JPS633398Y2 - - 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 the cylinders are communicated through each balance tube 1 of the intake manifold 2, since the phase difference of the pressure fluctuation of each cylinder is different, 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.

Although it is not a down draft variable bench lily type multiple carburetor, there is also one in which each branch port 3 of the intake manifold connected to a side draft carburetor is communicated with a balance tube 4 as shown in Fig. 3. However, when all the branch ports 3 are connected in this way, the effect of suppressing pulsation is large, but as shown in Fig. 4, the torque curve α when they are connected (torque Curve β) had a problem in that the torque and output decreased by about 5% or more.

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 rapid blowout of fuel is caused by a hole that is different from a normal fuel supply port, that is, a hole with a function other than the fuel supply port, for example, a hole with a function other than the float chamber 45 of the carburetor to keep the pressure constant. This phenomenon occurs because fuel blows out into the intake passage through the vent 44 that communicates with the atmosphere. 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 uses a balance tube structure to attenuate intake pulsation and maintain flow balance between the carburetors in a variable bench lily type multiple carburetor, while also completely eliminating the risk of sudden fuel blowout in high load ranges. The purpose is to remove it.

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 connected to the intake air connected to each carburetor. The manifold communicates with each other at two locations: the branch port and the riser portion.

In an intake manifold with such a structure, the pressure in the intake manifolds connected to each carburetor is transmitted through the balance tube, canceling out the peak of pressure fluctuation, and the pulsation of the intake air flows through all the intake ports to the balance tube. It is suppressed as well as if it were communicated with.

In addition, since both the branch port and the riser part are communicated through a balance tube, the necessary cross-sectional area of the balance tube necessary to suppress pulsation can be distributed to each balance tube, and the riser part is communicated with each other. The passage cross-sectional area of the balance tube can be reduced. Therefore, an imbalance in the flow rates between the vaporizers caused by a large amount of mixed gas flowing into the balance tube communicating with the riser portion is suppressed. Note that the balance tube that communicates the branch ports has the following configuration: only one of the branch ports served by each carburetor communicates with each other, and the intake air flowing through the branch ports has this configuration. Since it does not inherently allow a large amount of intake air to flow because it is difficult to flow into the balance tube, it is difficult to create an imbalance in the flow rate between the converters. Therefore, the flow rate flowing through the carburetor is balanced, increasing the amount of intake air, making the mixture distribution uniform, and improving engine output. Furthermore, more importantly, by communicating not only the branch port but also the riser portion through the balance tube, the phenomenon of fuel blowing out from the vent etc. does not occur. Therefore, overconcentration of the air-fuel mixture in the high load range is prevented, and normal operation can be achieved.

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 one embodiment of the present invention. The figure shows an example of the intake manifold of a four-cylinder engine equipped with a downdraft variable bench lily type twin carburetor. In the figure, 21 indicates the entire intake manifold, and 22 and 23 indicate the constituent parts of the intake manifold connected to the respective carburetors 24 and 25 of the dual carburetor. The intake manifolds 22 and 23 have the same shape, and have riser portions 26 and 27 located directly below the downdraft variable bench lily type carburetors 24 and 25 to change the flow from the carburetors 24 and 25 at right angles to the engine side. and a gathering part 2 extending almost horizontally from the riser parts 26 and 27 toward the engine side.
8, 29, branching parts 30, 31 that branch the flow of the collecting parts 28, 29 into respective cylinders, and branching part 3.
The branch ports 32, 33, 34, and 35 extend downstream from 0 and 31 toward each cylinder independently of each other. The branch ports 32, 33, 34, 35 of the intake manifold 21 are connected to the cylinder head 36.
are connected to the respective intake ports 37 formed in the cylinder #1, #2 cylinder,
Connected to #3 cylinder and #4 cylinder.

Branch ports 32, 33 of the intake manifold 21,
Of the ports 34 and 35, the branch ports 32 and 33 are in charge of most of the intake air and fuel supply by the carburetor 24, and the branch ports 34 and 35 are in charge of most of the intake air and fuel supply by the carburetor 25. 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 formed of an integral cast body.

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 ventilate type carburetors, and although the structure itself is known, the ventilate part 39 is composed of a carburetor body and a suction piston 41. The opening area of the vent lily is determined by the balance with the suction spring 42 by guiding the vent lily negative pressure to the suction chamber constituted by the case 40. The amount of fuel is controlled by a needle 43 fixed to the suction piston 41 in accordance with the amount of intake air. Note that 44 is a vent for communicating the float chamber 45 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 from the viewpoint of suppressing pulsation.
In order to suppress the flow rate flowing from 2, 23 into the other intake manifold 23, 22, it is small to some extent.
In particular, it is better for the passage cross-sectional area of the balance tube 47 to be small. Therefore, the sum of the passage cross-sectional area of the balance tube 46 and the passage cross-sectional area of the balance tube 47 is set to be approximately equal to or less than the passage cross-sectional area of any one of the branch ports 32, 33, 34, and 35. Since this required passage cross-sectional area is distributed between the balance tube 46 and the balance tube 47, the passage cross-section area of the balance tube 47 that communicates the riser parts 26 and 27 communicates only the riser parts as shown in FIG. It is much smaller than the passage cross-sectional area of the balance tube 1, and is set to about 1/2 or less of the balance tube.

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

First, the intake air passes through the variable bench lily section 39 and the throttle valve 38, and then enters the intake manifolds 22, 2.
3, the flow direction is changed toward the engine at the riser parts 26 and 27 of the intake manifolds 22 and 23,
The flow passes through the collecting parts 28 and 29 to the branch parts 30 and 31, where the flow is divided into each cylinder, and passes through the branch ports 32, 33, 34, and 35 to the #1 cylinder and #2 cylinder, respectively. , #3 cylinder, and #4 cylinder. 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 intake ports can communicate with each other, effectively suppressing pulsation. Here, the pulsations in the branch ports 32, 35 connected to the #1 and #4 cylinders are also instantly and effectively eliminated via the branch ports 33, 34 and balance tubes 46, 47 connected to the #2 and #3 cylinders. They interfere and are suppressed. Therefore, the pulsation transmitted to the variable bench lily portion 39 is suppressed, the flapping of the suction piston 41 that 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 almost symmetrical to each other, so branch port 3
The flow rates of the air-fuel mixture flowing through 2 and 33 tend to be approximately equal. Also, for the same reason, branch ports 34 and 3
The flow rate of the air-fuel mixture flowing through 5 tends to be approximately equal. By communicating this through balance tubes 46, 47, branch ports 32, 33, 34, 3
Therefore, the flow balance between the vaporizers 24 and 25 is about 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 4 to the branch port 34 of the other carburetor 25, the direction of the flow must be changed at the entrance to the balance tube 46, but the flow in the branch ports 33 and 34 is 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. Since it flows into the intake manifold on the other side of the carburetor, it tries to flow through the balance tube 47, but as mentioned above, the passage cross-sectional area of the balance tube 47 is small, so the flow resistance is large, and the balance tube actually flows into the intake manifold on the side of the other carburetor. The amount flowing through 47 to the intake manifold on the other carburetor side is small.

Comparing this with the previous example shown in Fig. 1, in the device shown in Fig. 1, the balance tube 1 is provided in the riser section, and the passage cross-sectional area of the balance tube 1 is large. The intake air that changes its flow in all lateral directions when it collides easily flows into the balance tube 1 and can easily flow into the intake manifold on the other carburetor side through the balance tube 1 with low flow resistance. The balance of inflow between vaporizers is likely to be lost. On the other hand, as in the embodiment of the present invention, the branch port 33,
34 is provided with a balance tube 46, which communicates the riser parts 26 and 27.
When the cross-sectional area of the passage is reduced, intake air is less likely to flow into the intake manifolds of other cylinders, and the balance of each carburetor is less likely to be upset. 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 and the intake flow rate of each carburetor 24, 25 of an engine equipped with an intake manifold according to an 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 14, 15 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. 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 to the vent other than the regular fuel supply port. However, as in the embodiment of the present invention, the riser parts 26 and 27 are also connected to the balance tube 4.
As a result of testing under various conditions in a high load region, it was found that when communication was established at No. 7, the above-mentioned abnormal fuel blowout did not occur 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.
It has also been found that if this phenomenon does not occur, it will not occur again. 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 or the like, but since the cross-sectional area of the passage is smaller than that of the one shown in FIG. 1, it does not cause an imbalance in the flow rate.

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 Since they are connected through another balance tube, the present invention can simultaneously reduce pulsation during idling and suppress flow imbalance when the throttle valve is fully open. The effect is that the output can be improved, and the possibility of abnormal fuel blowout can be completely eliminated.

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 intake 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 the 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 an intake manifold according to an embodiment of the present invention, FIG. 7 is a sectional view of the intake manifold shown in FIG. 6 and its vicinity, and FIG. 8 is a diagram of an engine intake system with the intake manifold shown in FIG. FIG. 3 is a characteristic diagram of engine rotation speed and intake flow rate of each carburetor. 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...variable bench lily portion, 41...branch portion, 44...Vent, 46...Balance tube, 47...Another balance tube.

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. An intake manifold characterized in that ports communicate with each other through a balance tube, and riser portions of the intake manifold connected to each carburetor communicate with each other through another 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. 2. The intake manifold according to claim 1, wherein the riser portion of the intake manifold connected to each carburetor is communicated with another balance tube.