JPH03189324A - Intake device of engine - Google Patents

Abstract

PURPOSE:To prevent torque shock in association with variation of an engine operation condition by changing over the opening/closing timing of an intake valve by means of a valve timing variable system under the condition that a shutter valve is closed. CONSTITUTION:At an intake passage 7 which communicates with an intake port 11 controlled by the opening/closing timing of an intake valve 15 by an actuator 40 of the intake valve 15, a shutter valve 24 which closes at the time of low-speed high load operation is provided. When the opening/closing timing of the intake valve 15 is changed over, in a control unit 30, a valve timing control signal is outputted to the actuator 40 of the intake valve 15 under the condition that the shutter valve 24 is closed. Since the opening/closing timing is changed over under the condition that intake air is not flowed to the intake passage 7 provided with the shutter valve 24, torque shock caused by changeover of the timing of the intake valve 15 is effectively prevented.

Description

[Detailed Description of the Invention] Rijutsu Kokuri Doctor! The present invention aims to improve fuel efficiency by reducing pumping loss in the low-speed operating range, and improves output in the high-speed operating range, as well as improving knocking resistance in the low-speed, high-load operating range. This relates to an engine intake system that can reduce pumping loss.More specifically, it aims to improve fuel efficiency by reducing pumping loss in low-speed operating ranges, and to improve output in high-speed operating ranges. In order to improve knocking resistance, an engine intake system is equipped with a variable valve timing mechanism that changes the opening and closing timing of the intake valve of at least one intake port depending on the engine operating condition. This invention relates to an engine intake system that can be improved.

The engine is equipped with a plurality of independent intake ports, and is equipped with a variable valve timing mechanism that changes the opening/closing timing of the intake valve of at least one intake port depending on the engine operating condition. By opening and closing the intake port at low speed timing and using the air-fuel mixture in the combustion chamber to be blown back into the intake passage that communicates with the intake port, pumping loss is reduced and fuel efficiency is improved. is known as an engine intake device that opens and closes an intake port at high speed timing to improve output.

In the intake system of such an engine, in a low-speed operating region, the intake valve of the intake port whose opening/closing timing is controlled by the variable valve timing mechanism is opened in the second half of the intake stroke after the intake valves of other intake ports are opened. A variable valve timing mechanism controls the opening and closing of the intake valve at low speed timing, so that it opens from the beginning to the first half of the compression stroke, thereby blowing the air-fuel mixture in the combustion chamber back into the intake passage, reducing pumping loss. On the other hand, in high-speed operating ranges, the opening/closing timing of the intake valve of the intake port whose opening/closing timing is controlled by the variable valve timing mechanism is adjusted to the opening/closing timing of the intake valves of other intake ports. By controlling the opening and closing of the intake valve at high speed timing so that the intake valves are almost the same,
Efforts are being made to improve output.

However, in the intake system of such an engine,
In a low-speed operation region, the intake valve of the intake port whose opening/closing timing is controlled by the variable valve timing mechanism is opened from the second half of the intake stroke to the first half of the compression stroke after the intake valves of other intake ports are opened. Since pumping loss is reduced by using the air-fuel mixture blowing back into the intake passage, it is inevitable that the turbulence in the combustion chamber will be attenuated and combustion will become unstable. There was a problem in that knocking was more likely to occur in the high-load operating range.

The present invention aims to improve fuel efficiency by reducing pumping loss in the low-speed driving range, improve output in the high-speed driving range, and reduce pumping loss in the low-speed high-load driving range. It is an object of the present invention to provide an engine intake device that can improve knocking resistance and prevent torque shock due to changes in engine operating conditions.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine equipped with a plurality of independent intake ports and a variable valve timing mechanism that changes the opening/closing timing of an intake valve of at least one intake port in accordance with engine operating conditions. In the intake system, a shutter valve is provided in the intake passage communicating with the intake port whose opening/closing timing of the intake valve is controlled by the variable valve timing mechanism, and a shutter valve that closes at low rotation and high load is provided, and when the operating state of the engine changes, Achieved by providing a control means for switching the opening/closing timing of the intake valve by the variable valve timing mechanism while the shutter valve is closed when the shutter valve is opened/closed and the opening/closing timing of the intake valve is switched. be done.

In a preferred embodiment of the present invention, the engine is a multi-cylinder engine, each cylinder of which has a plurality of independent intake ports, and the opening/closing timing of the intake valve of at least one intake port is controlled according to the engine operating state. In a cylinder system of a multi-cylinder engine that is equipped with a variable valve timing mechanism that changes the valve timing, the valve timing mechanism of each cylinder controls the opening and closing timing of the intake valve. The intake ports that are provided with a shutter valve that closes and communicate with the intake passage provided with the shutter valve are configured to communicate with each other via a communication passage on the downstream side of the shutter valve.

Effect of the Invention According to the present invention, a shutter valve is provided in the intake passage connected to the intake port where the opening/closing timing of the intake valve is controlled by the variable valve timing mechanism, and the shutter valve is closed at low rotation speeds and high loads. Since the opening and closing of the shutter valve is controlled, even if the intake valve whose opening/closing timing is controlled by the variable valve timing mechanism is open at low speeds and high loads, the air-fuel mixture will not flow into the intake passage upstream of the shutter valve. Not only is the compressed high-pressure air-fuel mixture prevented from being blown back up to the maximum level, but when the intake valve is closed, the compressed high-pressure air-fuel mixture is held between the intake valve and the shutter valve, and during the next intake stroke, the air-fuel mixture is When opened, this high-pressure air-fuel mixture flows into the combustion chamber and promotes turbulence of the air-fuel mixture in the combustion chamber, increasing the combustion rate and therefore greatly improving the anti-soaking property. Also, when the engine operating condition changes and the shutter valve is opened or closed and the intake valve opening/closing timing is changed, the intake valve is controlled by the variable valve timing mechanism with the shutter valve closed. Since a control means for switching the opening/closing timing of the valve is provided, the opening/closing timing of the intake valve is switched by the variable knob timing mechanism while the intake air does not flow through the intake passage where the shutter valve is provided. It becomes possible to effectively prevent torque shock caused by switching the opening/closing timing of the intake valve.

According to a preferred embodiment of the present invention, the intake passage communicates with an intake port whose opening/closing timing of the intake valve is controlled by the variable valve timing mechanism of each cylinder, and is provided with a shutter valve that closes at low rotation and high load. On the downstream side of the shutter valve, they are communicated with each other through a communication path, so even if there is a manufacturing error or the sealing performance of the ring
Check the sealing performance of the intake valve and exhaust valve for each cylinder.
Even if it is difficult to make it uniform and there are differences between cylinders, the high-pressure air-fuel mixture retained in the intake passage between the intake valve and shutter valve of a certain cylinder due to blowback during low-speed, high-load operation, The intake air is supplied through the communication passage between the intake valve and the shutter valve of the intake passage where the shutter valve of the cylinder that will next perform combustion is installed, so the intake air filling amount in each cylinder can be made uniform, and the cylinder It becomes possible to improve the difference.

Embodiment Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an overall schematic diagram of a four-cylinder engine including an engine intake system according to an embodiment of the present invention, and FIG.
FIG. 2 is a sectional view taken along line XX in FIG. 1, showing the upper structure of the combustion chamber. For convenience of explanation, FIG. 1D only shows a one-cylinder engine, and the others are omitted.

In FIGS. 1 and 2, an engine 1 includes a cylinder block 2 and a cylinder head 3, and is movable in the vertical direction within a cylinder bore 4 of the cylinder block 2 while sliding on the inner wall surface of the cylinder bore 4. A combustion chamber is formed in the cylinder bore 4 above the piston 5. On the other hand, an intake passage 6.7 and an exhaust passage 8.9 are formed in the cylinder head 3, with an intake port 10.11 and an exhaust port 12.13, respectively.
The cylinder bore 4 is opened at the cylinder bore 4 .

Also provided are an intake valve 14.15 and an exhaust valve 16.17 that open and close the intake port 6.7 and the exhaust port 8.9. In FIG. 1, only the intake passage 7, intake port 11, intake valve 15, exhaust passage 9, exhaust port 13, and exhaust valve 17 are illustrated.

In the intake passage 7, in order from the upstream side, an air cleaner 20,
An air flow meter 21 and a throttle valve 22 are provided, respectively, and a shutter valve 24 that is opened and closed by an actuator 23 is provided in the intake passage 7 on the downstream side of the throttle valve 22. Further, a fuel injection valve 25 for injecting fuel is provided in the intake passage 7 on the downstream side of the shutter valve 24. Similarly, the intake passage 6 is also provided with an air cleaner, an air flow meter, a throttle valve, and a fuel injection valve (not shown), but the intake passage 6 is not provided with a shutter valve.

In FIG. 1, 30 is a control unit, which includes an accelerator opening signal from an accelerator pedal position sensor 32 that detects the position of the accelerator pedal 31, a crank angle signal from a crank angle sensor 33 that detects the crank angle, and a shutter valve. A shutter valve opening signal from a shutter valve position sensor 34 that detects the opening of the shutter valve 24 and an intake air amount detection signal from the air flow meter 21 are respectively input to the control unit 30.

On the other hand, the control unit 30 outputs a knob timing control signal to an intake valve actuator 40 that opens and closes the intake valve 15, and a fuel injection amount control signal to the fuel injection valve 25.

FIG. 3 is a timing chart showing the opening/closing timing of the intake valves 14 and 15. The broken line A shows the valve lift curve of the intake valve 14, and the curve B shows the valve lift curve of the intake valve 15 at high speed timing. , curve C represents the valve lift curve of the intake valve 15 at low speed timing,
Each is shown. The opening and closing timings of these intake valves 14 and 15 are stored in the control unit 30 in the form of a map or the like.

As shown in FIG. 3, the intake valve 14 begins to open just before the piston 5 reaches the intake top dead center, and the piston 5
Its opening and closing timing is always set constant so that it closes immediately after reaching the intake bottom dead center. On the other hand, in a low rotational operating range where the engine rotational speed detected by the crank angle sensor 33 is below a predetermined value, the intake valve 15 opens slightly more than the point at which the intake valve 14 starts to open, as shown by curve B. The intake valve 1 starts to open at an early point in time.
The control unit 30 controls the intake valve actuator 40 so that the intake valve actuator 40 closes slightly later than the point at which the curve C closes.
The low speed timing indicated by
Intake valve 1 at the closing point of 4 and high timing
The control unit 30 controls the intake valve actuator 40 so that the intake valve actuator 40 closes later than when the intake valve actuator 5 closes, and after a while after the engine 1 enters the compression stroke.

FIG. 4 shows the intake valve 14.15 and the shutter valve 24.
This is an opening/closing control map.

As shown in FIG.
. In the following low rotation operating ranges α and β, the intake valve 14
is opened and closed at the timing shown by curve A in FIG. 3, and the intake valve actuator 40 is controlled by the control unit 30 so that the intake valve 15 is opened and closed at the low speed timing shown by curve C, On the other hand, a high-speed operation region γ where the engine speed N exceeds the predetermined value N0
In this case, the control unit 30 controls the intake valve so that the intake valve 14 is opened and closed at the timing shown by curve A in FIG. 3, and the intake valve 15 is opened and closed at the high speed timing shown by curve B. Although the actuator 40 is being controlled, the shutter valve 24 is activated when the engine speed N is below a predetermined value N0 and the engine load detected by the air flow meter 21 is a predetermined value.
The shutter valve actuator 23 is controlled by the control unit 30 so that the shutter valve actuator 23 is closed only in the low-speed, high-load operating range α exceeding the engine operating range β and γ, and is opened in the other engine operating ranges β and γ.

Therefore, in the high-speed operation region γ, the intake valve 15
However, since the intake valve 14 is opened and closed at high-speed timing that is almost the same as the opening and closing timing of the intake valve 14, and the shutter valve 24 is also open, sufficient intake air can be supplied into the fuel chamber and the desired engine output can be obtained. In addition, in the low rotation and low load operating region β, the intake valve 15 is opened and closed at low speed timing, and the shutter valve 24 is opened, so the air-fuel mixture blows back from the combustion chamber to the intake passage 7, and the pumping Loss can be reduced and fuel efficiency can be improved.

In this way, when the air-fuel mixture blows back from the combustion chamber to the intake passage 7, pumping loss is reduced, but the turbulence of the air-fuel mixture in the combustion chamber is weakened and combustion becomes unstable. Conventionally, there was a problem that knocking was more likely to occur in the low-speed, high-load operating region α, but in this embodiment, the shutter valve 24 is controlled to close in the low-speed, high-load operating region α. Therefore, at the beginning of the compression stroke, the high-pressure air-fuel mixture that is blown back from the combustion chamber into the intake passage 7 through the open intake valve 15 flows back further upstream by the shutter valve 24. As a result, the turbulent flow of the air-fuel mixture in the combustion chamber is weakened, preventing combustion from becoming unstable, and the high-pressure air-fuel mixture blown back from the combustion chamber into the intake passage 7 is 15 closes, the intake valve 1
5 and the shutter valve 24, and when the intake valve 15 is opened in the next intake stroke, it flows into the combustion chamber and the air-fuel mixture in the combustion chamber is Since the turbulence is promoted, it is possible to increase the combustion rate, and therefore, the knocking resistance in the low rotation and high load operating region α can be significantly improved.

Furthermore, in this embodiment, when the operating state of the engine changes and shifts from the low-speed, high-load operating region α to the high-speed operating region γ, the opening/closing timing of the intake valve 15 is switched to high-speed timing. Afterwards, the control unit 30 controls the intake valve actuator 40 and the shutter valve actuator 23 to gradually open the shutter valve 24, thereby preventing torque shock.

That is, from the low rotation high load operation region α where the opening/closing timing of the intake valve 15 is a low speed timing and the shutter valve 24 is closed, the opening/closing timing of the intake valve 15 is a high speed timing and the shutter valve 24 is open. When shifting to the high-speed operation region γ, the shutter valve 24 is opened at the same time as the opening/closing timing of the intake valve 15 is switched from low-speed timing to high-speed timing, or when the shutter valve 24 is opened first, Next, when controlling the opening/closing timing of the intake valve 15 from low-speed timing to high-speed timing, the intake air amount changes instantaneously and torque shock occurs, but in this embodiment, the shutter valve 24 is closed and there is no flow of intake air in the intake passage 7, first, the opening/closing timing of the intake valve 15 is switched to high-speed timing, and then the shutter valve 24 is controlled to be gradually opened. When the operating state of the engine shifts from the low-speed, high-load operating range α to the high-speed operating range γ, it is possible to obtain the high output required in the high-speed operating range γ while preventing torque shock. .

Conversely, when the operating state of the engine shifts from the high-speed operating range γ to the low-speed high-load operating range α, the shutter valve 24 is first closed, and then a state in which there is no flow of intake air in the intake passage 7 is established. By switching the opening/closing timing of the intake valve 15 to low speed timing, torque shock is prevented.

In addition, when the operating state of the engine changes and shifts from the low rotation and low load operation region β to the high rotation operation region γ, first, the shutter valve 24 is gradually closed, and the shutter valve 24 is fully closed, and the intake air is Switch the opening/closing timing of the valve 15 to high-speed timing, and then switch the shutter valve 2 to the high-speed timing.
The control unit 30 controls the intake valve actuator 40 and the shutter valve actuator 23 so as to gradually open the valve 4, thereby preventing torque shock.

That is, from the low rotation, low load operation region β where the opening/closing timing of the intake valve 15 is a low speed timing and the shutter valve 24 is open, the opening/closing timing of the intake valve 15 is a high timing and the shutter valve 24 is open. When transitioning to the high-speed operation region γ, which is opened, the shutter valve 2
When controlling the opening/closing timing of the intake valve 15 to switch from low-speed timing to high-speed timing with 4 open, the intake air amount changes instantaneously and torque shock occurs. teeth,
First, the shutter valve 24 is gradually closed, and with the shutter valve 24 fully closed and no intake air flowing in the intake passage 7, the opening/closing timing of the intake valve 15 is switched from low speed timing to high speed timing, and then gradually By opening the shutter valve 24, the operating state of the engine changes from the low-speed, low-load operating region β to the high-speed, low-load operating region γ.
This makes it possible to obtain the high output required in the high-speed operation region γ while preventing torque shock when shifting to the high-speed operation region γ.

Conversely, when the operating state of the engine shifts from the high-speed operating range γ to the low-speed low-load operating range β, the shutter valve 24 is first gradually closed, and the shutter valve 24 is fully closed and the intake passage 7 is closed. In a state where intake air does not flow through the shutter valve 2, the opening/closing timing of the intake valve 15 is switched from high speed timing to low speed timing, and then the shutter valve 2 is gradually closed.
4 is opened to prevent torque shock.

FIG. 5 shows an example of a flow chart of the switching control of the opening/closing timing of the intake valve 15 and the opening/closing control of the shutter valve 24.

In FIG. 5, first, the engine speed N detected by the crank angle sensor 33, the intake air amount Q detected by the air 70-meter 21, and the accelerator opening degree φ detected by the accelerator pedal position sensor 32 are ,
This is read by the control unit 30, and based on this, the control unit 30 determines that the engine rotation speed N is a predetermined value N. It is determined whether or not the engine speed is below, that is, whether the operating state of the engine is in the low-speed operating region α or β.

As a result, when the control unit 30 determines that the engine speed N is less than the predetermined value N0 and the engine operating state is in the low-speed operating region α or β, the control unit 3o further controls the accelerator opening. Rate of change Δ
Based on φ/Δt, it is determined whether the engine is in an acceleration state.

When the control unit 30 determines that the engine is not in an accelerating state, it moves to the next control cycle, and on the other hand, when it determines that the engine is in an accelerating state, it moves to the next control cycle based on the input signal from the shutter valve position sensor 34. Whether the shutter valve 24 is fully closed or not, that is,
It is determined whether the operating state of the engine is transitioning from the low-speed, high-load operating range α to the high-speed operating range γ.

As a result, when it is determined that the operating state of the engine is in the low rotation and high load operating region α, the control unit 3
0 outputs a valve timing switching signal to the intake valve actuator 40, switches the opening/closing timing of the intake valve 15 to high-speed timing, and then changes the rate of change in the accelerator opening according to the value of the change rate Δφ/Δt in advance in an experimental manner. The shutter valve actuator 23 is driven according to the map determined and stored, and the shutter valve 24 is driven.
control to open gradually. Therefore, when the operating state of the engine shifts from the low-speed high-load operating region α to the high-speed operating region γ, the shutter valve 24 remains fully closed and the opening/closing timing of the intake valve 15 changes from the low-speed timing to the high-speed timing. After that, the shutter valve 24 changes the accelerator opening change rate Δφ/Δt.
It is gradually opened until it is fully opened according to the value of , and after shifting to the control condition of the high rotational operating region γ, the next control cycle is started.

On the other hand, although the engine is accelerating, shutter valve 2
4 is not fully closed, that is, when the control unit 30 determines that the engine operating state is in the low-speed, low-load operating region β and is about to shift to the high-speed, low-load operating region γ, control unit 30
The shutter valve 24 is gradually closed in accordance with the rate of change Δφ/Δt of the accelerator opening based on a map that has been experimentally determined and stored in advance, and the shutter valve 24 is fully closed. After that, the opening/closing timing of the intake valve 15 is switched from low speed timing to high speed timing, and after that, the shutter valve 24 is gradually opened,
After the control conditions are shifted to the high-speed operation region γ and the shutter valve 24 is fully closed, the next control cycle is started.

On the other hand, based on the engine speed N input from the crank angle sensor 33, the engine speed N is a predetermined value N. When it is determined that the operating state of the engine is in the high-speed operating region γ, the control unit 30
Furthermore, it is determined whether the engine is in a deceleration state based on the rate of change Δφ/Δt of the accelerator opening.

As a result, when the control unit 30 determines that the engine is not in a deceleration state, it continues the control as it is; on the other hand, when it determines that the engine is in a deceleration state,
Gradually close the shutter valve 24,
is fully closed, the opening/closing timing of the intake valve 15 is switched from high-speed timing to low-speed timing, and further, based on the value of the intake air amount Q input from the air flow meter 21, the engine load is set to a predetermined value. , that is, whether the operating state of the engine is shifting to the low-speed, high-load operating region α or the low-speed, low-load operating region β. .

As a result, the engine load exceeds the predetermined value L0,
When it is determined that the engine operating state is shifting to the low rotation and high load operation region α, the control condition has already been shifted to the low rotation and high load operation region α, so the next control cycle is started.

On the other hand, when it is determined that the engine load is less than or equal to the predetermined value L0 and the engine operating state is shifting to the low rotation and low load operating region β, the control unit 3o further controls the The rate of change in accelerator opening Δφ/Δt is determined based on the stored map, etc.
The shutter valve 24 is gradually closed according to the value of , and after the shutter valve 24 is fully closed, the next control cycle is started.

As described in detail above, according to this embodiment, the engine output in the high-speed driving range is improved, the fuel efficiency is improved in the low-speed driving range, and the knocking resistance is improved in the low-speed high-load driving range. It becomes possible to provide an engine intake device that can significantly improve the engine speed and prevent torque shock.

FIG. 6 is a schematic plan view showing the upper structure of a combustion chamber of a two-cylinder engine according to another embodiment of the present invention.

In FIG. 6, the first cylinder 50 and the second cylinder 70 each have two intake ports 51, 52 and an intake port 71.
．． 72 is open, and each intake port 51.52.7
1 and 72 have intake passages 53, 54 and 7, respectively.
3.74 is connected. Although not shown, the intake port 5 is similar to the intake port 11 in the previous embodiment.
The intake valve 55 that opens and closes the intake port 2 and the intake valve 75 that opens and closes the intake port 72 are configured such that their opening and closing timings can be changed by the control unit 30. Also,
Two exhaust ports 56.57 and 76.77 are open to the first cylinder 50 and the second cylinder 70, respectively. Passages 58.59 and 78.79 are in communication.

Intake passage 54 communicating with intake port 52 of first cylinder 50
The intake passages 74 communicating with the intake ports 72 of the second cylinder 70 are respectively provided with shutter valves 60 and 80, and the intake passages 54 and 74 are arranged on the downstream side of the shutter valves 60 and 80. They are communicated through a communication path 90. The opening/closing timing of the intake valve 61.55 and the opening/closing timing of the intake valve 81.75 are as follows.
Each is controlled by a control unit (not shown).
Settings can be made in the same manner as shown in FIG. 3 in the embodiment described above, and opening and closing of the shutter valves 60 and 80 can also be set by a control unit (not shown) in the same manner as in FIG. 3 in the embodiment described above.

In the two-cylinder engine according to the embodiment of the present invention configured as described above, in the low-speed, high-load operating region, the intake valve 55 of the intake port 52 of the first cylinder 50 is closed during the compression stroke, similar to the embodiment described above. Even after entering the combustion chamber, it is still open, so the high-pressure air-fuel mixture in the combustion chamber flows from the combustion chamber to the intake port 5.
2, and is blown back into the intake passage 54. However, in this operating range, the shutter valve 60 is closed, so there is no backflow to the upstream side of the shutter valve 60, and when the shutter valve 60 is closed, The air-fuel mixture blown back from the combustion chamber to the intake passage 54 is held in a high pressure state between the intake valve 55 and the shutter valve 60. However, in this embodiment, the communication path 90 allows
Since the intake passages 54 and 74 on the downstream side of the shutter valve 60 and the shutter valve 80 are in communication with each other, the air-fuel mixture held between the intake valve 55 and the shutter valve 60 in a high pressure state flows through the communication passage 90. Then, it is supplied between the shutter valve 80 and the intake valve 75 of the intake passage 74. Therefore, when the intake valve 75 is subsequently opened when the second cylinder 70 is ignited, a high-pressure air-fuel mixture is introduced into the combustion chamber of the second cylinder 70 from the intake port 72.
Turbulence of the air-fuel mixture within the combustion chamber is promoted. after that,
When the intake valve 75 of the second cylinder 70 closes, the high-pressure air-fuel mixture held between the shutter valve 80 of the intake passage 74 and the intake valve 75 passes through the communication passage 90 to the first cylinder 60. The shutter valve 60 of the intake passage 54 and the intake valve 5
5.

In this way, when the intake valve 55 or intake valve 75 of one cylinder is closed, the high-pressure air-fuel mixture held between the intake valve 55 and the shutter valve 60 or between the intake valve 75 and the shutter valve 80 is Since it is supplied to the intake passage 74 of the other cylinder or the intake passage 54 through the passage 90, there may be manufacturing errors between the cylinders, or the sealing performance of the ring, the intake valve,
Even if the sealing properties of the exhaust valves differ between cylinders, it is possible to equalize the intake air filling amount supplied to each intake air.

According to this embodiment, it is possible to significantly improve knocking resistance in the low-speed, high-load driving range while improving engine output in the high-speed driving range and improving fuel efficiency in the low-speed driving range. Moreover, it is possible to provide an engine intake system that can prevent torque shock and can even out the intake air filling amount even if there is a difference between cylinders. .

The present invention is not limited to the above-mentioned examples, but various modifications can be made within the scope of the invention described in the claims, and these are also included within the scope of the present invention. Needless to say.

For example, in the embodiment shown in FIG. 6, a two-cylinder engine has been described, but it goes without saying that the present invention is also applicable to a multi-cylinder engine having three or more cylinders.

According to the present invention, pumping loss is reduced in the low-speed operation region to improve fuel efficiency, and in the high-speed operation region, output is improved and low-speed high-load operation is achieved. It becomes possible to obtain an engine intake system that can improve knocking resistance in the knocking region.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of a four-cylinder engine including an engine intake system according to an embodiment of the present invention, and FIG.
It is the XX line sectional view. FIG. 3 is a timing chart showing the opening/closing timing of the intake valve. FIG. 4 is an opening/closing control map of the intake valve and shutter valve. FIG. 5 is a flowchart showing an example of a method for controlling the switching of the opening/closing timing of the intake valve 15 and controlling the opening/closing of the shutter valve 24. FIG. 6 is a schematic plan view showing the upper structure of the combustion chamber of an engine according to another embodiment of the present invention. l...Engine, 2-cylinder block, 3-...
...Cylinder head, 4- cylinder bore, 5-
...-Piston, 6.7-Intake passage, 8.9...Exhaust passage, 1O
111-・Intake port, 12.13゛-・Exhaust port, 14.15-・・Intake valve, 16.17゛-・・
Exhaust valve, 20゛' air cleaner, 21...° air flow meter, 22--throttle valve, 23-...°shutter valve actuator, 24°
゛Shutter valve, 25--fuel injection valve, 30-control unit, 31--accelerator pedal, 32--accelerator pedal position 33-°゛crank angle sensor, 34-°-shutter Valve position 40... Intake valve actuator, 50... 1st cylinder, 51.52... Intake port, 53.54...° Intake passage, 55.61...° Intake valve, 56.57...・・Exhaust port, 58.59・°・・Exhaust passage, 60・・・Shutter valve, 70・−2nd cylinder, 71.72・・Intake port, 73.74°−・・Intake passage, 75. 81. Intake valve, 76.77-° exhaust port, 78.79° exhaust passage, 80...-shutter valve, 90... communication passage. Fig. 4 Fig. 6 ζ0 Diagram

Claims (1)

[Claims] In an engine intake system that includes a plurality of independent intake ports and is provided with a variable valve timing mechanism that changes the opening/closing timing of an intake valve of at least one intake port according to engine operating conditions, the variable valve timing mechanism A shutter valve that closes at low engine speeds and high loads is provided in the intake passage communicating with the intake port where the opening and closing timing of the valve is controlled. When the opening/closing timing of the
An intake system for an engine, comprising a control means for switching the opening/closing timing of the intake valve by the variable valve timing mechanism when the shutter valve is closed.