JPH0559249B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an engine intake system, and particularly to a multi-cylinder engine having two independent intake passages for low load and high load. This invention relates to an engine that uses intake pressure waves generated in an intake passage to obtain a supercharging effect from a medium rotation range to a high rotation range of an engine.

(Prior Art) In general, a multi-cylinder engine is equipped with an intake passage having two systems, a low-load intake passage and a high-load intake passage, each branching independently from an enlarged chamber and opening into each cylinder. The intake passage includes a primary valve that is located upstream of the enlarged chamber and changes the amount of intake air flowing through at least the low-load intake passage, and a secondary valve that changes the amount of intake air that flows through the high-load intake passage. When the engine is under low load, only the primary valve is opened and intake air is supplied to each cylinder only from the low-load intake passage, thereby increasing the intake flow rate and improving combustion stability. When the load is high, the secondary valve is also opened to supply intake air from the high-load intake passage, thereby increasing intake air filling efficiency and increasing output. Intake systems are well known.

By the way, the technology of supercharging the intake air by installing a supercharger in the intake passage in order to improve the intake air filling efficiency and output of the engine is well known, but since it is a supercharger device, the structure is large-scale. As the cost increased, so too did the cost increase.

In addition, as disclosed in Japanese Utility Model Publication No. 45-2321, a technique for obtaining a supercharging effect using intake pressure waves generated in the intake passage of an engine has conventionally been used in a single-cylinder engine to reduce the size of the intake pipe. Divided into two different passages, each with a separate intake port, the two intake passages are used when the engine is running at high speeds, and at low engine speeds, the intake passage that is at the later closing position is closed, allowing for early intake. By occluding the intake air, a suitable intake air filling efficiency can be obtained over a wide range of engine speeds by utilizing the supercharging effect caused by the intake air occlusion at the point of maximum intake pressure, which is a function of the intake pipe dimensions and engine speed. Something like this has been proposed.

(Problem to be solved by the invention) However, this device is for a single-cylinder engine, and its structure and operation are unclear, such as how to utilize the intake pressure waves generated in the intake passage. Therefore, it could not be put into practical use immediately. Moreover, since it is a carburetor type engine, there is a drawback that if an attempt is made to obtain a supercharging effect using pressure waves, the length of the intake passage becomes long, resulting in a significant delay in response of the fuel.

Therefore, the inventors of the present invention found that when intake air is started from the intake port, the intake passage becomes negative pressure and an expansion wave is generated, and this expansion wave is reversed into a compression wave. In particular, we focused on the fact that a supercharging effect can be effectively obtained by acting on the intake port at the end of the intake stroke, where intake air blowback occurs (hereinafter referred to as the "intake individual pulsation effect"), and utilize this intake individual pulsation effect. In particular, it is intended to improve the intake air filling efficiency of the engine.

However, in this case, if the above-mentioned intake-specific pulsation effect is set to be obtained at high engine speeds that require high output, the torque valley brought about by the above-mentioned intake-specific pulsation effect will occur on the low-speed side, and instead This will result in a decrease in output during engine rotation. Therefore, it is important to further generate a separate intake-specific pulsation effect that compensates for the torque valley brought about by this intake-specific pulsation effect, in order to improve the output of the engine from the mid-speed range to the high-speed range. desirable.

That is, the present invention provides a multi-cylinder engine having two independent intake passages, one for low load and one for high load, as described above. By obtaining a separate intake pulsation effect in the low-load intake system to compensate for the torque valley brought about by the intake pulsation effect, the fuel consumption can be improved without using a supercharger or the like. While ensuring good responsiveness, it is possible to effectively improve output by increasing intake air filling efficiency in the mid- to high-speed range of the engine with a simple configuration by making slight design changes to the existing intake system. This is the purpose.

(Means for Solving the Problem) In order to achieve this object, the solving means of the present invention includes an expansion chamber, a low-load intake passage that independently communicates the expansion chamber and each cylinder for each cylinder, and a primary valve that is located in the intake passage upstream of the enlarged chamber and changes the amount of intake air flowing through at least the low-load intake passage; and an intake passage that flows through the high-load intake passage. The present invention assumes an intake system for a multi-cylinder engine equipped with a secondary valve that changes the amount of air. A fuel injection nozzle for supplying fuel to at least the low-load intake passage downstream of the enlarged chamber is provided. The passage cross-sectional area of the high-load intake passage is set larger than the passage cross-sectional area of the low-load intake passage, and the passage length l _S of the high-load intake passage from the enlarged chamber to each cylinder is set as above. Passage length of the low-load intake passage from the expansion chamber to each cylinder
l Set smaller than _P. The passage length l _S of the intake passage for high loads and the passage length l _P of the ventilation passage for low loads are
In the high-load intake passage, the expansion wave that occurs at the opening to each cylinder in the engine high speed range of 5000 to 7000 rpm is reversed and reflected in the expansion chamber, and the secondary pulsating wave of the compression wave is generated at the end of the intake stroke of each cylinder. While propagating and supercharging, the low-load intake passage synchronizes with the engine rotation range where the torque trough between the second-order pulsation wave of the compression wave and its third-order pulsation wave in the high-load intake passage occurs. Similarly, the following relational expression is established so that the secondary pulsating wave of the compression wave, which is obtained by inverting and reflecting the expansion wave generated at the opening to each cylinder in the expansion chamber, propagates to the end of the intake stroke of each cylinder to perform supercharging. l _S = (θ _S - θ ₀ ) x (60/360N ₁ ) x (1/4) x a l _P = (θ _P - θ ₀ ) x (60/360N ₂ ) x (1/4) x a l _P = l _S × (1.25±0.125) (Here, θ _S and θ _P are the openings of the high-load and low-load intake valves that open and close the openings of the high-load and low-load intake passages to the cylinders. The period, θ ₀ is the period from the opening of the high-load and low-load intake valves until the expansion wave is substantially generated, and the second pulsation wave of the compression wave, which is the inversion of the expansion wave, is propagated to the opening of each cylinder. _N1 is the engine rotational speed at which intake supercharging is performed by the secondary pulsating wave of the compression wave in the high-load intake passage;
N ₂ is the engine rotation speed (N ₁ > N ₂ ) at which intake air supercharging is performed by the secondary pulsating wave of the compression wave in the low-load intake passage;
a is the propagation velocity of pressure waves).

(Function) As a result, in the present invention, by using two different types of intake pulsation effects in the low-load intake system and the high-load intake system, which are independent of each other, the torque peaks of both systems are not separated. By overlapping both torques, from the high rotation range to the low rotation side, secondary pulsation waves in the high-load intake system, secondary pulsation waves in the low-load intake system, and tertiary pulsation in the high-load intake system. Each inspiratory unique pulsating effect due to waves is successfully generated in turn. In other words, the main strong intake pulsation effect in the high engine speed range in the high-load intake system, and the complementary effect in the low-load intake system to compensate for the torque valley caused by this main intake pulsation effect. Due to the intake air pulsation effect, a supercharging effect can be obtained from the medium speed range to the high speed range of the engine, and a substantially flat high output torque can be obtained.

Here, the limitation of the engine high speed range of 5000 to 7000 rpm to obtain the main intake air pulsation effect is because the maximum output and maximum speed are generally set within this range. This is because it requires high output and is an effective area for improving intake air filling efficiency and output.

In this case, since the low-load intake passage and the high-load intake passage independently communicate the enlarged chamber with each cylinder, pressure waves can be generated individually in each of the low-load and high-load intake passages. propagation, the intake air interference between both intake passages is reduced, and the strong individual intake pulsation effect is maintained, especially in the high-load intake passage, and the above-mentioned supercharging effect can be effectively exhibited.

In addition, in that case, the main intake pulsation effect in the high engine speed range (5000 to 7000 rpm), which requires high output, was obtained in the high-load intake system, meaning that the high-load intake passage was replaced by the low-load intake passage. Because the passage cross-sectional area is larger than that of the one above, and the resistance to the propagation of pressure waves is small, the supercharging effect can be effectively exerted, and as a result, the passage length of the high-load intake passage L _S is shorter than that of the low-load intake passage. Since the passage length L _P of 1 is required to be shorter than that of P, an increase in intake resistance can be prevented, so that the intake air filling efficiency can be effectively increased, which is advantageous in meeting the above output requirement.

Furthermore, since the expansion chamber is located downstream of the primary valve, the pressure waves are not attenuated by the primary valve, and the individual intake pulsation effects can be effectively exhibited.

Furthermore, when setting the fuel supply position by the fuel injection nozzle to obtain a unique intake pulsation effect, the passage length of each intake passage becomes long, resulting in a delay in fuel response. This is to suppress it as much as possible.

In addition, the reason why the secondary pulsating wave is used to obtain the intake-specific pulsating effect in the present invention is that while the primary pulsating wave has the above-mentioned effect, the passage length of the low-load and high-load intake passages is too long and is twice as long as the secondary pulsating wave, which makes it difficult to mount on a vehicle and tends to increase intake resistance. On the other hand, the passage length of the tertiary pulsating wave is shortened to 2/3 of that of the secondary pulsating wave, but on the other hand, the above-mentioned effect on the secondary pulsating wave is reduced by about 15 to 25%, and the intake air The resistance doesn't change much. For this reason, the purpose is to effectively exhibit the unique pulsation effect of the intake air while making the passage length as short as possible.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIGS. 1 and 2 show a first embodiment as a basic structural example in which the present invention is applied to a dual induction type four-valve two-cylinder four-stroke engine. In the figure, 1A and 1B are a first cylinder and a second cylinder, and 2 is a combustion chamber formed by a cylinder 3 and a piston 4 in each cylinder 1A, 1B.

Reference numeral 5 denotes a main intake passage whose one end opens to the atmosphere via an air cleaner 6 to supply intake air to each cylinder 1A, 1B, and the main intake passage 5 is equipped with an air flow meter 7 for detecting the amount of intake air. It is arranged. The main intake passage 5 has an enlarged chamber 8 downstream of the air flow meter 7, and the enlarged chamber 8 connects the cylinders 1A and 1B to low-load intake passages 9a and 9b.
and high-load intake passages 10a, 10b are independently branched, and each cylinder 1A,
It opens into the combustion chamber 2 of 1B.

The main intake passage 5 upstream of the enlarged chamber 8 and downstream of the air flow meter 7 is provided with an intake passage 9 that opens in response to an increase in engine load and opens fully when the load exceeds a predetermined load.
Primary valve 13 that changes the amount of intake air flowing through a and 9b
is installed. Further, each of the high-load intake passages 10a, 10b downstream of the expansion chamber 8 is opened when the engine load exceeds a predetermined value, and changes the amount of intake air flowing through the high-load intake passages 10a, 10b when the engine load is high. Secondary valves 14, 14 are arranged so as to be interlocked with each other. Further, in each of the low-load intake passages 9a and 9b downstream of the enlarged chamber 8, there is provided a solenoid valve type fuel injection nozzle 15 whose fuel injection amount is controlled according to the amount of intake air based on the output of the air flow meter 7. , 15 are arranged.

Further, each of the high-load intake ports 12 is provided with a high-load intake valve 16 that opens and closes the high-load intake port 12 during the intake stroke, and although not shown, each of the low-load intake ports 11 A low-load intake valve is provided to open and close the low-load intake port 11 during the intake stroke. In addition, each cylinder 1
In A and 1B, one end of 17 and 18 opens to the atmosphere, and the other end opens to the combustion chamber 2 of each cylinder 1A and 1B via exhaust ports 19 and 20 to discharge exhaust gas from the combustion chamber 2. In the first and second exhaust passages, each of the exhaust ports 19 and 20 is provided with exhaust valves 21 and 21 that open and close the exhaust ports 19 and 20 during the exhaust stroke.

And each of the above-mentioned high load intake passages 10a, 10
The minimum passage cross-sectional area A _S of b is each low-load intake passage 9
It is set larger than the minimum passage cross-sectional area A _P of a and 9b (A _S > A _P ), and each high-load intake passage 10
Passage length l of a and 10b _S is each low load intake passage 9
The length of the passages a and 9b is set shorter than l _P (l _S < l _P ), especially for high-load intake passages 10 a and 10 b.
The pressure waves are propagated effectively by reducing their attenuation.

Further, the volume of the expansion chamber 8 is set to be 0.5 times or more the total displacement of the engine. this is
This is because if it is less than 0.5 times, the reversal effect between the expansion wave and the compression wave cannot be obtained. In addition, the expansion chamber 8 functions as a surge tank for intake air during transient operations such as acceleration or deceleration of the engine, and prevents misfires due to breathing during acceleration or fuel overflow during deceleration. to ensure good fuel responsiveness.

Further, the opening timing of the high-load intake valve 16 (opening timing of the high-load intake port 12) and the opening timing of the low-load intake valve (not shown) (opening timing of the low-load intake port 11) The valve closing timings of both (the closing timings of the intake ports 11 and 12) are also set to be approximately the same.

In addition, each of the above-mentioned high-load intake passages 10a, 10
b passage length l _S , that is, the high-load intake passage 10
Combustion chamber 1 from the opening end face of a, 10b to the enlarged chamber 8
The passage length l _S to the opening to the intake port 12 (high-load intake port 12) is determined by l _S = (θ _S -θ ₀ )×(60/360N ₁ )×(1/4)×a . . . It is set to a value determined from the equation (). In the above equation (), θ _S is the opening period of the high-load intake valve 16, and θ ₀ is the period during which the expansion wave is substantially generated from the opening of the high-load intake port 12 due to the opening of the high-load intake valve 16. The closing of the high-load intake valve 16 (the high-load Closing of load intake port 12)
The total temperature is about 60 to 100 degrees. Therefore, (θ _S −θ ₀ ) represents the rotation angle of the crankshaft required from the generation of the expansion wave to the propagation of the secondary pulsation of the compression wave. Further, _N1 is the reference engine speed set between 5000 and 7000 rpm, and 60/ _360N1 represents the time (seconds) required to rotate 1 degree. Moreover, 1/4 represents the reciprocal of the stroke in which the secondary pulsation makes two reciprocations. Furthermore, a is the propagation velocity (sound velocity) of the pressure wave, which is 343 m/s at 20°.

Furthermore, the passage length l _P of each of the low-load intake passages 9a, 9b, that is, the low-load intake passages 9a, 9b.
The passage length l _P from the opening end face to the enlarged chamber 8 to the opening to the combustion chamber 2 (low-load intake port 11) is
The energy generated around (N ₁ /1.25) rpm in the high-load intake passages 10a and 10b,
1/(1.25±0.125) of the reference rotation speed _N1 is set between 5000 and 7000 rpm to compensate for the torque valley caused by the main intake pulsation effect.
The above () to obtain the intake unique pulsation effect due to the complementary secondary pulsation wave when the engine rotates at rpm
It is set to a value determined by the formula l _P = (θ _P −θ ₀ )×(60/360N ₂ )×(1/4)×a (), which is similar to the formula. That is, in the above equation (), θ _P is the opening period of the low-load intake valve, and as described above, θ _P =θ _S. Also, N ₂ is the engine speed, N ₂ = N ₁ / (1.25±
0.125), so l _P = l _S × (1.25±0.125).

Note that in the above equations () and (), the influence of the flow of intake air on the propagation of pressure waves is ignored. This is because the flow velocity is smaller than the speed of sound and causes almost no change in the flow in the intake passage.

Next, to explain the operation of the first embodiment, in the high engine rotation range of 5000 to 7000 rpm, which requires high output, the secondary valves 14, 14 are opened, and the low-load intake passages 9a, 9b are operated under high load. The intake passages 10a and 10b for each cylinder are also opened, and each cylinder 1A and 1B
On the other hand, intake air is also supplied from the high-load intake passages 10a and 10b. At that time, each cylinder 1A,
1B, after the high-load intake valve 16 is opened, an expansion wave is generated in each high-load intake passage 10a, 10b due to the start of intake from the high-load intake port 12. This expansion wave is transmitted from the expansion chamber 8 to each cylinder 1A, 1
By setting the passage length _lS of the high-load intake passages 10a and 10b leading to B to the value determined by the above formula () based on the engine high speed range of 5000 to 7000 rpm, the high-load intake passage 10a ,10
b → Expansion chamber 8 (reflects as a compression wave and reflects it) → High load intake passages 10a, 10b → Combustion chamber 2 (reflects as an expansion wave and reflects it) → High load intake passages 10a, 10
b → Expansion chamber 8 (reflected as a compression wave) → Passes through the high-load intake passages 10a and 10b to the high-load intake port 12 at the end of the intake stroke of each cylinder 1A and 1B as a secondary pulsating wave of the compression wave (Note that the reversal from the compression wave to the expansion wave in the combustion chamber 2 occurs when the piston is moving relatively toward the bottom dead center and the volume of the combustion chamber 2 is sufficiently expanded. (performed stably). As a result, this secondary pulsating compression wave causes the high-load intake port 12 at the end of the intake stroke to
The blowback of the intake air is suppressed and the intake air is forced into the combustion chamber 12, which results in supercharging. Therefore, due to the supercharging effect due to the individual intake pulsation effect in the high-load intake system of each cylinder 1A, 1B, the charging efficiency in the high engine speed range of 5000 to 7000 rpm increases and the output can be improved. can.

On the other hand, in the engine speed range where the engine speed is lower than the above 5000 to 7000 rpm by a ratio of (1.25±0.125), intake is started from the low-load intake ports 11 of each cylinder 1A and 1B in the same way as above. The expansion waves generated in the intake passages 9a, 9b reduce the passage length _lP of the low-load intake passages 9a, 9b from the expansion chamber 8 to each cylinder 1A, 1B by _lP = _lS × (1.25±
0.125), the low-load intake passages 9a, 9b → expansion chamber 8 (reflected as a compression wave) → low-load intake passages 9a, 9b → combustion chamber 2
(Inverted and reflected as an expansion wave) →Low load intake passage 9
a, 9b → Expansion chamber 8 (inverted to compression wave and reflected) →
The compression wave 2 passes through the low-load intake passages 9a and 9b.
The next pulsating wave propagates to the low-load intake port 11 at the end of the intake stroke of each cylinder 1A, 1B (also in this case, the reversal from the compression wave to the expansion wave in the combustion chamber 2 is caused by This is done stably because it is in a sufficiently expanded state), and supercharging is also performed.
As a result, due to the intake individual pulsation effect in the low-load intake system of each cylinder 1A, 1B itself, the engine high rotation side generated by the intake individual pulsation effect due to the secondary pulsation wave in the high-load intake system. Intake air filling efficiency in the engine rotation range where the torque trough is generated between the peak of torque increase at , and the peak of torque increase at low engine speed, which is generated by the unique pulsation effect of the intake due to the tertiary pulsation wave. It is possible to improve the output by fully compensating for the

Therefore, in each cylinder 1A, 1B, the third
As shown in the figure, the engine speed range (5000~
In addition to the output improvement obtained by the main intake individual pulsation effect (indicated by the broken line) due to the secondary pulsation wave in the high-load intake system (at 7000rpm), the intake individual pulsation effect due to this main secondary pulsation wave The engine rotation generated by the torque trough formed between the peak of torque increase on the high engine rotation side generated by this and the peak of torque increase on the low engine rotation side generated by the intake-specific pulsation effect due to the tertiary pulsation wave. Complementary intake-specific pulsation effect due to secondary pulsation waves in the low-load intake system (shown by solid line)
This makes it possible to compensate for the decrease in output at the torque trough and improve the output, thereby increasing the output with almost flat high-torque characteristics over a wide range from the mid- to high-speed range of the engine. . still,
In Figure 3, the main intake individual pulsation effect due to the secondary pulsation wave in the high-load intake system is obtained based on 6000 rpm, and the complementary intake individual pulsation effect due to the secondary pulsation wave in the low-load intake system is obtained.
This shows the engine output torque characteristics when set to obtain 4800 rpm as a reference.

In this case, the low load intake passages 9a and 9b and the high load intake passage 10a in each cylinder 1A and 1B,
10b are independently connected to the expansion chamber 3 and each cylinder 1A,
1B, each of the low-load and high-load intake passages 9a, 9b, 10a, 10
Since the pressure waves are propagated individually in the intake passages 10a and 10b, there is less interference between the intake passages 9a and 10a, and 9b and 10b, especially in the high-load intake passages 10a and 10b.
The strong intake-specific pulsation effect at 10b is maintained, and the supercharging effect can be effectively exhibited.

In addition, in that case, the main intake pulsation effect in the high engine speed range (5000 to 7000 rpm) that requires high output is obtained in the high-load intake system, that is, the high-load intake passages 10a and 10b are The passage area is larger than that of the high-load intake passages 9a, 9b, and the resistance to the propagation of pressure waves is small, so the supercharging effect can be effectively exerted. Since l _S is shorter than the passage length l _P of the low-load intake passages 9a and 9b and an increase in intake resistance can be prevented, the intake air filling efficiency can be effectively increased, which is advantageous in meeting the above output requirements. It is.

Furthermore, since the expansion chamber 8 is located downstream of the primary valve 13, the pressure waves are not attenuated by the primary valve 13, and the individual pulsation effects of each intake air can be effectively exerted. .

Furthermore, the fuel injection nozzle 15 as a fuel supply device includes a low-load intake passage 9a downstream of the enlarged chamber 8;
9b, it is possible to prevent the deterioration of fuel response due to the increase in the intake passage length _lP in order to obtain the intake-specific pulsation effect, and to ensure good fuel response. Low-load intake passage 9 that can supply intake air and fuel in the operating range
Only a and 9b need be installed, and the fuel supply device can be simplified.

Further, the supercharging effect due to the individual intake pulsation effect is determined by the position of the expansion chamber 8 and the low-load intake passages 9a, 9b leading from the expansion chamber 8 to each cylinder 1A, 1B.
and the passage length of high-load intake passages 10a and 10b
This is achieved by setting _lP , _lS , etc. as described above, and since a supercharger etc. is not required, only a slight design change to the existing intake system is required, and the structure is extremely simple. Therefore, it can be implemented easily and at low cost.

It should be noted that the present invention is not limited to the first embodiment described above, but also includes various other modifications. 4 and 5 show second and third embodiments as modified examples of the first embodiment (in addition, the first embodiment
The same parts as those in the embodiment are given the same reference numerals and the explanation thereof will be omitted). In the second embodiment shown in FIG. 4, a low-load intake passage 9 is provided for each cylinder 1A, 1B.
a, 9b and the high-load intake passages 10a, 10b are connected through a common single intake port 23 instead of the independent low-load and high-load intake ports 11, 12 as in the first embodiment. The combustion chamber 2 is opened, and the intake port 23 is opened and closed by a single intake valve 24. Also, in Figure 5, 3
In the embodiment, the expansion chambers are provided independently in the expansion chamber 8a of the low-load intake system and the expansion chamber 8b of the high-load intake system. Even in these cases, the passage lengths l _S , l _P of the high-load intake passages 10a, 10b and the low-load intake passages 9a, 9b
By setting the expressions () and () above, similar effects can be obtained.

Furthermore, although the above embodiments have been described as examples in which the present invention is applied to a two-cylinder engine, it goes without saying that the present invention can also be applied to various other multi-cylinder engines with dual induction intake systems.

(Effects of the Invention) As explained above, according to the present invention, in a multi-cylinder engine equipped with two independent intake passages, one for low load and one for high load, downstream of the enlarged chamber, the high load intake system In addition, in the high engine speed range of 5000 to 7000 rpm, the supercharging effect is obtained by the strong intake pulsation effect mainly due to the secondary pulsation wave. A torque trough is created between the peak of torque up on the high engine speed side generated by the intake pulsation effect and the peak of torque up on the low engine speed side generated by the intake pulsation effect due to its tertiary pulsation wave. Since a supercharging effect is obtained in the engine rotation range to compensate for the above-mentioned torque valley by the intake air pulsation effect, good response of the fuel is ensured without the need for a supercharger etc. However, even with a simple configuration made by slightly changing the design of the existing intake system, it is possible to effectively improve the output with almost flat high torque characteristics over a wide range from the mid- to high-speed engine speed range. Therefore, it can greatly contribute to the ease of implementation of measures to improve engine output and cost reduction.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIGS. 1 and 2 are an explanatory diagram of the overall configuration and a schematic diagram of the essential parts of the first embodiment, FIG. 3 is a diagram showing output torque characteristics, and FIG. 4 is a diagram showing an output torque characteristic. 2 is a diagram equivalent to FIG. 2 showing the second embodiment, and FIG. 5 is a diagram equivalent to FIG. 1 showing the third embodiment. 1A...1st cylinder, 1B...2nd cylinder, 2...
Combustion chamber, 5... Main intake passage, 8, 8a, 8b...
Expansion chamber, 9a, 9b...Low load intake passage, 10
a, 10b...Intake passage for high load, 13...Primary valve, 14...Secondary valve, 15...Fuel injection nozzle.

Claims (1)

[Scope of Claims] 1. An expansion chamber, a low-load intake passage and a high-load intake passage that independently communicate the expansion chamber with each cylinder for each cylinder, and an intake passage upstream of the expansion chamber. Intake air of a multi-cylinder engine, comprising: a primary valve located in an intake passage that changes the amount of intake air flowing through at least the low-load intake passage; and a secondary valve that changes the amount of intake air that flows through the high-load intake passage. The device includes a fuel injection nozzle that supplies fuel to at least the low-load intake passage downstream of the expansion chamber, and the passage cross-sectional area of the high-load intake passage is larger than the passage cross-sectional area of the low-load intake passage. In addition, the passage length _lS of the high-load intake passage from the expansion chamber to each cylinder is set to be smaller than the passage length _lP of the low-load intake passage from the expansion chamber to each cylinder. Then, the passage length l _S of the high-load intake passage and the passage length l _P of the low-load ventilation passage are the same as that of the high-load intake passage.
In the high engine rotation range of 5000 to 7000 rpm, the expansion wave generated at the opening to each cylinder is reversed in the expansion chamber, and the secondary pulsating wave of the compression wave propagates at the end of the intake stroke of each cylinder to perform supercharging. At the same time, the low-load intake passage synchronizes with the engine rotation range where the torque trough between the secondary pulsating wave of the compression wave and its tertiary pulsating wave in the high-load intake passage occurs, and the same applies to each cylinder. The following relational expression l _S = (θ _S -θ ₀ ) × (60/360N ₁ ) × (1/4) × a l _P = (θ _P -θ ₀ ) × (60/360N ₂ ) × (1/4) × a l _P = l _S × (1.25±0.125) (Here, θ _S and θ _P are the opening periods of the high-load and low-load intake valves that open and close the openings of the high-load and low-load intake passages to the cylinders, and θ ₀ is the high-load and low-load intake valve opening periods. The period from the opening of the intake valve for load and low load until the expansion wave is substantially generated, and the period when the secondary pulsating wave of the compression wave, which is the inversion of the expansion wave, is propagated to the opening of each cylinder for high load. and the period until the low-load intake valve closes, _N1 is the engine rotational speed at which intake supercharging is performed by the secondary pulsation wave of the compression wave in the high-load intake passage,
N ₂ is the engine rotation speed (N ₁ > N ₂ ) at which intake air supercharging is performed by the secondary pulsating wave of the compression wave in the low-load intake passage;
(a is the propagation velocity of pressure waves).