JPH02211318A - Exhaust device for multi-cylinder engine - Google Patents

Abstract

PURPOSE:To conduct excellently the re-combustion of exhaust gas by making a constitution in which control valves which make connection between the exhaust ports for cylinders whose exhaust duration overlaps each other, at the time of a low load, and which make shutting off at a predetermined load time excepting the low load time, are provided. CONSTITUTION:Exhaust gas from cylinder 10, 20 whose exhaust duration overlaps each other is led out into an exhaust passage 41 by means of the 1st exhaust ports 18, 18. Meanwhile, at the time of a low load, control valves 43, 43 are opened, and blown down exhaust gas at the 2nd exhaust ports 19, 19, as its blow-down is weak, is pushed back to the self cylinder 10 or 20 by the compression force of other cylinder 20 or 10, and disorder is generated with the self cylinder 10 or 20, and the re- combustion of an unburnt ingredient is expedited. Also, at the time of a predetermined load, for example, at the time of a middle load or the like excepting the low load time, control valves 43, 43 are closed, and shutting off is made between the 2nd exhaust ports 19, 19, so blown-down exhaust gas is returned within the self cylinder 10 or 20 by making reflection by means of these control valves 43, 43, and disorder is generated within the self cylinder 10 or 20, and the recombustion of the unburnt ingredient is expedited.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust system for a multi-cylinder engine, and more particularly to one that improves emissions by re-burning exhaust gas.

(Prior Art) Conventionally, as disclosed in Japanese Patent Publication No. 45-23681, an exhaust system for a multi-cylinder engine of this type includes a housing and a rotor disposed within the housing. In a multi-cylinder rotary piston engine, the three working chambers formed between the housing and the rotor undergo the suction, compression, explosion, expansion, and exhaust strokes in sequence as the rotor rotates. It is known that cylinders having different phase differences are communicated with each other by a communication passage so that high-temperature, high-pressure gas in the working chamber during the stroke is injected into the working chamber during the exhaust stroke. According to this, high-temperature, high-pressure gas ejected into the working chamber during the exhaust stroke imparts high thermal energy to the working chamber, generates turbulence within the working chamber, reburns unburned components, and improves emissions. can be improved.

(Problem to be Solved by the Invention) In general, not only rotary piston engines but also engines, exhaust gas in the cylinder is ejected into the exhaust port that begins to open at the end of the explosion stroke, which is the so-called blowdown (
(exhaust blow) occurs. Therefore, in a multi-cylinder engine, each cylinder is provided with a first exhaust port for guiding exhaust gas into the exhaust passage and a second exhaust port that communicates with other cylinders whose exhaust periods overlap. It is conceivable to blow down the exhaust gas from the cylinder and send it to the other cylinder in the afterburning phase via the second exhaust port for re-combustion, promoting the combustion of unburned components and improving emissions.

However, in that case, when communicating the second exhaust ports with each other, for example, if they are connected to the outside of the engine via a communication passage, the exhaust gas is cooled while flowing through this communication passage, and the above-mentioned re-combustion is effectively carried out. Problems may arise, such as not being able to

The present invention has been made with attention to these points,
The purpose of this is to reburn the exhaust gas that is blown down in the sight cylinder rather than in other cylinders, thereby achieving good reburning of the exhaust gas.

(Means for Solving the Problems) In order to achieve the above object, the present invention returns the blown-down exhaust gas to the sight cylinder and re-burns it by the compression force of other cylinders and the reflection of the blow-down. be.

Specifically, the solution taken by the present invention is to provide, for each cylinder, a first exhaust port for leading exhaust gas to an exhaust passage, and a second exhaust port that communicates with other cylinders whose exhaust periods overlap. This assumes a multi-cylinder engine with In response to this, the second exhaust ports of the cylinders whose exhaust periods overlap are provided with a control valve that communicates with each other during low loads and shuts off during predetermined loads other than low loads.

(Function) With the above configuration, in the present invention, exhaust gas from each cylinder is led out to the exhaust passage through the first exhaust port.

On the other hand, when the load is low, the control valve is open and the second exhaust ports are in communication, so the exhaust gas blown down to the second exhaust port has a weak blowdown.
It is pushed back into the sight tube by the compression force of the other cylinders, causing turbulence within the sight tube, and promoting re-burning of unburned components.

In addition, at a predetermined load other than low load, such as during medium load, the control valve is closed and the connection between the second exhaust ports is cut off, so the exhaust gas blown down to the second exhaust port is It is reflected by the control valve and returns to the sight tube, causing turbulence within the sight tube and promoting re-burning of unburned components.

In this way, the blown-down exhaust gas only moves back and forth in the vicinity of the second exhaust port, so the temperature of the exhaust gas is maintained at a high temperature, and unburned components are re-burned well.

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

FIG. 1 shows a 20-
This shows a rotary type rotary piston engine. In the figure, 10.20 is the first cylinder and second cylinder of the engine. 11 is a rotor housing having a trochoid inner peripheral surface of the first cylinder 10 and the second cylinder 20, and 12 is a side housing provided before and after the rotor housing 11.11. An eccentric shaft 14 having eccentric portions having a phase difference of 180 degrees with respect to each other is supported in this housing. A rotor 13 is disposed in each of the rotor housings 11, and rotatably supported by each eccentric portion of the eccentric shaft 14. Therefore, as the rotor 13 rotates, the three working chambers 15 formed between the housing 11.12 and the rotor 13 are caused to perform suction, compression, explosion, expansion, and exhaust strokes in sequence. As shown in FIG. 2, the exhaust periods of these two cylinders 10 and 20 overlap with each other.

Further, each of the side housings 12 is provided with an intake port 16 so as to communicate with the working chamber 15 during the intake stroke. A collective type intake passage 31 is connected to each intake port 16. The intake passage 31 includes
A throttle valve 32 is provided to adjust the intake flow rate. Further, an injector 33 for supplying fuel to the intake air is provided in the intake passage 31 near each intake port 16.

Further, each of the rotor housings 11 has a first and a second rotor housing 11, which are connected to the working chamber 15 during the exhaust stroke.
Two exhaust ports 18 and 19 are provided respectively. The second exhaust port 19 is connected to the first exhaust port 18.
The opening timing of the second exhaust port 19 is set to be earlier than the opening timing of the first exhaust port 18.

Further, a collective type exhaust passage 41 is connected to the first exhaust port 18 . Furthermore, one of the second exhaust ports is connected via a communication path 42. Control valves 43 are provided at the connection portions of the communication passages 42 with the respective second exhaust ports 19, and each of the control valves 43 is driven by an actuator 44. Further, a communication passage 42 between the two control valves 43 43 is connected to the exhaust passage 41 via a second exhaust passage 45 . moreover,
Each of the second exhaust passages 45 is provided with an on-off valve 46, and each of the on-off valves 46 is driven by an actuator 47. The actuators 44 and 47 are controlled by a control unit 50.

Furthermore, an air flow sensor 34 is provided in the intake passage 31 upstream of the throttle valve to detect the intake flow rate;
Reference numeral 5 denotes a rotation speed sensor for detecting the rotation speed of the engine, and output signals from the respective sensors 34 and 35 are input to the control unit 50.

Actuator 4 by the control unit 50
4.47 operation control will be explained.

(1) During low load, including during idling operation, the control valve 43.
43 is opened, and the on-off valve 46 is closed. That is, the exhaust gas in the working chamber 15 is blown down to the second
The air is ejected into the exhaust port 19, but since the blowdown is weak, the opening of the control valve 43 causes the gas to be injected into the eye cylinder by the compression force of the working chamber 15 of the other cylinder 10, 20 through the communicating passage 42. Pushed back to 10, 20 and eye tube 10
It returns to the working chamber 15 at a temperature of .degree.

Figure 3 shows the experimental results. The solid line in the figure shows the IC emission amount when the control valves 43 and 43 are opened and the on-off valve 46 is closed in the engine of the above embodiment. (without the second exhaust port).

('2J During medium load) At medium load, the control valves 43 and 43 are closed, and the on-off valve 46 is closed. In other words, since the control valve 43 is closed, the exhaust gas blown down to the second exhaust port 19 is , it is reflected by this control valve 43° 43 and passes through the sight tube 1.
The temperature returns to the working chamber 15 of 0.20, and turbulence is generated in the working chamber 15 to promote reburning of unburned components.

Figure 3 shows the experimental results. The dashed line in the same figure shows the IC emission amount when the control valves 43 and 43 are closed and the on-off valve 46 is closed in the engine of the above embodiment. This is less than the engine's IC emissions.

(3) At high load times, the control valves 43 and 43 are opened (and
Open the on-off valve 46. That is, when the load is high, the combustion temperature is high and there are few unburned components in the exhaust gas, so the exhaust gas blown down to the second exhaust port 19 is transferred to the communication path 4.
2 and the second exhaust passage 45 to the exhaust passage 41.

Therefore, in the above embodiment, the blown-down exhaust gas only moves back and forth in the vicinity of the second exhaust port 19 during low load and medium load, so the temperature of the exhaust gas is maintained at a high temperature and the unburned The re-combustion of the components will be performed well, and the emissions will be improved.

Claims (1)

[Claims] (1) In a multi-cylinder engine, in which each cylinder is provided with a first exhaust port for guiding exhaust gas to an exhaust passage, and a second exhaust port that communicates with other cylinders whose exhaust periods overlap, 1. An exhaust system for a multi-cylinder engine, characterized in that a control valve is provided that allows communication between second exhaust ports of cylinders whose exhaust periods overlap each other at low loads, and shuts them off at predetermined loads other than low loads.