JPH028125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for an exhaust turbocharged engine mainly used in automobile engines.

As is well known, a cylinder combustion chamber equipped with both main and sub intake systems has been put into practical use as one of the engine improvement measures to reduce exhaust gas. In addition to the main intake valve that takes in air, there is also a sub-intake valve that takes in air-fuel mixture from the intake port upstream of the throttle valve of the carburetor. It works in conjunction with the subchamber and jet piece to enhance the jet effect within the combustion chamber.

By the way, when an exhaust turbo supercharger is inserted in the mixture passage downstream of the carburetor of this type of improved engine to supercharge the engine, there is a problem that it has an undesirable effect on the operation of the auxiliary intake system. The reason for this is that the suction force of the cylinder fluctuates greatly depending on the operating condition of the engine, so the discharge pressure of the mixture discharged from the supercharger changes from a negative pressure value to a positive pressure value. This is due to fluctuations over a wide range, and the specific effect is that in the supercharged operating range of the engine, part of the supercharged mixture and accumulated combustion gas enter the carburetor from the sub-intake passage. The backflow reduces the combustibility of the air-fuel mixture, and if the intake of the auxiliary intake system is temporarily stopped to prevent backflow, the auxiliary intake valve will not be cooled, causing local overheating of the combustion chamber. This causes problems such as unnecessary deterioration of the valve.

The present invention has been made to solve these problems, and the purpose of the present invention is to achieve a good air-fuel mixture and a good jet action in the combustion chamber over a wide operating range of the engine. An object of the present invention is to provide an intake system for a supercharged engine that can be obtained.

The present invention will be described below based on three illustrated embodiments.

First embodiment device (see FIG. 1).

The structure of this device is such that a combustion chamber 3 of a cylinder head 2 facing above a piston 1 is provided with a main suction port 4 and a sub suction port 5. An intake valve 6 and a sub-intake valve 7 are interposed.

Thus, the main intake port 4 communicates with the main intake passage 10A forming the discharge side of the supercharger 9, which is interposed in the mixture passage downstream of the carburetor 8, and the sub-intake port 5 communicates with the The throttle valve 11 communicates with an auxiliary intake passage 12A that opens to the intake port 8b of the intake passage 8a on the upstream side, and a check valve 13 for preventing backflow that opens only in the downstream direction is interposed in the passage 12A. ing.

Note that reference numeral 14 indicates an air cleaner communicating with the carburetor 8, and reference numeral 15 indicates an exhaust port of the cylinder head 2.

In the intake system of the first embodiment configured as described above, in an operating range where the suction negative pressure is strong such as during idling operation or low load operation, the main intake passage 10A is
Since the discharge pressure is maintained at a certain negative pressure value, the check valve 13 is opened and a good jet flow is generated within the combustion chamber 3.

On the other hand, in a supercharging operation range such as during high-load running, the discharge pressure of the main intake passage 10A becomes positive, so the check valve 13 closes and the intake port 8b
Backflow of intake air, etc. from the combustion chamber 3 to the carburetor 8 is prevented, thereby maintaining normal combustion operation within the combustion chamber 3.

Second embodiment device (see FIG. 2).

The structure of this device is that a bypass passage 16A is formed between the auxiliary intake passage 12B and the main intake passage 10B, and a check valve 17 as a first backflow prevention means is interposed in the bypass passage 16A. On the other hand, the sub-intake passage 12 upstream from the bypass branch point
B includes a check valve 18 as a second backflow prevention means.
is interposed.

Therefore, the first check valve 17 is connected to the main intake passage 1
The discharge pressure of 0B is set to a predetermined negative pressure value (e.g. -50mm
Hg) in the operating condition, the auxiliary intake passage 1
2B direction, while the second check valve 18
The cylinder head is provided with a characteristic that the cylinder head opens in two directions in an operating state when the discharge pressure is lower than the predetermined value.

In the intake system of the second embodiment configured as described above, in an operating range where the suction negative pressure is strong such that the discharge pressure is lower than a predetermined negative pressure value, the check valve 17 is closed and the check valve 18 is opened. Therefore, the jet effect of the auxiliary intake valve 7 maintains good combustion operation, similar to the operation in the first embodiment.

On the other hand, in the supercharging operation range where the discharge pressure exceeds the predetermined negative pressure value, the check valve 18 is closed and the check valve 17 is open, so the carburetor In addition to preventing backflow to the sub-intake passage 12B from the bypass passage 16A, the cooled air-fuel mixture flowing into the sub-intake passage 12B flows through the sub-intake valve 7, thereby preventing unnecessary overheating and deterioration of the valve 7. Ru.

Third embodiment device (see FIGS. 3 and 4).

The structure of this device is such that the passage opening operation of the double check valves 17 and 18 in the second embodiment is performed by the operation of one negative pressure responsive switching valve 19. Intake passage 12C, 12D
and a bypass passage 16 communicating with the main intake passage 10C.
The switching valve 19 installed at the branch point with B includes a diaphragm 21 that separates the negative pressure chamber 20, a balance spring 22 that pushes up the diaphragm 21, and a sliding valve body 23 attached to the diaphragm 21. , a high-pressure operation-side opening valve passage 25 and a low-pressure operation-side opening valve passage 26 that are opened and closed by vertical sliding of the valve body 23, and a ventilation passage that communicates the high-pressure operation-side opening valve passage 25 and the negative pressure chamber 20. 27 and an external communication valve passage 28, where the communication valve passage 28 is connected to the downstream sub-intake passage 1.
2D, and the opening valve passages 25 and 26 on the high-pressure operation side and the low-pressure operation side are respectively connected to the bypass passage 16B and the upstream sub-intake passage 12C.

In the intake system of the third embodiment configured as described above, in an operating range where the suction negative pressure is strong, the auxiliary intake passages 12C and 12D communicate with each other, and the bypass passage 16B is closed. In the supercharging operation region, the downstream auxiliary intake passage 12D and the bypass passage 16B are in communication, and the upstream auxiliary intake passage 12C is closed, and such passage opening/closing operation is different from the operation in the second embodiment described above. It has exactly the same effect.

Therefore, the intake operation of this embodiment is the same as that of the second embodiment.

As described in detail above, according to the supercharged engine intake device according to the invention set forth in claim 1 of the present invention, the auxiliary intake passage is configured to communicate or shut off depending on the operating state of the engine. Because of that,
In the operating range where the suction negative pressure is high, the sub-intake valve exerts a jet flow effect, and in the supercharging operating range, it can prevent intake air from flowing back into the carburetor.

Further, according to the intake device according to the invention described in claims 2 to 4, the auxiliary intake passage can be selectively connected to the carburetor intake passage upstream of the slot or the supercharging mixture, depending on the operating state of the engine. Since it is configured to communicate with the main intake passage through which air flows,
In the operating range where suction negative pressure is high, the auxiliary intake valve exerts a jet flow effect, and in the supercharging operating range, intake air backflow to the carburetor is prevented, and at the same time, heating of the auxiliary intake valve is also prevented. Effective engine combustibility is maintained throughout the operating range, and there are effects such as improving the durability of the intake valve.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an intake system for a supercharged engine showing a first embodiment of the present invention, FIG. 2 is a schematic diagram of the same intake system showing a second embodiment, and FIG. 3
FIG. 4 is a schematic diagram of the intake system showing an embodiment of the invention.
FIG. 4 is a sectional view of the negative pressure responsive switching valve of FIG. 3; 3... Combustion chamber, 4... Main intake port, 5... Sub-intake port, 8... Carburetor, 8a... Carburetor intake passage, 8b... Opening intake port, 9... Supercharger,
10A-10C...Main intake passage, 11...Throttle valve, 12A-12D...Sub-intake passage, 13...
...Check valve as a backflow prevention valve, 16A, 16B...
...Bypass passage, 17, 18...First and second check valves as backflow prevention means, 19...Negative pressure response switching valve, 25, 26...Each opening valve passage on the high pressure operation side and the low pressure operation side .

Claims (1)

[Claims] 1. A main intake port and a sub-intake port are opened in the combustion chamber, and the main intake port is connected to the discharge side of an exhaust turbo supercharger installed in a mixture passage downstream of a carburetor. In the intake system, the sub-intake port is communicated with the main intake passage forming the main intake passage, and the sub-intake port is communicated with the sub-intake passage which communicates with the intake passage of the intake passage upstream of the carburetor throttle valve. An intake system for a supercharged engine, characterized in that it is equipped with a check valve that closes in a supercharged operation range. 2 A main intake port and a sub-intake port are opened in the combustion chamber, and the main intake port is connected to the main intake passage forming the discharge side of the exhaust turbo supercharger installed in the mixture passage downstream of the carburetor. In the intake device in which the sub-intake port is communicated with the sub-intake passage leading to the intake port of the intake passage upstream of the carburetor throttle valve, a bypass passage is provided between the sub-intake passage and the main intake passage. At the same time, the bypass passage is provided with a first backflow prevention means that opens in an engine operating range where the supercharger discharge pressure exceeds a predetermined negative pressure value, and The sub-intake passage has a second intake passage that opens in the engine operating range when the supercharger discharge pressure falls below a predetermined negative pressure value.
An intake system for a supercharged engine, characterized in that it is equipped with a backflow prevention means. 3. The intake system for a supercharged engine according to claim 2, wherein each of the first and second backflow prevention means is formed by a check valve. 4 A negative pressure response switching valve for backflow prevention driven by the supercharger discharge pressure is installed at the branch point in the middle of the auxiliary intake passage, and the high pressure operation side opening valve passage of the switching valve and the low pressure operation side opening passage of the switching valve are interposed. 3. The intake system for a supercharged engine according to claim 2, wherein each of the side opening valve passages is connected to the bypass passage and a sub-intake passage upstream of the branching point.