JPH1026019A - Exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost and to improve the efficiency of catalytic action and precision of detection of oxygen concentration, in an exhaust manifold having an O2 sensor and a catalytic converter. SOLUTION: This exhaust manifold 1 to extremely simplify a shape and a structure and reduce a cost is formed in a way that a first pipe 2 from which a plurality of branch pipes 3 are protruded and a second pipe 4 provided with a sensor mounting part 9 to which an O2 sensor is attached and which incorporates and exhaust emission control catalyst 5 are integrally interconnected in a manner that the axes thereof cross each other. Further, disturbance occurs to a flow of exhaust gas at a sharply bent connection part between the first and second pipes 2 and 4, and the efficiency of catalytic action is increased so that exhaust gas flows in a uniformly dispersed state to the whole of the catalyst 5. Further, by arranging an O2 sensor in the vicinity of the connection part or a flow part right therebelow, oxygen concentration is detected with high-precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold for an internal combustion engine, and more particularly, to an exhaust gas purifying apparatus, in which an O ₂ sensor for detecting oxygen concentration in exhaust gas is provided and a catalytic converter for purifying exhaust gas is integrally provided. It relates to an exhaust manifold.

[0002]

_2. Description of the Related Art An O2 sensor provided in an exhaust manifold and a catalytic converter connected immediately downstream thereof is conventionally known as disclosed in, for example, Japanese Utility Model Laid-Open No. 39418/93. . The configuration of this type of exhaust manifold will be described with reference to FIG.

In FIG. 4, a catalytic converter 23 having a built-in exhaust gas purifying catalyst 24 having a honeycomb structure is connected to an exhaust manifold 21 provided with a plurality of branch pipes 22 each connected to an exhaust port of a cylinder head. ing. The connection portion 25 of the exhaust manifold 21 with the catalytic converter 23 is smoothly curved with a large radius of curvature or bent at an obtuse angle in order to make the flow of exhaust gas smooth. In the illustrated example, the curvature radius is set to be large, and the curvature is made substantially perpendicular. Then, a sensor attachment portion 27 for attaching the O ₂ sensor 26 to the outer peripheral portion of the curved connection portion 25
Are formed. In addition, these exhaust manifolds 21
The catalytic converter 23 has a complicated shape and is usually made of cast iron.

[0004]

However, the configuration in which the exhaust manifold 21 made of cast iron and the catalytic converter 23 are connected as shown in FIG.
There is a problem in that the number of parts and the number of manufacturing and assembling steps increase, resulting in an increase in cost.

The flow of the exhaust gas is reduced by the curved connecting portion 2.
5, the catalyst 24 is mainly used only at the portion corresponding to the outer periphery of the curved connecting portion 25, and the portion corresponding to the inner periphery is rarely used. There is a problem that the efficiency of the catalytic action is deteriorated and the flow resistance of the exhaust gas in the catalyst 24 is increased.

Further, since the exhaust gas flowing on the inner peripheral side of the curved connecting portion 25 does not hit the O ₂ sensor 26, the accuracy of detecting the oxygen concentration in the exhaust gas is deteriorated, and the accuracy of the air-fuel ratio control is deteriorated. There was a problem.

As a sheet metal exhaust manifold integrated type converter, a dome-shaped portion is formed at the entrance of the converter portion, a plurality of branch pipes are extended from the dome-shaped portion, and an O ₂ sensor is provided on the dome-shaped portion. It is also known to mount the gas, but the shape is complicated and the manufacturing cost is also high, and the exhaust gas from each branch pipe is O _2.
There is a problem that the sensor does not hit the sensor evenly and the detection accuracy of the oxygen concentration is poor.

The present invention has been made in view of the above-mentioned conventional problems, and enables an exhaust manifold equipped with an O ₂ sensor and a catalytic converter to be manufactured at low cost, has a high catalytic action efficiency, and has a high accuracy in controlling the oxygen concentration. It is an object to provide an exhaust manifold that can be detected.

[0009]

According to the present invention, there is provided a first pipe provided with a plurality of branch pipes protruding therefrom, and a _second pipe provided with a sensor mounting portion for mounting an O2 sensor and having an exhaust gas purifying catalyst incorporated therein. And the pipes are connected integrally with each other with their axes intersecting. Since the first and second pipes are connected integrally, they are light in weight, extremely simple and low in shape and structure. Can be manufactured at cost. In addition, since the connection between the first and second pipes is sharply refracted, the flow of the exhaust gas is disturbed at the connection, and the exhaust gas is sufficiently mixed and flows through the second pipe. In other words, the exhaust gas is uniformly dispersed and flows throughout the catalyst, so that the entire catalyst is used and the efficiency of the catalytic action is increased. Also,
Since the exhaust gas is sufficiently mixed at the connection portion, the oxygen concentration can be detected with high accuracy by arranging the O ₂ sensor near this connection portion or immediately downstream thereof.

[0010] When the first and second pipes are connected in a sharply refracted state, the flow resistance may be increased due to the disturbance of the flow of exhaust gas at the connection portion.
In fact, the opposite is true. Exhaust gas flows through the catalyst, which is a part having a large flow resistance, as a whole, as described above, so that the flow resistance is greatly reduced, and the output is reduced by the flow resistance of the exhaust gas. Can be reduced.

Further, the first and second pipes are connected so that the crossing angle thereof, that is, the angle between the axes of the two pipes, is acute, and a sharp edge is formed at the corner of the connection between the two pipes. Then, the turbulence of the exhaust gas at the connection portion becomes stronger, and the mixing action is further strengthened, so that a higher effect can be obtained.

Further, when the sensor mounting portion is formed on the closing member on the end face of the second pipe on the side of the connecting portion with the first pipe, it is not necessary to separately provide a sensor mounting portion, and the sensor is mixed with the O ₂ sensor. Since the exhaust gas hits reliably, low-cost and highly accurate detection can be performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1 to FIG. 3, reference numeral 1 denotes an exhaust manifold, and a plurality of branch pipes 3 connected to the respective exhaust ports of the cylinder head are protruded to form a first pipe 2 which constitutes a collective portion of the exhaust manifold. And a second pipe 4 having a built-in exhaust gas purifying catalyst 5 having a honeycomb structure and constituting a catalytic converter section.

The first pipe 2 comprises a straight pipe, one end of which is closed by welding a closed end plate 6,
The other end is a second pipe 4 also made of a straight pipe.
Are connected integrally by welding so as to communicate with each other near one end. These first and second pipes 2 and 4 are connected such that the intersection angle θ between their axes forms an acute angle,
The inner corner 14 of the connection forms an edge.
The distal end of each branch pipe 3 is welded to a single connection flange 7 common to these branch pipes 3.
Is connected to the exhaust side of the cylinder head, whereby each branch pipe 3 is connected to the exhaust port.

One end of the second pipe 4 is closed by welding a disc-shaped closing member 8 having a fitting portion 8a fitted on the inner periphery of the end and a flange portion 8b engaged on the edge. At the center of the closing member 8, a sensor mounting portion 9 including a mounting seat 9a and a mounting screw hole 9b is provided, so that the O ₂ sensor 10 is mounted. The catalyst 5 is held at a position at a suitable distance from the connection of the second pipe 4 with the first pipe 2 to the other end. The other end of the second pipe 4 is bent in a V-shape to form an outlet pipe 11.
Is connected to the end of the outlet pipe portion 11, and a connection flange 12 formed with a connection pipe portion 13 for connection to an exhaust pipe is welded to the end of the outlet pipe portion 11.

The above-described exhaust manifold 1 is made of a stainless steel plate except for the connection flange 7 and the closing member 8, so as to reduce the thickness and weight and prevent perforation due to corrosion. The connection flange 7 is made of a steel plate having a thickness of about several mm in order to secure predetermined rigidity and connection strength, and also to form the sensor mounting portion 9 for the closing member 8.

In the above configuration, the exhaust gas discharged from the exhaust port of the cylinder head enters the first pipe 2 which is the collecting section via each branch pipe 3, and from the first pipe 2 to the second pipe 2. It flows toward the pipe 4. At this time,
Since the connecting portions of the first pipe 2 and the second pipe 4 are connected with their axes intersecting with each other, the exhaust gas flow path is sharply bent at this connecting portion, and the crossing is further performed. Since the angle θ is acute and the inner corner 14 forms an edge, the exhaust gas flowing from the first pipe 2 to the second pipe 4 causes a large turbulence in the flow at the connection. The exhaust gas is sufficiently mixed at this connection portion, and is evenly dispersed in the cross section of the second pipe 4.
In this state, the inside of the second pipe 4 goes downstream. Accordingly, the exhaust gas flows evenly in the exhaust gas purification catalyst 5, whereby the entire exhaust gas purification catalyst 5 is used, and the efficiency of the catalytic action is increased.
In addition, since the gas flows uniformly in the exhaust gas purification catalyst 5, the flow resistance is reduced as compared with the case where the flow is concentrated in a part, and the output decrease due to the flow resistance of the exhaust gas purification catalyst 5 is reduced accordingly. can do.

Further, since the exhaust gas is sufficiently mixed at the connecting portion, the entire exhaust gas hits the O ₂ sensor 10 mounted on the sensor mounting portion 9 provided at the connecting portion, and the high exhaust gas is applied. Oxygen concentration can be detected with high accuracy,
Highly accurate air-fuel ratio control can be performed.

Further, since the exhaust manifold 1 of the present embodiment is constructed by integrally connecting the first pipe 2 and the second pipe 4 formed of straight pipes, the shape and structure are extremely simple. It can be manufactured at low cost. Further, since the sensor mounting portion 9 is formed on the closing member 8 on the end surface of the second pipe 4 on the side of the connection portion with the first pipe 2, it is not necessary to separately provide the sensor mounting portion 9, and O _Since the exhaust gas mixed with the _two sensors 10 surely hits, high-precision detection can be performed at low cost.

In the above embodiment, the sensor mounting portion 9
Is formed on the closing member 8 that closes one end of the second pipe 4. However, depending on the arrangement state of various devices around the engine, the connection portion between the first pipe 2 and the second pipe 4 may be formed. It may be appropriately formed at the vicinity position or immediately downstream position. Also,
The intersection angle θ between the first pipe 2 and the second pipe 4 is preferably set to an acute angle as described above, but may be set to a substantially right angle. The first pipe 2 and the second pipe 4 are advantageously formed of straight pipes from the viewpoint of cost, but if a portion within an appropriate range from the connecting portion is straight, other portions are optional. May be appropriately bent.

[0022]

According to the exhaust manifold of the present invention, since the first and second pipes are integrally connected by crossing their axes as described above, the weight and the shape and the structure are reduced. Can be manufactured very simply and at low cost, and an exhaust manifold provided with an O ₂ sensor and a catalytic converter can be provided at low cost. Also, since the connection between the first and second pipes is sharply refracted, the exhaust gas is sufficiently mixed and dispersed by the turbulence of the exhaust gas flow at the connection, and the exhaust gas is evenly dispersed throughout the catalyst. When the entire catalyst is used, the efficiency of the catalytic action is increased, and as a result, the catalyst can be downsized and the amount of noble metal used can be reduced, so that the cost can be reduced.
Further, since the exhaust gas is sufficiently mixed at the connection portion, the oxygen concentration can be detected with high accuracy by disposing the O ₂ sensor at the connection portion or immediately downstream thereof.

Therefore, according to the present invention, it is possible to provide an exhaust manifold capable of detecting the oxygen concentration with high accuracy at a low cost and high catalytic action efficiency.

[Brief description of the drawings]

FIG. 1 is a front view of one embodiment of an exhaust manifold according to the present invention.

FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;

FIG. 3 is a sectional view taken along the line BB of FIG. 1;

FIG. 4 is a front view of a conventional exhaust manifold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust manifold 2 1st pipe 3 Branch pipe 4 2nd pipe 5 Exhaust gas purification catalyst 9 Sensor mounting part

Claims (1)

[Claims] 1. A first pipe having a plurality of branch pipes projecting therefrom, and a second pipe having a sensor mounting portion for mounting an O ₂ sensor and having an exhaust gas purifying catalyst built therein, and a shaft center thereof. An exhaust manifold characterized in that the exhaust manifold is cross-linked and integrally connected.