JPS63297725A - Engine with turbocharger - Google Patents

Abstract

PURPOSE:To enhance the scavenging effect of exhaust gas by providing opening/ closing means in a passage bypassing a turbine of a turbocharger which means is adapted to be opened only under an engine load not lower than a predetermined load and during an overlap period when both suction and exhaust ports are opened. CONSTITUTION:A combustion chamber 2 in each cylinder of an engine 1 is provided with plural suction ports 3 and 4, an exhaust port 5 and an auxiliary exhaust port 6. An exhaust passage 9 connected to the exhaust port 5 is provided with a turbine 17. The turbine 17 is connected through a shaft 18 to a compressor 19 provided in a suction passage 11, thus constructing a turbocharger. A bypass passage 10 independent of the exhaust passage 9 is connected to the auxiliary exhaust port 6. The bypass passage 10 bypasses the turbine 17 to join with the exhaust passage 9. A closing control valve 20 is provided in the bypass passage 10 per each cylinder. The closing control valve 20 is opened under a specific high engine load.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is aimed at improving knocking resistance and increasing compression by effectively scavenging the exhaust gas remaining in the combustion chamber. It is related to the engine.

In engines with prior art superchargers, residual exhaust gas in the combustion chamber is scavenged using boost pressure, and the residual exhaust gas in the combustion chamber causes the combustion chamber temperature to rise, causing knocking, etc. There are known products that improve combustibility and output by preventing the occurrence of. For example, JP-A-6
Publication No. 1-185628 discloses that while the supercharger is running, the so-called overlap period from when the intake valve begins to open to when the exhaust valve ends to close is changed according to the operating state of the engine, thereby reducing the overlapping period. A supercharged engine is disclosed in which exhaust gas is pushed out of a combustion chamber by the pressure of air supply, scavenging the air, and improving combustibility.

However, in a turbocharged engine, as the intake pressure increases, the exhaust pressure also increases, so the intake pressure is higher than the exhaust pressure only in a limited operating range, and the intake boat and exhaust port are opened. There is a problem in that the exhaust gas remaining in the combustion chamber cannot be effectively scavenged by overlapping the two periods.

OBJECT OF THE INVENTION The object of the present invention is to provide a turbocharged engine that improves anti-knocking characteristics and achieves high compression by effectively scavenging exhaust gas remaining in a combustion chamber. It is.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bypass passage that bypasses a turbine, and to provide a bypass passage in which the bypass passage is operated under a predetermined load or higher and during an overlap period when both the intake port and the exhaust port are open. This is achieved by providing a bypass passage opening/closing means that only opens the bypass passage.

In this way, even if the bypass passage opening/closing passage is opened and the exhaust gas is allowed to flow to bypass the turbine during the overlapping period in which the intake port and the exhaust port are both open under operating conditions above a predetermined load, Due to turbocharging, the exhaust energy m is high at the beginning of the exhaust stroke and drops rapidly, so in the latter half of the exhaust stroke when the opening timings of the intake and exhaust ports overlap, even if the exhaust gas is bypassed by the turbine, Turbocharging has almost no effect, and therefore, according to the present invention, turbocharging improves output while effectively scavenging residual exhaust gas in the combustion chamber to improve anti-knocking characteristics and improve high performance. It becomes possible to realize compression.

EXAMPLES Hereinafter, examples of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic diagram of a four-cylinder supercharged engine according to an embodiment of the present invention.

In FIG. 1, the combustion chamber 2 of each cylinder of the engine 1 includes:
The first intake port 3 and the second intake port 4 as well as the exhaust port 5 and the auxiliary exhaust port 6 are open, respectively. A second intake passage 8 independent of the first intake passage 7 is connected to each other, and the exhaust port 5 is
The exhaust passage 9 is connected to the auxiliary exhaust port 6, and a bypass passage 10 that is independent of the exhaust passage 9 is connected to the auxiliary exhaust port 6. The first intake passage 7 and the second intake passage 8 merge into an intake passage 11 upstream thereof, and a fuel injection valve 12 is provided in the intake passage 11 upstream of the merging portion. The first intake port 3, second intake port 4, exhaust port 5 and auxiliary exhaust port 6 are operated at predetermined timing by the first intake valve 13, second intake valve 14, exhaust valve 15 and auxiliary exhaust valve 16, respectively. It is opened and closed.

A turbine 17 is provided in the exhaust passage 9, and the turbine 1
7 is transmitted via a shaft 18 to a compressor 19 provided in the intake passage 11 for supercharging intake air. Further, the bypass passage 10 is connected to the turbine 17.
bypasses and joins the exhaust passage 9, bypass passage 1
0 includes an on-off control valve 20 that opens and closes the bypass passage 10.
is provided. Fuel injection valve 12 and compressor 19
A throttle valve 21 and an intercooler 22 are provided in the intake passage 11 between the two. The exhaust passage 9 includes a bypass exhaust passage 23 and a waste gate valve 24 that controls the opening degree of the bypass exhaust passage 23 in order to control the amount of exhaust gas supplied to the turbine 17.
are provided for each.

FIG. 2 shows the opening/closing timing of the first intake port 3, second intake port 4, exhaust port 5, and auxiliary exhaust port 6 in this embodiment, that is, the first intake valve 13, the second intake valve 14, the exhaust valve 15, and Auxiliary exhaust valve 16
FIG. 3 is a time chart showing the opening/closing timing of the opening/closing control valve 2 in this embodiment.
It is a graph which shows the relationship with opening/closing control of 0.

In FIG. 2, curve X is the lift curve of the exhaust valve 15, curve Y is the lift curve of the auxiliary exhaust valve 16,
Further, the curve Z indicates the lift curves of the first intake valve 13 and the second intake valve 14, respectively. In this embodiment, the first intake valve 13 and the second intake valve 14 are operated at the same timing. It is opened and closed. Further, the opening/closing timing of the exhaust valve 15 is determined by the overlap between the opening period of the first intake valve 13 and the second intake valve 14 and the opening period of the exhaust valve 15, that is,
The settings are such that there is almost no overlap period. The opening/closing timing of the auxiliary exhaust valve 16 is set so that the overlap period between the opening period of the first intake valve 13 and the second intake valve 14 and the opening period of the auxiliary exhaust valve 16 is constant. .

In FIG. 3, a region A indicated by a satin finish is a low-load operating region in which the on-off control valve 20 is closed and exhaust gas is not exhausted from the bypass passage 10. In the low-load operation region, the on-off control valve 20 is opened during the overlap period between the opening periods of the first intake valve 13 and the second intake valve 14 and the auxiliary exhaust valve 16 to direct exhaust gas to the turbine 17. If the exhaust gas is scavenged by lowering the exhaust pressure by bypassing the exhaust gas and exhausting it from the bypass passage 10, combustion will become unstable. is supplied to. Region B shown with diagonal lines is the first intake valve 1
During the overlap period between the opening periods of the third and second intake valves 14 and the auxiliary exhaust valve 16, the on-off control valve 20 is opened, exhaust gas is exhausted from the auxiliary exhaust port 6 through the bypass passage 10, and the exhaust gas is exhausted from the turbine 17. This is a high-load operation area where the system is bypassed.

In this way, the first intake valve 13, the second intake valve 1
4. Set the opening/closing timing of the exhaust valve 15 and the auxiliary exhaust valve 16, and set the first
Only during the overlap period between the opening periods of the intake valve 13, the second intake valve 14, and the auxiliary exhaust valve 16,
The on-off control valve 20 is opened to exhaust the exhaust gas from the auxiliary exhaust port 6 through the bypass passage 10, and the exhaust gas is exhausted to the turbine 17.
By bypassing the exhaust gas, the exhaust pressure is lowered than the intake pressure, and the exhaust gas remaining in the combustion chamber 2 is passed through the bypass passage 10 by the intake air from the first intake valve 13 and the second intake valve 14. It becomes possible to scavenge air. Here, the overlap period between the opening periods of the first intake valve 13 and the second intake valve 14 and the auxiliary exhaust valve 16 is preferably 10 degrees or more in crank angle, more preferably 30 degrees or more in crank angle. setting is desirable to obtain sufficient scavenging effect.

Yes. By setting the overlap period in this way, the amount of exhaust gas remaining in the combustion chamber 2 can be sufficiently reduced, a high charging amount can be obtained with a low boost pressure, and the mixture temperature due to the residual exhaust gas can be reduced. is prevented from rising,
It becomes possible to significantly improve anti-knocking characteristics in high-load operating ranges. As described above, the anti-knocking characteristics in high-load operating ranges are greatly improved, so in turbocharged engines, the compression ratio, which was conventionally set to a low value to prevent knocking, can be changed to a higher value, for example 8.
It can be set to 7 or more, which improves fuel efficiency and output in low-load operating ranges, and also protects the exhaust system by lowering the exhaust gas temperature even in high-speed operating ranges. As a result, the need to enrich the fuel is reduced, so that fuel efficiency characteristics in high-speed driving ranges can also be improved.

According to this embodiment, in the high-load operation region, the combustion chamber 2
It is possible to effectively scavenge the exhaust gas remaining in the engine, improve knocking resistance, and enable high compression.

The present invention is not limited to the above-mentioned examples, but various modifications can be made within the scope of the invention described in the claims, and these are also included within the scope of the present invention. Needless to say.

For example, in the embodiment, the auxiliary exhaust valve 16
The opening/closing timing of the first intake valve 13, the second intake valve 14, and the opening period of the auxiliary exhaust valve 16 are set to be constant, but the overlap period based on the crank angle is set to be constant. Even if the engine speed is low, the actual overlap time is longer as the engine speed is lower, and gradually becomes shorter as the engine speed is higher. There is a risk that intake air may blow through from the auxiliary exhaust port 6 to the bypass passage 10, and in an operating range where the engine speed is high, there is a risk that residual exhaust gas may not be sufficiently scavenged. In order to prevent such a risk, the overlap period based on the crank angle between the opening period of the first intake valve 13, the second intake valve 14, and the auxiliary exhaust valve 16 becomes longer as the engine speed increases. , auxiliary exhaust valve 16
It is also possible to control the timing of opening and closing. Also, the first
The overlap period based on the crank angle between the opening periods of the intake valve 13 and the second intake valve 14 and the auxiliary exhaust valve 16 is set in an operating range where the engine speed is high.
Even if the opening degree of the on-off control valve 20 is set to a constant value that provides a sufficient scavenging effect, and the degree of opening of the on-off control valve 20 is controlled to be small in an operating range where the engine speed is low and to increase as the engine speed increases. good.

Furthermore, in the embodiment described above, the on-off control valve 20 is provided in the bypass passage 110, and by opening it in the high-load operation region and during the overlap period, residual exhaust gas in the combustion chamber 2 is scavenged. However, the opening/closing control valve 20 is not used, and the opening/closing timing of the auxiliary exhaust valve 16 is set so that it opens only in the high-load operation region, or the opening period of the auxiliary exhaust valve 16 is changed only in the high-load operation region. The opening period of the second intake valve 13 and the second intake valve 14 may be set and controlled so as to overlap with each other.

Furthermore, in the embodiment, a bypass passage 1 connected to an auxiliary exhaust port 6 provided in each cylinder of a four-cylinder engine is provided.
Although the on-off control valve 20 is provided in the exhaust passage 9, the bypass passages 1°0 from each cylinder are gathered together and merged into the exhaust passage 9, and the gathering part of the bypass passage 10 and the joining part with the exhaust passage 9 are If an on-off control valve 20 is provided between
The mechanism can be simplified. Although the above embodiments have been described with reference to a four-cylinder engine, it goes without saying that the present invention is applicable to both one-cylinder engines and multi-cylinder engines other than four-cylinder engines. do not have.

Effects of the Invention According to the present invention, it is possible to provide a turbocharged engine that can effectively scavenge the exhaust gas remaining in the combustion chamber, thereby improving anti-knocking characteristics and achieving high compression. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a four-cylinder supercharged engine according to an embodiment of the present invention. FIG. 2 is a time chart showing the opening/closing timing of the first intake valve, second intake valve, exhaust valve, and auxiliary exhaust valve in the embodiment of the present invention, and FIG. 3 shows the engine operating range and the opening/closing control valve timing. It is a graph showing the relationship with opening/closing control. DESCRIPTION OF SYMBOLS 1... Engine, 2... Combustion chamber, 3... First intake port, 4... Second intake port, 5... Exhaust port, 6...
...Auxiliary exhaust port, 7...First intake passage. 8...Second intake passage, 9...Exhaust passage, lO...
・Bypass passage, 11... Intake passage, 12... Fuel injection valve, 13.
...First intake valve, 14...Second intake valve, 15...Exhaust valve, 16...Auxiliary exhaust valve, 17...Turbine, 18...Shaft, 19...
・Compressor, 20... Opening/closing control valve, 21. Bottle or throttle valve, 22... Intertellar, 23... Bypass exhaust passage, 24... Waste gate valve. Figure 2 Figure 3 Upper Nonno Circulation

Claims (1)

[Claims] In a turbocharged engine equipped with a turbocharger driven by exhaust gas from the engine, a bypass passage is provided to bypass the turbine of the turbocharger, and the bypass passage is operated at a predetermined load or higher. 1. A turbocharged engine characterized by being provided with passage opening/closing means that opens only during an overlap period in which an intake port and an exhaust port are both open.