JPH10196373A - Variable intake mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of filling with intake air in a wide range of the number of revolutions of an engine region, regarding a variable intake mechanism. SOLUTION: A surge tank 14 is communicated with the cylinders of an engine 12 through respective branch pipes 16 and a volume chamber 20 through connectors 22 and 24. An ACIS valve 18 to switch communication and disconnection of a tank chamber is arranged in a surge tank 14. On-off valves 28 and 30 are arranged at the pipe walls 22a and 24a of the connectors 22 and 24. An intake pipe 32 is communication with the volume chamber 20. With the switch valve 18 closed, a pressure wave generated at a cylinder is transmitted to the connectors 22 and 24. In this case, by opening and closing the on-off valves 28 and 30, the frequency of a pressure wave transmitted to the connectors 22 and 24 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable intake mechanism, and more particularly, to a variable intake mechanism suitable for realizing good charging efficiency in a wide range of engine speed.

[0002]

2. Description of the Related Art Conventionally, inertial supercharging has been known which improves the charging efficiency of intake air supplied to an engine by the inertia of an air column in an intake pipe of the engine. The inertial supercharging effect is
It becomes the maximum when the propagation time of the negative pressure wave generated in the intake stroke of the piston in the intake system and the closing timing of the intake valve are matched. The propagation time of the negative pressure wave changes according to the natural frequency of the intake system. Therefore, when the engine speed reaches a value corresponding to the natural frequency of the intake system, the inertia supercharging effect is maximized, and optimal charging efficiency is obtained. In this case, if the natural frequency of the intake system is changed according to the engine speed, the charging efficiency is improved in a wider engine speed range.

As a variable intake mechanism having such a function,
2. Description of the Related Art A configuration disclosed in, for example, JP-A-63-263217 is known. The above-mentioned conventional variable intake mechanism includes a rotatable flapper mechanism on a pipe wall at a connection portion of the intake pipe to the surge tank. In the above-described conventional variable intake mechanism, a state in which the flapper mechanism does not function as a pipe wall of the intake pipe and a state in which the intake pipe length is increased by the flapper mechanism functioning as the pipe wall are determined by the rotation position of the flapper mechanism. Is achieved. Therefore, according to the above-described conventional variable intake mechanism, the intake pipe length is changed by switching the position of the flapper mechanism, whereby the natural frequency of the intake system can be changed. By switching the flapper mechanism according to the engine speed, the engine speed range in which good charging efficiency can be obtained is expanded.

As a configuration that can achieve the same object, a variable intake mechanism in which the inside of a surge tank is divided into two chambers and an opening / closing valve for switching between communication and shutoff between the two chambers has been conventionally used. I have. In this variable intake mechanism, the state in which the two chambers of the surge tank are communicated and the state in which the two chambers are shut off are switched by opening and closing the on-off valve. In a state where the two chambers are communicated with each other, the pressure waves generated in the respective cylinders cancel each other out in the surge tank, so that the pressure waves do not propagate to the upstream side of the surge tank. In a state where the two chambers are shut off, the pressure waves are not canceled by the surge tank but propagated upstream from the surge tank. As described above, the natural frequency of the intake system is changed by changing the region where the pressure wave propagates.

[0005]

However, all of the above-mentioned conventional variable intake mechanisms change the natural frequency of the intake system in two stages. Therefore, the optimum charging efficiency is obtained only at two points in the engine speed range, and the charging efficiency cannot be improved in a wide engine speed range.

The present invention has been made in view of the above points, and has as its object to provide a variable intake mechanism capable of realizing good charging efficiency in a wide engine speed range.

[0007]

The above object is achieved by the present invention.
As described in, a surge tank that communicates with each cylinder of the engine, a plurality of chambers that are partitioned so that the inside of the surge tank communicates with at least one of the cylinders, and an upstream side of the surge tank An intake passage that communicates with each of the plurality of chambers, a switching unit that switches between a state in which the plurality of chambers are communicated with each other and a state in which the plurality of chambers are shut off in accordance with a rotation speed of the engine; A vibration characteristic changing means for changing the vibration characteristic of the intake passage in accordance with the rotation speed.

In the present invention, the switching means switches between a state in which the plurality of chambers of the surge tank are communicated with each other and a state in which the chambers are disconnected from each other in accordance with the engine speed. With the plurality of chambers connected to each other, pressure waves generated in each cylinder of the engine cancel each other out in the surge tank.
Therefore, the pressure wave is not propagated upstream of the surge tank. Therefore, in such a state, a pressure wave having a frequency f1 corresponding to the vibration characteristics downstream of the surge tank is generated. On the other hand, when the plurality of chambers are shut off from each other, the pressure waves do not cancel each other in the surge tank, and the pressure waves are transmitted to the intake passage upstream of the surge tank.
The frequency f2 of the pressure wave transmitted to the intake passage depends on the vibration characteristics of the intake passage. Accordingly, the vibration frequency f2 is changed by changing the vibration characteristics of the intake passage in accordance with the engine speed by the vibration characteristic changing means. by the way,
In general, when the rotational speed of the engine matches the frequency of the pressure wave generated in each cylinder of the engine, an optimum charging efficiency can be obtained by the inertia supercharging effect. Therefore, in the present invention, the frequencies f1 and f2 are set according to the number of revolutions of the engine.
Is realized and the frequency f2 is changed, thereby increasing the point at which the optimum charging efficiency is obtained in the engine speed region.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a variable intake mechanism 10 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view when the variable mechanism 10 is cut along a line II-II shown in FIG. FIG. 3 is a cross-sectional view of the step when the variable mechanism 10 is cut along the line III-III shown in FIG.

In the present embodiment, the variable intake mechanism 10
This is applied to the cylinder type engine 12. As shown in FIGS.
As described above, the variable intake mechanism 10 includes a surge tank 14.
I have. The surge tank 14 is shown in FIGS.
It is located at the top. The surge tank 14
First cylinder 13 of engine 12_-1~ 6th cylinder 13_-6Everywhere
The six branch pipes 16 communicate with each other. The first cylinder
13_-1~ 6th cylinder 13 _-6If no distinction is made,
It is represented as a cylinder 13. Branch pipe 16 is surge tank 1
4 to form a semi-circular curve toward the engine 12
Has been established. Each of the branch pipes 16 and each cylinder of the engine 12
At the connection part with 13 each intake valve (not shown)
Is provided.

An ACIS valve 18 is provided inside the surge tank 14. When the ACIS valve 18 is closed, the first tank chamber 14 a communicating the internal space of the surge tank 14 with the first cylinder 12 _-1 to the third cylinder 12 _-3 of the engine 12, and the fourth cylinder 12 _-4 to 6th cylinder 12
_-6 divided into a second tank chamber 14b which communicates, in a state of being open is configured to communicate with each other and the first tank chamber 14a and the second reservoir chamber 14b.

In the space between the surge tank 14 and the engine 12, a volume chamber 20 is provided.
It is provided so as to be surrounded by. The volume chamber 20 communicates with the first tank chamber 14a and the second tank chamber 14b of the surge tank 14 via connectors 22 and 24, respectively. The connectors 22 and 24 are tubular members having an elliptical cross-sectional shape, and are curved so as to surround the left side surface of the volume chamber 20 in FIG. The tube walls 22a, 24a of the connectors 22, 24 on the volume chamber 20 side are
It forms part of the middle left wall. On / off valves 28 and 30 that are opened and closed by a common actuator 26 are provided on the tube walls 22 a and 24 a of the connectors 22 and 24. Therefore, when the on-off valves 28 and 30 are opened, the internal spaces of the connectors 22 and 24 communicate with the internal space of the volume chamber 20 via the on-off valves 28 and 30. An intake pipe 32 communicates with the upstream side of the volume chamber 20. A throttle valve 34 is provided in the intake pipe 32.

The intake valves of each cylinder 13 of the internal combustion engine 12 are opened and closed at timings synchronized with the strokes of the corresponding pistons. When the intake valve is opened,
Air having a flow rate corresponding to the opening degree of the throttle valve 34 is sucked into the intake pipe 32, and is supplied to the cylinder 13 of the engine 12 through the volume chamber 20, the connectors 22 and 24, the surge tank 14, and the branch pipe 16. Is done. FIG. 4 shows a time chart of the opening period of each intake valve. As shown in FIG. 4, the intake valve of each cylinder 13 has a cylinder number 1 → 5 → 3
The valves are opened in the order of → 6 → 2 → 4. When the intake valve is opened, a negative pressure wave is generated near the intake valve in the branch pipe 16 with the start of the intake stroke of the piston. This negative pressure wave propagates through the branch pipe 16 and reaches the surge tank 14,
A part thereof is reflected by the surge tank 14. The phase of the reflected negative pressure wave is reversed, and the reflected negative pressure wave propagates toward the cylinder 13 as a positive pressure wave. When the timing at which the positive pressure wave reaches the intake valve coincides with the timing at which the intake valve is closed, the intake pressure in the branch pipe 16 increases, and the charging efficiency is improved. The length of the valve opening period of the intake valve (hereinafter, referred to as the valve opening period length) decreases as the engine speed of the engine 12 increases. Also, after the negative pressure wave is generated,
The time T1 from when the light is reflected by the surge tank 14 and reaches the intake valve coincides with the period of the natural frequency f1 determined by the structure of the branch pipe 16, such as the pipe length, pipe system, and shape. Therefore, the inertia supercharging effect is maximized at the engine speed NE1 in which the valve opening period length matches the time T1, and the optimum charging efficiency is obtained.

Further, a part of the negative pressure wave generated at the time of opening the intake valve is connected to the connector 2 upstream of the surge tank 14.
The air is propagated from 2, 24 through the volume chamber 20 to the intake pipe 32. This negative pressure wave is reflected at the end of the intake pipe 32, the phase is inverted, and the positive pressure wave is propagated toward the cylinder 13. The time it takes for this reflected wave to reach the intake valve is
Branch pipe 16, surge tank 14, volume chamber 20, connector 2
2, 24 and the period T2 of the natural frequency f2 determined by the structure of the entire intake system of the intake pipe 32, and T2>
The relationship T1 is established. Therefore, such natural frequency f
If the second pressure wave can be effectively generated in the intake system, the optimum charging efficiency can be obtained even at the engine speed NE2 (NE2 <NE1) where the valve opening period length matches the time T2. .

That is, as shown in a model diagram in FIG. 5, the variable intake mechanism 10 has a vibration mode of a frequency f1 at which the pressure wave is reflected by the surge tank 14 and a frequency f2 at the end of the intake pipe 32. By having a vibration mode, by realizing inertial supercharging in both of these vibration modes,
The charging efficiency can be improved in a wider engine speed region.

In this case, as can be seen from FIG. 4, for example, the opening periods of the intake valves of the first cylinder _13-1 and the fifth cylinder _13-5 overlap. Therefore, in a state where the first tank chamber 14a and the second tank chamber 14b of the surge tank 14 communicate with each other by opening the ACIS valve 18,
A positive pressure wave caused by the negative pressure wave is reflected due to the opening of the intake valves of the first cylinder 13 _-1, and negative pressure wave due to the opening of the intake valve of the fifth cylinder 13 _-5 cancel the surge tank 14 Thus, the negative pressure wave propagated upstream from the surge tank 14 is weakened. A second cylinder 13 _-2 sixth cylinder 1
Similarly, in the cylinders 3 _-6 , 13 _-3 and 13 _-4 , the opening periods of the intake valves overlap, so that the pressure waves cancel out in the surge tank 14 as described above. .

Therefore, in this embodiment, the engine 1
In the low rotation speed region 2, the ACIS valve 18 is closed to shut off the surge tank 14 between the tank chambers 14a and 14b. As described above, the tank chamber 14a
, A first cylinder 13 _-1 to a third cylinder 13 _-3 communicate with each other, and a fourth cylinder 13 _-4 to a sixth cylinder 13 _-6 communicate with the tank chamber 14b. In each of the combination of the first cylinder 13 _-1 to the third cylinder 13 _{-3 and} the combination of the fourth cylinder 13 _-4 to the sixth cylinder 13 _-6 , the opening periods of the intake valves do not overlap.
Therefore, the pressure wave is generated in the tank chamber 14a of the surge tank 14.
And 14b are transmitted to the intake pipe 28 without canceling each other. As a result, a pressure wave having the natural frequency f2 is generated in the intake system, and the optimum charging efficiency can be obtained even at the engine speed NE2.

The variable intake mechanism 10 of this embodiment is further characterized in that by opening and closing the on-off valves 28 and 30, the substantial length of the intake system upstream of the surge tank 14 can be changed. Have. That is, when the on-off valves 28 and 30 are closed, the air sucked from the intake pipe 32 flows through the connector 2 as shown by the solid line arrow 36 in FIG.
The pipe walls 22a, 24a of the pipes 8, 30 bypass the lower ends in FIG. On the other hand, when the on-off valves 28 and 30 are opened, the air sucked from the intake pipe 32 does not bypass the pipe walls 22a and 24a as shown by the arrow 38 shown by the broken line in FIG. , On-off valve 2
It flows into the connectors 22, 24 via 8, 30. As described above, in the present embodiment, the length of the intake system on the upstream side of the surge tank 14 is shortened by opening the on-off valves 28 and 30. As a result, the natural frequency f2 of the entire intake system increases, and the new natural frequency f3 (f3>
The vibration mode of f2) is realized.

That is, in the variable intake mechanism 10 of the present embodiment, the ACIS valve 18 is closed and the on-off valve 2 is closed.
By opening the valves 8 and 30, optimal charging efficiency can be obtained even at the engine speed NE3 (NE2 <NE3 <NE1) where the valve opening period length of the intake valve matches the cycle T3 of the natural frequency f3. become.

FIG. 6 shows the relationship between the engine speed NE in this embodiment, the open / closed state of the ACIS valve 18 and the on-off valves 28 and 30, and the vibration mode realized by this open / closed state. As shown in FIG. 6, in the low rotation speed region I including the rotation speed NE2, the ACIS valve 18 and the on-off valves 28 and 30 are both closed to realize the vibration mode of the natural frequency f2, and thereby the rotation speed is increased. The optimum filling efficiency is obtained at several NE2. In the middle rotation speed region II including the rotation speed NE3, the ACIS valve 18 is closed and the on-off valves 28 and 30 are opened to realize the vibration mode of the natural frequency f3. The optimum filling efficiency is obtained at the rotational speed NE3. Further, in the high rotation speed region III including the rotation speed NE1, the ACIS valve 18 is opened to realize the vibration mode of the natural frequency f1, thereby obtaining the optimum charging efficiency at the rotation speed NE1.

As described above, the variable intake mechanism 10 of this embodiment
According to the above, by switching the open / close state of the ACIS valve 18 that partitions the surge tank 14 and the open / close valves 28 and 30 provided upstream of the surge tank 14 in accordance with the rotational speed NE of the engine 12, the three engines are switched. Optimum charging efficiency can be obtained at the rotational speeds NE1, NE2, and NE3, whereby the charging efficiency can be improved over a wide range of engine rotational speeds.

In the first embodiment, the ACI
The S valve 18 is connected to the switching means described above by the connectors 22 and 2.
Reference numeral 4 corresponds to the above-described intake passage, and the on-off valves 28 and 30 correspond to the above-described vibration characteristic changing means. Next, a variable intake mechanism 40 according to a second embodiment of the present invention will be described with reference to FIGS. 7 and 8 are sectional views corresponding to FIG. 2 of the first embodiment. In FIGS. 7 and 8, the same components as those in FIG. I do. In FIG. 7, tube walls 42a, 44a of the connectors 42, 44 on the side of the volume 20 are shown.
Constitutes a part of the left side surface in the figure of the volume portion 20. The tube walls 42a, 44a are connected to the connectors 42, 44 and the volume 2
0 is provided as a part separate from the other parts so as to be rotatable about a point O shown in FIG.

When the pipe walls 42a, 44a are in the position shown in FIG. 7, the air sucked into the intake pipe 32 is, as shown by the arrow 46 in FIG. 7, the lower end portions of the pipe walls 42a, 44a in the figure. Bypasses and flows into the connectors 42 and 44. On the other hand, as shown in FIG. 8, when the pipe walls 42a, 44a are rotated clockwise from the posture shown in FIG.
Is drawn into the connectors 42 and 44 through the space between the tube walls 42a and 44a without bypassing the tube walls 42a and 44a. Therefore, in the state shown in FIG. 8, the substantial intake passage length of the connectors 42 and 44 is reduced as compared with the state shown in FIG. That is, in the present embodiment, the substantial intake passage length of the connectors 42, 44 can be continuously changed by the rotation angle of the tube walls 42a, 44a, whereby the natural frequency f2 of the entire intake system is reduced. It can be changed continuously.

Therefore, according to the variable intake mechanism 40 of the present embodiment, the pipe walls 42a, 44a depend on the engine speed NE.
By changing the rotation angle and realizing the natural frequency f2 according to the engine speed NE, it is possible to realize the optimum charging efficiency in a wide range of the speed range. In addition,
In this embodiment, the tube walls 42a and 44a correspond to the above-described vibration characteristic changing means.

Next, a variable intake mechanism 50 according to a third embodiment of the present invention will be described with reference to FIGS.
9 and 10 are cross-sectional views corresponding to FIGS. 2 and 3 of the first embodiment, respectively. In FIGS. 9 and 10, the same components as those in FIGS. 2 and 3 are denoted by the same reference numerals. The description is omitted.

As shown in FIGS. 9 and 10, partitions 56 and 58 are provided inside the connectors 52 and 54 of the variable intake mechanism 50 of this embodiment. FIG. 11 shows partition walls 56 and 58.
FIG. As shown in FIG.
Are flat plate portions 56a, 58a formed in a semicircular annular shape,
From both ends of the flat plate portions 56a, 58a, the flat plate portions 56a, 58
and a flange portion 56b, 58b and 56c, 58c extending perpendicularly to a. Partition walls 56, 58
The flat plate portions 56a, 58a extend along the longitudinal direction of the connectors 52, 54, and the flange portions 56b, 58b
Closes a part of the opening to the volume 20 of the connectors 52 and 54, and the flanges 56c and 58c
The connectors 52 and 54 are disposed inside the connectors 52 and 54 so as to partially close the openings to the surge tank 14.
Therefore, when the partition walls 56, 58 are displaced in the left-right direction in FIG. 10, the cross-sectional areas of the connectors 52, 54 are changed,
Thereby, the natural frequency f2 of the entire intake system is changed.

However, when the cross-sectional area of the connectors 52 and 54 is changed, the natural frequency f2 is changed as compared with the case where the lengths of the connectors 52 and 54 are changed as in the first and second embodiments. Cannot be changed significantly. However, when the cross-sectional areas of the connectors 52 and 54 are reduced, the amplitude of the pressure wave is increased, the flow velocity of the flowing air is increased, and the inertia supercharging effect is improved. Therefore, according to the present embodiment, the filling efficiency is reduced by reducing the cross-sectional area of the connectors 52 and 54 in the engine speed region where the inertial supercharging effect due to the matching between the engine speed and the natural frequency cannot be expected. Can be improved. In the present embodiment, the partitions 56 and 58 correspond to the above-described vibration characteristic changing means.

Next, a variable intake mechanism 60 according to a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 12 and FIG. 13 are the same as FIG.
FIGS. 12 and 13 are the same as those in FIGS. 1 and 2, and the description thereof is omitted. Also,
FIG. 14 shows a model diagram of the variable intake mechanism 60.

As shown in FIGS. 12 and 13, in the variable intake mechanism 60 of this embodiment, a second ACIS valve 62 is disposed inside the volume section 20. 2nd ACIS
The valve 62 divides the volume portion 20 into a first chamber 20a communicating with the connector 22 and a second chamber 20b communicating with the connector 24 when the valve is closed.
The first chamber 20a and the second chamber 20b are configured to communicate with each other. First chamber 20a and second chamber 20 of volume 20
The intake pipes 64 and 66 communicate with b.
The intake pipes 64 and 66 have throttle valves 68 respectively.
And 70 are provided.

According to the configuration of the variable intake mechanism 60,
In the state where the ACIS valve 18 is opened, as described in the first embodiment, since the negative pressure waves generated due to the opening of the intake valve cancel each other out in the surge tank 14, the vibration of the natural frequency f1 is generated. Only the mode is realized. When the ACIS valve 18 is closed and the second ACIS valve 62 is opened, the negative pressure wave
Thus, the vibration mode having the natural frequency f2 is realized.

Further, in the present embodiment, when both the ACIS valve 18 and the second ACIS valve 62 are closed, the negative pressure wave generated in the branch pipe 18 is generated by the surge tank 14.
The light propagates to the intake pipe 32 without being canceled by the volume 20 and is reflected at the end. Therefore, in such a state, as shown in FIG. 14, a vibration mode having a natural frequency f4 determined from the entire intake system from the branch pipe 16 to the end of the intake pipe 32 is realized.

The relationship of f1>f2> f4 holds among the three natural frequencies f1, f2 and f4. Therefore, in the present embodiment, the first type shown in FIG.
As in the case of the embodiment, the open / close state of the ACIS valve 18 and the second ACIS valve 62 is sequentially switched from the low rotational speed side of the engine 12 so that the respective modes of the natural frequencies f4, f2, and f1 are realized. Thereby, good charging efficiency can be realized in a wide range of engine speed. In this embodiment, the second ACI
The S valve 62 corresponds to the above-described vibration characteristic changing means.

[0033]

As described above, according to the present invention, good charging efficiency can be realized in a wide range of engine speed.

[Brief description of the drawings]

FIG. 1 is a plan view of a variable intake mechanism according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along a line II-II shown in FIG.

FIG. 3 is a step cross-sectional view taken along line III-III shown in FIG. 2;

FIG. 4 is a time chart of the opening period of each intake valve of the engine to which the variable intake mechanism of the embodiment is applied.

FIG. 5 is a model diagram of the variable intake mechanism of the present embodiment.

FIG. 6 is a diagram showing a relationship between an engine speed, an open / closed state of an ACIS valve and an on-off valve, and a realized vibration mode in the variable intake mechanism of the embodiment.

FIG. 7 is a sectional view of a variable intake mechanism according to a second embodiment of the present invention.

FIG. 8 is a view showing a state in which the pipe wall is rotated clockwise in FIG. 7;

FIG. 9 is a sectional view of a variable intake mechanism according to a third embodiment of the present invention.

FIG. 10 is a step cross-sectional view taken along the line XX shown in FIG.

FIG. 11 is a perspective view of a partition wall according to the present embodiment.

FIG. 12 is a plan view of a variable intake mechanism according to a fourth embodiment of the present invention.

FIG. 13 is a sectional view taken along a line XIII-XIII shown in FIG.

FIG. 14 is a model diagram of the variable intake mechanism of the present embodiment.

[Explanation of symbols]

 10, 40, 50, 60 Variable intake mechanism 12 Engine 18 ACIS valve 28 On-off valve 42 Connector 42a, 42b Pipe wall 56, 58 Partition wall 62 Second ACIS valve

Claims (1)

[Claims] A surge tank that communicates with each cylinder of the engine; a plurality of chambers each of which is partitioned such that an interior of the surge tank communicates with at least one of the cylinders; and an upstream side of the surge tank. An intake passage that is provided and communicates with each of the plurality of chambers; a switching unit that switches between a state in which the plurality of chambers are communicated with each other and a state in which the plurality of chambers are shut off according to a rotation speed of the engine; And a vibration characteristic changing means for changing a vibration characteristic of the intake passage according to a rotation speed.