JPH0116325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a supercharged engine in which a normal intake system path and a supercharging system path having a supercharger are independently provided.

As a prior art related to this type of engine, as shown in Japanese Patent Application Laid-Open No. 55-137315, an intake air supply that supplies air-fuel mixture to each cylinder by utilizing the negative pressure inside the cylinders generated as the piston descends. A system path and a supercharging system path for forcibly supplying air pressurized by a turbocharger into each cylinder are provided independently, and first, the intake valve provided at the end of the intake system path is opened. The air-fuel mixture is introduced into the cylinder from the intake system, and from around the time when the intake valve closes, a supercharging valve provided at the end of the supercharging system is opened to pressurize the cylinder from the supercharging system. There are some that are filled with air.

However, in this configuration, in order to prevent the air-fuel mixture in the cylinder from blowing back into the intake system during supercharging, the opening timing of the intake valve and the opening timing of the supercharging valve must be greatly overlapped. It needs to be set small. Moreover, in order to prevent the air-fuel mixture filled in the cylinder from flowing back into the supercharging path when moving to the compression stroke, the supercharging valve must be opened at a relatively early point, for example, at around 75 degrees after bottom dead center. Must be closed. Therefore, in order to satisfy these conditions without significantly reducing the amount of air-fuel mixture supplied from the intake system, the opening timing of the supercharging valve must be made very short, and the supercharging Limited by valve lift amount. As a result, we have found that using a high-compression, large-capacity supercharger, a sufficient supercharging effect cannot be achieved unless a large amount of air is forced into the cylinder through a narrow valve opening passage during the short period when the supercharging valve is open. As will be shown, such a tendency is contrary to the original purpose of this type of supercharging system. However, this type of supercharging system is characterized in that it is not necessary to send the entire amount of intake air into the cylinder by the supercharger, so the capacity of the supercharger can be reduced.

In addition, in such a configuration, during partial load when no supercharging is performed, the air-fuel mixture in the cylinder is connected to a throttle valve that blocks the downstream part of the supercharging system path, that is, the middle of the supercharging system path, and each cylinder. However, if the throttle valve is located at a gathering point in the supercharging system, the space may be large. Since it has a large capacity, there is a disadvantage that the effective compression ratio decreases due to such a backflow phenomenon.

The present invention was made with attention to such circumstances, and includes an intake system path that supplies air-fuel mixture into each cylinder using the negative pressure inside the cylinder that occurs as the piston descends, and a supercharger. A supercharging system that forcibly supplies pressurized air into each cylinder is provided independently, an intake valve that opens and closes the terminal end of the intake system, and A supercharging valve that opens and closes the terminal end is provided separately, and a throttle that is closed during idling operation without supercharging and during partial load is provided at a gathering part located upstream of the supercharging valve in the supercharging system. In addition to intervening valves, check valves that allow only the flow of air or air-fuel mixture in the direction of the cylinders to pass are inserted in the branch passages of this supercharging system to each cylinder, and the intake valves are closed. By setting the timing almost near the bottom dead center, sufficient lift amount of the supercharging valve can be ensured and charging efficiency can be effectively increased even when using a small capacity supercharger. In addition, it is an object of the present invention to provide a supercharged engine that can prevent a decrease in the effective compression ratio even in a partial load range where supercharging is not performed.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Intake system path 2 and supercharging system path 3 for cylinder 1...
are established independently. The intake system passage 2 supplies air-fuel mixture into the cylinder 1 by using the negative pressure inside the cylinder 1 that occurs as the piston 4 descends, and has an intake port 5 that communicates with each cylinder 1 at one end. . . . and an intake passage 7 that communicates the other end of the intake port 5 with an air cleaner 6.
An intake valve 8 for opening and closing the intake port 5 is provided at one end of the intake port 5, and a carburetor 9 is provided in the middle of the intake passage 7.
is inserted. On the other hand, the supercharging line 3 forcibly supplies air pressurized by the supercharger 11 into the cylinder 1, and has one end connected to the cylinder 1.
It has a supercharging port 12 that opens inward, and a supercharging passage 13 that communicates the other end of the supercharging port 12 with the air cleaner 6. The supercharging port 12 is provided at one end of the supercharging port 12.
A supercharging valve 14 that opens and closes 2... is provided, and the supercharger 11 is inserted in the middle of the supercharging passage 13. Note that the supercharger 11 is
It may be a so-called exhaust turbocharger driven by exhaust pressure, or it may be an air pump driven by the rotational force of a crankshaft. Further, a throttle valve 16 is inserted downstream of the supercharger 11 in the supercharging passage 13, that is, upstream of the collecting part 15 of the supercharging passage 13, and A return passage 18 having a relief valve 17 in the inserted portion is provided in parallel. The throttle valve 16 is connected to the throttle valve 10 of the carburetor 9 via a link mechanism or the like.
It is set so that it starts opening when it opens to a predetermined angle (it becomes fully closed in the partial load range from idling operation). Further, the return passage 18 is for returning pressurized air discharged from the discharge port 11a of the supercharger 11 to the intake port 11b side of the supercharger 11 when the throttle valve 16 is closed. The relief valve 17 is designed to allow only the flow of high-pressure air in the direction of arrow X to pass therethrough.

In such an engine, the intake system path 2
The overlap between the opening timing of the intake valve 8 (see solid line a in FIG. 3) and the opening timing of the supercharging valve 14 in the supercharging system 3 (see solid line b in FIG. 3) is calculated as follows: The value is set to be small enough to prevent the air-fuel mixture from flowing backward into the air-fuel mixture. Further, the closing timing of the intake valve in the intake system path is set near the bottom dead center. A branch passage portion of the supercharging system 3 to each cylinder 1, for example, the supercharging port 12...
A check valve 19 is inserted at the joint between the supercharging passage 13 and the supercharging passage 13, respectively. The check valve 19 has a structure called a so-called reed valve, and has a structure in which one direction of the cylinder,
In other words, only air flowing in the direction of arrow Y is allowed to pass through.

With this kind of configuration, the check valve 19 is inserted in the supercharging line 3, so supercharging will automatically end when the pressure before and after the reed valve is balanced, as shown in Figure 3. Even if the supercharging valve is not closed early as in the conventional system shown by the two-dot chain line C, the phenomenon in which the air-fuel mixture filled in the cylinder 1 flows back into the supercharging line 3 when moving to the compression stroke can be avoided. It can be prevented. Furthermore, the overlap between the opening timing of the intake valve 8 and the opening timing of the supercharging valve 14 is set to be small, and the closing timing of the intake valve in the intake system path is set near the bottom dead center, so that the overlap between the opening timing of the intake valve 8 and the supercharging valve 14 is set to be small. There is no inconvenience that the air-fuel mixture in the cylinder 1 is blown back into the intake system path 2 during charging and the charging efficiency is reduced. Therefore, it is possible to set the lift amount or valve opening period of the supercharging valve 14 to a much larger value than conventional ones, and it is possible to obtain a sufficient supercharging effect even when using a small capacity supercharger 1. It has the advantage of being able to In addition, since the check valves 19 are inserted at each branch part of the supercharging system 3, the amount of air-fuel mixture that flows back into the supercharging system 3 during partial load when supercharging is not performed can be minimized. It can be stopped. Therefore, it is possible to effectively prevent a decrease in the effective compression ratio even in the partial load range. That is, the throttle valve 16 closes at partial load.
In the case of a type in which the supercharging system 3 is arranged in the gathering part 15 of the supercharging system 3, the volume between the throttle valve 16 and the supercharging valve 14 tends to be large.
There is a risk that the air-fuel mixture that has flowed into the cylinder 1 during the compression stroke will be pushed back into that space, resulting in a decrease in output. Since each is provided,
Such problems can be effectively resolved.

The structure of the check valve is, of course, not limited to the one described above; in short, any structure can be used as long as it has low resistance and can quickly and reliably prevent backflow. It may be hot.

As detailed above, the present invention provides an intake valve at the end of an intake system path, a supercharging valve at the end of a supercharging system, and a collection of supercharging systems located upstream of the supercharging valve. A throttle valve is provided in the section, a check valve is provided in the branch passage section, and the opening timing of the intake valve is set approximately near the bottom dead center, so that the opening timing of the intake valve and the While the overlap with the opening timing of the charging valve is set to be small, the lift amount or opening timing of the supercharging valve can be set to a much larger value than in the prior art described above. Therefore, supercharging air can be efficiently supplied into the cylinder from the latter half of the intake stroke to the first half of the compression stroke. Therefore,
The advantage is that a sufficient supercharging effect can be obtained even when a small capacity supercharger is used.

Furthermore, since the check valves are provided in each of the branch passages of the supercharging system, even if a throttle valve is provided in the gathering part and the above-mentioned configuration is adopted,
It is also possible to effectively prevent a decrease in the effective compression ratio in the partial load range.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, FIG. 1 is a schematic sectional view showing the main part, and FIG.
The line sectional view, FIG. 3, is a diagram showing valve timing. 1... Cylinder, 2... Intake system path, 3... Supercharging system path, 4... Piston, 8... Intake valve, 11
...Supercharger, 12... Branch passage portion (supercharging port), 14... Supercharging valve, 15... Collection part, 1
6... Throttle valve, 19... Check valve.

Claims (1)

[Claims] 1. An intake system that supplies air-fuel mixture into each cylinder using the negative pressure inside the cylinder that occurs as the piston descends, and a turbocharger that forcibly supplies pressurized air into each cylinder. A supercharging system in which an intake valve that opens and closes the terminal end of the intake system passage and a supercharging valve that opens and closes the terminal end of the supercharging system passage are provided separately, and A throttle valve that closes during idling operation without supercharging and at partial load is provided at the gathering point of the supercharging system located upstream of the valve, and a throttle valve is provided to each cylinder of the supercharging system. A check valve is inserted in each of the branch passages to allow only the flow of air or air-fuel mixture to pass in the direction of the cylinder,
A supercharged engine characterized in that the intake valve closes at a time substantially near bottom dead center.