JPH021476Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an intake passage of an engine.

(Prior art) A mixture is ejected from a fuel supply means, such as a carburetor, and the intake passage for guiding the mixture to the engine is designed to promote atomization or improve torque by utilizing the intake inertia effect. It is preferable to make it as long as possible. For this reason, as shown in Japanese Utility Model Application Publication No. 57-54665, the shape of the intake pipe interposed between the carburetor and the intake port is changed so that the air-fuel mixture supplied from the carburetor is transferred to the intake port of the engine, that is, the intake pipe. There are some that are bent away from the mounting surface to the engine body.

However, when the intake pipe is made long in this way, it is disadvantageous from the viewpoint of quickly guiding the air-fuel mixture from the carburetor to the engine. Particularly in cold weather, the fuel from the carburetor hardly atomizes but becomes liquid and travels through the walls of the intake pipe, resulting in extremely delayed fuel supply and the problem of not being able to start the engine quickly. arise.

(Purpose of the invention) The present invention was made in consideration of the above-mentioned circumstances, and even when the intake pipe interposed between the fuel supply means and the intake port of the engine body is lengthened, To provide an engine intake passage that allows the engine to be started quickly in cold weather.

(Structure of the invention) In order to achieve the above-mentioned object, in the present invention, a bend is provided between the fuel supply means and the intake port formed in the engine body so that the fuel supply means is bent away from the intake port. An intake passage for an engine, comprising an intake pipe interposed therebetween and guiding fuel ejected from the fuel supply means to the engine, wherein a bypass passage is arranged to bypass the intake pipe. The bypass passage has an upstream end opened to the inner bottom wall of the intake pipe at a bent part of the intake pipe, and a downstream end of the bypass passage further downstream of the intake pipe than the upstream end of the bypass passage. The bypass passage is opened into the intake pipe at a side thereof, and the bypass passage has a path length that is longer than a path length of the intake pipe with respect to the intake pipe between the upper and downstream ends of the bypass passage. The bypass passage is short, and the minimum passage cross-sectional area of the bypass passage is set to be smaller than the minimum passage cross-sectional area of the intake pipe.

(Embodiment) In FIG. 1, 1 is an engine body, and in the embodiment, the engine body 1 has four cylinders: a first cylinder 2a, a second cylinder 2b, a third cylinder 2c, and a fourth cylinder 2d. It is said to be an inline 4 cylinder. In such an engine body 1 (cylinder head), there are 4
3 intake ports for the 1st cylinder, 3b for the 2nd cylinder, 3c for the 3rd cylinder, and 3d for the 4th cylinder.
A surface of each of the intake ports 3a to 3d that opens to the outside of the engine body 1 is an intake pipe mounting surface 4.

An intake manifold 5 serving as an intake pipe is attached to the intake pipe mounting surface 4. This intake manifold 5 has a chamber 6 directly below the carburetor directly below a flange portion 5a for connecting the carburetor, and the chamber 6 directly below the carburetor.
As shown in FIG. 2, the first branch part A is located in a direction away from the intake pipe mounting surface 4. Two first branch passages 5A and 5B are branched from this first branch part A, and one of the first branch passages 5
A is bent in the middle and extends toward the intake pipe mounting surface 4, and is further branched into two second branch passages 5A-1 and 5A-2 on the downstream side of this bend. ), the two second branch passages 5A-1, 5A-2
is connected to the intake port 3a or 3b. Similarly, the other first branch passage 5B is bent midway to face the intake pipe mounting surface 4, and is further branched into two second branch passages on the downstream side of the bend (this (the branch part is designated by the symbol C as another second branch part), and the two second branch passages 5B
-1 and 5B-2 are connected to the intake port 3c or 3d.

With the intake manifold shaped as described above, the air-fuel mixture from the carburetor 7 (see FIGS. 2 and 3) as a fuel supply means connected to the flange portion 5a is directed as indicated by the white arrow in FIG. As shown, from the chamber 6 immediately below, the first branch part A and the first branch passages 5A, 5
B, second branch parts B, C, second branch passage 5A-1,
5A-2, 5B-1, and 5B-2, and is supplied to each of the intake ports 3a to 3d. That is, the air-fuel mixture from the carburetor 7 once flows in a direction away from the intake pipe mounting surface 4, and then is bent and reversed to flow to each of the intake ports 3a to 3d. Therefore, from the carburetor 7 to the intake port 3
The intake passages from a to 3d are made sufficiently long to promote fuel atomization or sufficiently enhance the intake inertia effect. Moreover, since the carburetor 7 is located in the middle portion of the intake manifold 5 in the left-right direction in FIG. At the same time, the amount of protrusion of each member from the intake pipe mounting surface 4 is also reduced, making it easier to mount it on the vehicle body.

As shown in FIG. 3, the inner bottom wall 6a of the directly below chamber 6 and the second branch passage 5A-2 are connected by a bypass passage 8 having a small diameter (minimum passage cross-sectional area is small). That is, the upstream end 8 of the bypass passage 8
a is opened to the inner bottom wall 6a, while its downstream end 8b is opened to the inner bottom wall of the second branch passage 5A-2, and such a bypass passage 8 connects the immediately below chamber 6 and the intake port 3a. However, they are connected at a distance shorter than the path length of the intake manifold 5 which is a regular intake passage, and in the embodiment, they are connected at the shortest distance. The bypass passage 8 is formed to pass through the bridge part 5b, which connects the part of the chamber 6 directly below the intake manifold 5 and the second branch passage 5A-2. There is.

A solenoid valve 9 is connected to the bypass passage 8 near its downstream end 8b. This solenoid valve 9 is opened when it is energized, and a temperature switch 11 and a starting switch 12 are connected in series to each other in the middle of the connection to the battery 10. The temperature switch 11 is closed when the engine temperature is below a predetermined temperature, and the starter switch 12 is closed when the starter switch of an ignition switch (not shown) is turned on and the starter motor is rotated. It is also closed during so-called cranking. That is, the solenoid valve 9
is designed to open only in cold weather and when the engine is started.

In addition, 13 in Figures 1 and 2 is the EGR passage, 1
Reference numeral 4 denotes an EGR valve, and the downstream end of the EGR passage 13 is opened into the first branch A from the upper wall thereof. Exhaust gas flowing through such an EGR passage 13 is indicated by a black arrow in FIG.

In the above configuration, at cold start,
Since both switches 11 and 12 are closed, the solenoid valve 9 is opened. At this time, the air-fuel mixture, particularly liquid fuel, from the carburetor 7 tends to stay on the inner bottom wall 6a of the chamber 6 directly below, but it passes from the inner bottom wall 6a through the bypass passage 8 that constitutes the shortest intake passage. , is immediately supplied to the intake port 3b, that is, the second cylinder 2b. In addition, in this case, since the passage diameter of the bypass passage 8 is small, even if the intake negative pressure is low at the time of starting, the liquid fuel will flow at a sufficiently high speed based on the intake negative pressure. This also contributes to the prompt supply of liquid fuel. Therefore, immediately after starting the
The number cylinder 2b is ignited (completely exploded). Due to the ignition of this No. 2 cylinder 2b, the engine speed increases and the suction force (intake negative pressure) of the other cylinders 2a, 2c, and 2d also increases, which causes the air-fuel mixture that is not sufficiently atomized to increase. The fuel is immediately supplied to each cylinder 2a, 2c, and 2d through the normal route (the route through the intake manifold 5 without passing through the bypass passage 8), and in this way, all the cylinders 2a to 2d are ignited.

Of course, if the above-mentioned starting operation is stopped, the starting switch 12 is opened, so the solenoid valve 9 is closed, and the bypass passage 8 is not used after that, and all the air-fuel mixture passes through the intake manifold 5 to each intake port 3a.
~3d. Of course, once the engine is warmed up, the temperature switch 11 is also opened.

Further, in the above configuration, since the length of the bypass passage 8 is shortened and the diameter of the passage is made small, the intake manifold 5 does not become larger.

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases.

The bypass passage 8 may be always open without providing a separate on-off valve (electromagnetic valve 9).
In this case, the bypass passage 8 may be made sufficiently small in diameter so as not to obstruct the flow of intake air in the intake manifold 5. In addition, the bypass passage 8
When the diameter is made sufficiently small, it is preferable to provide a head difference between the upstream end 8a and the downstream end 8b to compensate for the flow of fuel.

By providing two or more bypass passages 8, for example,
In the embodiment, the directly below chamber 6 and the second branch passage 5B-1 may be further connected by a bypass passage.

One carburetor may be provided for one intake port, and in this case, the intake manifold 5 is not required (each intake port and each carburetor each independently form one intake port). connected by pipes). Of course, the present invention can be similarly applied to engines having other numbers of cylinders than four cylinders.

(Effects of the invention) As is clear from the above, the invention has the following effects:
The length of the intake pipe that connects the fuel supply means and the intake port of the engine body can be made sufficiently long to promote fuel atomization or sufficiently increase the intake inertia effect. By using the bypass passage with a small passage cross-sectional area, fuel can be quickly supplied to the intake port (cylinder) and the engine can be started quickly.

Moreover, in this case, the minimum passage cross-sectional area of the bypass passage is made smaller than the minimum passage cross-sectional area of the intake pipe,
In addition, since the length of the bypass passage is shorter than the length of the intake pipe, the device does not become larger.

Furthermore, in order to obtain the above effects, it is sufficient to simply provide the bypass passage in the intake pipe, so the structure is simple and can be implemented easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the present invention. FIG. 2 is a sectional view taken along the line -- in FIG. 1. FIG. 3 is a sectional view taken along the line -- in FIG. 1. 1: Engine body, 3a to 3d: Intake port,
5: Intake manifold (intake pipe), 6a: Inner bottom wall (of the intake pipe), 7: Carburetor, 8: Bypass passage, 8
a: upstream end, 8b: downstream end.

Claims (1)

[Claims for Utility Model Registration] The fuel supply means is interposed between the fuel supply means and an intake port formed in the engine body by being bent so as to move away from the fuel supply means and the intake port. An intake passage for an engine comprising an intake pipe that guides fuel ejected from the intake pipe to the engine, wherein a bypass passage is arranged to bypass the intake pipe, and the bypass passage is arranged to bypass the intake pipe. The upstream end of the bypass passage is opened to the inner bottom wall of the intake pipe at a bent part of the intake pipe, and the downstream end of the bypass passage is opened into the intake pipe downstream of the upstream end of the bypass passage. , the bypass passage has a path length shorter than that of the intake pipe with respect to the intake pipe between the upper and downstream ends of the bypass passage, and a minimum passage disconnection of the bypass passage. An intake passage for an engine, characterized in that the area is set to be smaller than the minimum passage cross-sectional area of the intake pipe.