Exhaust structure of an internal combustion engine

Abstract

This invention provides an exhaust structure for an internal combustion engine that can improve the warm-up performance of the air-fuel ratio sensor. [Solution] The exhaust structure 10 of the internal combustion engine includes an electrically heated catalytic converter 13 provided in the exhaust passage 12a of the internal combustion engine 11, in which the catalyst 31 is heated by the application of electricity, and an air-fuel ratio sensor 14 provided upstream of the catalytic converter 13 in the exhaust passage 12a. The air-fuel ratio sensor 14 has an exposed surface 14a that is exposed to the exhaust passage 12a. The exposed surface 14a is blackbody.

Description

Technical Field

[0001] The present disclosure relates to an exhaust structure of an internal combustion engine.

Background Art

[0002] Patent Document 1 discloses an exhaust structure of an internal combustion engine including an electrically heated catalyst device provided in an exhaust passage of the internal combustion engine and an air-fuel ratio sensor provided upstream of the catalyst device in the exhaust passage.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The catalyst of the catalyst device purifies the exhaust gas by chemically reacting when it reaches the activation temperature. The catalyst is warmed up by high-temperature exhaust gas. The air-fuel ratio sensor detects the air-fuel ratio by being activated by heating. When the air-fuel ratio sensor is arranged near the catalyst device, the air-fuel ratio sensor receives radiation from the catalyst device. However, since the exhaust temperature is low immediately after starting the internal combustion engine, it is difficult to warm up the catalyst. In this case, since the air-fuel ratio sensor hardly receives radiation from the catalyst, it is also difficult to warm up the air-fuel ratio sensor.

Means for Solving the Problems

[0005] An exhaust structure of an internal combustion engine for solving the above problems includes an electrically heated catalyst device provided in an exhaust passage of the internal combustion engine, in which the catalyst is heated by energization, and an air-fuel ratio sensor provided upstream of the catalyst device in the exhaust passage. The air-fuel ratio sensor has an exposed surface exposed to the exhaust passage, and the exposed surface is blackened.

Effects of the Invention

[0006] According to the present invention, the warm-up performance of the air-fuel ratio sensor can be improved. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the exhaust structure of an internal combustion engine. [Modes for carrying out the invention]

[0008] One embodiment of the exhaust structure for an internal combustion engine will be described with reference to the drawings. As shown in Figure 1, the exhaust structure 10 of the internal combustion engine comprises an internal combustion engine 11, an exhaust pipe 12, a catalytic converter 13, and an air-fuel ratio sensor 14. The internal combustion engine 11 in this embodiment is a gasoline engine. The internal combustion engine 11 has a plurality of cylinders (not shown). The space inside the exhaust pipe 12 is the exhaust passage 12a. The exhaust pipe 12 is connected to the internal combustion engine 11. The exhaust gas discharged from the internal combustion engine 11 flows through the exhaust passage 12a.

[0009] The catalytic converter 13 is installed in the exhaust passage 12a. The catalytic converter 13 has a catalyst 31 and a pair of electrodes 32. When the catalyst 31 reaches its activation temperature, it purifies the exhaust gas by a chemical reaction. The pair of electrodes 32 are attached to the catalyst 31. By applying a voltage between the pair of electrodes 32, an electric current flows through the catalyst 31. When an electric current flows through the catalyst 31, the catalyst 31 generates heat due to its electrical resistance. In other words, the catalytic converter 13 is an electrically heated catalytic converter in which the catalyst 31 is heated by the flow of electricity.

[0010] The air-fuel ratio sensor 14 is located upstream of the catalytic converter 13 in the exhaust passage 12a. The air-fuel ratio sensor 14 is positioned as close to the catalytic converter 13 as possible, while ensuring sufficient insulation distance between the conductive portion of the air-fuel ratio sensor 14 and the conductive portion of the catalytic converter 13. In this embodiment, the air-fuel ratio sensor 14 is inserted through a through-hole 12h provided in the upper part of the exhaust pipe 12. The air-fuel ratio sensor 14 protrudes downward from the inner circumferential surface of the exhaust pipe 12.

[0011] The air-fuel ratio sensor 14 includes a detection element 41, a heater 42, and a housing 43. The heater 42 heats the detection element 41. The housing 43 houses the detection element 41 and the heater 42. The housing 43 is provided with an inlet 43a for introducing exhaust gas into the housing 43 from the exhaust passage 12a. The detection element 41 is activated by being heated by the heater 42, thereby detecting the air-fuel ratio of the exhaust gas introduced into the housing 43.

[0012] The air-fuel ratio sensor 14 has an exposed surface 14a that is exposed to the exhaust passage 12a. The exposed surface 14a is blackened. The exposed surface 14a is blackened, for example, by applying blackbody paint. In this embodiment, the entire exposed surface 14a is blackened.

[0013] [Operation and Effects of This Embodiment] The operation and effects of this embodiment will now be explained. (1) The exhaust structure 10 of the internal combustion engine includes a catalytic converter 13 and an air-fuel ratio sensor 14. The catalytic converter 13 is installed in the exhaust passage 12a. The catalytic converter 13 is an electrically heated catalytic converter in which the catalyst 31 is heated by the application of electricity. The air-fuel ratio sensor 14 is installed in the exhaust passage 12a upstream of the catalytic converter 13. The air-fuel ratio sensor 14 has an exposed surface 14a that is exposed to the exhaust passage 12a. The exposed surface 14a is blackened.

[0014] The catalytic converter 13 is an electrically heated catalytic converter in which the catalyst 31 is heated by the application of electricity. Therefore, preheating of the catalyst 31 by applying electricity can be performed before starting the internal combustion engine 11. Consequently, the air-fuel ratio sensor 14 is warmed up by radiation received from the preheated catalyst 31. In addition, the exposed surface 14a of the air-fuel ratio sensor 14 is blackbody. Therefore, the air-fuel ratio sensor 14 can efficiently receive radiation from the preheated catalyst 31. Thus, the warm-up performance of the air-fuel ratio sensor 14 is improved.

[0015] (2) The improved warm-up performance of the air-fuel ratio sensor 14 enhances its detection performance during cold starts. This allows for air-fuel ratio control based on an accurate air-fuel ratio, thereby reducing emissions.

[0016] (3) In order to improve the warm-up performance of the air-fuel ratio sensor 14, for example, it is conceivable to place the air-fuel ratio sensor 14 near the internal combustion engine 11. However, the air-fuel ratio sensor 14 is required to be positioned so that exhaust gases from multiple cylinders hit the air-fuel ratio sensor 14 evenly. For this reason, it is difficult to place the air-fuel ratio sensor 14 near the internal combustion engine 11.

[0017] In contrast, the air-fuel ratio sensor 14 in this embodiment is warmed up by radiation received from the preheated catalyst 31, allowing the air-fuel ratio sensor 14 to be positioned away from the internal combustion engine 11. Therefore, the degree of freedom in mounting the air-fuel ratio sensor 14 is increased.

[0018] (4) Since the exposed surface 14a of the air-fuel ratio sensor 14 is blackened, the corrosion resistance of the air-fuel ratio sensor 14 is improved. As a result, it is no longer necessary to position the air-fuel ratio sensor 14 in the upper space of the exhaust passage 12a to prevent water in the exhaust pipe 12 from adhering to the air-fuel ratio sensor 14. In other words, the air-fuel ratio sensor 14 can be positioned in the lower space of the exhaust passage 12a. Therefore, the degree of freedom in the mounting direction of the air-fuel ratio sensor 14 is increased.

[0019] (5) An insulating distance is ensured between the air-fuel ratio sensor 14 and the catalytic converter 13. This suppresses short circuits between the air-fuel ratio sensor 14 and the catalytic converter 13. In addition, exhaust gas reflected by colliding with the catalytic converter 13 is less likely to reach the air-fuel ratio sensor 14, thereby ensuring the detection performance of the air-fuel ratio sensor 14.

[0020] [Example of changes] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0021] · The internal combustion engine 11 is not limited to a gasoline engine. The internal combustion engine 11 may be, for example, a diesel engine or a hydrogen engine. · The mounting direction of the air-fuel ratio sensor 14 may be changed as appropriate. The air-fuel ratio sensor 14 may be mounted, for example, so as to extend horizontally, or may be mounted so as to project upward from the lower part of the inner peripheral surface of the exhaust pipe 12.

[0022] · In the above embodiment, the entire exposed surface 14a was blackened, but a part of the exposed surface 14a may be blackened.

Explanation of Reference Numerals

[0023] 10… Exhaust structure of internal combustion engine, 11… Internal combustion engine, 12a… Exhaust passage, 13… Catalytic device, 14… Air-fuel ratio sensor, 14a… Exposed surface, 31… Catalyst

Claims

[Claim 1] An electrically heated catalytic converter is installed in the exhaust passage of an internal combustion engine, in which the catalyst is heated by the application of electricity. An air-fuel ratio sensor is provided in the exhaust passage upstream of the catalytic converter, An exhaust structure for an internal combustion engine, comprising: The air-fuel ratio sensor has an exposed surface that is exposed to the exhaust passage, The exposed surface is the exhaust structure of an internal combustion engine that has been blackened.

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