JP2014218966A - Exhaust valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust valve showing a less adhesion characteristic at a valve surface, a heat-resistance of processed film, its close-fitness, uniformity of film thickness, wear-resistance characteristic and a low cost processing film even if a temperature during operation of an internal combustion engine is increased and exhaust gas of high temperature flows in the valve.SOLUTION: An exhaust valve 26 installed in an exhaust flow passage where exhaust gas of an internal combustion engine flows comprises: a valve body 261 formed with a communicating passage communicated with the exhaust flow passage; a valve body 262 arranged in the communicating passage; and a shaft member 263 connected to the valve body 262, inserted into shaft holes 311, 312 formed at the valve body 261, supported by the valve main body through bearings mounted in the shaft holes 311, 312 and rotationally driven. The entire surface of the valve body 261 is applied with ceramics coating.

Description

  The present invention relates to an exhaust valve mounted in an exhaust gas exhaust system of an internal combustion engine.

  2. Description of the Related Art Conventionally, a configuration is known in which an exhaust passage valve for switching a flow rate or adjusting a flow rate is installed in an exhaust passage through which exhaust gas discharged from a vehicle engine flows. For example, in an EGR device (exhaust gas recirculation device) installed to reduce NOx emission in exhaust gas discharged from a diesel engine, a configuration in which a flow path switching valve is provided in the exhaust gas recirculation passage is known. is there.

  Patent Document 1 discloses an anti-adhesion performance of deposits (also referred to as combustion products) generated by a composition component or solid matter in exhaust gas in an exhaust channel valve installed in an exhaust channel through which exhaust gas flows. An exhaust passage valve is disclosed that aims to provide a technique effective for improving the valve operability and the valve operability.

  In Patent Document 1, an exhaust passage valve is configured as follows to solve the problem. The valve body is made of an aluminum material, and the valve body housed in the valve body is made of a stainless material. The inside of the valve body prevents the deposits in the exhaust gas flowing in the exhaust flow path from adhering to the portion where the exhaust gas flow reaches and the outer periphery of the valve body, and between the valve body and the valve body. In order to reduce the sliding resistance of the contact portion, an oil-repellent coating treatment made of polytetrafluoroethylene is applied.

  In Patent Document 1, the above-mentioned fluorine coating treatment film is employed to solve the problem, but there are the following problems.

1) The heat resistance is inferior to the temperature rise when the internal combustion engine is operating.
2) Carbides contained in the exhaust gas are likely to adhere to the treated surface on the treated film surface.
3) The adhesion of the treated film is poor and easily peeled off.
4) The film thickness tends to be non-uniform.
5) The surface hardness of the treated film is low and the treated surface is easily damaged and easily worn.
6) Processing cost is high.

Japanese Patent No. 4767232

  The present invention has been made in view of the above circumstances, and even if the temperature rises when the internal combustion engine is operating or hot exhaust gas flows through the valve, the adherence of deposits on the valve surface is poor. It is an object of the present invention to provide an exhaust valve provided with a heat treated, adhesive, film thickness uniformity, wear resistance, and low cost treated film.

  An exhaust valve according to a first aspect of the present invention for achieving the above object is an exhaust valve attached to an exhaust passage through which exhaust gas of an internal combustion engine circulates, wherein the communication passage communicating with the exhaust passage is formed. A body, a valve body provided in the communication path, the valve body connected to the valve body, inserted into a shaft hole formed in the valve body, and the bearing through a bearing portion installed in the shaft hole. And a shaft member that is supported by the valve body and is driven to rotate. The entire surface of the valve body is subjected to a ceramic coating process.

  According to the first invention, since the ceramic coating is applied to the entire valve body of the exhaust valve, the corrosion resistance of the exhaust gas passage of the exhaust valve is improved. Further, it is possible to prevent the combustion products (adhered matter) from adhering to the exhaust gas passage of the exhaust valve. Further, this ceramic coating is less expensive than the fluorine coating, and the exhaust valve of the present invention can be reduced in cost.

  The exhaust valve according to a second aspect of the invention is characterized in that, in the first aspect of the invention, the ceramic coating is applied to the valve body.

  According to the second aspect of the invention, since the ceramic coating is applied to the valve body in the exhaust valve, not only the heat resistance of the valve body is improved, but also the adhesion of combustion products to the valve body can be prevented.

  The exhaust valve according to a third aspect is characterized in that, in the first or second aspect, the ceramic coating is applied to an outer peripheral portion of the shaft member that rotationally drives the valve body.

  According to the third invention, since this ceramic coating is applied to the outer peripheral surface of the shaft member that rotationally drives the valve body in the exhaust valve, not only the heat resistance of the shaft member is improved, but also the combustion product on the shaft member. Can be prevented.

  The exhaust valve according to a fourth aspect of the present invention is the exhaust valve according to any one of the first to third aspects, wherein the sliding portion of the shaft member that rotationally drives the valve body is coated with a metal or metal compound having heat resistance and solid lubricity. It is characterized by.

  According to the fourth aspect of the present invention, the rotational sliding portion of the shaft member that rotationally drives the valve body in the exhaust valve is coated with the solid lubricating metal, so that friction during sliding can be reduced. Further, it is possible to prevent wear of the shaft member that is a drive part of the valve body.

It is a figure showing a schematic structure of a diesel engine of this embodiment. It is a figure which shows the external appearance of the exhaust valve (EGR cooler switching valve) in FIG. It is explanatory drawing which displayed the main components of the exhaust valve in FIG. It is explanatory drawing of the operation mode of the exhaust valve in FIG. It is explanatory drawing of the process of a ceramic coating used for the exhaust valve of this invention. It is explanatory drawing of the thermal behavior of the ceramic coating used for the exhaust valve of this invention. It is explanatory drawing of the present fluorine coating process and ceramic coating process. It is explanatory drawing of the exhaust valve of Example 3 and Example 4. FIG.

  The best mode for carrying out the present invention will be described with reference to the drawings.

<1> Configuration of Internal Combustion Engine Hereinafter, an exhaust valve according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. First, the configuration of a diesel engine 100 as an embodiment of the “internal combustion engine” in the present invention will be described with reference to FIG.

  A diesel engine 100 shown in FIG. 1 is a diesel engine (internal combustion engine) mounted on an automobile, a ship, a work machine, or the like. As shown in FIG. 1, the diesel engine 100 includes an engine body 11, an intake passage 12, an exhaust passage 115, a turbocharger 14, an EGR device (exhaust gas recirculation device) 20, and the like.

  The intake passage 12 is a passage through which intake gas sucked into the engine body 11 flows, and is configured such that intake air (fresh air) flows in the order of the intake pipe 12a, the intake pipe 12b, and the intake manifold 12c. Intake (fresh air) flows into the intake pipe 12a by the compressor 17a constituting the turbocharger 14, and flows into the intake pipe 12b via the compressor 15a. The compressor 17a is driven by a turbine 17b. The intake air (fresh air) circulated in the intake pipe 12b merges with exhaust gas circulated through EGR pipes 20a and 20d, which will be described later, and flows into the intake manifold 12c. The air is sucked into each cylinder of the engine body 11.

  The exhaust passage 15 is a passage through which exhaust gas exhausted from the engine body 11 flows, and is configured such that exhaust gas flows in the order of the exhaust manifold 15a, the exhaust pipe 15b, and the exhaust pipe 15c. Most of the exhaust gas flowing into the exhaust manifold 15a from each cylinder of the engine body 11 flows to the turbine 17b side through the exhaust pipe 15b, and after rotating the turbine 17b, the exhaust gas purification device (not shown) is passed through the exhaust pipe 15c. ). On the other hand, a part of the exhaust gas flowing into the exhaust manifold 15a branches and flows to the EGR passage 21 side of the EGR device 20.

  The EGR device 20 is a device having an EGR (Exhaust Gas Recirculation) function for recirculating exhaust gas to the intake system of the diesel engine 100, and includes an EGR passage 21, an EGR cooler 23, and a control unit (controller) 25. And an exhaust valve 26 and the like. The switching valve 26 of the EGR device 20 is the present invention. This “exhaust valve” is an “EGR cooler switching valve”.

<2> Configuration of Exhaust Valve Next, the detailed configuration and operation of the exhaust valve (EGR cooler switching valve) 26 will be described with reference to FIGS.

  First, the overall configuration of the exhaust valve 26 will be described with reference to FIGS. FIG. 2 is an external view of the exhaust valve 26 in FIG. 1, and FIG. 3 is an explanatory view showing the main components of the exhaust valve 26 in FIG. FIG. 4 shows the structure of the operating part of the valve body 262 in the exhaust valve in FIG. 2, and is an explanatory view of the operation mode of the exhaust valve.

  As shown in FIGS. 2 and 3, the exhaust valve 26 is provided with a valve body (valve) 262 inside a valve body (body) 261 having air cooling fins 267 for air cooling. For example, an aluminum material can be used for the valve body 261, and an iron-based material such as cast iron can be used when the exhaust gas temperature is high. A material that can exhibit the required heat resistance according to the temperature of the exhaust gas may be used.

  The valve body 262 is supported on the valve body 261 side via a shaft member 263, and the shaft member 263 is connected to the actuator 266 via a lever 264 and a rod 265. For example, a ferritic or austenitic stainless material can be used for the valve body 262, but the valve body 262 is not limited to this.

  Although not shown, the internal structure of the actuator 266 has a diaphragm chamber provided with a diaphragm inside, and a negative pressure is applied to the diaphragm chamber through a negative pressure tube. When a negative pressure is applied to the actuator 266, the rod 265 is driven in the direction of the arrow P in FIG. 3, and when the negative pressure is purged and atmospheric pressure, the rod 265 is driven in the direction of the arrow Q. The shaft member 263 is rotationally driven in the arrow X direction or the arrow Y direction in FIG. As an actuator for driving the shaft member 263, an electric actuator such as an electric motor or an electromagnetic solenoid can be used in addition to the negative pressure actuator 266 as in the present embodiment.

<3> Operation of Exhaust Valve Here, the operation of the exhaust valve of the present invention will be described with reference to FIG. FIG. 4 is an explanatory diagram of the operation mode of the exhaust valve. “EGR cooler use mode” (hereinafter referred to as “use mode”) and “EGR cooler non-use mode” (hereinafter referred to as “unused mode”) depending on the operating state of the valve body 262 inside the valve body 261. It operates in two modes. The valve body 262 is formed in a substantially L shape and is fixedly connected to the shaft member 263 with a bolt or the like. The valve body is rotationally driven via the actuator 266 described above. As a result, the exhaust valve is switched between the use mode and the unused mode.

  FIG. 4A shows a use mode in which the exhaust gas cooled through the cooling circuit is sent to the intake system. On the other hand, FIG. 4B is a mode in which the exhaust gas is sent directly to the intake system without being cooled.

  As described above, the inner surface of the valve body main body 261 of the exhaust valve and the outer peripheral surface of the valve body 262 are exposed to high-temperature exhaust gas and combustion products. Therefore, the inner surface of the valve body 261 and the valve body 262 are susceptible to thermal damage, and combustion products adhere to the surface. The adhesion of combustion products adversely affects the operation of the valve body and the function of the exhaust valve itself. Conventionally, a fluorine coating has been employed on the inner surface of an exhaust valve for the purpose of preventing the adhesion of such combustion products. However, as mentioned in “Background”, there are many problems.

  In the present invention, a ceramic coating is employed on the inner surface of the exhaust valve. The ceramic coating will be described below.

<4> Ceramic coating The ceramic coating employed in the exhaust valve of the present invention is a ceramic coating treatment using a plasma electrolytic oxidation method. With the treatment method shown in FIG. 5, the surface of the treated component is coated with a plasma anodic oxide film by immersing the treated component and the electrode in an aqueous solution and causing a plasma discharge between them. A ceramic thin film such as aluminum oxide or zirconium oxide can be treated with an equal thickness as the oxide film.

  The result of evaluating the thermal behavior of this ceramic coating is shown in FIG. As shown in FIG. 6, there is obtained a result that there is no change up to 600 ° C. in TG (weight change) and DTA (exothermic / endothermic behavior). The exhaust gas of a normal internal combustion engine is about 300 ° C., and there is no problem at all. This ceramic coating exhibits an effect superior to that of the conventional fluorine coating.

  FIG. 7 is a diagram comparing the ceramic coating process used in the exhaust valve of the present invention and the fluorine coating used in the conventional exhaust valve. As shown in FIG. 7, the ceramic coating is processed in the process of degreasing → water washing → plasma oxidation treatment → water washing → drying. On the other hand, the fluorine coating is processed through numerous steps as shown in FIG. Therefore, the present ceramic mix coating is much less expensive than the fluorine coating.

  By employing such a ceramic coating for the exhaust valve, heat resistance and corrosion resistance can be improved, and further, adhesion of combustion products to the inner surface of the exhaust valve can be prevented. Therefore, the function of the exhaust valve can be maintained.

  Further, when such a ceramic coating is used for the exhaust valve, the entire surface of the exhaust valve is processed for the convenience of the processing step. Accordingly, since the outer peripheral surface of the exhaust valve is also coated with ceramics, a rust prevention effect can be expected when the exhaust valve is manufactured from an iron-based material.

  In Example 1, a ceramic coating was applied to the entire surface of the valve body 261 of the exhaust valve. In the present embodiment, the same ceramic coating as that of the first embodiment is applied to the outer peripheral surface of the valve body 262. Thereby, the heat resistance of the valve body is improved, and the adhesion of combustion products can be prevented. Therefore, the valve body operates reliably and the function of the exhaust valve can be maintained.

This embodiment will be described with reference to FIG. FIG. 8 shows a state where the M part of FIG. 3 is housed in the valve body 261. In the shaft member 263, bearings 313 and 314 are fitted into shaft holes 311 and 312 provided in the valve body 261, and the shaft member is rotatably inserted into the bearing. A portion where the valve body 262 is attached to the shaft member 263 is exposed to high-temperature exhaust gas. Moreover, it is in the state which a combustion product tends to adhere. In the present embodiment, the ceramic coating of the first embodiment is applied to the outer peripheral surface of the valve body 262. As a result, the heat resistance and corrosion resistance of the shaft member are improved, and adhesion of combustion products can be prevented. Therefore, the valve body operates reliably and the function of the exhaust valve can be maintained.
In the present embodiment, the same ceramic coating as that of the first embodiment is applied to the inner peripheral surfaces of the shaft holes 311 and 312. This improves the wear resistance of the shaft hole. Therefore, even when the bearings 313 and 314 are abolished, the shaft member rotates reliably and the function of the exhaust valve can be maintained.

  In the present embodiment, the surface of the shaft member 263 that is a member that rotationally drives the valve body 262 is subjected to a surface treatment that reduces the sliding resistance of the rotating sliding portion. As the surface treatment, a metal or metal compound coating having heat resistance and solid lubricity is applied. As the metal film, a metal material such as molybdenum can be sprayed on the surface of the main body of the shaft member, or a molybdenum disulfide film treated as the metal compound can be used. Thereby, the wear resistance of the shaft member is improved, and mechanical loss when the shaft member rotates and slides can be reduced.

DESCRIPTION OF SYMBOLS 100: Diesel engine 11: Engine main body 12: Intake passage 12a, 12b: Intake pipe 12c: Intake manifold 14: Turbocharger 15: Exhaust passage 15a: Exhaust manifold 15b, 15c: Exhaust pipe 17a: Compressor 17b: Turbine 20: EGR device 20a, 20d: EGR pipe 21: EGR passage 23: EGR cooler 25: controller 26: exhaust valve (EGR switching valve)
261: Valve body 262: Valve body 263: Shaft member 264: Lever 265: Rod 266: Actuator 267: Fin 311, 312: Shaft hole 313, 314: Bearing

Claims (4)

An exhaust valve attached to an exhaust passage through which exhaust gas from an internal combustion engine flows,
A valve body having a communication passage communicating with the exhaust flow path;
A valve body provided in the communication path;
A shaft member connected to the valve body, inserted into a shaft hole formed in the valve body, supported by the valve body via a bearing portion installed in the shaft hole, and driven to rotate;
With
An exhaust valve, wherein the entire surface of the valve body is subjected to a ceramic coating process.   The exhaust valve according to claim 1, wherein the ceramic coating is applied to the valve body.   The exhaust valve according to claim 1 or 2, wherein the ceramic coating is applied to an outer peripheral portion of the shaft member that rotationally drives the valve body.   The exhaust valve according to any one of claims 1 to 3, wherein a sliding portion of the shaft member for rotationally driving the valve body is coated with a metal or metal compound having heat resistance and solid lubricity. .

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