known devices are still not sufficient to achieve the two objectives of achieving low fuel consumption and low emissions through combustion of air, and obtaining high output under high load and high rotation speeds.

The present invention is capable of achieving both the combustion of a lean air-fuel mixture through stratification in the low-load, low-speed range and high output in the high-load, high-speed range, achieving low fuel consumption, low emissions, and high output. It is an attempt to provide a practical dual intake valve engine.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a first intake port that is always open to generate a swirl in the intake air supplied into the combustion chamber, and an intake port that is opened only in the high-load, high-speed operating range of the engine. a second intake port having a control valve and supplying straight intake air into the combustion chamber;
and a third intake port provided with a fuel injection valve. The third intake valve is connected to the combustion chamber through second and third intake valves, and the opening timing of the third intake valve is delayed from the opening timing of the first intake valve.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, l is a first intake port which is connected to the combustion chamber 3 through a first intake valve 2, and which is connected to the combustion chamber 3 through a first intake valve 2, and which is connected to a combustion chamber 3 near the first intake valve 2, known as a helical port. The air sucked through this port 1 causes a swirl within the combustion chamber 3 as shown by arrow A. A second intake port 4 is connected to the combustion chamber 3 via a second intake valve 5 and has a straight shape. An intake control valve 6 is disposed in the second intake port 4, and when the engine speed and load are low, the second intake port 4 is closed and the engine speed is reduced.

When the load is large, the second intake port 4 can be opened. This intake valve 6 is driven to open and close by an appropriate actuator (not shown), and when the engine is operated at low speed and low load, this second intake passage 4
When the engine is operated at high speed and high load, the second intake passage 4 is opened. The actuator has a diaphragm chamber partitioned by a diaphragm into an atmospheric pressure chamber and a variable pressure chamber, and a negative pressure (for example, negative pressure in the first intake passage 1) is applied to the variable pressure chamber depending on the operating state of the engine. Alternatively, a negative pressure control actuator that controls the opening and closing of the sub-intake control valve 6 by introducing atmospheric pressure is used.

This actuator is controlled by an ECU (electronic control unit), which will be described later. A third intake port 7 is connected to the combustion chamber 3 via a third intake valve 8.

The third intake port 7 is located between the two ports 1.4 and has a relatively small passage cross-sectional area, and therefore the third intake valve 8 is also small compared to the other intake valves 2 and 5.

A fuel injection valve 9 is arranged in this third intake port 7,
This fuel injection valve 9 is controlled by an ECU 19.

Said 1st. The positional relationship between the second and third intake valves 2.5 and 8 is as shown in FIG. The second intake valves 2 and 5 are arranged so as to be located outside the straight lines C and C connecting the respective centers of the second intake valves 2 and 5. Reference numeral 11 denotes an ignition plug, which is disposed approximately at the center of the cylinder surrounded by an intake valve 2.5.8 and two exhaust valves 13.14. Furthermore, a masking 12 that also serves as a squirrel is provided on the cylinder wall side of the lower surface of the cylinder head around the third intake valve 8, so that the injected fuel is guided in the direction of arrow B and floats around the ignition plug 11. It is being done. 15 is an exhaust port. EGR port 16 is branched from exhaust port 15 and EGR
It is connected to the third intake passage 7 via a valve 17.

Referring to FIG. 2, piston 20 has a cavity 21 formed in its top. The shape of the cavity 21 is such that the ignition plug 11 is located inside the inscribed circle 22 of the cavity 21 at the end opposite to the third intake valve 8, as shown in FIGS. The flame is shaped so that the flame propagates smoothly along the swirl shown by arrow A in the figure.

Further, the first and second intake valves 2 and 5 are of a swing arm type in which they are driven with a pivot center 24 as a fulcrum via a rocker arm 23, as shown by the chain line in FIG. This is because it is necessary to increase the lift amount in order to obtain high output, and the maximum valve lift amount C (Fig. 5) is b/a times the maximum cam lift amount (a is the pivot center 2
The distance b from 4 to the contact point of the rocker arm 23 with the cam 25 (b) can be increased by the distance between the pivot center 24 and the tip of the rocker arm 23 (see FIG. 2), that is, by the amount of the rocker. On the other hand, the third intake valve 8 has a valve lifter 18 and a cam 25, as shown by the solid line in FIG.
Direct drive system. This means that the maximum valve lift d (Fig. 5) of the third intake valve 8 is an appropriately small value (for example, d
This is because the direct drive method allows the third intake valve 8 to stably obtain a small lift curve. 26 is a water temperature sensor attached to the cooling waterway, and its signal is sent to the ECU 19.

Said 1st. The operating timing of the second and third intake valves 2.5 and 8 and the fuel injection valve 9 is shown in FIG. As shown in its operating curve Y, the opening timing of the third intake valve 8 is later than that of the first and second intake valves 2 and 5, whose operating curves are indicated by X, and at a timing F near the center of the intake stroke. The valve is opened and closed at approximately the same time G as the first and second intake valves 2 and 5 (E for the first and second intake valves). Also, the fuel injection valve 9
As shown in Z in the figure, the injection start timing (■) is controlled to advance or retreat with respect to the rotation speed and load so that the injection end timing H is before or after the opening timing F of the third intake valve 8. .

The operation of this embodiment will be explained next.

In the low-load, low-speed range of the engine, as shown in FIG. 5, first and second intake valves 2 and 5 are opened at D, and second intake port 4 is closed by intake control valve 6. Therefore, air is sucked into the combustion chamber 3 through the first intake valve 2, and a stable swirl A is generated. Subsequently, the third intake valve 8 is opened approximately at the center F of the intake stroke. Fuel is injected into the third intake port 7 from the fuel injection valve 9 according to a signal from the ECU 19 at an injection timing such that the fuel injection end timing H is almost the same as the opening timing F of the third intake valve 8. be done. Therefore, the rich air-fuel mixture 30 (Fig. 1) flows into the combustion chamber 3 from the third intake valve 8 in the latter half of the intake stroke, and the squishy provided around the third intake valve 8 also functions as Due to the effect of masking 12, this rich mixture 30
goes towards the ignition plug 13, rides the swirl A, and moves towards the arrow B.
is inhaled in the direction.

In the first half of the intake stroke, only air is taken in through the first intake valve 2 and remains near the top surface of the piston 20, and in the second half of the intake stroke, a rich air-fuel mixture is taken in through the third intake valve 8 and remains near the cylinder head. It turns out.

Also, the third intake valve 8 opens only in the latter half of the intake stroke, so
The flow sucked in from there is relatively weak and the first intake valve 2
A stable swirl is maintained without almost disturbing the swirl A generated in the above. This stratified state is stably maintained by swirl A until the compression top dead center, so at the time of ignition, a rich air-fuel mixture is floating near the ignition plug 9, causing the overall air-fuel ratio to be lean, or a large amount to be released from the EGR port 16. of
Even when EGR gas is introduced into the combustion chamber 3, stable ignition and flame propagation are achieved.

In addition, the fuel injection timing is controlled by the ECU 19 according to the engine speed and load so that the end timing H is close to the opening timing F of the third intake valve 8, so that most of the injected fuel is After being evaporated in the intake port 7 of No. 3, it is inhaled into the combustion chamber 3, which prevents deterioration of emissions and allows the injection time 2 to be determined based on the latest intake air amount signal. An accelerated response can be obtained.

Furthermore, the first. The second intake valve 2.5 is the rocker arm 2
Since the third intake valve 8 is directly driven by the cam 24 via the valve lifter 18, opening/closing control suitable for the maximum valve lift amount of each intake valve is possible, and the above three This prevents the valve lifters from interfering with each other as would be the case if all the intake valves were directly driven, and the bivofts 23 would not interfere with each other or with the spark plug 11 as would be the case if all the intake valves were of the swing arm type. Problems can be eliminated.

Further, since the EGR gas is not supplied to the surge tank as in the conventional case but is supplied to the third intake port, NOx can be reduced more effectively.

FIG. 6 is a graph showing the relationship between the opening timing F of the third intake valve 8 and the lean limit air-fuel ratio (A/F) in a low-load, low-speed range. As shown in the figure, the lean limit is greatly influenced by the opening timing of the third intake valve 3, and the best timing is when the opening timing is approximately in the middle of the intake stroke [90° after intake top dead center (TDC)]. Become. Therefore, considering that the best timing for opening the third intake valve 8 varies slightly depending on the engine speed and load, the opening timing of the third intake valve 8 is set at ±20° CA (crank angle) at the center of the intake stroke.
It is preferable to set the valve timing at around 70' to 110 @) after intake top dead center (TDC).For more optimal control, only the third intake valve 8 is provided with a variable valve timing mechanism, and the engine speed is , it can also be variably controlled depending on the load.

Figure 7 shows the relationship between the closing timing G of the third intake valve 8, low-speed torque, and high-speed torque, when the closing timing is the same as that of the first or second intake valve. It is shown as a ratio when the shaft torque is 1.0.

According to the figure, when the closing timing G of the third intake valve 8 is advanced, the operating angle of the third intake valve becomes smaller, making it impossible to obtain sufficient lift, and slowing down (which results in a decrease in not only low speed but also high-speed torque). Therefore, the closing timing G of the third intake valve 3 is set to the first.
It is preferable that the timing is approximately the same as the closing timing E of the second intake valves 2 and 5, or within about 40'' crank angle even if it is delayed.

Incidentally, when the engine is cold, if the fuel injection timing is set to a time other than the intake stroke using the signal from the water temperature sensor 26, deterioration of emissions can also be prevented.

Further, the same effect can be obtained by inhaling a lean mixture instead of air through the first intake valve 2.

8 and 9 show other embodiments of the invention.

In this embodiment, the shape of the cavity 21 provided in the upper part of the piston 20 is such that the ignition plug 11 is in contact with the outside 21a of a circle 22 inscribed in the cavity 21 and is disposed within the cavity 21. By forming the cavity 21 in this manner, the ignition plug 13 can avoid being hit directly by the swirl A, thereby improving ignition performance.

On the other hand, since the intake control valve 6 is opened in the high speed and high load range of the engine, the first. Second. Third intake valve 2.5.8
This makes it possible to draw a large amount of fresh air into the combustion chamber, resulting in good shaft torque and output. Furthermore, stratification improves combustion and suppresses the occurrence of non-king.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration 1, the so-called stratification, in which the air-fuel mixture is rich around the spark plug and lean on the piston side, is good and stable in the low-load and low-speed range of the engine. Therefore, a large amount of EG
R combustion is also possible, making it possible to achieve low fuel consumption and low emissions.

In addition, good shaft torque and shaft output can be effectively obtained in the high load, high rotation range of the engine.

In this way, it is possible to provide a practical dual-intake valve engine that can obtain the desired combustion state and high output in the entire operating range from the low-load, low-speed range to the high-load, high-speed range.

[Brief explanation of drawings]

FIG. 1 is a plan view of the first embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of the main part of the same embodiment, FIG. 3 is a plan view showing the shape of the cavity of the above embodiment, and FIG. FIG. 3 is a longitudinal section of the cavity, and FIG. 5 is a graph showing the operating timing and drift of each intake valve and the injection timing of the fuel injection valve. FIG. 6 is a graph showing the relationship between the opening timing of the third intake valve and the lean limit;
FIG. 7 is a graph showing the relationship between the closing timing of the third intake valve and the shaft torque, FIG. 8 is a plan view showing the shape of the cavity of the second embodiment of the present invention, and FIG. 9 is the graph shown in FIG. FIG. 1... First intake port, 2... First intake valve, 3...
...Combustion chamber, 4...Second intake port, 5
...Second intake valve, 6...Intake control valve, 7...
・Third intake port, 8...Third intake valve, 9...Fuel injection valve, 11...Ignition plug, 12...Masking, 15...Exhaust port, 16...EGR port, 18... Valve lifter, 19... ECU
, 21... Cavity, 23... Rocker arm, 25... Cam, 26... Water temperature sensor.

Claims (1)

[Claims] 1. It has a first intake port that is always open to create a swirl in the intake air supplied into the combustion chamber, and an intake control valve that opens only in the engine's high-load, high-speed operating range, and supplies straight intake air into the combustion chamber. a second intake port provided with a fuel injection valve; and a third intake port provided with a fuel injection valve;
and a multiple intake valve engine, wherein the third intake valve is connected to a combustion chamber via a third intake valve, and the opening timing of the third intake valve is delayed from the opening timing of the first intake valve.