JP2003206793A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control technology of an internal combustion engine capable of preventing a heater-heating type sensor from being splashed with water attributable to scattered condensed water and using the heater-heating type sensor even in a condition in which condensed water is generated. <P>SOLUTION: The internal combustion engine has an exhaust passage structure in which steam contained in exhaust gas is condensed in an exhaust passage of the internal combustion engine, the condensed water attributable to the condensation thereof forms a condensed water retention part in the exhaust passage, and an air-fuel ratio sensor is provided on a position at which the sensor is easily splashed with scattered condensed water retained in the retention part. The condensed water generated in the retention part is detected, and the fuel injection of the internal combustion engine is gradually controlled so as to suppress a sudden increase in the flow rate of the exhaust gas when the condensed water is detected, preventing the condensed water from being splashed to the air-fuel ratio sensor. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine,
More specifically, the present invention relates to a control technique for an internal combustion engine that prevents element breakage of a heater heating type sensor due to condensed water in an exhaust passage.

[0002]

2. Description of the Related Art In a lean-burn internal combustion engine represented by a diesel engine, various measures are taken to suppress the emission of nitrogen oxides (NOx). One of the countermeasures is to introduce a part of the exhaust gas (inert gas) into the combustion chamber as EGR gas, reduce the combustion temperature by the EGR gas as the inert gas, and generate the amount of nitrogen oxides (NOx). The so-called “EGR control” for reducing the power consumption is generally performed.

More specifically, the exhaust passage and the intake passage are connected to the EG
When the RGR passage is connected and an EGR valve is provided in the EGR passage and EGR gas is to be introduced, first, the EGR valve is opened at an opening degree according to the current operating state, and then,
The air amount (fresh air amount) taken into the combustion chamber is calculated from the output of the air flow meter, and the difference (error) between the calculated air amount and the target air amount is output from the air-fuel ratio sensor provided in the exhaust passage ( This is corrected by feedback control of the EGR valve based on the oxygen concentration of the exhaust gas, and a predetermined ratio (EG
EGR gas is introduced at an R rate). Here, the target air amount is the air amount calculated by the recirculation of the specified EGR gas. That is, during EGR control, feedback control of the EGR valve is performed based on the output of the air-fuel ratio sensor, and as a result, EGR gas flows into the combustion chamber together with fresh air at a predetermined rate.

[0004]

By the way, according to the present inventors, as seen in the above-mentioned EGR control, the EGR control is performed in a situation where the feedback control should be performed by utilizing the output of the air-fuel ratio sensor or the like. A defect caused by was found.

First, when the exhaust passage is cold, such as during cold weather, the exhaust gas is cooled, and the water vapor contained in the exhaust gas is condensed and becomes condensed water in the exhaust passage. Further, when the EGR control is performed in that state, a part of the exhaust gas recirculates to the intake system, the flow rate of the exhaust gas flowing in the exhaust passage decreases, and the condensed water generated by cooling the exhaust gas is It does not flow to the downstream of the exhaust gas, but accumulates in, for example, a bent portion of the exhaust passage. That is, the "retention of condensed water" occurs due to the execution of the EGR control.

On the other hand, a heater is built in the air-fuel ratio sensor used for feedback control and the like. The heater is energized when the sensor element is cold to heat the sensor element and activate the sensor element, thereby enabling the use of the sensor. In other words, it can be said that the heating of the sensor element is necessary to use the sensor when the sensor element is cold, and the appropriate feedback control is performed by the heating of the sensor element.

However, during EGR control, the EGR
Since the condensed water stays due to the control, there is a concern that the sensor may be exposed to water when the condensed water is scattered. That is, the condensed water may adhere to the sensor element during heating, which may cause a phenomenon such as cracking of the sensor element, that is, “thermal shock”. For this reason, in a situation where condensed water is likely to stay, a situation in which the sensor element cannot be heated even though it is desired to heat the sensor element continues, and a problem occurs in that feedback control using the sensor output cannot be performed.

The present invention has been made in consideration of such a technical background, and provides a control technique for an internal combustion engine which prevents the sensor from being exposed to water due to splashing of condensed water and enables early use of the sensor. The challenge is to provide.

[0009]

In order to solve the above technical problems, the present invention has the following configuration. That is,
The water vapor contained in the exhaust gas is condensed in the exhaust passage of the internal combustion engine, and the condensed water generated due to the condensation is provided with an exhaust passage structure that forms a retention portion of the condensed water in the exhaust passage. An internal combustion engine having a heater heating type sensor at a position where it is easily exposed to water due to the scattering of condensed water that has accumulated in the accumulation portion, the condensed water detecting means detecting the condensed water generated in the accumulation portion, and the condensed water detection. When condensate is detected by the means, fuel injection control means for changing the fuel injection control of the internal combustion engine so as to suppress a rapid increase in the flow rate of the exhaust gas, and preventing the condensate from scattering to the heater heating type sensor,
It is characterized by including.

That is, in an internal combustion engine in which condensed water is formed in the exhaust passage due to condensation of water vapor contained in the exhaust gas, it is assumed that the heater-heated sensor is exposed to water due to scattering of the condensed water. To be done. Therefore, in the present invention, the condensed water is detected by the condensed water detecting means, and when the condensed water is detected, the fuel injection control is changed so as to suppress the rapid increase in the flow velocity of the exhaust gas discharged along with the engine operation. Prevent water from splashing. Therefore, it is possible to prevent the heater heating type sensor from being covered with water when the condensed water is scattered, and the sensor can be used even in the situation where the condensed water stays.

It should be noted that the above-mentioned condensed water detecting means is sufficient as long as it is possible to detect the stay of the condensed water, and does not necessarily mean that means for directly detecting the staying condensed water is provided. . Further, changing the fuel injection control in the above means adding to the correction of the existing fuel injection control,
For example, it also includes the concept of switching to specific fuel injection control prepared to prevent a rapid increase in the flow rate of exhaust gas.

Further, the fuel injection control means may increase the fuel injection amount while adding a gradual change control in the increase correction of the fuel injection amount of the internal combustion engine to suppress a rapid increase in the exhaust gas flow velocity.

That is, in the correction of increasing the fuel injection amount, the flow velocity of the exhaust gas also rapidly increases as the engine speed fluctuates. Therefore, in this configuration, the gradual change control is executed in the correction of increasing the fuel injection amount to increase the fuel injection amount. The increase rate of the engine speed in the initial stage of correction is reduced to suppress a rapid increase in the flow rate of exhaust gas.

Further, the fuel injection control means sets the maximum fuel injection amount used for the fuel injection control of the internal combustion engine,
The injection amount may be changed to a smaller amount as compared with the setting so far to suppress a rapid increase in the flow rate of exhaust gas.

That is, if the set value of the maximum fuel injection amount is changed to a small value, it takes a long time to reach the target engine speed in the correction of increasing the fuel injection amount, and as a result, the flow velocity of exhaust gas rapidly increases. Is suppressed.

Further, an operating condition detecting means for detecting an operating condition of the internal combustion engine, and a scattering determining device for determining whether or not the condensed water is in a scattering condition based on the operating condition detected by the operating condition detecting means. The fuel injection control means changes the fuel injection control of the internal combustion engine when the scattering determination means determines that the condensed water is scattered in addition to the retention of the condensed water. A rapid increase in the flow rate of exhaust gas may be suppressed.

In this configuration, the fuel injection control of the internal combustion engine is changed after it is determined whether or not the condensed water is scattered, in addition to the retention of the condensed water. The frequency can be reduced.

The above-mentioned operating condition corresponds to an item having a correlation with the flow velocity of exhaust gas. For example, the operating condition itself such as the accelerated operating condition of the internal combustion engine is intended, and the accelerator opening, Various items such as intake air amount, fuel injection amount, required engine output, etc. can be exemplified.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of an internal combustion engine according to the present invention will be described. In the following description, an example in which the control device of the present invention is applied to a diesel engine, which is a type of a lean-burn internal combustion engine, will be described. It can be changed.

First, as shown in FIG. 1, the internal combustion engine 1 shown in this embodiment has four cylinders 2 (combustion chambers),
A fuel supply system, an intake system, a control system, an exhaust system, etc. are provided as main constituent elements.

The fuel supply system includes a fuel injection valve 3, a common rail (accumulation chamber) 4, a fuel supply pipe 5, a fuel pump 6, and the like, and supplies fuel to each cylinder 2. The fuel injection valve 3 is an electromagnetically driven on-off valve provided for each cylinder 2, and each fuel injection valve 3 is connected to a common rail 4 that serves as a fuel distribution pipe. Further, the common rail 4 is connected to the fuel pump 6 via the fuel supply pipe 5. The fuel pump 6 is rotationally driven using the rotation of the crankshaft 1a, which is the output shaft of the internal combustion engine 1, as a drive source.

In the fuel supply system thus constructed, first, the fuel in the fuel tank (not shown) is pumped up by the fuel pump 6. The pumped fuel is supplied to the common rail 4 via the fuel supply pipe 5. The fuel supplied to the common rail 4 is increased to a predetermined fuel pressure in the common rail 4 and distributed to each fuel injection valve 3. And
When a drive voltage is applied to the fuel injection valve 3 and the fuel injection valve 3 opens, the fuel is injected into each cylinder 2 via the fuel injection valve 3.

On the other hand, the intake system includes an intake pipe 9 and an intake throttle valve 1.
3, an intake branch pipe 8, an air cleaner box 10, an intercooler 16 and the like are provided to form an intake passage for supplying air to each cylinder 2. The intake pipe 9 forms a passage for guiding the air taken in through the air cleaner box 10 to the intake branch pipe 8. The intake branch pipe 8 forms a passage for distributing the air flowing in through the intake pipe 9 to each cylinder 2. An intake air temperature sensor 44a for measuring the temperature of the air flowing into the intake pipe 9 is provided in the vicinity of the connecting portion between the intake pipe 9 and the air cleaner box 10.

Further, a turbocharger 15 (compressor housing 15) for compressing the intake air is provided in the intake pipe 9 extending from the air cleaner box 10 to the intake throttle valve 13.
a) and an intercooler 16 for cooling the air compressed by the turbocharger 15, and an airflow meter 45 for measuring the flow rate of the air flowing into the combustion chamber 2 through the intake pipe 9 is provided upstream of the turbocharger 15. It is provided.

Further, immediately upstream of the intake branch pipe 8, the intake pipe 9 is provided.
The intake throttle valve 13 for adjusting the amount of air flowing into each cylinder 2 through the intake throttle valve 13 is controlled, and the opening degree of the intake throttle valve 13 is controlled by an actuator 14 including a stepper motor or the like. Immediately downstream of the intake throttle valve 13, an intake temperature sensor 44b that measures the temperature in the intake branch pipe 8 and an intake pressure sensor 46 that measures the pipe pressure in the intake branch pipe 8 are provided.

In the intake system thus constructed, first,
Generation of negative pressure due to engine operation and turbocharger 15
The air to be supplied to each cylinder 2 flows into the air cleaner box 10 due to the intake of the air. The air that has flowed into the air cleaner box 10 is dedusted and then flows into the turbocharger 15 via the intake pipe 9. The air flowing into the turbocharger 15 is compressed by the compressor wheel 15a and then cooled by the intercooler 16. Then, after the flow rate is adjusted by the intake throttle valve 13 as necessary, the air flows into the intake branch pipe 8. The air flowing into the intake branch pipe 8 is distributed to each cylinder 2 via each branch pipe, and is used for combustion together with the engine fuel injected and supplied from the fuel injection valve 3. Outputs of various sensors are input to an electronic control unit 30 described later, and are fed back to, for example, fuel injection control of an internal combustion engine.

Next, the control system will be described. The control system is a ROM connected to each other by a bidirectional bus 31.
It is composed of a so-called electronic control unit 30 (ECU) having a (read only memory) 32, a RAM (random access memory) 33, a CPU (central control unit) 34, an input port 35, and an output port 36.

In addition to the output signals of the various sensors described above, a load sensor 41 for detecting the depression amount of the accelerator pedal 40, a crank angle sensor 42 for detecting the number of revolutions of the crankshaft 1a, etc. correspond to the input port 35. It is inputted via the / D converter 37 or directly. On the other hand, the fuel injection valve 3, the reducing agent addition valve 61, the intake throttle valve driving actuator 14, the EGR valve 26, and the like are connected to the output port 36 via a corresponding drive circuit 38.

In the ROM 32, control programs for various devices, control maps referred to in the processing of the programs, and the like are recorded corresponding to each device. Further, in the RAM 33, output signals of various sensors input to the input port 35, control signals output to the output port 36, and the like are recorded as the operation history of the internal combustion engine.
The CPU 34 compares the output signals of the various sensors recorded on the RAM 33 with the control map developed on the ROM 32 on a desired program and compares the various control signals output during the processing with the output port 36. The data is output to the corresponding device via, and various devices are centrally managed.

The exhaust system is provided with an exhaust branch pipe 18 and an exhaust pipe (exhaust passage) 19 and forms an exhaust passage through which exhaust gas discharged from each cylinder 2 is discharged to the outside of the engine body. Further, the catalytic converter 50, the reducing agent addition device 60, the EGR device 2
0, etc., and nitrogen oxides (N
It has a function as an exhaust gas purification device that purifies Ox) and fine particles (for example, soot).

First, the exhaust branch pipe 18 is connected to the exhaust port 18a provided for each cylinder 2 and collects the exhaust gas discharged from the exhaust port 18a to guide it to the turbine housing 15b of the turbocharger 15. Is formed. Further, the exhaust pipe 19 forms a passage from the turbine housing 15b to a silencer (not shown). In the figure, 59 is a known oxidation catalytic converter.

The catalytic converter 50, which is one of the exhaust gas purification devices, is provided with a casing 51 and various exhaust gas purification catalysts 50a and 50b provided in the casing 51, and contains harmful substances in the exhaust gas discharged from the engine body 1. It is equipped with an exhaust gas purification function that purifies the exhaust gas.

More specifically, the turbine housing 15b
The casing 51 is arranged near the outlet of the casing 5 and
An exhaust purification catalyst is built in 1 in the order of the storage reduction type NOx catalyst 50a and the particulate filter 50b from the upstream side to form a catalytic converter 50. In addition,
In the following description, the NOx storage reduction catalyst 50a may be simply referred to as the lean NOx catalyst 50a.

The lean NOx catalyst 50a, which is one of the exhaust purification catalysts, has an exhaust purification action for mainly purifying nitrogen oxides (NOx) in the exhaust gas. More specifically, when the oxygen concentration of the exhaust gas flowing into the lean NOx catalyst 50a is high, the nitrogen oxides (NO
x) is absorbed and the oxygen concentration in the exhaust gas is low, that is, when the air-fuel ratio of the exhaust gas flowing into the lean NOx catalyst 50a is low, the absorbed nitrogen oxides (NOx).
Are reduced and released into the exhaust gas in the form of nitrogen dioxide (NO ₂ ) and nitric oxide (NO), and at the same time, the nitrogen dioxide (NO ₂ )
₂ ) and nitric oxide (NO) are converted into harmless water vapor (H ₂ O) and carbon dioxide (CO ₂ ) by oxidizing unburned combustion components (CO, HC) contained in the exhaust gas. It has the ability to purify exhaust gas.

The structure is, for example, alumina (Al
₂ O ₃ ) as a carrier, and potassium (K), sodium (Na), lithium (Li), cesium (Cs) on the carrier.
Alkali metal such as, or alkaline earth such as barium (Ba), calcium (Ca) or lanthanum (L
a), at least one selected from rare earths such as yttrium (Y), and a noble metal such as platinum (Pt).

A supplementary explanation of the exhaust gas purification action will be given here. In the lean burn internal combustion engine 1 shown in this embodiment,
Usually, combustion is performed in an oxygen excess atmosphere. Therefore, the oxygen concentration of the exhaust gas discharged along with the combustion of the engine hardly decreases until the above-mentioned reducing / releasing action is promoted, and the unburned combustion component (CO,
The amount of HC) is also very small.

Therefore, in this embodiment, the engine fuel (HC), which is a reducing agent, is injected and supplied into the exhaust gas to promote the reduction of the oxygen concentration, and the injected and supplied engine fuel serves as an unburned combustion component. It supplements hydrocarbons (HC) and promotes the above-mentioned exhaust gas purification action. The supply of the reducing agent is performed by a reducing agent adding device 60 described later.
The details will be described later.

One particulate filter 50b
Has an exhaust gas purification effect of oxidizing and burning fine particles such as soot contained in the exhaust gas. More specifically, it has a filter base material 58 carrying an activated oxygen releasing agent, and has an exhaust gas purifying action for purifying the fine particles collected on the filter base material 58 by oxidizing and burning with activated oxygen.

As shown in FIG. 2, the filter substrate 58 alone has a honeycomb shape formed of a porous material such as cordierite, and has a plurality of channels 55 and 56 extending in parallel with each other. is doing. More specifically, the exhaust gas inflow passage 55 whose downstream end is closed by the plug 55a.
And an exhaust gas outflow passage 56 whose upstream end is closed by a plug 56a. The exhaust gas inflow passage 55 and the exhaust gas outflow passage 56 have a thin partition wall 57 in the longitudinal direction of the filter substrate 58. They are arranged side by side.

Further, a layer of a carrier formed of alumina (Al ₂ O ₃ ) or the like is provided on the surface and inside pores of the partition wall 57, and a precious metal catalyst such as platinum (Pt) of a catalyst such as platinum (Pt) is provided on the carrier. In addition, an active oxygen-releasing agent that occludes the excess oxygen when it exists in the surroundings and conversely releases the occluded oxygen in the form of active oxygen when the oxygen concentration decreases is carried.

As the active oxygen releasing agent, alkali metals such as potassium (K), sodium (Na), lithium (Li), cesium (Cs) and rubidium (Rb), barium (Ba), calcium (Ca). ), At least one selected from alkaline earth metals such as strontium (Sr), rare earths such as lanthanum (La) and yttrium (Y), and transition metals such as cerium (Ce) and tin (Sn). Should be used.

Further, preferably, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium (Ca), that is, potassium (K), lithium (Li), cesium (Cs), rubidium (Rb), barium (Ba). ),
It is preferable to use strontium (Sr) or the like.

In the particulate filter 50b thus constructed, the exhaust gas first flows in the order of the exhaust gas inflow passage 55, the partition wall 57, and the exhaust gas outflow passage 56 (arrow a in FIG. 2), and is contained in the exhaust gas. Fine particles such as soot,
In the process of passing through the partition wall 57, it is collected on the surface and inside of the partition wall 57. Then, the fine particles collected in the partition wall 57 are oxidized by activated oxygen that increases by changing the oxygen concentration of the exhaust gas flowing into the partition wall 57 (filter base material) over a plurality of times, and finally a bright flame is generated. It is burned out without being emitted and is removed from the filter substrate 58.

As described above, in this embodiment, the NOx storage reduction catalyst 50a and the particulate filter 50b are arranged in the exhaust passage to purify nitrogen oxides (NOx) and soot and other fine particles contained in the exhaust gas. To do.

In this embodiment, the NOx storage reduction catalyst 50a and the particulate filter 50b are arranged in series as described above. The reason for this is
The reaction heat associated with the oxidation / reduction reaction in the storage reduction NOx catalyst 50a is used to raise the temperature of the particulate filter 50b, and the storage reduction released due to the oxidation / reduction reaction in the storage reduction NOx catalyst 50a. Type NOx
This is based on the reason that the activated oxygen from the catalyst 50a is used for the exhaust gas purification action of the particulate filter 50b. The storage reduction type NOx catalyst 50a carries a substance substantially similar to the activated oxygen releasing agent, as is clear from the above. Therefore, the storage reduction type NOx catalyst 50a
Can be said to have a function as an activated oxygen releasing agent.

Next, the reducing agent addition device 60 for promoting the exhaust purification action of the exhaust purification catalyst will be explained. The reducing agent addition device 60 includes a reducing agent addition valve 61, a reducing agent supply passage 62, a fuel pressure sensor 63, an emergency shutoff valve 66, and the like, and supplies an appropriate amount of the reducing agent (engine fuel) upstream of the catalytic converter 50 as necessary. Is added to the exhaust passage. That is, the engine fuel as a reducing agent is supplied into the exhaust gas so that the air-fuel ratio of the exhaust gas flowing into the catalytic converter 50 becomes the target air-fuel ratio.

The reducing agent addition valve 61 is an electric on-off valve which is provided at the gathering portion of the exhaust branch pipes 18 and opens when a predetermined voltage is applied. The reducing agent supply passage 62 forms a passage for guiding a part of the fuel pumped up by the fuel pump 6 to the reducing agent addition valve 61. Fuel pressure sensor 63
Detects the fuel pressure in the reducing agent supply passage 62. The emergency cutoff valve 66 stops the fuel supply to the reducing agent supply passage 62 when the pressure in the reducing agent supply passage 62 becomes abnormal.

In the reducing agent addition device 60 thus configured, first, the fuel discharged from the fuel pump 6 is supplied to the reducing agent addition valve 61 through the reducing agent supply passage 62. Subsequently, when a predetermined voltage is applied to the reducing agent addition valve 61, the reducing agent addition valve 61 is opened, and the fuel in the reducing agent supply passage 62 is injected and supplied into the exhaust branch pipe 18 through the reducing agent addition valve 61. . The fuel (reducing agent) supplied to the exhaust branch pipe 18 is
After being stirred in the turbine housing 15b, it flows into the catalytic converter 50 through the exhaust pipe 19. Therefore, the exhaust gas having a low oxygen concentration and mixed with hydrocarbon (HC) which is an unburned combustion component flows into the catalytic converter 50, and the above-described exhaust gas purification action is promoted.

The amount and timing of addition of the reducing agent are the air-fuel ratio sensor (A / F sensor) 47 which is a kind of heater heating type sensor provided downstream of the catalytic converter 50.
Output, and exhaust gas temperature sensors 48a, 48b provided upstream and downstream of the particulate filter 50b.
And the operation history recorded in the electronic control unit 30, which will be described later, and the like.

Next, the EGR device 20 will be described. The EGR device 20 includes an EGR passage 25 and an EGR valve 2
6, oxidation catalyst 28 for EGR device 20, EGR cooler 2
7 and the like, the exhaust gas purification catalyst 50a provided in the exhaust passage 19, in addition to the EGR control for suppressing the generation of nitrogen oxides (NOx) by introducing the exhaust gas which is the EGR gas into the combustion chamber 2.
This is a device used for temperature raising control for raising the temperature of 50b.

The EGR passage 25 is a passage connecting the exhaust branch pipe 18 and the intake branch pipe 8. Further, the EGR valve 26 is
It is an electric on-off valve provided at a connection portion between the EGR passage 25 and the intake branch pipe 8, and the valve opening amount is controlled based on a control program prepared in the electronic control unit 30. Further, the oxidation catalyst 28 for the EGR device is arranged in the path from the exhaust branch pipe 18 to the EGR cooler 27, and the exhaust branch pipe 1
The unburned combustion components in the EGR gas (exhaust gas) flowing from 8 are purified. The EGR cooler 27 uses the engine cooling water as a heat medium to cool the exhaust gas flowing in the EGR passage 25.

The opening control of the EGR valve 26, that is, "EGR control" will be described. When the EGR gas is to be introduced, first, the EGR valve 26 is opened at an opening according to the current operating state, and then the EGR valve 26 is opened. Then, the air amount (fresh air amount) taken into the combustion chamber 2 is calculated from the output of the air flow meter 45, and the difference (error) between the calculated air amount and the target air amount is output from the air-fuel ratio sensor 47 (exhaust gas). The EGR gas is introduced into the combustion chamber 2 at a predetermined rate (EGR rate) by performing feedback control of the EGR valve 26 based on the oxygen concentration of the gas). Here, the target air amount is the specified EGR.
It is the amount of air calculated by the recirculation of gas. That is,
During EGR control, E based on the output of the air-fuel ratio sensor 47
The feedback control of the GR valve 26 is performed, and as a result, the EGR gas flows into the combustion chamber 2 together with the fresh air at a predetermined rate.

By the way, when the exhaust passage 19 is cold, such as during cold, the exhaust gas is cooled, and the water vapor contained in the exhaust gas is condensed into condensed water. Further, when the EGR control is performed in this state, a part of the exhaust gas recirculates to the intake system as described above, so that the flow rate of the exhaust gas flowing in the exhaust passage 19 decreases and is generated by cooling the exhaust gas. The condensed water does not flow downstream of the exhaust gas, but accumulates in, for example, a bent portion of the exhaust passage 19. That is, the "retention of condensed water" occurs due to the execution of the EGR control.

On the other hand, the exhaust passage 19 is provided with an air-fuel ratio sensor 47 used for EGR control, catalyst control (air-fuel ratio control of exhaust gas) and the like. Air-fuel ratio sensor 47
Is a kind of "heater heating type sensor", and a heater is built in the sensor in order to secure the output accuracy of the sensor. When the sensor element is cold, the heater is energized to heat the sensor element and activate the sensor element early to enable the sensor to be used. In other words, to use the sensor when the sensor element is cold,
It can be said that the heating of the sensor element is necessary, and appropriate feedback control is performed by heating the sensor element.

However, as described above, during the EGR control, the condensed water tends to stay due to the EGR control, so that there is a concern that the air-fuel ratio sensor 47 may get wet due to the scattering of the condensed water. That is, there is a concern that the sensor element is cracked due to the condensed water adhering to the sensor element during heating, that is, the occurrence of “thermal shock”. For this reason,
In the situation where the condensed water is likely to stay, the situation in which the sensor element cannot be heated even though the sensor element is desired to be heated continues, which causes a problem that the EGR control or the like using the sensor output cannot be performed.

Therefore, in the internal combustion engine 1 according to the present embodiment, in order to prevent the air-fuel ratio sensor 47 from getting wet due to the scattering of condensed water, the following water-prevention control is carried out and the air-fuel ratio sensor 47 is controlled. Prevents water from getting in. Hereinafter, the water-prevention control according to the present invention will be described with reference to the flowchart shown in FIG.

First, the electronic control unit 30 detects the states of the exhaust passage 19 and the exhaust gas from various sensors (step 101), and detects the accumulation of condensed water in the exhaust passage 19 (step 102).

That is, at step 101, the temperature of the exhaust gas is detected by the exhaust gas temperature sensors 48a and 48b, and the water temperature sensor provided in the outside air temperature sensor (not shown) or the cooling system (not shown) of the internal combustion engine 1 is detected. From this, the wall temperature of the exhaust passage 19 is estimated. Also, in the following step 102,
The residence temperature of the condensed water is detected by comparing the wall surface temperature of the exhaust passage 19 and the temperature of the exhaust gas estimated in step 101 with the saturated steam curve calculated in various preliminary experiments.

Subsequently, in step S102, the electronic control unit 30 proceeds to the next step in order to prevent the air-fuel ratio sensor 47 from being covered with water when it is assumed that the condensed water is retained. In addition, when a negative determination is made in step 102, it is determined that the air-fuel ratio sensor 47 is not flooded, and this control is ended. Further, in the present embodiment, the condensed water detecting means according to the present invention is used in the control program used in the processing of step 101 and step 102, the sensors and the electronic control unit 30 required for processing the control program. Is configured.

Subsequently, the electronic control unit 30 grasps the operating condition of the internal combustion engine from the output changes of various sensors (step 103), and judges based on the grasped operating condition whether or not condensed water is scattered. Yes (Step 10
4).

Note that FIG. 4 is an example of a scattering determination map prepared for grasping the scattering of condensed water. Explaining with reference to the scattering determination map shown in FIG. The presence or absence of scattering is determined. It should be noted that the scattering determination method is, of course, not limited to the following description.

First, the scattering determination map shown in FIG. 4 will be described. The vertical axis represents the amount of condensed water scattered, and the horizontal axis represents the flow rate change amount of exhaust gas per unit time, that is, the flow velocity change amount of exhaust gas. Further, a scattering determination curve which is a threshold for scattering determination is set on the map. In the following description, the magnitude of the exhaust gas flow rate is proportional to the magnitude of the “exhaust gas flow velocity” in the present invention. That is, in the embodiment, since the pipe diameter of the exhaust passage 19 is constant, the flow velocity of the exhaust gas increases as the flow amount of the exhaust gas increases, so the flow velocity of the exhaust gas can be obtained from the flow amount of the exhaust gas.

Next, the scattering determination method will be described with reference to FIG. 4. In step 103, the amount of increase in the accelerator opening,
Estimate the exhaust gas flow rate (velocity) that changes per unit time from the increase in intake air volume and engine speed, and compare the estimated flow rate change with the dispersion determination map to determine the presence or absence of dispersion. To do.

That is, as shown at point a in FIG.
When the flow rate change amount (flow rate change amount) of the exhaust gas is small, the condensed water does not scatter, and the condensed water accumulated in the exhaust passage 19 flows downstream of the exhaust passage 19 through the wall surface of the exhaust passage 19. Further, in the situation shown by point b in FIG. 4, the flow rate change amount of the exhaust gas (flow rate change amount) is large, and it is assumed that the condensed water is scattered. That is, the condensed water accumulated in the exhaust passage 19 is
The air-fuel ratio sensor 4 is scattered by the rapid increase in the flow rate of exhaust gas.
7 will be attached. Further, in the present embodiment, the operation status detecting means is configured by the processing of step 103,
The scattering determination means is configured in step 104.

Next, in the electronic control unit 30, in the situation where the condensed water is supposed to be scattered, the fuel injection of the internal combustion engine is suppressed so as to prevent the rapid increase of the flow rate (flow velocity) of the exhaust gas in order to prevent the condensed water from being scattered. Change control (step 10)
5). That is, if it is assumed that the condensed water is scattered in step 104, the process proceeds to step 105. If a negative determination is made in step 104, step 1
Returning to 01, the dispersion of condensed water is continuously monitored.

In the change of the fuel injection control processed in step 105, for example, the fuel injection control of the internal combustion engine is changed according to the following control contents. First, on the basis of the operating condition grasped in step 103, for example, when a rapid increase in the exhaust gas flow rate due to the acceleration operation of the internal combustion engine is assumed, in the present water prevention control, the increase correction of the fuel injection amount accompanying the acceleration operation is performed. In, the fuel injection amount is increased while the gradual change control is added.

That is, as shown in FIG. 5, in the increase correction of the fuel injection amount with respect to the accelerator operation, the correction width (correction gain) in the initial stage of the increase correction is reduced, and in the initial stage of the increase correction, compared with the original injection amount. Fuel injection with a small injection amount. That is, in the initial stage of the increase correction, the fuel injection amount decreases with respect to the original injection amount, so the increase rate of the engine speed becomes small, and as a result, the exhaust gas flow rate per unit time increases rapidly, that is, the exhaust gas flow velocity increases rapidly. Suppressed. Therefore, the condensed water flows to the downstream side of the exhaust along the wall surface of the exhaust passage 19 even during the acceleration operation, so that the air-fuel ratio sensor 47 (sensor element) is prevented from being flooded with the scattered condensed water. Further, in the present embodiment, step 105 constitutes the fuel injection control means.

After the above-described processing of step 105, the process returns to step 101 again to continuously monitor the retention of condensed water. Then, upon receipt of the condensed water in step 102, this processing routine ends.

As described above, in the internal combustion engine according to the present embodiment, when the condensed water is assumed to be scattered, the water splash prevention control is performed to suppress the rapid increase of the flow velocity of the exhaust gas and prevent the condensed water from scattering. Therefore, it is possible to prevent the air-fuel ratio sensor 47 from getting wet due to the scattering of the condensed water. Therefore, even in the situation where condensed water is generated, the air-fuel ratio sensor 47 can be heated by the heater, and thus feedback control based on the output of the air-fuel ratio sensor 47 becomes possible.

That is, the air-fuel ratio sensor 47 (heater heating type sensor) can be heated even in a situation where the wall surface temperature of the exhaust passage 19 is low and the condensed water is expected to stay, as in the temperature raising control described above. As a result, the air-fuel ratio sensor 47
It is possible to perform an appropriate EGR control by using the output of.

Further, in the above-described water-prevention control, in order to prevent the condensation water from scattering, the fuel injection control of the internal combustion engine is changed to suppress a rapid increase in the flow rate of exhaust gas. Although the response characteristics (driver viability) of the engine are slightly lowered, the required engine output can be sufficiently secured.

That is, as means for suppressing the rapid increase in the flow rate of exhaust gas, for example, closing control of the exhaust throttle valve provided in the exhaust passage, etc. can be considered. In this case, pressure loss occurs in the exhaust system. However, a problem occurs that the required engine output cannot be satisfied. In this respect, in the present water-prevention control, the fuel injection amount is changed to suppress a rapid increase in the flow velocity of exhaust gas, so that the required engine output can be secured as described above. Further, in the present water prevention control, it is possible to reduce the frequency of correction of the fuel injection control accompanying the prevention of water exposure, as compared with the control content that uniformly reduces the flow velocity in the entire operation region. Therefore, in the entire operating range, the reduction of the driver's ability due to the correction of the fuel injection control is suppressed to the necessary minimum.

The above-described embodiment is merely an embodiment of the present invention, and its details can be appropriately changed without departing from the scope of the claims. For example, in the above-mentioned change of the fuel injection amount, the fuel injection amount is increased while adding the gradual change control in the increase correction of the fuel injection, but the maximum fuel injection amount used for the fuel injection control is set up to now. It is also possible to suppress the increase in the exhaust gas flow rate by changing the injection amount to a smaller value than the setting of.

That is, if the setting of the maximum fuel injection amount is changed to a low value in accordance with the generation of condensed water, it takes a long time to reach the target engine speed, and as a result, the flow velocity of exhaust gas decreases. . Therefore, the condensate is prevented from scattering and the air-fuel ratio sensor is prevented from getting wet.

Further, in the above-mentioned processing routine, in addition to the generation of condensed water, it is judged whether or not the condensed water is scattered to prevent the condensed water from scattering. If only this is taken into consideration, the fuel injection control may be changed so as to suppress a rapid increase in the flow velocity of the exhaust gas in a situation where condensed water is expected to be generated regardless of whether or not the condensed water is scattered.

More specifically, the start of the internal combustion engine is regarded as a condition for generating condensed water, and thereafter, the fuel injection control is carried out so as to reduce the flow rate of exhaust gas for a predetermined time. It can be changed.

Further, although the air-fuel ratio sensor has been described as an example in the present embodiment, the same effect as described above can be obtained if it is a heater heating type sensor such as a NOx sensor, an oxygen concentration sensor and an HC sensor. That is, the control device of the present invention can be applied to other than preventing the air-fuel ratio sensor from getting wet.

In the above description, the diesel engine is taken as an example, but the scope of application of the present invention is not limited to the diesel engine, and is applicable to all internal combustion engines in which condensed water is assumed to be generated in the exhaust passage. It is widely applicable.

[0079]

As described above, according to the present invention, it is possible to prevent the heater heating type sensor from being covered with water due to the scattering of condensed water and to use the sensor even in the situation where condensed water is generated. Can provide control technology.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an internal combustion engine according to the present embodiment.

FIG. 2 is a diagram for explaining the internal structure of a particulate filter which is a type of exhaust purification catalyst.

FIG. 3 is a flowchart for explaining a processing routine for water exposure prevention control according to the present embodiment.

FIG. 4 is a diagram showing an example of a scattering determination map used in the water exposure prevention control.

FIG. 5 is a diagram for explaining an injection amount change state of the fuel injection control of the internal combustion engine corrected by the water prevention control.

[Explanation of symbols]

1 Internal combustion engine (diesel engine) 1a crankshaft 2 cylinders (combustion chamber) 3 Fuel injection valve 4 common rail 5 Fuel supply pipe 6 Fuel pump 8 intake branch pipe 9 Intake pipe 10 air cleaner box 12 Intake air temperature sensor 13 Intake throttle valve 14 Actuator 15 Turbocharger 15a Compressor housing 15b turbine housing 16 Intercooler 18 Exhaust branch pipe 18a exhaust port 19 Exhaust passage (exhaust pipe) 20 EGR device 25 EGR passage 26 EGR valve 27 EGR cooler 28 Oxidation catalyst for EGR device 30 electronic control unit 31 bidirectional bus 35 input ports 36 output ports 37 A / D converter 38 Drive circuit 40 accelerator pedal 41 Load sensor 42 crank angle sensor 44a Intake air temperature sensor 44b Intake air temperature sensor 45 Air flow meter 46 Intake pressure sensor 47 Air-fuel ratio sensor 48a Exhaust gas temperature sensor 48b Exhaust gas temperature sensor 52 catalytic converter 50a Storage reduction type NOx catalyst 50b particulate filter 51 casing 55 Exhaust gas inflow passage 55a stopper 56 Exhaust gas outflow passage 56a stopper 57 partitions 58 Filter 59 Oxidation catalytic converter 60 Reductant addition device 61 Reductant addition valve 62 Reductant supply path 63 Fuel pressure sensor 66 Emergency shutoff valve

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ekinori Moriya             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Satoshi Nakamura             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute F-term (reference) 3G084 AA01 BA08 BA13 BA20 BA24                       CA02 DA00 DA12 DA19 DA28                       DA30 EA11 EB06 EB08 FA02                       FA07 FA10 FA11 FA20 FA26                       FA27 FA28 FA29 FA38                 3G301 HA02 HA11 HA13 JA00 JA13                       JA16 JA21 JB01 KA02 LB01                       LB11 MA01 MA15 MA27 NA07                       NC02 ND42 NE08 NE20 PA01Z                       PA07Z PA10Z PA11Z PB08Z                       PD02Z PD11Z PD13Z PE03Z                       PE08Z

Claims (4)

[Claims] 1. An exhaust passage structure in which water vapor contained in exhaust gas is condensed in an exhaust passage of an internal combustion engine, and condensed water generated due to the condensation forms a retention portion of the condensed water in the exhaust passage. And an internal combustion engine having a heater heating type sensor at a position where it is easily exposed to water due to splashing of condensed water that has accumulated in the accumulation part, and condensed water detection means for detecting condensed water generated in the accumulation part. When the condensed water is detected by the condensed water detecting means, the fuel for controlling the fuel injection of the internal combustion engine is changed so as to suppress the rapid increase in the flow velocity of the exhaust gas, and the fuel for preventing the condensed water from being scattered to the heater heating type sensor. An internal combustion engine comprising: an injection control unit; 2. The fuel injection control means increases the fuel injection amount while adding a gradual change control in the increase correction of the fuel injection amount of the internal combustion engine to suppress a rapid increase in the flow velocity of the exhaust gas. Item 1. The internal combustion engine according to item 1. 3. The fuel injection control means changes a setting of a maximum fuel injection amount used for fuel injection control of an internal combustion engine to an injection amount smaller than the setting so far, and suppresses a rapid increase in exhaust gas flow velocity. The internal combustion engine according to claim 1 or 2, characterized in that. 4. An operating condition detecting means for detecting an operating condition of the internal combustion engine, and a scattering determining means for determining whether or not condensed water is in a scattering condition based on the operating condition detected by the operating condition detecting means. The fuel injection control means changes the fuel injection control of the internal combustion engine when the dispersion determination means determines that the condensed water is scattered, in addition to the retention of the condensed water. 4. The method according to claim 1, wherein a rapid increase in exhaust gas flow velocity is suppressed.
Internal combustion engine according to any one of 1.