JP2001304031A - Device for measuring amount of hydrogen in exhaust gas and exhaust gas emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen detection device for an internal combustion engine for efficiently purifying NOx by improving fuel economy of the internal combustion engine, when NOx absorbed in an NOx absorbing catalyst is purified serving hydrogen generated by the catalyst as reducing agent, and to provide an exhaust gas emission control system using it. SOLUTION: A hydrogen amount estimating device disposed in an exhaust passage of the internal combustion engine is provided with the catalyst having a function for generating hydrogen from hydrocarbons in exhaust gas, methane sensors disposed on an upstream side and a downstream side of the exhaust passage of the catalyst, and calculating means for calculating methane consumption before and after passing the catalyst, and for estimating an amount of hydrogen delivered to the downstream side of the catalyst. The exhaust gas emission control system is provided with the hydrogen amount estimating device, and is constituted by arranging an NOx absorbing catalyst on the downstream side of the methane sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the amount of hydrogen in exhaust gas and an exhaust gas purifying system, and more particularly to a lean burn exhaust gas discharged from a lean burn engine or the like using hydrogen as a reducing agent. The present invention relates to a device for measuring the amount of hydrogen in exhaust gas and an exhaust gas purification system capable of efficiently purifying nitrogen oxides (NOx) in gas.

[0002]

2. Description of the Related Art In general, when an internal combustion engine is operated leaner than a stoichiometric air-fuel ratio, it is difficult to purify NOx discharged with a conventional three-way catalyst. Therefore, N having a NOx adsorbent that adsorbs NOx discharged during lean operation is provided.
An Ox adsorption catalyst is used. This NOx adsorption catalyst converts NOx discharged when the air-fuel ratio is set to lean to N
It is adsorbed by the Ox adsorbent, the air-fuel ratio is set to the stoichiometric air-fuel ratio or richer, the oxygen concentration in the exhaust gas is low, and hydrocarbons (HC) and carbon monoxide (CO) as reducing agents are removed. When the amount is large, the adsorbed NOx is released for purification.

However, the NOx contained in the NOx adsorption catalyst
The adsorbent has a limit in the amount of NOx that can be adsorbed. If the air-fuel ratio is set to lean and the operation is continued for a long time, the non-adsorbed NOx is discharged to the atmosphere as it is. For this reason, an air-fuel ratio control method in which the above-described lean operation and rich operation are repeatedly performed as appropriate is employed. Further, in order to release and purify the NOx adsorbed by the NOx adsorbent, HC and CO having an equivalent ratio to the adsorbed NOx are required.

[0004]

However, in the above-described air-fuel ratio control method, a rich operation is performed to supply more HC and CO in order to release and purify NOx adsorbed by the NOx adsorbent. Therefore, there is a problem that fuel consumption of the internal combustion engine is increased and fuel consumption is deteriorated.

[0005] In addition, for example, when a three-way catalyst is arranged upstream of the NOx adsorption catalyst, HC and CO supplied during operation at a stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio are reduced by the three-way catalyst arranged upstream. Since it is purified and the supply of the reducing agent to the NOx adsorbed by the NOx adsorbent is less than the equivalence ratio, the NOx is released, but the purification is incomplete and the NOx is discharged into the atmosphere. . Therefore, when a three-way catalyst is disposed upstream of an exhaust gas purification catalyst having a function of adsorbing NOx lean and releasing NOx at a stoichiometric air-fuel ratio to rich, a larger amount of fuel is supplied to increase the air-fuel ratio. It must be enriched, and the above-described deterioration in fuel efficiency is further promoted.

[0006] In addition to the above HC and CO, NOx
Hydrogen in exhaust gas can be used as a reducing agent. For example, it is conceivable to generate a large amount of hydrogen by a partial oxidation reaction and a steam reforming reaction and supply the hydrogen to the exhaust gas to purify NOx. Here, the partial oxidation reaction is a reaction in which a hydrocarbon and oxygen are reacted at a high temperature to generate a mixed gas of CO and H ₂ , and is expressed by the following formula: 2CH ₄ + O ₂ → 2CO + 4H ₂ . And 1 mole of hydrogen is produced from 1 mole of methane. The steam reforming reaction is represented by the following formula: CH ₄ + H ₂ O → CO + 3H ₂ , and 3 moles of hydrogen are produced from 1 mole of methane.

If the amount of hydrogen generated by the partial oxidation reaction can be known, the hydrogen can be supplied by temporarily increasing the air-fuel ratio when NOx is to be purified. Efficiency can be improved. However, since gasoline contains only a few percent of hydrogen, it usually contains only a small amount of hydrogen in the exhaust gas. Therefore, even if the amount of hydrogen in the exhaust gas is measured by a sensor or the like, it is directly measured. There is a problem that cannot be done.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to use NOx adsorbed on a NOx adsorption catalyst using hydrogen generated by the catalyst as a reducing agent. It is an object of the present invention to provide an apparatus for estimating the amount of hydrogen in exhaust gas and an exhaust gas purification system capable of improving the fuel efficiency of an internal combustion engine and purifying NOx efficiently when purifying the exhaust gas.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have noticed that hydrogen is generated by a partial oxidation reaction of methane and a steam reforming reaction. When the air-fuel ratio of the gas is made rich, the amount of hydrogen generated is estimated from the amount of CH ₄ generated from hydrocarbons in the exhaust gas, and the generated hydrogen is preferably used for NOx purification at an appropriate timing. By doing so, the inventors have found that the above-mentioned problems can be solved, and have completed the present invention.

That is, the apparatus for measuring the amount of hydrogen in exhaust gas according to the present invention is provided in an exhaust passage of an internal combustion engine and has a function of generating hydrogen from hydrocarbons in the exhaust gas. Or a first methane sensor and a second methane sensor that are installed on the upstream and downstream sides of a part of the exhaust flow path and measure the amount of methane in the gas;
The methane consumption before and after passing through the catalyst is calculated from the methane amount before passing through the catalyst and the methane amount after passing through the catalyst measured by the methane sensor, and the amount of hydrogen released downstream of the catalyst is calculated from the obtained methane consumption. Calculating means for estimating.

In a preferred embodiment of the hydrogen amount measuring apparatus according to the present invention, the catalyst has a methane generation catalyst section for generating methane from hydrocarbons and a hydrogen generation catalyst section for generating hydrogen from methane. And

Next, in the method for measuring the amount of hydrogen in exhaust gas according to the present invention, a catalyst for generating hydrogen from hydrocarbons in exhaust gas is installed in an exhaust passage of an internal combustion engine, and the exhaust gas removes the catalyst. It is characterized in that the amount of methane consumed during the passage is measured and the amount of hydrogen flowing out downstream of the catalyst is calculated from the amount of methane consumed.

Further, the exhaust gas purifying system of the present invention comprises:
A catalyst that generates hydrogen from hydrocarbons in the exhaust gas is installed in the exhaust flow path of the internal combustion engine, and the amount of methane consumed when the exhaust gas passes through the catalyst is measured.
It is characterized in that the amount of hydrogen flowing out downstream of the catalyst is estimated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus for measuring the amount of hydrogen in exhaust gas according to the present invention will be described below in detail. As described above, the apparatus for estimating the amount of hydrogen in exhaust gas of the present invention includes a catalyst having a function of generating hydrogen from hydrocarbons in exhaust gas,
First and second methane sensors are arranged on the upstream and downstream sides of the exhaust passage, respectively.

The apparatus for measuring the amount of hydrogen in exhaust gas according to the present invention comprises:
Focusing on hydrogen, which is an exhaust gas component other than HC and CO discharged when the air-fuel ratio of the internal combustion engine is rich and can be a reducing agent, this hydrogen is used as a NOx reducing agent.
This is because the inventors have found that it is possible to purify water. That is, when the air-fuel ratio of the internal combustion engine is lean, the conventional exhaust gas purifying catalyst such as a three-way catalyst uses HC and C
O was almost purified and could not be used as a NOx reducing agent. At the same time as the exhaust gas is purified, hydrogen is generated by a partial oxidation reaction of hydrocarbons.
Reacts with O to form water. However, when the air-fuel ratio is temporarily made rich, the amount of hydrocarbons in the exhaust gas increases, and accordingly, the amount of generated hydrogen increases significantly. The generated hydrogen is, like the lean, CO 2 in the exhaust gas.
Reacts with water to form water, but the amount is small compared to the amount of generated hydrogen, and a large amount of hydrogen flows downstream and can be used as a NOx reducing agent.

At this time, according to the partial oxidation reaction, as shown in the above equation, 1 mol of hydrogen is produced from 1 mol of methane. Therefore, instead of directly measuring the produced hydrogen,
By measuring the amount of methane generated in the exhaust gas when the air-fuel ratio is made rich, the amount of generated hydrogen can be estimated. In other words, the apparatus for measuring the amount of hydrogen in exhaust gas of the present invention includes a methane sensor arranged in an exhaust passage before and after a catalyst having a function of generating hydrogen by a partial oxidation reaction, such as a three-way catalyst. The change in the amount of methane before and after purification by the catalyst for use is measured, and the amount of hydrogen generated can be calculated from the change.

Further, as an example of the catalyst having a function of generating hydrogen from the exhaust gas, there is a three-way catalyst as described above. The three-way catalyst is, for example, a catalyst in which noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rd) are supported on alumina, and includes carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide. (NOx) can be purified together by catalytic reaction, and the purification mechanism is complicated. However, during purification, the ability to generate hydrogen from hydrocarbons and the like discharged from the internal combustion engine due to partial oxidation reaction and the like is reduced. Have.

Further, the catalyst having a function of generating hydrogen from the exhaust gas has a methane generating catalyst section for generating methane from hydrocarbons in the exhaust gas, and a hydrogen generating catalyst section for generating hydrogen from methane. Are preferred, and these 2
The two catalysts are preferably arranged in the order of a methane generation catalyst section on the upstream side of the exhaust flow path and a hydrogen generation catalyst section on the downstream side.
By arranging in this order, high molecular hydrocarbons can be cut into low molecular hydrocarbons by a cracking reaction to generate methane, and then hydrogen can be efficiently generated from methane by a partial oxidation reaction. Examples of the catalyst component of the methane generation catalyst section include silica-alumina and zeolite. The catalyst component of the hydrogen generation catalyst section includes Pd.
Cerium oxide, zirconium oxide, nickel compounds, etc., which carry the same, and these components are preferably contained in appropriate amounts.

The methane-producing catalyst section and the hydrogen-producing catalyst section are not particularly limited to the tandem arrangement as described above. A catalyst carrier is coated with the catalyst component of the hydrogen-producing catalyst section. The catalyst component of the methane generation catalyst section may be laminated thereon. The catalyst carrier is preferably a monolithic catalyst carrier, for example, a honeycomb carrier.
As the honeycomb material, a cordierite material such as ceramics is generally used. However, the present invention is not limited to this, and a honeycomb material made of a ferritic stainless steel metal material may be used, and the catalyst component powder itself may be formed into a honeycomb shape.

Further, the first and second methane sensors may include:
It is preferable that the hydrogen generation catalyst section is disposed in the exhaust passages on the upstream side and the downstream side of the hydrogen generation catalyst section. In the hydrogen amount estimation device of the present invention, as described above, not the hydrogen itself,
Since it is determined whether or not hydrogen has been generated by detecting methane, if sensors are arranged before and after only the hydrogen generation catalyst section, it is possible to estimate the amount of hydrogen generated from the amount of methane generated. it can.

The amount of hydrogen generated from the amount of methane generated is determined before and after the passage of the catalyst from the amounts of methane before and after the catalyst measured by the first and second methane sensors. Is calculated by a calculating means for calculating the amount of hydrogen released downstream of the catalyst from the obtained methane consumption.
That is, the methane sensor is preferably connected to an ECU and operated by using the relationship between methane and hydrogen in the above equation. However, the present invention is not limited to this, and other means may be used. .

Further, the hydrogen measuring device of the present invention preferably generates hydrogen when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich. Although it is possible that hydrogen is generated even when lean,
Particularly, in the range from the stoichiometric air-fuel ratio to rich, a large amount of fuel such as gasoline is supplied, so that the amount of hydrocarbons in the exhaust gas increases accordingly, and as a result, a large amount of hydrogen can be generated.

Next, the method for measuring the amount of hydrogen in exhaust gas according to the present invention will be described in detail. The method for measuring the amount of hydrogen in exhaust gas according to the present invention includes the steps of: installing a catalyst for generating hydrogen from hydrocarbons in exhaust gas in an exhaust passage of an internal combustion engine, and consuming methane when the exhaust gas passes through the catalyst. The amount of hydrogen is measured, and the amount of hydrogen flowing out downstream of the catalyst is calculated from the amount of methane consumed. That is, as described above, a method in which the first and second methane sensors are arranged before and after the hydrogen generation catalyst, the methane consumption is measured, and the amount of hydrogen flowing out downstream of the catalyst is calculated. The method is not limited to this method, and the hydrogen amount estimating method may be implemented using another device or the like.

Next, the exhaust gas purification system of the present invention will be described in detail. The exhaust gas purifying system of the present invention is an exhaust gas purifying system provided with a hydrogen amount measuring device, wherein a NOx adsorption catalyst for purifying nitrogen oxides is arranged downstream of the second methane sensor.

As described above, the above-mentioned hydrogen amount measuring device includes:
Since a catalyst having a function of generating hydrogen is provided, NOx can be reduced and purified by a NOx adsorption catalyst arranged on the downstream side using hydrogen generated by the catalyst as a reducing agent. In particular, during the lean operation, even if hydrogen is generated from methane in the exhaust gas in the hydrogen generation catalyst,
It is consumed for purification of exhaust gas components or becomes water,
Hydrogen generated in the downstream NOx adsorption catalyst is hardly supplied, or is supplied only slightly. During the rich operation, fuel such as gasoline supplied to the internal combustion engine increases, hydrocarbons in the exhaust gas also increase, cracking occurs in the hydrogen generation catalyst, and a large amount of methane is generated. Therefore, since hydrogen is generated in a larger amount than is consumed by the hydrogen generation catalyst, most of the generated hydrogen is supplied to the NOx adsorption catalyst on the downstream side.

In order to efficiently consume a large amount of hydrogen supplied as a reducing agent by the NOx adsorption catalyst during the rich operation, the NOx adsorption catalyst adsorbs NOx when the inflowing exhaust gas has a lean air-fuel ratio. Preferably, the catalyst is a NOx adsorption and purification catalyst that releases and purifies NOx when the stoichiometric air-fuel ratio is rich, and preferably contains a NOx adsorption component and a NOx purification component. Examples of the NOx adsorbent include alkali metals, alkaline earth metals or rare earth elements and elements related to any combination thereof, especially oxides thereof. Specifically, potassium (K), sodium (Na) ), Alkali metals such as lithium (Li) and cesium (Cs) and their oxides, alkaline earth metals such as barium (Ba) and calcium (Ca) and their oxides, lanthanum (L
a) and rare earth elements such as yttrium (Y) and their oxides. In the present invention, two or more of these can be used in any combination. Also,
As a component for purifying NOx, a noble metal element such as Pt, Rh, or Rd, which is also used in a three-way catalyst, may be mentioned.

The NOx adsorbing catalyst has a limit in the amount of NOx that can be adsorbed. Therefore, if a certain amount is absorbed, the amount of NOx that cannot be adsorbed in the exhaust gas increases. Therefore, a NOx sensor for measuring the amount of NOx is added to the downstream side of the NOx adsorption catalyst, a measured NOx amount signal is transmitted to the calculating means of the hydrogen amount measuring device, and the amount of generated hydrogen is feedback-controlled. preferable. That is, the above NO
By measuring the amount of NOx in the exhaust gas that has passed through the x purification catalyst, it is possible to know the timing of switching to the rich operation, and by switching to the rich operation and supplying a large amount of hydrogen,
The absorbed NOx can be efficiently purified. Then, the NOx adsorbing catalyst can absorb NOx again. It is sufficient if it is possible to know whether or not the exhaust gas contains NOx that has not been adsorbed by the NOx adsorption catalyst. Therefore, the NOx sensor may be installed only on the downstream side of the NOx purification catalyst. . Further, the NOx adsorption amount of the NOx purification catalyst can also be detected by means for estimating the NOx saturated adsorption amount from the engine speed, temperature, and the like, and is not particularly limited to the above means.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The exhaust gas purifying system of the present invention will be described below in more detail with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of an internal combustion engine to which the exhaust gas purification system of the present invention is applied. In FIG. 1, reference numeral 1 denotes an internal combustion engine, 2 denotes a three-way catalyst, 3 denotes an H ₂ generation catalyst, 4 denotes a NOx adsorption catalyst, 5 and 6 denote first and second methane sensors, 7 denotes a NOx sensor, and 8 denotes an ECU. Show. The internal combustion engine 1 is connected to a three-way catalyst 2 via an exhaust manifold and an exhaust pipe, and methane sensors 4 and 5 are arranged in exhaust pipes before and after the H ₂ generation catalyst 3. Further, the NOx adsorption catalyst 4 is connected via an exhaust pipe, and a NOx sensor 7 is connected to the exhaust pipe behind the NOx adsorption catalyst 4.
Are arranged.

The exhaust gas discharged from the internal combustion engine 1 is supplied to the three-way catalyst 2 through an exhaust manifold and an exhaust pipe. The amount of methane contained in the exhaust gas that has passed through the three-way catalyst 2 is obtained by inputting the output voltage generated by the first methane sensor 5 to the ECU 8 as needed. Similarly, the amount of methane in the exhaust gas that has passed through the H ₂ generation catalyst 3 is determined by calculating the output voltage generated by the second methane sensor 6 by EC.
It is obtained by inputting to U8.

[0031] Then, NOx in the exhaust gas is adsorbed in the NOx trap catalyst 4 exhaust gas composition is disposed downstream of the three-way catalyst 2 and H ₂ generating catalyst 3 when the lean. The amount of NOx in the exhaust gas passing through the NOx adsorption catalyst 4 is obtained by inputting an output voltage generated by a NOx sensor 7 provided downstream of the NOx adsorption catalyst 4 to the ECU 8 and converting the output voltage. Further, when it is determined that the NOx amount in the exhaust gas exceeds a predetermined value, the ECU 8
The air-fuel ratio control state of the internal combustion engine is made rich, and hydrogen is generated from the rich exhaust gas flowing through the three-way catalyst 2 and the H ₂ generation catalyst 3. Then, the hydrogen generated by the three-way catalyst 2 and the H ₂ generation catalyst 3 is supplied to the NOx adsorption catalyst 4, and the NOx adsorbed when the air-fuel ratio control state of the internal combustion engine is lean.
Is released and purified.

FIG. 2 shows hydrogen supply and N in this embodiment.
It is a time flow chart which shows an example of Ox release purification. When the internal combustion engine of FIG. 1 is operating lean, NOx in the exhaust gas is adsorbed by the NOx purification catalyst 4.
Then, when the NOx absorption amount of the NOx adsorption catalyst 4 reaches the allowable value, NOx disposed downstream of the NOx adsorption catalyst 4
It is possible to know that the output voltage of the sensor 7 has increased and NOx has been released into the atmosphere. Therefore, the ECU 8
When it is determined that the output voltage of the NOx sensor 7 exceeds a certain threshold value, a command for enriching the air-fuel ratio of the exhaust gas is issued to each device that controls the air-fuel ratio in the internal combustion engine 1. Then, the exhaust gas whose air-fuel ratio is enriched flows into the three-way catalyst 2, and the HC component in the exhaust gas is partially oxidized to generate hydrogen.

The partially oxidized HC becomes an HC species having a small number of carbon atoms. In particular, the amount of methane at the outlet of the three-way catalyst 2 is larger than the amount of methane discharged from the internal combustion engine 1 as shown in the rich operation in FIG. Therefore, the three-way catalyst 2 when the exhaust gas of the internal combustion engine 1 is rich
By detecting the amount of methane at the outlet of the catalyst and the outlet of the H ₂ generation catalyst 3 with the methane sensors 5 and 6 by the ECU 7, it can be determined whether or not hydrogen is generated.

The three-way catalyst 2 and the H ₂ generation catalyst 3
Produced in the NOx adsorbing catalyst 4 flows into the NOx adsorbing catalyst 4, and the N2 absorbed by the NOx adsorbing catalyst 4 when the exhaust gas is lean
Releases and purifies Ox. When the NOx purification by hydrogen is performed, the NOx sensor 7 disposed downstream of the NOx adsorption catalyst 4
Is determined by the ECU 8, the ECU 8 makes the air-fuel ratio control of the internal combustion engine 1 lean again, and the NOx adsorption catalyst 4 adsorbs NOx. By repeating this operation, it becomes possible to purify NOx and eliminate the need for unnecessary enrichment, so that fuel efficiency can be improved.

FIG. 3 is a graph showing NO by hydrogen in the present embodiment.
6 is a flowchart showing an example of x purification determination, and shows a routine executed at a desired timing in the exhaust gas purification system of the present embodiment. The routine is executed by calculation in the hydrogen amount estimating apparatus according to the output voltage from the methane sensors 5, 6 and the NOx sensor 7 shown in FIG. In the figure, first, at step 101, it is determined whether or not the current air-fuel ratio of the internal combustion engine is lean. Step 102 if lean
If not, it is determined that the air-fuel ratio state is such that the NOx adsorbed by the NOx adsorption catalyst 4 is released and purified.

Next, at step 102, it is determined whether the NOx amount TNOx at the outlet of the NOx adsorption catalyst 4 has reached a certain threshold value. This is determined by the output voltage of the NOx sensor 7 arranged downstream of the NOx adsorption catalyst 4 being input to the ECU 8 and being subjected to AD conversion. TN
When it is determined that Ox has reached a certain threshold value TNOx1, the routine proceeds to step 103, and when it is determined that TNOx1 has not been reached, the operating state of the exhaust gas is maintained lean. Then, in step 102, TNO
When it is determined that x has exceeded the threshold value TNOx1, the hydrogen supply flag is turned on in step 103, and the air-fuel ratio of the exhaust gas of the internal combustion engine 1 is enriched.

Next, in step 104, the inlet of the amount of methane CH4IN of _{H 2} generating catalyst 3 whether low is determined than the amount of methane CH4OUT the outlet of _{H 2} generating catalyst 3. If CH4IN is lower than CH4OUT, H
It is determined that hydrogen has been generated in the _2- generation catalyst 3, and the routine proceeds to step 106, where CH4IN becomes CH4OUT.
If it is higher, the routine proceeds to step 105, where a command for further enrichment is given to the internal combustion engine 1. Step 106
It is determined whether or not the release and purification of the NOx absorbed by the NOx adsorption catalyst 4 has been completed. This is the threshold TN at which the NOx amount TNOx at the outlet of the NOx adsorption catalyst 4 is
It is determined based on whether it is lower than Ox2. TNOx is T
If it is lower than NOx2, the release and purification of the NOx absorbed by the NOx adsorption catalyst 4 is completed, it is determined that the NOx adsorption catalyst 4 has been regenerated to a state where it can adsorb NOx again, and the routine proceeds to step 107. When TNOx is higher than TNOx2, the state of hydrogen supply is maintained. And step 10
At 7, the hydrogen supply flag is turned off, the purification of NOx release by hydrogen supply is completed, and the exhaust gas air-fuel ratio of the internal combustion engine 1 becomes lean again. When TONx is higher than TNOx2, the state of hydrogen supply is maintained.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the disclosure of the present invention. In particular, when determining whether or not the NOx amount has reached a certain threshold value at the outlet of the NOx adsorption catalyst 4, a conventionally known means for estimating the NOx adsorption amount to the NOx adsorption catalyst may be used.

[0039]

As described above, according to the present invention,
Focusing on the fact that hydrogen is generated by the partial oxidation reaction of methane, when the air-fuel ratio of the exhaust gas is made rich, the amount of hydrogen generated from hydrocarbons in the exhaust gas is calculated, and the generated hydrogen is Preferably, it is used for NOx purification at an appropriate timing to improve the fuel efficiency of the internal combustion engine when purifying NOx absorbed by the NOx purification catalyst using hydrogen generated by the catalyst as a reducing agent. It is possible to provide a device for measuring the amount of hydrogen in exhaust gas and an exhaust gas purification system that can be efficiently purified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an internal combustion engine to which an exhaust gas purification system of the present invention is applied.

FIG. 2 is a time flowchart illustrating an example of hydrogen supply and NOx purification.

FIG. 3 is a flowchart illustrating an example of NOx purification determination using hydrogen, and illustrates a routine executed at a desired timing.

[Explanation of symbols]

1 internal combustion engine 2 three-way catalyst 3 H ₂ generating catalyst 4 NOx adsorbing catalyst 5 first methane sensor 6 second methane sensor 7 NOx sensor 8 ECU

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F01N 3/24 F01N 3/24 R 3/28 301C 3/28 301 F02D 41/04 305A F02D 41/04 305 41/14 310J 41/14 310 G01N 31/00 C G01N 31/00 31/10 31/10 31/12 Z 31/12 B01D 53/36 101A (72) Inventor Hiroyuki Kanasaka 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa-ken Address F-term in Nissan Motor Co., Ltd. (Reference) 2G042 AA01 BB02 CA01 DA03 FA04 FA08 3G084 AA04 BA09 DA02 DA10 EB11 FA28 3G091 AA12 AA17 AA28 AB01 AB03 AB06 AB09 BA14 BA15 BA19 BA33 CA19 CB02 DA01 DA02 DA03 DA01 DB10 FB10 EA12 FC02 GA06 GB01X GB02Y GB03Y GB04X GB04Y GB05W GB06W GB07W GB10X GB16X GB17X HA08 HA12 HA18 HA36 HA37 HA42 HA47 3G301 HA15 JA02 JA25 MA01 ND01 N E13 NE14 NE15 PD01A PD01Z 4D048 AA06 AB02 AB06 AB07 BA03Y BA06Y BA08Y BA10Y BA11Y BA19X BA30Y BA31Y BA33Y BA38Y BA39Y BA41Y BA42Y BB02 CC44 DA01 DA02 DA08 DA20 EA04

Claims (8)

[Claims] 1. A catalyst which is installed in an exhaust passage of an internal combustion engine and has a function of generating hydrogen from hydrocarbons in exhaust gas, and which is installed on the entire or a part of the catalyst on the upstream and downstream sides of the exhaust passage. A first methane sensor and a second methane sensor for measuring the amount of methane in the gas; and a methane amount before and after the catalyst passed through the catalyst measured by the first and second methane sensors. Calculating means for calculating the amount of methane before and after the passage, and calculating the amount of hydrogen released downstream of the catalyst from the obtained amount of methane consumption, a device for measuring the amount of hydrogen in exhaust gas, comprising: . 2. The hydrogen amount measurement device according to claim 1, wherein the catalyst has a methane generation catalyst unit that generates methane from hydrocarbons, and a hydrogen generation catalyst unit that generates hydrogen from methane. 3. The methane generation catalyst section is disposed upstream of the hydrogen generation catalyst section, and the first methane sensor and the second methane sensor are disposed upstream and downstream of the hydrogen generation catalyst section. 3. The hydrogen amount measuring device according to claim 2, wherein: 4. The hydrogen according to claim 1, wherein the catalyst generates hydrogen when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich. Quantity measuring device. 5. A catalyst for generating hydrogen from hydrocarbons in exhaust gas is provided in an exhaust passage of an internal combustion engine, and the amount of methane consumed when the exhaust gas passes through the catalyst is measured. A method for measuring the amount of hydrogen in exhaust gas, comprising calculating an amount of hydrogen flowing out downstream of the catalyst from the amount. 6. An exhaust gas purifying system comprising the hydrogen amount measuring device according to claim 1, wherein a nitrogen oxide is purified downstream of the second methane sensor. An exhaust gas purification system comprising a NOx adsorption catalyst. 7. The NOx storage / purification catalyst that absorbs nitrogen oxide when the air-fuel ratio of the inflowing exhaust gas is lean and releases and purifies nitrogen oxide when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich. The exhaust gas purification system according to claim 6, which is a catalyst. 8. A NOx sensor for measuring the amount of nitrogen oxides is added downstream of the NOx adsorption catalyst, and the measured NO
The exhaust gas purification system according to claim 6 or 7, wherein an x amount signal is transmitted to a calculation unit of the hydrogen amount measuring device, and the amount of generated hydrogen is feedback-controlled.