JP6622860B1 - Catalytic converter - Google Patents

Abstract

A catalytic converter having excellent holding power is provided. A first catalyst carrier and a second catalyst carrier are provided in a cylindrical casing, and a first catalyst carrier is provided between the first catalyst carrier and the second catalyst carrier and the casing. A holding member is provided so as to surround the outer periphery of the second catalyst carrier, and an air-fuel ratio is provided between the first catalyst carrier and the second catalyst carrier via a mounting boss welded to an outer surface of the casing. A catalytic converter in which a sensor is disposed, wherein the outer diameter of the catalytic converter is formed substantially uniformly in the exhaust flow path direction of the casing, and the outer diameter of the catalytic converter is arranged upstream and downstream in the exhaust flow path direction of the casing, respectively. The pipes are fixed to each other by full circumference welding, and when the position where the mounting boss is welded is set to 0 ° on the outer circumference of the casing when viewed from the front in the exhaust flow direction of the casing, each of the full circumference welding is performed. End from 345 ° to 15 ° is a catalytic converter provided at the position of °. [Selection diagram] FIG.

Description

  The present invention relates to a catalytic converter.

  A catalytic converter that purifies gas components such as HC, CO, and NOx contained in the exhaust or collects and purifies particulate matter (hereinafter also referred to as “PM”) in the exhaust in the exhaust passage of the engine Is provided. This catalytic converter is configured by housing a columnar catalyst carrier having a function of purifying exhaust gas in a tubular casing that is a part of an exhaust flow path.

  Incidentally, in the catalytic converter, an air-fuel ratio sensor for measuring the oxygen concentration in the exhaust gas is introduced for the purpose of controlling the air-fuel ratio in the engine. For example, the air-fuel ratio sensor is introduced by welding the air-fuel ratio sensor mounting boss while penetrating the casing of the catalytic converter (see, for example, Patent Document 1).

  In Patent Document 1, in a two-bed converter in which two catalyst carriers are accommodated in a tubular casing, the casing is reduced in diameter at an intermediate position between the two catalyst carriers, and a part of the reduced diameter cylindrical portion is partially flat. And a structure in which an air-fuel ratio sensor mounting boss is introduced in the plane portion is disclosed. In this catalytic converter, after forming the reduced diameter portion (MID molding), the catalyst carrier is inserted from both sides, and the entire diameter is once again reduced (canning), thereby giving a holding force to the casing.

JP 2012-117443 A

  However, in the structure of Patent Document 1, there is a concern that cracks are likely to occur due to prolonged production due to a plurality of diameter reduction steps and repeated stress applied to the diameter reduction portion.

  By the way, the introduction of the air-fuel ratio sensor mounting boss into the casing is usually performed by welding to a mounting portion in the casing after canning. At this time, since distortion due to thermal expansion and contraction occurs in the surrounding weld heat affected zone, the casing is lifted from the catalyst carrier held inside, and the surface pressure supporting the catalyst carrier is lowered. .

  The present invention has been made in view of the above, and in a two-bed catalytic converter without an MID molding process, by appropriately setting the welding position between the casing and the upstream / downstream piping, the distortion of the heat-affected zone in welding is reduced. It is an object of the present invention to provide a catalytic converter having an excellent holding force by offsetting with a strain at the time of fitting or butt welding between a casing and an upstream / downstream pipe.

  (1) In the present invention, a first catalyst carrier (for example, a later-described honeycomb carrier 2a) and a second catalyst carrier (for example, a later-described honeycomb carrier 2b) are disposed in a cylindrical casing (for example, a later-described casing 4). And a holding member (for example, between the first catalyst carrier and the second catalyst carrier and the casing so as to surround the outer periphery of the first catalyst carrier and the second catalyst carrier) A mat 3) described later is provided, and a mounting boss (for example, a mounting boss 6 described later) welded to the outer surface of the casing is provided between the first catalyst carrier and the second catalyst carrier. A catalytic converter (for example, a later-described catalytic converter 1) in which an air-fuel ratio sensor (for example, an after-mentioned air-fuel ratio sensor 7) is disposed, the outer diameter of the catalytic converter being the exhaust of the casing Channel direction (for example, The casing and the pipes respectively disposed upstream and downstream of the casing in the direction of the exhaust flow path are fixed to each other by circumferential welding, When the position where the mounting boss is welded is 0 ° on the outer periphery of the casing as viewed from the front of the casing in the exhaust flow path direction, the respective starting points of the all-around welding are provided at positions of 345 ° to 15 °. A catalytic converter is provided.

  (2) In the invention of (1), the holding member has an abutment portion (for example, a later-described abutment portion 31) whose both ends face each other on the outer periphery of the casing in a front view of the casing in the exhaust flow path direction. When the position where the mounting boss is welded is 0 °, the mounting boss may be provided at a position of 15 ° to 105 ° or 255 ° to 345 °.

  According to the invention of (1), the strain in the vicinity of the starting point of the all-around welding and the spread of the case end caused by the boss mounting portion welding are offset. For this reason, the casing is less lifted and the holding force is improved. Therefore, according to the invention of (1), a catalytic converter having a holding power superior to that of the prior art can be provided.

  According to the invention of (2), the surface pressure is made uniform by positioning the mat joint at the expansion strain point immediately before the end of the entire circumference welding. Therefore, the reduction of the surface pressure is further suppressed, and the holding force is further improved. Therefore, according to the invention of (2), a catalytic converter having further excellent holding power can be provided.

It is a figure which shows the catalytic converter which concerns on one Embodiment of this invention. It is sectional drawing which shows the internal structure of the casing which concerns on the catalytic converter of the said embodiment. It is an exhaust flow path direction front view of the casing which concerns on the catalytic converter of the said embodiment. It is an expanded view which shows distribution of the expansion part in the side view of the casing which concerns on the catalytic converter of the said embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall view of a catalytic converter 1 according to an embodiment of the present invention. The catalytic converter 1 is disposed in an exhaust passage of an engine (not shown), and purifies exhaust discharged from the engine under the action of an exhaust purification catalyst. More specifically, for example, the catalytic converter 1 is installed vertically in the vehicle mounting posture in a section called “directly under the engine” in the exhaust passage of the engine (for example, in a section in an engine room in which the engine is stored), that is, The exhaust passage direction 1a and the vertical direction are provided so as to be substantially parallel.

  Here, the exhaust passage direction 1a is a central axis direction of a cylindrical casing 4 described later. That is, the exhaust flow path direction 1 a means the exhaust flow path direction (the direction in which the exhaust flows) in the casing 4.

  The catalytic converter 1 includes a columnar honeycomb carrier 2, a strip-like mat 3 wound around the honeycomb carrier 2, and a tubular casing 4 that accommodates the honeycomb carrier 2 around which the mat 3 is wound.

  The honeycomb carrier 2 has a columnar shape including a plurality of cells 21 extending along the exhaust flow passage direction 1a from the inflow side end 23 to the outflow side end 24, and partition walls 22 that partition the cells 21. Each cell 21 is a flow-through type honeycomb structure in which both ends 23 and 24 are not sealed. The partition wall 22 carries an exhaust purification catalyst. Exhaust gas flowing into each cell 21 from the inflow side end 23 is purified under the action of the exhaust purification catalyst in the process of flowing in each cell 21 along the exhaust flow path direction 1a.

  The mat 3 has a strip shape and includes a fiber material and an inorganic binder that connects the fiber materials. For the fiber material, inorganic fibers having heat resistance such as alumina fiber, mullite fiber, silica fiber, alumina silica fiber, and ceramic glass fiber are used. Moreover, what contains an alumina particle is used for an inorganic binder, for example. The mat 3 is wound along the outer peripheral surface of the columnar honeycomb carrier 2. Since the surface pressure in the vicinity of the mating portion 3a, that is, the mat end portion is increased after being wound, by setting this at a position corresponding to the expansion portion (expansion immediately before the end of all-around welding) 4b, the surface pressure due to expansion is increased. It can compensate for the decline and improve the holding power.

  FIG. 2 is a cross-sectional view showing the internal structure of the casing 4 according to the catalytic converter 1 of the present embodiment. The casing 4 has a cylindrical shape, and the outer diameter is substantially uniform in the direction of the exhaust flow path. The honeycomb carrier 2 around which the mat 3 is wound as described above is accommodated therein. The casing 4 holds the two honeycomb carriers 2 around which the mat 3 is wound, and has a hole 5 for attaching an air-fuel ratio sensor mounting boss at an intermediate position thereof. That is, the two honeycomb carriers 2 are held in the casing 4 at a predetermined interval, and have a space in which the air-fuel ratio sensor 7 is inserted therebetween.

  Note that, when the honeycomb carrier 2 is inserted into the casing 4, the inner diameter of the casing 4 is slightly larger than the outer diameter of the mat 3 in a state of being wound around the honeycomb carrier 2, but after the honeycomb carrier 2 is inserted, the casing 4 The honeycomb carrier 2 is held in the casing 4 by reducing the diameter. Specifically, the mat 3 is compressed from the outer peripheral direction by the casing 4 having a reduced diameter, and the surface pressure by the mat 3 acts on the outer peripheral surface of the honeycomb carrier 2, whereby the honeycomb carrier 2 is positioned at a predetermined position inside the casing 4. Is held in.

  The hole 5 is a hole provided on the outer peripheral side surface of the casing 4, and the air-fuel ratio sensor 7 is inserted into the catalytic converter 1 through the hole 5. An air-fuel ratio sensor mounting boss 6 is bonded to the hole 5 by welding as a jig for introducing the air-fuel ratio sensor 7 into the casing 4.

  The air-fuel ratio sensor mounting boss 6 is a jig for inserting the air-fuel ratio sensor 7 into the casing 4. The shape of the air-fuel ratio sensor mounting boss 6 is not particularly limited, but it is preferable that the air-fuel ratio sensor mounting boss 6 has a cylindrical portion of a size that fits into the hole 5 because welding can be easily performed.

  The air-fuel ratio sensor 7 is a sensor that detects and measures the air-fuel ratio in the exhaust gas. The air-fuel ratio sensor 7 is likely to need maintenance and replacement due to accumulation or deterioration of soot in the exhaust gas. Therefore, it is preferable that the air-fuel ratio sensor mounting boss 6 and the air-fuel ratio sensor 7 are threaded so as to be fitted to each other so that the air-fuel ratio sensor 7 can be easily removed.

FIG. 3 is a front view of the exhaust flow passage direction 1a of the casing 4 according to the catalytic converter 1 of the present embodiment.
The catalytic converter 1 is connected to upstream and downstream piping in the exhaust system, and the connecting portion is fitted or butt welded around the entire circumference of the cylinder. Here, in the front view of the catalytic converter 1 in the direction of the exhaust flow path, when the position where the mounting boss is welded is set to 0 °, the starting point of each circumferential welding is 345 ° (−15 °) to 15 °. Provided in position. Accordingly, by contracting the welding heat affected zone at the starting point of the all-around welding, the expansion of the expansion portion 4a generated during welding of the mounting boss can be offset, and the reduction of the surface pressure due to the rising of the casing can be alleviated. .

  Furthermore, in the catalytic converter 1 of the present invention, the position at which the joint 3a facing both ends of the mat 3 is welded to the mounting boss at the outer periphery of the casing when viewed from the front of the exhaust passage direction 1a is 0 °. Sometimes it is preferably located from 15 ° to 105 ° or 255 ° (−105 °) to 345 ° (−15 °). Accordingly, the mat joint portion 3a where the surface pressure is increased is positioned with respect to the expansion strain portion 4b immediately before the end point of the entire circumference welding, so that the decrease in the surface pressure is compensated and the holding force is improved.

  Next, a method for manufacturing the catalytic converter 1 of this embodiment will be briefly described.

  Two honeycomb carriers 2 each having a mat 3 wound around the outer periphery thereof are inserted into a cylindrical casing 4 and held in predetermined positions. At this time, a space in which an air-fuel ratio sensor can be inserted exists between the two honeycomb carriers 2. A hole 5 for attaching an air-fuel ratio sensor mounting boss is formed in the casing 4 in advance, and the holding position is determined so that the hole 5 comes to an intermediate position between the two honeycomb carriers 2.

  The entire cylindrical casing 4 holding the two honeycomb carriers 2 is compressed in the radial direction of the cylinder by a dedicated press from the outside to reduce the diameter. Thereby, the mat 3 is compressed in the casing 4, and the surface pressure from the mat 3 is applied to the two honeycomb carriers 2, whereby a holding force is applied to the casing 4.

  FIG. 4 is a development view showing the distribution of the expansion portion in a side view of the casing 4 according to the catalytic converter 1 of the present embodiment. In FIG. 4, (a) represents the cylindrical casing 4 in front view of the exhaust passage direction 1a, and the numbers around the circle correspond to the four directions on the cylindrical side surface. The four rectangles described in (b) are side views from the side direction corresponding to the numbers. In addition, the upward direction in each side view corresponds to the front side of the cylindrical surface shown in FIG.

  In this embodiment, the air-fuel ratio sensor mounting boss 6 is attached to the hole 5 of the casing 4 subjected to the diameter reduction process by welding. At the time of welding, due to the influence of the welding heat of the air-fuel ratio sensor mounting boss 6, distortion occurs such that the outer peripheral end of the casing 4 swells outward in the mounting boss mounting side direction (the expanding portion 4 a shown in FIG. 4). ).

  In this embodiment, the surface pressure is measured using a tactile sensor. The surface pressure can be measured by winding the tactile sensor around the honeycomb carrier 2, and then winding the mat 3 and performing canning.

  In the present embodiment, the casing 4 welded to the mounting boss is connected to the upstream and downstream piping in the exhaust system. This connection is performed by fitting the casing 4 and the pipe all around or by butt welding. At this time, since it is all-around welding, the start point and the end point are almost the same position. This point is defined as a welding start point 8. It is known that when fitting or butt welding is performed, particularly in the vicinity of the welding start point, the weld heat affected zone is cooled over time after welding, and as a result, the base material contracts more than before welding. Therefore, by appropriately setting the welding start point 8, it is possible to cancel the expansion of the weld heat affected zone that has occurred during boss welding and to mitigate the reduction in the surface pressure at the expanded portion 4a.

  On the other hand, as a result of the escape of the base metal along the welding direction 8a along with the all-around welding, a distortion that swells outward occurs in the portion immediately before the all-around welding end point. By appropriately setting the position of the mat joint portion 3a where the surface pressure increases with respect to the strained portion 4b, the decrease in the surface pressure can be alleviated and the holding force can be improved.

  The effects of the catalytic converter according to the present embodiment described above are summarized as follows.

  The catalytic converter 1 according to the present embodiment accommodates two cylindrical honeycomb carriers 2, a strip-like mat 3 wound around the two honeycomb carriers 2, and two honeycomb carriers 2 around which the mat 3 is wound. A tubular casing 4. In the casing 4, an air-fuel ratio sensor mounting boss 6 is welded to a tube wall at an intermediate position between the two honeycomb carriers accommodated therein, and an air-fuel ratio sensor 7 is mounted via the air-fuel ratio sensor mounting boss 6. The

  The catalytic converter 1 is connected to upstream and downstream piping in the exhaust system, and the connecting portion is fitted or butt welded to the entire circumference. In the exhaust flow passage direction 1a front view of the catalytic converter 1, when the position where the mounting boss is welded is 0 °, the welding start point 8 of each circumferential welding is 345 ° (−15 °) to 15 °. It is provided in the position.

  Thereby, the expansion | swelling at the time of welding of the air-fuel ratio sensor mounting | wearing boss | hub 6 produced in the cylindrical edge part of the casing 4 is relieve | moderated by the shrinkage | contraction effect | action in the vicinity of the starting point at the time of fitting with upstream and downstream piping or butt welding. Therefore, a decrease in the surface pressure applied by the mat 3 to the honeycomb carrier 2 in the expansion portion 4a is suppressed, and the holding power of the honeycomb carrier 2 in the casing 4 is improved.

  Further, in the catalytic converter 1, the abutment portion 3a where both ends of the mat 3 face each other is 15 when the position where the mounting boss is welded is 0 ° on the outer periphery of the casing 4 in the front view of the exhaust passage direction 1a. It is located in the range of ° to 105 ° or 255 ° (−105 °) to 345 ° (−15 °).

  As a result, the mat joint portion where the surface pressure is likely to increase is positioned in the portion that expands at the time of welding immediately before the end point of the entire circumference welding, so that the surface pressure is made uniform and the holding force is further improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. Within the scope of the gist of the present invention, the detailed configuration may be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Catalytic converter 1a Exhaust flow path direction 2 Honeycomb carrier 3 Mat 3a Joint part 4 Casing 4a, 4b Expansion part 5 Hole part 6 Air-fuel ratio sensor mounting boss 7 Air-fuel ratio sensor 8 Welding start point 11 Upstream piping 12 Downstream piping

Claims (2)

A first catalyst carrier and a second catalyst carrier are disposed in a cylindrical casing;
A holding member is provided between the first catalyst carrier and the second catalyst carrier and the casing so as to surround outer peripheries of the first catalyst carrier and the second catalyst carrier,
A catalytic converter in which an air-fuel ratio sensor is disposed between the first catalyst carrier and the second catalyst carrier via a mounting boss welded to the outer surface of the casing;
The outer diameter of the catalytic converter is formed substantially uniformly in the exhaust flow path direction of the casing,
The casing and the pipes respectively arranged upstream and downstream in the exhaust flow path direction of the casing are fixed to each other by full circumference welding,
When the position where the mounting boss is welded is 0 ° on the outer periphery of the casing in a front view of the casing in the exhaust flow path direction, each end point of the all-around welding is at a position of 345 ° to 15 °. A catalytic converter provided.   The holding member has an abutting portion facing both ends at 15 ° to 105 ° when the position where the mounting boss is welded is 0 ° on the outer periphery of the casing in a front view of the casing in the exhaust flow path direction. The catalytic converter according to claim 1, wherein the catalytic converter is provided at a position of ° or 255 ° to 345 °.

Images