JP2000073755A - O2 sensor installing structure of catalyst converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an O2 sensor installing structure of catalyst converter which can maintain a high detecting accuracy by installing an O2 sensor near a catalyst carrier, and can remove the O2 sensor easily constantly when necessary. SOLUTION: In a catalyst converter to fix catalyst carriers 12 and 14 in a tubular housing 2 through holding mats 11 and 13, inner tubes 23 and 24 to pass the exhaust gas to the inner side are provided to at least a part in the area where no holding mats 11 and 13 in the tubular housing 2 are set, so as to make in a double structure by making the tubular housing 2 as the outer tube, and a pedestal 31 for O2 sensor installing is fixed to the tubular housing 2 at the part of the double structure, and an O2 sensor 30 is installed there.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to O ₂ sensor mounting structure for a catalytic converter having an O ₂ sensor.

[0002]

O ₂ sensor to be attached to the catalytic converter catalyst support is built into the Related Art cylindrical housing is supported through the housing for outputting the detected detection signal of oxygen concentration in the housing.

FIG. 4 shows a conventional general example. The holding mats 02a and 03a are respectively housed in a cylindrical housing 01.
, Two catalyst carriers 02 and 03 are arranged in series.
The pedestal 04 is welded to the housing 01 between the two catalyst carriers 02 and 03, and the O ₂ sensor 05 penetrates and is screwed to the pedestal 04 and fixedly supported.

Further, there is an example in which an exhaust pipe is used as a double pipe instead of a catalytic converter and an O ₂ sensor is attached to the double pipe (Japanese Patent Laid-Open No. 8-189351). A nipple for attaching an O ₂ sensor is fitted into a cylindrical wall formed by projecting a part of the inner tube of the double tube toward the outer tube.

[0005]

In the case of the catalytic converter shown in FIG. 4, the temperature of the housing 01 rises because the housing 01 is in direct contact with the high-temperature exhaust gas. Distortion easily occurs.

When the pedestal is distorted, it becomes difficult to remove the O ₂ sensor 05, and the operation becomes troublesome. Also O ₂ sensor
If the 05 cannot be removed from the pedestal 04, the entire catalytic converter must be replaced, which is not economical.

Similarly, in the example described in the above-mentioned publication, the nipple is fitted into and tightly adhered to the inner pipe, which comes into contact with the exhaust gas and becomes high in temperature, so that the temperature of the nipple also rises and thermal distortion is likely to occur. Therefore, the O ₂ sensor fixed to the nipple is difficult to remove.

[0008] The detection of the oxygen concentration by the O ₂ sensor is as follows.
It is desirable to perform the detection near the catalyst carrier in order to increase the detection accuracy. However, in the example described in the above-mentioned publication, it is arranged in the exhaust pipe, so that the detection accuracy cannot be expected to be improved much.

[0009] The present invention has been made in view of the foregoing, processing and its object is to maintain high detection precision mounting the O ₂ sensor in the vicinity catalyst support, whenever necessary O ₂
Removing the sensor easily lies in subjecting the O ₂ sensor mounting structure of the catalytic converter that can.

[0010]

In order to achieve the above object, the present invention provides a catalytic converter for fixing a catalyst carrier via a holding mat in a cylindrical housing. At least a part of the area where the holding mat is not installed is provided with an inner cylinder for allowing exhaust gas to pass inside, so that the cylindrical housing has an outer cylinder and has a double structure. _Two
Was O ₂ sensor mounting structure for a catalytic converter fitted with O ₂ sensor by fixing the pedestal for sensor mounting.

A pedestal is fixed to a double structure portion having an inner cylinder of the cylindrical housing, and an O ₂ sensor is mounted on the pedestal. The pedestal is fixed to a cylindrical housing corresponding to the outer cylinder of the double structure part, and the cylindrical housing is separated from the inner cylinder that directly contacts high-temperature exhaust gas with an air insulation layer in between,
Since the influence of heat is alleviated and the temperature rise is suppressed, the pedestal is not distorted by heat.

Therefore, the O ₂ sensor becomes difficult to remove from the pedestal due to the thermal distortion of the pedestal, and the work becomes troublesome.
Quite possible to avoid a problem such as replacement of the entire catalytic converter can no longer be detached, it can be easily removed the O ₂ sensor at any time when necessary.

[0013] Since the O ₂ sensor is mounted on the cylindrical housing of the catalytic converter, it is located near the catalyst carrier, and high detection accuracy can be ensured. By providing the inner cylinder, it is possible to suppress the flow of the exhaust gas to the mat, so that it is possible to suppress the displacement of the holding mat and the scattering of the mat fiber.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to FIG. In the catalytic converter 1 of the present embodiment, the cylindrical housing 2 has a cylindrical outer cylinder 3.
And a conical front end cone 4 welded to the front opening end and integrally connected thereto, and a conical rear end cone 5 welded to the rear opening end and integrally connected together. .

An inflow port 6 is formed at a tapered end in front of the front cone 4, and an outflow port 7 is formed at a tapered end behind the rear cone 5. The outer cylinder 3 has a reduced diameter portion 3a confined at the center, and the outer cylinder 3 has a reduced diameter portion 3a inside.
Before and after, monolith-type catalyst carriers 12, 14 are held via holding mats 11, 13, respectively.

The holding mats 11 and 13 are formed into a mat shape by adding, for example, an organic binder mainly containing ceramic fiber and vermiculite and mainly containing acrylic acid. The catalyst carriers 12, 14 having a columnar shape on the inner side are held at a pressure.

The inner cylinder 23 and the front cone inner 24 are provided inside the reduced diameter portion 3a of the outer cylinder 3 where the holding mats 11 and 13 of the cylindrical housing 2 are not installed and the front cone 4, respectively, to form a double structure. are doing.

The inner cylinder 23 is formed in a flat cylindrical shape having a diameter slightly smaller than the reduced diameter portion 3a of the outer cylinder 3, and has an air heat insulating layer between the inner cylinder 23 and the reduced diameter portion 3a. The front end cone inner 24 is formed in a conical shape along the inner peripheral surface of the front end cone 4 via an air heat insulating layer.

An O ₂ sensor 30 is attached to a portion forming a double structure by the reduced diameter portion 3 a of the outer cylinder 3 and the inner cylinder 23. A pedestal 31 for screwing and supporting the O ₂ sensor 30 is welded to the reduced diameter portion 3a of the outer cylinder 3 from outside, and the O ₂ sensor 30 is screwed into a female screw engraved on the inner periphery of the pedestal 31, Reduced diameter portion 3a and inner cylinder 23
And the sensitive part at the tip of the O ₂ sensor 30 is projected into the inner cylinder 23.

The present catalytic converter 1 has the above-described structure. Exhaust gas is guided to the exhaust pipe, enters through the inlet 6, passes through the front end cone inner 24, passes through the catalyst carriers 12, 14, and is purified. And exits from outlet 7. Since the O ₂ sensor 30 is provided in the catalytic converter 1 and is disposed close to the catalyst carriers 12 and 14, the oxygen concentration detection accuracy is high.

The portion other than the rear end cone 5 of the cylindrical housing 2 has a double structure by an inner cylinder 23 and a front end cone inner 24 except for a region where the catalyst carriers 12 and 14 are held.
Since there is no direct exposure to the high-temperature exhaust gas through the air insulation layer, the influence of heat is reduced.

[0022] Thus since no cause distortion pedestal 31 fixed to the reduced diameter portion 3a of the outer cylinder 3a of the cylindrical housing 2 is also due to heat, O ₂ sensor 30 which is screwed to the pedestal 31 at any time when necessary It can be easily removed and newly installed.

For example, when the main body of the O ₂ sensor 30 is damaged due to a flying stone, or the wiring is broken, and the O ₂ sensor 30 needs to be replaced, or during other maintenance, the pedestal 31 is thermally strained and screwed. It is possible to avoid that it is difficult to remove the O ₂ sensor. If the O ₂ sensor 30 can not be removed is uneconomical must replace the entire catalytic converter 1.

Further, etc. If the catalyst support strike the catalytic converter 1 on the convex portion of the melting and road of the catalyst carrier by an engine misfire is damaged, it will replace the catalytic converter 1, O ₂ sensor 30 is again it can be used, O ₂ sensor 30 to achieve this it is important to be able to be easily removed.

As described above, the catalytic converter 1 has a double structure at a required portion and the influence of the heat of the exhaust gas on the outer cylinder 3 is small. Therefore, the thermal expansion of the outer cylinder 3 is small, the surface pressure is maintained, and the holding mat is maintained. 11 and 13 can always hold the catalyst carriers 12 and 14 reliably.

The front end cone inner 24 has an inlet 6 at the front end, the diameter of which gradually increases, and the diameter of the rear end opening is substantially equal to the outer diameter of the catalyst carrier 12, and the rear end opening of the front end cone inner 24 is Since the front end face of the catalyst carrier 12 is opposed to the front end surface with a slight gap, almost all of the exhaust gas guided to the front end cone inner 24 flows into the catalyst carrier 12, and the flow velocity is supplied to the holding mat 11 on the outer periphery of the catalyst carrier 12. Only a very small amount of reduced exhaust gas is reached.

As described above, since the holding mat 11 does not directly receive the high-temperature exhaust gas and the holding mat 11 is reliably held by the surface pressure of the outer cylinder 3 which does not thermally expand as described above, the holding mat 11 There is no problem of scattering.

Since the surface pressure of the outer cylinder 3 can be kept substantially constant, it is not necessary to set the maximum surface pressure at normal temperature to be high, so that the possibility of damaging a low-strength catalyst carrier is low. By reducing the thickness of the carrier wall, pressure loss and weight can be reduced.

Further, the double structure of the catalytic converter 1 allows the catalytic converter 1 to be arranged at a position closer to the engine without changing the temperature of the cylindrical housing 2, and the purification performance can be improved by early activation of the catalyst. it can. In addition, it is possible to set the air-fuel ratio control in which the temperature of the exhaust gas is increased without changing the temperature of the cylindrical housing 2, and it is possible to improve the fuel efficiency by approaching the stoichiometric air-fuel ratio even during high-speed operation.

Next, another embodiment will be described with reference to FIG. The catalytic converter 50 of the present embodiment has exactly the same structure except that the catalytic converter 50 is different from the catalytic converter 1 in two points, and the same members are denoted by the same reference numerals.

The present catalytic converter 50 has a rear end cone inner 25 inside the rear end cone 5 to form a double structure.
The difference from the catalytic converter 1 is that the O ₂ sensor 51 is provided on the rear end cone 5 without being provided on the outer cylinder 3.

[0032] In screwed to the pedestal 52 which is fixed to the outer surface of the rear end cone 5 screwed O ₂ sensor 51, the sensitive part of the tip of the rear end cone 5 and the rear end Kon'in'na 25 through the O ₂ sensor 51 Are projected into the inner cylinder 23.

The catalytic converter 50 includes a cylindrical housing 2
Except for the region holding the catalyst carriers 12 and 14, the entire structure has a double structure, and an O ₂ sensor 51 is attached to the double structure of the rear end cone 5 and the rear end cone inner 25.

Accordingly, since the rear end cone 5 is less affected by the heat of the exhaust gas and the pedestal 52 fixed to the rear end cone 5 does not generate distortion due to heat, the O ₂ sensor 51 screwed to the pedestal 52 is necessary. It can be easily removed at any time.

As in the present catalytic converter 50, an O ₂ sensor
51 is disposed in the rear end cone 5 downstream of the catalyst carrier 14, or the O ₂ sensor 30 is connected to the catalyst carrier 12 as in the catalytic converter 1.
By arranging between the catalyst carrier 14 and the catalyst carrier 14, it is possible to detect the deterioration of the catalyst for detecting the oxygen storage capacity of the catalyst.

A catalytic converter 60 according to still another embodiment is shown and described in FIG. The present catalytic converter
60 is another O 2 in the catalytic converter 50 shown in FIG.
_{The two} sensors 61 are attached to the front end cone 4, and the other configuration is the same as that of the catalytic converter 50, and the same members use the same reference numerals.

[0037] In screwed screwed O ₂ sensor 61 to the pedestal 62 which is fixed to the outer surface of the front cone 4, the front end of the sensitive part of the tip of the O ₂ sensor 61 through the front cone 4 and the front end Kon'in'na 24 Kon'in'na It protrudes into 24. O ₂ sensor
Mounting structure 61 is the same as the O ₂ sensor 51, the pedestal 62 does not cause thermal strain, O ₂ sensor screwed to the pedestal 62
The 51 can be easily removed whenever needed and can be easily installed.

In the above embodiment, the cylindrical housing 2
Is a cylindrical outer cylinder 3 and a conical front end cone 4,
Although it is constituted by the rear end cone 5, a structure called a so-called clamshell in which the cylindrical housing is divided in half by a plane including the central axis and the two are united can be applied.

[Brief description of the drawings]

FIG. 1 is a sectional view of a catalytic converter according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a catalytic converter according to another embodiment.

FIG. 3 is a cross-sectional view of a catalytic converter according to another embodiment.

FIG. 4 is a sectional view of a conventional catalytic converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Catalytic converter, 2 ... Cylindrical housing, 3 ... Outer cylinder,
4 front cone, 5 rear cone, 6 inlet, 7 outlet, 11 holding mat, 12 catalyst carrier, 13 holding mat, 14 catalyst carrier, 24 front cone inner, 25 rear end Kon'in'na, 30 ... O ₂ sensor, 31 ... base, 50 ... catalytic converter, 51 ... O ₂ sensor, 52 ... base, 60 ... catalytic converter, 61 ... O ₂ sensor, 62 ... base.

Claims (1)

[Claims] 1. A cylindrical housing having a holding mat interposed therebetween.
In a catalytic converter for fixing a catalyst carrier, the holding mat in the cylindrical housing is not installed.
To allow exhaust gas to pass through at least part of the
A double structure in which a cylinder is provided and the cylindrical housing is an outer cylinder;
The cylindrical housing of the double structure has O_TwoSensor mounting
Fix the pedestal for O _TwoCharacterized by attaching a sensor
O of the catalytic converter_TwoSensor mounting structure.