JPS6282233A - Exhaust system for internal combustion engine mounted with turbocharger - Google Patents

Abstract

PURPOSE:To improve the extent of engine performance so better, by providing a turbine wheel with ceramics, while covering an exhaust manifold, an exhaust pipe and an inner wall of a turbine housing with a ceramic layer, and utilizing heat resistance and lightweightiness inherent in ceramics. CONSTITUTION:Aluminum oxide is covered, 0.3mm or so in thickness, on the front of each inner wall of a housing 8 (made of resist cast iron), an exhaust manifold 5 (made of cast iron) and an exhaust pipe 6 (made of stainless steel) to be used for a turbocharger 7 by means of a plasma thermal spraying process. As for a turbine wheel 7a, a silicon nitride sintered body is used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exhaust system for an internal combustion engine equipped with a turbocharger, and in particular to such an exhaust system in the case of a turbocharger using a ceramic turbine wheel.

[Conventional technology]

A turbocharger uses exhaust gas energy to rotate a turbine wheel, which is connected to a compressor on the same axis.
This is a device that compresses intake air by driving the engine and supplies high-density intake air above atmospheric pressure to the engine. High-temperature exhaust gas is blown onto this exhaust turbine wheel.Recently, turbine wheels made of ceramics have been developed.

On the other hand, the exhaust manifold, exhaust pipe, and turbine housing of the turbocharger that connect the engine and the turbocharger are each made of the following materials. In other words, as engines have become more powerful in recent years, exhaust manifolds have been subjected to increased heat and vibration stress, and to cope with this, high-silicon spheroidal graphite cast iron is increasingly being used instead of spheroidal graphite cast iron. Exhaust pipes are generally carbon steel pipes or stainless steel pipes. Spheroidal graphite cast iron is used for turbine housings for engines with low exhaust temperatures, and Niresist cast iron, which has excellent heat resistance and oxidation resistance, is used for engines exposed to exhaust gas as high as 900°C.

[Problem that the invention seeks to solve]

The exhaust manifold, exhaust pipe, and inner wall of the turbine housing for conventional turbochargers are mainly made of iron-based materials, but since they are exposed to exhaust gas at around 900°C during engine operation, turbochargers Causes the formation of oxide scale inside the body. Such oxidized scale causes chipping damage to the blades of ceramic turbo wheels, which can lead to damage to ceramic turbine wheels.

[Means and effects for solving the problems] The present invention has the following features:
In order to solve the above problem, the inner walls of the exhaust manifold, exhaust pipe, and turbine housing made of iron-based materials from the engine to the turbocharger are coated with a ceramic layer to prevent the formation of oxide scales caused by high-temperature exhaust gas. , thereby preventing damage to the ceramic turbine.

Iron-based exhaust manifold, ceramic material covering the exhaust pipe and turbine housing inner wall,
There are no particular limitations on the coating method.

In terms of material, for example, A1. O,,Cr,03,T
ie, , Zr0z.

ZrSiO4 oxide and Tic, WC, Zr
C.SiC.

HfC, Ba, 5iJ4. TiN, BN
, AIN, and other non-oxides can be used, and as a coating method, electrodeposition, flame spraying, vapor deposition, etc. can be used.

The thickness of the ceramic coating layer is desirably 0.1 mm or more to prevent the generation of oxide scale;
．． Approximately 1 to 0.5 mm is appropriate.

〔Example〕

Figure 1 schematically shows the intake and exhaust system of an engine equipped with a turbocharger. In the figure, 1 is the engine. Air intake (
After passing through intake pipes 2 and 3 (not shown), air is taken into the engine via an intake manifold 4. Exhaust gas that has become hot due to combustion inside the engine 1 is sent to an exhaust pipe 6 via an exhaust manifold 5 and is discharged to the outside of the vehicle. The turbocharger 7 consists of a turbine wheel 7a housed in a turbine housing 8 provided midway through the exhaust pipe 6, and an impeller 7b housed in the turbine housing midway through the intake pipe 2.3. 7b is coaxially supported by a bearing section. Then, the turbocharger 7 is moved to the turbine wheel 7 by the exhaust gas.
A is rotated, and its driving force rotates an impeller to supply compressed intake air to the engine.

Conventionally, since the exhaust manifold 5, exhaust pipe 6, and turbine housing 8 through which high-temperature exhaust gas passes are made of iron-based materials, the high-temperature exhaust gas generates oxidized scale, which collides with the ceramic turbine wheel 7a, causing the turbine There was a risk that the wheel 7a would be damaged. Therefore, the present invention provides an exhaust manifold 5 and an exhaust pipe 6 that connect the engine 1 and the turbine wheel 7a.
The inner wall of the turbine housing 8 is coated with a ceramic layer to prevent oxide scale from forming there. Basically, it is sufficient to coat the inner wall of the exhaust pipe 6 up to the inlet of the turbine housing 8 with a ceramic layer.

Isamu Oshi - The front inner walls of the housing used for the upper turbocharger (made of resist cast iron), the exhaust manifold (made of cast iron), and the exhaust pipe (made of stainless steel) were coated with Al2O3 to a thickness of approximately 0.3 mm by plasma spraying. . The arc power used for thermal spraying was 300 kW, and atzoz powder with a particle size of 100 μm was introduced as a gas into a plasma flame ejected from an Ar electric current, and was sprayed onto the surface of the above-mentioned parts. A bench durability test was conducted on a turbine housing, exhaust manifold, and exhaust pipe coated with ^1203, and in a turbocharger using a silicon nitride sintered body as a turbine wheel.

When durability tests were conducted for a predetermined period of time in a temperature range of 900 to 1000°C, no damage was observed to the ceramic turbo wheels in all five tests.

As in Example 1, ZrO was applied to the inner wall of the housing, exhaust manifold, and exhaust pipe by plasma spraying.
□ was covered. A durability test similar to that in Example 1 was conducted on a turbocharger made of these parts and a silicon nitride turbo wheel, and no damage was observed to the ceramic turbo wheel in all five tests.

Durability tests similar to those in Examples 1 and 2 were conducted using a turbocharger consisting of a conventional housing, exhaust manifold, and exhaust pipe that were not coated with ceramic, and a turbine wheel made of silicon nitride. As a result, the ceramic turbo wheel was damaged in three out of five tests. Furthermore, when the surface of the ceramic wheel that was not damaged was observed, chipping was particularly noticeable on the blades due to the collision of fine particles made of iron oxide.

〔Effect of the invention〕

According to the present invention, damage to the ceramic turbo wheel is prevented, the reliability of a turbocharger using the ceramic turbo wheel is improved, and engine performance is improved because the heat resistance and light weight of ceramics can be utilized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an intake and exhaust system of an engine equipped with a turbocharger. 1...Engine, 2.3...Intake pipe, 4...
・Intake manifold, 5...Exhaust manifold 6...Exhaust pipe, 7...Turbocharger,
7a... Turbine wheel, 7b... Impeller, 8... Turbine housing.

Claims (1)

[Claims] 1. In the exhaust system of an internal combustion engine equipped with a turbocharger, the turbine wheel of the turbocharger is made of ceramic, and the exhaust manifold and exhaust pipe that connect the internal combustion engine and the turbocharger, as well as the inner wall of the turbine housing of the turbocharger, are made of ceramic. An exhaust system for an internal combustion engine equipped with a turbocharger, characterized by being coated with