JPH051618Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a catalytic converter installed in an automobile exhaust system, and particularly aims to improve warm-up performance, downsize the entire exhaust system, and reduce back pressure. This invention relates to the structure of a catalytic converter.

[Prior Art] The exhaust system of an automobile is provided with a catalytic converter for purifying exhaust gas. Normally, this catalytic converter has a monolithic catalyst housed inside the converter case, and the exhaust gas inlet and outlet of the converter case are coaxial, meaning that a direct current of exhaust gas flows from the inlet of the converter case to the monolithic catalyst and the outlet. It is structured to flow.

In addition, as a structure aimed at downsizing the catalytic converter and reducing back pressure in the catalytic converter section, for example, as shown in Fig. 9, the converter case 1
The axes of the inlet section 2 and outlet section 3 of the exhaust gas are offset from each other, and the monolithic catalyst 4 is housed in between at an angle, so that the inlet area of the monolithic catalyst 4 can be widened relative to the flow of exhaust gas. Converters are also known (for example, Japanese Utility Model Application Publication No. 123820/1983).

[Problems to be solved by the invention] However, there are the following problems, especially in vehicles where the exhaust system from the engine cannot be very long, such as rear engine vehicles (for example, midship vehicles).

In the case of a rear engine vehicle, the arrangement of each component of the exhaust system is as shown in FIG. 10, for example. In the figure, 5 is an engine oil pan, 6 is a transmission, 7 is a drive shaft, 8 is an exhaust pipe, and 9 is a bellows tube provided for rolling absorption, etc. An L-shaped pipe 10, a catalytic converter 11, and a muffler 12 are arranged downstream of the bellows pipe 9.

In such an arrangement, the distance l from the engine to the catalytic converter 11 increases, the temperature of the exhaust gas decreases before reaching the catalyst in the catalytic converter 11, and the rise in catalyst temperature is slow, especially from a cold state. There was a problem that the catalyst performance tended to deteriorate during the warm-up process. For this problem,
If an attempt is made to place the catalytic converter 11 close to the engine, the position of the bellows tube 9 will be approximately determined based on rolling absorption performance, resulting in the catalytic converter 11 being too close to the engine, causing the catalyst to become hot. This causes new problems such as heat damage from the converter 11 to the engine (water temperature, oil temperature, etc.) and various devices around the engine.

In addition, the L-shaped pipe 10 on the upstream side of the catalytic converter 11
However, it is difficult to make a large bend due to manufacturing reasons or the back pressure of the exhaust gas, and there is also the problem that the L-shaped pipe 10 inevitably becomes large, making it difficult to downsize the entire exhaust system. In particular, the L-shaped pipe 10 as a bent pipe accounts for a large amount of pressure loss in the exhaust gas flow, so in order to reduce back pressure and improve engine output performance, the pressure loss of this L-shaped pipe 10 is important. This had become one of the major problems.

Although the pressure loss of the catalytic converter itself can be reduced by using the mixed flow type catalytic converter as described above, the above problem still remains as long as the L-shaped pipe 10 exists. Also, with the arrangement as shown in Figure 10,
If the catalytic converter 11 is replaced with a mixed flow type catalytic converter, there is a risk that the overall length of the exhaust system (vertical dimension in the figure) will actually increase.

The present invention focuses on the above-mentioned problems and brings the catalyst closer to the engine, improving the warm-up performance of the catalytic converter. It is an object of the present invention to provide a structure of a catalytic converter that can reduce the size of the system and significantly reduce the back pressure in the exhaust system.

[Means for Solving the Problems] The catalytic converter of the present invention that meets this objective is a catalytic converter in which a monolithic catalyst is housed in a converter case, in which the exhaust gas inlet and outlet of the converter case are connected to the inlet and the outlet. The monolithic catalyst is oriented in a direction in which the central axis of the outlet part forms an L-shape, and the central axis of the monolithic catalyst is inclined with respect to both the central axis of the inlet part and the central axis of the outlet part of the converter case. It is made up of things stored inside.

Preferably, the exhaust gas passage from the inlet of the converter case to the exhaust gas inflow surface of the monolithic catalyst has an enlarged chamber structure in which the cross-sectional area of the passage gradually increases.

[Function] In such a catalytic converter, since the converter case itself constitutes an L-shaped pipe, the 10th
There is no need to intentionally install an L-shaped pipe on the upstream side of the catalytic converter as shown in the figure, the catalyst of the catalytic converter is brought closer to the engine side, improving warm-up performance, and the catalyst is quickly heated to purify exhaust gas. In addition to improving performance, the overall length of the exhaust system is shortened and the entire exhaust system is miniaturized. The exhaust gas flowing in from the converter case inlet is changed in flow direction by the monolithic catalyst, which has a central axis that is inclined with respect to the central axis of the inlet, and then passes through the monolithic catalyst. The flow direction is changed by the outlet section having the flow direction and the flow is sent to the downstream side. Therefore, the flow direction of the exhaust gas can be gradually changed into an L-shape in the catalytic converter section, and since the flow path area is usually expanded in the monolith catalyst section, the flow direction can be changed to the desired flow direction with low pressure loss. This means that the back pressure in the entire exhaust system can be kept to a low level.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1 and 2 show a catalytic converter according to an embodiment of the present invention. In the figure, 2
1 is the engine oil pan, 22 is the exhaust pipe, 23 is the bellows pipe, 24 is the bent pipe, 2
5 represents a muffler, 26 represents a drive shaft, and a catalytic converter 27 is provided immediately downstream of the bellows tube 23.

The catalytic converter 27, as shown in FIG.
A converter case 28 houses a monolithic catalyst 29 in which the catalyst is supported on a ceramic or metal monolithic carrier. The exhaust gas inlet 30 and outlet 31 of the converter case 28 are arranged such that the central axis 32 of the inlet 30 and the central axis 33 of the outlet 31 form an L-shape.
The angle formed by the central axes 32 and 33 is not limited to 90 degrees. The monolithic catalyst 29 is placed within the converter case 28 with its center axis 34 extending toward the inlet portion 30.
The outlet portion 31 is housed at an angle with respect to the central axis 32 of the outlet portion 31 and with respect to the central axis 33 of the outlet portion 31. The exhaust gas passage 35 from the inlet portion 30 of the converter case 28 to the exhaust gas inflow surface 29a of the monolithic catalyst 29 has an enlarged chamber structure in which the cross-sectional area of the passage gradually increases toward the downstream side. This enlarged chamber 35 is provided with a plurality of introduction folds 36 that guide the exhaust gas in a direction in which the passage area increases. The central axis 34 of the monolithic catalyst 29 has any suitable angle with respect to the central axes 32 and 33 of the inlet section 30 and the outlet section 31, respectively.
The central axis 34 and the central axis 33 are gradually inclined (bent) in this order.

In the embodiment device configured as described above, since the converter case 28 itself constitutes a bent pipe similar to a conventional L-shaped pipe, the catalytic converter 28
7 There is no need to intentionally install an L-shaped pipe upstream,
It becomes possible to connect the catalytic converter 27 immediately downstream of the bellows tube 23. Therefore, the distance l ₁ (illustrated in FIG. 2) from the engine to the inlet of the catalytic converter 27 is the conventional distance l (illustrated in FIG. 10).
As a result, the catalytic converter 27 is brought closer to the engine, the temperature drop of the exhaust gas flowing into the catalytic converter 27 is suppressed, and the catalyst is heated in a short time, resulting in high exhaust gas purification even when it is cold. Performance can be obtained. In other words, in Figure 4, the first
The gas temperature at the exit of the catalyst and the second
As shown in the comparison with the gas temperature in the arrangement shown in the figure, with the device of the present invention, it is possible to quickly raise the temperature of the catalyst to a predetermined temperature in a short time after starting the engine. As shown in Figure 5, which shows the relationship between the exhaust gas temperature and the exhaust gas purification performance of the catalyst, the catalyst can only demonstrate its target purification performance above a certain temperature, so the short term By making it possible to raise the temperature of the catalyst in a timely manner, it becomes possible to quickly exhibit a predetermined purification performance even during a cold start.

Further, immediately downstream of the bellows tube 23, a conventional catalytic converter 4 is installed, for example, as shown in FIG.
It is also possible to connect the muffler 42 to the downstream side of the muffler 42 via the bent pipe 41, but this inevitably increases the overall length L of the exhaust system, and in rear engine cars etc. It becomes difficult to contain. In contrast, in the present invention, since the catalytic converter 27 itself functions as an L-shaped pipe as described above, the overall length _L1 of the exhaust system can be kept small. moreover,
As shown in FIG. 1, X, Y of the catalytic converter 27
The dimensions, especially the Y dimension, can be made smaller than normal L-shaped pipes, so the overall length of the exhaust system can be further reduced.
It is possible to keep L ₁ small.

Furthermore, the flow of the exhaust gas flowing in from the inlet portion 30 is expanded in the expansion chamber 35 and the flow velocity is reduced before flowing into the monolith catalyst 29, so that the pressure loss due to bending is suppressed to a small level and the flow between the monolith catalyst 29 and the monolith catalyst 29 is reduced. Provides sufficient contact time. In addition, the central axis 34 of the monolithic catalyst 29 is at an angle intermediate between the central axes 32 and 33 of the inlet section 30 and the outlet section 31, and the flow path of the exhaust gas is expanded and the direction of the exhaust gas is gradually changed within the converter case 28. Therefore, the pressure loss can be suppressed to be smaller than the bending pressure loss caused by the conventional L-shaped pipe. As a result, it becomes possible to efficiently suppress the back pressure of the entire exhaust system. In other words, as schematically shown in FIGS. 6 and 7, in the conventional structure, the exhaust gas flow 50 is sharply bent approximately at right angles at the L-shaped pipe portion, whereas in the present invention, the inflowing exhaust gas 51 The flow is first expanded (section 52), passes through the monolithic catalyst 29 at an angle between the inlet angle and the outlet angle, and is then discharged from the outlet, and the flow is gradually changed so that the back pressure is suppressed to low. .

Next, FIG. 8 shows a catalytic converter according to another embodiment of the present invention.

In this embodiment, the central axis 63 of the inlet portion 62 of the converter case 61 and the monolithic catalyst 64 are
are arranged so that the central axis 65 of the two are substantially on the same line. The central axis 63 of the inlet portion 62 and the central axis 67 of the outlet portion 66 are arranged in an L-shape, and the central axis 65 of the monolithic catalyst 64 is inclined with respect to both the central axis 63 and the central axis 67. A monolith catalyst 64 is arranged. Further, the enlarged chamber 68 at the entrance portion is not particularly provided with introduction folds. Other configurations are similar to those of the previous embodiment.

Even in such a catalytic converter 69, the catalytic converter 69 itself can perform the same function of converting the flow direction of exhaust gas as a conventional L-shaped pipe, while having smaller X and Y dimensions than a conventional L-shaped pipe. Furthermore, since the inlet portion 62 is arranged at a position corresponding to the center of the monolithic catalyst 64, the inflowing exhaust gas flows naturally and uniformly into the expansion chamber 68 without the need to provide an introduction fold or the like. It is possible to spread toward the inflow surface. Other operations are similar to those of the previous embodiment.

[Effects of the invention] As explained above, when using the catalytic converter of the invention, the following various effects can be obtained.

First, because the converter case itself has the same function of changing the exhaust gas flow direction as a conventional L-shaped pipe, the catalytic converter can be moved closer to the engine side even if the position of the bellows tube cannot be changed. In addition to speeding up the temperature rise and improving exhaust gas purification performance, especially during the warm-up process,
The entire exhaust system can be downsized. By downsizing the entire exhaust system, the degree of freedom in designing the exhaust system and mounting the catalytic converter can be improved. Furthermore, since the conventional L-shaped tube is not required, the number of parts can also be reduced.

In addition, since the flow of exhaust gas is gradually changed within the converter case, the pressure loss associated with changing the flow direction of exhaust gas into an L-shape is smaller than with a conventional L-shaped pipe, and the overall exhaust system is improved. Back pressure can be kept small. As a result, it is possible to improve the output performance of the engine.

[Brief explanation of the drawing]

FIG. 1 is an internal configuration diagram of a catalytic converter according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an exhaust system in which the catalytic converter of FIG. A schematic configuration diagram of the exhaust system when installed directly downstream of the pipe, Figure 4 is a diagram of the relationship between catalyst output gas temperature and time, Figure 5 is a diagram of the relationship between catalytic converter inlet gas temperature and catalyst purification performance, and Figure 6 is a diagram of the relationship between catalyst outlet gas temperature and catalyst purification performance. The figure is a conceptual diagram showing the flow of exhaust gas in a conventional L-shaped pipe section, Fig. 7 is a conceptual diagram showing the flow of exhaust gas in the catalytic converter of the present invention, and Fig. 8 is a conceptual diagram showing the flow of exhaust gas in the catalytic converter of the present invention. Internal configuration diagram of catalytic converter,
Figure 9 is a cross-sectional view of a conventional mixed flow converter.
Figure 0 is a schematic configuration diagram of a conventional exhaust system. 21... Engine oil pan, 22... Exhaust pipe, 23... Bellows pipe, 25...
Muffler, 27, 69...Catalytic converter, 2
8,61...Converter case, 29,64...
Monolith catalyst, 30, 62...Inlet part, 31, 6
6... Outlet part, 32, 63... Central axis of inlet part, 33, 67... Central axis of outlet part, 34, 6
5... Central axis of monolithic catalyst, 35, 68...
Expansion chamber, 36...Introduction fold.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a catalytic converter in which a monolithic catalyst is housed in a converter case, the exhaust gas inlet and outlet of the converter case are arranged such that the central axes of the inlet and outlet are L-shaped. A catalytic converter characterized in that the monolithic catalyst is housed in a converter case with the central axis of the monolithic catalyst inclined with respect to both the central axis of the inlet portion and the central axis of the outlet portion. (2) An exhaust gas passage from the inlet of the converter case to the exhaust gas inflow surface of the monolith catalyst,
The catalytic converter according to claim 1, which is a registered utility model, is configured as an enlarged chamber whose passage cross-sectional area gradually increases.