JP2001164999A - Clogging sensing device of exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sense accurately an occurrence of clogging in an EGR device to recirculate part of the exhaust gas flowing in the exhaust system of an internal combustion engine back to its suction system, whereby a degradation of exhaust gas emission resulting from clogging is precluded. SOLUTION: A clogging sensing device of an exhaust gas recirculation device is equipped with an exhaust gas recirculating passage leading from the exhaust passage of an internal combustion engine to its suction passage, a flow regulating valve to adjust the flow rate of the exhaust gas flowing in the exhaust gas recirculating passage, an exhaust gas recirculation amount controlling means to control the degree of opening of the flow regulating valve in accordance with the operating condition of the engine, and a clogging judging means to pass a judgement that the exhaust gas recirculating passage is clogged in the case the degree of opening of the flow regulating valve is greater than the specified reference value when the engine is in the specified operating condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation (EGR) device for recirculating a part of exhaust gas flowing through an exhaust system of an internal combustion engine to an intake system, and more particularly to detecting clogging of the EGR device. About technology.

[0002]

2. Description of the Related Art In recent years, an internal combustion engine mounted on an automobile or the like has a lean-burn internal combustion engine capable of burning a mixture in an excess oxygen state (lean air-fuel ratio) in order to reduce fuel consumption. Development is underway.

[0003] On the other hand, it is known that when a mixture having a lean air-fuel ratio is burned in the above-described lean-burn internal combustion engine, a relatively large amount of nitrogen oxide (NOx) is generated. In particular, the higher the combustion speed of the air-fuel mixture or the higher the combustion temperature of the air-fuel mixture, the more nitrogen oxides (NOx) are generated.

[0004] Nitrogen oxides (NO
As a method for reducing the amount of x), an exhaust gas recirculation (EGR) that recirculates a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage of the internal combustion engine is used.
n) A method using a device has been proposed.

[0005] The EGR device uses water vapor (H ₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ) contained in exhaust gas.
Utilizing the incombustibility and endothermic properties of the inert gas components such as the above, the combustion speed and combustion temperature of the air-fuel mixture in the combustion chamber of the internal combustion engine are reduced, and the amount of nitrogen oxides (NOx) generated during combustion Is to be reduced.

[0006] Incidentally, as the above EGR device,
A device including an EGR passage that connects an exhaust passage and an intake passage of the internal combustion engine, and an EGR valve that adjusts a flow rate of exhaust gas (EGR gas) flowing in the EGR passage; and an EGR passage in addition to the EGR passage and the EGR valve. EG for cooling gas
Various configurations of devices have been proposed, such as a device configured by providing an R cooler in the middle of an EGR passage.

In the EGR device, soot and unburned fuel components contained in the exhaust gas adhere to or accumulate on the wall surface of the EGR passage and the wall surface of the EGR cooler, so that the EGR passage and the EGR cooler are not clogged. Occurred in some cases. When clogging occurs in the EGR passage and the EGR cooler, it becomes difficult to recirculate a desired amount of EGR gas to the intake passage, and nitrogen oxide (N
There has been a problem that the amount of generation of Ox) cannot be sufficiently reduced.

In order to solve such a problem, conventionally, an EGR device for a diesel engine as disclosed in Japanese Patent Application Laid-Open No. 10-196462 has been proposed. The EGR device for a diesel engine described in the publication discloses a soot contained in EGR gas as a reducing agent at a portion upstream of an EGR cooler in an EGR passage communicating an exhaust passage and an intake passage of an internal combustion engine. Nitrogen oxide (NOx)
And a NOx reduction catalyst for reducing NOx.

The diesel engine EGR device configured as described above reduces soot flowing into the EGR cooler by consuming soot in the EGR gas as a reducing agent in the NOx reduction catalyst upstream of the EGR cooler. EG
This is to prevent clogging of the R cooler.

[0010]

In an EGR device for a diesel engine as described in the above-mentioned publication, when the NOx reduction catalyst is in an inactive state, the EG
S such as soot and unburned hydrocarbon (HC) contained in R gas
The OF (Solible Organic Function) component flows into the EGR cooler without being consumed by the NOx reduction catalyst.
When such an event is repeated, SOGR is added to the EGR cooler.
There is a possibility that the F component is deposited and clogging of the EGR cooler occurs.

Further, the EG of the aforementioned diesel engine
The R device does not include a means for detecting clogging of the EGR cooler or the EGR passage. Therefore, when clogging of the EGR cooler or the EGR passage actually occurs, a desired amount of EG
It becomes difficult to recirculate the R gas to the intake passage, and as a result, it may not be possible to sufficiently reduce the amount of nitrogen oxides (NOx) generated in the internal combustion engine.

The present invention has been made in view of the various problems described above, and has an EGR device for recirculating a part of exhaust gas flowing through an exhaust system of an internal combustion engine to an intake system of the internal combustion engine. An object of the present invention is to provide a technique for accurately detecting the occurrence of clogging in an EGR device in an internal combustion engine, thereby contributing to preventing deterioration of exhaust emission due to clogging.

[0013]

The present invention employs the following means to solve the above-mentioned problems. That is, the clogging detection device of the exhaust gas recirculation device according to the present invention,
An exhaust recirculation passage that communicates between an exhaust passage and an intake passage of the internal combustion engine, a flow adjustment valve that adjusts a flow rate of exhaust flowing in the exhaust recirculation passage, and the flow adjustment valve according to an operation state of the internal combustion engine. Exhaust gas recirculation amount control means for controlling the opening of the exhaust gas recirculation passage when the opening of the flow regulating valve is larger than a predetermined reference opening when the internal combustion engine is in a predetermined operating state; And clogging determining means for determining that an error has occurred.

In the clogging detection device for the exhaust gas recirculation device configured as described above, the exhaust gas recirculation amount control means controls the opening of the flow control valve according to the operating state of the internal combustion engine. For example, the exhaust gas recirculation amount control means performs feedback control of the opening degree of the flow control valve so that the amount of fresh air actually sucked into the internal combustion engine becomes a desired amount according to the operating state of the internal combustion engine.

In the feedback control as described above,
If the amount of fresh air actually sucked into the internal combustion engine is smaller than a desired amount, the exhaust gas recirculation amount control means corrects the opening of the flow control valve in the valve closing direction.

In this case, the amount of exhaust gas (hereinafter referred to as "recirculated gas") recirculated from the exhaust passage to the intake passage decreases, and the amount of recirculated gas sucked into the internal combustion engine decreases accordingly. become. When the amount of recirculated gas taken into the internal combustion engine decreases, the amount of fresh air taken into the internal combustion engine increases by the reduced amount.

In the feedback control described above, if the amount of fresh air actually sucked into the internal combustion engine is larger than a desired amount, the exhaust gas recirculation amount control means corrects the opening of the flow control valve in the valve opening direction. I do.

In this case, the amount of the recirculated gas recirculated from the exhaust passage to the intake passage increases, and accordingly, the amount of the recirculated gas sucked into the internal combustion engine increases. When the amount of recirculated gas taken into the internal combustion engine increases, the amount of fresh air taken into the internal combustion engine decreases by the increased amount.

If the exhaust gas recirculation passage is clogged while such control is being performed, the opening of the flow control valve is increased as compared with the case where no clogging occurs in the exhaust gas recirculation passage. Will be. That is, when the exhaust gas recirculation passage is clogged, the amount of recirculated gas recirculated from the exhaust passage to the intake passage is reduced from the normal state, and the amount of recirculated gas sucked into the internal combustion engine is reduced accordingly. And the amount of fresh air drawn into the internal combustion engine increases,
The exhaust gas recirculation amount control means opens the flow control valve to reduce the amount of fresh air drawn into the internal combustion engine (in other words, to increase the amount of recirculated gas drawn into the internal combustion engine). It will be corrected in the valve direction.

Therefore, the clogging judging means compares the opening of the flow control valve when the internal combustion engine is in a predetermined operating state with a predetermined reference opening, and if the opening of the flow control valve is larger than the reference opening. It is determined that the exhaust gas recirculation passage is clogged.

The predetermined reference opening may be an opening detected in advance when the internal combustion engine is in a predetermined operation state and no clogging occurs in the exhaust gas recirculation passage. The value may be determined based on the opening detected when the engine is in the predetermined operating state and the exhaust gas recirculation passage is not clogged.

The value determined based on the opening detected when the internal combustion engine is in the predetermined operating state and the exhaust gas recirculation passage is not clogged is determined when the internal combustion engine is in the predetermined operating state and The average value of a plurality of openings detected when no clogging occurs in the exhaust gas recirculation passage may be performed, or the clogging may occur in the exhaust gas recirculation passage when the internal combustion engine is in a predetermined operation state. It may be a value determined in consideration of the learning value of the opening degree detected when not performed.

This is because the internal combustion engine is in a predetermined operating state,
In addition, even when the exhaust gas recirculation passage is not clogged, the opening degree of the flow control valve may be different if conditions such as temperature and pressure are different.

The clogging judging means may judge that a clog has occurred in the exhaust gas recirculation passage when the opening of the flow regulating valve is larger than the reference opening by a predetermined opening or more.
It is assumed that the opening degree of the flow control valve changes depending on conditions. In such a case, the opening degree of the flow control valve is set to the reference opening degree even though the exhaust gas recirculation passage is not clogged. This is because it may be larger.

In the clogging detection device for an exhaust gas recirculation device according to the present invention, when the exhaust gas recirculation passage includes cooling means for cooling the exhaust gas flowing through the exhaust gas recirculation passage, the clogging judging means may include: If the opening of the flow control valve when the internal combustion engine is in a predetermined operating state is larger than a predetermined reference opening, it may be determined that the cooling means has clogged.

This is because the cross-sectional area of the passage formed in the cooling means is often set to be smaller than the exhaust gas recirculation passage, or the components such as soot and unburned fuel contained in the exhaust gas are cooled. Is cooled, the components are liquefied and easily attached to the wall surface inside the cooling means, so that the cooling means is more likely to be clogged than the exhaust gas recirculation passage.

In the clogging detection device for an exhaust gas recirculation device according to the present invention, the predetermined operation state of the internal combustion engine is such that the opening of an intake throttle valve provided in an intake passage of the internal combustion engine is at a predetermined opening, and It is preferable that the internal combustion engine is in a steady operation state with a low load, particularly when the internal combustion engine is in an idle operation state.

Next, a clogging detection device for an exhaust gas recirculation device according to the present invention comprises: an exhaust gas recirculation passage for guiding a part of exhaust gas flowing through an exhaust gas passage of an internal combustion engine to an intake passage of the internal combustion engine; A cooling unit provided in the middle of the passage for cooling the exhaust gas flowing through the exhaust gas recirculation passage; a cooling efficiency calculating unit for calculating a cooling efficiency of the cooling unit; and a cooling efficiency calculated by the cooling efficiency calculating unit. And clogging judging means for judging that clogging has occurred in the cooling means when the cooling means has dropped below the reference value.

The cooling means exchanges heat between the recirculated gas and the refrigerant. When clogging occurs in the cooling means, the cooling means is smaller than when no clogging occurs in the cooling means. As a result, the heat exchange rate in the cooling means decreases. Further, when clogging occurs in the cooling means, the pressure of the recirculating gas flowing through the cooling means is more likely to increase than in the case where no clogging occurs in the cooling means. Temperature easily rises.

Therefore, when clogging occurs in the cooling means, it can be said that the cooling efficiency is lower than when no clogging occurs in the cooling means. For this reason,
When the actual cooling efficiency of the cooling means is lower than a predetermined reference value, it is possible to determine that the cooling means has clogged.

Here, the predetermined reference value may be a value indicating the cooling efficiency when the cooling means is not clogged, or is based on the cooling efficiency when the cooling means is not clogged. May be determined.

As the above-mentioned cooling means, a water-cooled cooler for exchanging heat between predetermined cooling water and recirculated gas can be exemplified. The predetermined cooling water may be cooling water for an internal combustion engine or dedicated cooling water for cooling only the recirculated gas.

When a water-cooled cooler is used as the cooling means, the cooling efficiency calculating means calculates the temperature of the exhaust gas (recirculated gas) flowing into the water-cooled cooler, the temperature of the cooling water supplied to the water-cooled cooler, The cooling efficiency of the water-cooled cooler may be calculated using the temperature of the exhaust gas (recirculated gas) flowing out of the water-cooled cooler as a parameter.

At this time, the temperature of the recirculated gas flowing into the water-cooled cooler and / or the temperature of the recirculated gas flowing out of the water-cooled cooler may be directly detected by using a dedicated temperature sensor. Alternatively, it may be estimated from a detection value of a sensor provided in the internal combustion engine in advance.

Next, a clogging detection device for an exhaust gas recirculation device according to the present invention is provided with an exhaust gas recirculation passage communicating an exhaust gas passage and an intake gas passage of an internal combustion engine, and a flow rate of exhaust gas flowing through the exhaust gas recirculation passage. A flow control valve for adjusting, an intake throttle valve provided in a portion of the intake passage upstream of a connection portion of the exhaust recirculation passage, and regulating a flow rate of intake air flowing through the intake passage; and an operating state of the internal combustion engine. Exhaust recirculation amount control means for controlling the opening degree of the flow regulating valve and / or the intake throttle valve in accordance with the opening degree of the flow regulating valve or the intake throttle when the internal combustion engine is in a predetermined operating state And clogging determining means for determining that a clog has occurred in the exhaust gas recirculation passage when the opening degree of the valve is larger than a predetermined reference opening degree.

This is because if the flow control valve is already fully opened when it is necessary to increase the amount of recirculated gas, the opening of the intake throttle valve is adjusted to reduce the negative pressure of the intake pipe acting on the exhaust gas recirculation passage. It is assumed that the size is adjusted.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of a clogging detection device for an exhaust gas recirculation device according to the present invention will be described below with reference to the drawings.

<First Embodiment> First, a first embodiment of a clogging detection device for an exhaust gas recirculation device will be described with reference to FIGS.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which a blockage detection device for an exhaust gas recirculation device according to the present invention is applied, and an intake / exhaust system thereof. The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cylinder diesel engine having four cylinders 2. In the internal combustion engine 1, a fuel injection valve 3 for directly injecting fuel into the combustion chamber of each cylinder 2 and a crankshaft as an engine output shaft of the internal combustion engine 1 have a predetermined angle (for example, 15 degrees).
°) A crank position sensor 4 that outputs a pulse signal each time it rotates and a water temperature sensor 5 that outputs an electric signal corresponding to the temperature of cooling water flowing through a water jacket (not shown) of the internal combustion engine 1 are attached.

The above-described fuel injection valve 3 is connected to a pressure storage chamber (common rail) 7 via a fuel pipe 6. The common rail 7 is connected to a fuel pump 9 attached to the fuel tank 8 via a fuel pipe 10 and to the fuel tank 8 via a return pipe 11.

When the fuel pressure in the common rail 7 is lower than a predetermined maximum pressure, the valve is closed at the connection point of the return pipe 11 in the common rail 7 to cut off the conduction between the common rail 7 and the return pipe 11. When the fuel pressure in the common rail 7 becomes equal to or higher than the maximum pressure, a pressure regulating valve 12 is provided which opens to allow conduction between the common rail 7 and the return pipe 11.

A fuel pressure sensor 13 for outputting an electric signal corresponding to the fuel pressure in the common rail 7 is attached to the common rail 7. In the fuel system configured as described above, the fuel pump 9 pumps up the fuel stored in the fuel tank 8 and sends the pumped fuel to the common rail 7 through the fuel pipe 10. The fuel supplied from the fuel pump 9 to the common rail 7 is accumulated until the pressure of the fuel reaches a desired target pressure. Common rail 7
The fuel accumulated to the target pressure in
And is distributed and supplied to the fuel injection valve 3 of each cylinder 2 via Each fuel injection valve 3 opens when a drive current is applied, and injects fuel at a target pressure supplied from the common rail 7 into the combustion chamber of each cylinder 2.

In the fuel system described above, the common rail 7
When the fuel pressure in the chamber increases to the maximum pressure or more, the pressure regulating valve 10 opens. In this case, a part of the fuel stored in the common rail 5 is returned to the fuel tank 6 via the return pipe 9, and as a result, the common rail 5
The fuel pressure inside is reduced.

Next, an intake branch pipe 14 is connected to the internal combustion engine 1. Each branch pipe of the intake branch pipe 14 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown). The intake branch pipe 14 is connected to an intake pipe 15, and the intake pipe 15 is connected to an air cleaner box 16.

At a position immediately downstream of the air cleaner box 16 in the intake pipe 15, an air flow meter 17 for outputting an electric signal corresponding to the mass of intake air flowing through the intake pipe 15, and a flow through the intake pipe 15. An intake air temperature sensor 18 that outputs an electric signal corresponding to the intake air temperature is attached.

A portion of the intake pipe 15 downstream of the air flow meter 17 is provided with a compressor housing 1 of a centrifugal supercharger (turbocharger) 19 operated by using heat energy of exhaust gas discharged from the internal combustion engine 1 as a driving source.
9a is provided.

In the portion of the intake pipe 15 downstream of the compressor housing 19a, there is provided an intercooler 20 for cooling fresh air which has been compressed in the compressor housing 19a and has become high temperature.
In addition, as the intercooler 20, an air-cooled intercooler that dissipates heat of fresh air by using traveling wind generated when a vehicle equipped with the internal combustion engine 1 travels, and heat of fresh air and predetermined cooling water is used. For example, a water-cooled intercooler that lowers the temperature of fresh air by performing heat exchange between the two can be exemplified.

An intake throttle valve (throttle valve) 21 for adjusting the flow rate of intake air flowing through the intake pipe 15 is provided at a position downstream of the intercooler 20 in the intake pipe 15. The throttle valve 21 is provided with a throttle actuator 22 for opening and closing the throttle valve 21 and a throttle position sensor 23 for outputting an electric signal according to the opening of the throttle valve 21.

The throttle actuator 22
For example, a built-in electric actuator that includes a stepper motor or the like and drives the opening and closing of the throttle valve 21 in accordance with the magnitude of the applied power, and a diaphragm that is displaced in conjunction with the throttle valve 21 and has a built-in negative pressure A negative pressure type actuator for opening and closing the throttle valve 21 by displacing the diaphragm according to the size of the diaphragm can be exemplified.

In the intake system configured as described above, the fresh air that has flowed into the air cleaner box 16 is subjected to an air cleaner (not shown) in the air cleaner box 16 to remove dust and dirt from the fresh air. Through the compressor housing 19a of the centrifugal supercharger 19.

The intake air flowing into the compressor housing 19a is compressed by rotation of a compressor wheel provided in the compressor housing 19a. Fresh air that has been compressed in the compressor housing 19a and has become high temperature is cooled by the intercooler 20.

The fresh air cooled by the intercooler 20 is guided to the intake branch pipe 14 with the flow rate adjusted by the throttle valve 21 as necessary. Fresh air guided to the intake branch pipe 14 passes through each branch pipe of the intake branch pipe 14 and passes through each cylinder 2.
To the combustion chamber.

The fresh air distributed to the combustion chamber of each cylinder 2 burns using the fuel injected from the fuel injection valve 3 as an ignition source. Next, an exhaust branch pipe 24 is connected to the internal combustion engine 1. Each branch pipe of the exhaust branch pipe 24 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch pipe 24 is provided in the turbine housing 1 of the centrifugal supercharger 19.
9b, it is connected to the exhaust pipe 25. The exhaust pipe 25 is connected downstream to a muffler (not shown).

A portion of the exhaust branch pipe 24 located immediately upstream of the turbine housing 19b and the exhaust 25
Is connected to a portion located immediately downstream of the turbine housing 19b by a bypass passage 26 that bypasses the turbine housing 19b.

The bypass passage 26 is provided with a waste gate valve 27b comprising a valve 27a for opening and closing the bypass passage 26 and an actuator 27b for driving the valve 27a to open and close.

The actuator 27b is connected to the intake pipe 15 located immediately downstream of the compressor housing 19a via a working pressure passage 28, and the pressure of fresh air flowing in the intake pipe 15 immediately downstream of the compressor housing 19a ( In other words, the valve 27a is opened and closed using the pressure of the fresh air compressed in the compressor housing 19a).

Specifically, when a pressure less than a predetermined pressure is applied from the intake pipe 15 via the operating pressure passage 28 to the actuator 27b, the actuator 27b holds the valve body 27a at the valve closing position, and operates from the intake pipe 15. When a pressure equal to or higher than a predetermined pressure is applied through the pressure passage 28, the valve 27a is driven to open.

In the exhaust pipe 25, a first exhaust purification catalyst 29 and a DPF (Diesel Particulate Filter) 30 are provided at a portion downstream of the connection portion of the bypass passage 26.
And a second exhaust purification catalyst 31 are sequentially provided from the upstream side.

The first and second exhaust gas purifying catalysts 2
Reference numerals 9 and 31 denote catalysts for purifying harmful gas components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas.

The first and second exhaust purification catalysts 29, 3
For example, when the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is near the stoichiometric air-fuel ratio, hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) contained in the exhaust gas are included. A three-way catalyst for purifying the exhaust gas, stores nitrogen oxides (NOx) contained in the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is in an oxygen excess state (lean state), and stores it when the oxygen concentration of the inflowing exhaust gas decreases NOx storage-reduction catalyst for reducing while releasing nitrogen oxides (NOx), a reducing agent for reducing the nitrogen oxides (NOx) when the air-fuel ratio of the inflowing exhaust gas is in an oxygen excess state (lean state) And the like. A selective reduction-type NOx catalyst for reducing and purifying nitrogen oxides (NOx) contained in the exhaust gas when NO is present, or a catalyst formed by appropriately combining the above-mentioned catalysts can be exemplified.

The above-mentioned DPF 30 is used to remove particulate matter (P) such as soot (black smoke) and unburned fuel components contained in exhaust gas.
M: a filter that collects Particulate Matter.
The DPF 30 is made of, for example, a porous material as a base material,
Alternately, a first flow path in which the upstream end is open and the downstream end is closed, and a second flow path in which the upstream end is closed and the downstream end is open They are arranged in a honeycomb shape.

In such a DPF 30, the DPF 30
The exhaust gas that has flowed into the first flow path first flows into the first flow path. The exhaust gas that has flowed into the first flow path flows into the second flow path through a hole in a partition wall that separates the first flow path and the second flow path, and then exhausts downstream from the open end downstream of the second flow path to the DPF 30. It is discharged to the pipe 25. The PM contained in the exhaust gas is physically adsorbed by the partition wall when the exhaust gas passes through the hole of the partition wall separating the first flow path and the second flow path, and is thereby removed from the exhaust gas. Become.

An exhaust temperature sensor 32 for outputting an electric signal corresponding to the temperature of the exhaust gas flowing through the exhaust pipe 25 is provided at a portion of the exhaust pipe 25 located between the DPF 30 and the second exhaust purification catalyst 31. Is attached.

In the exhaust pipe 25, a portion downstream of the second exhaust gas purification catalyst 31 is provided.
An exhaust throttle valve 33 that adjusts the flow rate of exhaust gas flowing through the inside, and an exhaust throttle actuator 34 that opens and closes the exhaust throttle valve 33 according to the magnitude of applied power or negative pressure.
Are provided.

The exhaust throttle valve 33 operates to reduce the flow rate of exhaust gas in the exhaust pipe 25 when the internal combustion engine 1 is in a warm-up operation state or the like, thereby increasing the load on the internal combustion engine 1. Of the internal combustion engine 1 and the warming-up of the intake and exhaust system components.

In the exhaust system configured as described above, the burned gas burned in the combustion chamber of each cylinder 2 of the internal combustion engine 1 passes through the exhaust port of each cylinder 2 to each branch pipe of the exhaust branch pipe 24. Is discharged. The burned gas (exhaust) discharged to each branch of the exhaust branch 24 is supplied to the turbine housing 19 of the centrifugal supercharger 13.
b.

When the exhaust gas flows into the turbine wheel 19b, the thermal energy of the exhaust gas is transferred to the turbine housing 19b.
b is converted into rotational energy of a turbine wheel rotatably supported in b. The rotational energy of the turbine wheel is transmitted to the compressor wheel of the compressor housing 19a, and the compressor wheel compresses fresh air by the rotational energy transmitted from the turbine wheel.

When the pressure of the fresh air compressed in the compressor housing 19a (the pressure of the fresh air in the intake pipe 25 downstream of the compressor housing 19) rises to a predetermined pressure or more, the pressure of the fresh air is increased to the operating pressure passage. 28 to the actuator 27b.
b drives the waste gate valve 27a to open.

In this case, a part of the exhaust gas flowing through the exhaust branch pipe 24 flows to the exhaust pipe 25 via the bypass passage 26, so that the flow rate of the exhaust gas flowing into the turbine housing 19b decreases and flows into the turbine housing 19b. Exhaust heat energy, in other words, turbine housing 19b
, The heat energy converted into the rotational energy of the turbine wheel decreases. As a result, the rotational energy transmitted from the turbine wheel to the compressor wheel decreases, and the pressure of fresh air compressed in the compressor housing 19a does not increase to a predetermined pressure or more.

The exhaust gas discharged from the turbine housing 19b passes through an exhaust pipe 25 to the first exhaust gas purifying catalyst 2.
Flow into 9. The first exhaust gas purification catalyst 29 purifies harmful gas components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas.

The exhaust gas that has passed through the first exhaust gas purifying catalyst 29 subsequently flows into the DPF 30, and the PM contained in the exhaust gas is removed by the DPF 30. The exhaust flowing out of the DPF 30 flows into the second exhaust purification catalyst 31.

In the second exhaust gas purifying catalyst 31, harmful gas components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) remaining in the exhaust gas, that is, the first exhaust gas The harmful gas components that have not been purified by the purification catalyst 29 are purified. The exhaust gas that has passed through the second exhaust gas purification catalyst 31 is discharged into the atmosphere via the exhaust pipe 25 and the muffler.

On the other hand, an exhaust gas recirculation passage (EGR passage) 100 is connected to the exhaust branch pipe 24,
The passage 100 is connected to the intake branch pipe 14. An EGR valve 101 that opens and closes an open end of the EGR passage 100 in the intake branch pipe 14 is provided at a connection portion between the EGR passage 100 and the intake branch pipe 14. The EGR valve 101 is configured by an electromagnetic valve or the like, and can change the opening degree according to the magnitude of the applied power. This EGR valve 101 realizes the flow rate regulating valve according to the present invention.

The EGR valve 101 includes the EGR valve 10
An EGR opening sensor 102 that outputs an electric signal corresponding to the opening degree of 1 is attached. Examples of the EGR opening sensor 102 include a potentiometer having a metal contact that slides on a resistor in conjunction with the opening and closing operation of the EGR valve 101, and a slot disk that rotates in conjunction with the opening and closing operation of the EGR valve 101. And a photointerrupter-type sensor including a photointerrupter including an LED and a phototransistor arranged to face each other with a slot disk interposed therebetween.

In the middle of the EGR passage 100, the EG
An EGR cooler 103 for cooling exhaust gas (hereinafter, referred to as EGR gas) flowing in the R passage 100 is provided. The EGR cooler 103 implements a cooling unit according to the present invention.

Two pipes 104 and 105 are connected to the EGR cooler 103, and these two pipes 104 and 105 are connected to each other.
105 is connected to a radiator 106 for radiating the heat of the cooling water of the internal combustion engine 1 to the atmosphere.

One of the two pipes 104 and 105 is a pipe for guiding a part of the cooling water cooled in the radiator 106 to the EGR cooler 103, and the other pipe 104. 105 is the E
This is a pipe for guiding the cooling water circulated in the GR cooler 103 to the radiator 106. In the following, the pipe 104 is referred to as a cooling water introduction pipe 104, and the pipe 1
05 is referred to as a cooling water outlet pipe 105.

An opening / closing valve 107 for opening and closing a flow path in the cooling water outlet pipe 105 is provided in the middle of the cooling water outlet pipe 105. The on-off valve 107 is configured by an electromagnetically driven valve or the like that opens when drive power is applied.

The exhaust gas recirculation mechanism (E
In the GR mechanism, when the EGR valve 101 is opened, the EGR
The passage 100 becomes conductive, and a part of the exhaust gas flowing in the exhaust branch pipe 24 passes through the EGR passage 100 and the intake branch pipe 1
It is led to 4.

At this time, when the on-off valve 107 is in the open state, the circulation path connecting the radiator 106, the cooling water introduction pipe 104, the EGR cooler 103, and the cooling water outlet pipe 105 is in a conductive state, and is cooled by the radiator 106. The cooled water circulates through the EGR cooler 103. as a result,
In the EGR cooler 103, heat exchange is performed between the EGR gas flowing in the EGR passage 100 and the cooling water circulating in the EGR cooler 103, so that the EGR gas is cooled.

The EGR gas recirculated from the exhaust branch pipe 24 to the intake branch pipe 14 through the EGR passage 100 is supplied to the intake branch pipe 1
Each cylinder 2 while mixing with fresh air flowing from the upstream of 4
And the fuel injected from the fuel injection valve 3 is combusted as an ignition source.

Here, the EGR gas contains an inert gas component such as water (H ₂ O) or carbon dioxide (CO ₂ ) which does not burn itself and has endothermic properties, such as water (H ₂ O) and carbon dioxide (CO ₂ ). ing. For this reason, when the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered, thereby suppressing the generation amount of nitrogen oxides (NOx).

Further, the EGR cooler 103
When the gas is cooled, the temperature of the EGR gas itself decreases, and the volume of the EGR gas decreases.
When the R gas is supplied into the combustion chamber, the ambient temperature in the combustion chamber does not unnecessarily increase, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber is unnecessarily reduced. Absent.

An electronic control unit (ECU) 35 for controlling the internal combustion engine 1 is provided in the internal combustion engine 1 configured as described above. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's requirements.

The ECU 35 includes a crank position sensor 4, a water temperature sensor 5, a fuel pressure sensor 13, an air flow meter 17, an intake temperature sensor 18, a throttle position sensor 23, an exhaust temperature sensor 32, and an EGR opening degree sensor 1.
In addition to various sensors such as 02, an accelerator opening sensor 36 that outputs an electric signal corresponding to the operation amount (accelerator opening) of an accelerator pedal (not shown) is connected via electric wiring. The data is input to the ECU 35.

On the other hand, the ECU 35 includes the fuel injection valve 3, the fuel pump 9, the throttle actuator 22, the exhaust throttle actuator 34, the EGR valve 101, and the on-off valve 10.
7 and the like are connected via electric wiring,
U35 can be controlled.

Here, as shown in FIG. 2, the ECU 35 is connected to the CP 35
U41, ROM42, RAM43, backup RAM44, input port 45, and output port 46.
A D converter (A / D) 47 is provided.

The input port 45 receives the output signals of a sensor such as the crank position sensor 4 which outputs a digital signal, and outputs those output signals to the CPU.
41 and the RAM 43.

The input port 45 includes a water temperature sensor 5, a fuel pressure sensor 13, an air flow meter 17, an intake temperature sensor 18, a throttle position sensor 23, an exhaust temperature sensor 32, an accelerator opening sensor 36, and an EGR opening sensor 102. And the like, input through an A / D 47 of a sensor that outputs a signal in an analog signal format, and transmit those output signals to the CPU 41 and the RAM 43.

The output port 46 is connected to the fuel injection valve 3, the fuel pump 9, the throttle actuator 22, the exhaust throttle actuator 34, the EGR valve 101, and the on-off valve 10.
7 and the like via electric wiring, and outputs a control signal output from the CPU 41 to the fuel injection valve 3, the fuel pump 9, the throttle actuator 22, the exhaust throttle actuator 34, the EGR valve 101, or the on-off valve 10.
Send to 7.

The ROM 42 includes a fuel injection valve control routine for controlling the fuel injection valve 3, a fuel pump control routine for controlling the fuel pump 9, and the throttle valve 21.
Control routine for controlling the exhaust throttle valve 33, an exhaust throttle control routine for controlling the exhaust throttle valve 33, an EGR control routine for controlling the EGR valve 101, the on-off valve 1
07 in addition to various application programs such as an EGR cooling control routine for controlling the EGR cooler 10.
An EGR clogging determination control routine for detecting the clogging of No. 3 is stored.

The ROM 42 stores various control maps in addition to the application programs described above. The control map includes, for example, a fuel injection amount control map indicating a relationship between an operation state of the internal combustion engine 1 and a basic fuel injection amount (basic fuel injection time), and a relation between the operation state of the internal combustion engine 1 and the basic fuel injection timing. A fuel injection timing control map, a common rail pressure control map showing a relationship between an operating state of the internal combustion engine 1 and a target pressure in the common rail 7,
Target pressure and the discharge pressure of the fuel pump 9 (fuel pump 9
, A fuel discharge pressure control map showing the relationship between the operating state of the internal combustion engine 1 and the opening degree of the throttle valve 22, a throttle opening degree control map showing the relationship between the operating state of the internal combustion engine 1 and the opening of the throttle valve 22, and the operating state of the internal combustion engine 1 and the exhaust throttle valve. An exhaust throttle opening control map showing the relationship with the opening of the engine 33, the operating state of the internal combustion engine 1 and the EGR valve 1
EGR valve opening control map showing the relationship with the opening of 01, cooler operating timing control showing the relationship between the operating state of the internal combustion engine 1 and the operating timing of the EGR cooler 103 (in other words, the opening timing of the on-off valve 107). Such as a map.

The RAM 43 stores an output signal from each sensor, a calculation result of the CPU 41, and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 26 outputs a pulse signal. These data are rewritten to the latest data each time the crank position sensor 26 outputs a pulse signal.

The backup RAM 44 is a non-volatile memory capable of storing data even after the operation of the internal combustion engine 1 is stopped. The CPU 41 operates in accordance with an application program stored in the ROM 42 to execute fuel injection valve control, fuel pump control, throttle control, exhaust throttle control, EGR control, and EGR cooling control, and constitute the gist of the present invention. The EGR blockage determination control is executed.

For example, in the fuel injection valve control, the CPU 41
First, the amount of fuel injected from the fuel injection valve 3 is determined, and then the timing for injecting fuel from the fuel injection valve 3 is determined. When determining the fuel injection amount, the CPU 41 determines R
The engine speed and the output signal (accelerator opening) of the accelerator opening sensor 36 stored in the AM 43 are read. C
The PU 41 accesses a fuel injection amount control map, and calculates a basic fuel injection amount (basic fuel injection time) corresponding to the engine speed and the accelerator opening. CPU 41
Is the output signal value of the water temperature sensor 5, the air flow meter 17
The basic fuel injection time is corrected based on the output signal value of the intake air temperature sensor 18 or the like, and the final fuel injection time is determined.

When determining the fuel injection timing, the CPU 4
1 accesses a fuel injection start timing control map and calculates a basic fuel injection timing corresponding to the engine speed and the accelerator opening. The CPU 41 corrects the basic fuel injection timing using the output signal value of the water temperature sensor 5, the output signal value of the air flow meter 17, or the output signal value of the intake air temperature sensor 18 as a parameter, and determines the final fuel injection timing.

When the fuel injection time and the fuel injection timing are determined, the CPU 41 compares the fuel injection timing with the output signal of the crank position sensor 4 and determines that the output signal of the crank position sensor 4 is equal to the fuel injection start time. At the time coincident with the timing, application of drive power to the fuel injection valve 3 is started. The CPU 41 stops applying the driving power to the fuel injection valve 3 when the elapsed time from the start of the application of the driving power to the fuel injection valve 3 reaches the fuel injection time.

In the fuel injection control, when the operating state of the internal combustion engine 1 is the idling operation state, the CPU 41 determines the output signal value of the water temperature sensor 5 and the rotational force of the crankshaft like a compressor of a vehicle interior air conditioner. The target idle rotation speed of the internal combustion engine 1 is calculated using the operating states of the auxiliary devices operating using the parameters as parameters. And CPU4
1 performs feedback control of the fuel injection amount so that the actual idle speed matches the target idle speed.

Next, in the fuel pump control, the CPU 41
Reads the engine speed and the accelerator opening stored in the RAM 43, for example. The CPU 41 accesses a common rail pressure control map and calculates a target pressure corresponding to the engine speed and the accelerator opening. continue,
The CPU 41 accesses the fuel discharge pressure control map,
A discharge pressure of the fuel pump 9 corresponding to the target pressure (a drive current of the fuel pump 9) is calculated, and the calculated drive current is applied to the fuel pump 9.

At this time, the CPU 41 applies a voltage to the fuel pump 9 based on a difference between an output signal value (actual fuel pressure in the common rail 7) of the fuel pressure sensor 13 attached to the common rail 7 and the target pressure. Feedback control of the drive current value to be performed is performed.

In the throttle control, the CPU 41
Reads the engine speed and the accelerator opening stored in the RAM 43, for example. The CPU 41 accesses a throttle opening control routine and calculates a target throttle opening corresponding to the engine speed and the accelerator opening. The CPU 41 applies drive power corresponding to the throttle opening to the throttle actuator 22. Further, the CPU 41 performs feedback control of the throttle actuator 22 based on a difference between an output signal value (actual throttle opening) of the throttle position sensor 23 and the target throttle opening.

In the exhaust throttle control, the CPU 41 controls the exhaust throttle valve 33 when the internal combustion engine 1 is in a warm-up operation state after a cold start or when the vehicle interior heater is operating.
Exhaust throttle actuator 34 to drive the valve in the valve closing direction.
Control. In this case, the load on the internal combustion engine 1 increases, and the fuel injection amount increases accordingly. As a result, the calorific value of the internal combustion engine 1 increases, the warm-up of the internal combustion engine 1 is promoted, and the heat source of the vehicle interior heater is secured.

In the EGR control, the CPU 41
The engine speed, the output signal of the water temperature sensor 5 (cooling water temperature), the output signal of the accelerator opening sensor 36 (accelerator opening), and the like stored in the memory 3 are read out to determine whether the execution conditions of the EGR control are satisfied. Is determined.

The above-mentioned EGR control execution conditions are as follows: the coolant temperature is equal to or higher than a predetermined temperature, the internal combustion engine 1 has been continuously operated for a predetermined time or more from the start, and the change amount of the accelerator opening is a positive value. Conditions such as certain conditions can be exemplified.

If it is determined that the EGR control execution condition described above is satisfied, the CPU 41 accesses the EGR valve opening control map based on the engine speed and the accelerator opening to obtain the engine speed. And the opening of the EGR valve 101 corresponding to the accelerator opening is calculated.

On the other hand, if it is determined that the EGR control execution condition as described above is not satisfied, the CPU 41 determines whether E
Control is performed so as to keep the GR valve 101 in the fully closed state. Furthermore,
In the EGR control, the CPU 41 performs a so-called EGR valve feedback control in which the opening degree of the EGR valve 101 is feedback-controlled using the intake air amount of the internal combustion engine 1 as a parameter.

In the EGR valve feedback control, for example, the CPU 41 determines the target intake air amount of the internal combustion engine 1 using the accelerator opening, the engine speed and the like as parameters.
At this time, the relationship between the accelerator opening, the engine speed, and the target intake air amount may be mapped in advance, and the target intake air amount may be calculated from the map, the accelerator opening, and the engine speed. .

When the target intake air amount is determined by the above procedure, the CPU 41 reads out the output signal value (actual intake air amount) of the air flow meter 17 stored in the RAM 43, and reads the actual intake air amount and the target intake air amount. Compare with air volume.

If the actual intake air amount is smaller than the target intake air amount, the CPU 41 sets the EGR valve 1
01 is closed by a predetermined amount. In this case, the EGR passage 100
The amount of EGR gas flowing into the intake branch pipe 14 from the engine decreases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 decreases. As a result, the amount of fresh air sucked into the cylinder 2 of the internal combustion engine 1 increases by an amount corresponding to the decrease in the EGR gas.

On the other hand, when the actual intake air amount is larger than the target intake air amount, the CPU 41 opens the EGR valve 101 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 14 from the EGR passage 100 increases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 increases. As a result, the amount of fresh air sucked into the cylinder 2 of the internal combustion engine 1 decreases by an amount corresponding to the increase in the EGR gas.

When it is necessary to increase the EGR gas amount, if the EGR valve 101 is already fully opened, the CPU 4
1 controls the throttle actuator 22 to close the throttle valve 21 by a predetermined opening degree. In this case, since the degree of negative pressure of the intake negative pressure in the intake branch pipe 14 located downstream of the throttle valve 21 increases, the EGR passage 1
From 00, the amount of EGR gas sucked into the intake branch pipe 14 increases.

The predetermined amount may be a fixed value that is determined in advance, or a variable value that is changed according to a deviation between the actual intake air amount and the target intake air amount. Is also good.

Next, the EGR gas cooling control is a control executed when the EGR control is in an execution state. This E
In the GR gas cooling control, when the EGR gas cooling condition is satisfied, the CPU 41 opens the on-off valve 107 and circulates a part of the cooling water cooled by the radiator 106 to the EGR cooler 103. The EGR gas flowing through the EGR passage 100 is cooled.

The above EGR gas cooling conditions are as follows: the output signal value (cooling water temperature) of the water temperature sensor 5 is equal to or higher than a predetermined temperature; the engine speed is equal to or higher than a predetermined speed; And the output signal value (exhaust gas temperature) of the exhaust gas temperature sensor 32 is equal to or higher than a predetermined temperature.

Next, the EGR clogging determination control which is the gist of the present invention will be described. The EGR blockage determination control according to the present embodiment is a control for determining whether or not the EGR cooler 103 is clogged.
Is in the EGR control execution region, and EG
This is executed when the R valve feedback control is in the execution state.

In the EGR clogging determination control according to the present embodiment, the CPU 41 determines the opening of the EGR valve 101 when the EGR cooler 103 is not clogged (hereinafter referred to as a reference EGR valve opening) and the EGR clogging. The degree of opening of the EGR valve 101 during execution of the determination control (hereinafter referred to as the determination EGR
(Referred to as a valve opening) to determine whether or not the EGR cooler 103 is clogged.

If the EGR cooler 103 is clogged, the intake branch pipe 14
Since the amount of EGR gas flowing into the internal combustion engine 1 decreases, the amount of EGR gas taken into the internal combustion engine 1 decreases instead of the internal combustion engine 1.
The amount of fresh air to be sucked into the air will increase.

That is, when clogging occurs in the EGR cooler 103, the output signal value (actual intake air amount) of the air flow meter 17 exceeds the target intake air amount. As described above, when the actual intake air amount exceeds the target intake air amount, the EG is controlled by the EGR valve feedback control.
The opening of the R valve 101 is corrected in the valve opening direction to reduce the actual intake air amount to the target intake air amount.

Therefore, the opening of the EGR valve for determination is equal to the reference EGR.
If it is larger than the valve opening, it can be said that the EGR cooler 103 is clogged. By the way, when the operating state of the internal combustion engine 1 changes, the opening degree of the EGR valve 101 is also changed accordingly. Therefore, when detecting the opening degree of the EGR valve for determination, the operating state of the internal combustion engine 1 is based on the reference EGR valve opening state. It must be the same as the operating state when the degree is detected (hereinafter referred to as the reference operating state).

Therefore, the CPU 41 detects the EGR valve opening for determination when the operating state of the internal combustion engine 1 is the same as the reference operating state. The above-mentioned reference operation state is preferably a low-load steady operation state, particularly preferably an idle operation state after completion of the warm-up operation. This is because when the internal combustion engine 1 is in the high load operation state, the flow rate of the exhaust gas discharged from the internal combustion engine 1 is large, and the pressure of the exhaust gas in the exhaust branch pipe 24 tends to increase. Occurs, the amount of EGR gas flowing into the intake branch pipe 14 from the EGR passage 100 is hard to decrease, and the opening of the EGR valve 101 is not corrected in the valve opening direction in the EGR valve feedback control, or Is very small.

Even when the internal combustion engine 1 is in the same operating state as the reference operating state, the air flow meter 1
7, the opening of the EGR valve 101 due to the initial tolerance of the EGR valve 101, the EGR opening sensor 102, etc., and changes in the environment (outside temperature, atmospheric pressure, etc.) in which the vehicle on which the internal combustion engine 1 is mounted is changed. May be larger than the reference opening. In the present embodiment, when the actual EGR valve opening is larger than the reference opening by a predetermined opening or more, the EGR cooler 10
3 was determined to be clogged.

Hereinafter, the EGR clogging determination control according to the present embodiment will be specifically described. The CPU 41 uses the EG
In executing the R clogging determination control, an EGR clogging determination control routine as shown in FIG. 3 is executed. This EG
The R clogging determination control routine is a routine that is repeatedly executed at predetermined time intervals (for example, every time the crank position sensor 4 outputs a pulse signal) under the condition that the EGR valve feedback control is being executed.

In the EGR clogging determination control routine, the CP
The U41 first accesses the EGR abnormality flag storage area set in the RAM 43 in S301, and
It is determined whether "0" is stored in the abnormality flag storage area.

The above-mentioned EGR abnormality flag storage area contains E
“1” is stored when the GR cooler 103 is clogged, and “0” is stored when the EGR cooler 103 is not clogged.

If it is determined in step S301 that "1" is stored in the EGR abnormality flag storage area,
The PU 41 ends the execution of this routine once. on the other hand,
If it is determined in step S301 that “0” is stored in the EGR abnormality flag storage area, the CPU 41
Proceeds to S302, the engine speed from the RAM 43, the output signal value of the accelerator opening sensor 35 (accelerator opening), the fuel injection amount, the output signal value of the water temperature sensor 5 (cooling water temperature),
Various data such as the output signal value (throttle opening) of the throttle position sensor 23 and the drive power applied to the exhaust throttle actuator 34 are read.

In step S303, the CPU 41 executes the processing in step S30.
Based on the various data read in step 2, it is determined whether the operating state of the internal combustion engine 1 is the same as the reference operating state.

At this time, the CPU 41 determines that the engine speed is the same as the engine speed in the reference operating state, and that the accelerator opening is the same as the accelerator opening in the reference operating state.
The fuel injection amount is the same as the fuel injection amount in the reference operation state, the cooling water temperature is the same as the cooling water temperature in the reference operation state, and the throttle opening is the same as the throttle opening in the reference operation state. The drive power applied to the exhaust throttle actuator 34 is the same as the drive power applied to the exhaust throttle actuator 34 in the reference operation state, and the DPF 30 is not clogged.
By determining whether or not conditions such as the non-execution state of the regeneration process of the PF 30 are satisfied, it is determined whether or not the operating state of the internal combustion engine 1 is the same as the reference operating state. It may be.

Further, in addition to the above-described conditions, the CPU 41 considers the operating states of auxiliary equipment such as an air conditioner compressor and a power steering pump, and determines that the operating state of the internal combustion engine 1 is the same as the reference operating state. It may be determined whether or not the vehicle is in an operation state.

If it is determined in step S303 that the operation state of the internal combustion engine 1 is not the same as the reference operation state, the CPU 41 temporarily terminates the execution of this routine.
On the other hand, when it is determined in S303 that the operating state of the internal combustion engine 1 is the same as the reference operating state,
The CPU 41 proceeds to S304, in which the EGR opening sensor 10
The output signal value (the EGR valve opening for determination) is input.

In S305, the CPU 41 executes the
To read the reference EGR valve opening. S306
Then, the CPU 41 compares the opening degree of the EGR valve for judgment inputted in the step S304 with the reference opening degree of the EGR valve read out in the step S305, and determines that the opening degree of the EGR valve for the judgment is a predetermined opening degree from the opening degree of the reference EGR valve. It is determined whether it is larger than the degree.

If it is determined in step S306 that the opening of the determination EGR valve is larger than the reference EGR valve opening by a predetermined amount or more, the CPU 41 determines that the EGR cooler 103 is clogged, and proceeds to step S307. RA
After "1" is written in the EGR abnormality flag storage area of M43, the execution of this routine ends.

On the other hand, in S306, the determination E
If it is determined that the GR valve opening is not larger than the reference EGR valve opening by a predetermined amount or more, the CPU 41 determines that the EGR cooler 103 is not clogged, and proceeds to S308.
After writing "0" in the EGR abnormality flag storage area of the RAM 43, the execution of this routine ends.

As described above, when the CPU 41 executes the EGR clogging determination control routine, the clogging determining means according to the present invention is realized. Therefore, according to the clogging detection device of the exhaust gas recirculation device according to the present embodiment, in the exhaust gas recirculation device for recirculating a part of the exhaust gas flowing through the exhaust system of the internal combustion engine to the intake system, EGR
The clogging of the gas flow path can be detected with high accuracy.

In this embodiment, an example has been described in which the output signal value of the EGR opening sensor 102 is compared with the reference opening to determine whether the EGR cooler 103 is clogged. If the EGR valve 101 is not provided, the driving power applied from the CPU 41 to the EGR valve 101 is compared with the driving power corresponding to the reference opening to determine the EGR.
The clogging of the cooler 103 may be determined.

<Embodiment 2> Next, a second embodiment of the clogging determination device for an exhaust gas recirculation device according to the present invention will be described with reference to FIG. Here, a configuration different from the above-described first embodiment will be described, and a description of the same description will be omitted.

In the first embodiment, the determination EG is used.
Although the example in which the clogging of the EGR cooler 103 is determined by comparing the R valve opening with the reference EGR valve opening has been described, in the present embodiment, instead of the above-described reference opening,
The internal combustion engine 1 is in the reference operating state and the EGR cooler 10
An example in which the clogging of the EGR cooler 103 is determined using the EGR valve opening and the EGR valve opening for determination obtained by the learning control executed when no clogging has occurred in No. 3 will be described.

In this case, the CPU 41 sets the EGR cooler 1
03 is not clogged, for example, when the vehicle equipped with the exhaust gas recirculation device is in a new vehicle state, or when a component of the exhaust gas recirculation device is replaced with a new component, and the EGR valve feedback is performed. When the control is being executed, an EGR valve opening learning control routine as shown in FIG. 4 is executed. The EGR valve opening learning control routine is a routine stored in a predetermined area of the ROM 42 in advance.

In the EGR valve opening learning control routine, CP
First, in S401, the engine speed, the output signal value of the air flow meter 17 (actual intake air amount), the target intake air amount related to the EGR valve feedback control, and the output signal value of the accelerator opening sensor 35 (accelerator Opening), fuel injection amount, output signal value of coolant temperature sensor 5 (cooling water temperature), output signal value of throttle position sensor 23 (throttle opening), drive power applied to exhaust throttle actuator 34, etc. Read data Read various data.

[0139] In S402, the CPU 41 proceeds to S40.
It is determined whether or not the internal combustion engine 1 is in the reference operating state using the data read in 1 as a parameter. Said S
If it is determined in 402 that the internal combustion engine 1 is not in the reference operating state, the CPU 41 executes the above-described processing from S401 again.

On the other hand, if it is determined in S402 that the internal combustion engine 1 is in the reference operating state, the CPU 41
Proceeding to S403, the actual intake air amount read in S401 is compared with the target intake air amount to determine whether or not the actual intake air amount has converged to the target intake air amount.

If it is determined in S403 that the actual intake air amount has not converged to the target intake air amount,
The PU 41 executes the above-described processing after S401 again. If it is determined in S403 that the actual intake air amount has converged to the target intake air amount, the CPU 41
Proceeds to S404, and executes an EGR valve opening learning process. Specifically, the EGR valve opening control map and the internal combustion engine 1
And the output signal value (actual EGR valve opening) of the EGR opening sensor 102, which is determined from the operating state (in this case, the reference operating state), is calculated.
The calculated difference is stored in a predetermined area of the RAM 43 as a learning value.

In S405, the CPU 41 sets a learning number counter C for counting the number of executions of the EGR valve opening learning process.
Is incremented by one. The learning number counter described above may be a register built in the CPU 41, or may be a storage area set in a predetermined area of the RAM 43 for storing the number of times of execution of the learning process.

In S406, the CPU 41 executes the processing in S40.
It is determined whether or not the counter value of the learning number counter: C updated in 5 is equal to or more than a predetermined number (for example, N times).

If it is determined in step S406 that the counter value of the learning number counter C is smaller than the predetermined number N, the CPU 41 executes the above-described processing from step S401 again.

If it is determined in step S406 that the counter value of the learning number counter C is equal to or greater than the predetermined number N, the CPU 41 proceeds to step S407, and the CPU 43 proceeds to step S407.
Is read out, and the average value of the N learning values is calculated.

In step S408, the CPU 41 corrects the previously determined reference EGR valve opening with the average value, and stores the corrected reference EGR valve opening as a new reference EGR valve opening in a predetermined area of the RAM 43. Let it.

When the CPU 41 completes the processing of S408, it terminates the execution of this routine. According to such an EGR valve opening learning control routine, the reference EGR valve opening used for the EGR clogging determination control includes the air flow meter 17, the EGR valve 101, and the EGR opening sensor 102.
Since the value takes into account the initial tolerance of the internal combustion engine 1, a decrease in determination accuracy due to individual differences of the internal combustion engine 1 is prevented, and more accurate EGR blockage determination control can be performed.

<Embodiment 3> Next, a third embodiment of a clogging detection device for an exhaust gas recirculation device according to the present invention will be described with reference to FIG. Here, a configuration different from that of the above-described first embodiment will be described, and a description of a similar configuration will be omitted.

In the first embodiment, the EGR valve 1
The example in which the clogging of the EGR cooler 103 is determined using the opening degree of 01 as a parameter has been described. In the present embodiment, an example in which the clogging of the EGR cooler 103 is determined using the cooling efficiency of the EGR cooler 103 as a parameter will be described.

Here, if the EGR cooler 103 becomes clogged, the heat exchange efficiency of the EGR cooler 103 decreases, and accordingly, the cooling efficiency of the EGR cooler 103 decreases.

Therefore, the cooling efficiency of the EGR cooler 103 when the internal combustion engine 1 is in the reference operation state is the same as when the internal combustion engine 1 is in the reference operation state.
If the cooling efficiency is lower than when no clogging occurs, it can be determined that the EGR cooler 103 is clogging.

The cooling efficiency of the EGR cooler 103 is
The temperature of the EGR gas flowing into the cooler 103 (hereinafter, referred to as cooler inlet gas temperature), the temperature of the EGR gas flowing out of the EGR cooler 103 (hereinafter, referred to as cooler outlet gas temperature), and the cooling flowing into the EGR cooler 103 The water temperature and the temperature can be uniquely obtained.

Specifically, assuming that the cooling efficiency of the EGR cooler 103 is Tin, the temperature of the EGR gas flowing out of the EGR cooler 103 is Tout, the temperature of the EGR gas flowing out of the EGR cooler 103 is Tout, and the cooling water temperature is THW. Cooling efficiency = (Tin−Tout) / (Tin−TH
W).

The method for obtaining the cooler inlet gas temperature Tin is as follows: (1) The EGR cooler 1
A method of directly detecting the cooler inlet gas temperature: Tin by attaching a temperature sensor to a portion located immediately upstream of the turbine 03, and (2) the exhaust gas temperature downstream of the turbine housing 19b and the thermal energy consumed in the turbine housing 19b as parameters. (3) Estimating the cooler inlet gas temperature: Tin using the intake air amount of the internal combustion engine 1, the cooling water temperature, the fuel injection amount, and the cycle efficiency as parameters. And the like.

The method of determining the cooler outgas temperature: Tout is as follows: (4) A method of directly detecting the cooler outgas temperature: Tout by attaching a temperature sensor to a portion of the EGR passage 100 located immediately downstream of the EGR cooler 103.
(5) a method of calculating the cooler outlet gas temperature: Tout using the EGR rate, the intake air temperature downstream of the intercooler 20 and the intake air temperature of the intake branch pipe 14 downstream of the EGR valve 101 as parameters, and (6) the intake air in the intake branch pipe 14. Pressure, intake pipe base filling efficiency, and intake branch pipe 1 downstream of EGR101
Assumption value of intake air temperature at 4: T and intercooler 20
A temporary cooler outlet gas temperature is determined from the downstream intake air temperature, and an intake air temperature T ′ in the intake branch pipe 14 downstream of the EGR 101 is determined using the temporary cooler outlet gas temperature, and the T ′ matches the T. By performing the convergence calculation as described above, a method of calculating the true cooler outlet gas temperature: Tout can be exemplified.

In this embodiment, the cooler inlet gas temperature: T
The method (2) described above will be described as an example of the method of obtaining in, and the method (5) described above will be described as an example of the method of obtaining the cooler outlet gas temperature: Tout.

FIG. 5 is a diagram showing a schematic configuration of an internal combustion engine to which the clogging determination device for an exhaust gas recirculation device according to the present embodiment is applied and an intake / exhaust system thereof. In FIG. 5, the intake branch pipe 1
4, an intake temperature sensor 50 that outputs an electric signal corresponding to the temperature of intake air (mixed gas of fresh air and EGR gas) flowing in the intake branch pipe 14 is provided at a portion downstream of the connection portion with the EGR passage 100. Installed.

Further, the intake branch pipe 14 is
An intake pipe pressure sensor 51 for outputting an electric signal corresponding to the pressure of the intake air (supercharging pressure) in the inside is attached. In the following, the intake pipe 15 immediately downstream of the air cleaner box 16 will be described.
The intake air temperature sensor 18 attached to the intake manifold 14 is referred to as a first intake air temperature sensor 18, and the intake air temperature sensor 50 attached to the intake branch pipe 14 is referred to as a second intake air temperature sensor 50.

The procedure for estimating the cooler inlet gas temperature: Tin and the cooler outlet gas temperature: Tout will be described below. First, when estimating the cooler inlet gas temperature: Tin, the CPU 41
Is the output signal value of the exhaust gas temperature sensor 32 (exhaust gas temperature downstream of the turbine housing 19b) and the air flow meter 17
Output signal value (the amount of fresh air sucked into the internal combustion engine 1) and
An output signal (supercharging pressure) of the intake pipe pressure sensor 51 is input.

The CPU 42 uses the output signal value (supercharging pressure) of the intake pipe pressure sensor 51 and the output signal value of the air flow meter 17 (the amount of fresh air sucked into the internal combustion engine 1) as parameters, and uses it as a parameter. , In other words, the turbine expansion ratio of the turbine housing 19b.

Subsequently, the CPU 42 sets the exhaust temperature sensor 3
Then, the temperature of the exhaust gas before flowing into the turbine housing 19b, that is, the cooler inlet gas temperature: Tin, is calculated based on the output signal value of No. 5 and the turbine expansion ratio.

Here, assuming that the output signal value of the exhaust temperature sensor 35 is T1, the turbine expansion ratio is P1, the output signal value of the intake pipe pressure sensor 51 is P2, and the turbine efficiency of the turbine housing 19b is ηt, The following theoretical formula is established. ηt = (Tin−T1) / (Tin (1-1 / (P1 / P2))
(＾ 0.248) The turbine efficiency: ηt is the turbine housing 19b
Since it is a unique value, it may be obtained experimentally in advance and stored in the ROM 42.

Accordingly, by substituting the output signal value of the exhaust temperature sensor 35: T1, the turbine expansion ratio P1, the output signal value of the intake pipe pressure sensor 51, P2, and the turbine housing 19b into the above-described theoretical formula, Cooler inlet gas temperature: Tin is determined.

Next, when estimating the cooler outlet gas temperature: Tout, the CPU 41 determines the output signal value of the air flow meter 17 (the amount of fresh air sucked into the internal combustion engine 1) and the first intake air temperature sensor. 18 (the intake air temperature before flowing into the compressor housing 19a), the output signal value of the second intake air temperature sensor 50 (the intake air temperature downstream of the EGR valve 101), and the output signal value of the intake pipe pressure sensor 51 ( (Supercharging pressure).

Subsequently, the CPU 41 determines the ratio (EGR) of the amount of EGR gas contained in the intake air taken into the internal combustion engine 1.
Rate) and the temperature of the intake air flowing out of the intercooler 20 are calculated.

When determining the EGR rate, the CPU 41 determines the total amount of intake air (the sum of the amount of fresh air and the amount of EGR gas to be taken into the internal combustion engine 1) and the amount of intake air to be taken into the internal combustion engine 1. The EGR rate is calculated using the output signal value (the amount of fresh air sucked into the internal combustion engine 1) as a parameter.

Here, assuming that the EGR rate is EGRR, the output signal value of the air flow meter 17 is GA, and the total amount of intake air taken into the internal combustion engine 1 is GALL, the EGR rate can be expressed by the following equation. EGRR = (GALL−GA) / GALL The total amount of intake air taken into the internal combustion engine 1: GALL is an output signal value (supercharging pressure) of the intake pipe pressure sensor 51, an intake pipe base filling efficiency specific to the internal combustion engine 1, and the like. Can be obtained by integrating The aforementioned intake pipe base filling efficiency can be expressed as a function of the engine speed,
It may be determined experimentally in advance.

When calculating the temperature of the intake air after passing through the intercooler 20, the CPU 41 first uses the running speed of the vehicle equipped with the internal combustion engine 1 and the output signal value of the air flow meter 17 as parameters. Calculate the cooling efficiency.

Subsequently, the CPU 42 substitutes the compressor efficiency of the compressor housing 19a and the output signal value of the first intake air temperature sensor 18 into a theoretical equation relating to the compressor housing 19a, and substitutes the same for the compressor housing 19a.
Temperature of the intake air flowing out of the
Calculates the temperature of the intake air flowing into the.

The theoretical equation for the compressor housing 19a is as follows: ηc is the compressor efficiency of the compressor housing 19a, and T is the output signal value of the first intake air temperature sensor 18.
2. The output signal value of the intake pipe pressure sensor 51 is P2, the pressure of the intake air flowing out of the compressor housing 19a is P3,
Assuming that the temperature of the intake air flowing out of the compressor housing 19a is T3, ηc = T2 * ((P3 / P2) ＾ 0.286-1) / (T3
−T2).

The compressor efficiency: ηc is a value unique to the compressor housing 19a, and the output signal value of the air flow meter 17 and the pressure of the intake air flowing out of the compressor housing 19a: P3 can be obtained as parameters. Of the intake air flowing out of the compressor: P3 can be obtained by subtracting the pressure loss in the intercooler 20 from the output signal value (supercharging pressure) of the intake pipe pressure sensor 51.

The CPU 42 calculates the intake air temperature after passing through the intercooler 20 from the cooling efficiency of the intercooler 20 and the temperature of the intake air flowing into the intercooler 20, which are obtained by the above-described method.

When the EGR rate and the intake air temperature after passing through the intercooler 20 are obtained in this manner, the CPU
Reference numeral 41 denotes the EGR rate, the intake air temperature after passing through the intercooler 20, and the output signal value of the second intake air temperature sensor 50 (the intake air temperature downstream of the EGR valve 101, that is, the fresh air cooled by the intercooler 20). And the intake air temperature after the EGR gas is mixed) as a parameter to calculate the cooler outlet gas temperature: Tout.

Here, assuming that the EGR rate is EGRR, the intake air temperature after passing through the intercooler 20 is Tico, and the output signal value of the second intake air temperature sensor 50 is T4, T4 = EGRR * Tout + (1-EGRR) * The equation Tico holds.

Thus, the above equation is used to calculate the EG obtained earlier.
By substituting the R rate, the intake air temperature after passing through the intercooler 20, and the output signal value of the second intake air temperature sensor 50, the cooler outlet gas temperature: Tout is calculated.

The cooler inlet gas temperature: Tin and the cooler outlet gas temperature: Tout estimated by the above-described method are represented by:
EGR cooler cooling efficiency = (Tin−Tout) / (Tin−TH
By substituting into the equation (W), the EGR cooler cooling efficiency is calculated.

Therefore, the CPU 41 compares the EGR cooler cooling efficiency calculated by the above-described procedure with the EGR cooler cooling efficiency when the EGR cooler 103 is not clogged, so that the EGR cooler 103 is clogged. It can be determined whether or not it has occurred.

[0178]

According to the clogging detection device for an exhaust gas recirculation device according to the present invention, the opening degree of the flow control valve when the internal combustion engine is in a predetermined operating condition, the opening degree of the flow control valve when the internal combustion engine is in a predetermined operating condition and the exhaust gas recirculation. By comparing the reference opening based on the opening of the flow control valve when the circulation passage is not clogged, it is possible to determine whether the exhaust recirculation passage is clogged. Become.

At this time, the reference opening is a value determined in consideration of a learned value of the opening detected when the internal combustion engine is in a predetermined operating state and the exhaust recirculation passage is not clogged. By using, it is possible to prevent erroneous determinations due to initial tolerances and the like of the components of the exhaust gas recirculation device, and to improve determination accuracy.

In the exhaust gas recirculation device clogging detection device according to the present invention, when the cooling device is provided in the middle of the exhaust gas recirculation passage, the cooling device is used when the internal combustion engine is in a predetermined operating state. By comparing the cooling efficiency with the cooling efficiency when the internal combustion engine is in a predetermined operating state and the cooling means is not clogged, it is possible to determine whether or not the cooling means is clogged. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which a blockage detection device of an exhaust gas recirculation device according to a first embodiment is applied and an intake / exhaust system thereof;

FIG. 2 is a diagram showing an internal configuration of an ECU.

FIG. 3 is a flowchart illustrating an EGR clogging determination control routine;

FIG. 4 is a flowchart showing an EGR valve opening learning control routine;

FIG. 5 is a diagram showing a schematic configuration of an internal combustion engine to which a blockage detection device for an exhaust gas recirculation device according to a third embodiment is applied and an intake / exhaust system thereof;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 5 ... Water temperature sensor 14 ... Intake branch pipe 15 ... Intake pipe 17 ... Air flow meter 18 ... · First intake air temperature sensor 19 · · · Centrifugal supercharger 19a · · Compressor housing 19b · · Turbine housing 20 · · · Intercooler 21 · · · Throttle valve (intake throttle valve) 24 · · · Exhaust branch pipe 25 · .. exhaust pipe 29 ... first exhaust purification catalyst 30 ... DPF 31 ... second exhaust purification catalyst 32 ... exhaust temperature sensor 50 ... second intake air temperature sensor 51 ... intake pipe pressure Sensor 100 EGR passage (exhaust gas recirculation passage) 101 EGR valve 102 EGR opening degree sensor 103 EGR cooler

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Fukuma 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yasuhiko Otsubo 1 Toyota Town Toyota City, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Hiroki Matsuoka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masaaki Kobayashi 1 Toyota Town Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Motoshiro Endo Aichi 1 Toyota Town, Toyota Prefecture F-term (reference) in Toyota Motor Corporation 3G062 AA05 ED08 FA19 GA06 GA15 GA21

Claims (9)

[Claims] An exhaust recirculation passage that communicates between an exhaust passage and an intake passage of the internal combustion engine; a flow control valve that adjusts a flow rate of exhaust flowing through the exhaust recirculation passage; Exhaust gas recirculation amount control means for controlling the opening degree of the flow control valve, and the exhaust gas when the opening degree of the flow control valve is larger than a predetermined reference opening degree when the internal combustion engine is in a predetermined operating state. Clogging detection means for determining that a clog has occurred in the recirculation passage. 2. An exhaust system according to claim 1, wherein said clogging determination means determines that clogging has occurred in said exhaust gas recirculation passage when an opening of said flow regulating valve is larger than said reference opening by a predetermined opening or more. A blockage detector for the recirculation device. 3. The reference opening is a value determined based on the opening when the internal combustion engine is in a predetermined operating state and the exhaust gas recirculation passage is not clogged. The clogging detection device for an exhaust gas recirculation device according to claim 1, wherein: 4. The reference opening is a value determined based on a learning value of the opening when the internal combustion engine is in a predetermined operating state and the exhaust recirculation passage is not clogged. The clogging detection device for an exhaust gas recirculation device according to claim 1, wherein: 5. The exhaust gas recirculation passage includes cooling means for cooling the exhaust gas flowing in the exhaust gas recirculation passage, and the clogging judging means is configured to perform the operation when the internal combustion engine is in a predetermined operating state. 2. The exhaust gas recirculation passage clogging detection device according to claim 1, wherein it is determined that the cooling means is clogged when the opening of the flow control valve is larger than a predetermined reference opening. 6. The intake passage of the internal combustion engine is provided with an intake throttle valve for adjusting a flow rate of fresh air flowing through the intake passage. The clogging determination device for the exhaust gas recirculation device according to claim 1, wherein in the state, when the opening of the intake throttle valve is at a predetermined opening, the clogging of the exhaust gas recirculation passage is determined. . 7. An exhaust recirculation passage for guiding a part of exhaust gas flowing through an exhaust passage of the internal combustion engine to an intake passage of the internal combustion engine, and exhaust gas provided in the middle of the exhaust recirculation passage and flowing through the exhaust recirculation passage. A cooling means for cooling the cooling means; a cooling efficiency calculating means for calculating a cooling efficiency of the cooling means; and a clogging of the cooling means when the cooling efficiency calculated by the cooling efficiency calculating means falls below a predetermined reference value. Clogging detection means for judging that the clogging has occurred. 8. The cooling means is a water-cooled cooler that performs heat exchange between predetermined cooling water and exhaust gas, and the cooling efficiency calculating means is configured to determine a temperature of exhaust gas flowing into the water-cooled cooler, The exhaust gas recirculation system according to claim 7, wherein the cooling efficiency of the water-cooled cooler is calculated by using, as parameters, a temperature of cooling water supplied to the water-cooled cooler and a temperature of exhaust gas flowing out of the water-cooled cooler. Clogging detector for circulator. 9. An exhaust gas recirculation passage communicating between an exhaust passage and an intake passage of the internal combustion engine; a flow control valve for adjusting a flow rate of exhaust flowing in the exhaust gas recirculation passage; and the exhaust gas recirculation in the intake passage. An intake throttle valve provided at a portion upstream of a connection portion of the passage to adjust a flow rate of intake air flowing through the intake passage; and opening the flow control valve and / or the intake throttle valve according to an operation state of the internal combustion engine. Exhaust recirculation amount control means for controlling the degree, when the opening degree of the flow control valve or the opening degree of the intake throttle valve when the internal combustion engine is in a predetermined operating state is larger than a predetermined reference opening degree, Clogging detection means for determining that a clog has occurred in the exhaust gas recirculation passage.