JPS6256326B2 - - 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.

Conventionally, in this type of engine, for example, each cylinder is provided with a supercharging port in addition to a normal intake port, and the negative pressure inside the cylinder that is generated as the piston descends is used to transfer air from the intake port to the cylinder. In addition to supplying air-fuel mixture into the cylinder, air or air-fuel mixture pressurized by a supercharger is forcibly fed into the cylinder from the supercharging port to improve charging efficiency and output. What has been made possible is known.

However, engines that adopt this type of supercharging system have the advantage of being able to use a small-capacity supercharger, since it is not necessary to send the entire amount of intake air into the cylinder using a supercharger. However, on the other hand, there are many difficulties in setting the valve timing, etc., and it is difficult to achieve sufficient performance over the entire rotation range of the engine.

In other words, with this type of configuration, the overlap between the opening period of the intake valve provided at the intake port and the opening period of the supercharging valve provided at the supercharging port is set to be large, so that when the intake valve is fully open, If the supply valve is also opened to perform supercharging, the pressure inside the cylinder will become higher than the pressure in the intake port, and the air or mixture filled in the cylinder will flow back to the intake port, impairing the supercharging effect. This problem is particularly likely to occur in the low-speed rotation range where intake inertia is small. Therefore, in reality,
As shown in Figure 1, it is necessary to set the overlap between the opening period of intake valve a and the opening period of supercharging valve b to zero or a minimum value, and also to shorten the operating period of each valve a and b. I have no choice but to.
However, under these circumstances, if the lift amount of each valve a and b is set to ensure a sufficient intake passage area, the acceleration of the valves a and b will increase, resulting in abnormalities such as so-called valve dancing. There is a disadvantage that the valve behavior is likely to occur, and the rotational speed at which normal operation can be performed is limited to a low value. Furthermore, if the intake valve is set to close early, the amount of intake air from the intake port will be extremely reduced in the high speed rotation range, which will reduce the supercharging effect. In other words, as shown in Fig. 2, even in a normal engine that does not perform supercharging, the volumetric efficiency is approximately constant over the entire rotation range when the intake valve is kept open for a sufficient period of time (solid line C). On the other hand, when the intake valve is closed early (dotted-dash line d), the volumetric efficiency tends to decrease dramatically in the high-speed rotation range, but this tendency is similar to the intake system in this type of supercharged engine. This is inherited directly from the air intake characteristics of the engine, and the problem arises that the supercharging effect is diminished due to this phenomenon of reduction in volumetric efficiency. However, this problem can be temporarily solved by increasing the amount of air supplied from the supercharging port, but in order to do so, the supercharging pressure is increased and a large amount of air is required during the short period when the supercharging valve is open. It is necessary to send air into the cylinder,
Since it is essential to increase the capacity of the supercharger, this goes against the original purpose of this type of supercharging system, which is to downsize the supercharger.

Therefore, in recent years, in configurations in which the intake port and the supercharging port are provided independently, the overlap between the opening period of the intake valve and the opening period of the supercharging valve is reduced in the low speed range, and in the high speed range. A device that can be made larger has been developed (see JP-A-55-137314). However, since this system focuses on the fact that the intake inertia increases in the high-speed rotation range and increases the overlap in that rotation range, there is naturally a limit to the amount of increase, and the above-mentioned problems naturally occur. The problem has not yet been resolved. In addition, in order to increase or decrease the overlap, a configuration for changing the valve timing is essential, resulting in the disadvantage that the valve operating mechanism becomes complicated.

The present invention has been made in view of these circumstances, and is achieved by inserting a check valve in the middle of the intake system path including the intake port, which allows only the flow of the air-fuel mixture toward the cylinder to pass through. The present invention aims to eliminate the above-mentioned disadvantages and provide a supercharged engine that can exert sufficient supercharging effect up to high speed rotation range even when using a small-capacity supercharger. . Furthermore, by making the air-fuel ratio uniform in the partial load range, it is possible to dilute the air-fuel mixture throughout the engine, thereby improving the fuel consumption rate.

An embodiment of the present invention will be described below with reference to FIGS. 3, 4, and 5.

An intake system passage 2 and a supercharging system passage 3 are provided independently for the cylinder 1. The intake system passage 2 is connected to the piston 4
An intake port 5 whose one end communicates with the inside of the cylinder 1 is used to supply the air-fuel mixture into the cylinder 1 by using the negative pressure inside the cylinder 1 that occurs as the air falls.
and an intake passage 7 that communicates the other end of the intake port 5 with an air cleaner 6. and,
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 inserted in the middle of the intake passage 7. On the other hand, the supercharging line 3 forcibly supplies air pressurized by the supercharger 11 into the cylinder 1, and includes a supercharging port 12 whose one end opens into the cylinder 1, and a supercharging port 12 that opens into the cylinder 1 at one end. The supercharging passage 13 communicates the other end of the supercharging port 12 with the air cleaner 6. A supercharging valve 14 for opening and closing the supercharging port 12 is provided at one end of the supercharging port 12, and the supercharger 11 is inserted in the middle of the supercharging passage 13. ing. Note that the supercharger 11 may be a so-called exhaust turbocharger driven by exhaust pressure, or may be an air pump driven by the rotational force of a crankshaft. Further, the downstream part of the supercharging passage 13 from the supercharger 11, that is,
A throttle valve 15 is inserted upstream of the gathering part 19 of the supercharging system path, and a return passage 17 having a relief valve 16 is provided in parallel at the part of the supercharging passage 13 where the supercharger 11 is inserted. ing. The throttle valve 15 is connected to the throttle valve 10 of the carburetor 9 via a link mechanism or the like, and starts opening when the throttle valve 10 opens a predetermined angle (from idling to partial load range). (fully closed). Further, the return passage 17 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 15 is closed. The relief valve 16 is designed to allow only the flow of high-pressure air in the direction of the arrow x to pass therethrough.

In such an engine, the intake system path 2
A check valve 18 is inserted at a branch passage portion to each cylinder, for example, at a junction between the intake port 5 and the intake passage 7. The check valve 18 has a structure called a so-called reed valve, and is configured to allow the air-fuel mixture to flow only in the direction of the cylinder, that is, in the direction of arrow Y. Then, set the valve timing to 5th.
The settings are as shown in the figure. That is, the opening/closing timing and lift amount of the intake valve 8 are set to substantially the same values as those of a normal engine without a supercharger. On the other hand, the supercharging valve 14 begins to open in the range of 60° to 90° before bottom dead center (BDC), its maximum lift is near the bottom dead center, and it closes in the range of 60° to 90° after bottom dead center. Driven.

With such a configuration, the check valve 18 is inserted in the middle of the intake system passage 2 to allow only the flow of air-fuel mixture toward the cylinder 1 to pass, so that the opening period of the intake valve 8 and the supercharging time can be controlled. Even if supercharging is performed when the intake valve 8 is sufficiently open by setting a large overlap with the opening period of the valve 14, the air-fuel mixture in the cylinder 1 will not flow back into the intake system path 2 without limit. . Therefore, it is possible to lengthen the opening period of each of the valves 8 and 14, and even if the lift amount of each of these valves 8 and 14 is set sufficiently large, the acceleration of the valve increases and the valve dances in the high speed rotation range. It does not cause any inconvenience. Moreover, with this type of engine, there is no need to close the intake valve 8 early, and it can be opened and closed at the same timing as a normal engine that does not perform supercharging, so it can be used as the base of combustion even in the high-speed rotation range. A sufficient amount of intake air from the intake system path 2 can be ensured. In other words, in the case of this embodiment, 30 degrees before bottom dead center where effective supercharging begins
Up to 20 degrees, the lift of the intake valve 8 is large and has a sufficient suction effect, so it shows the same characteristics as the solid line C in Fig. 2, and the intake air from the intake system path in the high speed range. There is no sudden drop in volumetric efficiency. Therefore, even if the amount of air sent into the cylinder 1 from the supercharging line 3 is relatively small, a sufficient supercharging effect can be obtained. To be more specific, in the case of this embodiment, as shown in FIG. Although the amount of intake air will be slightly lower than that without supercharging (dotted chain line f) due to the influence of Since there is no significant decrease in the amount of intake air in the cylinder 1, the total amount of intake air into the cylinder 1 can be reduced by supplying a relatively small amount of pressurized air from the supercharging system 3 in any rotation range. (solid line g) exceeds the amount of intake air (dotted chain line f) when supercharging is not performed. Therefore, even if a small-sized supercharger is used, there is an advantage that a sufficient supercharging effect can be exhibited up to the high speed rotation range. Furthermore, this engine can obtain the above-mentioned effects with an extremely simple configuration in which the check valve 18 is inserted in the branch passage portion of the intake system path 2 to each cylinder, and the valve timing can be made variable. It is easy to implement since there is no problem such as a complicated valve mechanism as in the case.

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's okay to be hot.

Further, a throttle valve 15 is inserted in the supercharging system upstream of the gathering portion 19, and the throttle valve 15 is configured to be fully closed from idling operation to partial load operation. Therefore, when the engine is operated at a load lower than this partial load range, when the auxiliary intake valve 14 opens, the pressure in the collecting part 19 and the pressure in the cylinder are balanced, so that the pressure in the previous compression stroke is reduced. By injecting the compressed air-fuel mixture into the cylinder that is in the intake stroke, it improves variations in the air-fuel ratio between cylinders, and also creates turbulence in the air-fuel mixture within the cylinder, which helps improve combustion. Then, as the compression process further progresses from this state, a part of the air-fuel mixture is pressurized and stored in the collecting section 19 of the supercharging system, and the cycle is repeated.

By repeating this cycle in the partial load range, the air-fuel ratio is equalized, and the air-fuel ratio is set leaner because it improves ignition combustibility by causing turbulence in the air-fuel mixture. Therefore, it is possible to improve the fuel consumption rate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the valve timing of a conventional example, and FIG. 2 is a characteristic diagram showing the relationship between engine speed and volumetric efficiency when the intake valve timing is changed in an engine that does not perform supercharging. 3 to 6 show an embodiment of the present invention,
Fig. 3 is a schematic sectional view showing the main parts, Fig. 4 is a sectional view taken along line A-A in Fig. 3, Fig. 5 is a diagram showing valve timing, and Fig. 6 is a diagram showing the crankshaft rotation angle and intake air during the intake process. FIG. 3 is a characteristic diagram showing the relationship with quantity. 1... Cylinder, 2... Intake system path, 3... Overpressure system path, 4... Piston, 15... Throttle valve,
18...Check valve, 19...Collection part.

Claims (1)

[Claims] 1. An intake system that supplies the air-fuel mixture into the cylinder by using the negative pressure inside the cylinder as the piston descends, and an air-fuel mixture that is forced into the cylinder by pressurized air or air-fuel mixture by the supercharger. and a supercharging system that supplies air to each cylinder independently, wherein a check valve is inserted in a branch passage of the intake system to each cylinder to allow only the flow of the air-fuel mixture in the direction of the cylinder. In addition, the supercharged engine is characterized in that the supercharging system path is provided with a throttle valve upstream of the collecting section.