JP2002266635A - Exhaust passage structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust passage structure capable of shortening and miniaturizing the total length without impairing the detecting characteristic of an O2 sensor. SOLUTION: In this exhaust passage provided with the O2 sensor mounted near a collecting part 3 where two or more exhaust pipes 2, 2, 2 are collected, and a catalyst 6 mounted in the downstream of the O2 sensor 10, a recessed part 6a recessed to the downstream is formed on an upstream end face of the catalyst 6 for keeping a predetermined distance with respect to the O2 sensor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an exhaust passage of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, an exhaust passage of an internal combustion engine is constituted by members as shown in an exploded view in FIG.
In the cylinder engine, four exhaust pipes 2, 2, 2, and 2 are provided for each cylinder.
2, 2, and 2 form a collecting portion 3 on the downstream side, and a throat portion 4 is formed on the downstream side thereof.
Is arranged downstream of the exhaust manifold 1.
A catalyst case 5 containing a catalyst 6 is connected and fixed by bolts 8 and 8 with a gasket 7 interposed therebetween. As shown in a sectional configuration diagram of a connected state in FIG.
An O ₂ sensor 10 is mounted in the vicinity of the gathering portion 3 of.

As shown in the enlarged cross-sectional view of FIG. 9, the O ₂ sensor 10 has a sensor portion 12 provided at the tip of a mounting screw portion 11 screwed to the collecting portion 3, and a plurality of O ₂ sensors 10 on the outer periphery thereof. A cover 13 having small holes 13a, 13a is covered. When condensed water in the exhaust gas G accumulates between the cover 13 and the sensor unit 12, the O ₂ sensor 10
To output will mad, O ₂ sensor 10 as condensate does not collect has a what is mounted downward as shown in the enlarged view of FIG. 10. The O ₂ sensor 10
Is provided to detect the combustion state of each cylinder by detecting the oxygen concentration in the exhaust gas G. Based on the detection value of the O ₂ sensor 10, the fuel mixture ratio is controlled, and the The amount of fuel supplied to each cylinder is controlled.

In order to measure the combustion state of each cylinder with one O ₂ sensor 10, the exhaust gas G from the four exhaust pipes _{2, 2, 2, 2} is uniformly distributed in the small holes of the O ₂ sensor 10. The position of the sensor portion 12 of the O ₂ sensor 10 is arranged at a position where the exhaust gas G is sufficiently mixed, that is, at a position indicated by L0 in FIG. In addition, the collecting portion 3 is configured to guide the exhaust gas to the outer peripheral side of the catalyst 6.
And the lower end of the throat portion 4 is secured, and the exhaust gas G hits the upstream end face of the catalyst 6 and is rebounded. The rebounded exhaust gas G is sent to the O ₂ sensor 1.
The distance L2 between the O ₂ sensor 10 and the upstream end face of the catalyst 6 is set to be 30 mm or more so that 0 is not detected.

As described above, conventionally, the O ₂ sensor 1
It is necessary to set the L0 and L2 to a sufficient distance and to install the O ₂ sensor 10 at an optimum position in order to ensure the detection accuracy of 0 well and control accurately. There is a problem that the distance becomes long. In order to increase the diameter of the catalyst 6 in order to increase the purification ability of the catalyst 6, it is necessary to increase the length of the throat portion 4, and the catalyst 6 is increased to a certain diameter or more from the viewpoint of mountability on a vehicle. There is a problem that you can not
It is necessary to design a large catalyst 6 in the length direction, and for ease of mounting on a vehicle, for example, as shown in FIG. 11, the catalyst 6 is divided into a first catalyst 61 and a second catalyst 62 and arranged in the exhaust path. The method of doing is taken. In addition, in FIG. 11, R is an engine room, and E is an engine.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and enables a large catalyst to be mounted without deteriorating the detection performance of the O ₂ sensor, thereby reducing the overall length. The first gist of the present invention is to provide a compact exhaust path structure that can be set, and an O ₂ sensor is provided near a gathering portion where two or more exhaust pipes gather.
In the exhaust path catalyst downstream of ₂ sensor is disposed, the upstream end face of the catalyst, a recess which is recessed toward the downstream side in order to ensure a predetermined distance between the O ₂ sensor is formed It is. A second gist is that a convex portion protruding downstream is formed on the downstream end surface of the catalyst. A third gist is that the concave and / or convex portions of the catalyst are formed in a spherical shape or a conical shape from the outer peripheral surface of the catalyst.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram of a connection state between an exhaust manifold 1 and a catalyst case 5 of an internal combustion engine, and FIG. 2 is an enlarged configuration diagram of main parts thereof. The same members as those shown in the conventional example in FIGS. 7, 8, 9 and 10 are denoted by the same reference numerals and described.

Exhaust manifold 1 having four exhaust pipes 2, 2, 2, 2 communicating with each cylinder of a four-cylinder engine
Is attached to the engine via a flange portion 9, and a collecting portion 3 in which four exhaust pipes 2, 2, 2 and 2 are gathered is formed on the downstream side, and further on the downstream side of the gathering portion 3. A throat portion 4 having a flared shape is formed in a continuous shape, and an O ₂ sensor 10 is mounted in the vicinity of the collecting portion 3 in a downward direction. At the center of the upstream end surface of the catalyst 6 provided in the catalyst case 5 connected to the downstream of the exhaust manifold 1, an upper concave portion 6 a is formed to be spherically recessed toward the downstream side. In the center of the downstream end face of
The lower end convex portion 6b protruding in a spherical shape toward the downstream side is formed integrally. This lower end convex portion 6b is used for the catalyst case 5
Is formed so as to protrude so as to be accommodated in the downstream throat portion 5a of the downstream portion.

[0009] As shown in FIG. 2, upper recess 6a is, O ₂
The central portion of the catalyst 6 immediately below (directly downstream of) the tip of the sensor portion 12 of the sensor 10 is recessed toward the downstream side.
The distance between the lower end of the O ₂ sensor and the bottom of the upper concave portion 6a is set to be 30 mm or more, so that even when the exhaust gas hits the upper concave portion 6a of the catalyst 6 and is repelled upstream, the exhaust gas is removed. A distance such that the O ₂ sensor 10 does not detect is ensured.

The upper end recess 6a has a spherical shape.
In addition to the shape like AA, BB or CC
Even if it is depressed in the shape shown by the imaginary line
K, O _TwoA sufficient distance from the lower end of the sensor 10 can be secured.
Anything is fine. Note that a protrusion is formed at the downstream end of the catalyst 6.
The lower end convex portion 6b secures the volume and surface area of the entire catalyst 6.
In order to maintain, the downstream side corresponding to the concave portion of the upper end concave portion 6a
It is formed in a spherical shape in this example.
But formed in a conical shape from the outer peripheral side of the catalyst 6.
It may be something.

[0011] In the present example this manner, since the upper concave portion 6a is formed on the catalyst 6 may be asked to the upstream end face of the catalyst 6 to the O ₂ sensor 10 side, i.e., O ₂ sensor 10 and the catalyst 6
The distance L2 to the upstream end can be made extremely short, and the overall length L3 can be made shorter and more compact than before. In addition, the detection performance of the O ₂ sensor 10 is not impaired, and the fuel supply amount can be favorably controlled. Therefore, the exhaust path can be formed compactly and the mountability to the vehicle can be ensured satisfactorily, and the larger catalyst 6 than before can be installed.

FIG. 3 shows a method of manufacturing the catalyst 6. First, a long cylindrical honeycomb carrier 60 is formed, the honeycomb carrier 60 is rotated, and the bowl-shaped cutter 20 is rotated. In the same manner, the honeycomb carrier 60 is cut into a predetermined size by using the bowl-shaped cutter 20, and as shown in FIG. 4, a spherical upper end concave portion 6a having a spherical shape from the outer peripheral side at the upstream end, and a spherical surface concave portion at the downstream end. The lower end convex portion 6b can be formed.

Incidentally, in the case of the catalyst 6 having a large diameter, FIG.
As shown in FIG. 6, the cutter 21 is cut obliquely into the honeycomb carrier 60 by using the cutter 21, and as shown in FIG. The catalyst 6 can be easily manufactured, and the plurality of catalysts 6 can be manufactured by cutting the honeycomb carrier 60 without waste.

[0014]

According to the present invention, there is provided a collection of two or more exhaust pipes.
O near the joint_TwoA sensor is provided and O _TwoDownstream of the sensor
In the exhaust path where the catalyst is located, the upstream end of the catalyst
On the surface, O_TwoTo ensure a certain distance from the sensor
Owing to the formation of the concave portion recessed downstream,_Two
Short overall exhaust path length without compromising sensor detection performance
And a large catalyst can be mounted.
Therefore, there is an effect that a cheap and compact structure can be obtained.

[0015] Further, since the convex portion protruding downstream is formed on the downstream end face of the catalyst, the volume and surface area of the entire catalyst can be assured by forming the convex portion downstream. Thus, sufficient exhaust gas purification performance can be obtained.

Further, since the concave and / or convex portions of the catalyst are formed in a spherical shape or a conical shape from the outer peripheral surface of the catalyst, the catalyst can be easily cut to a predetermined size using a bowl-shaped cutter or the like. It can be formed by forming.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a state in which an exhaust manifold and a catalyst case are joined.

FIG. 2 is an enlarged cross-sectional configuration diagram of a main part of FIG.

FIG. 3 is an explanatory diagram of an operation for forming a catalyst using a bowl-shaped cutter.

FIG. 4 is a perspective configuration diagram of a catalyst in which a concave portion and a convex portion are formed in a spherical shape.

FIG. 5 is an explanatory diagram of a work in a state of cutting into a conical shape using a cutter.

FIG. 6 is a perspective configuration diagram of a catalyst in which conical concave portions and convex portions are formed.

FIG. 7 is an exploded perspective view of a conventional exhaust path member.

FIG. 8 is a cross-sectional configuration view of a conventional connection state between an exhaust manifold and a catalyst case.

FIG. 9 is a sectional configuration diagram of an O ₂ sensor.

FIG. 10 is an enlarged configuration diagram of a main part showing a positional relationship between an O ₂ sensor and a catalyst.

FIG. 11 is a schematic configuration diagram of a state in which an engine having an exhaust path including two catalysts is mounted on a vehicle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Exhaust manifold 2 Exhaust pipe 3 Collecting part 4 Throat part 5 Catalyst case 5a Downstream throat part 6 Catalyst 6a Upper concave part 6b Lower convex part 10 O ₂ sensor 12 Sensor part 13 Cover

Claims (3)

[Claims] An O ₂ sensor is provided in the vicinity of a gathering portion where two or more exhaust pipes gather, and an O ₂ sensor is provided downstream of the O ₂ sensor. An exhaust path structure, characterized in that a concave portion that is recessed downstream is formed to secure a predetermined distance between the _two sensors. 2. The exhaust path structure according to claim 1, wherein a convex portion protruding downstream is formed on a downstream end surface of the catalyst. 3. The exhaust path structure according to claim 1, wherein the concave and / or convex portions of the catalyst are formed in a spherical shape or a conical shape from an outer peripheral surface of the catalyst.