JPH1182181A - Exhaust control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of smoke at the time of an exhaust throttle valve being operated in an internal combustion engine provided with the exhaust throttle valve and an EGR valve. SOLUTION: An exhaust control device A for an internal combustion engine is provided with; an exhaust returning passage 15 connecting an exhaust passage 9b with an intake passage 8b of a diesel engine 1 by-passing a cylinder 2 so as to return exhaust gas from the exhaust passage 9b to the intake passage 8b; an EGR valve 16 provided at the exhaust returning passage 15 so as to control the flow of returned exhaust gas; and an exhaust throttle valve 14 provided at the exhaust passage 9b being positioned downstream of a connection place P to the exhaust returning passage 15 so as to throttle the flow of exhaust gas flowing in the exhaust passage 9b. When the diesel engine is in warming-up operation and the temperature is lower than a specified warming-up temperature, the exhaust throttle valve 14 is closed after reducing the opening of the EGR valve 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust control system for an internal combustion engine, and more particularly to an exhaust control system for an internal combustion engine having an exhaust throttle valve and an EGR device.

[0002]

2. Description of the Related Art An internal combustion engine promotes warm-up by closing an exhaust throttle valve provided in an exhaust passage at a low temperature just after starting the engine. In the internal combustion engine, an exhaust gas recirculation device, so-called E, is mainly used for the purpose of reducing NOx generation.
It has a GR device. EGR is an acronym for exhaust gas recirculation and is called EGR, which literally means returning a part of the exhaust gas to the intake system and re-entering it in the cylinder. The EGR device is a device for that purpose, and connects at least an exhaust passage and an intake passage of the internal combustion engine to the cylinder portion in a bypass shape, and exhaust gas that recirculates exhaust gas from the exhaust passage to the intake passage. The apparatus includes at least a recirculation passage and an exhaust gas recirculation amount control valve provided in the exhaust gas recirculation passage for controlling a flow rate of the recirculated exhaust gas.

When an exhaust throttle valve is closed in an internal combustion engine provided with an exhaust throttle valve and an EGR device, the back pressure increases. Back pressure, as is well known, is the pressure created due to the resistance of the exhaust gas flow in the exhaust system. As the back pressure increases, the piston moves during the exhaust stroke, and the output decreases.
In order not to reduce the output, the work load of the internal combustion engine must be increased. In order to increase the amount of work, it is necessary to increase the amount of combustion, so that the amount of heat generated increases and the warm-up is promoted (see, for example, JP-A-5-71367).

When the exhaust throttle valve is throttled, at least a part of the exhaust gas originally discharged into the atmosphere becomes EGR.
The gas is returned to the intake passage via the exhaust gas recirculation passage. Therefore, the warm-up can be promoted also by the heat of the exhaust gas (for example, see Japanese Utility Model Laid-Open No. 2-22659).

[0005]

By the way, in a diesel engine equipped with an exhaust throttle valve and an EGR device, an EGR
If the exhaust throttle valve is closed while the exhaust gas is being recirculated from the exhaust passage to the intake passage by operating the device, the amount of exhaust gas returning to the intake passage becomes excessive, and the cylinder volume is constant. Becomes For this reason, the fuel cannot be sufficiently burned, which causes smoke and misfire.

Although the exhaust gas recirculation amount control valve of the EGR device is closed after the exhaust gas throttle valve is closed, the time from closing the exhaust gas recirculation valve to closing the exhaust gas recirculation amount control valve, even momentarily, is time-consuming. There is a gap. For this reason, it was difficult to suppress the generation of smoke and misfire corresponding to the time lag.

Further, as described above, in an internal combustion engine in which the back pressure is increased by restricting the exhaust throttle valve to increase the output and thereby promote warm-up, the EGR device is used. When the exhaust throttle valve is closed during operation, if the amount of exhaust gas returning to the intake passage is large, the back pressure does not increase and the warm-up property is reduced.

The present invention has been made in view of the above circumstances, and provides an internal combustion engine exhaust control apparatus for preventing generation of smoke in an internal combustion engine provided with an exhaust throttle valve and an EGR device. Technical issues.

[0009]

In order to achieve the above object, an exhaust gas control apparatus for an internal combustion engine according to the present invention connects an exhaust passage and an intake passage of the internal combustion engine to a cylinder portion in a bypass manner, and An exhaust gas recirculation passage for recirculating exhaust gas from a passage to the intake passage; an exhaust gas recirculation amount control valve provided in the exhaust gas recirculation passage to control a flow rate of the recirculated exhaust gas; An exhaust control device for an internal combustion engine, comprising: an exhaust throttle valve located downstream of a connection point with a passage and for restricting a flow of exhaust gas flowing through the exhaust passage, has the following configuration.

That is, when the internal combustion engine is in a warm-up operation and is lower than a predetermined warm-up temperature, the exhaust throttle valve is closed after reducing the opening of the exhaust gas recirculation amount control valve. It is characterized by.

In the exhaust control apparatus for an internal combustion engine according to the present invention, after the internal combustion engine is in a warm-up operation and has a temperature lower than a predetermined warm-up temperature, the opening degree of the exhaust gas recirculation amount control valve is reduced. By closing the exhaust throttle valve, even if a large amount of exhaust gas flows from the exhaust passage into the exhaust recirculation passage by closing the exhaust throttle valve, the opening degree of the exhaust gas recirculation amount control valve is already reduced before that. Therefore, only the exhaust gas corresponding to the opening degree flows into the intake passage. Therefore, the ratio of oxygen in the air-fuel mixture does not become extremely low. For this reason, the inside of the cylinder is not deficient in oxygen, and the fuel cannot be sufficiently burned. Therefore, generation of smoke can be prevented and misfire does not occur.

Further, the fuel supply means for supplying fuel to the cylinder portion may increase the supplied fuel while the exhaust throttle valve is closed. Since the amount of combustion increases by doing in this way, the output of the internal combustion engine increases, and the warm-up property also improves.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. <Overall Configuration of Apparatus> As shown in FIG. 1, a piston 3 is provided in a cylinder bore 2a formed in a cylinder 2 of a diesel engine 1 as an internal combustion engine so as to be vertically movable. Further, the piston 3 is connected to a crankshaft (not shown) via a connecting rod 4.

A combustion chamber 6 is formed in the piston head 3a. A cylinder head 7 is mounted and fixed on the upper part of the cylinder 2, and an intake port 8 and an exhaust port 9 facing the combustion chamber 6 when the piston 3 rises are provided inside the cylinder head 7.

An intake valve 8a and an exhaust valve 9a are incorporated in the intake port 8 and the exhaust port 9, respectively. An injection (fuel supply means) for injecting fuel into the combustion chamber 6 to supply the fuel between the two valves. 11 is arranged facing the combustion chamber 6. Further, the fuel is rushed out of the injection 11 by an injection pump (not shown).

A rotation speed sensor (not shown) for detecting an engine rotation speed is attached to the injection pump. The intake port 8 is connected to an intake pipe 8b as an intake passage, and the exhaust port 9 is connected to an exhaust pipe 9b as an exhaust passage.

The intake pipe 8b is provided with an air flow meter (not shown) for measuring the amount of intake air (fresh air). The exhaust pipe 9b is provided with an exhaust throttle valve 14 that is connected to and driven by a pressure control valve 14a such as an EVSV (electric vacuum switching valve). The exhaust throttle valve 14 is opened or closed. ON / OF
F control is performed. Then, at least when the temperature of the cooling water of the diesel engine 1 is low, the valve is closed to narrow the exhaust pipe 9b.

The exhaust pipe 9b and the intake pipe 8b are connected in a bypass manner to the cylinder 2 and are connected by an exhaust gas recirculation passage 15 for recirculating exhaust gas from the exhaust pipe 9b to the intake pipe 8b. The exhaust throttle valve 14 is located downstream of a portion P, which is a connection point between the exhaust gas recirculation passage 15 and the exhaust pipe 9b. A large-diameter portion 8b1 of the intake pipe 8b, which is a connection point between the exhaust gas recirculation passage 15 and the intake pipe 8b, is located downstream of the air flow meter (not shown).

The bold arrow in the exhaust gas recirculation passage 15 indicates a state in which part of the exhaust gas is recirculated from the exhaust pipe 9b to the intake pipe 8b. An EGR valve 16 as an exhaust gas recirculation control valve is provided at a junction between the intake pipe side end 15a of the exhaust gas recirculation passage 15 and the large diameter portion 8b1 of the intake pipe 8b.

The EGR valve 16 is an exhaust gas recirculation amount control valve for controlling the amount of exhaust gas recirculated from the exhaust pipe 9b to the intake pipe 8b via the exhaust gas recirculation passage 15. EGR valve 16
Is a pressure control valve 16a having the same structure as the pressure control valve 14a.
Is linked to

The pressure control valve 16a, together with the pressure control valve 14a, is an engine electronic control unit (hereinafter referred to as "ECU").
17 are electrically connected. When the ECU 17 controls the pressure control valve 14a and the pressure control valve 16a, the exhaust throttle valve 14 and the EGR valve 16 are opened and closed, respectively.

The ECU 17 controls the exhaust throttle valve 14 and the EGR valve 1
In opening and closing the valve 6, at least the engine speed and the fuel injection amount of the injection 11 are input to the ECU 17, and the opening and closing amounts of the exhaust throttle valve 14 and the EGR valve 16 are calculated from these input values.

When the diesel engine 1 is in the warming-up operation and the temperature is still lower than a predetermined warming-up temperature, the ECU 17 reduces the opening of the EGR valve 16 and then sets the exhaust throttle valve. 14 is closed.

A cooling water passage 18 having a water temperature sensor 18a is formed in the cylinder block 2. The cooling water passage 18 is connected to a vehicle interior heater H that uses the cooling water passing therethrough as a heat source, and warm air is sent from the vehicle interior heater H into the vehicle interior.

The injection 11 is also controlled by the ECU 17
The appropriate amount of fuel is fed to the combustion chamber 6 at an appropriate time under the control of the above. When the exhaust throttle valve 14 is closed, the amount of fuel supplied to the diesel engine 1 is increased by the injection 11.

As described above, the exhaust passage 9b and the intake passage 8b are connected to the cylinder 2 in a bypass manner, and the exhaust gas recirculation passage 15 for recirculating exhaust gas from the exhaust passage 9b to the intake passage 8b is provided. EGR valve 16 provided in passage 15 for controlling the flow rate of the recirculated exhaust gas
And an exhaust throttle valve 14 that is located downstream of a connection point P of the exhaust passage 9b with the exhaust recirculation passage 15 and throttles the flow of exhaust gas flowing through the exhaust passage 9b. When the engine 1 is in a warm-up operation and is still lower than a predetermined warm-up temperature, the exhaust throttle valve 14 is closed after the opening degree of the EGR valve 16 is reduced, and fuel is supplied to the cylinder 2. An injection control device A for an internal combustion engine according to the present invention is configured to increase the amount of supplied fuel while the injection 11 is closing the exhaust throttle valve 14.

Next, a routine for controlling the operation of the exhaust control device A for the internal combustion engine will be described with reference to FIG. This routine is a part of a normal flowchart (not shown) for driving the diesel engine 1 and includes steps 101 to 104 described below. The operations in the following procedure are all performed by the ECU 17.

When the processing shifts to this routine after the start of the diesel engine 1, in step 101, the exhaust throttle valve 14 is turned on, that is, the exhaust throttle valve 1 is turned on.
Then, it is determined whether or not the engine operating conditions for closing 4 have been met. The operating conditions in this case include a cooling water temperature, an outside air temperature, an engine speed, and the like. Step 10
If a positive determination is made in step 1, the process proceeds to the next step 102, and if a negative determination is made, this routine ends.

In step 102, the EGR control is executed based on the exhaust throttle ON EGR control map shown in FIG. Here, the symbol indicated by Anm such as A11 shown in FIG.
It indicates the opening degree (opening amount) of the valve, and the opening degree of the EGR valve is determined by the engine load and the number of revolutions in a certain operating state. This map is stored in a read-only memory (not shown) included in the ECU 17 in advance. After executing the EGR control in step 102, the process proceeds to step 103.

In step 103, it is determined whether the EGR control is being performed and the exhaust throttle valve 14 is open. If so, an affirmative decision is made and the routine proceeds to the next step 104, otherwise a negative decision is made and this routine is terminated.

In step 104, the exhaust throttle valve 14 is set to O
N, ie, actuate to close. Before or after this routine, there is a routine for closing the EGR valve 16 using the EGR control map for turning off the exhaust throttle shown in FIG. 4, but is omitted here. The sign of Bnm, such as B11 shown in FIG.
This is the same as the meaning of the symbol indicated by nm, and indicates the degree of opening of the EGR valve 16, and also in this case, is determined by the engine load and the number of revolutions. Note that, under the same condition where the rotation speed and the engine load are the same, the opening of the EGR valve 16 is larger in Bnm than in Anm. <Effects of Embodiment> Next, an exhaust control device A for an internal combustion engine
The operation and effect of will be described.

In the exhaust control device A for the internal combustion engine, when the diesel engine 1 is in the warming-up operation and is still lower than the predetermined warming-up temperature, the exhaust throttle is reduced after the opening degree of the EGR valve 16 is reduced. Since the valve 14 is closed, even if a large amount of exhaust gas flows into the exhaust gas recirculation passage 15 from the exhaust passage 9 b by closing the exhaust throttle valve 14, the EGR is already performed before that.
Since the opening degree of the valve 16 is reduced, only the exhaust gas corresponding to the opening degree flows into the intake passage. For this reason,
Since the proportion of oxygen in the air-fuel mixture does not become extremely low, there is no shortage of oxygen, and the fuel cannot be sufficiently burned. Therefore, generation of smoke can be prevented and misfire does not occur.

The injection 11 for supplying fuel to the cylinder 2 is operated while the exhaust throttle valve 14 is closed.
The supplied fuel may be increased. Since the amount of combustion increases by doing in this way, the output of the diesel engine 1 increases, and the warm-up property also improves.

[0034]

As described above, according to the exhaust gas control apparatus for an internal combustion engine of the present invention, when the internal combustion engine is in a warm-up operation and is still lower than a predetermined warm-up temperature, the exhaust gas is returned. Since the exhaust throttle valve is closed after the opening degree of the flow control valve is reduced, by closing the exhaust throttle valve, even if a large amount of exhaust gas flows into the exhaust gas recirculation passage from the exhaust passage, the exhaust gas is exhausted before that. Since the opening degree of the recirculation amount control valve has already been reduced, only the exhaust gas corresponding to the opening degree flows into the intake passage. For this reason, the ratio of oxygen in the air-fuel mixture does not become extremely low, so that oxygen is not sufficient and fuel cannot be sufficiently burned. Therefore, generation of smoke can be prevented and misfire does not occur.

Further, the fuel supply means for supplying fuel to the cylinder portion may increase the amount of fuel supplied while the exhaust throttle valve is closed. Since the amount of combustion increases by doing in this way, the output of the internal combustion engine increases, and the warm-up property also improves.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an exhaust control device for an internal combustion engine of the present invention.

FIG. 2 is a routine for controlling the operation of an exhaust control device A of the internal combustion engine.

FIG. 3 EGR control map for exhaust throttle ON

FIG. 4: EGR control map for exhaust throttle OFF

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine (internal combustion engine) 2 ... Cylinder (cylinder part) 2a ... Cylinder bore 3 ... Piston 3a ... Piston head 4 ... Connecting rod 6 ... Combustion chamber 7 ... Cylinder head 8 ... Intake port 8a ... Intake valve 8b ... Intake pipe (intake) 8b1 large diameter section 9 exhaust port 9a exhaust valve 9b exhaust pipe (exhaust passage) 11 injection (fuel supply means) Ga intake air amount (fresh air) EVSV electric vacuum switching valve 14 ... Exhaust throttle valve 14a ... Pressure control valve P ... Connection point of the exhaust passage with the exhaust gas recirculation passage 15 ... Exhaust gas recirculation passage 16 ... EGR valve (exhaust gas recirculation amount control valve) 16a ... Pressure control valve 17 ... ECU 18 ... Cooling Water passage H: Vehicle indoor heater A: Exhaust control device for internal combustion engine

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/06 330 F02D 41/06 330Z

Claims (2)

[Claims] 1. An exhaust gas recirculation passage for connecting an exhaust passage and an intake passage of an internal combustion engine to a cylinder portion in a bypass shape, for recirculating exhaust gas from the exhaust passage to the intake passage, and provided in the exhaust gas recirculation passage. An exhaust gas recirculation amount control valve for controlling a flow rate of the recirculated exhaust gas; and a flow of the exhaust gas flowing downstream of a connection point of the exhaust passage with the exhaust gas recirculation passage and flowing through the exhaust passage. An exhaust control valve for an internal combustion engine, comprising: an opening degree of the exhaust gas recirculation amount control valve when the internal combustion engine is in a warm-up operation and is lower than a predetermined warm-up temperature. The exhaust control device for an internal combustion engine, wherein the exhaust throttle valve is closed after reducing the pressure. 2. The exhaust control of an internal combustion engine according to claim 1, wherein the fuel supply means for supplying fuel to the cylinder portion increases the amount of fuel supplied while the exhaust throttle valve is closed. apparatus.