JP2003286820A - Engine exhaust-emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine exhaust-emission control device in which a catalyst can be heated even without a great capacity generator and an electric heater under an operating condition in which an exhaust temperature is below a temperature for catalytic activation. <P>SOLUTION: The control device comprises a filter, a heating means, an exhaust flow-rate reduction means, and a control means. The filter is provided in the exhaust system of the engine for oxidizing particulates in exhaust gas by catalytic action and removing them. The heating means is provided in the upstream of the filter or in the filter in order to heat the filter. A flow rate of exhaust gas flowing in the filter is reduced by the flow-rate reduction means. The control means drives the flow-rate reduction means prior to the heating of the filter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust emission control device.

[0002]

2. Description of the Related Art Generally, in an exhaust system of an engine such as a diesel engine, a filter is clogged due to the collection of particulates contained in the exhaust gas. Therefore, the collected particulates are incinerated to regenerate the filter. Exhaust gas purification device is installed. As an exhaust emission control device for a diesel engine, a continuous regeneration system is known in which collected particulates are incinerated by a catalytic reaction to regenerate a filter. In the continuous regeneration system, when the filter is clogged with particulates, the temperature of the exhaust gas is raised without using a forced regeneration means such as an electric heater or a burner, and the filter is regenerated by a catalytic reaction.

In a diesel engine employing such a continuous regeneration type exhaust purification device, unburned hydrocarbons (HC) and particulates can be reduced when the exhaust gas temperature is sufficiently high during filter regeneration. Under operating conditions where the exhaust gas temperature does not reach the catalyst activation temperature, such as after cold start, low rotation, low load, the filter may become clogged,
Due to insufficient oxidation by the catalyst, there was a problem that exhaust irritating odor and blue and white smoke deteriorate.

Therefore, under operating conditions in which the exhaust gas temperature does not reach the catalyst activation temperature, it is necessary to appropriately heat the exhaust gas. For example, an exhaust gas purifying apparatus disclosed in Japanese Patent Application Laid-Open No. 9-222009 is known.

[0005]

However, the conventional exhaust emission control device has the following problems.

At a temperature at which the exhaust gas temperature does not reach the catalyst activation temperature, the amount of heat required to raise the exhaust gas temperature to the catalyst activation temperature is required to heat the exhaust gas whole flow using the electric heater, which consumes a large amount of power. This leads to deterioration of fuel efficiency.
That is, in order to heat the exhaust gas exhaust flow to several hundred degrees with an electric heater, electric power of several hundred KW is required, and for that purpose, a large-capacity generator and electric heater are required. The capacity of the electric heater is insufficient.

The present invention has been made to solve the above-mentioned problems, and its purpose is to eliminate the need for a large-capacity generator or electric heater under operating conditions in which the exhaust temperature does not reach the catalyst activation temperature. It is also an object of the present invention to provide an exhaust gas purifying device for an engine that can heat a catalyst.

[0008]

The invention according to claim 1 is
A filter that is provided in the exhaust system of the engine and that oxidizes and removes particulates in the exhaust gas by a catalytic action, a heating unit that is mounted on the upstream side of the filter or on the filter, and that heats the filter, and flows into the filter. The exhaust flow rate reducing means for reducing the exhaust flow rate and the control means for driving the exhaust flow rate reducing means before heating the filter are characterized in that they are configured.

According to a second aspect of the present invention, in the engine exhaust gas purification apparatus according to the first aspect, the filter is a particulate filter that carries an oxidation catalyst on its surface and captures particulates. Claim 3
The described invention is the exhaust gas purifying apparatus for an engine according to claim 1, wherein the filter is a catalyst device having an oxidation catalyst carried on a surface thereof.

According to a fourth aspect of the present invention, in the engine exhaust gas purification apparatus according to the first aspect, the filter has a catalyst device having an oxidation catalyst on its surface, and an oxidation catalyst on its surface to capture particulates. And a particulate filter that does. Claim 5
The described invention is the exhaust gas purifying apparatus for an engine according to any one of claims 1 to 4, wherein the heating means is an electric heater.

According to a sixth aspect of the present invention, in the engine exhaust gas purification apparatus according to any one of the first to fourth aspects, the heating means is a burner. According to a seventh aspect of the present invention, in the engine exhaust gas purification device according to any one of the first to fourth aspects, the heating means controls the injection amount and the injection timing from the fuel injection device, It is characterized in that the filter is heated.

According to an eighth aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to any one of the first to seventh aspects, the exhaust flow rate reducing means is a shunt passage provided in parallel with the filter. By opening an on-off valve interposed in the filter, the flow dividing passage is closed and the flow rate of exhaust gas flowing into the filter is reduced.

According to a ninth aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to any one of the first to seventh aspects, the exhaust flow rate reducing means throttles an intake throttle valve of the engine, thereby It is characterized in that the flow rate of exhaust gas flowing into the filter is reduced. According to a tenth aspect of the present invention, in the engine exhaust gas purification device according to the first to seventh aspects, the exhaust flow rate reducing means is an engine E.
By increasing the exhaust gas recirculation rate in the GR device,
It is characterized in that the flow rate of exhaust gas flowing into the filter is reduced.

According to an eleventh aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to any one of the first to seventh aspects, the exhaust flow rate reducing means changes an opening / closing timing of an intake valve of the engine. Thus, the flow rate of exhaust gas flowing into the filter is reduced.

(Operation) In the invention described in claim 1,
The exhaust flow rate is reduced by the control means before the heating of the filter (before the heating of the filter or simultaneously with the heating of the filter), and the exhaust flow rate is reduced.

Therefore, the exhaust flow rate, that is, the heat capacity is reduced, and the energy for heating the exhaust flow is reduced. According to the second aspect of the invention, the particulates in the exhaust gas are burned (oxidized) while being trapped by the particulate filter. In the invention according to claim 3, while the exhaust gas passes through the filter (catalyst device supporting the oxidation catalyst), hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas are oxidized and removed by the oxidizing action. The particulates are adsorbed or oxidized.

According to the fourth aspect of the present invention, while the exhaust gas passes through the catalyst device, NO in the exhaust gas is converted to N by the oxidizing action.
Change to O ₂ . In the particulate filter, the collected particulates react with NO ₂ and are oxidized and removed (2NO ₂ + C → 2NO + CO ₂ ). In the invention according to claim 5, the filter is heated by the electric heater.

In the invention according to claim 6, the burner heats the filter. In the invention according to claim 7, when the injection amount is increased, the heat generation amount is increased and the exhaust gas temperature is increased, and when the injection timing is delayed, the thermal efficiency is decreased and the exhaust gas temperature is increased. In the invention of claim 8,
Part of the exhaust gas is diverted through the diversion passage, and the flow rate of the exhaust gas flowing into the filter is reduced.

In the ninth aspect of the present invention, the intake air throttle valve is throttled to reduce the amount of air supply, and therefore the exhaust flow rate from the engine is reduced. According to the tenth aspect of the present invention, since a part of the exhaust gas is recirculated to the intake side by the EGR device, the supply air does not enter the intake side by the amount of the exhaust gas that has recirculated, so that the supply amount is reduced. The exiting exhaust flow rate is reduced.

According to the eleventh aspect of the present invention, the intake air amount can be reduced by delaying or advancing the closing timing of the intake valve with respect to a predetermined closing timing, and as a result, the exhaust gas flow rate can be reduced.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<< Embodiment 1 >> Referring to FIG. 1 to FIG.
An embodiment (Embodiment 1) of an exhaust gas purification apparatus for an engine according to claims 1 and 2 will be described by taking a diesel engine as an engine. In FIG. 1, a diesel engine 1 is mounted on a vehicle (not shown).

The diesel engine 1 has an electronic fuel injection device 1A and a controller 19 for controlling the electronic fuel injection device 1A. The electronic fuel injection device 1A operates a fuel injection pump (not shown) having a control rack (not shown) and a fuel injection pump by controlling the movement amount of the control rack in accordance with the fuel injection amount. It is composed of an electronic governor (not shown). The electronic governor moves the control rack D
It has a C linear motor (not shown). An accelerator opening signal from the accelerator opening sensor 14A, a signal from the rotation speed sensor 14, etc. are input to the controller 19, a signal is sent from the controller 19 to the electronic governor, and a control rack of the fuel injection pump is controlled by the DC linear motor. By moving, the fuel injection amount in the fuel injection pump is increased or decreased.

The diesel engine 1 has an engine body 1
Have B. An intake manifold 2 and an exhaust manifold 3 are attached to the engine body 1B. A generator 1C is attached to the engine body 1B.
The generator 1C is incorporated in a known electric circuit. An intake system 4 is connected to the intake manifold 2.
An air heater 4A is installed in the middle of the intake system 4.

An exhaust system 5 is connected to the exhaust manifold 3. The exhaust system 5 includes an exhaust pipe 6 whose one end is connected to the exhaust manifold 3, and a particulate filter interposed in the middle of the exhaust pipe 6 (hereinafter, referred to as “P” in the first embodiment).
F ”), a flow dividing passage 8 that bypasses the filter 7, and a muffler 9. The filter 7 includes a housing 7A and a filter body 7B mounted in the housing 7A.

The filter body 7B has a substantially cylindrical shape made of a porous member made of cordierite (or SiC), and has a large number of cells 7C substantially parallel to the exhaust flow due to honeycomb partition walls (not shown). Formed, each cell 7
The inlet and outlet of C are alternately plugged by a sealing material. The partition wall is coated (supported) with a substance such as Pt having a catalytic action. Then, when the exhaust gas flows into the adjacent cells 7C via the partition wall, the particulates contained in the exhaust gas are captured by the partition wall.

A heating means is mounted in the housing 7A. As the heating means, the electric heater 10 arranged upstream of the filter 7 is shown (corresponding to claim 5).
The electric heater 10 is composed of an electrothermal resistor made of, for example, Kanthal wire. The electric heater 10 can uniformly heat the filter 7. The electric heater 10 may be provided on the outer circumference or inside of the filter body 7B.

The heating means is not limited to the electric heater 10, and means other than the electric heater 10 may be used. For example, a burner may be used as the heating means (corresponding to claim 6). According to the burner, the time required for burning (oxidizing) the particulates can be shortened. Alternatively, it controls the injection amount and injection timing by the electronic fuel injection device 1A (when the injection amount is increased, the heat generation amount increases, the exhaust gas temperature rises, and when the injection timing is delayed, the thermal efficiency decreases and the exhaust gas temperature rises). As a result, heating means for heating the filter 7 can be configured (corresponding to claim 7). By heating the filter 7 by the heating means using the electronic fuel injection device 1A, the mounting space can be saved and the weight can be reduced.

An on-off valve 11 is attached to the diversion passage 8. An electromagnetic valve 13 is connected to the opening / closing valve 11 via an actuator 12. The diesel engine 1 has a rotation speed sensor 1 for detecting the engine rotation speed.
4, a supercharging pressure sensor 15 for detecting supercharging pressure is attached to the intake system 4.

The first temperature sensor 16 is mounted on the housing 7A upstream of the filter body 7B, and the second temperature sensor 1 is installed downstream of the filter body 7B.
7 is attached. The first temperature sensor 16 is for duty-controlling the current flowing through the electric heater 10 according to the temperature on the upstream side of the filter body 7B. Second
The temperature sensor 17 is used to determine control according to the temperature on the downstream side of the filter body 7B (step S104,
S108, S114).

A first pressure sensor 18 for detecting the pressure of exhaust gas upstream of the filter 7 in the exhaust pipe 6 is mounted upstream of the on-off valve 11 in the flow dividing passage 8. Further, inside or outside the housing 7A, a second pressure sensor 22 for detecting the pressure of the exhaust gas on the downstream side of the filter body portion 7B (the atmospheric pressure may be substituted) is mounted. A controller 19 is arranged in the cab (not shown) of the vehicle. On the input side of the controller 19, a rotation speed sensor 14, an accelerator opening sensor 14A, a supercharging pressure sensor 15, a first pressure sensor 18, and a second pressure sensor 22.
The first temperature sensor 16 and the second temperature sensor 17 are connected to each other. The solenoid valve 13 and the electric heater 10 are connected to the output side of the controller 19.

Then, the controller 19 includes a calculation unit 20.
And a storage unit 21. The calculation unit 20 includes a primary clogging determination unit 20A and a secondary clogging determination unit 2.
0B, a first temperature determination means 20C, a second temperature determination means 20D, and a control means 20E (these are configured as software). The primary clogging determination means 20A determines whether or not the pressure loss coefficient a, which is an index indicating the degree of clogging of the PF, is larger than the threshold value a1 (corresponding to step S102 in FIG. 6).

The secondary clogging judging means 20B judges whether the filter pressure loss of the PF is larger than the threshold value ΔP1 (corresponding to step S103 in FIG. 6). The first temperature determination means 20C determines whether or not the PF downstream temperature is equal to or higher than a threshold value (for example, T1 = 10 ° C. to 50 ° C.) (corresponding to step S104 in FIG. 6). Second temperature determination means 20
D determines whether the PF downstream temperature is equal to or higher than a threshold value (temperature T2; catalyst activation temperature) (for example, T2 = 300 ° C.) (corresponding to step S108 in FIG. 6 and step S114 in FIG. 7).

The control means 20E drives the exhaust flow rate reducing means before heating the PF (steps S107 and S1 in FIG. 6).
1)). The control unit 20E can also drive the exhaust gas flow rate reducing unit at the same time as heating the PF. The storage unit 21 stores a threshold value (pressure loss coefficient limit a1),
A threshold value (pressure loss ΔP1), a threshold value (temperature T1), and a threshold value (temperature T2) are stored.

Then, by opening the on-off valve 11, the exhaust flow rate reducing means for reducing the exhaust flow rate flowing into the filter 7 by opening the flow dividing passage 8 is constituted (corresponding to claim 8). According to the exhaust flow rate reducing means, the exhaust flow rate flowing into the filter 7 can be reduced independently of the performance of the diesel engine 1. As the exhaust flow rate reducing means, the flow dividing passage 8 is opened to reduce the exhaust flow rate flowing into the filter 7. However, the present invention is not limited to this, and other examples (a), (ro) of the exhaust flow rate reducing means. ), (C)
Is shown in FIG.

(A) In FIG. 8, the intake system 4 is provided with an intake throttle valve 31. The intake throttle valve 31 is a solenoid valve whose opening changes proportionally, and is connected to the input side of the controller 19. By restricting the intake throttle valve 31, it is possible to configure an exhaust flow rate reducing means for reducing the amount of air supply and reducing the exhaust flow rate flowing into the filter 7 (corresponding to claim 9). According to the exhaust flow rate reducing means, the vehicle mounting space can be saved.

(B) In FIG. 8, the diesel engine 1 is provided with an EGR (Exhaust Gas Recirculation) device 32, and the exhaust gas recirculation rate in the EGR device 32 is increased, whereby the exhaust gas flowing into the filter 7 is increased. Exhaust flow rate reducing means for reducing the flow rate can be configured (corresponding to claim 10). The EGR device 32 can reduce nitrogen oxides (NOx) in the exhaust gas and reduce the exhaust gas flow rate.

Here, the EGR device 32 includes an EGR passage 32A connecting the intake manifold 2 and the exhaust manifold 3, and an EGR passage provided in the EGR passage 32A.
The EGR valve 32B is a solenoid valve whose opening changes proportionally, and is connected to the input side of the controller 19. The controller 19 is an EGR valve 32B
By appropriately controlling the opening degree of the exhaust gas according to the operating state of the engine, the proportion of returning a part of the exhaust gas to the intake side is adjusted,
A part of the exhaust gas from the exhaust system is recirculated to the intake air that is taken into the combustion chamber as EGR gas. According to the exhaust flow rate reducing means, the EGR device 32 can reduce the nitrogen oxides (NOx) in the exhaust gas, and the vehicle mounting space can be saved.

(C) By changing the opening / closing timing of the intake valve (not shown) of the diesel engine 1, exhaust flow rate reducing means for reducing the flow rate of exhaust gas flowing into the filter 7 can be constructed (claim 11). Corresponding to). The intake air amount can be reduced by delaying or advancing the closing timing of the intake valve relative to a predetermined timing, and as a result, the exhaust flow rate can be reduced. According to this exhaust flow rate reducing means, the use of the known variable valve timing mechanism eliminates the need for the flow dividing passage 8 and saves the vehicle mounting space.

In the figure, reference numeral 23 is a regulator and reference numeral 24 is a battery. Next, the operation of this embodiment will be described. The controller 19 performs the following control according to the flowcharts shown in FIGS. FIG. 4 shows a flowchart of a procedure for executing the program of the controller 19.

FIG. 5 shows a subroutine for reading a signal from the sensor in the program of FIG. Figure 6
The normal operation subroutine in the program of FIG. 4 is shown.

FIG. 7 shows a catalyst heating operation subroutine in the program of FIG. In step S1 of FIG. 4, the initial state is set. In the initial state, the controller 19 outputs a command to the solenoid valve 13 to close the opening / closing valve 11. Moreover, the flag is not set. The actuator 12 is driven by the compressed air supplied from the solenoid valve 13, and the opening / closing valve 11 is closed. As a result, the exhaust gas in the exhaust pipe 6 does not flow into the flow dividing passage 8 and all flows into the filter 7.

In step S2, the signals detected by the respective sensors are sent to the controller 19 and the arithmetic unit 2
Read to zero. The subroutine of step S2 is shown in FIG. The subroutine for reading the signal from the sensor will be described with reference to FIG. Step S of FIG.
At 21, the supercharging pressure signal detected by the supercharging pressure sensor 15 is sent to the controller 19, and the arithmetic unit 20
Read in.

In step S22, the rotation speed sensor 1
The signal of the engine rotation speed detected by 4 is sent to the controller 19 and read by the arithmetic unit 20. In step S23, the signal of the engine load detected by the accelerator opening sensor 14A is sent to the controller 19 and read by the arithmetic unit 20. In step S24, the signal of the PF upstream pressure detected by the first pressure sensor 18 is sent to the controller 19 and read by the arithmetic unit 20.

In step S 25, the signal of the PF downstream temperature detected by the second temperature sensor 17 is sent to the controller 19 and read by the arithmetic unit 20. Combustion (oxidation) of particulates by detecting PF downstream temperature
It is possible to judge the temperature of exhaust gas. The first temperature sensor 1
PF upstream temperature detected by 6 and the second temperature sensor 1
The difference from the PF downstream temperature detected by 7 is obtained. If the difference is large, the filter 7 burns (oxidizes), and if the difference is small, the filter 7 does not burn (oxidize) the particulates. The combustion (oxidation) state in the filter 7 can be checked.

When step S25 ends, the program proceeds to step S3. In step S3, it is determined whether there is an error. That is, it is determined whether or not the signal from each sensor does not reach the controller 19, or whether the electric wiring from each sensor to the controller 19 is broken or short-circuited. If YES (when an error has occurred), the process proceeds to step S7. Step S3
In case of NO (when no error occurs),
Go to step S4.

In step S7, the error is displayed on the monitor (not shown) and the driver is warned. In step S4, it is determined whether the engine is rotating. In step S4, it is determined whether or not the engine is rotating. The battery 24 is charged while the engine is rotating, but the battery 24 is not charged while the power is on and the engine is stopped. This is to prevent the battery 24 from rising.
In the case of YES (when it is confirmed that the engine is rotating), the process proceeds to step S5. If NO in step S4 (when the engine is not rotating), the process proceeds to step S8, and an electric power OFF command is transmitted to the electric heater 10. The electric heater 10 is not energized and the filter 7 is not heated (at this time, the flag is turned off).

The process proceeds from step S8 to step S9. In an emergency in which an error has occurred in step S9, the on-off valve 11 is opened to guide the exhaust gas to the flow dividing passage 8 in order to prevent the filter 7 from being clogged with particulates. In addition, the on-off valve 11 is used even at low temperature start or engine stall.
Open (prevents white smoke from cooling the exhaust at PF during cold start).

On the other hand, in step S5, it is determined whether or not the air heater 4A is energized. In this judgment, the air heater 4A consumes about 2 KW of electric power. Therefore, if the electric heater 10 and the air heater 4A are used at the same time, the battery 24 may rise. Therefore, it is confirmed that the air heater 4A is not energized. It is necessary to do so.

If YES in step S5 (when the air heater 4A is energized), the electric heater 10 is turned off.
The FF command is transmitted. The electric heater 10 is not energized and the filter 7 is not heated. If NO in step S5 (when the air heater 4A is not energized), the process proceeds to step S6. In step S6,
It is determined whether or not the "catalyst heating operation in progress" flag is set. The “catalyst heating operation” is an operation in which the electric heater 10 is energized to heat the filter 7.

If YES in step S6 (during catalyst heating operation), the process proceeds to the subroutine "catalyst heating operation" in step S11. If NO (not in catalyst heating operation), "normal operation" is a subroutine in step S10. Proceed to. The "normal operation" that is the subroutine of step S10 will be described with reference to FIG.

First, in step S101, the pressure loss Δ
The pressure loss coefficient a is calculated from P, the engine speed, and the supercharging pressure P1. Hereinafter, the pressure loss coefficient a will be described. FIG. 3 is a graph in which the horizontal axis represents the exhaust gas flow rate G and the vertical axis represents the filter pressure loss ΔP. The pressure loss coefficient a, which is an index indicating the degree of clogging of the PF, is calculated by the equation a = ΔP / G ^K.

In the figure, the exhaust flow rate is estimated from the supercharging pressure, the engine speed and the engine specifications. K is an index of 1 ≤ K ≤ 2, which is obtained in advance from experimental data of exhaust flow rate and pressure loss characteristics or simulation at a fixed amount of particulates, and is generally K ≈ 1 for laminar flow and K ≈ 2 for turbulent flow. is there. The pressure loss coefficient a increases as the collection amount of particulates increases (arrow in FIG. 3).

In step S102, the primary clogging determining means 20A determines whether or not the pressure loss coefficient a is equal to or larger than a threshold value (pressure loss coefficient limit a1). If YES is determined (the pressure loss coefficient a is equal to or larger than the threshold value (pressure loss coefficient limit a1)), it is determined that the particulates are clogged in the PF, and the process proceeds to step S107. If NO (when the pressure loss coefficient a is less than the threshold value (pressure loss coefficient limit a1)), it is determined that the particulates are not clogged in the PF, and the process proceeds to step S103.

In step S103, the secondary clogging judging means 20B judges whether the pressure loss ΔP is equal to or larger than the threshold value ΔP1. If the secondary clogging determining means 20B determines YES (when the pressure loss ΔP is the threshold value ΔP1 (for example, 35 kPa or more)), it is determined that the pressure loss exceeds the limit, and the process proceeds to step S107. In the case (when it is determined that the pressure loss ΔP is the threshold value ΔP1 (for example, less than 35 kPa), it is determined that the pressure loss does not exceed the limit, and the process proceeds to step S104. The pressure loss ΔP is obtained as follows. The pressure loss ΔP is calculated and temporarily stored in the calculation unit 20 of FIG.

Pressure loss ΔP = [exhaust pressure upstream of PF (transmitted from the first pressure sensor 18 in step S24) -P
Difference in exhaust pressure on the downstream side of F (transmitted from the second pressure sensor 22)] = pressure on the inlet side Pf−Pa on the outlet side (approximately atmospheric pressure) In step S104, the first temperature determination means 20C causes the PF downstream side. The temperature is a threshold value (for example, T1 = 10 ° C.)
It is determined whether the temperature is 50 ° C or higher). Step S104
In the case of YES (when the PF temperature is equal to or higher than the threshold ΔT1) (when the temperature is high), the process proceeds to step S105. In the case of NO (when the PF temperature is less than the threshold value ΔT1) (when the temperature is low), the process proceeds to step S107.

Here, the reason for determining whether or not the PF downstream temperature is lower than the low temperature threshold value (for example, T1 = 10 ° C. to 50 ° C.) in the state where the particulates are not clogged in the PF is the reason for low temperature starting. When the exhaust gas temperature is lower than a threshold value (for example, T1 = 10 ° C. to 50 ° C.), exhaust irritating odor and bluish white smoke are generated, so it is better to heat even if the filter 7 is not blocked. As a result, the electric heater 10 does not have to be energized except when the particulates are clogged in the filter 7 or at the time of low temperature start, and the power consumption can be reduced.

In step S105, the electric heater 1
0 is controlled to OFF, and the filter 7 is not heated. Therefore, the catalyst is not heated either. The process proceeds from step S105 to step S106. In step S106, a closing command is output to the on-off valve 11. As a result, the flow dividing passage 8 is closed, and the exhaust gas that has partially flowed into the flow dividing passage 8 flows into the filter 7 and is restored to the normal exhaust flow.

When step S106 is completed, the series of routines are completed and the process returns to FIG. On the other hand, step S1
At 07, an opening command is output to the on-off valve 11. When the opening / closing valve 11 is opened, the diversion passage 8 is opened. The exhaust gas in the exhaust pipe 6 flows to the filter 7 and the branch passage 8. Therefore, the flow rate of exhaust gas flowing into the filter 7 is reduced (corresponding to claim 8). The exhaust gas temperature rises as the exhaust gas flow rate decreases (claims 9, 10, 11).
In step S108 (corresponding to step 1), the second temperature determination means 20D determines whether the PF downstream temperature is equal to or higher than the threshold value 2 (for example, 300 ° C.).

If YES (the PF downstream temperature is the threshold value 2)
(For example, when the catalyst activation temperature is 300 ° C. or higher), the process proceeds to step S105, and the electric heater 10 is controlled to be OFF. This is because the particulates are self-oxidized by the catalyst even if the electric heater 10 is not energized in the filter 7.

In case of NO (the PF downstream temperature is the threshold value 2)
If the temperature is lower than the catalyst activation temperature of 300 ° C., for example, the process proceeds to the subroutine S11 “catalyst heating operation”. This is because the subroutine S11 corresponds to claims 5, 6, and 7. When the filter 7 is regenerated, the exhaust gas flows through the diversion passage 8,
The exhaust flow rate flowing into the filter 7 is reduced.

In this way, by the control means 20E,
The steps S107 and S108 of FIG. 6 are executed, and the exhaust flow rate reducing means is driven before the computing unit 20 heats the PF. Next, step S11 "catalyst heating operation" which is a subroutine will be described with reference to FIG. Step S1
At 11, a flag of "during catalyst heating operation" is set.

In step S112, the electric heater 1
0 is turned on, and the exhaust gas temperature is raised by duty-controlling the current flowing through the electric heater 10 according to the catalyst temperature (upstream temperature). In step S113, the signal of "during catalyst heating operation" is output. In step S114, the second temperature determination means 20D determines whether the catalyst downstream temperature is higher than the threshold value T2.

If YES in step S114 (when the catalyst downstream temperature is equal to or higher than the threshold value T2), the process proceeds to step S116. If NO in step S114 (when the catalyst downstream temperature is lower than the threshold value T2), the process proceeds to step S115. When the catalyst downstream temperature is equal to or higher than the threshold value T2, even if the catalyst is not heated by the electric heater 10, the collected particulates are operated while being sequentially burned (oxidized) by the action of the catalyst. Does not accumulate in the filter 7. That is, the particulates are oxidized while being accumulated, and are not accumulated in the filter 7.

In step S115, it is determined whether the set time has elapsed. If YES in step S115 (if the set time has elapsed), the process proceeds to step S116, and if NO (if the set time has not elapsed), the process returns to the main routine of FIG. In step S116, an OFF command is transmitted to the electric heater 10. The electric heater 10 is not energized, and the filter 7
Is not heated.

In step S117, a closing command is output to the on-off valve 11. As a result, the diversion passage 8
Is closed, and the exhaust gas that has partially flowed into the flow dividing passage 8 flows into the filter 7 and is restored to the normal exhaust flow. In step S118, the flag is turned off, and the process returns to the main routine of FIG.

According to the above-mentioned structure, the following effects can be obtained. First, when oxidizing particulates, the control means 20E reduces the exhaust gas flow rate before heating the filter 7, so the heat capacity is reduced, and the filter is raised to the catalyst activation temperature without a large-capacity generator. The temperature can be raised, and the particulates are sufficiently burnt (oxidized) by the catalyst, and it is possible to prevent the filter from being clogged, and the exhaust stimulating odor and the deterioration of blue and white smoke to be prevented.

Secondly, since the energy for consumption of the electric heater is minimized, the saved energy can be used as the original net horsepower of the engine to improve the fuel consumption of the diesel engine 1. Thirdly, since the filter 7 is a PF that carries an oxidation catalyst on its surface and traps particulates, the particulates can be trapped reliably and the exhaust gas purification rate can be improved.

9 and 10 show a modification of the first embodiment. The modification of the first embodiment is applied to a structure in which a catalyst device having an oxidation catalyst and a particulate filter arranged on the downstream side are integrated instead of the particulate filter in the first embodiment. . Hereinafter, different parts of this structure will be described.
In addition, only the main part of this structure will be described.

In the figure, an exhaust pipe 33 (exhaust pipe 6 in FIG.
(Corresponding to the above), the filter device 34 is interposed, and the flow dividing passage 35 bypasses the filter device 34.
Is provided. An on-off valve 35A is attached to the flow dividing passage 35. The actuator 3 is connected to the opening / closing valve 35A.
A solenoid valve 35C is connected via 5B. Solenoid valve 3
5C is connected to a controller 19 (not shown). The controller 19 has the same structure as that shown in FIGS. 1 and 2, and functions similarly to the first embodiment.

The filter device 34 has a casing 36A. A filter 36B whose surface is coated with an oxidation catalyst is mounted in a casing 36A via a plurality of support stays (support members) 36C. In the filter 36B, a large number of cells 36E substantially parallel to the exhaust gas flow are formed by the honeycomb partition walls 36D.
Has a structure in which the inlet and the outlet are alternately sealed with a sealing material 36F, and the entire surface including the outer periphery of the filter 36B is coated with an oxidation catalyst.

Further, the chamber 3 formed in the casing 36A
An electric heater 38 is attached to 7. And K
The exhaust gas that has flowed into the sing 36A is the outer periphery of the filter 36B.
When flowing toward the inlet end face 36G along the
By the catalytic action of the oxidation catalyst coated on the outer periphery of 6B
A large amount of NO in the exhaust is NO₂Change to (2NO + O₂→ 2N
O₂ ) And flows into the chamber 37. Furthermore, the filter 36B
The particulates collected on the surface of the partition wall 36D
Active oxidation removal by coated oxidation catalyst
(2 NO₂+ C → 2NO + CO₂) And exhaust
HC and CO in the inside are oxidized and removed by the oxidation catalyst.

According to this structure, the same operation and effect as those of the first embodiment can be obtained. Further, since NO ₂ has a large oxidizing power for particulates, the combustion temperature of particulates can be made lower than that of the filter 7 of the first embodiment, and power consumption can be reduced. Further, it is possible to save space. << Embodiment 2 >> An embodiment (Embodiment 2) of an engine exhaust gas purification apparatus according to the first and third aspects of the present invention will be described with reference to FIG. 11, taking a diesel engine as an example of the engine.

The engine exhaust gas purification apparatus according to the second embodiment has the same structure as the engine exhaust gas purification apparatus according to the first embodiment, and the same components are designated by the same reference numerals and their description is omitted. Only different points will be described. In the second embodiment, the catalyst device 41 is used instead of the filter 7 in the first embodiment.

In the catalyst device 41, an oxidation catalyst such as Pt is carried on the surface of a honeycomb-shaped cell 41A formed in large numbers substantially in parallel with the flow of exhaust gas, and while the exhaust gas passes through this, the exhaust gas is transferred to the surface. When they come into contact with each other, they oxidize and remove hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas by an oxidizing action, and adsorb or oxidize particulates. In addition,
When the catalyst device 41 is used, the first in the first embodiment
The reason why there is no pressure sensor 18 is that the catalyst device 41 does not capture particulates and the particulates are not
There is almost no pressure loss.

Further, the branch point 6 of the exhaust pipe 6 with the flow dividing passage 8
A second opening / closing valve 42 for the catalyst device 41 is attached to the downstream portion 6B of A. An electromagnetic valve 44 is connected to the second opening / closing valve 42 via an actuator 43. The solenoid valve 44 is connected to the output side of the controller 19.

The controller 19 simultaneously controls the opening / closing valve 11 and the second opening / closing valve 42. When the on-off valve 11 is open, the diversion passage 8 is open. At this time, the second on-off valve 42
Is closed and the electric heater 10 is turned on. On the other hand, when the opening / closing valve 11 is closed, the diversion passage 8 is closed. At this time, the second opening / closing valve 42 is opened and the electric heater 10 is turned off.

According to the second embodiment, the same operation and effect as those of the first embodiment can be obtained. Further, since the catalyst device 41 is a flow-through catalyst carrier, it is possible to reduce exhaust resistance and prevent a decrease in engine output. << Embodiment 3 >> With reference to FIG. 12, an embodiment (Embodiment 3) of an exhaust gas purification apparatus for an engine according to claims 1 and 4 will be described by taking a diesel engine as an engine.

The engine exhaust purification system according to the third embodiment has the same structure as the engine exhaust purification system according to the first embodiment, and the same components are designated by the same reference numerals and their description is omitted. Only different points will be described. In the third embodiment, a catalyst device 51 and a particulate filter 52 are used instead of the filter 7 in the first embodiment.

The catalyst device 51 is arranged on the upstream side of the particulate filter 52, and carries an oxidation catalyst such as Pt on the surface of the honeycomb-shaped cells 51A formed in large numbers substantially in parallel with the exhaust flow. Further, a second opening / closing valve 53 for the catalyst device 51 is attached to a downstream side portion 6B of the branch point 6A of the exhaust pipe 6 with the branch passage 8. An electromagnetic valve 55 is connected to the second opening / closing valve 53 via an actuator 54. The solenoid valve 55 is connected to the output side of the controller 19.

When the on-off valve 11 is open, the diversion passage 8 is open. At this time, the second opening / closing valve 53 is closed and the electric heater 10 is turned on. On the other hand, when the opening / closing valve 11 is closed, the diversion passage 8 is closed. At this time, the second opening / closing valve 53
Is open and the electric heater 10 is off. Then, while the exhaust gas passes through the catalyst device 51, the exhaust gas comes into contact with the partition walls to oxidize NO in the exhaust gas into NO ₂ gas.
Change to. Further, the catalyst device 51 oxidizes and removes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas, and burns (oxidizes) particulates.

The particulate filter 52 has a substantially cylindrical shape made of a porous member made of cordierite (or SiC), and has a large number of cells 52A substantially parallel to the exhaust flow formed by honeycomb partition walls. Each cell 52
The inlet and the outlet of A are alternately sealed by a sealing material. The partition wall is coated (supported) with a substance such as Pt having a catalytic action. Then, when the exhaust gas flows into the adjacent cells via the partition wall, the particulates contained in the exhaust gas are captured by the partition wall.

In the particulate filter 52, the collected particulates react with the above NO ₂ and are oxidized and removed (2NO ₂ + C → 2NO + CO ₂ ). According to the third embodiment, the same operation and effect as those of the first embodiment are produced. Further, since NO ₂ has a large oxidizing power for particulates, the combustion temperature of particulates can be made lower than that of the filter 7 of the first embodiment, and power consumption can be reduced.

In the first, second, and third embodiments, the diesel engine has been described as an example of the engine, but the engine is not limited to this, and an engine other than a diesel engine such as a gasoline engine or a compressed natural gas engine. Can be applied to.

[0085]

According to the first aspect of the present invention, the exhaust gas flow rate is reduced by the control means before the filter is heated. Therefore, the filter can be heated without a large-capacity generator, and the particulates can be a catalyst. As a result, combustion (oxidation) is sufficiently performed, and it is possible to prevent the filter from being clogged, the exhaust stimulating odor, and the deterioration of blue and white smoke.

Further, since the exhaust flow rate is reduced before the filter is heated by the control means, the energy consumed by the heater is minimized, and the saved energy is used as the original net horsepower of the engine to reduce fuel consumption. Can be better. According to the invention of claim 2, claim 1
In addition to the invention described, the filter is a particulate filter that carries an oxidation catalyst on the surface and captures particulates, so particulates can be captured reliably,
The exhaust gas purification rate can be improved.

According to the third aspect of the present invention, in addition to the first aspect of the invention, the filter is a catalyst device carrying an oxidation catalyst on its surface, so that exhaust resistance is reduced and engine output reduction is prevented. can do. According to the invention described in claim 4, the filter is composed of a catalyst device having an oxidation catalyst on the surface thereof, and a particulate filter having an oxidation catalyst on the surface thereof to capture particulates, and has an oxidizing power. Since it is large, the combustion temperature of the particulates can be lowered and the power consumption can be reduced.

According to the invention described in claim 5, the heating means is an electric heater, so that the filter can be heated uniformly. According to the invention of claim 6, since the heating means is a burner, it is possible to shorten the time required for burning (oxidizing) the particulates. According to the invention described in claim 7, since it is not necessary to mount an electric heater or a burner as a heating means, the mounting space can be saved and the weight can be reduced.

According to the eighth aspect of the present invention, the flow rate of exhaust gas flowing into the filter can be reduced independently of the performance of the engine. According to the invention described in claim 9, the diversion passage is not required, and the installation space of the vehicle can be saved. According to the tenth aspect of the invention, the EGR device can reduce the amount of nitrogen oxides (NOx) in the exhaust gas and the exhaust gas flow rate. According to the eleventh aspect of the present invention, by using the existing mechanism, the diversion passage is unnecessary, and the vehicle mounting space can be saved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an exhaust emission control device for a diesel engine of the present invention.

2 is a block diagram showing the controller of FIG. 1. FIG.

FIG. 3 is an explanatory diagram for determining the degree of clogging of particulates.

FIG. 4 is a flowchart showing a procedure of executing a program of a controller in the first embodiment.

FIG. 5 is a subroutine showing reading of a signal from a sensor in the program of FIG.

6 is a subroutine showing a normal operation in the program of FIG.

7 is a subroutine showing a catalyst heating operation in the program of FIG.

FIG. 8 is a configuration diagram showing a modified example of the heating means or the exhaust flow rate reducing means of the first embodiment.

FIG. 9 is a vertical sectional view showing a modification of the first embodiment.

10 is a cross-sectional view taken along the line I-I of FIG.

FIG. 11 is a configuration diagram showing a second embodiment of an exhaust emission control device for a diesel engine of the present invention.

FIG. 12 is a configuration diagram showing a third embodiment of an exhaust emission control device for a diesel engine of the present invention.

[Explanation of symbols]

1 diesel engine 5 exhaust system 7 filters 8 shunt passage 10 Electric heater 11 on-off valve 19 Controller 20E control means 41 Catalytic device 51 Catalytic device 52 Particulate filter

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/02 F01N 3/02 321J 331 331A 331L 341 341A 341E 341G 341Q F02D 9/02 F02D 9/02 Q 9 / 04 9/04 CE 13/02 13/02 D 21/08 301 21/08 301H 301Z 41/04 360 41/04 360A 370 370 380 380 380A 380M 385 385A 385M F02M 25/07 570 F02M 25/07 570J ( 72) Inventor Takayuki Adachi, 1-chome, Ii-chome, Ageo-shi, Saitama, Nissan Diesel Industry Co., Ltd. (72) Konobu Hirata 1-chome, Ii-chome, Ageo-shi, Saitama Nissan F-term (reference) 3G062 AA01 AA05 BA04 BA06 BA09 CA06 DA01 DA02 EA12 ED01 ED04 ED10 FA02 FA05 FA23 GA04 GA06 GA09 GA14 GA22 3G065 AA01 AA03 AA09 CA12 DA02 DA07 EA07 FA02 GA04 GA06 GA08 GA10 GA46 HA06 JA04 JA09 JA11 EA02 EA02 EA2 CB12 DA08 CB12 DA08 CB12 CB12 CB12 CB12 CB04 CB04 CB12 CB04 CB07 CB04 CB04 CB04 CB04 CB04 CB07 CB04 CB07 AA02 BA01 BB01 BB06 DA01 DA08 DB03 DC03 DC09 DC12 DC15 DE06S DF02 DF09 EA02 FA15 HA01X HA06X HA13X HA16Z HB01X HB02X HD02Z HD07X HD08Z HD09X HE01X 3G301 HA02 HA11 HA15 HA11 HA11 HA15 HA11 HA11 HA11 HA11 HA11 HA11 HA15

Claims (11)

[Claims] 1. A filter that is provided in an exhaust system of an engine and that oxidizes and removes particulates in exhaust gas by a catalytic action, and is mounted on an upstream side of the filter or on the filter
A heating means for heating the filter, an exhaust flow rate reducing means for reducing an exhaust flow rate flowing into the filter, and a control means for driving the exhaust flow rate reducing means before heating the filter. Exhaust purification device for engine. 2. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the filter is a particulate filter that carries an oxidation catalyst on its surface to trap particulates. 3. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the filter is a catalytic device having an oxidation catalyst carried on a surface thereof. 4. The filter comprises a catalytic device having an oxidation catalyst on its surface and a particulate filter which has an oxidation catalyst on its surface to capture particulates. Exhaust gas purification device for the engine described. 5. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the heating means is an electric heater. 6. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the heating means is a burner. 7. The engine according to claim 1, wherein the heating means heats the filter by controlling an injection amount and an injection timing from a fuel injection device. Exhaust purification device. 8. The exhaust flow rate reducing means opens an on-off valve provided in a diversion passage provided in parallel with the filter to open the diversion passage to reduce an exhaust flow amount flowing into the filter. The exhaust emission control device for an engine according to claim 1, wherein the exhaust emission control device is reduced. 9. The exhaust flow rate reducing means reduces the exhaust flow rate flowing into the filter by throttling an intake throttle valve of an engine. Engine exhaust purification device. 10. The exhaust flow rate reducing means reduces the exhaust flow rate flowing into the filter by increasing the exhaust gas recirculation rate in the EGR device of the engine. The exhaust emission control device for an engine according to any one of claims. 11. The exhaust flow rate reducing means changes the opening / closing timing of an intake valve of an engine,
The exhaust gas purification device for an engine according to any one of claims 1 to 7, wherein a flow rate of exhaust gas flowing into the filter is reduced.