JPH0571433A - Method for decreasing total hydrocarbon in exhaust gas of automobile - Google Patents

Abstract

PURPOSE:To decrease unburnt fuel and HC discharged from a combustion chamber in a low temperature starting range by using fuel in which the maximum number of carbon of compositive component is smaller and the total number of the compositive component is smaller those of than gasoline in parallel with use of the gasoline at the time of starting an engine. CONSTITUTION:Gasoline sucked by a pump 22 from a gasoline tank 2 is injected into an intake pipe 13 by means of an injector 21 for gasoline, and at the same time the gasoline is reformed by a reformer 33 during run, and fuel made molecularly lower than the gasoline is stocked in a fuel tank 34. The fuel made molecularly lower is injected in the intake pipe 13 by means of an injector 31 for the fuel at the time of starting the engine. Consequently, a discharge quantity of total hydrocarbon in the exhaust gas is decreased while the hydrocarbon being caused by combustion product for which the components such as paraffin, olefin and aromatic compound are made molecularly low by the combustion, and by action of the unburnt fuel presented by liquid-like bleed of component not vaporized by contact with an engine inner wall cold at the time of its start.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing unburned fuel, hydrocarbons (hereinafter referred to as HC), CO, and NOx, which are combustion products of fuel, emitted from an automobile engine, particularly from engine start. The unburned portion of the fuel discharged in the low temperature starting region leading to the warm-up operation, H which is the combustion product of the fuel
A method of reducing C.

[0002]

2. Description of the Related Art Exhaust gas from an automobile engine contains unburned fuel, HC, CO, and NO which are combustion products of fuel.
x, etc. are included. When released into the atmosphere, they cause the generation of photochemical smog and acid rain, which have a great adverse effect on humans and the ecosystem. Beginning in the 1970s, exhaust gas regulations were set, and methods for removing harmful substances in exhaust gas were eagerly studied by automobile manufacturers.
A noble metal-based three-way catalyst that simultaneously treats O and NOx has been developed.

However, in recent years, environmental problems on a global scale such as ozone layer depletion, global warming, and acid rain have been highlighted, and automobile exhaust gas regulation values are further strengthened.
Among the harmful substances of HC, CO, and NOx, especially HC
Regarding, because it greatly contributes to the ozone layer depletion,
Regulations will be more stringent than other substances.

Approximately 70% of the total amount of HC released from the automobile into the atmosphere is exhausted within about 2 minutes after the start of engine activation of the automobile. This is due to the fact that combustion is performed in a fuel-rich state when the engine is started, which does not reach steady operation, the exhaust gas temperature is low, and the three-way catalyst does not work.

Therefore, in addition to the improvement of the engine combustor and the combustion state, two exhaust gas purifying catalysts, a low temperature catalyst at the time of starting and a high temperature catalyst at the time of steady operation, are installed in parallel (Japanese Patent Laid-Open No. 61). -200316), a bypass passage is provided in the exhaust pipe from the engine outlet to the exhaust gas purifying catalyst, and an adsorbent for adsorbing the exhaust gas at the time of start is installed therein (JP-A-63-63).
-68713), during the period from engine start to warming up, secondary air is supplied to the exhaust gas introduction part of the three-way catalyst to cause the combustion reaction on the three-way catalyst (JP-A-1-227815). Etc. methods have been proposed. However, these inventions treat HC once discharged from the engine combustor, and the essential problem cannot be solved unless the HC discharge amount at the engine combustion chamber outlet is reduced.

[0006]

SUMMARY OF THE INVENTION In order to meet the strict requirement for reduction of HC emissions, the present invention unburns fuel discharged from an engine combustion chamber particularly in a low temperature starting region from engine start to warm-up operation. Min, H which is the combustion product of fuel
It is intended to provide a technique for reducing C and reducing total hydrocarbons in exhaust gas.

[0007]

[Means for Solving the Problems] Since gasoline is composed of various components such as paraffins, olefins, and aromatics having 10 or less carbon atoms, it could not be vaporized by coming into contact with the cold engine inner wall at startup. Since the components flow out in a liquid state or the components with a high carbon number are burned to generate a component with a low carbon number, H
C is discharged. We pay attention to this point, and as a technique to reduce unburned content of fuel discharged from the engine combustion chamber and HC which is a combustion product of fuel in the low temperature starting region from engine start to warm-up operation, at engine startup The present invention has led to the invention of a method for reducing total hydrocarbons (hereinafter referred to as THC) using a fuel in which the maximum number of constituent carbon atoms is smaller than that of gasoline and the total number of constituent components is smaller. Hereinafter, the present invention will be described in detail.

A method for reducing THC in vehicle exhaust gas by using a fuel having a maximum number of constituent carbon atoms smaller than that of gasoline and a total number of constituent components instead of gasoline at the time of engine startup in a gasoline vehicle. In particular, as a fuel to replace gasoline, specifically, the low boiling point component in the constituent components of gasoline already mounted as a fuel on a vehicle is vaporized and separated, or the constituent component is reformed to reform the constituent component. The fuel whose maximum carbon number is 6 or less is used. As a method for reforming or cracking gasoline, a catalytic cracking method using a catalyst such as zeolite or a mixed vapor with hydrogen is used as Pt or Pt-
There is a method of catalytically reforming with a Re catalyst or a noble metal catalyst such as Pt or Pd supported on a solid acid. For the separation method,
Liquid phase coated diatomaceous earth, adsorbent method such as activated carbon, membrane separation method, heating method, microwave method or a combination thereof is possible. The reforming, disassembling, and separating operations by these methods are carried out while the vehicle is running by a method that requires a long operation such as an adsorbent method and a membrane separation method, and the products are stored in a tank and used when starting the engine. With a method that can be performed in a relatively short time, such as a heating method or a microwave method, it is possible to start the engine while producing fuel components.

As described above, the method of reforming, decomposing and separating gasoline to produce a fuel and using the fuel takes time depending on the method, or carbon by reforming, decomposing and separating. There is also a problem that a large number of HC may remain as a residue. Therefore, a method of vaporizing or reforming methanol, which is liquid at room temperature and has a lower molecular weight and a lower boiling point than gasoline, is also effective.

In the method of producing fuel by vaporizing, reforming, decomposing and separating gasoline and methanol and using the same, a plurality of production steps are added to the conventional system. Therefore, we use a pre-purified fuel as a fuel only at the time of starting, that is, instead of gasoline when starting the engine, methanol, methane,
TH in automobile exhaust gas characterized by using propane, hydrogen, LPG, or natural gas as a fuel
A method of reducing C was devised. These fuels are filled in a dedicated tank provided separately, and are introduced into the injector in a liquid state or in a vaporized state at the time of starting the engine and injected into the engine. LPG is mainly composed of C3H8 and C4H10, and has a higher carbon number than gasoline.
The amount of unburned aromatics and combustion products can be reduced. The effect becomes even greater with refined fuels such as methanol, methane, propane, and hydrogen. These fuels are produced separately. The exhaust gas purification system installed in an automobile has the function of adding oxygen-enriched air to the exhaust gas at the engine outlet, and when that oxygen is produced by electrolysis of water, hydrogen that is simultaneously produced is used for the engine. It can be used as fuel. In addition to methanol, methane, propane, hydrogen, LPG, natural gas, a mixture of gasoline and methanol, kerosene, and light oil are also effective.

Gasoline and these fuels are supplied separately by two injectors provided exclusively, or by one injector. When supplied from one injector, if the fuel is liquid, liquid fuel can also be injected from the nozzle provided for gasoline injection of the injector. If the fuel is introduced into the injector in the gaseous state, it is not possible to inject the gaseous fuel from the nozzle of the injector that injects gasoline. Therefore, the vaporized fuel is injected from the auxiliary air injection portion of the injector structure that atomizes the gasoline injected from the nozzle by introducing the auxiliary air represented by Japanese Patent Application No. 2-115596. By this method, it is possible to supply two kinds of fuel to the inside of the engine with the same injector, and not only to reduce the amount of HC produced by mixing gasoline and fuel from the engine start up to steady operation. The fuel injected as gas atomizes gasoline and has the same effect as auxiliary air.

Regarding the mixing ratio of gasoline and the above-mentioned fuel, the fuel is used at the time of starting the engine, the fuel is gradually mixed with the gasoline to increase the ratio of the fuel, and only the gasoline is operated in the steady state. The mixing ratio, injection amount, injection time, etc. of these are controlled by the intake pipe at the engine inlet, the engine inside, the engine outlet exhaust gas, the temperature of the exhaust gas treatment catalyst, the HC inside the engine, the engine outlet exhaust gas, and the exhaust gas treatment catalyst outlet gas. , CO, NOx, oxygen concentration values are detected by sensors.

In a gasoline automobile, when the engine is started, the fuel used in combination with gasoline has a maximum carbon number of constituents smaller than that of gasoline and a total number of constituents smaller than that of gasoline. When used in combination with the exhaust gas purifying device using the installed catalyst, the THC reducing method is more effective. By combining with an exhaust gas purification device in which an electrocatalyst is installed at the engine outlet and an exhaust gas purification catalyst (main catalyst) is installed in the subsequent stage, THC discharged until the electrocatalyst is heated to a predetermined temperature can be obtained. It can be reduced. By combining an exhaust gas purification device with a water adsorbent and HC adsorbent installed at the engine outlet and an exhaust gas purification catalyst (main catalyst) installed at the subsequent stage, the HC adsorbent capacity is reduced and the temperature of the main catalyst is reduced. The amount of HC desorbed from the adsorbent before the temperature rises can be reduced. By combining an exhaust gas purification device with a pre-catalyst installed at the engine outlet and a main catalyst at the subsequent stage, the amount of untreated HC discharged before the pre-catalyst rises to a temperature sufficient for the reaction is reduced. it can.

[0014]

The operation of the present invention will be described below.

Gasoline is paraffin having 10 or less carbon atoms,
It is composed of various kinds of components such as olefins and aromatics.
HC in the combustion exhaust gas of gasoline could not be vaporized due to the combustion products (mainly low-molecular weight paraffins and olefins) in which these components have been reduced to a low molecular weight due to combustion, and contact with the cold engine inner wall at startup. It can be classified as an unburned fuel (such as aromatic compounds of benzene and toluene) such as the component flowing out in liquid form. Therefore, as in the present invention, by using a fuel having a low molecular weight component in gasoline or a fuel having a low molecular weight HC other than gasoline as a main component at the time of starting the engine, a large amount of H derived from
It acts to reduce C.

[0016]

The present invention will be described in detail below with reference to specific examples.

<Embodiment 1> FIG. 1 is an embodiment of the present invention and is a systematic diagram of a part of a fuel supply system and an engine when reformed gasoline is used as a fuel.

From the gasoline tank 2 to the gasoline pump 2
In the gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the gasoline injector 21, the gasoline sucked by the pump 32 from the gasoline tank 2 while traveling is reformed by the reformer 33. The fuel whose molecular weight is lower than that of gasoline is stocked in the fuel tank 34 and injected into the intake pipe 13 by the fuel injector 31 when the engine is started. When fuel and gasoline are used together, the two injectors 21 and 31 simultaneously inject into the intake pipe 13 and mix them in the intake pipe 13.
In this way, by using gasoline reformed as a fuel, it is possible that the components such as paraffin, olefins, and aromatics come into contact with combustion products whose molecular weight is lowered by combustion and the engine inner wall that is cold at startup. As a result, THC in the exhaust gas caused by unburned fuel, such as components that could not be vaporized flowing out in liquid form, can be reduced.

<Embodiment 2> FIG. 2 is a systematic diagram of a part of a fuel supply system and an engine when a reformed fuel other than gasoline is used as the fuel.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the gasoline injector 21, fuel other than gasoline such as methanol filled in the fuel tank 3 is pumped to the reformer 33. The fuel reformed and fed is injected into the intake pipe 13 by the fuel injector 31 when the engine is started. When using both fuel and gasoline, the two injectors 21 and 31
At the same time, it is injected into the intake pipe 13 and mixed in the intake pipe 13. The reforming by the reformer 33 is carried out in parallel when the engine is started, or is carried out during traveling and stocked in the tank. In the latter case, the fuel tank 34 and the pump 35 as shown in FIG. 1 can be installed downstream of the reformer 33. <Third Embodiment> FIG. 3 is a systematic diagram of a part of a fuel supply system and an engine when a liquid fuel other than gasoline is vaporized and used as a fuel.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the gasoline injector 21, the liquid fuel filled in the fuel tank 3 is sent to the carburetor 36 by the pump 32 and is vaporized. Is injected into the intake pipe 13 by the fuel injector 31 when the engine is started. When fuel and gasoline are used together, the two injectors 21 and 31 simultaneously inject into the intake pipe 13 and mix them in the intake pipe 13. The vaporization of fuel by the vaporizer 36 is performed in parallel when the engine is started.

<Embodiment 4> FIG. 4 is a systematic diagram of a part of a fuel supply system and an engine when a gaseous fuel is used as a fuel.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the gasoline injector 21, the gaseous fuel filled in the fuel tank 3 is sent by the pump 32, and the fuel injector 31 for starting the engine is used. To inject into the intake pipe 13. When fuel and gasoline are used together, the two injectors 21 and 31 simultaneously inject into the intake pipe 13 and mix them in the intake pipe 13.

<Embodiment 5> FIG. 5 shows a fuel supply system and a part of an engine when a liquid fuel other than gasoline is vaporized and used as fuel, and gasoline and fuel are supplied to the intake side of the engine by the same injector. FIG.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the injector 23, the fuel filled in the fuel tank 3 is sent to the carburetor 36 by the pump 32, and the vaporized fuel is started. At some times, it is injected into the intake pipe 13 by the injector 23. When both fuel and gasoline are used, the injector 23 simultaneously injects them into the intake pipe 13 to mix them at the time of injection.
When the injector 23 has a structure that atomizes the gasoline injected from the nozzle by introducing auxiliary air,
Inject the vaporized fuel from the auxiliary air injection part. As a result, the same effect can be obtained by introducing the auxiliary air, and further the THC can be reduced.

<Embodiment 6> FIG. 6 is a system diagram of a fuel supply system and a part of the engine when a gas fuel other than gasoline is used as the fuel and the gasoline and the fuel are supplied to the intake side of the engine by the same injector. is there.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the injector 23, the fuel filled in the fuel tank 3 is pumped by the pump 32 when the engine 23 starts the intake pipe 13
Inject. When both fuel and gasoline are used, the injector 23 simultaneously injects them into the intake pipe 13 to mix them at the time of injection. In the case where the injector 23 has a structure in which the gasoline injected from the nozzle is atomized by introducing the auxiliary air, the vaporized fuel is injected from the auxiliary air injection part. As a result, the same effect can be obtained by introducing the auxiliary air, and further the THC can be reduced.

<Embodiment 7> FIG. 7 is an embodiment of the present invention, in which an electrocatalyst is installed at the engine outlet in a fuel supply system when liquid fuel other than gasoline is vaporized and used as fuel. It is a flow in which an exhaust gas purifying device in which an exhaust gas purifying catalyst (main catalyst) is installed in stages is combined, and a control system configuration flow thereof.

From the gasoline tank 2 to the gasoline pump 2
In a gasoline engine system in which the gasoline sucked by 2 is injected into the intake pipe 13 of the engine by the gasoline injector 21, the liquid fuel filled in the fuel tank 3 is sent to the carburetor 36 by the pump 32 and is vaporized. Is injected into the intake pipe 13 by the fuel injector 31 when the engine is started. The exhaust gas in which these fuels are burned is introduced into the exhaust pipe 14, and after the air is added by the secondary air pump 61 to promote combustion, the electrocatalyst 51 and the exhaust gas purifying catalyst installed on the downstream side are added. It is processed by (main catalyst) 52 and discharged into the atmosphere.

Mixing ratio of gasoline and fuel, intake pipe 13
The amount of injection to the engine, the injection time, etc. are controlled by the intake pipe at the engine inlet, the engine interior, the exhaust gas at the engine outlet exhaust pipe 14,
This is performed by detecting values of temperature, air-fuel ratio, HC, CO, NOx, and oxygen concentration of the electrocatalyst 51 and the exhaust gas purifying catalyst (main catalyst) 52 with sensors.

The combination of the fuel supply system and the exhaust gas purifying device is not limited to this embodiment, and the exhaust gas purifying device of this embodiment is already described in Embodiment 1, Embodiment 2, Embodiment 4, and Embodiment 4. A combination with the fuel supply system of the fifth and sixth embodiments is also possible. Further, it is also possible to combine each fuel supply system with an exhaust gas purifying device other than this embodiment.

<Embodiment 8> FIG. 8 is an explanatory view of an exhaust gas purifying apparatus which can be combined with the fuel supply systems of Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4, Embodiment 5 and Embodiment 6. Is.

A water and HC adsorbent 54 is installed in the exhaust pipe at the engine outlet, and an exhaust gas purifying catalyst (main catalyst) 52 is installed in the subsequent stage. Air is added to the exhaust gas at the engine outlet by the secondary air pump 61 for the purpose of promoting the combustion of HC and suppressing the temperature rise of the adsorbent.

<Embodiment 9> FIG. 9 is an explanatory view of an exhaust gas purifying apparatus which can be combined with the fuel supply systems of Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4, Embodiment 5 and Embodiment 6. Is.

A front catalyst 53 is installed in the exhaust pipe at the engine outlet, and an exhaust gas purification catalyst (main catalyst) 52 is installed in the subsequent stage. Air is added to the exhaust gas at the engine outlet by the secondary air pump 61 in order to accelerate the combustion of HC.

[0036]

According to the method of the present invention, unburned components of fuel discharged from the engine combustion chamber and hydrocarbons, which are combustion products of fuel, are discharged in the low temperature starting region from engine start to warm-up of the automobile. It is possible to reduce the amount of emission into the atmosphere.

[Brief description of drawings]

FIG. 1 is a system diagram of a fuel supply system according to an embodiment of the present invention.

FIG. 2 is a system diagram of a fuel supply system when a reformed fuel other than gasoline is used as the fuel.

FIG. 3 is a system diagram of a fuel supply system when a liquid fuel other than gasoline is vaporized and used as a fuel.

FIG. 4 is a systematic diagram of a part of a fuel supply system and an engine when using gaseous fuel as fuel.

FIG. 5 is a system diagram of a fuel supply system and a part of the engine when a liquid fuel other than gasoline is vaporized and used as a fuel, and the gasoline and the fuel are supplied to the intake side of the engine by the same injector.

FIG. 6 is a systematic diagram of a fuel supply system and a part of the engine when a gas fuel other than gasoline is used as the fuel and the gasoline and the fuel are supplied to the intake side of the engine by the same injector.

FIG. 7 is a system diagram of a fuel supply system, an exhaust gas purification device, and its control system.

FIG. 8 is an explanatory diagram of an exhaust gas purification device.

FIG. 9 is an explanatory diagram of an exhaust gas purification device.

[Explanation of symbols]

11 ... Cylinder, 12 ... Piston, 13 ... Intake pipe, 14
... Exhaust pipe, 15 ... Intake valve, 16 ... Exhaust valve, 17
... spark plug, 2 ... gasoline tank, 21 ... gasoline injector, 22 ... gasoline pump, 31 ... fuel injector, 32 ... pump, 33 ... reformer, 34 ... fuel tank, 35 ... pump.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Yamashita 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitate Manufacturing Co., Ltd., Hitachi Research Institute (72) Hiroshi Miyadera 4026 Kuji Town, Hitachi City, Hitachi City, Ibaraki Prefecture Nitate Factory Inside Hitachi Research Laboratory (72) Inventor Takeshi Atako 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (15)

[Claims] 1. In an automobile exhaust gas, which is used together with gasoline at the time of engine startup, to use a fuel having a maximum number of carbon atoms of a constituent component smaller than that of gasoline and a total number of constituent components less than that of gasoline. How to reduce total hydrocarbons. 2. The automobile exhaust system according to claim 1, wherein the fuel is used when the engine is started, the gasoline is gradually mixed with the fuel to increase the proportion of the gasoline, and the engine is driven only by the gasoline in a steady state. How to reduce total hydrocarbons in gas. 3. The maximum carbon number of a constituent component according to claim 1, wherein a low boiling point component in the constituent component of the gasoline is vaporized and separated as the fuel, or the gasoline is reformed so that the maximum carbon number of the constituent component is 6 or less. To reduce total hydrocarbons in automobile exhaust gas using the specified fuel. 4. The method for reducing total hydrocarbons in an automobile exhaust gas according to claim 1, wherein methanol is vaporized as the fuel or a fuel obtained by reforming methanol is used. 5. The fuel according to claim 1, wherein one or more of methanol, a mixture of gasoline and methanol, methane, propane, hydrogen, LPG, natural gas, kerosene, light oil is used as the fuel instead of the gasoline. A method for reducing total hydrocarbons in automobile exhaust gas. 6. The method for reducing total hydrocarbons in vehicle exhaust gas as claimed in claim 1, wherein the liquid fuel stored in the tank is vaporized by a vaporizer and then sent to an injector and injected into the engine. 7. The method for reducing total hydrocarbons in vehicle exhaust gas according to claim 1, wherein the gasoline and the fuel are injected into an engine by using the same injector. 8. The total exhaust gas of a vehicle for injecting the vaporized fuel from an auxiliary air injection portion of an injector structure for atomizing the gasoline injected from a nozzle by introducing auxiliary air. Hydrocarbon reduction method. 9. The method for reducing total hydrocarbons in vehicle exhaust gas according to claim 7, wherein the gasoline or the fuel is injected into the engine from the same nozzle of the same injector. 10. A method for reducing total hydrocarbons in an exhaust gas of an automobile, comprising combining an exhaust gas purifying device having an electrocatalyst at an engine outlet and an exhaust gas purifying catalyst at a subsequent stage. 11. A total hydrocarbon contained in an exhaust gas of an automobile according to claim 1, wherein a water adsorbent and a hydrocarbon adsorbent are installed at an engine outlet, and an exhaust gas purifying device in which an exhaust gas purifying catalyst is installed after the engine is combined. Reduction method. 12. A method for reducing total hydrocarbons in an automobile exhaust gas according to claim 1, wherein an exhaust gas purifying device having a front catalyst installed at an engine outlet and a main catalyst installed at a subsequent stage is combined. 13. The gasoline according to claim 10, wherein the fuel is operated from the start of engine startup until the electrocatalyst is heated to a predetermined temperature, and then the gasoline is gradually mixed with the fuel. The method for reducing total hydrocarbons in the exhaust gas of an automobile which is driven by the gasoline after the temperature of the main catalyst rises and the purification performance is exhibited. 14. The fuel according to claim 11, wherein the fuel is used at the start of engine startup, and the gasoline is gradually mixed with the fuel until the temperature of the main catalyst rises and purification performance is exhibited. A method for reducing total hydrocarbons in the exhaust gas of an automobile which is driven by the gasoline after the main catalyst exhibits the purification performance by increasing the ratio. 15. The fuel according to claim 12, wherein the fuel is used when starting the engine, and the gasoline is gradually mixed with the fuel until the temperature of the main catalyst rises and the purification performance is exhibited. A method for reducing total hydrocarbons in the exhaust gas of an automobile which is driven by the gasoline after the main catalyst exhibits the purification performance by increasing the ratio.