JPH0618291Y2 - Mounting structure for oxygen concentration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an internal combustion engine, and more particularly to a mounting structure for an oxygen concentration sensor.

[Conventional technology]

Providing an oxygen concentration sensor in the exhaust system of an internal combustion engine is widely performed not only in electronically controlled fuel injection engines but also in engines with a carburetor. In an electronically controlled fuel injection engine, the basic injection amount is set according to the intake air amount (intake pipe pressure), feedback control is performed based on the output of the oxygen concentration sensor, and the fuel is adjusted so that the air-fuel ratio actually approaches the theoretical air-fuel ratio. The injection amount is corrected. By-pass air is similarly corrected in engines with a carburetor. In order to perform better feedback control, the oxygen concentration sensor must be responsive and highly accurate, and in order to achieve this,
The installation position in the exhaust system is also important.

Conventional oxygen concentration sensors are generally installed relatively upstream of the exhaust system, ie upstream of the catalytic converter, in order to respond as quickly as possible to the exhaust emitted from the engine. However, if the oxygen concentration sensor is set at a position relatively upstream of the exhaust system, it will be affected by the variation between the cylinders and easily affected by the high temperature of the exhaust gas.
Therefore, there has been a problem that the detection characteristics may change with time or may be affected by manufacturing errors of individual sensors. In order to solve this, JP-A-53-10379
In Japanese Patent No. 6, the second oxygen concentration sensor is provided downstream of the catalytic converter, and the first oxygen concentration sensor on the upstream side is monitored. Downstream of the catalytic converter, the exhaust temperature is low, various poisonous substances are trapped, and variations among the cylinders are eliminated, so that the detection accuracy can be improved although the response is not high. Therefore, by combining the first sensor and the second sensor, feedback control with excellent responsiveness and accuracy can be performed.

[Problems to be solved by the invention]

The dual-bed catalytic converter in which the three-way catalyst and the oxidation catalyst are housed in a common case can purify the three main harmful components HC, CO, and NOx in the exhaust gas very efficiently. In general, since secondary air is supplied between the two, if an oxygen concentration sensor is provided downstream of the dual bed catalyst, the supplied secondary air will be detected. Further, in a general dual bed catalytic converter, a secondary air introduction pipe is simply connected to the space between the three-way catalyst and the oxidation catalyst, and the secondary air supplied in this manner is the space described above. It is difficult to spread over the whole, and high purification efficiency using the entire oxidation catalyst cannot be realized.

Therefore, an object of the present invention is to provide a dual-bed catalytic converter improved so that the average secondary air is supplied to the entire oxidation catalyst with a structure in which an oxygen concentration sensor is attached so as not to be affected by the secondary air. Is to provide.

[Means for solving problems]

The mounting structure of the oxygen concentration sensor according to the present invention is the mounting structure of the oxygen concentration sensor to the dual bed catalytic converter provided in the exhaust system of the internal combustion engine and having the three-way catalyst and the oxidation catalyst arranged on the exhaust downstream side. The dual-bed catalytic converter has a pipe for introducing secondary air that substantially traverses a space between the three-way catalyst and the oxidation catalyst in a radial direction, and the pipe has a pipe in an axial direction thereof. Each portion is provided with an air outlet for blowing secondary air at least in the exhaust upstream direction and the exhaust downstream direction, and the oxygen concentration sensor is installed on the exhaust upstream side of the pipe in the space. Between the pipe and the pipe, means for preventing the secondary air blown from the air outlet from directly hitting the oxygen concentration sensor is provided. It is characterized in that is.

〔Example〕

In FIG. 2, 10 is an engine body, 12 is an intake manifold, and 14 is an exhaust manifold. A fuel injection valve 16 is attached to the intake manifold 12, and the fuel injection valve 1
6 is controlled by the electronic control unit 18. The exhaust manifold 14 is connected to the catalytic converter 22 by the exhaust pipe 20, and the catalytic converter 22 is further connected to the exhaust pipe 24 on the downstream side thereof. In the system of the present invention, the first
The oxygen concentration sensor 26 of the upstream side of the catalytic converter 22,
It is attached to the collective portion of the exhaust manifold 14 or the exhaust pipe 20 on the upstream side. Further, the second oxygen concentration sensor 2
8 is directly attached to the catalytic converter 22. These first and second oxygen concentration sensors 26 and 28 are publicly known ones for detecting the oxygen component concentration in the exhaust gas, and detailed description thereof will be omitted here. The detection outputs of the first and second oxygen concentration sensors 26, 28 are sent to the electronic control unit 18, and the electronic control unit 18 feeds back the fuel injection from the fuel injection valve 16 based on the outputs of these sensors 26, 28. Control. The control method is not the subject of the present invention, and will be omitted.

As shown in FIG. 1, the catalytic converter 22 is a dual-bed catalytic converter in which a monolithic three-way catalyst 30 and an oxidation catalyst 22 are housed in a common case 34 with a space therebetween. The three-way catalyst 30 and the oxidation catalyst 32 are supported by a case 34 via a wire mesh 36, respectively, and a seal 38 is provided at an upstream end of the case 34, so that exhaust gas flowing in the direction of the arrow is transmitted to the catalysts 30, 32 and the case. It does not leak between 34 and. Secondary air is supplied from the perforated pipe 40 to the space between the three-way catalyst 30 and the oxidation catalyst 32 to assist the oxidation reaction of the oxidation catalyst 32. The pipe 40 is welded to the case 34 at its root.

In the space between the three-way catalyst 30 and the oxidation catalyst 32, the second oxygen concentration sensor 28 described above is further arranged so as to project. The second oxygen concentration sensor 28 has a perforated protective cover 2
It is covered with 9 and is arranged at a position upstream of the secondary air introducing pipe 40. A large number of holes 42 serving as air injection ports of the pipe 40 are provided on the entire peripheral surface of the pipe 40. In the present invention, a canopy 44 surrounding the tip of the pipe 40 is further provided. The eaves 44 is welded to the case 34, and the case 3 of the second oxygen concentration sensor 28.
4 which is slightly longer than the length of the protruding portion. As shown in FIG. 3, the eaves 44 has a semicircular cross section, is located between the second oxygen concentration sensor 28 and the pipe 40, and the air injected from the hole 42 of the pipe 40 has the second oxygen concentration. It prevents direct contact with the sensor 28.
Therefore, the second oxygen concentration sensor 2 passes through the three-way catalyst 30.
The secondary air supplied from the pipe 40 is not mixed into the exhaust gas toward the second oxygen concentration sensor 28, and the second oxygen concentration sensor 28 exhausts the exhaust gas passing through the three-way catalyst 30. It is possible to accurately detect the oxygen component concentration in the inside. On the other hand, since the holes 42 of the pipe 40 are evenly provided up to the tip of the pipe 40, the secondary air does not flow into the oxidation catalyst 3
Go over the entire surface of 2.

FIG. 4 shows a modified embodiment of FIG. 1, in which the second oxygen concentration sensor 28 is attached to the case 34 from the same direction as the pipe 40. Further, the eaves 44 is mounted so as to surround the second oxygen concentration sensor 28. Fifth
The figure shows yet another embodiment, in which no eaves are provided. Instead, the second oxygen concentration sensor 28
The hole of the perforated protective cover 29 is provided only in a predetermined angle range facing the three-way catalyst 30, and the downstream side facing the pipe 40 has no hole. Similarly, the hole 42 of the pipe 40 is not provided in a portion overlapping with the second oxygen concentration sensor 28, so that the air from the pipe 40 is supplied to the second oxygen concentration sensor 28.
It prevents you from hitting directly.

[Effect of device]

As described above, according to the present invention, the dual-bed catalytic converter has a pipe for introducing secondary air that substantially crosses the space between the three-way catalyst and the oxidation catalyst in the radial direction. Is provided with an air outlet for blowing out secondary air in at least the exhaust upstream direction and the exhaust downstream direction in each axial portion, so that the secondary air is supplied to each portion of the aforementioned space. In particular, the secondary air blown out to the exhaust upstream side spreads in the direction perpendicular to the axis of the pipe due to the collision with the exhaust gas, and the secondary air blown out to the exhaust downstream side is oxidized together with the secondary air blown to the exhaust downstream side of the pipe. It is uniformly supplied to the entire catalyst, and high purification efficiency using the entire oxidation catalyst can be realized. Further, the oxygen concentration sensor is installed on the exhaust upstream side of the pipe in the aforementioned space, and the secondary air blown from the air outlet directly hits the oxygen concentration sensor between the oxygen concentration sensor and the pipe. Since the means for preventing this is provided, the oxygen concentration can be measured with high accuracy.

[Brief description of drawings]

1 is an enlarged cross-sectional view of an essential part of FIG. 2, FIG. 2 is a schematic view of an internal combustion engine having two oxygen concentration sensors, FIG. 3 is a cross-sectional view through the eaves and a pipe of FIG. 1, and FIG. Is a sectional view of another embodiment, and FIG. 5 is a sectional view of yet another embodiment. 14 ... Exhaust manifold, 20, 24 ... Exhaust pipe, 2
2 ... Dual-bed catalytic converter, 26, 28 ...
Oxygen concentration sensor, 34 ... Case, 40 ... Pipe, 4
4 ... eaves.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takatoshi Masui 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Toshiyasu Katsino 1 Toyota Town, Toyota City, Aichi Toyota Motor Co., Ltd. (72) Inventor Toshio Tanahashi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) References JP-A-52-19810 (JP, A) JP-A-57-126518 (JP, A) Actual Kaisho 59-116518 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A structure for mounting an oxygen concentration sensor on a dual-bed catalytic converter, which is provided in an exhaust system of an internal combustion engine and has a three-way catalyst and an oxidation catalyst arranged on the exhaust downstream side thereof. Has a pipe for introducing secondary air that substantially crosses the space between the three-way catalyst and the oxidation catalyst in the radial direction, and the pipe has at least exhaust gas upstream in each axial portion thereof. An air outlet for ejecting secondary air in the lateral direction and the exhaust downstream direction is provided, the oxygen concentration sensor is installed on the exhaust upstream side of the pipe in the space, and between the oxygen concentration sensor and the pipe. Is provided with means for preventing secondary air blown from the air outlet from directly hitting the oxygen concentration sensor. The mounting structure of the concentration sensor.