JPS58155214A - Exhaust purifier for motorcycle - Google Patents

Abstract

PURPOSE:To improve exhaust purification performance, by opening the downstream ends of exhaust pipes extending at both sides behind plural cylinders, in an expansion chamber, so that the downstream ends of the exhaust pipes are opposed to the upstream ends of mufflers at both the sides and by providing exhaust gas sensors between the opposed ends of the exhaust pipes and the mufflers. CONSTITUTION:An engine 3 has four cylinders 6, two of which are located at one side and the other two are located at the other side. Carburetors 8 are connected to the intake ports 6a of the cylinders 6 through intake pipes 7. Exhaust pipes 9 extend at both the sides and are connected to the exhaust ports 6b of the cylinders 6. The two exhaust pipes 9 at each side are connected to a common expansion chamber 11 through a confluence 10. Mufflers 12 also extend at both the sides and are coupled to the expansion chamber 11. An exhaust purifying catalyst 13 is provided in each muffler 12. The exhaust pipes 9 are opened in the expansion chamber 11 so that the exhaust pipes are nearly concentrically opposed to the upstream ends of the mufflers 12. Exhaust gas sensors 18 are provided between the opposed ends of the exhaust pipes 9 and the mufflers 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for a multi-cylinder engine in a two-wheeled motor vehicle.

Conventionally, an engine having at least two cylinders is located in the middle of a vehicle body having front and rear wheels, and a common engine (a) that communicates with the exhaust boat of each cylinder and extends rearward and communicates with the exhaust pipe (a) (a). A motorcycle is known which is provided with two expansion chambers (b) and one muffler (c) on one side and one muffler (c) on the other side connected to the expansion chamber. (c
The air-fuel ratio of the exhaust gas upstream of each catalyst (d) is adjusted by adjusting the air-fuel ratio of the exhaust gas upstream of each catalyst (d).
It is conceivable to control the exhaust gas sensor (θ) by a signal from the exhaust gas sensor (θ) in the exhaust gas sensor so as to be prepared for purification by each catalyst (d), but this has the following advantages and disadvantages.

That is, the advantages are: (1) When the exhaust gas sensor (e) is installed in the exhaust pipe (&), the sensor (θ) reduces the JifI air resistance before the exhaust pipe (a) is activated. However, the expansion chamber (b
), such inconvenience does not occur when the sensor (θ) is provided.

The pulsating change in exhaust pressure is buffered by the expansion chamber (b),
This prevents pulsation changes from acting directly on the muffler (0) and adversely affecting the purification performance of the catalyst (DL).

(a) Exhaust gas from the exhaust pipe (a) is diffused into the expansion chamber (b) and flows to the muffler (Q), during which part of the exhaust gas is
The degree of M decreases and the reaction at the catalyst (d) becomes slow.

(b) The ambient temperature of the exhaust gas sensor (θ) becomes relatively low humidity, and the operation of the sensor (θ) tends to become unstable.

That's true.

An object of the present invention is to eliminate the above disadvantages and to provide an exhaust gas purification device that takes advantage of the above-mentioned advantages and still has high performance. an engine having two cylinders, at least one exhaust pipe on one side and one on the other side extending rearward and communicating with the exhaust boat of each cylinder, and the exhaust pipes on one side and the other side communicating with the bean. A common expansion chamber, one muffler on one side and one muffler on the other side connected to the expansion chamber are provided, and each muffler is equipped with a catalyst for air purification of υ1゛. In a device in which the air-fuel ratio of the exhaust gas on each side is controlled by the signal from the exhaust gas sensor in the expansion chamber, the downstream ends of the exhaust pipes on each side are placed in the expansion chamber facing the upstream ends of the mufflers on each side. The exhaust gas sensor is characterized in that the eyes are opened at substantially concentric positions and an exhaust gas sensor is inserted into the opposing gap.

Next, one example of implementing the present invention will be explained with reference to FIGS. 2 to 5.

In the drawing, (1) indicates the vehicle body (11 is the front vehicle + 21 (21), the engine (3) in the middle, the fuel tank (4) above it, and the passenger compartment at the rear). The engine (3) has two cylinders (6) on the minus side and two on the other side, as shown in Fig. 2. It is composed of 4 cylinders with 4 cylinders, and each cylinder (6) has an intake boat (6).
a) is equipped with each carburetor (8) connected via each intake pipe (7), and further includes υ1. of each cylinder (6). It is equipped with two exhaust pipes (9) (9) on one side and the other side that communicate with the air boat (6b) and extend rearward, and two exhaust pipes (IJ) on each side of these sides. ) f91 at each junction (1(
2) A common expansion chamber (lυ) is communicated through (101), and one muffler circle is provided on one side and the other side of the rear side connected to the expansion chamber (11), and each muffler Each three-way catalyst (131) for exhaust purification is provided in the O4, and each exhaust pipe (9
) or each secondary air introduction '#(
141 to allow secondary air to be freely introduced into the exhaust gas through each of these introduction pipes.

Two secondary air introduction pipes (14) on the - side and the other side (14)
) are merged separately and opened into one common air cleaner On at the upstream end of each intake pipe (7) through each reed valve (15) and each control valve (I6). ,
Each exhaust gas sensor (each control valve 06) is controlled to open and close via each control circuit (11) by the national output signal, and the air-fuel ratio of the exhaust gas flowing into the exhaust pipe (91 (91) on each side of -c1 is controlled by the output signal of the country). It is now controlled according to the country's output signal.

Here, the exhaust pipes (9) (9) on each side are connected to the confluence part f1.
01, each muffler (121) is opened in the expansion chamber (11) at its downstream end in a position facing and substantially concentric with the upstream end, and each exhaust gas sensor (121) is placed in the opposing gap. I tried to intervene.

Next, to explain its operation, the exhaust pipes (9) (9) on each side
Exhaust gas from the expansion chamber (Ill) is adiabatically expanded in the expansion chamber (Ill) and flows to the muffler (14) on each side with pulsation changes as buffered as possible, which improves the purification performance of each catalyst OJ. According to the present invention, the exhaust pipe (9) is not particularly different from the one shown in the first diagram described above.
Since the downstream end of the muffler (12) and the upstream end of the muffler (12) are concentrically opposed to each other, a portion of the high-temperature exhaust gas flow from the exhaust pipe (9) is diffused into the expansion chamber (11). It flows directly to the muffler (12j) and acts on the catalyst 0 tank, raising the humidity of the air scum, accelerating the reaction in the catalyst 0:(l, and also increasing the temperature of the exhaust gas sensor 011g from the exhaust pipe (9). The sensor is exposed to a stream of exhaust gas and maintained at a high temperature, allowing stable detection operation.

In the -E%f2 embodiment, the exhaust gas sensor (181) was installed in each side of the exhaust pipe (91 & two, one each, for a total of two, but this was set as one on the - side and one common control It is also possible to adjust the air-fuel ratio using a valve (Ifil).

As described above, according to the present invention, the downstream ends of the exhaust pipes on each side are opened in the expansion chamber in a position substantially concentric with the upstream ends of the mufflers on each side, and the exhaust pipes are opened in the opposing gaps. This device inserts a gas sensor, and takes advantage of the above-mentioned advantages of using an expansion chamber, such as the reduction of ridge resistance and exhaust resistance against pulsation changes, as well as promoting catalyst reaction and stable operation of the exhaust gas sensor. It has the effect of significantly improving purification performance.

4. Brief explanation of the drawings 1. , 1IA is a schematic plan view of the rear part of the conventional device, FIG. 2 is a side 1n1 view of an example of a motorcycle equipped with the device of the present invention, FIG. 4 is a plan view of Abe Q), and FIG. 5 is a cross-sectional view taken along the line V-■ in FIG. 4.

(1+・・・Car body (2)・・・Car wheel (3)・・・・・・Engine (6)・・・・・・Cylinder (6b)...exhaust boat i! -)l...Exhaust pipe Department: Expansion chamber (12j・・・・・・ma)　la fl:()・・・catalyst (I8)・・・Exhaust force sensor 2 people outside Figure 4 18

Claims (1)

[Claims] @ At least 2 in the middle part of the vehicle body with wheels after t1
An engine with several cylinders and an exhaust boat for each cylinder]! I! At least one exhaust pipe on one side and one on the other side that curves and extends in the evening, one common expansion chamber that communicates the exhaust pipes on the two sides and the other side, and one sitting in the expansion chamber. In addition to providing one muffler on one side and one on the other side, catalysts for exhaust purification are provided in each of the 77 chambers, and the air-fuel ratio of the exhaust gas on the upstream side of each catalyst is determined by a signal from an exhaust gas sensor in the expansion chamber. The downstream ends of the exhaust pipes on each side are opened in the expansion chamber at a position substantially concentric with the upstream end of the map on the valley side, and an exhaust gas sensor is installed in the opposing gap. An automatic 2-width small exhaust purification device that is characterized by being inserted.