JPH07197816A - Intake air control device for engine - Google Patents

Abstract

PURPOSE:To provide an engine intake air control device capable of improving the condition of combustion by generating the tumble, and capable of securing the air of required amount. CONSTITUTION:In an engine, a long passage 25 and a short passage 26 are connected to an intake passage 18 which is continuously connected to openings 11a-11c of intake valves. A tumble generation variable means is provided with a tumble switching valve 23 which is turned between the non-tumbling position to fully open the intake passage 18 and the tumbling position to flow the intake flow in a deflecting manner to the ceiling wall of the intake passage. The intake passage length variable means is provided with a passage length switching valve 27 to open/close the short passage 26. An intake control means (ECU) 40 is constituted so that the tumble switching valve 23 may be turned to a tumbling position, and a passage length switching valve 27 may be turned to a closing position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine intake control system, and more particularly to an engine intake control system provided with tumble generation varying means for generating tumble in an intake flow introduced into a cylinder in accordance with an operating state of the engine. The present invention relates to the improvement of the intake control method capable of ensuring the required intake air amount even in the low speed rotation range.

[0002]

2. Description of the Related Art It is known that it is effective to generate vertical vortices, so-called tumble, in an intake air flow introduced into a cylinder in order to improve a combustion state of an engine, particularly in a low speed rotation range. As a means for generating this tumble, conventionally, for example, a method of introducing intake air into the cylinder by directing the intake air axially from the vicinity of the cylinder axis center by causing the intake air to flow toward the top wall side of the intake passage Has been proposed (for example, see Japanese Patent Application No. 3-111185).

[0003]

The tumble generating means described above is configured to generate the tumble by reducing the intake passage area by some means, especially in the low speed rotation range of the engine. Therefore, the inflow resistance of the intake air flow becomes high and the intake air amount tends to become insufficient, and as a result, there is a concern that the output may be lower than the design value although the combustion state can be improved.

The present invention has been made in view of the above circumstances, and provides an intake control device for an engine which can generate a tumble to improve a combustion state and can secure a necessary air amount. The purpose is to do.

[0005]

According to a first aspect of the present invention, there is a tumble state in which a vertical vortex (tumble) that flows in the cylinder axial direction into the cylinder is positively generated and a non-tumble state in which the vertical vortex is non-positively generated. Tumble generation varying means for switching the intake passage length, intake passage length varying means for varying the intake passage length, and intake control means for changing the intake passage length varying means to a long side when the tumble generation varying means is switched to the tumble state. An intake control device for an engine, characterized by comprising:

The invention of claim 2 is a specific example of each component in the invention of claim 1. First of all, this engine has a structure in which a long passage and a short passage are connected to an intake passage communicating with an intake valve opening. The tumble generation varying means includes a tumble switching valve that rotates between a non-tumble position where the intake passage is fully opened and a tumble position where the intake air flow is biased toward the top wall side of the intake passage. Furthermore, the intake passage length varying means includes a passage length switching valve that opens and closes the short passage. The intake control means is configured to rotate the tumble switching valve to the tumble position and rotate the passage length switching valve to the closed position in the low speed rotation range of the engine.

The invention of claim 3 is another specific example of each component in the invention of claim 1. First, this engine has the following configuration. While having three intake valve openings, the intake passage is defined by a partition wall into a first passage connected to the two intake valve openings and a second passage connected to the remaining one intake valve opening, and at least on the first passage side. One intake valve opening is formed to direct intake air in the cylinder axial direction. Further, a long passage and a short passage are connected to the confluence of the first and second passages.

The tumble generation varying means is provided with a tumble switching valve that opens and closes the second passage. Furthermore, the intake passage length varying means includes a passage length switching valve that opens and closes the short passage. The intake control means is configured to rotate the tumble switching valve and the passage length switching valve to the closed position in the low speed rotation range of the engine.

In the present invention, changing the intake passage length means changing the intake passage length suitable for obtaining the so-called inertia supercharging effect, that is, the intake passage length according to the engine speed. The length and the short length respectively mean the intake passage length with which the effect of inertial supercharging can be obtained in the low-medium speed rotation range and the high-speed rotation range of the engine.

Further, in the present invention, non-aggressive generation of tumble does not mean that tumble is not generated at all, but, for example, the intake flow is not controlled by rotating the tumble switching valve. It means that tumble is generated to the extent that it occurs depending on the shape of the intake port.

[0011]

According to the engine intake control device of the present invention, the intake control means, when the tumble generation varying means is controlled in the tumble state, for example, in the low speed rotation range of the engine, simultaneously increases the intake passage length varying means. Control the state.

For example, in the third aspect of the invention, the tumble switching valve rotates to the tumble position, the intake air flows unevenly toward the top wall side, is introduced axially in the cylinder from the intake valve opening, and is tumbled. Occurs. In the invention of claim 2,
The tumble switching valve closes the second passage, the intake air flows only on the first passage side, and at least a part of the intake air is axially directed into the cylinder from an intake valve opening having a shape suitable for generating tumble on the first passage side. Introduced with a tumble. In this case, in any of the inventions, the tumble switching valve is controlled to the tumble state, and at the same time, the intake passage length switching valve closes the short passage, so that the intake air is long enough to obtain the inertia supercharging effect in the low speed rotation range. Introduced through the passage.

Therefore, according to the present invention, when the tumble generating means is in the tumble generating state by narrowing down the intake passage area in the low speed rotation range of the engine, the intake passage length varying means closes the short passage, and the intake speed is low. It is introduced through a long passage in which the effect of inertia supercharging is obtained in the rotation range. As a result, tumble is generated and the combustion state is improved, and the required intake amount is obtained by inertia supercharging, and the required output is secured.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 10 are views for explaining an intake control device of a V-type engine according to an embodiment (first embodiment) of the invention of claims 1 and 2, and FIG. 1 is a schematic front view of the engine of this embodiment. 2, FIG. 2 is a sectional front view of the apparatus of this embodiment, FIG. 3 is a plan view of the engine of this embodiment, FIG. 4 is a sectional view taken along line IV-IV of FIG. 3, FIG. 5 is a bottom view of the intake system, and FIG. 6 is a surge. A plan view of the tank portion, FIG. 7 is a plan view of the tumble switching valve, and FIGS.
[Fig. 3] is a schematic diagram for explaining the operation of the apparatus of this embodiment.

In the figure, 1 is a water-cooled 4-cycle V-type 8
The engine 1 is a cylinder engine, and the engine 1 has an oil pan 3 that forms a lower portion of the crank chamber connected to a lower mating surface of a skirt portion 2a that forms an upper portion of the crank chamber of the cylinder block 2.
The left and right cylinder heads 4 and 5 are connected to the mating surfaces of the left and right cylinder portions 2b and 2c forming the V bank of the cylinder block 2 by head bolts, and the left and right cylinder heads 4 and 5 are connected.
It has a structure in which the left and right head covers 6 and 7 are attached to the upper mating surface of 5. The engine of this embodiment has left and right cylinder parts 2b and 2c, left and right cylinder heads 4 and 5,
Since the left and right head covers 6 and 7 and the valve operating mechanism arranged inside are left-right symmetric, the following description and illustration will be made only for either left or right.

Four cylinder bores (cylinders) 2d are formed in parallel in each of the cylinder portions 2b and 2c, and a piston 8 slidably inserted in each cylinder bore 2d is connected through a connecting rod 9. It is connected to the crankshaft 10.

On the block-side mating surfaces 4a, 5a of the left and right cylinder heads 4, 5, there are provided four combustion recesses 11 each forming a combustion chamber.
1, three intake valve openings 11a to 11c and two exhaust valve openings 11d and 11e are formed. The exhaust valve openings 11d and 11e are opened and closed by an exhaust valve 12, and the exhaust valves 12 are opened and closed by an exhaust cam shaft 13. The intake valve openings 11a, 11b, 11c are opened and closed by intake valves 14a, 14b, 14a, respectively.
The intake cam shaft 15 opens and closes a and 14b.

The exhaust valve openings 11d and 11e are led out to the outer wall of the bank of each cylinder head 4 and 5 by one exhaust port 16, and the exhaust manifold 17 is provided in the external connection opening 16a of each exhaust port 16. It is connected.

The intake valve openings 11a to 11c are led out to the inner wall of each bank of the cylinder heads 4 and 5 through the intake port 18. An intake unit 19 is connected to the external connection opening 18a of the intake port 18. The intake unit 19 includes the left and right cylinder portions 2b, 2c,
The shape is set so as to fill the V bank space A formed by the left and right cylinder heads 4 and 5 and the left and right head covers 6 and 7. The intake unit 19 includes the left and right valve bodies 20 connected to the external connection opening 18a.
a, 20b, and an intake manifold 21 arranged in an arch shape between the valve bodies 20a, 20b.
And a surge tank 22 suspended below the intake manifold 21.

The connection mating surfaces of the external connection openings 18a of the left and right cylinder heads 4 and 5 are formed so as to be flush with each other and parallel to the crankshaft.
b has a flat plate shape. This left and right valve body 2
1 extends in parallel with the crankshaft 10 in 0a and 20b.
A tumble switching valve 23 in which one valve plate 23b is fixed for each cylinder is arranged on the valve shaft 23a. The valve plate 23b is formed with a notch 23c located outside the V bank when the valve plate 23b is rotated to the fully closed position. Therefore, when the intake port 18 is closed by the valve plate 23b, the intake air flows unevenly toward the top wall 18b side of the intake port 18, is introduced while being directed in the axial direction from the cylinder center side, and tumble is likely to occur. There is.

Further, one fuel injection valve 24 is mounted on each of the valve bodies 20a and 20b so that the fuel injection valve 24 is substantially vertical, and the fuel injection valve 24 is mounted on each of the cylinders.
It is located between 3 and the intake camshaft 15. Further, each of the fuel injection valves 24 is located substantially on the center line of the intake port 18 when seen in a plan view, and its fuel injection port is directed to each of the intake valve openings 11a to 11c.

Here, in the present embodiment, in order to make the occurrence of the tumble more reliable, the following configuration is adopted.
The axis P of the spark plug 41 is inclined to the outside of the bank by an angle θ3 with respect to the cylinder axis H, and accordingly the intake valves 14a,
14b is erected on the cylinder axis H side as compared with the exhaust valve 12, and a space for further erection of the intake port inside the bank is secured. The intake valve 14a,
Due to the standing of 14b, the distance from the cylinder shaft H to the exhaust cam shaft 13 is L1, while the distance to the intake cam shaft 15 is L2, which is small. The intake port 18 is formed so as to stand up to the cylinder axis H side as much as possible, and the notch 23c of the tumble switching valve 23 is located on the top wall 18b side. As a result, the intake flow that is biased toward the top wall 18b by closing the tumble switching valve 23 is more strongly directed toward the cylinder axis H from the vicinity of the center of the cylinder, and the tumble is surely generated. Further, the fuel from the fuel injection valve 24 is injected so as to intersect with the unevenly flowing intake air flow to improve the mixing of air and fuel.

The intake manifold 21 has a merging passage 21a connected to the valve body 20a or 20b.
In the V-bank space A, extends diagonally inward and upward, and extends a long passage 21b downward from the upper end of the confluence passage 21a. Further, the long passage 21b extends inside the curved portion.
The short passage 21c having a larger cross-sectional area and a shorter length is branched and formed.

The lower end opening 21d of the long passage 21b
A long pipe 25 is provided at the lower end opening 21 of the short passage 21c.
Short tubes 26 are connected to e. The long pipe 25 and the short pipe 26 extend downward in the surge tank 22, and the lower end openings 25a and 26 of the both pipes 25 and 26 are extended.
a is expanded in a trumpet shape and is directed toward the side wall 22a of the surge tank 22 on the cylinder side. This allows
The short pipes 21c can be arranged in the crankshaft direction without any gap (see FIG. 4), and the openings 26a of the adjacent short pipes 26 can be arranged.
The short tube 26 can have a large diameter without interfering with each other.

With the above-mentioned structure, the passage length on the long side is approximately twice as long as the passage length on the short side, and the lower end openings 25a and 26a of both the pipes 25 and 26 and the side wall. A relatively large space B is formed between the space 22a and 22a. This improves the flow of air in the surge tank 22 in the crankshaft direction. The long pipe 25 and the short pipe 26 are preferably made of resin or pipes in order to reduce the weight.

Long passage 21 of the intake manifold 21
b lower end opening 21d and merging passage 21a lower end opening 21
The end face of f is flush with the short passage 21c
The end surface of the lower end opening 21e of the
It is located above the lower end surfaces of d and 21f. This is to avoid interference between the drive actuator of the passage length switching valve and the throttle valve, as will be described later.

Further, all the short passages 21c are positioned so as to overlap with each other on a straight line parallel to the crankshaft, and one valve shaft 27a is provided in the short passage 21c.
And an intake passage length switching valve 2 in which one valve plate 27b is fixed to the valve shaft 27a for each cylinder.
7 are provided. The valve shaft 27a is parallel to the valve shafts 23a of the left and right tumble switching valves 23 described above.

Here, the length measured along the passage axis from the opening 26a of the short passage 26 to each of the intake valve openings 11a to 11c is such that an inertia supercharging effect can be obtained in a high speed rotation range of 4600 rpm or more. Is set to.
Further, the length measured along the passage axis from the opening 25a of the long passage 25 to each of the intake valve openings 11a to 11c is such that an inertia supercharging effect can be obtained in a medium to low speed rotation range of less than 4600 rpm. It is set.

The surge tank 22 has a bowl-shaped cross-section that bulges downward and has a connection flange 22b with an opening at the upper end.
Is the lower end openings 21d and 21f of the intake manifold 21.
It is hermetically sealed by connecting to a mating surface formed flush with. An air inlet 22c is formed at one end of the surge tank 22 in the crankshaft direction, and a throttle body 30b has a pair of valve plates 30a rotatably arranged in the air inlet 22c. Valve 30
Are connected.

Here, the intake air is introduced into the surge tank through the air introduction port 22c, and is introduced into the engine through the long pipe 25 and the short pipe 26 through the intake manifold 21. In a multi-cylinder engine such as
When the above is provided, the intake air amount may vary. Therefore, in the present embodiment, as shown in FIG. 5, the long pipe 25 ′ located at a position distant from the air introduction port 22 c is opened toward the upstream side with respect to the air flow, and is located at a position close to the air introduction port 22 c. The long tube 25 ″ is opened toward the downstream side. This suppresses the imbalance of the air amount. In order to achieve the above object, the long tubes 25 ', 25 "are arranged obliquely, so that the height of these long tubes 25'(25" is not shown) is increased as shown in FIG. As a result, the front and rear corners 22 'of the surge tank 22 can be reduced in size, and the overall arrangement space can be reduced.

A diaphragm valve 28 as an actuator is arranged at the outward protruding end of the valve shaft 27a of the intake passage length switching valve 27, and the output shaft of the diaphragm valve 28 is connected to the valve shaft 27a. ing. The diaphragm valve 28 is supported by the boss portion 21g of the intake manifold 21, which is the same member as the intake passage length switching valve 27, and the diaphragm 29 is provided with the tumble switching valve 23. It is supported by the valve bodies 20a and 20b, which are the same members that are installed. Therefore, it is possible to avoid an assembly error between each switching valve and the diaphragm valve, and it is possible to smoothly perform the opening / closing operation.

Further, as described above, the intake passage length switching valve 27
Is arranged at a higher position than the tumble switching valve 23, thereby avoiding interference with the throttle body 30 arranged on the same side as the intake passage length switching valve 27.

Next, the function and effect of the apparatus of this embodiment will be described. In FIG. 8, reference numeral 40 denotes an ECU that controls the opening and closing of the tumble switching 23, the intake passage length switching valve 27, the throttle valve 30a, etc., which indicates the engine operating state such as the throttle valve opening a and the engine speed b. A signal is input and the tumble switching signal A and the passage length switching signal B are output according to the operating state of the engine.

First, as shown in FIG. 8, the tumble switching valve 23 is placed in the tumble state in the diaphragm valve 29 in the low speed low load operation region where the engine speed is, for example, 2600 rpm or less and the throttle opening is, for example, about 10%. The tumble switching signal A is supplied to the tumble switching valve 23, whereby the tumble switching valve 23 is rotated to the tumble position, that is, the closed position where only the top wall side of the intake passage 18 is open (the position shown in FIG. 2). As a result, the intake air flows unevenly toward the top wall of the intake passage 18, is introduced axially from the vicinity of the cylinder axis, and tumble is generated. In this case, as described above, the intake port 18 is vertically formed by the inclined arrangement of the spark plug 41 and the intake valves 14a, 14b so as to be closer to the cylinder axis H side, and the notch 23c is located on the top wall 18b side. Therefore, the occurrence of tumble is more reliable.

At this time, the diaphragm valve 28 is supplied with the switching signal B for making the passage length changeover valve 27 make the passage length longer, whereby the passage length changeover valve 27 is shortened as shown in FIG. The passage 21c is closed, and intake air is introduced into the cylinder from the long pipe 25 through the long passage 21b. As a result, the intake passage length is such that the inertia supercharging effect can be obtained in the low speed rotation range, and a sufficient intake amount can be secured while generating the tumble.

Further, as shown in FIG. 9, the tumble switching valve 23 is fully opened, that is, in the non-tumble position, when the engine speed is, for example, 2600 to 4600 rpm, and the throttle opening is, for example, about 40% in the medium speed and medium load range. On the other hand, the passage length switching valve 27 keeps the passage length long.
As a result, the throttle for generating tumble is released, and a larger intake amount is secured.

Further, as shown in FIG. 10, in the high speed and high load operation range where the engine speed is, for example, 4600 rpm or more and the throttle opening is substantially fully opened, the passage length switching valve 27 opens the short passage 21c, so Is introduced into the cylinder through a short passage having a length capable of obtaining an inertial supercharging effect in the high speed rotation region, and the rest is introduced into the cylinder through the long passage, and a large amount of intake air is secured in the high speed rotation region.

As described above, in this embodiment, when the tumble switching valve 23 is rotated to the tumble position in the low speed rotation range to generate the tumble, the passage length switching valve 27 is switched to the long side so that the inertia is increased. Since the supercharging effect is obtained, it is possible to compensate for the decrease in the intake air amount due to the inflow resistance that occurs due to the generation of tumble with inertial supercharging, and to generate a tumble to improve the combustion state while maintaining a sufficient intake air amount. It is possible to avoid the decrease in output.

Further, in this embodiment, each switching valve 23, 27,
Since the three valve shafts 23a, 27a, 23a of 23 are arranged in parallel with the crank shaft, a large number of passages can be opened and closed by one switching valve, and the structure can be simplified. In this case, the intake passage length switching valve 27 located at the center of the V bank is also used.
The valve shaft 27a of the throttle body 30 is disposed above the valve shafts 23a of the other two switching valves 23.
The interference with can be avoided.

11 to 13 are schematic views for explaining an intake control device according to an embodiment (second embodiment) of the invention of claims 1 and 3. In this embodiment, the intake valve opening 1
The intake port 18 for leading out 1a to 11c to the inner wall of the bank of each cylinder head 4, 5 is a first intake port 18a connected to the intake valve openings 11a, 11b by a partition wall 18d.
And the second intake port 18 connected to the intake valve opening 11c.
It is defined in b.

Here, of the intake valve openings 11a to 11c, the opening 11b located at the center is set in a so-called tumble port shape. That is, as shown in FIG. 2, the cylinder shaft H is added to the intake air sucked into the cylinder bore.
In order to generate the tumble by directing the direction, the angle θ1 formed by the axis V1 of the intake valve opening 11b (which coincides with the axis of the intake valve 14b) and the cylinder axis H is set to, for example, left,
The axis of the right intake valve opening 11a, 11c (the intake valve 14a,
The shape is set to be smaller than the angle θ2 between V2 and the cylinder axis H (which coincides with the axis of 14c), that is, the shape is oriented in the cylinder axis direction.

In the valve bodies 20a and 20b,
And a partition wall 20 continuous with the partition wall 18d of the intake port 18 in the merging passage 21a of the intake manifold 21.
c and 21h are formed. In addition, the valve body 2
1 extends in parallel with the crankshaft 10 in 0a and 20b.
A tumble switching valve 23 in which one valve plate 23b is fixed for each cylinder is arranged on the valve shaft 23a. The valve plate 23b is located on the second intake port 18b side,
When the second intake port 18b is closed by the valve plate 23b, intake air flows only through the first intake port 18a.

In the second embodiment, in the low speed rotation and low load operation range, as shown in FIG. 11, the second intake port 18b is fully closed by the tumble switching valve 23, and the intake is performed only on the side of the first intake port 18a. As described above, the tumble is generated by being introduced axially into the cylinder from the intake valve opening 11a and the tumble port 11b. In the medium-speed rotation medium-load operation range and the high-speed rotation high-load operation range, the tumble switching valve 23 is fully opened, and the intake air passes through both the first and second intake ports 18a and 18b, which is the same as the first embodiment. It is almost the same.

[0044]

As described above, according to the intake control device for an engine of the present invention, when the tumble generation varying means is in the tumble state, the intake passage length varying means is simultaneously in the long state. For example, in the invention of claim 2, when the tumble switching valve rotates to the tumble position, the intake passage length switching valve closes the short passage, and in the invention of claim 3, when the tumble switching valve closes the second passage, the intake passage length changes. The switching valve closes the short passage. Therefore, in the present invention, when the tumble generating means is in the tumble generating state by narrowing the intake passage area in the low speed rotation range of the engine or the like, the intake passage length varying means closes the short passage and the intake air is in the low speed rotation range. It is introduced through a long passage that provides the effect of inertia supercharging. As a result, tumble is generated and the combustion state is improved, and the required amount of intake air is obtained by inertial supercharging, and the required output is secured.

[Brief description of drawings]

FIG. 1 is an embodiment (first embodiment) of the invention of claims 1 and 2;
3 is a front view of an engine including an intake control device according to FIG.

FIG. 2 is a sectional front view of the engine of the first embodiment.

FIG. 3 is a plan view of the engine of the first embodiment.

FIG. 4 is a sectional side view of the engine of the first embodiment (of FIG. 3).
IV-IV line sectional view).

FIG. 5 is a bottom view of the intake manifold of the first embodiment engine.

FIG. 6 is a plan view of a surge tank portion of the engine of the first embodiment.

FIG. 7 is a front view of the tumble switching valve of the first embodiment.

FIG. 8 is a schematic diagram for explaining the operation of the engine of the first embodiment.

FIG. 9 is a schematic diagram for explaining the operation of the engine of the first embodiment.

FIG. 10 is a schematic diagram for explaining the operation of the engine of the first embodiment.

FIG. 11 is a schematic diagram for explaining the operation of the engine provided with an embodiment (second embodiment) of the invention of claims 1 and 3;

FIG. 12 is a schematic diagram for explaining the operation of the engine of the second embodiment.

FIG. 13 is a schematic diagram for explaining the operation of the engine of the second embodiment.

[Explanation of symbols]

 1 engine 2d cylinder bore (cylinder) 11a-11c intake valve opening 18 intake passage 18a first intake port (first passage) 18b second intake port (second passage) 18d, 20c, 21h partition wall 21b, 25 long passage, long Tube 21c, 26 Short passage, Short tube 23 Tumble switching valve 27 Intake passage length switching valve 40 ECU (intake control means) H cylinder shaft

Claims (3)

[Claims] 1. A tumble generation varying means for switching between a tumble state in which a vertical vortex (hereinafter referred to as “tumble”) flowing in a cylinder axial direction into a cylinder is positively generated and a non-tumble state in which a vertical vortex is not positively generated is switched, and intake air. An engine comprising: an intake passage length varying means for varying a passage length; and an intake control means for varying the intake passage length varying means to a longer side when the tumble generation varying means is switched to a tumble state. Intake control device. 2. The engine according to claim 1, wherein the engine has a structure in which a long passage and a short passage are connected to an intake passage communicating with an intake valve opening, and the tumble generation varying means fully opens the intake passage. And a tumble switching valve that rotates between a non-tumble position where the tumble is not positively generated and a tumble position where the tumble is positively generated by biasing the intake flow toward the top wall of the intake passage. The intake passage length varying means includes a passage length switching valve that opens and closes the short passage, and the intake control means rotates the tumble switching valve to a tumble position in the low speed rotation range of the engine. An intake control device for an engine, which is configured to rotate the passage length switching valve to a closed position. 3. The engine according to claim 1, wherein the engine is 3
One intake valve opening is defined, and the intake passage is divided into a first passage connected to the two intake valve openings by a partition wall and a second passage connected to the remaining one intake valve opening, and at least one of the first passage side is provided. One intake valve opening is formed so as to direct the intake air flow in the cylinder axial direction, and further, a long passage and a short passage are connected to the confluent portion of the first and second passages. , The tumble generation varying means,
A tumble switching valve that opens and closes the second passage,
The intake passage length varying means includes a passage length switching valve that opens and closes the short passage, and the intake control means turns the tumble switching valve and the passage length switching valve to a closed position in the low speed rotation range of the engine. An intake control device for an engine, which is configured to operate.