JPH0452377B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an intake system for an engine, and particularly to an intake passage in a multi-cylinder engine equipped with two independent intake passages, one for low load and one for high load. This relates to a device that uses intake pressure waves generated within the engine to obtain a supercharging effect when the engine is under high load and high rotation speed.

(Prior Art) In general, in a multi-cylinder engine, two systems of low-load intake passages branch from an enlarged chamber and open to each cylinder independently through low-load and high-load intake ports. An intake passage having a high load intake passage having a larger passage area than the load intake passage, the intake passage being located upstream of the enlarged chamber and changing at least the amount of intake air flowing through the low load intake passage. It has a secondary valve and a secondary valve that changes the amount of intake air flowing through the high-load intake passage.When the engine is under low load, only the primary valve is opened and intake air is taken only from the low-load intake passage. By supplying this to each cylinder, the intake flow rate is increased and combustion stability is improved.
A so-called dual-induction intake system is well known, which aims to improve filling efficiency and output by opening the next valve and supplying intake air from the high-load intake passage as well. .

By the way, the technology of supercharging the intake air by installing a supercharger in the intake passage in order to improve the filling efficiency and output of the engine is well known, but since it is a supercharger device, the structure is large-scale. At the same time, there was a dislike of increasing costs.

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, the supercharging effect caused by the occlusion of the intake air at the maximum pressure of the intake air, which is a function of the intake pipe dimensions and the engine speed, is utilized to obtain a suitable charging efficiency over a wide range of engine speeds. It has been proposed that

(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.

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 charging efficiency of the engine.

In that case, if the opening timings of the low-load intake port and the high-load intake port of each cylinder are different, the blowback of the residual exhaust gas in the combustion chamber will concentrate on the one that opens earlier, and this will cause the opening timing to be later. It was found that the negative pressure generated by the start of inspiration becomes larger in the first direction, a strong expansion wave can be generated, and the unique pulsation effect of inspiration becomes large. To explain this in detail, for example, 4
In a cycle reciprocating engine, if the opening timing of the high-load intake port is set later than the opening timing of the low-load intake port, as shown in Figure 5, when the low-load intake port opens, the residual exhaust gas in the combustion chamber Gas blowback concentrates on the low-load intake port, and the pressure in the combustion chamber decreases accordingly. Then, accompanied by the pressure reducing effect of the subsequent downward movement of the piston, a large negative pressure is generated in the combustion chamber when the high-load intake port is opened. Therefore, at the opening of the high-load intake port, the pressure close to atmospheric pressure immediately before the opening suddenly changes to the above-mentioned large negative pressure as the high-load intake port opens, and a strong expansion wave is generated here. will occur.

For these reasons, the present invention has been developed to open the high-load intake port later than the low-load intake port in a multi-cylinder engine equipped with two intake passages, one for low load and one for high load. By effectively obtaining the intake pulsation effect in the high-load intake system when the engine is under high load and at high rotation speeds, which require high output, it is possible to make slight design changes to the existing intake system without using a supercharger, etc. The purpose of this invention is to effectively increase the charging efficiency and improve the output when the engine is under high load and high rotation speed, even with a simple configuration.

(Means for Solving the Problem) In order to achieve this object, the solution means of the present invention includes an expansion chamber, and downstream of the expansion chamber, a low-load intake port and a high-load intake port are connected to each cylinder independently. an intake passage having a low-load intake passage and a high-load intake passage that are opened at the same time; The present invention is based on an intake ventilation system for a multi-cylinder engine that has a secondary valve and a secondary valve that changes the amount of intake air flowing through a high-load intake passage. A fuel injection nozzle is provided to supply fuel to the low-load intake passage downstream of the enlarged chamber. 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 of the high-load intake passage from the expansion chamber to each cylinder is set to the expansion chamber. The passage length is set to be smaller than the passage length of the low-load intake passage leading from to each cylinder. The opening timing of the high-load intake port is set to be later than the opening timing of the low-load intake port. The passage _length of the intake passage for high loads above is 5000
In the engine high rotation range of ~7000 rpm, the expansion wave generated by the start of intake at the high-load intake port of each cylinder is reversed and reflected in the expansion chamber, and the secondary pulsating wave of the compression wave is generated for each cylinder at the end of the intake stroke. The formula below l _S = (θ _S - θ _O ) x (60/360N) x (1/4) x a (here, θ _S is The opening period of the high-load intake valve that opens and closes the load intake port, θ _O , is the period from the opening of the high-load intake valve until the expansion wave substantially occurs, in order to effectively perform supercharging. N is the engine speed, and a is the invalid period, which is the sum of the period from just before closing to the closing of the high-load intake valve in which the secondary pulsating wave of the compression wave, which is the inversion of the expansion wave, is propagated. (propagation velocity of pressure waves).

(Function) As a result, in the present invention, the 5000
In the high engine speed range of ~7000 rpm, the secondary valve opens both the low-load intake passage and the high-load intake passage, and intake air is supplied to each cylinder from the high-load intake passage as well. There is. At this time, after the high-load intake valve is opened in each cylinder, an expansion wave is generated in each high-load intake passage due to the start of intake from the high-load intake port. The generation of this expansion wave is
Because the low-load intake port opens earlier than the high-load intake port, at the start of each cylinder's intake stroke, the blowback of residual exhaust gas from the combustion chamber concentrates on the low-load intake port. Accordingly, the generation of negative pressure due to the start of intake from the high-load intake port becomes larger and stronger. Then, this strong expansion wave propagates to the high-load intake port of each cylinder at the end of the intake stroke as a secondary pulsating wave of the compression wave that is reversed and reflected in the expansion chamber. As a result, due to the unique intake pulsation effect caused by this strong secondary pulsating compression wave, the blowback of intake air from the high-load intake port at the end of the intake stroke is suppressed, and the intake air is strongly pushed into the combustion chamber, resulting in strong supercharging. It will be done.

In addition, in that case, the high-load intake passage, which is the pressure wave propagation path for obtaining the above-mentioned intake-specific pulsation effect, has a larger passage cross-sectional area than the low-load intake passage,
Moreover, since the passage length is short, the resistance to the propagation of pressure waves is small, so that the above-mentioned intake-specific pulsation effect can be more effectively exerted in a high-load intake system.

Furthermore, since the fuel injection nozzle is installed in the low-load intake passage downstream of the enlarged chamber, only the low-load intake passage, which can supply intake air and fuel in all operating ranges, can be installed. The supply device can be simplified.

Here, the engine high speed range to obtain the above-mentioned intake air pulsation effect is limited to 5000 to 7000 rpm.
Since the maximum output and maximum speed are generally set within this range, this is a high load, high rotation range of the engine, which requires high output, and is an effective range for improving charging efficiency and output.

Furthermore, the reason why the low-load intake passage and the high-load intake passage are made independent downstream of the expansion chamber is as follows.
This is to prevent the pressure waves generated in the low-load and high-load intake passages of each cylinder from dispersing to the other, or from interfering with each other and weakening. This is because the opening/closing timing and length of the intake port are not the same as that of the intake passage due to the differences in requirements in the dual induction intake system, and the pressure waves of one are attenuated by the other.

In addition, the reason why secondary pulsation is used in obtaining the intake-specific pulsation effect in the present invention is that while primary pulsation has the above-mentioned effect, the passage length of the high-load intake passage becomes too long. 2 for the case of next pulsation
Since it is twice as long, it is difficult to mount it on a vehicle, and it also tends to increase intake resistance. On the other hand, with tertiary pulsation, the passage length is shortened to 2/3 of that of secondary pulsation, but on the other hand, the above effect is reduced by about 15 to 25% compared to secondary pulsation, and the intake resistance is not as great. does not change. 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-cycle 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 from the enlarged chamber 8, low-load intake passages 9a, 9b and high-load intake passages 10a, 10b are separated for each cylinder 1A, 1B. It branches and opens into the combustion chamber 2 of each cylinder 1A, 1B via a low-load intake port 11 and a high-load intake port 12, respectively.

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 in conjunction with each other. Further, at the downstream ends (near the opening to the combustion chamber 2) of each of the low-load intake passages 9a, 9b downstream of the enlarged chamber 8, fuel is supplied according to the amount of intake air based on the output of the air flow meter 7. Solenoid valve type fuel injection nozzle 1 with controlled injection amount
5 and 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, 17 and 18 have one end open to the atmosphere and the other end open 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
The passage length ls of a and 10b 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 damping of the engine, and prevents misfires caused by breathing during acceleration or fuel overflow during deceleration. This ensures good response of the fuel.

That is, downstream of the primary valve 13, each cylinder 1
An enlarged chamber 8 having a large volume (the above-described predetermined volume) in which the low-load intake passages 9a and 9b and the high-load intake passages 10a and 10b of A and 1B are gathered, respectively.
Therefore, when the primary valve 13 is at a low opening, negative intake pressure is generated and stored in the expansion chamber 8, and when the primary valve 13 is at a high opening, atmospheric pressure is generated in the expansion chamber 8. A similar intake pressure is generated and stored. Therefore, during acceleration operation, when the opening of the primary valve 13 rapidly increases and opens, the negative pressure of the intake air that had been stored in the expansion chamber 8 upstream causes the main intake air to flow upstream of the expansion chamber 8. By rapidly increasing the intake flow velocity in the passage 5 and increasing the responsiveness of the air flow meter 7, a rapid fuel increase (fuel responsiveness) can be ensured. In addition, during deceleration operation, when the opening degree of the primary valve 13 suddenly decreases and closes, the intake pressure close to atmospheric pressure that has been stored in the expansion chamber 8 upstream causes the main valve upstream of the expansion chamber 8 to By rapidly reducing the intake flow velocity in the intake passage 5 and increasing the responsiveness of the air flow meter 7, a rapid fuel loss (fuel responsiveness) can be ensured.

Furthermore, the valve opening timing of the above-mentioned low load intake valve (not shown) (opening timing of the low load intake port 11)
is set to be earlier than the opening timing of the high-load intake port 16 (the opening timing of the high-load intake port 12), and the blowback of the residual exhaust gas in the combustion chamber 2 is set to be earlier than the opening timing of the high-load intake port 16. This causes expansion waves to be generated more strongly at the start of intake on the high-load intake port 12 side.
Also, the closing timing of the high-load intake valve 16 (the closing timing of the high-load intake port 12) is the closing timing of the low-load intake valve (the closing timing of the low-load intake port 11).
This is set to be later than that of the high-load intake system by preventing the secondary pulsating compression wave that propagated to the high-load intake port 12 at the end of the intake stroke from blowing through from the low-load intake port 11. The intake air pulsation effect is effectively exhibited.

In addition, each of the above-mentioned high-load intake passages 10a, 10
b passage length ls, 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 ls to the opening to 2 (high-load intake port 12) is l _S (θ _S −θ _O ) so as to obtain the second-order intake unique pulsation effect in the rotation range of 5000 to 7000 rpm. ×(60/360N) ×(1/4)×a…() It is set to a value obtained from the formula. In the above equation (), θ _S is the opening period of the high-load intake valve 16, and θ _O 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. In order to effectively perform supercharging, the high-load intake valve 16 is closed (the high-load intake port 12 The invalid period, which is the sum of the period immediately before opening (opening) and the period immediately before closing, is about 60 to 100 degrees. Therefore, (θ _S −θ _O ) 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, N is the engine rotational speed, N=5000 to 7000 rpm, and 60/360N represents the time (seconds) required to rotate 1 degree. Also, 1/4 is 2
Represents the reciprocal of the stroke in which the next pulsation goes back and forth twice. Furthermore, a is the propagation velocity (sound velocity) of the pressure wave, and at 20°C a
=343m/s.

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

Next, to explain the operation of the first embodiment, when the engine rotates at a high speed of 5,000 to 70,000 rpm, which requires high output, the secondary valves 14, 14 are opened, and the intake passages 9a, 9b for low loads as well as the intake passages for high loads are The intake passages 10a, 10b are also opened, and each cylinder 1A, 1
Intake air is also supplied to B from the high-load intake passages 10a and 10b. At that time, each cylinder 1
After opening the high-load intake valve 16 at A and 1B,
When intake starts from the high-load intake port 12, an expansion wave is generated in each of the high-load intake passages 10a, 10b. This expansion wave occurs because the opening timing of the low-load intake port 11 is earlier than the opening timing of the high-load intake port 12.
At the start of the intake stroke, the blowback of the residual exhaust gas in the combustion chamber 2 is concentrated on the low-load intake port 11 side, and the negative pressure generated by the start of intake from the high-load intake port 12 is correspondingly large and strong. Become. This strong expansion wave causes the expansion chamber 8 and each cylinder 1A,
By setting the passage length ls of the high-load intake passages 10a and 10b leading to 1B to the value determined by the above formula () based on the high engine rotation of 5000 to 7000 rpm, the high-load intake passages 10a, 1
0b → Expansion chamber 8 (inverts and reflects compression waves) → High load intake passages 10a, 10b → Combustion chamber 2 (inverts and reflects expansion waves) → High load intake passages 10a, 1
0b → Expansion chamber 8 (reflected as a compression wave) → Propagates to the high-load intake port 12 at the end of the intake stroke of each cylinder 1A, 1B as a secondary pulsation of the compression wave via the high-load intake passages 10a, 10b do. As a result, this strong secondary pulsating compression wave suppresses the blowback of intake air from the high-load intake port 12 at the end of the intake stroke, and forces the intake air strongly into the combustion chamber 2. Moreover, the closing timing of the high-load intake port 12 is set later than that of the low-load intake port 11, so that the above-mentioned
In combination with preventing the next pulsating compression wave from blowing through from the low-load intake port 11, strong supercharging is performed.

Therefore, when the engine rotates at a high speed of 5000 to 7000 rpm, a strong supercharging effect can be obtained by generating an effective and strong intake pulsation effect in the high-load intake system of each cylinder 1A and 1B. Therefore, the third
As shown in the figure, the charging efficiency increases at high engine speeds of 5,000 to 7,000 rpm, that is, at high engine load and high speeds, and the output can be improved. still,
FIG. 3 shows the output torque characteristics of the engine when the high-load intake system is set to obtain a second-order intake-specific pulsation effect with an engine speed of 6000 rpm as a reference.

In that case, the high-load intake passage 10, which is a pressure wave propagation path for obtaining the intake-specific pulsation effect,
The passages a and 10b have a larger passage area and a shorter passage length than the low-load intake passages 9a and 9b, so the resistance to the propagation of pressure waves is small, and therefore the above-mentioned intake-specific pulsation effect can be used for high-load applications. It can be made more effective in the intake system.

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 is provided at the downstream end (near the opening to the combustion chamber 2), and its passage length _lP is long, so that the airflow meter 7 placed upstream of the expansion chamber 8 is It is possible to prevent deterioration of fuel responsiveness due to response delay (response delay in fuel supply corresponding to the changed amount of air introduced into the combustion chamber 2), and ensure good fuel responsiveness. Only the low-load intake passages 9a and 9b, which can supply intake air and fuel in all operating ranges, are installed, and the fuel supply system can be simplified.

In addition, the supercharging effect due to the intake individual pulsation effect is determined by the position of the expansion chamber 8, the opening timing of each intake port 11, 12, and the high-load intake passages 10a, 10b from the expansion chamber 8 to each cylinder 1A, 1B. passage length of
Obtained by setting ls etc. as above,
Since a supercharger or the like is not required, only slight design changes to the existing intake system are required, and the structure is extremely simple, so 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. FIG. 4 shows a second embodiment of the present invention (the same parts as in the first embodiment are given the same reference numerals and their explanations are omitted). Instead of one expansion chamber 8, an expansion chamber 8a for the low-load intake system and an expansion chamber 8b for the high-load intake system are provided independently.
Also in this example, the opening timing of the low-load intake port 11 is set earlier than that of the high-load intake port 12, and the passage length of the high-load intake passages 10a and 10b is
By setting ls using the above equation ( ), the same effects as in the first embodiment can be achieved.

Further, 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 intake passages, one for low load and one for high load, downstream of the enlarged chamber, the high load intake system In order to obtain a unique intake pulsation effect in the engine high speed range of ~7000 rpm, a high-load intake passage with a large passage cross-sectional area and short passage length is used to utilize the secondary pulsation, and for this purpose, a high-load intake passage with a large passage cross-sectional area and a short passage length is used. By opening the intake port later than the low-load intake port and suppressing the attenuation of the expansion wave due to residual gas, the unique pulsation effect of the intake is sufficiently and effectively produced to obtain a strong supercharging effect. did. Therefore, it is possible to effectively improve the output at high engine load and high rotation speeds even with a simple configuration that requires only slight design changes to the existing intake system without the need for a supercharger, etc., and thus increases the engine output. This can greatly contribute to easier implementation of improvement measures and cost reduction.

[Brief explanation of the drawing]

The drawings show embodiments of the invention, FIGS. 1 and 2.
The figures are an explanatory diagram of the overall configuration and a schematic diagram of the main parts showing the first embodiment, Figure 3 is a diagram showing the output torque characteristics, and Figure 4 is a diagram showing the output torque characteristics.
The figure is a diagram corresponding to FIG. 1 showing the second embodiment, and FIG. 5 is an explanatory diagram showing changes in combustion chamber pressure with respect to valve timing. 1A...first cylinder, 1B...second cylinder, 2...combustion chamber, 5...main intake passage, 8, 8a, 8b...expansion chamber,
9a, 9b...Low load intake passage, 10a, 10b
...Intake passage for high load, 11...Intake port for low load, 12...Intake port for high load, 13...Primary valve,
14...Secondary valve, 15...Fuel injection nozzle.

Claims (1)

[Claims] 1. An enlarged chamber, and a low-load intake passage and a high-load intake passage that open downstream of the enlarged chamber to each cylinder independently through low-load and high-load intake ports. The intake passage includes a primary valve located upstream of the enlarged chamber that changes the amount of intake air flowing through at least the low-load intake passage, and a primary valve that changes the amount of intake air that flows through the high-load intake passage. The intake system for a multi-cylinder engine having a secondary valve is provided with a fuel injection nozzle that supplies fuel to a low-load intake passage downstream of the enlarged chamber, and the passage cross-sectional area of the high-load intake passage is The cross-sectional area of the load intake passage is set to be larger than the passage length of the high-load intake passage from the enlarged chamber to each cylinder, and the passage length of the low-load intake passage from the enlarged chamber to each cylinder is set to be larger than that of the load intake passage. The opening timing of the above-mentioned high-load intake port is set to be later than the opening timing of the above-mentioned low-load intake port, and the passage length l _S of the above-mentioned high-load intake passage is set to 5000~
In the high-speed engine rotation range of 7000 rpm, the expansion wave generated by the start of intake at the high-load intake port of each cylinder is inverted and reflected in the expansion chamber, and the secondary pulsating wave of the compression wave is the high speed of each cylinder at the end of the intake stroke. The formula below l _S = (θ _S - θ _O ) x (60/360N) x (1/4) x a (here, θ _S is the high load The opening period of the high-load intake valve that opens and closes the high-load intake port, θ _O is the period from the opening of the high-load intake valve until the expansion wave substantially occurs, and in order to effectively perform supercharging. N is the engine rotation speed, and a is the pressure. An engine intake system characterized by being set according to the wave propagation velocity).