JPH02199214A - Engine exhaust gas purification device - Google Patents

Abstract

PURPOSE:To improve aldehyde group reducing effect with preventing heat deterioration of a secondary catalyst by leading exhaust gas of an engine body in the case that detected alcohol density is higher than a predetermined valve. CONSTITUTION:A first catalyst 19 for mainly purifying exhaust gas of gasoline fuel and a secondary catalyst 20 for mainly purifying exhaust gas of alcohol fuel are provided on the way of an exhaust pipe 18. Hereupon, an opening and closing valve 22 is controlled to be closed by a controller 23 under a state that alcohol density detected by an alcohol density sensor is over predetermined set valve. Consequently, aldehyde group mixed in the exhaust gas can be effectively purified by respectively leading the exhaust gas from an engine body 1 to the catalysts 19, 20. In case that the alcohol density is lower than predetermined set valve, the opening and closing valve 22 is controlled to be opened to detour the exhaust gas round the catalyst through a bypass passage 21 to prevent the catalyst from poisoning.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to cleaning exhaust gas from an engine that uses a mixed fuel of gasoline fuel and alcohol fuel, for example. Concerning improvement of purification equipment.

(Prior Art) In general, vehicles such as automobiles that use gasoline fuel are equipped with a catalytic converter formed by, for example, a three-way catalyst, in the middle of the exhaust path of the engine body, which converts exhaust gases discharged from the engine body. By passing through the inside of this catalytic converter, carbon monoxide and hydrocarbons in the exhaust gas are oxidized, and at the same time, nitrogen oxides (NOX) are reduced and purified.

By the way, for example, an engine main body that uses a mixed fuel of gasoline fuel and alcohol fuel has been considered, but the exhaust gas of this type of engine main body contains aldehyde produced by combustion of the alcohol fuel. This aldehyde is difficult to purify with a catalytic converter formed by a three-way catalyst, so as the alcohol concentration in the mixed fuel increases, the amount of aldehyde discharged to the outside increases, which increases the negative impact on the human body and the external environment. There is.

Therefore, measures such as increasing the catalyst capacity, increasing the amount of precious metals supported, and moving the catalyst closer to the engine body have been considered, but increasing the catalyst capacity and increasing the amount of precious metals supported increases costs and However, there is a problem that the aldehyde purification effect is low, and when the catalyst is placed close to the engine body, there are problems such as a decrease in output due to increased back pressure and a decrease in the durability of the catalyst.

Furthermore, it has been confirmed that the base metal catalyst is more effective as a means for reducing aldehydes than a catalytic converter formed by a three-way catalyst. however,
When this base metal catalyst is used in a gasoline engine, there is a problem in that the base metal catalyst is easily poisoned by S02 and the like produced from sulfur contained in gasoline fuel. Furthermore, this base metal catalyst has inferior NOx (nitrogen oxide) purification properties compared to noble metal catalysts, and is also susceptible to thermal deterioration, so it has not been used as an exhaust gas purification device for engines.

(Problem to be Solved by the Invention) Aldehydes mixed in the exhaust gas from an engine that uses a mixed fuel of gasoline fuel and alcohol fuel are difficult to purify using a catalytic converter formed by a three-way catalyst. There has been a problem in that as the alcohol concentration in the fuel increases, the amount of aldehyde discharged to the outside increases, increasing the negative impact on the human body and the external environment. Furthermore, when using a base metal catalyst which is highly effective as a means of reducing aldehydes, there is a problem that the base metal catalyst is easily poisoned by S02 etc. generated from the sulfur contained in gasoline fuel. At the same time, this base metal catalyst produces NOx (nitrogen oxides).
In addition to having inferior purification properties compared to precious metal catalysts, they also suffered from thermal deterioration and quality problems.

This invention was made in view of the above-mentioned circumstances, and aims to increase the effect of reducing aldehydes by using a second catalyst that mainly purifies the exhaust gas of alcohol fuel when the alcohol concentration in the fuel is high. In addition, when the alcohol concentration in the fuel is low, the second catalyst can be effectively protected, preventing thermal deterioration of the second catalyst and improving the durability of the engine. The object of the present invention is to provide an exhaust gas purification device.

[Structure of the Invention] (Means for Solving the Problem) The invention as claimed in claim (1) provides a first catalyst that mainly purifies exhaust gas of gasoline fuel and a catalyst that mainly purifies alcohol fuel in the middle of the exhaust path of the engine body. A second catalyst for purifying fuel exhaust gas is provided, a bypass passage connected in parallel with the second catalyst, and an on-off valve for opening and closing this bypass passage. An alcohol concentration detection means for detecting the alcohol concentration in the alcohol and a controller for opening the on-off valve when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value are provided.

The invention of claim (2) also provides a first catalyst that mainly purifies exhaust gas of gasoline fuel in the middle of the exhaust path of the engine body, and a downstream side of this first catalyst that mainly purifies exhaust gas of alcohol fuel. A second catalyst for purifying gas is provided, a bypass passage connected in parallel with the second catalyst and an on-off valve for opening and closing this bypass passage are provided in the exhaust passage of the engine body, respectively. An alcohol concentration detection means for detecting the alcohol concentration in the fuel and a controller for opening the on-off valve when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value are provided.

Furthermore, the invention of claim (3) uses a base metal catalyst containing silver as a main component as the second catalyst of claim (1) or (2). be.

(Function) In the invention of claim 1, when the alcohol concentration detected by the alcohol concentration detection means is higher than a predetermined set value, the on-off valve is closed, and the exhaust gas from the engine body is transferred to the first catalyst. By guiding the aldehydes mixed in the exhaust gas into the second and second catalysts, the aldehydes mixed in the exhaust gas are introduced into the second catalyst.
In addition, when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value, the on-off valve is opened to direct the exhaust gas from the engine body into the catalyst in section 1. By bypassing the second catalyst through the bypass passage, the second catalyst is prevented from being poisoned by S02 generated from sulfur in gasoline fuel, and its durability is improved. This is what I did.

Furthermore, in the invention of claim (2), a second catalyst that mainly purifies exhaust gas of alcohol fuel is disposed downstream of a first catalyst that purifies exhaust gas of gasoline fuel. , heat from the engine body side is prevented from being directly transferred to the second catalyst, thereby preventing thermal deterioration of the second catalyst.

Furthermore, in the invention of claim (3), the second catalyst of claim (1) or (2) is formed of a base metal catalyst containing silver as a main component. Accordingly, the effect of purifying aldehydes by the second catalyst, which mainly purifies exhaust gas of alcohol fuel, is further enhanced.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 schematically shows the overall structure of an exhaust gas purification device for a vehicle engine such as an automobile. 1st
In the figure, 1 is an engine main body, 2 is an intake pipe of the engine main body 1, and 3 is an exhaust pipe of the engine main body 1. In this case, the engine main body 1 is formed with a number of cylinders 4. Furthermore, an intake boat 5 and an exhaust port 6 for each cylinder 4 are formed in the cylinder head 1a of the engine body 1, respectively.

The intake boat 5 and the exhaust port 6 are opened and closed by an intake valve 7 and an exhaust valve 8, respectively.

Further, the intake pipe line 2 of the engine body 1 is formed by connecting an intake pipe 9 disposed on the upstream side and an intake manifold (intake manifold) 10 disposed on the downstream side.
Each branch pipe of the intake manifold 10 is connected to each intake boat 5 of the cylinder head la, respectively. The intake pipe 9 of the intake pipe line 2, the intake manifold 10, and the intake boat 5 in the cylinder head la...
The intake passage of the engine body 1 is formed by the above.

Furthermore, a surge tank 11 is connected in the middle of the intake pipe 9.

Furthermore, fuel injection valves 12 of a fuel injection device are connected to each branch pipe of the intake manifold 10, respectively. One end of a fuel supply pipe 13 is connected to each of these fuel injection valves 12 . Further, the other ends of these fuel supply pipes 13 are connected to a fuel tank 15 via a fuel pump 14.

This fuel tank 15 contains a mixed fuel of gasoline fuel and alcohol fuel, for example, methyl alcohol. When the engine body 1 is in operation, as the fuel pump 14 is driven, a mixed fuel of gasoline fuel and alcohol fuel in the fuel link 15 is supplied via the fuel supply pipe 13, and from each fuel injection valve 12 to the intake manifold 10. It is designed to be injected into each branch pipe. Further, an alcohol concentration sensor (alcohol concentration detection means) 16 is installed in the fuel supply pipe 13 to detect the concentration of alcohol in the mixed fuel. In this case, the alcohol concentration sensor 16 is, for example, an optical type in which a light source and a light receiving element are disposed in the mixed fuel, and the refractive index of light changes depending on the value of the mixture ratio, or it is determined by the fuel composition. It may be of a dielectric constant type that determines the mixture ratio from a change in the dielectric constant of the mixed fuel, or of a type that determines the alcohol concentration from the magnitude of a feedback learning correction coefficient for the basic injection amount.

On the other hand, the exhaust pipe line 3 of the engine body 1 is formed by connecting an exhaust manifold (exhaust manifold) 17 disposed on the upstream side and an exhaust pipe 18 disposed on the downstream side. Each branch pipe is connected to the exhaust port 6 of each cylinder 4 of the cylinder head 1a, respectively.

The exhaust port 6 in the cylinder head la and the exhaust manifold 17 and exhaust pipe 18 of the exhaust pipe line 3 form an exhaust passage of the engine body 1. Further, in the middle of this exhaust pipe 18, there is a first catalyst 19 that mainly purifies exhaust gas of gasoline fuel, and downstream of this first catalyst 19, there is a second catalyst that mainly purifies exhaust gas of alcohol fuel. 20 are provided respectively. In this case, the first catalyst 19 is formed of, for example, a three-way catalyst, and the second catalyst 20 is formed of a base metal catalyst containing silver as a main component. Further, the exhaust pipe 18 is provided with a bypass passage 21 connected in parallel with the second catalyst 20 and an on-off valve 22 for opening and closing the bypass passage 21. This opening/closing valve 22 is of a butterfly valve type, and is connected to a controller 23 formed by, for example, a microcomputer and its peripheral circuitry, and its opening/closing operation is controlled by control signals from this controller 23. .

The controller 23 also includes an alcohol concentration sensor 16 disposed in the fuel supply pipe 13 , a throttle position sensor 25 for detecting the opening degree of the throttle valve 24 disposed in the intake pipe 9 , and a throttle position sensor 25 for detecting the opening degree of the throttle valve 24 disposed in the intake pipe 9 . An intake pressure sensor 26 detects the intake pressure, a rotation speed sensor 27 detects the rotation speed of the engine body 1, a water temperature sensor 28 detects the cooling water temperature of the engine body 1, and detects the oxygen concentration in the exhaust gas in the exhaust manifold 17. Each sensor such as the 02 concentration sensor 29 and the fuel injection valve 12 are connected to each other. The controller 23 controls the opening/closing operation of the on-off valve 22 according to the alcohol concentration detected by the alcohol concentration sensor 16, and the alcohol concentration α detected by the alcohol concentration sensor 16 is set to a predetermined set value. The on-off valve 22 is opened in a state of α0 or less.

Next, the operation of the above configuration will be explained with reference to the flowchart of FIG. 2.

First, while the engine body 1 is operating, detection signals from each sensor are input into the controller 23, and based on the detection signal from the alcohol concentration sensor 16, the alcohol concentration α
is loaded. This detected alcohol concentration α is then compared with a set value α0 stored in the controller 23 in advance.

Here, in the case of α≧α0, the on-off valve 22 is operated to close by the controller 23 as shown by the solid line in FIG.
Bypass passage 21 is closed.

Therefore, in this case, exhaust gas from the engine body 1 is first introduced into the first catalyst 19 formed by a three-way catalyst, and carbon monoxide and hydrocarbons produced by combustion of gasoline fuel components are oxidized. At the same time, nitrogen oxides (NOx) are reduced and purified. Further, the exhaust gas that has passed through the first catalyst 19 is then guided into the second catalyst 20 formed by a base metal catalyst, and the aldehydes mixed in this exhaust gas are transferred to the second catalyst 20. 20 is effectively purified.

In addition, when α is α0, the on-off valve 22 is opened by the controller 23 as shown by the imaginary line in FIG.
Bypass passage 21 is opened.

Therefore, in this case, exhaust gas from the engine body 1 is introduced into the first catalyst 19 formed by a three-way catalyst, and carbon monoxide and hydrocarbons produced by combustion of gasoline fuel components are oxidized. At the same time, nitrogen oxides (NOX) are reduced and purified. Furthermore, the exhaust gas that has passed through the first catalyst 19 is then discharged to the outside through the bypass passage 21 . Therefore, in this case, the exhaust gas from the engine body 1 is guided only into the first catalyst 19 and passed through the bypass passage 21 to the second catalyst.
Since the second catalyst 20 can be bypassed, the second catalyst 20 can be prevented from being poisoned by S02 generated from sulfur in the gasoline fuel, and durability can be improved. Note that α0 is set to such an extent that the amount of aldehydes generated by combustion of alcohol fuel is sufficiently small, and the aldehydes generated when α is less than α0 are the first ones formed by the three-way catalyst. The catalyst 19 alone is sufficient for purification.

Therefore, in the above configuration, when the alcohol concentration α detected by the alcohol concentration sensor 16 is higher than the predetermined set value α0, the on-off valve 22 is closed by the controller 23, and the exhaust gas from the engine body 1 is closed. Since the gas is introduced into the first catalyst 19 and the second catalyst 20, the aldehydes mixed in the exhaust gas can be effectively purified by the second catalyst 20, and the alcohol concentration sensor The alcohol concentration α stamped by No. 16 is the predetermined set value α. In the following cases, the controller 23 opens the on-off valve 22 to guide exhaust gas from the engine body 1 only into the first catalyst 19 and bypass the second catalyst 20 via the bypass passage 21. Therefore, the second catalyst 20 can be prevented from being poisoned by S02 generated from sulfur in the gasoline fuel, and durability can be improved. Further, since the second catalyst 20 that mainly purifies the exhaust gas of alcohol fuel is disposed downstream of the first catalyst 19 that mainly purifies the exhaust gas of gasoline fuel,
It is possible to prevent heat from the engine body 1 side from being directly transferred to the second catalyst 20, and thermal deterioration of the second catalyst 20 can be prevented. Furthermore, since a base metal catalyst containing silver as a main component was used as the second catalyst 20,
Second catalyst 2 that mainly purifies exhaust gas of alcohol fuel
The purification effect of aldehydes by 0 can be further enhanced.

Note that this invention is not limited to the above embodiments. For example, in the above embodiment, a butterfly valve type on-off valve 22 for opening and closing the bypass passage 21 is shown, but a poppet valve type on-off valve 31 may be provided as shown in FIG. .

Further, in the above embodiment, the fuel tank 15 contains a mixed fuel of gasoline fuel and alcohol fuel, for example, methyl alcohol, and when the engine main body 1 is in operation, the gasoline fuel in the fuel tank 15 is mixed with the fuel pump 14 when the engine body 1 is in operation. Although a configuration is shown in which the mixed fuel with alcohol fuel is supplied through the fuel supply pipe 13 and injected from each fuel injection valve 12 into each branch pipe of the intake manifold 10, it is possible to A dual fuel type configuration may be used in which the fuel is supplied via an independent fuel supply path.

Furthermore, it goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] According to the invention of claim (1), a first catalyst that purifies exhaust gas mainly of gasoline fuel and a first catalyst that purifies exhaust gas mainly of alcohol fuel are provided in the middle of the exhaust path of the engine body. a second catalyst, a bypass passage connected in parallel with the second catalyst, and an on-off valve for opening and closing the bypass passage, and detecting the alcohol concentration in the fuel of the engine body. An alcohol concentration detection means and a controller that opens the on-off valve when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value are provided, so that when the alcohol concentration is higher than the predetermined set value, By guiding the exhaust gas from the engine body into the first catalyst and the second catalyst, the aldehydes mixed in the exhaust gas can be effectively purified by the second catalyst, and When the alcohol concentration is below a predetermined set value, the on-off valve is opened to guide exhaust gas from the engine body only into the first catalyst and bypass the second catalyst via the bypass passage. It is possible to prevent the second catalyst from being poisoned by S02 generated from sulfur in gasoline fuel, thereby improving durability.

According to the invention of claim (2), a first catalyst for mainly purifying exhaust gas of gasoline fuel is provided in the middle of the exhaust path of the engine body, and a first catalyst for mainly purifying exhaust gas of gasoline fuel is provided on the downstream side of the first catalyst. A second catalyst for purifying fuel exhaust gas is provided, and an opening/closing device for opening and closing the inlet passage and this bypass passage is connected in parallel with the second catalyst in the exhaust passage of the engine body. Each valve is provided with an alcohol concentration detection means for detecting the alcohol concentration in the fuel in the engine body, and a controller that opens the on-off valve when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value. Since we have set up each
It is possible to prevent heat from the engine main body side from being directly transferred to the second catalyst, thereby preventing thermal deterioration of the second catalyst.

Furthermore, according to the invention of claim No. (3), claim No.
) or (2), a base metal catalyst containing silver as a main component was used, so the second catalyst mainly purifies alcohol fuel exhaust gas.
The effect of purifying aldehydes by the catalyst can be further enhanced.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram of the entire engine exhaust gas purification device, FIG. 2 is a flowchart for explaining the operation, and FIG. 3 is a flow chart for explaining the operation. FIG. 2 is a schematic configuration diagram of main parts showing another embodiment. 1... Engine body, 3... Exhaust pipe line, 16...
Alcohol concentration sensor (alcohol concentration detection means), 1
9...First catalyst, 20...Second catalyst, 21...
・Bypass passage, 22.31... Opening/closing valve, 23...
controller. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (3)

[Claims] (1) A first catalyst that mainly purifies exhaust gas of gasoline fuel and a second catalyst that mainly purifies exhaust gas of alcohol fuel are respectively arranged in the middle of the exhaust path of the engine body,
A bypass passage connected in parallel with the second catalyst and an on-off valve for opening and closing the bypass passage are provided, and an alcohol concentration detection means for detecting the alcohol concentration in the fuel in the engine body, and this alcohol concentration detection means An exhaust gas purification device for an engine, characterized in that a controller is provided for opening the on-off valve when the alcohol concentration detected by the above is below a predetermined set value. (2) A first catalyst that mainly purifies exhaust gas from gasoline fuel is installed in the middle of the exhaust path of the engine body, and a second catalyst that mainly purifies exhaust gas from alcohol fuel is placed downstream of this first catalyst. A bypass passage connected in parallel with the second catalyst in the exhaust passage of the engine main body, and an on-off valve for opening and closing the bypass passage are provided respectively, and the alcohol concentration in the fuel of the engine main body is An engine exhaust gas purification system comprising an alcohol concentration detection means for detecting alcohol concentration and a controller for opening the on-off valve when the alcohol concentration detected by the alcohol concentration detection means is below a predetermined set value. Device. (3) The engine exhaust gas purification device according to claim (1) or (2), wherein the second catalyst is formed of a base metal catalyst containing silver as a main component. .