JPH0577846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a multi-cylinder engine, particularly an engine that utilizes the dynamic effect of intake air to increase intake air filling efficiency.

(Prior art) In recent years, in automobile engines, attempts have been made to improve intake air filling efficiency or output by utilizing dynamic effects such as air inertia effect and resonance effect. When using the resonance effect in a multi-cylinder engine, each cylinder is divided into two cylinder groups with non-adjacent intake orders, and the cylinders in both cylinder groups are connected to each other through independent intake passages. Two intake collecting sections are provided which are connected together. These intake collecting parts act as resonance boxes or resonance tubes that resonate with intake vibrations of a specific frequency, and the large positive pressure waves generated by the resonance effect push intake air into the corresponding cylinders. .

However, with the above configuration, the resonance effect can only be obtained in a specific engine rotation range where the frequency of intake vibration matches the natural frequency of the intake gathering part determined by the volume and pipe length. Become.
Therefore, as shown in Japanese Utility Model Application Publication No. 59-148425, for example, two intake collecting parts are merged on the upstream side, while a communication part is provided in the middle of both intake collecting parts to communicate the two collecting parts. , and an on-off valve that opens and closes the communication portion, so that the natural frequency of both air gathering portions can be switched between two high and low levels by opening and closing the valve. In other words, when both intake air gathering parts meet only at the upstream end, the pipe length becomes longer and the natural frequency becomes lower, so a resonance effect can be obtained in the low rotational speed range of the engine. If the collecting parts are connected in the middle, the pipe length will be shortened and the natural frequency will be high, resulting in a resonance effect in the high engine speed range. Therefore, if the opening/closing valve is controlled to open and close according to the rotational range of the engine, the intake air filling efficiency or the output can be improved in a plurality of engine rotational ranges.

On the other hand, some exhaust gas is recirculated into the engine intake system from the exhaust system to reduce NOx (nitrogen oxides), which is a harmful component in exhaust gas, or a throttle valve is used to control rotation during idle. Bypass air is supplied to bypass the tutle valve, but these exhaust gases and air need to be evenly supplied to each cylinder. Therefore, when the intake system is provided with two intake collecting sections corresponding to two cylinder groups as described above, device passages such as exhaust recirculation passages and bypass air passages are connected to exhaust recirculation control valves and bypass air control valves. It branches on the downstream side of the valve, etc., and the branched parts are connected to both of the above-mentioned intake collecting parts, respectively. In this case, the two intake collecting parts communicate with each other via the branched part of the device passage. .
Therefore, when trying to obtain a resonance effect in a predetermined engine speed range by blocking the communication between the two intake air collection parts with an on-off valve, especially under high load, the intake vibrations within the two intake air collection parts are caused by the above-mentioned device. They cancel each other out through the branching portions of the passages, and as a result, the resonance effect at each intake gathering portion is halved, making it impossible to obtain the desired intake air filling amount in the relevant engine rotation range.

To solve this problem, the pipe diameter of the branch part of the device passage can be made thinner and sufficiently long to reduce the mutual influence of vibrations in both intake air collecting parts through the branch part, or the control valve can be Two systems of device passages may be provided corresponding to the two air intake collecting portions. However, in the former case, it is necessary to ensure the flow rate of exhaust gas or bypass air, so the pipe diameter cannot be made too small, and if the pipe length at the branch part is made long, the control valve on the device passage becomes distant from the intake system. As a result, control responsiveness deteriorates. In addition, in the latter case, the device equipment becomes complicated and costs increase, and since the operating amounts of the control valves in both systems do not match, there is a risk that the amount of exhaust gas etc. supplied to each cylinder may become uneven. .

(Object of the Invention) The present invention provides an engine that improves intake air filling efficiency by utilizing a resonance effect in an intake system.
In particular, two intake collecting parts are provided in the intake system corresponding to two cylinder groups whose intake orders are not adjacent to each other,
In addition, in a multi-cylinder engine in which a communication portion provided between both intake air gathering portions is provided with an on-off valve that opens and closes depending on the rotation range of the engine, the on-off valve is closed to shut off the communication portion between both intake air gathering portions. At times, both collecting portions are prevented from communicating with each other via a branch path of the device passage. As a result, especially under high load, both intake collecting sections reliably resonate with intake vibrations of a predetermined frequency in a predetermined engine rotation range in which the on-off valve is closed, thereby improving the intake air filling efficiency or the engine speed. The purpose is to ensure that the output is effectively improved.

(Structure of the Invention) The intake system for a multi-cylinder engine according to the present invention is characterized in that it is structured as follows in order to achieve the above object.

That is, two intake collecting parts are connected to two cylinder groups whose intake order is not consecutive through independent intake passages, a communication passage connects both intake collecting parts, and the communication passage is connected in a predetermined engine rotation range. In an intake system for a multi-cylinder engine having a closed on-off valve, a device passage having a control valve is branched on the downstream side of the control valve, and the branch passage is connected to both the intake air gathering parts or a resonance pipe provided on the upstream side thereof. A cutoff valve is provided which connects the two branch passages to each other and blocks communication between the two branch passages when the on-off valve is closed.

The device passage is, for example, an exhaust gas recirculation passage or a bypass air passage for idle rotation control, and these passages are provided with an exhaust gas recirculation control valve or a bypass air control valve that is closed at least when the engine is under high load. ing. Therefore, under high load, the control valve on the device passage and the cutoff valve provided between the branch passages in the device passage close together in the predetermined engine rotation range in which the on-off valve is closed. Communication of the intake air collecting section is completely blocked. As a result, the intake air gathering portion reliably resonates with the intake vibration in the engine rotation range in the high load range.

When performing exhaust gas recirculation or supplying bypass air, the control valve on the device passage and the cutoff valve between the branch passages are opened, so that the exhaust gas, etc. is distributed equally to each cylinder via both intake collecting parts. However, since the area where exhaust gas recirculation or bypass air is supplied is in the low to medium load area of the engine where sufficient intake air filling efficiency is not required, it is necessary to open the above shutoff valve. Even if both intake collecting parts communicate through a device passage (branch passage),
This does not affect the effect of improving the intake air filling efficiency due to the resonance effect.

(Effects of the Invention) As described above, according to the present invention, two intake collecting parts are provided in the intake system corresponding to two cylinder groups whose intake orders are not adjacent to each other, and an on-off valve is provided between the two intake collecting parts. By blocking or communicating,
In an intake system for a multi-cylinder engine, which is configured to obtain a resonance effect in a plurality of engine rotation ranges, and in which branch portions of a device passage are respectively connected to both of the intake collecting portions or resonance pipes provided upstream thereof, When the on-off valve is closed, communication between the two intake air collecting parts is prevented through the device passage, and the communication between the two intake air collecting parts is completely cut off. As a result, in a predetermined engine speed range in which the on-off valve is closed, especially in a high load range, a reduction in the resonance effect due to the communication between both intake air collecting parts through the device passage is prevented, and the required charging efficiency is achieved in that speed range. An improvement effect or an output improvement effect can be obtained.

(Example) Examples of the present invention will be described below.

As shown in FIG. 1, the engine 1 has six cylinders 2 ₁ to 2 ₆ , and these cylinders 2 ₁ to 2 ₆ are divided into two cylinder groups 3 ₁ in which cylinders that are not adjacent in the intake order are grouped into the same group. , 3 are grouped into ₂ . That is, the intake order is, for example, first cylinder 2 ₁ → fourth cylinder
The order is cylinder ₂₄ → second cylinder ₂₂ → fifth cylinder ₂₅ → third cylinder ₂₃ → sixth cylinder ₂₆ , in other words, the cylinders of the two cylinder groups ₃₁ and ₃₂ overlap. The intake strokes are performed alternately without any problems.

On the other hand, the intake device 4 that supplies intake air to each of the cylinders 2 ₁ to 2 ₆ has intake ports 5 1 _{to 5} of each of the cylinders 2 ₁ to _{2 6} .
Independent intake passages 6 ₁ whose downstream ends are respectively connected to 5 _6
6 , and the upstream ends of the intake passages ₆₁ to ₆₃ corresponding to the first cylinder group ₃₁ among these independent intake passages are connected to the first surge tank ₇₁ and the second cylinder group _32. A second surge tank 7 ₂ to which the upstream ends of the corresponding intake passages 6 ₄ to 6 ₆ are connected, and first and second surge tanks provided upstream of both surge tanks 7 ₁ and 7 ₂ and whose upstream ends are joined together. It is composed of resonance passages 8 ₁ and 8 ₂ and a merging passage 9 led from an air cleaner (not shown) and connected to a merging part (branching part) of the first and second resonance passages 8 ₁ and 8 ₂ , The first and second resonance passages 8 ₁ ,
First and second throttle valves 10 ₁ and 10 ₂ are provided which open and close in conjunction with the throttle valve 8 ₂ . Here, the first surge tank 7 ₁ and the first resonance passage 8 ₁ and the second surge tank 7 ₂ and the second resonance passage 8 ₂ constitute mutually independent first and second resonance spaces, These resonance spaces have a constant natural frequency f determined by the volume V of the surge tank and the length L of the resonance passage.

Further, a relatively short communication path 11 is provided between the first and second surge tanks 7 ₁ and 7 ₂ to communicate the surge tanks 7 ₁ and 7 ₂ , and a relatively short communication path 11 is provided between the first and second surge tanks 7 1 and 7 2 . An on-off valve 12 that opens and closes is provided. Then, open the on-off valve 12 to open the communication path 1.
1, the left and right halves 1 of the communication path 11
1 ₁ and 11 ₂ form first and second resonance spaces together with the first and second surge tanks 7 ₁ and 7 ₂ instead of the first and second resonance passages 8 ₁ and 8 ₂ . There is. In this case, the communication path 1 that acts as a resonance tube
Since the length L' of each half part 11 ₁ , 11 ₂ of 1 is shorter than the length L of the first and second resonance passages 8 ₁ , 8 ₂ , the natural frequency f' of the resonance space in this case is as follows. It will be higher than in the case of

Further, the first and second surge tanks 7 ₁ and 7 ₂ have an exhaust recirculation passage 14 equipped with an exhaust recirculation control valve 13 as a device passage, and a bypass air passage 16 equipped with a bypass control valve 15 for use during idling.
are connected. These passages 14, 16
are both passages 1 on the downstream side of the control valves 13 and 15.
4, 16 common first and second branch passages 17 ₁ , 1
7 ₂ , and both branch passages 17 ₁ and 17 ₂ are the first,
They are connected to second surge tanks 7 ₁ and 7 ₂ , respectively. In other words, the exhaust gas recirculation passage 14 and the bypass air passage 16 are both connected to the first and second branch passages 17 ₁ ,
17 ₂ via the first and second surge tanks 7 ₁ , 7 ₂
is communicated with. At the confluence of the first and second branch passages 17 ₁ and 17 ₂ , both branch passages 17 ₁ and 17 2 are connected.
17. A shutoff valve 18 is provided for communicating or shutting off between _the two, and the shutoff valve 18 and the on-off valve 12 on the communication path 11 are configured to be closed and opened at the same time by a common actuator 19. has been done. It should be noted that an opening/closing control signal corresponding to the operating range of the engine is sent to the actuator 19 from a control device (not shown).

Next, the operation of the above embodiment will be explained.

During operation of the engine 1, intake air taken in from an air cleaner (not shown) is distributed and introduced from the confluence passage 4 on the upstream side of the intake device 4 into the first and second resonance passages 8 ₁ and 8 ₂ , respectively. It flows into the first and second surge tanks 7 ₁ and 7 ₂ via two throttle valves 10 ₁ and 10 ₂ . And this intake is the first
The first to third cylinders ₂₁ forming the first cylinder group ₃₁ are connected from the surge tank ₇₁ to the independent intake passages ₆₁ to 63 _.
to 2 ₃ , and is distributed and supplied from the second surge tank 7 ₂ to the fourth to sixth cylinders 2 ₄ to 2 ₆ forming the second cylinder group 3 ₂ through independent intake passages 6 ₄ to 6 ₆ . In that case, three cylinders 2 ₁ forming the first cylinder group 3 _1
-23 are not adjacent in the cylinder order, and the three cylinders ₂₄ to ₂₆ constituting the second cylinder group ₃₂ are also not adjacent in the intake order, so in each of the cylinder groups ₃₁ and _32, , the pressure waves generated when the intake ports 5 ₁ to 5 ₃ or 5 ₄ to 5 ₅ are opened and closed cause the pressure waves to flow through the independent intake passages 6 ₁ to 5 5 .
When propagated to the corresponding surge tank 7 ₁ or 7 ₂ through 6 ₃ or 6 ₄ to _{6 6} , they do not cancel each other out, and as a result, the first and second surge tanks 7 ₁ ,
The same number of intake vibrations occur within _{7.2 seconds} depending on the engine speed. And both surge tanks 7 ₁ , 7 ₂
The communication passage 11 between them is shut off by an on-off valve 12, and the low natural frequency f which is independent of each other is provided by both the surge tanks 7 ₁ and 7 ₂ and the first and second resonance passages 8 ₁ and 8 ₂ . When two resonance spaces are formed,
In the low rotation range of the engine 1, the resonance space resonates with the intake vibration, and the large positive pressure wave generated by this resonance increases the intake air filling efficiency. Further, the on-off valve 12 is open, and the first and second surge tanks 7 ₁ , 7 ₂ and the left and right halves 11 ₁ of the communication passage 11 ,
When two resonant spaces with a high natural frequency f' are formed by 11 _and 2, the resonant spaces and the intake air vibration resonate in the high rotation range of the engine 1, and the intake air filling efficiency is increased. . In other words, when the on-off valve 12 is closed under high load, an output torque characteristic A having a peak a in the low rotation range is obtained as shown in FIG. An output torque characteristic B having the following characteristics is obtained. Here, in these characteristics A and B, output torque peaks a' and b' occur on the high rotation side of the peaks a and b due to the intake inertia effect within the independent intake passages 6 ₁ to 6 ₆ .

Therefore, as shown in FIG. 2, in the high load region of the engine 1 where a large output is required, the first engine rotational speed where both characteristic curves A and B intersect is
The on-off valve 12 is operated in a region lower than N ₁ and in a region higher than the second engine speed N ₂ .
If the on-off valve 12 is controlled to be closed in the intermediate rotation range (and in the middle and low load range), the output torque characteristics at high load will match both of the above characteristics A and B, as shown by the bold line in FIG. The characteristics of the engine are always on the high output side, and as a result, a large output torque can be obtained over a wide rotation range of the engine.

However, when the on-off valve 12 is closed to obtain the characteristic A shown in FIG. 3, the on-off valve 12 blocks the communication path 11 between the first and second surge tanks 7 ₁ and 7 ₂ Despite this, both surge tanks 7 ₁ ,
7 ₂ are communicated by a device passage such as an exhaust gas recirculation passage, the intake vibrations in both surge tanks 7 ₁ and 7 ₂ are mutually attenuated via the device passage. In this case, the above characteristic A
As shown by the chain line in Fig. 3, the characteristic A' becomes a characteristic in which the unevenness is reduced.As a result, by utilizing the characteristic A, the engine speed is low ( _N1 or less) and the output torque is improved. In the region, the output torque decreases in both areas indicated by the shaded area x.

However, in this invention, the first and second
Common first and _second branch passages 17 ₁ of the exhaust gas recirculation passage 14 and the bypass air passage 16 that distribute and supply exhaust gas and bypass air to the surge tanks 7 1 , 7 ₂ ,
17 A cutoff valve 18 is provided between _the on-off valve 1 and the on-off valve 1.
Since the shutoff valve 18 is also closed when the on-off valve 12 is closed, the shutoff valve 18 is closed when the on-off valve 12 is closed.
The first and second surge tanks 7 ₁ and 7 ₂ do not communicate through the branch passages 17 ₁ and 17 ₂ , and when the on-off valve 12 is closed, the upstream sides of the exhaust gas recirculation passage 14 and the bypass air passage 16 are also controlled. They are closed by valves 13 and 15, respectively. Therefore, the first and second surge tanks 7 ₁ and 7 ₂ are completely prevented from communicating with each other and with respect to the upstream sides of the device passages 14 and 16. This prevents the output torque from decreasing as shown by the perspective part x in FIG. 3 in the low engine speed range below _N1 .
The required output torque characteristic shown by the thick line of curve A is obtained.

Here, when the exhaust gas is recirculated to the first and second surge tanks 7 ₁ and 7 ₂ and when bypass air is supplied, the exhaust gas recirculation control valve 13 and the bypass air control valve 15 are respectively opened, and the above-mentioned First,
The shutoff valve 18 between the second branch passages 17 ₁ , 17 ₂ is also opened, so that the exhaust gas or bypass air is evenly distributed to both surge tanks 7 ₁ , 7 ₂ . In this case, the region where exhaust gas is recirculated and the region where bypass air is supplied are respectively indicated by the symbols in FIG. Therefore, in these areas, branch passages 17 ₁ , 17 ₂
The shutoff valve 18 between them is opened, and accordingly, the first and second surge tanks 7 ₁ , 7 ₂ are connected to the branch passages 17 ₁ , 17 _{2 .}
Even if the surge tanks 7 ₁ and 7 ₂ are connected to each other through the communication passage 11, opening the cutoff valve 18 can improve the intake air filling efficiency or the output torque due to the resonance effect. is not affected.

Here, in the above embodiment, the common first,
The second branch passages 17 ₁ and 17 ₂ were connected to the first and second surge tanks 7 ₁ and 7 _2, respectively, but as shown in FIG.
The first and second branch passages 17 ₁ ′, 17 ₂ ′ of 6′ are the first,
They may be connected to the second resonance passages 8 ₁ ′ and 8 ₂ ′, respectively. Further, as shown in FIG. 5, both the exhaust gas recirculation passage 14'' and the bypass air passage ₁₆ '' are separated from each other by a cutoff valve 18 _' '. It may be merged into one branch passage.

Furthermore, FIGS. 6 and 7 show an on-off valve 12 that opens and closes the communication passage 11 between the first and second surge tanks 7 ₁ and 7 ₂ , and an exhaust gas recirculation passage connected to both surge tanks 7 ₁ and 7 ₂ , respectively. 14 and the first and second branch passages 17 ₁ , 17 ₂ of the bypass air passage 16
This shows a specific example of a configuration in which the shutoff valve 18 that communicates with and shuts off the valves is linked together. In this example, the on-off valve 12 and the shutoff valve 18 are attached to a single shaft 20, and the shaft 20 is Both valves 12 and 18 are simultaneously closed and opened simultaneously by a single actuator 19.

Note that the device passage is not limited to the exhaust gas recirculation passage or the bypass air passage shown in each of the above embodiments, and is similarly applicable to cases where other device passages are connected to the intake system.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic diagram of an intake system, FIG. 2 is a diagram showing a control area of the intake system, and FIG. 3 is a diagram showing control characteristics. Figures 4 and 5 are schematic diagrams of main parts showing other configuration examples of the branching part of the device passage, respectively, and Figure 6 is a partially cutaway schematic diagram of the intake device showing a specific configuration example of the interlocking mechanism of the on-off valve and the shutoff valve. Plan view, Figure 7 is Figure 6-
FIG. 2 is a schematic vertical cross-sectional view of the intake device taken along a line. 1... Engine, 3 ₁ , 3 ₂ ... Cylinder group, 4...
Intake device, 6 ₁ to 6 ₆ ...Independent intake passage, 7 ₁ , 7 ₂
...Intake collection part (surge tank), 8 ₁ , 8 ₂ ...
Resonance tube (resonance passage), 11... Communication passage, 12...
Opening/closing valve, 13, 15... Control valve, 14, 16...
Device passage, 17 ₁ , 17 ₂ ... Branch passage, 18
...Shutoff valve.

Claims (1)

[Claims] 1. Two groups of cylinders whose intake order is not consecutive are collected in each intake collecting part by independent intake passages, and a communicating passage is provided that communicates both intake collecting parts, and the communicating passage is connected to a predetermined rotation range of the engine. The intake system for a multi-cylinder engine is provided with an on-off valve that closes at An intake system for a multi-cylinder engine, comprising a cutoff valve connected to each of the provided resonance pipes and for blocking communication between the two branch passages at least when the engine is under high load when the opening/closing valve is closed.