JPH068722U - Catalytic device for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Object] In a catalyst device installed in an exhaust passage of an internal combustion engine, in order to improve exhaust emission at the time of warm-up, early activation of the catalyst is realized with an extremely simple configuration. [Structure] The catalyst 8 is divided on a plane in which the volume of the upstream side 8a is smaller than the volume of the downstream side 8b and is substantially perpendicular to the flow of exhaust gas, and a predetermined heat insulating space 9 is provided between them in the same case 7. Install in series with interposition.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a catalyst device for an internal combustion engine.

[0002]

[Prior art]

 It is well known to provide a catalyst device in the exhaust passage as one of the measures for exhaust gas of an internal combustion engine. Of these, in order to improve the exhaust emission during warm-up, a bypass passage bypassing the exhaust passage is formed on the upstream side of the main catalyst, a sub catalyst with a small heat capacity is inserted in the middle of the passage, and the exhaust passage and the bypass passage are bypassed. A switching valve that selectively opens and closes the passage is provided, and when the main catalyst temperature is below a specified value (activation temperature), exhaust gas is guided to the bypass passage through the switching valve, and flows from the sub catalyst to the downstream side through the main catalyst. In addition, a throttle is provided in front of the catalyst in the exhaust passage so that when the catalyst temperature is low, the throttle is effective only in the center of the catalyst, and when the catalyst temperature rises, the throttle is loosened to reduce the entire catalyst. It has been proposed that the exhaust gas be made to flow through (Japanese Utility Model Publication No. 63-87212 and Japanese Utility Model Publication No. 123932).

Although it is not a technical content for promoting the early activation of the catalyst, two catalysts are arranged in series in the case through a predetermined space in order to absorb the thermal expansion of the catalyst carrier, and Some catalysts are fixed to the case at the outer circumferences of the end portions opposite to the facing end surfaces (Japanese Utility Model Laid-Open No. 2-85815 and Japanese Utility Model Laid-Open No. 2-83320).

[0004]

[Problems to be solved by the device]

 However, in such a conventional example (measures for exhaust during warm-up), in the former case, many parts are attached to the exhaust passage such as the bypass passage and the sub-catalyst, and in the latter case, the catalyst is attached. It is technically difficult to configure the front throttle to function well, and in any case, the structure including the switching valve or the throttle control means becomes considerably complicated, resulting in a significant increase in cost. was there.

The present invention aims to realize early activation of a catalyst with an extremely simple structure in order to improve exhaust emission during warm-up.

[0006]

[Means for Solving the Problems]

 Therefore, in the present invention, in the catalyst device installed in the exhaust passage of the internal combustion engine, the catalyst is divided on a plane whose volume on the upstream side is smaller than that on the downstream side and which is substantially perpendicular to the flow of exhaust gas. These are housed in series in the same case with a predetermined adiabatic space interposed therebetween.

[0007]

[Action]

 According to this, the upstream catalyst portion is quickly warmed by the heat quantity of the exhaust gas, and the heat insulating space suppresses heat transfer to the downstream catalyst portion, so that the activation temperature is raised in a short time. Since warm-up is performed by idle rotation, the amount of exhaust is small, and therefore a sufficient purification rate can be obtained even if the catalyst volume (capacity) is small. Further, when the upstream side is activated, the exhaust gas temperature to the downstream side becomes high due to the reaction heat of the catalyst, so that the heating of the downstream side is promoted and the temperature rise of the entire catalyst also becomes faster.

[0008]

【Example】

 In FIG. 1, reference numeral 1 is an engine using methanol as a fuel, and an injector 2 for injecting fuel near the top dead center of a compression stroke and an ignition plug 3 for assisting ignition of fuel spray are provided in a combustion chamber of the engine.

A catalyst device 6 that oxidizes unburned components (aldehyde and unburned methanol) in the exhaust gas is provided in the engine exhaust passage 4 immediately upstream of the muffler 5. As shown in FIGS. 2 and 3, the catalyst device 6 is one in which two monolith catalysts 8 are installed in parallel in an elliptic cylinder type case 7. Each catalyst 8 has a smaller volume on the upstream side than the volume on the downstream side. , And it is divided into two in a plane perpendicular to the flow of exhaust gas.

The upstream side 8a and the downstream side 8b of each catalyst 8 are arranged in series with a predetermined heat insulating space 9 interposed therebetween, and an interram mat 10 that integrally covers the outer periphery of the catalyst 8 and a frame that suppresses the front and rear thereof. The wire mesh mat 11 is fixedly supported in the case 7.

An exhaust introduction space 12 and an exhaust space 13 are provided in the front and rear of the case 7, and partition walls (not shown) with holes that open these spaces 12, 13 to the front and rear surfaces of each catalyst 8. Is formed. Reference numeral 14 denotes a flange for connecting the inlet 15 of the case 7 to the exhaust passage 4 on the upstream side, and 16 denotes a flange for connecting the outlet 17 to the exhaust passage 4 on the downstream side.

With this configuration, the exhaust gas from the engine 1 flows from the introduction space 12 in the catalyst device 6 through the entire catalyst 8 to the discharge space 13 and is discharged from the muffler 5 to the outside. At some times, as shown in FIG. 4, the upstream side 8a of each catalyst 8 has a small volume and warms up quickly due to the heat quantity of the exhaust gas, and the heat transfer to the downstream side 8b is suppressed by the heat insulating space 9, so the temperature rises to the activation temperature in a short time. . Since warm-up is performed by idle rotation, the amount of exhaust gas is small, and a sufficient purification rate can be obtained only with the catalyst capacity on the upstream side 8a. Further, when the upstream side 8a is activated, the exhaust gas temperature to the downstream side 8b rises due to the reaction heat of the catalyst, so that the heating of the downstream side 8b is promoted, and as a result, the temperature rise of the entire catalyst 8 becomes faster.

Therefore, each catalyst 8 in the case 7 is divided into two parts on a plane in which the volume of the upstream side 8a is smaller than the volume of the downstream side 8b and which is perpendicular to the flow of exhaust gas, and these are divided into predetermined heat insulating spaces 9 The exhaust gas emission during warm-up can be effectively improved by the simple structure of arranging in series with interposing the above.

In this embodiment, the parallel monolith catalyst 8 is described in the case 7, but the present invention is widely applied as a technique for realizing early activation of the catalyst regardless of the type and model of the catalyst device. It is possible.

[0015]

[Effect of device]

 In short, according to the present invention, in the catalyst device installed in the exhaust passage of the internal combustion engine, the catalyst has a volume on the upstream side smaller than the volume on the downstream side, and is in a plane substantially perpendicular to the exhaust flow. In addition to splitting, these were housed in series in the same case with a predetermined adiabatic space between them, so that the upstream catalyst part was activated quickly at engine startup, so the warm-up was very simple. The effect that the exhaust emission in the inside can be effectively improved is obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an engine exhaust system.

FIG. 2 is a partially cutaway perspective view of a catalyst device.

FIG. 3 is a schematic sectional view of the same.

FIG. 4 is an explanatory diagram showing effects of the catalyst device.

[Explanation of symbols]

 4 engine exhaust passage 6 catalyst device 7 case 8 monolith catalyst 8a upstream catalyst portion 8b downstream catalyst portion 9 adiabatic space

Claims (1)

[Scope of utility model registration request] 1. In a catalyst device installed in an exhaust passage of an internal combustion engine, the catalyst is divided in a plane in which the volume of the upstream side is smaller than the volume of the downstream side and is substantially perpendicular to the flow of exhaust gas, and these are divided. A catalyst device for an internal combustion engine, characterized in that a predetermined adiabatic space is interposed in the same case and they are housed in series.