JPS633400Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake manifold for a multi-cylinder internal combustion engine equipped with a variable bench lily type multiple carburetor.

In the intake manifold of a conventional multiple carburetor, although this is an example of a fixed bench lily, in order to prevent pulsation during idling, the part directly below the carburetor is equipped with a balance tube 1, as shown in Figure 1. There was a communication. That is, intake manifold 2
Inside the pump, the flow rate changes according to the timing of intake air, and the pressure changes accordingly, causing pulsation.
This pressure fluctuation is transmitted to the carburetor, so when a variable bench lily is used, the variable bench lily tends to flap due to the pulsation. This flapping is less likely to occur when the engine speed is high because the variable bench lily cannot follow pressure fluctuations, but when the engine is idling, the frequency of pressure fluctuations is small, so it tends to fluttering. In order to suppress this flapping, it is necessary to eliminate the pulsation.
When each of the intake manifolds 2 is communicated through the balance tube 1, the phase difference of the pressure fluctuation of each cylinder is different, so the pressures interfere with each other and act in a direction to eliminate the pulsation.

However, the balance tube 1 that communicates with the intake manifold connected to each carburetor of the multiple carburetor,
Although it is effective in suppressing pulsation, conventionally it was installed directly below the carburetor, so the intake air immediately after passing through the carburetor is connected from the intake manifold connected to one carburetor to the intake manifold connected to the other carburetor. There was a problem that it flowed into the manifold, causing an imbalance in the flow rate between the carburetors. In particular, when the throttle valve is fully open, as shown in Figure 2, an imbalance occurs in the intake air amounts A and B passing through the respective carburetors in the high speed range, resulting in a decrease in the intake air amount, resulting in a decrease in output, and a change in the air-fuel ratio to the output air. There was a problem in that the deviation from the fuel ratio caused a decrease in output.

As shown in Fig. 3, there is a system in which each branch port 3 of the intake manifold connected to a side draft type carburetor is communicated with a balance tube 4, but when all branch ports 3 are connected in this way, Although the effect of suppressing pulsation is large, as shown in Fig. 4, when the balance tube is connected (torque curve β), the torque and output are about 5% or more compared to the torque curve α when the balance tube is not connected. There was a problem with the decline.

As described above, conventional intake manifolds are incompatible with suppressing pulsation and maintaining output, and a solution has been desired.

In order to solve this object, the applicant of the present utility model registration proposed an intake manifold for a multi-cylinder engine connected to a variable bench lily type carburetor as shown in FIG. A plurality of branch ports 7, 8 and one branch port 8, 9 of the branch ports 9, 10 connected to
An intake manifold that communicates with each other through a balance tube 11 has been proposed before this utility model registration application.

With such a structure, pulsation is suppressed and the amount of intake air flowing through each carburetor 5, 6 is balanced. This suppresses the fluttering of the variable bench lily during idling, stabilizing performance, and maintains the intake air amount by balancing the intake air amount, maintains the output air-fuel ratio, and evenly distributes the air-fuel mixture between the cylinders. The effect is that the engine output is maintained well even in a high load range.

However, in the intake manifold shown in Figure 5, under certain conditions, such as high load and high rotation, fuel suddenly comes out of the carburetor, causing the air-fuel ratio to drop below 10, resulting in overconcentration. Through repeated testing, it was discovered that there was a problem with the mixture becoming mixed. This sudden blowout of fuel is caused by holes that are different from normal fuel supply ports, that is, holes with other functions that are not intended for fuel supply ports, such as connecting the float chamber and the atmosphere to maintain constant pressure in the float chamber of the carburetor. This phenomenon occurs because fuel blows out into the intake passage through the vent that communicates between the two. Moreover, tests have shown that this phenomenon occurs on and off, and either never occurs, or once it occurs under certain conditions, a large amount of fuel suddenly blows out. In other words, this phenomenon either occurs or it does not occur, and once it occurs, the amount of fuel blown does not gradually increase, but rather a large amount of fuel is blown into the intake passage, making the mixture too rich. Making it impossible to maintain normal operation.

In other words, in an intake manifold like the one shown in Fig. 5, although two things, which were conventionally thought to be contradictory, such as reducing pulsation and maintaining flow balance, can be achieved at the same time, mixing due to sudden fuel injection under certain conditions is possible. There was a problem that there was a risk of overconcentration of Qi.

This invention, in a variable bench lily type multiple carburetor, attenuates intake pulsation, maintains the flow balance between the carburetors, completely eliminates the risk of sudden fuel blowout in the high load range, and communicates through a balance tube. The purpose of this is to suppress the decrease in output as much as possible when this happens.

In order to achieve this purpose, in the intake manifold of a multi-cylinder engine connected to the variable bench lily type multiple carburetor of the present invention, one of the plurality of branch ports connected to each carburetor is The branch ports communicate with each other through a balance tube, and the riser portions of the intake manifolds connected to each carburetor communicate with each other through another balance tube. In other words, all the branch ports are not connected to each other, but only one of the branch ports assigned to each carburetor is communicated by the balance tube, and is not connected to each carburetor. The intake manifold communicates with each other at two locations: the branch port and the riser portion. The passage cross-sectional area of the balance tube that communicates with the branch port is made smaller than the passage cross-sectional area of the balance tube that communicates with the riser section. The cross-sectional area of the passage may be determined by increasing or decreasing the inner diameter of the tube, or by providing an orifice within the tube.

In an intake manifold with this structure,
Since the branch port section and the riser section are connected by a balance tube, the pressure is sufficiently transmitted between each vaporizer, and the peaks and troughs of pressure fluctuations cancel each other out, suppressing pulsation. . Also, 2
Because they are communicated at two locations, the cross-sectional area of each balance tube can be reduced, and compared to the intake manifold shown in Figure 1, the amount of intake air flowing from one side to the other through the balance tubes is reduced. Unbalance of flow rate is also suppressed. In addition, since the riser part is also communicated with the balance tube, the abnormal blowout of fuel stops decreasing.

Generally, when pulsation is eliminated by communication through a balance tube, the output decreases as explained in Fig. 4, but in this invention, the passage cross-sectional area of the balance tube on the branch port side, which is particularly effective in reducing pulsation, is reduced by riser. Since the cross-sectional area of the passage is smaller than that of the balance tube on the branch port side, the drop in pulsation at the branch port part is suppressed to a relatively small level, and a drop in output is prevented. Therefore, the effects of preventing pulsation, suppressing flow imbalance, and preventing abnormal fuel blowout are achieved while suppressing a decrease in output.

Hereinafter, preferred embodiments of the intake manifold of the present invention will be described with reference to the drawings.

6 and 7 show an intake manifold according to a first embodiment of the present invention. The figures show an intake manifold for a four-cylinder engine equipped with a downdraft variable venturi type dual carburetor as an example. In the figures, 21 indicates the entire intake manifold, and 22 and 23 indicate components of the intake manifold connected to the respective carburetors 24 and 25 of the dual carburetor. The intake manifolds 22 and 23
are symmetrical to each other, and are located directly below the downdraft type variable venturi type carburetors 24, 25 to redirect the flow from the carburetors 24, 25 to the engine side at a right angle, and
The intake manifold 11 is made up of collecting sections 28, 29 which extend almost horizontally from the intake manifold 11 toward the engine side, branching sections 30, 31 which branch the flows of the collecting sections 28, 29 to the respective cylinders, and branching ports 32, 33, 34, 35 which extend downstream from the branching sections 30, 31 toward the respective cylinders independently of one another.
6, and are connected to the first, second, third and fourth cylinders via intake valves.

Branch ports 32, 33 of the intake manifold 21,
Among the branch ports 34 and 35, the carburetor 24 takes in most of the intake air and fuel supply to the branch ports 34 and 35, and the carburetor 25 takes in most of the intake air and fuel to the branch ports 34 and 35. be in charge. The branch ports 32 and 33 are separated from the branch part 30 and widen to separate from each other as they go downstream, and then curve in a direction toward the engine and extend parallel to each other.
It communicates with an intake port 37 of the cylinder head 36. Similarly, the branch ports 34 and 35 are separated from the branch part 31 and widen to separate from each other as they go downstream, and then curve toward the engine side and extend parallel to each other, and are connected to the intake port of the cylinder head 36. It connects to 37. Branch port 32,
The portions 33, 34, and 35 and the portions forming the riser portions 26 and 27 are integrally cast.

Above the riser parts 26 and 27, there is a carburetor 24,
There are 25 respective throttle valves 38.
The carburetors 24 and 25 are variable bench lily type carburetors, and the structure itself is known, but the negative pressure generated in the bench lily portion 39 is
The suction spring 42 is guided to a suction chamber 48 consisting of the inner wall of the
The position of the suction piston 41, that is, the opening area of the bench lily portion 39 is determined by the balance. A needle 43 is fixed to the suction piston 41, and the amount of fuel is controlled by the radius of the needle. In addition, 4
4 is a vent for communicating the float chamber 45 of the variable bench lily vaporizer with the atmosphere to keep the pressure of the float chamber 45 constant.

Intake manifold 21 connected to a dual carburetor
Among them, any one branch port among the plurality of branch ports connected to each of the vaporizers 24 and 25, that is, the branch port 3 connected to the vaporizer 24.
One of the branch ports 2 and 33 (branch port 33 connected to the #2 cylinder in the illustrated example),
Any one of the branch ports 34 and 35 connected to the carburetor 25 (in the illustrated example, the branch port 34 connected to the #3 cylinder) is communicated with each other through a balance tube 46. . The balance tube 46 is provided between the side walls of the branch ports 33 and 34 and extends linearly in the horizontal direction.
The balance tube 46 connects each vaporizer 24, 2
5, that is, branch ports 32 and 33 connected to the vaporizer 24 and the vaporizer 25
Of the branch ports 34, 35 connected to each other, only one branch port 33, 34 is communicated with each other, and not all the branch ports 32, 33, 34, 35 are communicated with each other.

Further, the intake manifolds 22 and 23 connected to the respective carburetors 24 and 25 are connected to the respective riser parts 2.
6 and 27 are also communicated through another balance tube 47. The other balance tube 47 extends horizontally through the side walls of the riser parts 26 and 27. Therefore, the intake manifolds 22 and 23 are communicated with each other by a balance tube 47 at a portion directly below the carburetors 24 and 25, and by a balance tube 46 at a portion remote from the portion directly below the carburetors 24 and 25 toward the engine. .

The sum of the passage cross-sectional area of the balance tube 46 and the passage cross-section area of the balance tube 47 should be larger in terms of suppressing pulsation and preventing fuel from blowing out. In order to suppress the flow rate flowing into the branch ports 32, 33, 34, 3, the smaller the smaller the better.
The cross-sectional area of any one of the passages is set to be less than or equal to the cross-sectional area of any one of the passages. Then, this required passage cross-sectional area is distributed to the balance tube 46 and the balance tube 47. The passage cross-sectional area of the balance tube 46 that communicates the branch ports 33 and 34 is the riser portion 2.
It is smaller than the passage cross-sectional area of the balance tube 47 which communicates the two. In the first embodiment, the size of the passage side area is determined by the balance tubes 46, 4.
This is achieved by making a difference in the inner diameter of the 7.

Next, the operation of the intake manifold of the first embodiment configured as described above will be explained.

First, the intake air passes through the bench lily section 39 and the throttle valve 38, reaches the intake manifolds 22 and 23, and then reaches the riser section 2 of the intake manifolds 22 and 23.
At 6 and 27, the direction of the flow is changed toward the engine, and it passes through converging parts 28 and 29 and reaches branch parts 30 and 31. At the branch parts 30 and 31, the flow is divided into each cylinder, and the flow is transferred to branch ports 32, 33, and 34. , 35 to the #1 cylinder, #2 cylinder, #3 cylinder, and #4 cylinder, respectively. At this time, #1 cylinder, #2 cylinder,
In the #3 cylinder and the #4 cylinder, intake pressure fluctuations, that is, pulsations having mutually different phases occur in accordance with the intake timing.

This pulsation is transmitted through the balance tube 46 and the balance tube 47 to the respective carburetors 24,
Pressure fluctuations that can be transmitted between the intake manifolds 22 and 23 connected to the intake manifold 25 and have different phases are
Since the peaks and valleys of pressure fluctuations overlap and cancel each other out, pulsation is suppressed. Pressure fluctuations are transmitted through balance tube 46 and balance tube 4.
7, and if there is a communication path through which even pressure waves can be transmitted, the air can be transmitted instantaneously without accompanying the actual flow in the intake balance tubes 46, 47. Since it can be used, #2 cylinder,
#3 cylinder branch ports 33, 34 and riser section 2
6, 27 and balance tube 4 respectively
6. If you communicate with the balance tube 47,
All the intake ports 21 can communicate with each other, and pulsation can be effectively suppressed. Here, the pulsations in the branch ports 32 and 35 connected to the #1 and #4 cylinders are also detected in the #2 cylinder,
Through the branch ports 33, 34 and balance tubes 46, 47 connected to the #3 cylinder, they effectively interfere with each other and are suppressed. Therefore, the pulsation transmitted to the bench lily portion 39 is suppressed, and the flapping of the suction piston 41 of the bench lily portion 39, which tends to occur during idling, is suppressed, and good performance is maintained.

On the other hand, from the perspective of flow balance, #1
cylinder, branch ports 32, 33 connected to #2 cylinder
are symmetrical to each other, so the branch ports 32,
The flow rate of the air-fuel mixture flowing through 33 tends to be approximately equal. Furthermore, for the same reason, the flow rates of the air-fuel mixture flowing through the branch ports 34 and 35 tend to be approximately equal.
By communicating this through balance tubes 46, 47, branch ports 32, 33, 34, 35
Therefore, the flow balance between the vaporizers 24 and 25 tends to collapse.

However, regarding the balance tube 46 that communicates the branch ports 33 and 34, the large intake flow when the throttle valve 38 is fully open tends to continue flowing in the flow direction within the branch ports 33 and 34. , and does not attempt to flow into the balance tube 46. That is, one carburetor 2 passes through the balance tube 46.
In order for the flow to flow from the branch port 33 of the second carburetor 25 to the branch port 34 of the other carburetor 25, the direction of the flow must be changed by inputting to the balance tube 46, but the flows in the branch ports 33 and 34 are already directional. Therefore, it is difficult for the water to flow into the balance tube 46.

Regarding the other balance tube 47, that is, the balance tube 47 that communicates with the riser parts 26 and 27, the intake air that has changed its flow direction by hitting the bottom wall surfaces of the riser parts 26 and 27 also flows into the balance tube 47. Because it flows in, it tries to flow through the balance tube 47 into the intake manifold on the other carburetor side, but the balance tube 47
The passage cross-sectional area of is smaller than the passage cross-sectional area of balance tube 1 when two intake manifolds are communicated only by the riser part as shown in FIG.
The flow resistance is large, and the amount that actually flows through the balance tube 47 to the intake manifold on the other side of the carburetor is much smaller than in the intake manifold as shown in FIG. Therefore, the imbalance in flow rates between the vaporizers, which has been a problem in the past, is suppressed.

FIG. 8 shows the relationship between the engine speed of the engine intake system to which the intake manifold is attached and the flow rate of each carburetor 24, 25 in the embodiment of the present invention.
As can be seen from a comparison between the same figure and FIG. 2, in the present invention, an unbalance in the flow rate is unlikely to occur up to a high load rotation range, and even if an unbalance occurs, it is small.

When the flow rates flowing through the branch ports 32, 33, 34, and 35 are stably balanced, the amount of air taken into the cylinders becomes large, and therefore the engine output becomes high. In addition, since the intake air flow rate flowing through each carburetor 24, 25 is stabilized, the air-fuel ratio can be easily maintained at the output air-fuel ratio, preventing a decrease in output, and suppressing excessive richness and leanness of the air-fuel mixture. This is also advantageous in terms of exhaust gas control.

Note that the branch ports 33 and 34 are communicated through the balance tube 46, and the balance tube 4
Even if the riser portions 26 and 27 are communicated through 7, the decrease in output can be suppressed compared to the case where all the branch ports are communicated as in the example shown in FIG. Moreover, branch port 3, which has a particular effect on output reduction,
Since the passage area of the balance tube 46 that communicates between the balance tubes 3 and 34 is smaller than the passage cross-sectional area of the balance tube 47, the suppression of pulsation at the branch port portion is relatively small, and the decrease in output is small. The torque curve γ of the present invention is shown in FIG. 4, and the torque curve γ is close to the torque curve α when the branch port is not communicated.

Next, regarding the effect of preventing fuel from blowing out, in the already proposed intake manifold shown in Fig. 5, under certain conditions in the high load range as mentioned above, fuel suddenly flows out from vents other than the regular fuel ports. However, when the riser parts 26 and 27 were also connected through the balance tube 47 as in the embodiment of the present invention, as a result of testing under various conditions in a high load region, the above-mentioned fuel abnormality was detected. It turned out that no bubbles occurred at all. As mentioned above, this phenomenon is an on-off phenomenon, and it either occurs or it does not occur, and it is not a matter of magnitude, but it has also been found that if it does not occur, it will not occur at all. Therefore, an abnormal drop in the air-fuel ratio (A/F) due to abnormal fuel blowout and an accompanying failure to continue normal operation will not occur. In this way, the balance tube 47 functions to prevent abnormal fuel from blowing out from the vent 44, etc., but since the passage cross-sectional area is smaller than that of the one in FIG. 1, it does not cause an imbalance in the flow rate. .

FIG. 9 shows an intake manifold according to a second embodiment of the present invention. In this embodiment, orifices 48 and 49 are provided in the balance tubes 46 and 47, respectively, to determine the size of the passage cross-sectional area of the balance tube 46 that communicates the branch port with the balance tube 47 that communicates the riser part. This is achieved by making the opening area of the orifice 48 in the balance tube 46 smaller than the opening area of the orifice 49 in the balance tube 47 that communicates with the riser section. Other configurations,
Since the operation is similar to that of the first embodiment, similar parts are given the same reference numerals as those of the first embodiment, and the explanation thereof will be omitted.

As is clear from the above description, in the intake manifold of the present invention, one branch port of the intake manifold that receives each carburetor is communicated with each other through a balance tube, and the riser portion of each intake manifold is connected to They communicate through another balance tube, and the cross-sectional area of the balance tube on the branch port side is smaller than the cross-sectional area of the riser side, so when using the present invention,
While keeping the output drop due to balance tube communication small, it is possible to simultaneously reduce pulsation during idling and suppress flow imbalance when the throttle valve is fully open. It is possible to improve the output of the engine,
Moreover, the effect of completely eliminating the possibility of abnormal fuel blowout can be obtained.

In the above explanation, an intake manifold connected to a downdraft carburetor is taken as an example, but it may also be an intake manifold connected to a side draft carburetor, and the intake manifold is limited to a 4-cylinder air manifold. It may be a 6-cylinder intake manifold in which three branch ports are connected to each carburetor of a dual carburetor, or it may be a multiple carburetor other than a dual carburetor. Included in the technical idea of this invention.

[Brief explanation of the drawing]

Figure 1 is a plan view of an intake manifold with a balance tube for a fixed bench lily type multiple carburetor as a prior art, and Figure 2 is an engine rotational speed in the intake manifold with balance tube for a multiple carburetor shown in Figure 1. Characteristic diagram of intake flow rate of each vaporizer, 3rd
The figure is a cross-sectional view when all intake ports are connected through balance tubes, Figure 4 is a characteristic diagram of engine speed and torque showing a comparison between when a balance tube is installed and when it is not installed, and Figure 5 is a characteristic diagram of engine speed and torque. Plan view of the intake manifold of the type previously proposed by the applicant in which intake ports are connected through a balance tube, No. 6
The figure is a plan view of the intake manifold according to the first embodiment of the present invention, FIG. 7 is a sectional view of the intake manifold of FIG. 6 and its vicinity, and FIG. 8 is an engine intake system with the intake manifold of FIG. 6 installed. FIG. 9 is a characteristic diagram of the engine speed and the intake flow rate of each carburetor, and FIG. 9 is a plan view showing a part of the intake manifold in cross section according to the second embodiment of the present invention. 21... Intake manifold (whole), 22, 23
...Intake manifold (part) connected to each carburetor, 24, 25... Carburizer, 26, 27... Riser section, 28, 29... Collection section, 30, 31...
Branch portion, 32, 33, 34, 35... Branch port, 36... Cylinder head, 37... Intake port of cylinder head, 38... Throttle valve, 39... Bench lily portion, 41... Suction piston, 44...Vent, 46...Balance tube, 47...Another balance tube, 48, 49...Orifice.

Claims (1)

[Claims for Utility Model Registration] (1) In the intake manifold of a multi-cylinder engine connected to variable bench lily type multiple carburetors, any one branch out of the plurality of branch ports connected to each carburetor. The ports communicate with each other through a balance tube, and the riser portion of the intake manifold connected to each carburetor is communicated with another balance tube, and the passage cross-sectional area of the balance tube that communicates with the branch port is defined as above. An intake manifold characterized in that the passage cross-sectional area of the balance tube communicating with the riser portion is smaller than that of the balance tube. (2) In the intake manifold for a 4-cylinder engine connected to a downdraft variable bench lily type dual carburetor, the branch port connected to the #2 cylinder and the branch port connected to the #3 cylinder are connected to each other with a balance tube. In addition, the riser portion of the intake manifold connected to each carburetor is communicated with another balance tube, and the cross-sectional area of the balance tube communicating with the branch port is the same as that of the balance tube communicating with the riser portion. The intake manifold according to claim 1, which is smaller than the passage cross-sectional area.