JPH0452373B2 - - 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) Generally, a multi-cylinder engine is provided with an intake passage having two systems, a low-load intake passage and a high-load intake passage, which open independently to each cylinder, and the intake passage has at least a low-load intake passage. It has a primary valve that changes the amount of intake air flowing through the intake passage for normal use, and a secondary valve that changes the amount of intake air that flows through the intake passage for high loads.When the engine is under low load, only the primary valve is opened. By supplying intake air to each cylinder only from the low-load intake passage, which has a narrow passage area, it increases the intake flow rate and improves combustion stability.At the same time, when the engine is under high load, the secondary valve is also opened. A so-called dual-induction type intake system is well known, in which intake air is supplied from a high-load intake passage as well, thereby increasing filling efficiency and increasing output.

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 equipped with a supercharger, 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, it is possible to obtain suitable charging efficiency over a wide range of engine speeds by utilizing 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 engine speed. 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, when examining the intake characteristics of the engine, the present inventors found that (i) When the intake port is opened, the intake air is compressed by the pressure of the residual exhaust gas in the combustion chamber, and a compression wave is generated at the intake port part in the intake passage. This compression wave is generated particularly strongly when the intake port is closed because the engine exhaust pressure has been increased in recent commercial vehicles to reduce noise and purify exhaust gas. (ii) When the intake port is closed, We found that the inertia of the intake air compresses the intake air, generating compression waves in the intake port portion of the intake passage, and (iii) that the start of intake at the intake port generates expansion waves in the intake passage.

Therefore, in a multi-cylinder engine equipped with two independent intake passages as described above, the present invention is capable of converting the compression wave (i) in one cylinder upon opening into other cylinders, in particular, causing intake air to blow back. If the supercharging effect is applied at the end of the intake stroke, the supercharging effect can be effectively obtained (hereinafter referred to as the exhaust interference effect). If activated, a supercharging effect can be effectively obtained (hereinafter referred to as intake inertia effect), and the expansion wave in (iii) above in each cylinder is reversed into a compression wave, which is also applied at the end of the intake stroke of each cylinder. Focusing on the fact that the supercharging effect can be effectively obtained if the supercharging effect is activated (hereinafter referred to as the intake individual pulsation effect), we have focused on the above-mentioned inter-cylinder interference effect (exhaust interference effect and intake inertia effect) and the intake individual pulsation of each cylinder. By utilizing this effect, it is intended to improve engine filling efficiency.

That is, an object of the present invention is to provide an intake system for a multi-cylinder engine having two intake passages as described above.
During high-load, high-speed engines that require high output, the opening compression wave that occurs particularly strongly at the intake port of one cylinder as described above in at least one intake system is effectively propagated to other cylinders at the end of the intake stroke, resulting in inter-cylinder interference. In addition to setting it to effectively obtain a supercharging effect by using the exhaust interference effect as By making it possible to obtain the supercharging effect due to the above-mentioned intake air pulsation effect, it is possible to operate the engine at high loads and high speeds with a simple configuration by making slight design changes to the existing intake system without using a supercharger etc. This aims to effectively improve output by increasing filling efficiency.

(Means for Solving the Problem) In order to achieve this object, the solving means of the present invention has a low-load intake passage and a high-load intake passage independent of each other for each cylinder, and a low-load intake passage for each cylinder. An intake passage is provided in which a load intake passage and a high load intake passage are opened to the combustion chamber of each cylinder via an intake port, and the intake passage changes at least the amount of intake air flowing through the low load intake passage. The present invention is based on an engine intake system having a primary valve and a secondary valve that changes the amount of intake air flowing through the high-load intake passage. and a communication passage having a passage cross-sectional area equal to or greater than the minimum passage cross-sectional area of each intake passage, which communicates the low-load intake passages and the high-load intake passages of each cylinder downstream of the primary valve and the secondary valve. Provide an expansion room with a The passage length of the low-load intake passage and the high-load intake passage between each cylinder via the above-mentioned communication passage is set to 5000 to 5000 for at least one of them.
When the engine rotates at a high speed of 7,000 rpm, the compression wave generated when the intake port of one cylinder opens will propagate to the intake ports of other cylinders at the end of the intake stroke to perform supercharging. In addition, the passage lengths l _P and l _S of the low load intake passage and the high load intake passage from the enlarged chamber to the intake port of each cylinder are both 5000~
When the engine rotates at a high speed of 7000 rpm, the expansion wave generated by the start of intake at the intake port of each cylinder is reversed and reflected in the expansion chamber, and the secondary pulsating wave of the compression wave propagates to the intake port of each cylinder at the end of the intake stroke. The following formula l _P = (θ _P - θ ₂ ) x (60/360N) x (1/4) x a l _S = (θ _S - θ ₂ ) x (60/360N) ) × (1/4) × a (where θ _P and θ _S are the opening periods of each intake port, and θ ₂ is the period from the opening of each intake port until the expansion wave is substantially generated) N is the engine rotational speed, a is the propagation velocity of the pressure wave).

(Function) As a result, in the present invention, the 5000
At high engine speeds of ~7000rpm, the opening operation of the secondary valve opens both the low-load intake passage and the high-load intake passage. Intake air is supplied independently of the At this time, in at least one of the low-load and high-load intake systems, when the intake port of one cylinder is opened, the opening compression wave generated near the intake port passes through the communication path and is generated at the end of the intake stroke. It is propagated to the intake ports of other cylinders.
As a result, this opening compression wave forces intake air into the combustion chamber from the intake ports of other cylinders at the end of the intake stroke, resulting in supercharging (exhaust interference effect).

At the same time, in both the low-load and high-load intake passages of each cylinder, expansion waves generated in the low-load and high-load intake passages due to the start of intake from the low-load and high-load intake ports, A secondary arterial wave of the compression wave that is reversed and reflected in the expansion chamber is propagated to each intake port at the end of the intake stroke of each cylinder, and supercharging is also performed (intake-specific pulsation effect).

In that case, each of the communication passages is located downstream of the primary valve and the secondary valve, respectively, and the passage cross-sectional area of each communication passage is set to be greater than or equal to the minimum passage cross-sectional area of each intake passage. Although there is pressure wave attenuation due to the expansion of the passage cross-sectional area of each communication passage itself, the attenuation rate is lower than the pressure wave attenuation due to the reduction of the passage cross-sectional area (throttling). Therefore, the above-mentioned exhaust interference effect can be effectively exhibited. Furthermore, since the enlarged chamber is located downstream of the primary valve and the secondary valve, it can similarly effectively exert the unique intake pulsation effect.

Here, 5000 ~
The limit of 7000 rpm is generally set in this range for maximum output and maximum speed, so it is a high load, high rotation area of the engine that requires high output, and is an effective area for improving charging efficiency and output. It depends.

Furthermore, the reason why the low-load intake passage and the high-load intake passage are made independent downstream of the primary and secondary valves is that the pressure waves generated in the low-load and high-load intake passages of each cylinder are This is to prevent the intake passage from dispersing to the other or from weakening due to interference with each other.In particular, due to the difference in requirements between the low-load intake passage and the high-load intake passage in a dual induction intake system, the intake port This is because the opening/closing timing and length are different, and one pressure wave is attenuated by the other.

(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 is partitioned downstream of the air flow meter 7 by a partition 8 into a main low-load intake passage 9 and a main high-load intake passage 10. The main low-load intake passage 9 has a primary valve that opens as the engine load increases, and when the load exceeds a predetermined load, opens fully to change the amount of intake air flowing through the main low-load intake passage 9 when the engine load is low. A valve 11 is provided. In addition, in the main high-load intake passage 10,
A secondary valve 12 is provided that opens when the engine load exceeds a predetermined load and changes the amount of intake air flowing through the main high-load intake passage 10 when the engine is under high load. Further, the main low-load intake passage 9 is branched downstream of the primary valve 11 into first and second low-load intake passages 9a and 9b having the same shape and dimensions, and then connected to low-load intake ports 13 and 13, respectively. Through each cylinder 1
It communicates with the combustion chambers 2, 2 of A and 1B. Also,
The main high-load intake passage 10 is branched into first and second high-load intake passages 10a and 10b having the same shape and dimensions downstream of the secondary valve 12, and then connected through high-load intake ports 14 and 14, respectively. Each cylinder 1A, 1
It communicates with the combustion chambers 2, 2 of B. Therefore, for each cylinder 1A, 1B, low load intake passage 9a,
9b and the high-load intake passages 10a and 10b are configured to open into the combustion chamber 2 independently at the downstream of the primary valve 11 and the secondary valve 12.

The minimum passage cross-sectional area A _S of each of the above-mentioned high-load intake passages 10a, 10b is the respective low-load intake passage 9a, 9b.
The minimum passage cross-sectional area A _P is set larger than the minimum passage cross-sectional area A P (A _S > A _P ), and the high-load intake passages 10a and 10b
This makes it possible to effectively propagate pressure waves by reducing their attenuation.

Further, at the downstream end of each of the low-load intake passages 9a and 9b (of course located downstream of the communication passage 18 described later), a fuel injection amount is determined according to the intake air amount based on the output of the air flow meter 7. Controlled electromagnetic valve type fuel injection nozzles 15, 15 are provided to ensure good fuel response.

The branch part of the main high-load intake passage 10 is located downstream of the secondary valve 12, and is an enlarged chamber having a communication passage 16 that communicates the first and second high-load intake passages 10a and 10b. 17. The passage cross-sectional area A _CS of the communication passage 16 is:
The minimum passage cross-sectional area of each high-load intake passage 10a, 10b is set to be larger than the minimum passage cross-sectional area A _S (A _CS ≧
A _S ).

Further, the branch part of the main low-load intake passage 9 is
It is located downstream of the primary valve 11 and is constituted by an enlarged chamber 19 having a communication passage 18 that communicates the first and second low-load intake passages 9a and 9b. The passage cross-sectional area A _CP of the communication passage 18 is the minimum passage cross-sectional area of each low-load intake passage 9a, 9b so as to similarly transmit pressure waves with reduced attenuation.
It is set larger than A _P (A _CP > A _P ).

Further, the volume of each of the enlarged chambers 17 and 19 is set to be 0.5 to 2.0 times the engine displacement. This is because if it is less than 0.5 times, no reversal effect between expansion waves and compression waves can be obtained, whereas if it exceeds 2.0 times, the pressure waves will be diffused and the inter-cylinder interference effect will be significantly reduced. Further, each of the enlarged chambers 17 and 19 functions as a surge tank for intake air during transient operation such as acceleration or deceleration of the engine, thereby ensuring good fuel response.

That is, downstream of the primary valve 11 and secondary valve 12, there is a low-load intake passage 9a for each cylinder 1A, 1B.
and 9b and high-load intake passages 10a and 10b, respectively, are provided with enlarged chambers 19 and 17 having large volumes (the above-mentioned predetermined volumes).
When the next valve 11 and the secondary valve 12 are at a low opening, the expansion chamber 19
Intake negative pressure is generated and stored in the enlarged chamber 17 in which both the valve 17 and the secondary valve 12 or only the secondary valve 12 has a low opening. In addition, when the primary valve 11 and the secondary valve 12 are at a high opening, intake air close to atmospheric pressure is supplied to both the expansion chambers 19 and 17, or when only the primary valve 12 is at a high opening, the expansion chamber 19 is filled with air near atmospheric pressure. Pressure is generated and stored. Therefore, during acceleration operation, the above-mentioned valve (at least one of the primary valve 11 and the secondary valve 12)
When the valve opening rapidly increases and the valve opens, the negative intake pressure that had been stored in the expansion chamber (at least one of the expansion chambers 19 and 17) rapidly increases the intake flow velocity in the intake passage upstream of the expansion chamber. , air flow meter 7
By increasing the responsiveness of the engine, a rapid fuel increase (fuel responsiveness) can be ensured. In addition, during deceleration operation, when the opening of the valve suddenly decreases and the valve closes, the intake flow velocity in the intake passage upstream of the expansion chamber is reduced by the intake pressure close to atmospheric pressure that had been stored in the expansion chamber until then. By quickly reducing the amount of fuel and increasing the responsiveness of the air flow meter 7, a rapid fuel loss (fuel responsiveness) can be ensured.

Furthermore, each of the high-load intake ports 14 is provided with a high-load intake valve 20 that opens and closes the high-load intake port 14, and although not shown, each of the low-load intake ports 13 is provided with a high-load intake valve 20 for opening and closing the high-load intake port 14. Intake port 1
A low-load intake valve that opens and closes 3 is provided.
In each cylinder 1A, 1B, one end of 21 and 22 opens to the atmosphere, and the other end opens to the exhaust port 2.
3, 24 to open into the combustion chamber 2 of each cylinder 1A, 1B to discharge exhaust gas from the combustion chamber 2.
and a second exhaust passage, each of the above exhaust ports 2
3 and 24 are provided with exhaust valves 25 and 25 that open and close the exhaust ports 23 and 24, respectively. Although not shown, a catalyst device for purifying exhaust gas is installed at the downstream collecting portion of each exhaust passage 21, 21, 22, 22 of each cylinder 1A, 1B, and the exhaust pressure is high. It's summery.

Furthermore, the opening timing of the high-load intake valve 20 (the opening timing of the high-load intake port 14) is the opening timing of the low-load intake valve (not shown) (the opening timing of the low-load intake port 13). It was set earlier than
A strong compression wave is generated in the high-load intake passages 10a and 10b when they are opened. Also,
Both valve closing timings are set at approximately the same time.

In addition, both cylinders 1 via the communication passage 16
Passage length L _S of high load intake passages 10a and 10b between A and 1B (that is, high load intake ports 14 and 1
4) is the passage length of the communication passage 16 l _CS
and the respective passage lengths l _S and l S of the first and second high-load intake passages 10a and 10b downstream of the communication passage 16 ( _{L S =} l _CS +2l _S ). Furthermore, the passage length L _P of the low-load intake passages 9a and 9b between the cylinders 1A and 1B via the communication passage 18 (that is, the communication length between the low-load intake ports 13 and 13) is the same. is the sum of the passage length l _CP of the communication passage 18 and the passage lengths l P and l _P of the first and second low-load intake passages 9a and 9b downstream of the communication passage 18 ( _{L P =} l _CP + 2l _P )
It is. The above passage lengths L _S and L _P are as follows:
When obtaining exhaust interference effect in both cylinders 1A and 1B in the rotation range of 5000 to 7000 rpm, L _S (P) = {(720/Z) + θ _S (P) −θ _O }×(60/360N)× a...Set to the value determined from the formula (). In addition, in the above formula (), Z is the number of cylinders and Z=2,
720/Z indicates the phase difference between cylinders. θ _S (P) is the opening period of each intake valve. In addition, θ _O is the period from the opening of each intake valve (opening of the intake port) until the compression wave at the time of opening is substantially generated, and the period during which the compression wave at the time of opening is propagated in order to effectively perform supercharging. The invalid period is the sum of the period from the time just before each intake valve closes (intake port closes) until the valve closes, and varies depending on the valve opening characteristics, etc., but is about 10 to 50 degrees. Yotsute {(720/Z)+
θ _S (P)−θ _O } represents the rotation angle of the crankshaft required from generation of an opening compression wave in one cylinder to propagation to the other cylinder at the end of the intake stroke.
Also, N is the engine rotation speed, N = 5000 to 7000 rpm, and 60/360N is the time (seconds) required to rotate 1°.
represents. Also, a is the propagation speed of the pressure wave, which is 20℃
So a=343m/s.

In addition, each of the above passage lengths L _S and L _P are 5000~
When obtaining the intake inertia effect between both cylinders 1A and 1B in the rotation range of 7000 rpm, the formula L _S (P) = {(720/Z) - θ ₁ } × (60/360N) × a ... () is set to the value calculated from. In the above equation (), θ ₁ is the period from the closing of each intake valve (intake port closing) until the compression wave at closing is substantially generated, and the compression wave at closing to perform effective supercharging. The invalid period, which is the sum of the period from just before closing to the closing of each intake valve during which the waves are propagated, is also about 10 to 50 degrees, and {(720/Z) − θ ₁ } is the same for one cylinder. It represents the rotation angle of the crankshaft required from the generation of the compression wave at closing to the propagation to the other cylinder at the end of the intake stroke. The rest is the same as in the case of formula () above.

For example, in the case of the above embodiment, the length of the passage is set so as to obtain an exhaust interference effect with a large supercharging effect between the high-load intake passages 10a and 10b, which have a large passage area and can effectively propagate pressure waves. L _S is set to the value determined by the above equation (). Further, in order to obtain an intake inertia effect between the low-load intake passages 9a and 9b, the passage length L _P is set to a value determined by the above equation ().

Furthermore, each of the high-load intake passages 10a, 10
Passage length l _S and each low load intake passage 9a, 9
The passage length l _P of b, that is, the enlarged chamber 1 of each intake passage
The passage lengths l _S and l _P from the opening end face to the combustion chamber 2 (each intake port 13, 14) are both due to the second-order intake individual pulsation effect in the rotation range of 5000 to 7000 rpm. _{In order to} obtain . In the above equation (), _θ2 is the period from the opening of each intake port due to the opening of each intake valve until the expansion wave is substantially generated, and the period when the expansion wave is reversed in order to effectively perform supercharging. The ineffective period, which is the sum of the period from just before the intake valve closes (intake port closes) until the valve closes, during which the secondary pulsating wave of the compression wave is propagated, is about 60 to 100 degrees, and therefore (θ _S (P)-θ ₂ ) represents the rotation angle of the crankshaft required from the generation of the expansion wave to the propagation of the secondary pulsating wave of the compression wave. Moreover, 1/4 represents the reciprocal of the stroke in which the secondary pulsation makes two reciprocations. The rest is the same as in the case of formula () above.

Here, the reason why secondary pulsation is used to obtain the intake-specific pulsation effect is that while primary pulsation has the above-mentioned effect, the passage lengths l _S and l _P become too long.
Since the length is twice as long as that in the case of secondary pulsation, it is not easy to install on a vehicle and tends to increase intake resistance. On the other hand, in the case of tertiary pulsation, the path lengths l _S and l _P become 2/3 shorter than those of secondary pulsation, but on the other hand, the above-mentioned effect decreases by about 15 to 25% with respect to secondary pulsation. Also, the intake resistance does not change much. For this reason, the purpose is to effectively exhibit the intake-specific pulsation effect while making the passage lengths l _S and l _P as short as possible.

Note that in the above equations () to (), 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 length of the intake passage.

Next, the operation of the first embodiment will be explained with reference to FIG. 3.
When the engine is running at high speed, the secondary valve 12 is opened to open the main high-load intake passage 10 as well as the main low-load intake passage 9, and the main high-load intake passage 10 is opened for each cylinder 1A, 1B.
Intake air is supplied from each high-load intake passage 10a, 10b independently from each low-load intake passage 9a, 9b. At that time, when the high-load intake port 14 of one cylinder, for example, the high-load intake valve 20 of the second cylinder 1B is opened, the second high-load intake passage 1 is opened.
The opening compression wave generated near the high-load intake port 14 of 0b increases the passage length L _S of the high-load intake passages 10a and 10b between both cylinders 1A and 1B by 5000~
By setting the value determined by the above formula () based on the engine high speed of 7000 rpm, the second high-load intake passage 10b → communication passage 16 →
After passing through the first high-load intake passage 10a, the high-load intake port 14 of the first cylinder 1A at the end of the intake stroke
is propagated to. As a result, this opening compression wave forces the intake air into the combustion chamber 2 from the high-load intake port 14 of the first cylinder 1A at the end of the intake stroke, resulting in supercharging (exhaust interference effect). .

At the same time, when the low-load intake port 13 is closed due to the closing of the low-load intake valve at the end of the intake stroke of the second cylinder 1B, a closing occurs near the low-load intake port 13 of the second low-load intake passage 9b. The compression wave is generated by setting the passage length L _P of the low-load intake passages 9a and 9b between both cylinders 1A and 1B to a value determined by the above formula () with reference to the high engine speed of 5000 to 7000 rpm. , through the second low-load intake passage 9b → the communication passage 18 → the first low-load intake passage 9a, and is propagated to the low-load intake port 13 of the first cylinder 1A, which is also at the end of the intake stroke, and supercharging is carried out. (inhalation inertia effect). Furthermore, at the same time, in the first cylinder 1A, after the low-load intake valve and the high-load intake valve 20 are opened, intake is started from the low-load and high-load intake ports 13 and 14, and the first low-load and high-load intake valves are opened. Load intake passages 9a, 10
The expansion waves generated in a respectively increase the passage lengths l _P and l _S of each intake passage 9a and 10a from 5000 to 5000.
By setting the value determined by the above formula () based on the engine high speed of 7000 rpm, each intake passage 9a, 10a → each expansion chamber 17, 1
9 (reflected as a compression wave) → each intake passage 9a,
10a → Combustion chamber 2 (reflects as an expansion wave and reflects) → Each intake passage 9a, 10a → Each expansion chamber 17, 19 (reflects as a compression wave and reflects) → Each intake passage 9a, 10a
As a secondary pulsating wave of the compression wave, the first cylinder 1
The supercharging is also propagated to each intake port 13, 14 at the end of the intake stroke of A (intake individual pulsation effect).

Similarly, in the second cylinder 1B, 5000
At high engine speed of ~7000rpm, the first cylinder 1A is applied to each intake port 13 and 14 at the end of the intake stroke.
The closing compression wave and the opening compression wave from the cylinder 1B and the secondary pulsating compression wave of the second cylinder 1B itself are propagated to perform supercharging.

Therefore, the supercharging effect due to the inter-cylinder interference effect between the cylinders 1A and 1B (the exhaust interference effect in the high-load intake system and the intake inertia effect in the low-load intake system), and the , 1B itself has a synergistic effect with the supercharging effect due to the unique intake pulsation effect in the low-load and high-load intake systems, as shown in Figure 4. The charging efficiency is significantly increased in the rotation range of In addition, in FIG. 4, compared to the case where each intake passage 9a, 9b, 10a, 10b of each cylinder 1A, 1B is made independent and only the intake individual pulsation effect is obtained based on 6000 rpm (indicated by a broken line), In addition to this
The output torque characteristics of the engine are shown when the inter-cylinder interference effect (exhaust interference effect and intake inertia effect) is obtained based on 6000 rpm (indicated by a solid line).

In that case, the high-load intake passages 10a, 10b, which are pressure wave propagation paths for obtaining the exhaust interference effect and the intake-specific pulsation effect, have a larger passage cross-sectional area than the low-load intake passages 9a, 9b. As a result, the resistance to the propagation of pressure waves is small, and the exhaust interference effect, which has a particularly large supercharging effect, can be effectively exerted in a high-load intake system.

Further, the communication passages 16 and 18 are located downstream of the primary valve 11 and the secondary valve 12, respectively, and the passage cross-sectional areas A _CP and A _CS of the communication passages 16 and 18 are the same as those of the intake passages 9a, 9b, and 18, respectively. Since the minimum passage cross-sectional area of valves 10a and 10b is set to be at least A _P and A _S , each of the above-mentioned valves 11 and 1
2, the pressure waves are not attenuated by the communication passages 16 and 18, and although there is pressure wave attenuation due to the expansion of the passage cross-sectional area of each communication passage 16, 18 itself, compared to the pressure wave attenuation due to the passage cross-sectional area reduction (throttle). The attenuation rate is small, so the exhaust interference effect and intake inertia effect described above can be effectively exerted. In addition, each of the expansion chambers 17, 1
Since the valve 9 is located downstream of the primary valve 11 and the secondary valve 12, it can similarly effectively exhibit the intake-specific pulsation effect.

Furthermore, by opening the high-load intake port 14 earlier than the low-load intake port 13, a strong compression wave can be generated especially when the high-load intake port 14 opens, resulting in an exhaust interference effect. This is more effective due to improved supercharging effect.

Also, a fuel injection nozzle 1 as a fuel supply device
5 is a low-load intake passage 9a downstream of the communication passage 18;
9b is provided at the downstream end (near the opening to the combustion chamber 2), the length of the intake passage becomes longer, so that the air flow meter 7 disposed upstream of the communication passage 18 (enlarged chamber 19) Good fuel response is achieved by preventing the deterioration of fuel response caused by response delays during acceleration and deceleration operations (response delay in fuel supply corresponding to the changed amount of air introduced into the combustion chamber 2). In addition, it is possible to simplify the fuel supply system by installing only the low-load intake passages 9a and 9b, which can supply intake air and fuel in all operating ranges.

In addition, the supercharging effect due to the exhaust interference effect, intake inertia effect, and intake unique pulsation effect is achieved by the communication passage 16,
18, and both cylinders 1A, 1B via the communication passages 16, 18.
This can be obtained by setting the lengths L _S and L _P of the high-load intake passages 10a, 10b and the low-load intake passages 9a, 9b between them as described above, and does not require a supercharger or the like. Therefore, only a slight design change to the existing intake system is 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 above-mentioned embodiments, but also includes various other modifications. For example, in the above embodiment, in each cylinder 1A, 1B, the low load and high load intake passages 9a, 9
b, 10a, 10b are connected to the combustion chamber 2 through independent low-load and high-load intake ports 13, 14, respectively.
However, as in the second embodiment shown in FIG. The above first
The same effects as in the embodiment can be achieved (in FIG. 5, the same parts as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted).

Further, although the first embodiment described above shows an example in which the present invention is applied to a two-cylinder four-stroke engine, it goes without saying that the present invention can also be applied to various other multi-cylinder engines of the dual induction type. For example, as an example, FIG. 6 shows a third embodiment applied to a four-valve, four-cylinder, four-cycle engine (the same parts as in the first embodiment are denoted by the same reference numerals and detailed explanations are given below). (Explanation omitted).

In the case of this example, the high-load intake passages 10a to 10d of the cylinders 1A to 1D are branched from the same portion of the enlarged chamber 17' downstream of the secondary valve 12.
They are communicated by a communication path 16' formed by 7'. In addition, the low-load intake passages 9a to 9d of each cylinder 1A to 1D are connected to an enlarged chamber 1 downstream of the primary valve 11.
They are communicated by a communication passage 18' that branches from the same portion of the enlarged chamber 19'. First,
The low-load intake passages 9a, 9b, 9c, and 9d of the second, third, and fourth cylinders 1A, 1B, 1C, and 1D are all set to the same length. 1A, 1B, 1C, 1D high load intake passage 1
0a, 10b, 10c, and 10d are also all set to the same length, and L _S and L _P between adjacent cylinders in the 1-3-4-2 ignition order are necessarily equal. Further, the cylinders 1A to 1A are connected via the communication passages 16' and 18'.
In order to obtain the exhaust interference effect, at least one of the passage lengths L _S and L _P of the high load intake passages 10a to 10d and the low load intake passages 9a to 9d between 1D should be The term (rotation angle required from generation of compression wave to propagation during opening) is different (see Figure 9), L _S (P) = (θ _S (P) - 180 - θ _O ) × (60/360N) × a ...(') is set. Further, when obtaining the intake inertia effect, Z=4 is set according to the above equation (). In addition, each intake passage 9a to 9d, 10a to 10d
The passage lengths l _P and l _S are both set according to the above equation ( ) so as to obtain a second-order intake-specific pulsation effect. Furthermore, for 3-cylinder 4-stroke engines,
Although not shown, it is the same as in the case of two cylinders, and each passage length L _S , L _P , l _P , l _S may be set using the above equations () to ().

Furthermore, as a mode of inter-cylinder interference of the exhaust interference effect and the intake inertia effect, the first embodiment (two cylinders, four
cycle engine), the high-load intake system has an exhaust interference effect, and the low-load intake system has an intake inertia effect. You can set it to . In the case of a general two-cylinder engine, the working process is as shown in Fig. 7.
As described above, the exhaust interference effect (indicated by the solid line arrow) and the intake inertia effect (indicated by the dashed line arrow) act alternately from the first cylinder to the second cylinder and from the second cylinder to the first cylinder. It is. In addition, in the case of a three-cylinder engine, as shown in Fig. 8, both of the above effects can be achieved from the first cylinder to the second cylinder, as in the case of a two-cylinder engine.
It acts sequentially from the 2nd cylinder to the 3rd cylinder, and from the 3rd cylinder to the 1st cylinder. Furthermore, in the case of a four-cylinder engine, as shown in Figure 9, the intake inertia effect is caused by the firing order: 1st cylinder → 3rd cylinder, 3rd cylinder → 4th cylinder, 4th cylinder → 2nd cylinder. , the exhaust interference effect acts sequentially from the 2nd cylinder to the 1st cylinder, and conversely, the exhaust interference effect acts from the cylinder whose phase is delayed by 180 degrees, from the 3rd cylinder to the 1st cylinder, and from the 4th cylinder to the 3rd cylinder. , from the second cylinder to the fourth cylinder, from the first cylinder to the second cylinder, and from the third cylinder to the first cylinder. Therefore, at least one of the passage lengths L _{S and LP} between the cylinders, which cause inter-cylinder interference in this way, may be set so as to obtain the exhaust interference effect.

Further, in the above embodiment, the primary valve 11 is provided in the main low-load intake passage 9, but the primary valve 11 is provided in the main low-load intake passage 9 and the main high-load intake passage 9. A type provided in the main intake passage 5 upstream of the branching part with the intake passage 10 can also be adopted.

(Effects of the Invention) As explained above, according to the present invention, in a multi-cylinder engine equipped with two independent intake passages for low load and high load, when the engine rotates at a high speed of 5000 to 7000 rpm, At least one of the high-load and low-load intake systems provides a strong supercharging effect due to the exhaust interference effect between cylinders, and each cylinder's own high-load and low-load intake systems provide unique intake characteristics. Since the supercharging effect due to the pulsation effect is effectively obtained, even a simple configuration consisting of a slight design change to the existing intake system can be used without the need for a supercharger or the like, and it is possible to easily charge the engine during high load and high rotation speeds. It is possible to effectively improve output to improve efficiency, and is therefore useful for easily implementing measures to improve engine output and reducing costs.

[Brief explanation of the drawing]

The drawings show embodiments of the invention, FIGS. 1 and 2.
The figure is an explanatory diagram of the overall configuration and a schematic diagram of the main parts of the first embodiment, FIG. 3 is an explanatory diagram showing the intake stroke of the first embodiment, FIG. 4 is a diagram showing the output torque characteristics, and FIG. FIG. 6 is a schematic diagram of the main parts showing the second embodiment, FIG. 6 is a diagram equivalent to FIG. 1 showing the third embodiment, and FIGS. 7 to 9 are inter-cylinder interference in 2-cylinder, 3-cylinder, and 4-cylinder engines, respectively. FIG. 1A to 1D...1st to 4th cylinders, 2...Combustion chamber, 5
... Main intake passage, 7... Air flow meter, 9... Main low load intake passage, 9a to 9d... 1st to 4th low load intake passage, 10... Main high load intake passage, 10a
~10d...first to fourth high-load intake passages, 11...
Primary valve, 12... Secondary valve, 15... Fuel injection nozzle,
16, 16'...Communication path, 17, 17'...Enlargement chamber, 1
8, 18'...Communication path, 19, 19'...Enlargement chamber.

Claims (1)

[Scope of Claims] 1. Each cylinder has an independent low-load intake passage and a high-load intake passage, and the low-load intake passage and high-load intake passage of each cylinder are connected to the combustion chamber of each cylinder. The chamber is provided with an intake passage opened through an intake port, and the intake passage includes at least a primary valve that changes the amount of intake air flowing through the low-load intake passage, and a primary valve that changes the amount of intake air that flows through the high-load intake passage. An intake system for an engine having a secondary valve that is changed, wherein the low-load intake passages and the high-load intake passages of each of the cylinders are connected downstream of the primary valve and the secondary valve, respectively. An enlarged chamber having a communication passage with a passage cross-sectional area larger than the minimum passage cross-sectional area of the passage is provided, and the passage length of the low-load intake passage and the high-load intake passage between each cylinder via the communication passage is at least When the engine is running at a high speed of 5,000 to 7,000 rpm, the compression wave generated when the intake port of one cylinder opens propagates to the intake port of the other cylinder at the end of the intake stroke to perform supercharging. The passage lengths l _P and l _S of the above-mentioned low-load intake passage and high-load intake passage from the expansion chamber to the intake port of each cylinder are determined when both are at high engine speed of 5000 to 7000 rpm. The following equation _l = (θ _P −θ ₂ ) × (60/360N) × (1/4) × a l _S = (θ _S −θ ₂ ) × (60/360N) × (1/4) × a (Here, θ _P and θ _S are the opening periods of each intake port, and θ ₂ is the period from the opening of each intake port 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. (N is the engine rotational speed, and a is the propagation speed of pressure waves.) 2 In a 2-cylinder or 3-cylinder 4-cycle engine, the passage length L S of the high-load intake passage between each cylinder via the communication passage and the passage length L _S of the low-load intake passage between each cylinder via the communication passage. At least one of the passage lengths L _P can be calculated using the following formula L _S (P) = {(720/Z) + θ _S (P) −θ _O } x (60/360 N) x a (where Z is the number of cylinders, θ _S (P) is the opening period of each intake port, θ _O is the period from the opening of each intake port until the opening compression wave is substantially generated, and the opening period of the opening compression wave for effective supercharging. (N is the engine rotational speed, and a is the propagation speed of the pressure wave.) Intake system for the engine described. 3 In a 4-cylinder 4-cycle engine, the passage length L _S of the high-load intake passage between each cylinder via the communication passage and the passage length of the low-load intake passage between each cylinder via the communication passage. At least one of L _P ,
The following formula L _S (P) = (θ _S (P) - 180 - θ _O ) × (60/360N) × a (Here, θ _S (P) is the opening period of each intake port, θ _O
is the period from the opening of each intake port until the opening compression wave is substantially generated, and the period from just before closing of each intake port to the time when the opening compression wave is propagated in order to effectively perform supercharging. (N is the engine rotation speed, and a is the propagation speed of the pressure wave.)
Intake system for the engine described in Section 1.