JP2000179335A - Exhaust-gas processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust-gas processing apparatus capable of achieving a high NOx conversion ratio regardless of properties of fuel applied as a reducing agent. SOLUTION: This exhaust-gas processing apparatus includes a NOx catalyst 6 inserted in an exhaust pipe 4 of an engine 1 for purifying an exhaust gas, and a nozzle (reducing-agent supplying means) 26 for supplying a reducing agent to the NOx catalyst 6. The exhaust-gas processing apparatus further includes an operating-state detecting means for detecting an operating state of the engine 1, and a property detecting means 25 for detecting a property of the reducing agent which is supplied to the NOx catalyst 6. The amount of reducing agent supplied to the NOx catalyst 6 is controlled according to the detected operating state and the property of the reducing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, nitrogen oxides emitted from a diesel engine (hereinafter, referred to as NO _x) it relates to an exhaust gas treatment device for purifying.

[0002]

2. Description of the Related Art As a conventional exhaust gas treatment apparatus, there is an apparatus that supplies a reducing agent by a post injection (hereinafter, referred to as a post injection) from a common rail type injection system according to an operating condition of an internal combustion engine from a catalyst inlet ( JP-A-8-74561
Reference).

[0003]

However, such a conventional exhaust gas processing apparatus has the following problems. (1) maximize the _the NO _x reduction capability of the catalyst HC (hydrocarbon-based) species depends catalyst. When a different HC species is given as the reducing agent, the NO _x purification rate decreases. (2) As shown in FIG. 19, when the property of the fuel changes, the content of the above-mentioned effective HC species naturally changes, so that when a different kind of fuel is supplied as the reducing agent of the NO _x catalyst, The amount of fuel as a reducing agent required to obtain the maximum NO _x conversion varies. For example, as shown in FIG.
In the case of the catalyst species is effective as a reducing agent, when giving the light fuel shown in FIG. 19 as a reducing agent, to obtain the same NO _x reduction in an amount less than the standard fuel. Conversely, if the standard fuel is not supplied more than the light fuel, the same NO _x
No reduction effect is obtained. From the fact that, even when supplied to the catalyst as a reducing agent a certain amount of fuel irrespective of the nature of the fuel, there is a problem that expected the NO _x reduction performance can not be expected. The present invention has been made in view of the above problems, regardless of the property of the fuel supplied as a reducing agent, is intended to obtain a high NO _x conversion.

[0004]

According to a first aspect of the present invention, a catalyst is provided in an exhaust passage of an internal combustion engine to purify exhaust gas, and the catalyst has a reducing agent. An exhaust gas treatment device having a reducing agent supply means for supplying the catalyst, comprising: an operating state detecting means for detecting an operating state of the internal combustion engine; and a property detecting means for detecting a property of the reducing agent supplied to the catalyst. The amount of the reducing agent supplied to the catalyst is controlled in accordance with the operating state and the properties of the reducing agent. The invention described in claim 2 is claim 1
In the exhaust gas treatment device described above, the supply amount of the reducing agent is reduced when the fuel is determined to be lighter than the reference fuel. According to a third aspect of the present invention, in the exhaust gas treatment apparatus according to the first or second aspect, the reducing agent uses fuel of an internal combustion engine, and the supply of the reducing agent is performed by a post-injection using a common rail fuel injection system, a unit injector, or the like. The fuel injection is performed during the expansion stroke or the exhaust stroke. According to a fourth aspect of the present invention, in the exhaust gas processing apparatus of the third aspect, a fuel injection period when fuel is injected in the expansion stroke is corrected according to a property of the fuel. According to a fifth aspect of the present invention, in the exhaust gas processing apparatus of the third or fourth aspect, a fuel injection amount when fuel is injected during the expansion stroke is corrected according to an actual EGR rate.

[0005]

According to the first aspect of the present invention, the performance of the catalyst can be maximized by controlling the amount of the reducing agent provided depending on the properties of the reducing agent. In the invention according to claim 2, since a light reducing agent having a small C number is effective in a copper-based catalyst,
It is possible also to reduction of the reducing agent supply amount of the target is achievable goals of the NO _x reduction performance, to increase the supply interval of the reducing agent if the nature of the reducing agent is determined to be light . In the third aspect of the present invention, attention has been paid to the fact that the properties of the fuel are closely related to the kinematic viscosity, and that the lighter the fuel, the higher the proportion of the HC species having a smaller C number and the lower the kinematic viscosity. Thus as fuel lighter consists may post injection amount required is small, by increasing or decreasing the post injection amount in accordance with the nature of the detected fuel, and can be always exhibit the performance of the NO _x catalyst . In addition, since the injection amount can be controlled to the minimum with respect to the required NO _x reduction performance, it is possible to minimize fuel consumption deterioration. According to the fourth aspect of the present invention, when the fuel properties of the common rail type fuel injection system change, the kinematic viscosity of the fuel changes as shown in FIG. 2 to change the injection rate of the nozzle. For the injection of the amount, a difference occurs between the target injection amount and the actual injection amount. Therefore, by correcting the solenoid valve energization time of the nozzle for injecting the target post injection amount according to the fuel property and the fuel temperature (actual kinematic viscosity), the post
The injection amount can be accurately controlled. According to a fifth aspect of the present invention, in addition to the second aspect of the invention, when the target EGR rate changes from a warm state to a cold state, the space velocity SV of the catalyst (exhaust gas flow rate / catalyst capacity) changes. When the speed SV changes, the NO _x reduction performance also changes. Therefore, by controlling the post injection amount according to the actual space speed SV of the catalyst, the NO _x
x It is possible to bring out the performance of the catalyst.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) Embodiment 1 corresponds to the first aspect of the present invention. FIG. 1 is a diagram illustrating the configuration of the first embodiment. In the figure, 1 is the engine, 8 common rail fuel injection system, the 5 EGR valve, 2 an intake pipe, the exhaust manifold 3, the fourth exhaust pipe, 6 is the NO _x catalyst, 7 is an exhaust temperature sensor. The EGR valve 5 is interposed in a passage connecting the exhaust manifold 3 and the intake pipe 2. FIG. 3 is a diagram of a fuel injection system, 9 is an accelerator opening sensor, 10
Denotes a crank angle sensor, and 11 denotes a cam angle sensor, which controls the injection timing and the injection amount based on the information. 12 is a fuel temperature sensor, 14 is a pressure pump, and 13 is a control valve for controlling the amount of fuel pumped to the common rail 15. Reference numeral 21 denotes a check valve for preventing the pressure-fed fuel from returning. Common rail 1
5 controls the rail pressure from the rail pressure of the common rail detected by the rail pressure sensor 20 and the control valve 23 for controlling the amount of fuel released from the rail and the pressure pump 14. Reference numeral 19 denotes a nozzle capable of injecting an arbitrary amount of fuel at an arbitrary time by opening and closing the 16 electromagnetic valves. All of these controls are performed by 22 control units. In addition, 17 is a pressure feed plunger and 18 is a fuel tank. In FIG. 1, reference numeral 24 denotes a reducing agent tank for storing the reducing agent, and reference numeral 25 denotes a property determining means (specific gravity meter or the like) for determining the property of the reducing agent. The reducing agent is supplied from nozzles 26 serving as reducing agent supply means.

FIG. 4 is a control flowchart of the present embodiment, which corresponds to the first aspect of the present invention. Describing along a flowchart, in step 1 (hereinafter, step is abbreviated as S), the operating state of the engine 1 is read. Here, the operation state is determined from the crank angle sensor 10 and the accelerator opening sensor 9 shown in FIG. If it is the reducing agent supply area, proceed to S3,
If not, the process proceeds to S6. In S3, the reducing agent supply amount Qpst is searched from the map shown in FIG. In S4, the property of the reducing agent is detected by the property determining means (for example, hydrometer) 25.

In S5, the amount of the reducing agent to be supplied is corrected according to the detected specific gravity. For a catalyst in which a reducing agent with a small C number is effective, the supply amount is small when the specific gravity is smaller than the standard specific gravity of the reducing agent, and the supply amount is large when the specific gravity is large.
The opposite is true for catalysts where a large C number reducing agent is effective. In S6, the target fuel injection amount Qs is retrieved from the fuel injection amount map shown in FIG. 6 based on the engine speed Ne and the accelerator opening Acc read by the crank angle sensor 10, and fuel is injected.

(Embodiment 2) Embodiment 2 is the second embodiment.
It corresponds to the described invention. The configuration of the present embodiment is the same as the configuration of the first embodiment, and a description thereof will not be repeated. The control of the present embodiment is almost the same as the control flowchart of the first embodiment shown in FIG. 4, but in the present embodiment, after the property of the reducing agent is determined in S5 of FIG. Only when it is determined that the property of the reducing agent is light, the amount of the reducing agent to be given is reduced with respect to the standard. For example, in a copper-based catalyst, C
Since a small number of reducing agents are effective, the supply amount of the reducing agent is reduced only when it is determined that the material is light. If the amount of the reducing agent is increased while the oxidation activity is low, the amount of the reducing agent is not increased because the amount of HC emission from the tail pipe may increase.

(Embodiment 3) Embodiment 3 is a third embodiment.
It corresponds to the described invention. FIG. 7 is a diagram for explaining the configuration of the present embodiment. The configuration of the present embodiment is different from the configuration of the first embodiment shown in FIG. 1 in that the reducing agent tank 24, the property determining means 25, and the nozzle 26 Are omitted, and the other configuration is the same as the configuration of the first embodiment, and thus the description is omitted.

FIG. 8 is a control flowchart of the third embodiment.
In S1, the operating state of the engine 1 is read. Here, the operating state is determined from the crank angle sensor 10 and the accelerator opening sensor 9 shown in FIG. In S2, it is determined whether the operation state read in S1 is in the fuel property detection operation region. If it is the fuel property detection operation region, the process proceeds to S3, and if not, the process proceeds to S7. In S3, the target fuel injection amount QS is searched from the fuel injection amount map shown in FIG. 6 based on the engine speed Ne and the accelerator opening Acc read by the crank angle sensor 10, and fuel is injected. In S4, the target rail pressure Prs is searched from the target rail pressure map shown in FIG. 5 based on the engine speed Ne and the accelerator opening Acc read by the crank angle sensor 10. From this difference from the actual rail pressure Pri, a pump discharge amount Qsp for maintaining the rail pressure is determined.

In step S5, a pump discharge amount Qsp 'at a reference fuel temperature is obtained from the pump discharge amount Qsp and the fuel temperature Tfu detected by the fuel temperature sensor 12, and the fuel discharge amount under a predetermined operating condition is determined. Determine the properties. For example, at this time, if the amount of Qsp 'is large, the kinematic viscosity is low = light, and it is determined from the fuel property characteristics in FIG. The pump discharge amount Qsp is determined by the pumping amount of the pumping plunger 17 of the pump 14. The pumping amount is adjusted by opening and closing the control valve 13.
For example, the amount of pumping can be controlled by opening the control valve 13 for a predetermined period during plunger pumping. The pump discharge amount Qsp can be detected from the open time of the control valve 13 at this time, and the discharge amount is corrected based on the open time and the fuel temperature Tfu to obtain the pump discharge amount Qsp 'at the reference fuel temperature.
By comparing the discharge amount Qsp with the discharge amount when a standard fuel is used, the kinematic viscosity of the fuel can be detected.

In S6, a correction coefficient Kf for the post injection amount shown in FIG. 11 is read from the viscosity of the fuel determined in FIG. For example, in the case of the catalyst having the characteristics shown in FIG. 12, the lighter the fuel, the more HC species effective for NO _x reduction, so that Kf <1 when the fuel is determined to be light (standard fuel: Kf = 1).

In S7, it is determined from the operating conditions whether post injection is necessary. The activity of the catalyst is determined from the exhaust gas temperature detected by the exhaust gas temperature sensor 7. If the catalyst is active, it is determined that the catalyst is in the post injection region. Even when the exhaust temperature sensor 7 is not provided, it is possible to estimate the exhaust temperature from the operating state and determine whether or not it is in the post injection region. If it is determined to be the post injection region, the process proceeds to S8, and if not, the process proceeds to S10.

In S8, the operation state and p as shown in FIG.
The post injection amount is determined from the post injection map.
In S9, the target p is set according to the correction coefficient Kf read in S6.
The ost injection amount is corrected, and po is injected at a predetermined time during the expansion stroke.
Perform st injection. The post injection amount is Kf × Qpost. In S10 and S11, the main injection is performed according to the operating state, as in S3 and S4.

(Embodiment 4) Embodiment 4 is a fourth embodiment.
It corresponds to the described invention. The configuration of the present embodiment is the same as the configuration of the third embodiment, and a description thereof will be omitted. The control of the present embodiment is almost the same as the control flowchart of the third embodiment shown in FIG. 8, but in the present embodiment,
Target post injection amount Kf × Qpos obtained in S9 of FIG.
A correction is made to the energization time Tf for the solenoid valve 16 with respect to t. The energizing time Tf at the fuel temperature obtained by the correction coefficient Kf and the fuel temperature sensor 12 in the map shown in FIG.
Is calculated, and the correction coefficient Kqps is obtained.
The post-injection is performed by opening the solenoid valve 16 for a time Kqpst × Tf obtained by multiplying t by Tf shown in FIG.

(Embodiment 5) Embodiment 5 is a fifth embodiment.
It corresponds to the described invention. The configuration of the present embodiment is the same as the configuration of the third embodiment, and a description thereof will be omitted. The control of the present embodiment is almost the same as the control flowchart of the third embodiment shown in FIG. 8, but in the present embodiment,
EG with respect to the target post injection amount obtained in S8 of FIG.
Make corrections when the R rate changes. As shown in FIG. 15, in the EGR region, the EGR rate is set lower during cold operation than during warm-up (the EGR rate is Kegr × the target EGR obtained from FIG. 16). For this reason, in the EGR range, the flow rate of the exhaust gas flowing through the catalyst differs between when the engine is cold and when the engine is warmed up.

As shown in FIG. 17, the performance of the catalyst is sensitive to the space velocity SV. Therefore, if the real space velocity SV such as during cold increases, N by increasing the post injection amount, increasing the catalyst inlet HC / NO _x ratio
Since the O _x conversion is improved, it is possible to obtain the target NO _x conversion by adjusting the post injection amount according to the actual space velocity SV. From the relationship between the water temperature and the EGR coefficient Kegr shown in FIG. 18, a post injection amount coefficient Kqpst2 is obtained as shown in the figure according to Kegr, and post injection is performed by an amount obtained by multiplying the coefficient by the target post injection amount Qpost shown in FIG. Do.

[0019]

As described above, according to the first aspect of the present invention, by controlling the target post injection amount in accordance with the properties of the fuel, the deterioration of the fuel consumption can be minimized, and N
Can be drawn to the ability of the O _x catalyst maximally and become,
Good exhaust characteristics are obtained. In the invention according to claim 2,
In addition to the effect of the first aspect of the present invention, since the injection characteristics of the fuel injection nozzle are different depending on the property and the fuel temperature of the fuel, the target post is determined according to the property and the fuel temperature of the fuel.
By controlling the injection period control valve with respect to the injection amount, it becomes possible to perform accurate post injection regardless of the outside air temperature and the operating state. In the invention according to claim 3, claim 2
In addition to the effect of the invention described, it is possible to maximize even cold during the performance of the NO _x catalyst by controlling the post injection amount according to the actual space velocity SV of the catalyst.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between kinematic viscosity and injection rate.

FIG. 3 is a diagram showing a common rail fuel injection system according to the first embodiment.

FIG. 4 is a control flowchart of the first embodiment.

FIG. 5 is a diagram showing a relationship between an operating state and a post injection amount.

FIG. 6 is a diagram showing a target injection amount according to operating conditions.

FIG. 7 is a diagram illustrating a configuration of a third embodiment.

FIG. 8 is a control flowchart according to the third embodiment.

FIG. 9 is a diagram showing a target rail pressure according to operating conditions.

FIG. 10 is a diagram showing a relationship between a pumping amount and a fuel property in a reference state.

FIG. 11 is a diagram showing a relationship between kinematic viscosity and coefficient Kf.

FIG. 12 is a diagram showing HC species and NO _x conversion.

FIG. 13 is a diagram illustrating a relationship between kinematic viscosity and a coefficient Kqpst of a solenoid valve energizing time.

FIG. 14 is a diagram showing a relationship between a target injection amount and a solenoid valve energizing time at each rail pressure.

FIG. 15 is a diagram showing a relationship between a water temperature and an EGR coefficient.

FIG. 16 is a diagram showing a relationship between an operating state and a target EGR rate.

FIG. 17 is a diagram showing the relationship between the space velocity SV and the NO _x reduction rate.

FIG. 18 is a diagram showing a relationship between an EGR coefficient and a target post injection amount.

FIG. 19 is a view showing properties of light oil and HC species.

[Explanation of symbols]

1 engine 2 intake pipe 3 an exhaust manifold 4 exhaust pipe 5 EGR valve 6 NO _x catalyst 7 exhaust gas temperature sensor 8 common rail fuel injection system 9 accelerator opening sensor 10 crank angle sensor 11 the cam angle sensor 12 fuel temperature sensor 13 control valve 14 pumping Pump 15 Common rail 16 Solenoid valve 17 Pressure feed plunger 18 Fuel tank 19 Nozzle 20 Common rail pressure sensor 21 Check valve 22 Control unit 23 Control valve 24 Reducing agent tank 25 Property determination means (specific gravity meter) 26 Nozzle (Reducing agent supply means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 364 F02D 45/00 364K F02M 25/07 570 F02M 25/07 570J F-term (Reference) 3G062 AA01 AA03 BA04 BA05 FA06 FA13 GA04 GA06 GA09 GA15 3G084 AA01 AA03 BA09 BA13 BA15 BA20 BA24 DA07 DA10 EB01 EB08 FA10 FA14 FA33 FA38 3G091 AA02 AA11 AA18 AA28 AB05 BA01 BA14 CA13 CA18 CB02 CB03 CB08 DA01 EA08 FB10 HA36 HB03 HB05 3G301 HA02 HA04 HA06 HA13 HA15 JA25 JB09 LB11 MA11 MA18 MA19 MA20 MA26 NA08 NC02 ND42 NE01 NE13 PB01A PB01B PB02A PB02B PD11A PD11B PE01A PE01B PE03A PE03B PF03A PF03B

Claims (5)

[Claims] 1. An exhaust gas treatment apparatus having a catalyst disposed in an exhaust passage of an internal combustion engine for purifying exhaust gas, and having a reducing agent supply unit for supplying a reducing agent to the catalyst. Operating state detecting means for detecting the state; and property detecting means for detecting the property of the reducing agent supplied to the catalyst, and supplying the catalyst to the catalyst according to the detected operating state and the property of the reducing agent. An exhaust gas treatment device characterized by controlling the amount of a reducing agent. 2. The exhaust gas treatment apparatus according to claim 1, wherein the supply amount of the reducing agent is reduced when the fuel is determined to be lighter than the reference fuel. 3. The method according to claim 1, wherein the reducing agent uses fuel of an internal combustion engine, and supplies the reducing agent in an expansion stroke or an exhaust stroke by a fuel injection device that performs post injection by a common rail type fuel injection system, a unit injector, or the like. The exhaust gas treatment device according to claim 1 or 2, wherein 4. The exhaust gas treatment apparatus according to claim 3, wherein a fuel injection period when fuel is injected during the expansion stroke is corrected according to a property of the fuel. 5. The exhaust gas processing apparatus according to claim 3, wherein a fuel injection amount when fuel is injected during the expansion stroke is corrected according to an actual EGR rate.