JPH0830418B2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an intake system for an engine, and in particular, the passage state of an intake passage between an expansion chamber and a combustion chamber provided in an intake system is changed according to the engine speed. An intake system for an engine configured to control.

(Prior Art) In recent years, in engines for automobiles and the like, it has been attempted to improve the engine output by utilizing the so-called intake inertia effect and the like to improve the intake charging efficiency. This intake inertia effect is that a negative pressure wave generated near the intake port at the start of the intake stroke is propagated in the intake passage toward the upstream side and is reflected at the open end of the passage, which causes a positive pressure wave. It is intended to increase the action of pushing the intake air into the cylinder by utilizing the intake pressure vibration in the intake passage caused by the phenomenon that the air is returned to the intake port.
This intake inertia effect is effective only when the natural frequency of the intake pressure vibration determined according to the length of the intake passage and the intake valve opening / closing cycle, that is, the engine speed are synchronized. Therefore, if the length of the intake passage is fixed to a fixed length, the effective intake inertia effect can be obtained only in a specific engine rotation region, and the charging efficiency can be improved over a wide operating region. Can not. Therefore,
As measures against such drawbacks, for example, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. -115819 discloses a configuration in which the length of the intake passage (equivalent pipe length) is variably controlled according to changes in the engine speed. Specifically, the state of the intake passage is changed so that the substantial length of the intake passage is shortened stepwise or steplessly as the engine speed increases. . With such a configuration, when the engine speed is in the low speed region, that is, when the intake valve opening / closing cycle (the number of opening / closing operations per unit time) is small, the pipe length of the intake passage becomes long and the intake passage inside the intake passage By decreasing the natural frequency of the intake pressure vibration, the opening / closing cycle of the intake valve and the intake pressure vibration are well synchronized, and when the engine speed is in the high speed region, contrary to the above case, Since the pipe length of the intake passage is shortened and the natural frequency of the intake pressure vibration in the passage is increased, the opening / closing cycle of the intake valve and the intake pressure vibration are well matched even in this high rotation range. As a result, in any case, the intake inertia effect can be effectively obtained, and the engine output can be improved over a wide operating range.

However, in the configuration in which the pipe length of the intake passage is variable according to the engine speed as described above, the pipe length of the intake passage is considerably long when the engine speed is in the low rotation region (especially extremely low rotation region). If this is not done, an effective intake inertia effect cannot be obtained, and therefore if such a configuration is adopted, there will be a problem that the intake device will become large. In particular, in an engine in which a surge tank is provided in the upstream portion of the intake system, when the above-mentioned configuration is applied to the intake passage between the surge tank and the combustion chamber, the installation space of the intake passage or the Layout problems arise.

(Object of the Invention) The present invention addresses the above-mentioned problems relating to the intake device of an engine configured to variably control the pipe length of the intake passage in accordance with the engine speed, and particularly when the engine speed is low. (EN) An intake device having a structure capable of reducing the natural frequency of intake pressure vibration in the intake passage without significantly increasing the pipe length of the intake passage when in the rotation region. This aims to reduce the size of the intake device and solve the problem of the installation space of the device while ensuring an effective intake inertia effect in a wide operating range from the low rotation range to the high rotation range. To do.

(Structure of the Invention) An intake device for an engine according to the present invention is characterized in that it has the following structure in order to achieve the above object.

That is, in an intake system for an engine, the intake system is provided with an expansion chamber such as a surge tank, and the passage state of an intake passage communicating between the expansion chamber and the combustion chamber is variably controlled according to the engine speed. A chamber having a predetermined volume smaller than that of the expansion chamber, the volume of which is smaller than that of the expansion chamber, in the middle of an intake passage that branches from the chamber and independently communicates with the combustion chamber of each cylinder, and a communication portion of the chamber to the intake passage. And an on-off valve control means for variably controlling the on-off valve according to the engine speed. The on-off valve control means operates to open the above-mentioned on-off valve when the engine speed is in the low speed range, close it when the engine speed is in the medium speed range, and open it again when the engine speed is in the high speed range. .

According to the above configuration, when the engine speed is in the middle rotation speed range, that is, when the opening / closing valve control means closes the opening / closing valve, the intake passage independently communicating with the combustion chamber of each cylinder from the expansion chamber (hereinafter , The independent intake passage) is disconnected from the chamber, the opening at the upstream end of the intake passage to the expansion chamber acts as an atmosphere opening portion. Therefore, in this case, intake pressure oscillation occurs over the entire length of the independent intake passage from the expansion chamber to the combustion chamber. In this case, in this intake device, the natural frequency when the intake pressure phenomenon occurs over the entire length of the independent intake passage and the length of the intake passage are adjusted so that the opening / closing cycle of the intake valve in the middle rotation region of the engine is synchronized. Is set, so that the inertial effect can be obtained by closing the opening / closing valve as described above in this middle rotation region.

Further, when the engine is in the high rotation speed region, that is, when the opening / closing valve is opened by the opening / closing valve control means to open the communication portion between the chamber and the independent intake passage, the chamber has a predetermined volume. Therefore, the communicating portion functions as an atmosphere opening portion. Therefore, the intake pressure vibration is generated in the short passage portion between the communication portion and the combustion chamber in the independent intake passage, and the natural vibration of the intake pressure vibration is increased. As a result, the intake pressure oscillation and the opening / closing cycle of the intake valve are synchronized even in the high rotation region.

On the other hand, when the engine speed is in the low speed region, the frequency of the pressure wave becomes low due to the low opening / closing cycle of the intake valve. Since the change is less likely to occur and the damping rate of the pressure fluctuation in the chamber is small, even if the opening / closing valve is opened and the chamber and the independent intake passage are communicated with each other, there is almost no reflection in this communication portion (the chamber has one cylinder). The volume around the expansion chamber is smaller than that of the expansion chamber so that low-frequency pressure waves can be transmitted), and reaches the expansion chamber at the upstream end of the independent intake passage to be reflected. Therefore, the pipe length of the independent intake passage in which the intake pressure vibration occurs becomes the entire length of the passage as in the middle rotation region, but in this case, since the chamber is connected to the independent intake passage, That is, the volume of the independent intake passage increases by the volume of, and as the volume increases, the natural frequency of the intake pressure oscillation becomes lower than that in the middle rotation region. As a result, the natural frequency of the intake pressure vibration and the opening / closing cycle of the intake valve are synchronized even in the low rotation region.

(Effect of the Invention) As described above, according to the engine intake device of the present invention, the length of the independent intake passage that branches from the expansion chamber and communicates with the combustion chamber is determined by the intake air when the engine speed is in the middle rotation range. The pressure oscillation and the opening / closing cycle of the intake valve are set to a length that can be synchronized with each other, and a chamber of a predetermined volume provided in the middle of the independent intake passage is made to act as an atmosphere opening portion in the high rotation region. In the low rotation speed region, the volume of the independent intake passage is increased so that the natural frequency of the intake pressure vibration is reduced.Therefore, the on-off valve provided in the communicating portion of the chamber with the independent intake passage is opened and closed. By doing so, the natural frequency of the intake pressure vibration is low,
It is variably controlled to an optimum value according to each of the middle and high rotation regions, and the intake pressure oscillation and the opening / closing cycle of the intake valve are well synchronized in each of the above regions, so that the intake charging efficiency is increased. . As a result, the intake inertia effect is effectively obtained over a wide operating range, and particularly, the length of the intake passage is sufficient to obtain the intake inertia effect in the middle rotation range. The installation space and layout problems will be solved.

(Example) Hereinafter, the Example of this invention is described based on drawing.

1 to 3 show the first embodiment of the present invention.
As shown in FIG. 2, the intake device 2 of the engine 1 includes a main intake pipe 3 whose upstream end is connected to an air cleaner (not shown),
A surge tank 4 connected to the downstream end of the main intake pipe 3,
Each cylinder 5 ... 5 branched from one side of the surge tank 4
Independent intake pipes 7 ... 7 connected to the intake ports 6 ...
With the internal passage of the independent intake pipe 7 and the intake port 6, an independent intake passage 9 of length L from the surge tank 4 to the combustion chamber 5a via the intake valve 8 is provided for each cylinder 5.
Is configured.

However, in the intake device 2, each of the independent intake pipes 7 ...
First and second chambers 10 and 11 are provided from the upstream side across 7. Of these, the first chamber 10 has an internal space of a predetermined volume in which the volume per cylinder is smaller than that of the surge tank 4 and is communicated with each of the independent intake passages 9 ... 9 through the communicating portions 12 ... In addition, each communication part 12 ... 12
First on-off valves 13 ... Similarly, in the second chamber 11, an internal space having a predetermined volume smaller than that of the surge tank 4 per cylinder is a communicating portion.
14 are connected to the respective independent intake passages 9 ... 9 and second communication valves 14 ... 14 are provided with second on-off valves 15 ... 15, respectively. In addition to the above configuration, the intake device 2 includes the first on-off valves 13 ... 13 and the second on-off valves.
First and second actuators 16 and 1 for driving opening and closing 15 ... 15 respectively
7 is provided, and receives the engine speed signal a from the engine speed sensor 18
Control units 19 for outputting the first and second drive signals b and c are provided at 6 and 17, respectively.

 Next, the operation of the first embodiment will be described.

The air taken in from an air cleaner (not shown) during operation of the engine 1 is introduced into the surge tank 4 through the main intake pipe 3, and further, the independent intake passages 9 are formed by the independent intake pipes 7 ... 7 and the intake ports 6 ... ... 9 and then is sucked into the combustion chambers 5a, 5a of the cylinders 5, 5 in a predetermined order. In that case, the first and second on-off valves 13 ... 13, 15 ... 15 that connect and cut off the respective independent intake passages 9 ... 9 and the internal spaces of the first and second chambers 10 and 11
Are controlled to be opened and closed by the control unit 19 as shown below.

That is, the engine speed N detected based on the speed signal a from the engine speed sensor 18 is shown in FIG.
When it is lower than the first set speed N ₁ shown in Fig. 3 and when the suspended engine speed N is in an extremely low rotation speed region, the control unit 19 causes the first and second actuators 16 and 17 to move through the first and second actuators 16 and 17. As shown in (I) and (II), drive signals b and c are output so that both the first and second on-off valves 13 and 15 are opened. From this state, when the engine speed increases and reaches the first set speed N ₁ , the control unit
19 outputs the drive signal b to close the first opening / closing valve 13 and, in the low rotation region until the engine speed N reaches the second set speed N ₂ , the first opening / closing valve 13
Is closed and the second opening / closing valve 15 is kept open. Further, when the engine speed N reaches the second set speed N ₂ in this state, the control unit 19
The drive signal c is output so as to close the second on-off valve 15, and the first and second on-off valves 13 and 13 are output in the middle rotation range until the engine speed N reaches the third set speed N ₃ . 15
Both are closed. Further, when the engine speed N reaches the third set speed N ₃ in this state, the control unit 19 outputs the drive signal c to open the second opening / closing valve 15 again, and the engine speed N In a high rotation speed region where N is equal to or higher than the third set rotation speed N ₃ , the first opening / closing valve 13 is closed and the second opening / closing valve 15 is opened. In this case, the open / closed states of both the on-off valves 13 and 15 are the same as those in the low rotation speed range.

By the way, when the engine speed N is in the high speed region, the second opening / closing valve 15 is opened as described above, so that the internal space of the second chamber 11 having a predetermined volume and the independent intake passage 9 communicate with each other. The communication portion 14 is communicated via 14 and serves as an atmosphere opening portion of the intake passage 9. Therefore, at the start of the intake stroke of the engine 1, that is, when the intake valve 8 is opened, the pressure wave generated in the intake port 6 and propagated toward the upstream side is
Since it is reflected at the formation position A (see FIG. 2) of the communication portion 14, the intake pressure vibration is therefore generated in the downstream portion of the independent intake passage 9, that is, in the short passage portion having the length l ₁ shown in FIG. It will occur as a vibration with a high natural frequency.
As a result, the intake pressure oscillation and the opening / closing cycle of the intake valve 8, that is, the engine speed N are synchronized with each other in a high rotation region, and an effective intake inertia effect is obtained by this synchronization, as shown in FIG. As shown by the solid line (a), the characteristic of the intake charging efficiency in which the peak X ₁ occurs in the high rotation region is obtained. Then, the output torque of the engine 1 in the high rotation region is increased by utilizing the characteristic at or near the peak X ₁ .

Further, when the engine speed N is in the medium speed range,
Since both the first and second on-off valves 13 and 15 are closed as described above, the pressure wave generated in the intake port 6 reaches the opening position B to the surge tank 4 at the upstream end of the independent intake passage 9. After reaching, it will be reflected. Therefore, in this case, the intake pressure vibration occurs over the entire length L of the independent intake passage 9, the natural frequency of the intake pressure vibration becomes lower than that in the above high rotation region, and the intake pressure vibration and intake air The opening / closing cycle of the valve 8 is synchronized with the engine speed N in the middle rotation range. As a result, as shown by the chain line (b) in Fig. 3 (III), the characteristic of the intake charging efficiency where the peak X ₂ is generated in the middle rotation region is obtained, and the characteristic of the peak X ₂ or its vicinity is utilized. As a result, the output torque is increased even in this middle rotation range.

However, when the engine speed N is in the low speed range, the first on-off valve 13 is closed and the second on-off valve is closed as described above.
Although the valve 15 is opened and the engine speed N is in the same state as in the high speed region, in this low speed region, the intake port 8 opens and closes due to the low cycle of the intake port. The vibration of the pressure wave propagating from 6 to the upstream side is a low-frequency vibration that is hardly affected by the change in the passage shape. Therefore, even though the internal space of the second chamber 11 communicates with the intake passage 9, the pressure wave is difficult to be reflected at the communicating portion 14 (position A), and is transferred to the surge tank 4 having a sufficiently large volume. Will reach the opening position B and be reflected. Therefore, the intake pressure vibration occurs over the entire length L of the independent intake passage 9 as in the case of the middle rotation region, but in this case, the internal space of the second chamber 11 communicates with the independent intake passage 9. As a result, the volume of the passage in which the intake pressure vibration is generated is increased by the volume of the space, so that the natural frequency of the intake pressure vibration is reduced. Therefore, the intake pressure oscillation and the opening / closing cycle of the intake valve 8 are synchronized with each other in the low rotation speed region of the engine speed N, and by this synchronization, the intake charging efficiency shown by the solid line (a) in FIG. A peak X ₃ will occur in the characteristic curve in the low rotation region. And
By utilizing the characteristic at or near this peak X ₃ , the output torque is increased even in the low rotation speed region.

When the engine speed N is in the extremely low speed range,
Both the first and second on-off valves 13 and 15 are opened so that the independent intake passage 9 and the internal space of the first and second chambers 10 and 11 are communicated with each other. Similar to the case, the intake pressure vibration occurs over the entire length L of the intake passage 9, and the volume of the passage is increased by the volume of the internal space of the first chamber 10 as compared with the case of the above low rotation region. The frequency is further reduced. As a result, the synchronization between the intake pressure oscillation and the opening / closing cycle of the intake valve 8 occurs at a lower rotation side than in the low rotation range, and therefore, in this extremely low rotation range as well, FIG. As shown by the broken line (C), the intake charging efficiency is increased and the engine output is increased.

As described above, in the above embodiment, the length L of the independent intake passage 9 is set to a length in which the intake pressure oscillation and the opening / closing cycle of the intake valve 8 are synchronized with each other when the engine speed N is in the medium speed range. By making the internal spaces of the chambers 10 and 11 communicate with the intake passage 9 according to the engine speed N, the intake inertia effect can be efficiently obtained in all regions of high, middle, low and extremely low speed. Therefore, the length of the intake passage can be shortened as compared with the case where the above effect is obtained only by the length of the intake passage in the low rotation speed or extremely low rotation speed region. As a result, the output torque can be improved over a wide operating range without increasing the size of the intake device 2.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the intake device 21 of the engine 20 in this embodiment, as shown in FIG. 4, a volume per cylinder is provided in the middle of the independent intake passage 22 branched from the surge tank 25 and communicating with the combustion chamber 20a of each cylinder. One chamber 23 having an internal space of a predetermined volume smaller than the surge tank 25 is an opening / closing valve.
It is communicated via 24 and the surge tank 25
A rotating member 26 that can rotate is provided inside. The intake passage 22 is connected to the rotating member 26 and the surge tank.
The rotating member 2 is connected to a spiral passage 27 defined by the peripheral wall of 25 and communicates with the inner space 26b through an opening 26a provided in the rotating member 26.
By the rotation of 6, the passage length from the combustion chamber 20a to the space 26b is variably controlled.

In this embodiment, as shown in FIG.
Like the second opening / closing valve 15 in the first embodiment, the opening / closing valve 24 has a low engine speed N in the low rotation speed region (second set speed N ₂
When it is in the following area), the valve is opened, and the middle rotation area (second
The valve is closed when it is in the set rotation speed N ₂ to the third set rotation speed N ₃ ) and is opened again when it is in the higher rotation area (the area of the third set rotation speed N ₃ or more). Controlled. Therefore, also in this embodiment, the engine speed N
Is in a high rotation region, a high natural frequency of intake pressure vibration occurs in a short passage portion from the opening position C of the intake port 28 to the combustion chamber 20a to the communication position D of the chamber 23 in the independent intake passage 22 to cause middle pressure rotation. When it is in the region, intake pressure vibration of medium natural frequency occurs in the long passage from the position C to the position E of the opening 26a of the rotating member 26, and when it is in the low rotation region, it is different from the case of the medium rotation region. Intake pressure oscillations of low natural frequency will occur over the same long passage and the inner space of the chamber 23. As a result, the intake charging efficiency is effectively increased in each region, and the characteristic shown by the chain line (d) in FIG. 5 (III) is obtained. Further, in this embodiment, in order to increase the filling efficiency and to smooth the change of the efficiency, the rotation member 26 is rotated in the low and middle rotation regions, as shown in FIG. 5 (II). Such variable control of the passage length is performed. That is, when the engine rotational speed N reaches a predetermined rotational speed N ₀ in the low rotational speed region, the rotating member 26 is started to rotate in the x direction in accordance with the increase in the rotational speed N, and the passage length is made stepless. And the engine speed N is the second set speed.
At the time when it reaches N ₂ and shifts to the middle rotation range, the on-off valve 24
Simultaneously with the closing operation of, the rotating member 26 is returned to the initial state to maximize the passage length. Then, as the engine speed N increases, the rotary member 26 is again rotated in the x direction to shorten the passage length, and in the high rotation speed region where the engine speed N is the third set speed N ₃ or more. , Keep the path length at its shortest. As a result, the natural frequency of the intake pressure vibration is gradually increased in accordance with the increase of the engine speed N even in each of the low speed region and the medium speed region, and as a result, the intake charge efficiency in both regions is further increased. While being effectively increased, local fluctuations of intake charging efficiency during the closing operation and the opening operation of the on-off valve 24 are smoothed,
The smooth characteristics shown by the solid line (e) in FIG. 5 can be obtained.

In this embodiment as well, since the length of the intake passage that provides the intake inertia effect in the medium speed region can also improve the filling efficiency in the low speed region, the size of the intake device can be reduced.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a schematic plan view of an engine intake device, and FIG. 2 is FIG. 1 II.
A cross-sectional view taken along line -II, FIG. 3 (I), (II), (II
I) is a characteristic diagram showing an open / closed state of the first on-off valve, a characteristic diagram showing an open / closed state of the second on-off valve, and a characteristic line diagram of intake charging efficiency showing action and effect, respectively. Further, FIGS. 4 and 5 show a second embodiment of the present invention, FIG. 4 is a schematic vertical sectional view of an intake device of an engine, and FIGS. 5 (I), (II) and (III) are respectively shown. FIG. 6 is a characteristic diagram showing an open / closed state of an on-off valve, a characteristic diagram showing control of a passage length of an intake passage, and a characteristic diagram of intake charging efficiency showing operation effects. 1,20 ... Engine, 2,21 ... Intake device, 4,26b ... Expansion chamber, 5a,
20a ... combustion chamber, 7,22 ... independent intake passage, 11,23 ... chamber,
15,24… Open / close valve, 19… Open / close valve control means (control unit).

Claims (1)

[Claims] 1. An intake device for an engine, comprising: an expansion chamber provided in an intake system; and a passage state of an intake passage between the expansion chamber and a combustion chamber being variably controlled according to an engine speed. In the middle of the intake passage that branches from the expansion chamber and independently communicates with the combustion chamber of each cylinder, a chamber of a predetermined volume whose volume per cylinder is smaller than that of the expansion chamber is communicated,
An on-off valve is provided in the communication portion of the chamber to the intake passage, and the on-off valve is closed when the engine speed is in the middle rotation range, and the on-off valve is opened when the engine speed is in the low rotation range and the high rotation range. An intake system for an engine, comprising an on-off valve control means for operating a valve.