JPH01163411A - Device for purifying exhaust gas from rotary piston engine - Google Patents

Abstract

PURPOSE:To contrive to employ a pre-catalyst converter of a small size by partitioning an exhaust port into an upper and a lower sections, and thereby letting an upper side passage go around the pre-catalyst converter so that the passage is connected with a main catalyst converter. CONSTITUTION:An insert member 3 is inserted into an exhaust port so that the port is partitioned into an upper and a lower section. Let the upper side passage 8 go around a pre-catalyst converter 13 by means of a bypass pipe 19 so that it is connected with a main catalyst converter 14. Exhaust gas HC concentration of which is comparatively low, in the upper side passage 8 is treated only by the main catalyst converter 14. Owing to this constitution, the pre-catalyst converter of a small size can thereby be enployed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an exhaust gas purification device for a rotary piston engine that includes two catalyst devices, a pre-catalyst converter and a main catalytic converter, in an exhaust passage.

(Prior Art) Conventionally, as described in, for example, Japanese Utility Model Application Publication No. 59-196529, a rotor housing in which a cylindrical insert member is inserted into an exhaust port formed in a rotor housing is known. In this way, by inserting a cylindrical insert member into the exhaust port, the exhaust gas is prevented from being cooled by direct contact with the inner peripheral surface of the exhaust port, and the oxidation reaction of unburned gas in the catalyst device is prevented. can be promoted.

By the way, the exhaust passage is equipped with a small capacity pre-catalyst converter and a large capacity main catalytic converter.
A rotary piston engine in which the pre-catalyst converter is used as an oxidation catalyst to reduce unburned components that increase during low-temperature startup, etc., and the main catalytic converter is used as a three-photocatalyst, for example, to further reduce NOx, etc. In the case of a rotary piston engine, in the exhaust gas purification device of , unburned components (HC
) concentration differs depending on the operating conditions, such as during startup and normal driving, and the concentration distribution within the combustion chamber is quite uneven.As a result, exhaust gas is emitted with a considerably uneven HC concentration, and in reality Despite the fact that some of the HC needs to be processed by the pre-catalyst converter, the HC concentration is so low that the amount that could originally be processed by the main catalytic converter is also passed through the pre-catalyst converter. Therefore, the capacity of the precatalyst converter increases accordingly, and its durability also deteriorates. Furthermore, when all the exhaust gas is passed through the pre-catalytic converter, there is a problem that the exhaust pressure rises significantly, resulting in a drop in engine output.

(Object of the invention) The present invention has been made in view of the above problems, and includes 8
The purpose of the present invention is to downsize the precatalyst converter and improve its durability by allowing only exhaust gas with a high temperature of 0.01C to flow through the precatalyst converter.

(Structure of the Invention) In the case of a rotary piston engine, the HC concentration at the leading end of the combustion chamber is inevitably higher than that at the center. Also, at the end of the exhaust stroke, the exhaust gas at the trailing side end, which has a high temperature of 801 degrees, is collected and exhausted by the apex seal, and any of these exhaust gases with a high temperature of 801 degrees Focusing on the fact that the exhaust gas is discharged from the part of the exhaust port on the lag side in the rotor rotation direction, only the exhaust gas discharged from the part on the lag side in the rotor rotation direction is guided to the pre-catalyst converter. Its configuration is as follows. That is, the rotary piston engine exhaust gas purification device according to the present invention has the following features:
An exhaust passage in which an exhaust port formed in the rotor housing is provided with a pre-catalytic converter having at least an oxidation catalyst upstream, and a main catalytic converter having at least a three-way catalyst downstream of the pre-catalytic converter. and insert into the exhaust port an insert member that divides the exhaust gas passage into upper and lower parts, and only the lower passage located on the lagging side of the insert member in the rotor rotational direction is connected to the main catalyst via the pre-catalyst converter. converter, while the upper passage bypasses the pre-catalyst converter and connects to the main catalytic converter.

(Function) At the moment when the exhaust port starts to open from the lag side in the rotor rotational direction, the exhaust gas with high HC concentration at the leading end of the combustion chamber is discharged from the lag side exhaust port and flows into the lower passage of the insert member. is led to the pre-catalyst converter. Then, when the exhaust port is further opened, the exhaust gas with a low HC concentration in the center of the combustion chamber is discharged into the upper passage of the insert member, and is sent directly to the main catalytic converter. In addition, at the end of the exhaust stroke, the exhaust gas with high HC concentration at the leading end of the combustion chamber is collected by the apex seal and passes from the lagging side of the rotor rotational direction of the exhaust port to the pre-catalyst through the lower passage. Guided by list converter.

In this way, the exhaust gas with a high temperature of 804 degrees mainly passes through the lower passage defined by the insert member and is guided at high temperature to the precatalyst converter near the combustion chamber, where the HC is first reduced through an oxidation reaction. Then, it is sent to the main catalyst converter where HC is further reduced and NO8 etc. are reduced. Furthermore, the exhaust gas whose I-IC concentration is not very high flows through the upper passage directly to the main catalytic converter, where HC is reduced and NOx etc. are also reduced at the same time.

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

FIG. 1 is a longitudinal section of an exhaust port section in one embodiment of the present invention.

As is clear from the figure, the exhaust port 2 formed in the rotor housing 1 has a stepped enlarged portion 2 extending rearward in two steps.
a, 2b are provided, and a cylindrical insert member 3 is inserted and fixed into the exhaust port 2 from the rear. The insert member 3 includes a flange portion 3a, a tapered cylindrical portion 3b connected to an upper opening 4a of the flange portion 3a in a manner that divides the opening of the flange portion 3a into upper and lower halves, and a rotor rotation at the tip of the cylindrical portion 3b. It consists of a guide part 3c that protrudes toward the opening of the exhaust port 2 from the side (lower side) located on the advancing side, and the flange part 3a is on the inner end surface of the outlet side enlarged part 2b of the exhaust port 2. It is fixed to the rotor housing using a spring pin (not shown) in contact with the entire circumference.

The opening of the exhaust port 2 is divided into two by the guide portion 3c of the insert member 3 into a leading side and a lagging side in the rotor rotational direction, and the leading side opening portion 5a is formed in the cylindrical body portion 3b. The upper opening 4a of the flange portion 3a is connected to the upper opening 4a of the flange portion 3a via the first passage 6a, thereby forming an upper passage communicating with a first exhaust passage 8 defined in the exhaust pipe 7. In addition, the delay side listening portion 5b, which is several inches wide, is
The lower opening 4 of the flange portion 3a is passed through the second passage 6b formed between the lower surface of the cylindrical body portion 3b and the bottom wall of the exhaust port 2.
b, and these constitute a lower passage communicating with the second exhaust passage 9 of the exhaust pipe 7.

FIG. 2 schematically shows the overall structure of the exhaust system.

The rotor housing l of the rotary piston engine IO has a two-node peritrochoidal inner circumferential surface, along which a rotor 11 consisting of a three-lobed trochoidal inner envelope rotates. The rotor housing l has a working chamber 1 for the exhaust stroke.
An exhaust port 2 is provided which opens to the exhaust port 2.
Insert member 3 as described above is inserted into. A pre-catalyst converter 13 used as an oxidation catalyst is connected downstream of the second exhaust passage 9 of the exhaust pipe 7, and a main catalytic converter 14 used as a three-way catalyst is further connected downstream thereof. There is. A split air passage 15 is connected to the main catalytic converter 14 .

Two front pipes 17 and 18 are connected downstream of the main catalytic converter 14 via a joint pipe 16. Front pipe 17. t
Two silencers (not shown) are connected to s.

On the other hand, the first exhaust passage 8 of the exhaust pipe 7 is connected to the downstream side of the precatalyst converter 13 by a bypass pipe 19 that bypasses the precatalyst converter 13 .

Exhaust gas with a high HCa content at the leading end and the trailing end of the combustion chamber 12 is discharged from the port 5b on the lagging side in the rotor rotational direction at the moment the exhaust port opens or just before it closes, and enters the pre-catalyst. converter 13
guided by. Moreover, the exhaust gas with a relatively low HO2 degree discharged from the advance-side intake port 5a in the middle of the exhaust stroke bypasses the pre-catalyst converter 13 and is sent directly to the main catalytic converter 14. In this way, efficient exhaust gas purification is performed in accordance with the I-IC concentration, so that the precatalyst converter can be made smaller and more durable.

The present invention is not limited to the above embodiments, and can be implemented in various other ways.

(Effects of the Invention) Since the present invention is configured as described above, exhaust gas with a high HCa concentration is passed through the pre-catalyst converter, while exhaust gas with a relatively low HCl concentration is passed through the pre-catalyst converter as much as possible. It is possible to improve the efficiency of exhaust gas purification by using only the main catalytic converter to process the exhaust gas. Therefore, the pre-catalyst converter can be made smaller and its durability can be improved. Furthermore, by allowing only a portion of the exhaust gas to pass through the precatalyst converter, an increase in exhaust pressure is suppressed, thereby improving engine output.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an exhaust port portion in an embodiment of the present invention, and FIG. 2 is a general schematic diagram of the same embodiment. 1: Rotor housing, 2: Exhaust port, 3: Insert member, 6a: First passage, 6b: Second passage, 8: First exhaust passage, 9: Second exhaust passage, 10: Rokurepiston Engine, 13; Pre-catalyst converter,
14: Main catalyst converter, 19: Bypass pipe. Agent Patent Attorney Jun Shinfuji - Figure 1

Claims (1)

[Claims] (1) A pre-catalyst converter having at least an oxidation catalyst is provided upstream of the exhaust port formed in the rotor housing, and a main catalytic converter having at least a three-way catalyst is provided downstream of the pre-catalyst converter. An insert member that divides the exhaust gas passage into upper and lower parts is inserted into the exhaust port, and only the lower passage located on the lagging side of the insert member in the rotor rotational direction is connected to the lower passage through the pre-catalyst converter. An exhaust gas purification device for a rotary piston engine, characterized in that the upper passage is connected to the main catalytic converter, while bypassing the pre-catalytic converter and connected to the main catalytic converter.