JPH01104920A - Scavenger for engine with supercharger - Google Patents

Abstract

PURPOSE:To aim at improvement in an scavenging effect by installing a guide wall, guiding intake air made to flow into a combustion chamber from an intake port to the side of another intake port, projectingly in the peripheral edge of an opening leading to the combustion chamber in the intake port corresponding to an intake valve large in an overlap. CONSTITUTION:In a cylinder head 3, there are provided with each of intake valves 19, 20, opening or closing respective downstream side openings 16a, 17a in two intake ports 16, 17, and an exhaust valve 21 which opens or closes an upstream side opening 18a in one exhaust port 18, respectively. Likewise, in one side suction passage 7a to be interconnected to the intake valve 19 in one side large in an overlap with the exhaust valve 21, there is provided with a control valve 23 opening or closing this passage. In this constitution, a protuberant guide wall 26 is formed in a peripheral edge of the opening 16a to a combustion chamber 6 in the intake port 16 on one side. Then, intake air made to flow into this combustion chamber 6 from the intake port 16 is guided to the side of the intake port 17 on the other by the guide wall 26.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a scavenging device for scavenging residual exhaust gas in a combustion chamber in a cylinder of a supercharged engine using intake air (fresh air). It is.

(Conventional technology) Conventionally, in a supercharged engine that supercharges intake air,
The high intake boost pressure scavenges the residual exhaust gas in the combustion chamber, suppresses the temperature rise in the combustion chamber due to the residual exhaust gas, and increases the knocking resistance limit performance, improving the engine's combustibility and output. It is known to do so. For example, in the technology disclosed in Japanese Patent Application Laid-open No. 61-185628, the so-called overlap period from when the intake valve begins to open to when the exhaust valve closes is variable depending on the operating state of the engine while the supercharger is operating. , it is proposed to scavenge the residual exhaust gas in the combustion chamber by pushing it out to the exhaust side using the intake supercharging pressure to ensure good combustion performance of the engine, depending on the engine operating condition. has been done.

(Problem to be Solved by the Invention) However, this proposal has a structure in which the overlapping period with the exhaust valve is controlled by changing the opening period of one intake valve. It is necessary to use a cam mechanism or the like for adjustment, which tends to make the control structure extremely complicated.

Therefore, by providing a plurality of intake valves, at least one of which is set to have a large overlap with the exhaust valve, and by providing an on-off control valve in the intake passage communicating with the intake valve, the engine can be heated up. In high load rotation ranges, etc., the control valve is opened and intake air is supercharged through the intake valve with a large overlap, thereby increasing the scavenging effect of intake air supercharging pressure with a relatively simple structure. is possible.

However, in that case, on the other hand, the intake port opening area of the intake valve, which has a long overlap period with the exhaust valve, becomes small, and when the control valve opens and intake air is supercharged through the intake port, the intake air is After flowing into the combustion chamber from the exhaust port, the intake air flows directly toward the exhaust port. Therefore, only the residual exhaust gas in the periphery of the intake air flow is exhausted, and the scavenging effect of the entire combustion chamber cannot be achieved. There is a risk.

In addition, when the control valve is closed and the engine is in a low-load, low-speed range, residual exhaust gas flows back into the intake port, and the exhaust gas that returns to the intake port is sucked into the combustion chamber along with fresh air during the subsequent intake stroke. As a result, there is a risk that the combustibility of the engine may be impaired, so further improvements are desirable.

The present invention has been made in view of the above points, and its purpose is to improve the structure around the opening of the intake port to the combustion chamber for the intake valve that has a long overlap period with the exhaust valve. , the supercharged intake air flows evenly throughout the combustion chamber to promote the scavenging effect on the entire combustion chamber, and also to direct residual exhaust gas to the intake port in the low-load, low-speed range of the engine when the control valve is closed. The aim is to suppress backflow and improve the combustion performance of the engine.

(Means for solving the problem) In order to achieve this object, the solving means of the present invention protrudes from the periphery of the opening to the combustion chamber of the intake port corresponding to the intake valve with a large overlap. The guide wall guides intake air flowing into the combustion chamber from the intake port to the intake port side corresponding to the other intake valve.

That is, the configuration of the present invention includes a supercharger that supercharges intake air into a combustion chamber in a cylinder, and a plurality of intake valves including at least one intake valve whose overlap with an exhaust valve is set to be larger than other intake valves. A control valve is provided to control the opening and closing of an intake passage communicating with the intake valve having a large overlap, and the control valve is opened at least in a high load, high rotation range to remove residual exhaust gas from the combustion chamber in the cylinder. As a scavenging device for a supercharged engine that scavenges air using intake air, the intake air that has flowed into the combustion chamber from the intake port is placed around the periphery of the opening to the combustion chamber of the intake port corresponding to the intake valve with a large overlap. The present invention is characterized by a protruding guide wall that guides the intake port to the intake port corresponding to the intake valve.

(Function) With this configuration, in the present invention, the control valve opens in a high-load, high-speed range of the engine, and the intake passage corresponding to the intake valve that has a large overlap with the exhaust valve is opened. In this state, intake air supercharged by the supercharger is supplied to the combustion chamber in the cylinder, but since the intake valve has a large overlap with the exhaust valve, the residual exhaust gas remaining in the combustion chamber is The supplied high-pressure intake air is pushed out toward the exhaust passage, thereby scavenging the residual exhaust gas in the combustion chamber.

At this time, a guide wall is provided around the opening of the intake port to the combustion chamber corresponding to the intake valve that has a large overlap with the exhaust valve, so that the guide wall allows the flow of air from the intake port into the combustion chamber. The intake air is guided to the intake boat side corresponding to the other intake valve, swirls around the combustion chamber, and then flows to the exhaust port side. Due to this swirling flow of intake air, residual exhaust gas in the combustion chamber is evenly pushed out to the exhaust passage side, thereby promoting scavenging of the entire combustion chamber.

On the other hand, when the engine is under low load and at low speeds, etc., the control valve is closed, and the intake passage corresponding to the intake valve that has a large overlap with the exhaust valve is closed, and the intake passage that corresponds to the intake valve that has a large overlap with the exhaust valve is closed. is supplied to the combustion chamber in the cylinder through the intake valve.

At this time, in the intake passage where the intake valve and the exhaust valve overlap greatly, the residual exhaust gas in the combustion chamber flows back into the intake passage through the intake port, and the backflow exhaust gas flows into the combustion chamber in the subsequent intake stroke. When inhaled, the combustion performance of the engine tends to decrease. However, in the case of the present invention,
The guide wall protruding around the opening of the intake port to the combustion chamber acts as an obstacle, preventing the residual exhaust gas from flowing back into the intake port. Combustibility can be improved and maintained under low load and low rotation speeds.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows the overall configuration of an embodiment of the present invention, in which 1 is a fuel injection type engine comprising a cylinder block 2 and a cylinder head 3, and the cylinder block 2 has a plurality of cylinders 4,4° A piston 5 is fitted into each cylinder 4 so as to be able to reciprocate, and a combustion chamber is formed in the cylinder 4 surrounded by the top surface of the piston 5 and the bottom surface of the cylinder head 3. 6 is formed. 7 is an intake passage that supplies intake air to the combustion chamber 6 in each cylinder 4;
is an exhaust passage for discharging exhaust gas in the combustion chamber 6,
The upstream end portion of the intake passage 7 is connected to an air cleaner 9, and in the intake passage 7 downstream of the air cleaner 9, air flow meters 10 are installed to measure the intake air amount in order from the upstream side.
, a throttle valve 11 that throttles the intake passage 7, and an engine 1.
A mechanical supercharger 12 (roots-type supercharger) that is driven by a crankshaft 1a of the cylinder 1 and supercharges intake air;・・・
A surge tank 13 is provided to alleviate intake air interference, and the intake passage 7 on the upstream and downstream sides of the supercharger 12
Bypass passage 14 that returns the supercharged intake air to its upstream side
An on-off valve 15 is provided in the bypass passage 14.

As shown in FIG. 1, the intake passage 7 on the downstream side of the surge tank 13 (the downstream end portion of the intake passage 7) is connected to the combustion chamber 6 in each cylinder 4 and has a It is branched into two intake passages 7a and 7b. That is, in the cylinder head 3, each downstream end has a first opening and a first opening at an angular interval of about 60'' in the circumferential direction in one half of the lower surface of the syringe head 3 facing the combustion chamber 6 in the cylinder 4. Similarly, the upstream end of the second two intake ports 16.17 is located at the other part of the lower surface of the silicator head 3 facing the combustion chamber 6 (openings 16a, 17 of the above-mentioned two intake ports 16.17).
One exhaust port 18 opening on the side opposite to a) is formed through the first and second intake ports 16, 17.
Accordingly, the first and second intake passages 7a, 7, respectively.
The exhaust port 18 constitutes the upstream end portion of the exhaust passage 8.

Further, the cylinder head 3 includes a first intake valve 19 that opens and closes the downstream end opening 16a of the first intake port 16, and a downstream end opening 17 of the second intake port 17.
A second intake valve 20 that opens and closes a, and an exhaust port 18
These intake/exhaust valves 19 to 21 are provided with an OHC type valve operating mechanism drivingly connected to the crankshaft 1a of the engine 1, as shown in FIG. 22.

As shown in FIG. 2, due to the cam timing in the valve mechanism 22, the first intake valve 19 that opens and closes the first intake port 16 overlaps with the exhaust valve 21. The overlap between the second intake valve 20 and the exhaust valve 21, which is opened and closed, is set to be larger than the overlap between the second intake valve 20 and the exhaust valve 21.

In addition, the first intake passage 7a which has a large overlap with the exhaust valve 21 (the first intake passage 7a communicating with the valve 19) has a large overlap with the exhaust valve 21.
A control valve 23 consisting of a butterfly valve that opens and closes the first intake passage 7a is disposed at its upstream end. As shown in FIG. 4, the control valve 23 is opened and closed by an actuator 25 controlled by a control unit 24 so as to close when the engine 1 is under low load and at low rotation speed, and open when the engine 1 is under high load and high rotation speed. Therefore, in a high-load, high-speed range of the engine 1, the control valve 23 is opened to scavenge the residual exhaust gas in the combustion chamber 6 in the cylinder 4 by intake air passing through the first intake passage 7a.

As a feature of the present invention, on the lower surface of the cylinder head 3 facing the combustion chamber 6 in each cylinder 4, the first intake valve 1 has a large overlap with the exhaust valve 21.
9, the periphery of the opening 16a of the first intake port 16 to the combustion chamber 6, specifically, the downstream end opening 16a of the first intake port 16 and the upstream end opening 18a of the exhaust port 18.
A protruding guide wall 26 is provided on the opposite side of the downstream end opening 17a of the second intake port 17 with respect to the line connecting the two. 16 into the combustion chamber 6 is guided to the second intake port 17 side corresponding to the second intake valve 20. Note that in FIGS. 1 and 3, 27 is an injector that injects and supplies fuel to the branching portions of the first and second intake passages 7a and 7b. Also, in Figure 1, 2
8 is a spark plug.

Therefore, in the above embodiment, when the engine 1 is in a low load and low rotation range, the control valve 23 is closed under the control of the control unit 24, and the first intake valve 19, which has a large overlap with the exhaust valve 21, is closed. The corresponding first intake passage 7a is closed, and the intake air supercharged by the supercharger 12 is transferred to the second intake passage 7b corresponding to the second intake valve 20, which has a small overlap with the exhaust valve 21.
The fuel is supplied to the combustion chamber 6 in each cylinder 4 via.

At this time, since the first intake valve 19 and the exhaust valve 21 overlap greatly, the residual exhaust gas in the combustion chamber 6 flows from the downstream end opening 16a of the first intake port 16 to the first intake passage 7a. The backflow exhaust gas is sucked into the combustion chamber 6 in the subsequent intake stroke, and the combustibility of the engine 1 tends to decrease.
Since a guide wall 26 is provided protruding around the opening 6a of the intake port 16 to the combustion chamber 6, the guide wall 26 becomes an obstacle and prevents the residual exhaust gas from entering the first intake port 16. backflow is prevented. This makes it possible to improve and maintain the combustibility of the engine 1 at low load and low speed.

On the other hand, in the high-load, high-speed range of the engine 1, the control valve 2
3 is opened to open the first intake passage 7a, and the intake supercharged by the supercharger 12 flows into the in-cylinder combustion chamber 6 through both the first and second intake passages 7a and 7b. is supplied to

At this time, since the first intake valve 19 corresponding to the first intake passage 7a has a large overlap with the exhaust valve 21, the residual exhaust gas remaining in the combustion chamber 6 is absorbed by the supercharged gas. Exhaust port 1 by high pressure intake
This allows residual exhaust gas to be scavenged from the combustion chamber 6.

Also, the first intake port 16 corresponds to the first intake valve 19 which has a large overlap with the exhaust valve 21.
A guide wall 2 protruding from the periphery of the opening 6a to the combustion chamber 6.
6, the intake air flowing into the combustion chamber 6 from the first intake port 16 is guided to the opening 17a side of the second intake port 17, and rotates around the combustion chamber 6 in the counterclockwise direction in FIG. After that, the intake air flows toward the exhaust port 18 side, and the residual exhaust gas in the combustion chamber 6 is evenly pushed out toward the exhaust port 18 side by this swirling flow of intake air, thereby effectively promoting scavenging of the entire combustion chamber 6. be able to.

In the above embodiment, the two intake valves 19°20 and 1
Although the present invention is applied to an engine 1 having two or more exhaust valves 21, the present invention is also applicable to an engine having three or more intake valves or an engine having a plurality of intake valves and two or more exhaust valves. Of course you can.

Further, in the above embodiment, the case where the present invention is applied to the engine 1 equipped with a mechanical supercharger 12 is shown, but the present invention can also be applied to an engine equipped with a turbo supercharger.

(Effects of the Invention) As explained above, according to the present invention, a plurality of intake valves of a supercharged engine are provided, and at least one of them
The overlap between one intake valve and the exhaust valve is set longer than the other intake valves, and a control valve is provided that closes the intake passage communicating with the intake valve at least in the high-load, high-speed range of the engine. By providing a protruding guide wall on the periphery of the opening to the combustion chamber of the intake port corresponding to the valve, the guide wall guides the intake air flowing into the combustion chamber from the intake port to the intake port corresponding to the other intake valve. In the high-load, high-speed range of the engine, the intake air supercharged by the supercharger can be swirled within the combustion chamber to promote scavenging of the entire combustion chamber, and the control valve can be closed when the engine is under low load and low speed. When this occurs, the guide wall prevents the residual exhaust gas in the combustion chamber from flowing back into the intake passage through the intake valve with a large overlap, thereby improving and maintaining the combustibility of the engine.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic plan view of the lower surface of the cylinder head viewed from the combustion chamber in the cylinder of the engine, FIG. 2 is a diagram showing the opening and closing timing of intake and exhaust valves, and FIG. The figure is an overall configuration diagram, and FIG. 4 is a characteristic diagram for controlling the opening and closing of the control valve. 1...Engine, 4...Cylinder, 6...Combustion chamber, 7
...Intake passage, 7a...First intake passage, 7b...
・Second intake passage, 12...supercharger, 16...first
intake port, 16a... opening, 17... second intake port, 18... exhaust port, 19... first intake valve, 20... second intake valve, 21...・・・
Exhaust valve, 23... Control valve, 26... Guide wall. Fig. 4: Craftsmanship, Nwan Dharma - Height Fig. 1 Fig. 2 Crank angle

Claims (1)

[Claims] (1) A plurality of intake valves including a supercharger that supercharges intake air into the combustion chamber in the cylinder, and at least one intake valve whose overlap with the exhaust valve is set to be larger than other intake valves. A control valve is provided for controlling the opening and closing of an intake passage communicating with the intake valve having a large overlap, and the control valve is opened at least in a high-load, high-speed range to scavenge residual exhaust gas in the combustion chamber in the cylinder by intake air. A scavenging device for a supercharged engine, wherein the intake air flowing into the combustion chamber from the intake port is collected at the periphery of the opening to the combustion chamber of the intake port corresponding to the intake valve with a large overlap. A scavenging device for a supercharged engine, characterized in that a guide wall is provided protrudingly to guide the intake port side corresponding to the intake valve.