JP3558019B2 - Abnormality detection device for reducing agent supply device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for detecting an abnormality of a reducing agent supply device that purifies nitrogen oxides (NOx) contained in exhaust gas by supplying a reducing agent to an exhaust gas purifying catalyst disposed in an exhaust passage of an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, an internal combustion engine mounted on an automobile or the like, particularly an internal combustion engine driven by a mixture in an excess oxygen state (a so-called lean air-fuel ratio mixture) such as a diesel engine or a lean-burn gasoline engine, has a problem that the exhaust gas Various techniques have been proposed to reduce the amount of nitrogen oxides (NOx).
[0003]
As one of such techniques, there is known a technique in which a lean NOx catalyst such as a selective reduction type NOx catalyst or a storage reduction type NOx catalyst is disposed in an exhaust passage of an internal combustion engine.
[0004]
The selective reduction type NOx catalyst is a catalyst that reduces or decomposes nitrogen oxides (NOx) when hydrocarbons (HC) are present in an oxygen-excess atmosphere.
[0005]
When purifying nitrogen oxides (NOx) using such a selective reduction type NOx catalyst, it is necessary to supply an appropriate amount of a reducing agent such as hydrocarbon (HC) to the selective reduction type NOx catalyst. When the engine is operated at a lean air-fuel ratio, the amount of hydrocarbons (HC) in the exhaust gas is extremely small. Therefore, when the internal combustion engine is operated at a lean air-fuel ratio, the amount of nitrogen oxides (NOx) in the exhaust gas is reduced. For purification, it is necessary to separately supply a reducing agent such as hydrocarbon (HC) to the selective reduction type NOx catalyst.
On the other hand, when the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst is a lean air-fuel ratio, the NOx storage reduction catalyst stores nitrogen oxides (NOx) in the exhaust gas and flows into the NOx storage reduction catalyst. When the oxygen concentration of the exhaust gas decreases and a reducing agent is present, the catalyst reduces while releasing the stored nitrogen oxides (NOx).
[0006]
Since the amount of nitrogen oxide (NOx) that can be stored by such a storage-reduction NOx catalyst is limited, when the internal combustion engine is operated at a lean air-fuel ratio for a long period of time, the NOx storage capacity of the storage-reduction NOx catalyst increases. Saturation occurs and nitrogen oxides (NOx) contained in the exhaust gas are released to the atmosphere without being purified. Therefore, when purifying nitrogen oxides (NOx) using the storage reduction type NOx catalyst, the exhaust gas flowing into the storage reduction type NOx catalyst becomes empty before the NOx storage capacity of the storage reduction type NOx catalyst is saturated. It is necessary to lower the oxygen concentration in the exhaust gas and increase the amount of hydrocarbons (HC) contained in the exhaust gas by setting the fuel ratio to a rich air-fuel ratio.
[0007]
As a specific technique for purifying nitrogen oxides (NOx) in exhaust gas using a lean NOx catalyst as described above, for example, “Exhaust Purification System for Internal Combustion Engine” described in JP-A-11-93641 Has been proposed.
[0008]
The exhaust gas purifying apparatus for an internal combustion engine described in Japanese Patent Application Laid-Open No. H11-93641 has an exhaust passage branched into a first exhaust passage and a second exhaust passage in the middle thereof, and a storage reduction provided in the first exhaust passage. A first catalytic converter containing a type NOx catalyst, a second catalytic converter provided in a second exhaust passage and containing a selective reduction type NOx catalyst, and a branch provided between a first exhaust pipe and a second exhaust pipe; A switching valve that shuts off the first exhaust passage when the exhaust gas temperature changes from high to low and shuts off the second exhaust passage when the exhaust gas temperature changes from low to high; Reducing agent supply means for supplying a reducing agent.
[0009]
When the NOx purification rate of the selective reduction NOx catalyst becomes higher than that of the NOx storage reduction catalyst as in the case where the exhaust gas changes from high temperature to low temperature, the exhaust gas purification device of the internal combustion engine generates the second exhaust gas. In addition to controlling the switching valve to flow through the exhaust passage, and controlling the internal combustion engine to perform secondary fuel injection in the expansion stroke or the exhaust stroke, as in the case other than when the exhaust gas changes from high temperature to low temperature When the NOx purification rate of the NOx storage reduction catalyst is higher than that of the NOx selective reduction catalyst, the switching valve is controlled so that exhaust gas flows through the first exhaust passage, and the reducing agent is added to the NOx storage reduction catalyst. By controlling the reducing agent addition means, the selective reduction type NOx catalyst and the storage reduction type NOx catalyst can be selectively used according to their respective characteristics, thereby improving the purification rate of nitrogen oxides (NOx). It is those intoxicated to.
[0010]
In the above-mentioned publication, as a reducing agent supply means, an injection nozzle attached to the first catalytic converter and a pressure accumulating chamber for accumulating the fuel discharged from the fuel pump and distributing it to the fuel injection valve are used. And a reducing agent valve provided in the middle of the reducing agent pipe to adjust the flow rate of the fuel flowing through the reducing agent pipe.
[0011]
[Problems to be solved by the invention]
By the way, in the conventional technique described in the above-mentioned Japanese Patent Application Laid-Open No. 11-93641, it is also important to detect fuel leakage in a mechanism for supplying a reducing agent to a lean NOx catalyst.
[0012]
For example, when fuel leaks from the reducing agent supply mechanism to the exhaust pipe, an excessive amount of fuel is supplied to the lean NOx catalyst, and an excessive amount of fuel is burned in the lean NOx catalyst, or a part of the fuel becomes lean NOx catalyst. It is supposed that the lean NOx catalyst is released into the atmosphere without purification, and as a result, there is a possibility that the lean NOx catalyst may be deteriorated due to overheating, damaged, or deteriorated in exhaust emission.
[0013]
Further, when fuel leaks from the reducing agent supply mechanism to a portion other than the exhaust pipe, it becomes difficult to supply a desired amount of fuel to the lean NOx catalyst, and the purification rate of nitrogen oxide (NOx) in the lean NOx catalyst decreases. Therefore, there is a possibility that the exhaust emission may deteriorate.
[0014]
The present invention has been made in view of the various circumstances described above, and detects leakage of a reducing agent in a reducing agent supply device that supplies a reducing agent to a lean NOx catalyst provided in an exhaust passage of an internal combustion engine. An object of the present invention is to provide a technique capable of preventing deterioration and breakage of a lean NOx catalyst or deterioration of exhaust emission caused by leakage of a reducing agent.
[0015]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems.
[0016]
That is, the abnormality detecting device of the reducing agent supply device according to the present invention is
An exhaust purification catalyst that is provided in an exhaust passage of the internal combustion engine and purifies harmful gas components in exhaust gas in the presence of a reducing agent;
A reducing agent supply mechanism for supplying a reducing agent to an exhaust passage upstream of the exhaust purification catalyst;
Pressure detecting means for detecting the pressure of the reducing agent in the reducing agent supply mechanism,
Abnormality determining means for determining an abnormality of the reducing agent supply mechanism based on the pressure detected by the pressure detecting means,
It is characterized by having.
[0017]
In the abnormality detecting device for the reducing agent supply device configured as described above, when supplying the reducing agent to the exhaust purification catalyst, the reducing agent supply mechanism supplies the reducing agent to the exhaust passage upstream of the exhaust purification catalyst.
[0018]
The reducing agent supplied to the exhaust passage flows into the exhaust purification catalyst together with the exhaust gas flowing from the upstream of the exhaust passage. As a result, the exhaust purification catalyst reduces and purifies the harmful gas components in the exhaust using the reducing agent.
[0019]
On the other hand, the pressure detecting means detects the pressure of the reducing agent in the reducing agent supply mechanism. At this time, when the reducing agent is leaking in the reducing agent supply mechanism, the pressure detected by the pressure detecting means has a value different from the pressure when the reducing agent is not leaking in the reducing agent supply mechanism.
[0020]
Therefore, the abnormality determining means can determine the abnormality of the reducing agent supply mechanism based on the pressure detected by the pressure detecting means.
[0021]
Incidentally, even when the leakage of the reducing agent does not occur in the reducing agent supply mechanism, the pressure changes depending on the temperature of the reducing agent and the like. When the pressure is out of the predetermined range, more specifically, when the pressure detected by the pressure detecting means falls below a predetermined lower limit, the reducing agent supply mechanism may be determined to be abnormal.
[0022]
Further, the reducing agent supply mechanism according to the present invention,
A reducing agent discharging unit that discharges the reducing agent at a predetermined pressure,
A reducing agent addition unit provided in an exhaust passage upstream of the exhaust purification catalyst and adding a reducing agent to exhaust gas flowing through the exhaust passage;
A reducing agent supply path for guiding the reducing agent discharged from the reducing agent discharging unit to the reducing agent adding unit,
May be provided.
[0023]
Further, in the abnormality detecting device for the reducing agent supply device according to the present invention, the reducing agent supply mechanism includes:
A reducing agent discharging unit that discharges the reducing agent at a predetermined pressure,
A reducing agent adding unit that is provided in an exhaust passage upstream of the exhaust purification catalyst and adds a reducing agent to exhaust gas flowing through the exhaust passage;
A reducing agent supply passage that guides the reducing agent discharged from the reducing agent discharge unit to the reducing agent addition unit,
A blocking unit configured to block a flow of the reducing agent from the reducing agent discharge unit to the reducing agent supply path;
With
The reducing agent pressure detecting means detects a pressure in the reducing agent supply passage downstream of the blocking unit,
The abnormality determination unit determines an abnormality of the reducing agent supply mechanism based on a change in pressure detected by the pressure detecting unit when the blocking unit interrupts the flow of the reducing agent in the reducing agent supply path. It may be.
[0024]
In this case, when the path from the shutoff section to the reducing agent addition section in the reducing agent supply mechanism is closed, in other words, when a closed space is formed in the reducing agent supply mechanism, An abnormality in the reducing agent supply mechanism is determined based on the pressure in the closed space.
[0025]
For example, when the reducing agent is leaking from the closed space to the outside, the pressure in the closed space is reduced, and when the reducing agent is leaking from the outside of the closed space into the closed space, that is, When the leakage of the reducing agent occurs in the shutoff portion, the pressure in the closed space increases.
[0026]
Therefore, the abnormality determining means can determine the leakage of the reducing agent in the reducing agent supply mechanism based on the decrease or increase in the pressure of the closed space.
[0027]
However, since the pressure of the reducing agent changes due to factors such as temperature, the abnormality determining means determines that the reducing agent supply mechanism is abnormal when the amount of change in the pressure of the closed space exceeds a predetermined amount. You may.
[0028]
Further, when the operation of the internal combustion engine is stopped, the shut-off section cuts off the flow of the reducing agent from the reducing agent discharge section to the reducing agent supply path to form a closed space, and the pressure detection means operates the internal combustion engine to operate. The pressure of the closed space is detected when the internal combustion engine is restarted, and the pressure of the closed space is detected again when the internal combustion engine is restarted. The change amount may be obtained, and if the pressure change amount exceeds a predetermined amount, it may be determined that the reducing agent supply mechanism is abnormal.
[0029]
In this case, since the leakage of the reducing agent is determined based on the pressure change in the closed space for a relatively long period from the time when the operation of the internal combustion engine is stopped to the time when the internal combustion engine is restarted, the leakage of the reducing agent is also detected. It will be easier.
[0030]
In the present invention, examples of the internal combustion engine include a lean-burn internal combustion engine such as a direct-injection lean-burn gasoline engine and a diesel engine.
[0031]
In the present invention, examples of the exhaust purification catalyst include a storage reduction type NOx catalyst and a selective reduction type NOx catalyst.
[0032]
In the present invention, examples of the reducing agent include those containing hydrocarbons (HC) such as light oil and gasoline.
[0033]
In the present invention, a fuel pump that uses a rotational torque of an output shaft (crankshaft) of an internal combustion engine as a drive source can be exemplified as the reducing agent discharge unit of the reducing agent supply mechanism.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the abnormality detection device for a reducing agent supply device according to the present invention will be described with reference to the drawings. Here, an example in which the abnormality detection device for a reducing agent supply device according to the present invention is applied to a diesel engine for driving a vehicle will be described.
[0035]
<Embodiment 1>
First, a first embodiment of an abnormality detection device for a reducing agent supply device according to the present invention will be described with reference to FIGS.
[0036]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an abnormality detection device for a reducing agent supply device according to the present invention is applied and an intake and exhaust system thereof.
[0037]
The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2.
[0038]
The internal combustion engine 1 includes a fuel injection valve 3 for directly injecting fuel into a combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure. The common rail 4 is provided with a common rail pressure sensor 4a that outputs an electric signal corresponding to the pressure of the fuel in the common rail 4.
[0039]
The common rail 4 communicates with a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source. The pump pulley 6 attached to the input shaft of the fuel pump 6 has an output shaft ( It is connected via a belt 7 to a crank pulley 1a attached to a crankshaft).
[0040]
In the fuel injection system configured as described above, when the rotation torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 rotates the rotation torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to.
[0041]
The fuel discharged from the fuel pump 6 is supplied to a common rail 4 via a fuel supply pipe 5, accumulated in the common rail 4 to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0042]
Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
[0043]
The intake branch pipe 8 is connected to an intake pipe 9, and the intake pipe 9 is connected to an air cleaner box 10. An air flow meter 11 that outputs an electric signal corresponding to a mass of the intake air flowing through the intake pipe 9 and an electric current corresponding to the temperature of the intake air flowing through the intake pipe 9 are provided at an intake pipe 9 downstream of the air cleaner box 10. An intake air temperature sensor 12 for outputting a signal is attached.
[0044]
An intake throttle valve 13 that adjusts a flow rate of intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 13 is provided with an intake throttle actuator 14 that is configured by a stepper motor or the like and that drives the intake throttle valve 13 to open and close.
[0045]
An intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 which operates using heat energy of exhaust gas as a driving source. The intake pipe 9 downstream of the housing 15a is provided with an intercooler 16 for cooling intake air that has been compressed and has become high temperature in the compressor housing 15a.
[0046]
In the intake system configured as described above, the intake air that has flowed into the air cleaner box 10 is subjected to a compressor housing via an intake pipe 9 after dust or the like in the intake is removed by an air cleaner (not shown) in the air cleaner box 10. 15a.
[0047]
The intake air flowing into the compressor housing 15a is compressed by rotation of a compressor wheel provided inside the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has become high temperature is cooled by the intercooler 16, and then flows into the intake branch pipe 8 with the flow rate adjusted by the intake throttle valve 13 as necessary. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.
[0048]
On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown).
[0049]
The exhaust branch pipe 18 is connected to a turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected downstream to a muffler (not shown).
[0050]
An exhaust gas purifying catalyst 20 for purifying harmful gas components in exhaust gas is disposed in the exhaust pipe 19. An exhaust pipe 19 downstream of the exhaust purification catalyst 20 has an air-fuel ratio sensor 23 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust pipe 19, and a sensor that responds to the temperature of the exhaust flowing through the exhaust pipe 19. And an exhaust gas temperature sensor 24 for outputting an electric signal.
[0051]
The exhaust pipe 19 downstream of the air-fuel ratio sensor 23 and the exhaust temperature sensor 24 is provided with an exhaust throttle valve 21 for adjusting the flow rate of exhaust flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 which is constituted by a stepper motor or the like and drives the exhaust throttle valve 21 to open and close.
[0052]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) burned in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port, and then centrifugally filtered from the exhaust branch pipe 18. It flows into the turbine housing 15b of the feeder 15. The exhaust gas that has flowed into the turbine housing 15b rotates a turbine wheel rotatably supported in the turbine housing 15b by using thermal energy of the exhaust gas. At this time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.
[0053]
The exhaust gas discharged from the turbine housing 15b flows into the exhaust gas purification catalyst 20 via the exhaust pipe 19, and the harmful gas components in the exhaust gas are removed or purified. The exhaust gas from which the harmful gas components have been removed or purified by the exhaust purification catalyst 20 is discharged into the atmosphere via a muffler after the flow rate is adjusted by an exhaust throttle valve 21 as necessary.
[0054]
Further, the exhaust branch pipe 18 and the intake branch pipe 8 are communicated via an exhaust recirculation passage (EGR passage) 25 for recirculating a part of the exhaust flowing in the exhaust branch pipe 18 to the intake branch pipe 8. . In the middle of the EGR passage 25, a flow regulating valve (EGR) which is constituted by an electromagnetic valve or the like and changes the flow rate of exhaust gas (hereinafter referred to as EGR gas) flowing in the EGR passage 25 according to the magnitude of the applied power (Valve) 26 is provided.
[0055]
An EGR cooler 27 that cools EGR gas flowing through the EGR passage 25 is provided at a position upstream of the EGR valve 26 in the EGR passage 25.
[0056]
In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 becomes conductive, and a part of the exhaust gas flowing in the exhaust branch pipe 18 flows into the EGR passage 25, It is guided to the intake branch pipe 8 via the EGR cooler 27.
[0057]
At that time, in the EGR cooler 27, heat exchange is performed between the EGR gas flowing in the EGR passage 25 and a predetermined refrigerant, and the EGR gas is cooled.
[0058]
The EGR gas recirculated from the exhaust branch pipe 18 to the intake branch pipe 8 through the EGR passage 25 is guided to the combustion chamber of each cylinder 2 while mixing with fresh air flowing from the upstream of the intake branch pipe 8, The fuel is burned using the fuel injected from the injection valve 3 as an ignition source.
[0059]
Here, the EGR gas includes water (H₂O) and carbon dioxide (CO₂), Etc., because it does not burn itself and contains an endothermic inert gas component, when the EGR gas is contained in the mixture, the combustion temperature of the mixture decreases. Thus, the amount of generated nitrogen oxides (NOx) is suppressed.
[0060]
Further, when the EGR gas is cooled in the EGR cooler 27, the temperature of the EGR gas itself decreases and the volume of the EGR gas decreases, so that when the EGR gas is supplied into the combustion chamber, the atmospheric temperature in the combustion chamber is reduced. Does not rise unnecessarily, and the amount of fresh air supplied to the combustion chamber (volume of fresh air) does not unnecessarily decrease.
[0061]
Next, the exhaust purification catalyst 20 according to the present embodiment will be specifically described.
[0062]
The exhaust purification catalyst 20 is a NOx catalyst that purifies nitrogen oxides (NOx) in exhaust gas in the presence of a reducing agent. Examples of such a NOx catalyst include a selective reduction type NOx catalyst and a storage reduction type NOx catalyst. Here, the storage reduction type NOx catalyst will be described as an example. Hereinafter, the exhaust purification catalyst 20 is referred to as a storage reduction type NOx catalyst 20.
[0063]
The storage reduction type NOx catalyst 20 is made of, for example, alumina (Al₂O₃) As a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li) and cesium (Cs) and an alkali such as barium (Ba) and calcium (Ca) on the carrier. At least one selected from earth and rare earths such as lanthanum (La) yttrium (Y) and a noble metal such as platinum (Pt) are supported.
[0064]
When the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst 20 (hereinafter, referred to as an exhaust air-fuel ratio) is a lean air-fuel ratio, the NOx storage reduction catalyst 20 configured as described above is capable of oxidizing nitrogen in the exhaust gas. When the oxygen concentration of the inflowing exhaust gas is reduced and a reducing agent is present, the stored nitrogen oxides (NOx) are reduced and purified while releasing the stored nitrogen oxides (NOx).
[0065]
Here, the exhaust air-fuel ratio means the ratio of the sum of the amount of air supplied to the exhaust passage, the combustion chamber, the intake passage, etc. upstream of the exhaust purification catalyst and the sum of the amount of fuel (hydrocarbon). And Therefore, as long as no fuel, reducing agent, or air is supplied into the exhaust passage upstream of the NOx storage reduction catalyst 20, the exhaust air-fuel ratio matches the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber.
[0066]
Here, the NOx absorption / desorption mechanism of the NOx storage reduction catalyst 20 will be described using an example of a NOx storage reduction catalyst in which platinum (Pt) and barium (Ba) are supported on a carrier made of alumina.
[0067]
It is considered that the NOx absorbing / releasing action of the NOx storage reduction catalyst 20 is performed by a mechanism as shown in FIG.
[0068]
First, when the air-fuel ratio of the exhaust gas flowing into the storage-reduction NOx catalyst 20 becomes a lean air-fuel ratio and the oxygen concentration in the exhaust gas increases, as shown in FIG. , Oxygen in the exhaust (O₂) Is O₂ ⁻Or O^2-And adheres to the surface of platinum (Pt) in the form of, and the nitrogen monoxide (NO) in the exhaust gas becomes O 2 on the surface of platinum (Pt).₂ ⁻Or O^2-Reacts with nitrogen dioxide (NO₂(2NO + O)₂→ 2NO₂). Nitrogen dioxide (NO₂) Is oxidized on the surface of platinum (Pt) and combines with barium oxide (BaO) to form nitrate ions (NO₃ ⁻) Is formed. Thus, the nitrogen oxides (NOx) in the exhaust gas are converted into nitrate ions (NO_3-) Is stored in the NOx storage reduction catalyst.
[0069]
The above-described NOx storage operation is continued as long as the air-fuel ratio of the inflowing exhaust gas is lean and the NOx storage capacity of the storage reduction type NOx catalyst is not saturated.
[0070]
On the other hand, when the oxygen concentration of the inflowing exhaust gas decreases, the NOx storage reduction catalyst 20 reduces the nitrogen dioxide (NO₂) Is reduced, so that the nitrate ion (NO) bound to barium oxide (BaO)_3-) Is conversely nitrogen dioxide (NO₂) Or nitrogen monoxide (NO) and is released from the NOx storage reduction catalyst.
[0071]
That is, when the oxygen concentration of the exhaust gas flowing into the NOx storage reduction catalyst 20 decreases, the nitrate ions (NO_3-) In the form of nitrogen oxide (NOx) stored in the NOx storage reduction catalyst₂) Or nitrogen monoxide (NO) and released from the NOx storage reduction catalyst.
[0072]
As shown in FIG. 2B, the nitrogen oxides (NOx) released from the NOx storage reduction catalyst 20 are reduced components (eg, platinum (Pt) of the NOx storage reduction catalyst 20) contained in the exhaust gas. Oxygen on top_2-Or O^2-Reacts with active species such as partially oxidized hydrocarbons (HC) and carbon monoxide (CO)) to form nitrogen (N₂) Etc.
[0073]
That is, hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas are converted to O 2 on platinum (Pt).₂ ⁻Or O^2-And oxidized by reaction with O 2 on platinum (Pt)₂ ⁻Or O^2-If hydrocarbons (HC) and carbon monoxide (CO) still remain even after the consumption of hydrogen, these hydrocarbons (HC) and carbon monoxide (CO) are released from the NOx storage reduction catalyst 20. It reacts with nitrogen oxides (NOx) and nitrogen oxides (NOx) exhausted from the internal combustion engine 1, and as a result, the nitrogen oxides (NOx)₂).
[0074]
Therefore, by setting the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst 20 to the stoichiometric air-fuel ratio or the rich air-fuel ratio, the nitrogen oxides (NOx) stored in the NOx storage reduction catalyst 20 are released and reduced. It is possible to do.
[0075]
By the way, since the NOx storage capacity of the NOx storage reduction catalyst 20 is limited, when exhaust gas having a lean air-fuel ratio flows into the NOx storage reduction catalyst 20 for a long time, the NOx storage capacity of the NOx storage reduction catalyst 20 is saturated. In addition, nitrogen oxides (NOx) in the exhaust gas are released into the atmosphere without being removed or purified by the NOx storage reduction catalyst 20.
[0076]
However, in a diesel engine such as the internal combustion engine 1, the air-fuel ratio of the lean air-fuel ratio is burned in most of the operating region, and the air-fuel ratio of the exhaust gas becomes the lean air-fuel ratio in most of the operating region. The NOx storage capacity of the reduced NOx catalyst 20 is likely to be saturated.
[0077]
Therefore, when the NOx storage reduction catalyst 20 is applied to a lean burn type internal combustion engine such as a diesel engine, the air-fuel ratio of exhaust gas is theoretically determined at a predetermined timing before the NOx storage capacity of the NOx storage reduction catalyst 20 is saturated. It is necessary to set the air-fuel ratio or the rich air-fuel ratio.
[0078]
On the other hand, the internal combustion engine 1 according to the present embodiment includes a reducing agent supply mechanism that adds fuel (light oil) as a reducing agent to exhaust gas flowing through an exhaust passage upstream of the NOx storage reduction catalyst 20. .
[0079]
As shown in FIG. 1, the reducing agent supply mechanism is mounted on the cylinder head of the internal combustion engine 1 so that its injection hole faces the inside of the exhaust branch pipe 18, and when a fuel having a predetermined valve opening pressure or more is applied. A reducing agent injection valve 28 that opens the valve to inject fuel, a reducing agent supply passage 29 that guides the fuel discharged from the fuel pump 6 to the reducing agent injection valve 28, and a middle portion of the reducing agent supply passage 29. And a flow control valve 30 for adjusting the flow rate of the fuel flowing through the reducing agent supply passage 29, and the fuel in the reducing agent supply passage 29 provided in the reducing agent supply passage 29 upstream of the flow control valve 30. A shutoff valve 31 for shutting off the flow of the reducing agent, a reducing agent pressure sensor 32 attached to the reducing agent supply passage 29 upstream of the flow regulating valve 30 and outputting an electric signal corresponding to the pressure in the reducing agent supply passage 29, It has.
[0080]
In addition, the reducing agent injection valve 28 has an injection hole of the reducing agent injection valve 28 located downstream of a connection portion of the exhaust branch pipe 18 with the EGR passage 25, and is provided at a collecting portion of the four branch pipes in the exhaust branch pipe 18. It is preferable to be attached to the cylinder head so as to project to the exhaust port of the closest cylinder 2 and to face the gathering portion of the exhaust branch pipe 18.
[0081]
This prevents the reducing agent (unburned fuel component) injected from the reducing agent injection valve 28 from flowing into the EGR passage 25, and prevents the reducing agent from remaining in the exhaust branch pipe 18 without causing the centrifugal supercharger to accumulate. In order to reach the turbine housing 15b.
[0082]
In the example shown in FIG. 1, since the first (# 1) cylinder 2 of the four cylinders 2 of the internal combustion engine 1 is located closest to the collecting portion of the exhaust branch pipe 18, the first (# 1) cylinder is used. Although the reducing agent injection valve 28 is attached to the exhaust port of the second cylinder 2, when the cylinder 2 other than the first (# 1) cylinder 2 is located closest to the collecting portion of the exhaust branch pipe 18, The reducing agent injection valve 28 is attached to the exhaust port.
[0083]
Further, the reducing agent injection valve 28 is provided so as to penetrate a water jacket (not shown) formed in the cylinder head or to be attached in close proximity to the water jacket. The reducing agent injection valve 28 uses cooling water flowing through the water jacket. 28 may be cooled.
[0084]
In such a reducing agent supply mechanism, when the flow control valve 30 is opened, the high-pressure fuel discharged from the fuel pump 6 is applied to the reducing agent injection valve 28 via the reducing agent supply path 29. Then, when the pressure of the fuel applied to the reducing agent injection valve 28 reaches or exceeds the valve opening pressure, the reducing agent injection valve 28 opens and fuel as the reducing agent is injected into the exhaust branch pipe 18.
[0085]
The reducing agent injected from the reducing agent injection valve 28 into the exhaust branch pipe 18 flows into the turbine housing 15b together with the exhaust gas flowing from the upstream of the exhaust branch pipe 18. The exhaust gas and the reducing agent that have flowed into the turbine housing 15b are stirred and uniformly mixed by the rotation of the turbine wheel to form an exhaust gas having a rich air-fuel ratio.
[0086]
The rich air-fuel ratio exhaust gas thus formed flows from the turbine housing 15b into the NOx storage reduction catalyst 20 via the exhaust pipe 19, and the nitrogen oxides (NOx) stored in the NOx storage reduction catalyst 20 are stored. ) While releasing nitrogen (N₂).
[0087]
Thereafter, when the flow control valve 30 is closed and the supply of the reducing agent from the fuel pump 6 to the reducing agent injection valve 28 is interrupted, the pressure of the fuel applied to the reducing agent injection valve 28 becomes lower than the valve opening pressure. As a result, the reducing agent injection valve 28 closes, and the addition of the reducing agent into the exhaust branch pipe 18 is stopped.
[0088]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 35 for controlling the internal combustion engine 1. 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.
[0089]
The ECU 35 includes a common rail pressure sensor 4a, an air flow meter 11, an intake temperature sensor 12, an intake pipe pressure sensor 17, an air-fuel ratio sensor 23, an exhaust temperature sensor 24, a reducing agent pressure sensor 32, a crank position sensor 33, a water temperature sensor 34, an accelerator Various sensors such as an opening sensor 36 are connected via electric wiring, and output signals of the various sensors are input to the ECU 35.
[0090]
On the other hand, the ECU 35 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the flow control valve 30, the shut-off valve 31, and the like via electric wiring. Can be controlled.
[0091]
Here, as shown in FIG. 3, the ECU 35 includes a CPU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357 interconnected by a bidirectional bus 350. , An A / D converter (A / D) 355 connected to the input port 356.
[0092]
The input port 356 inputs an output signal of a sensor that outputs a signal in a digital signal format, such as the crank position sensor 33, and transmits those output signals to the CPU 351 and the RAM 353.
[0093]
The input port 356 includes a common rail pressure sensor 4a, an air flow meter 11, an intake temperature sensor 12, an intake pipe pressure sensor 17, an air-fuel ratio sensor 23, an exhaust temperature sensor 24, a reducing agent pressure sensor 32, a water temperature sensor 34, and an accelerator opening sensor. 36, etc., the signals are input via the A / D 355 of the sensor that outputs analog signal format signals, and the output signals are transmitted to the CPU 351 and the RAM 353.
[0094]
The output port 357 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the flow control valve 30, the shutoff valve 31, and the like via electric wiring, and is output from the CPU 351. The control signal is transmitted to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the flow control valve 30, or the shutoff valve 31.
[0095]
The ROM 352 includes a fuel injection valve control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and the EGR valve 26. Leak control for determining the leak of the reducing agent in the reducing agent addition mechanism in addition to various application programs such as an EGR control routine for controlling the pressure control valve, a reducing agent addition control routine for controlling the flow regulating valve 30, and the like. Remembers routines.
[0096]
The ROM 352 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 the operating state of the internal combustion engine 1 and a basic fuel injection amount (basic fuel injection time), and a relation between the operating state of the internal combustion engine 1 and the basic fuel injection timing. A fuel injection timing control map, an intake throttle valve opening control map indicating a relationship between an operating state of the internal combustion engine 1 and a target opening of the intake throttle valve 13, an operating state of the internal combustion engine 1, and a target opening of the exhaust throttle valve 21 , An EGR valve opening control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the EGR valve 26, the operating state of the internal combustion engine 1 and the flow control valve 30 And a flow control valve control map showing the relationship with the valve opening timing.
[0097]
The RAM 353 stores output signals from each sensor, calculation results of the CPU 351 and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data each time the crank position sensor 33 outputs a pulse signal.
[0098]
The backup RAM 354 is a nonvolatile memory that can store data even after the operation of the internal combustion engine 1 is stopped.
[0099]
The CPU 351 operates in accordance with the application program stored in the ROM 352, and performs a fuel injection valve control, an intake throttle control, an exhaust throttle control, an EGR control, a reducing agent addition control, and a reducing agent leakage determination which is the gist of the present invention. Execute control.
[0100]
For example, in the fuel injection valve control, the CPU 351 first determines the amount of fuel injected from the fuel injection valve 3 and then determines the timing at which fuel is injected from the fuel injection valve 3.
[0101]
When determining the fuel injection amount, the CPU 351 reads the engine speed and the output signal (accelerator opening) of the accelerator opening sensor 36 stored in the RAM 353. The CPU 351 accesses the 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. The CPU 351 corrects the basic fuel injection time based on output signal values of the air flow meter 11, the intake air temperature sensor 12, the water temperature sensor 34, and the like, and determines a final fuel injection time.
[0102]
When determining the fuel injection timing, the CPU 351 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 351 corrects the basic fuel injection timing by using output signal values of the air flow meter 11, the intake air temperature sensor 12, the water temperature sensor 34, and the like as parameters, and determines the final fuel injection timing.
[0103]
When the fuel injection time and the fuel injection timing are determined, the CPU 351 compares the fuel injection timing with the output signal of the crank position sensor 33, and the output signal of the crank position sensor 33 matches the fuel injection start timing. At this point, the application of the driving power to the fuel injection valve 3 is started. The CPU 351 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.
[0104]
In the fuel injection control, when the operating state of the internal combustion engine 1 is in the idling operation state, the CPU 351 uses the output signal value of the water temperature sensor 34 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 state of the auxiliary devices operating as a parameter as a parameter. Then, the CPU 351 performs feedback control of the fuel injection amount such that the actual idle speed matches the target idle speed.
[0105]
In the intake throttle control, the CPU 351 reads, for example, the engine speed and the accelerator opening stored in the RAM 353. The CPU 351 accesses the intake throttle valve opening control map and calculates a target intake throttle valve opening corresponding to the engine speed and the accelerator opening. The CPU 351 applies drive power corresponding to the target intake throttle valve opening to the intake throttle actuator 14. At that time, the CPU 351 detects the actual opening degree of the intake throttle valve 13 and feeds back the intake throttle actuator 14 based on the difference between the actual opening degree of the intake throttle valve 13 and the target intake throttle valve opening degree. You may make it control.
[0106]
In the exhaust throttle control, for example, the CPU 351 closes the exhaust throttle valve 21 in the valve closing direction 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. The exhaust throttle actuator 22 is controlled so as to be driven.
[0107]
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.
[0108]
In the EGR control, the CPU 351 reads the engine speed, the output signal (cooling water temperature) of the water temperature sensor 34, the output signal (accelerator opening) of the accelerator opening sensor 36, and the like stored in the RAM 353, and performs the EGR control. It is determined whether or not the execution condition is satisfied.
[0109]
The above-described EGR control execution conditions include, for example, that the coolant temperature is equal to or higher than a predetermined temperature, that the internal combustion engine 1 has been continuously operated for a predetermined time or more from the start, and that the amount of change in the accelerator opening is a positive value. Conditions can be exemplified.
[0110]
When it is determined that the above-described EGR control execution condition is satisfied, the CPU 351 accesses the EGR valve opening control map using the engine speed and the accelerator opening as parameters, and executes the engine speed and the accelerator operation. A target EGR valve opening corresponding to the opening is calculated. The CPU 351 applies drive power corresponding to the target EGR valve opening to the EGR valve 26. On the other hand, when it is determined that the above-described EGR control execution condition is not satisfied, the CPU 351 performs control to maintain the EGR valve 26 in the fully closed state.
[0111]
Further, in the EGR control, the CPU 351 may perform so-called EGR valve feedback control in which the opening degree of the EGR valve 26 is feedback-controlled using the intake air amount of the internal combustion engine 1 as a parameter.
[0112]
In the EGR valve feedback control, for example, the CPU 351 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. .
[0113]
When the target intake air amount is determined by the above-described procedure, the CPU 351 reads the output signal value (actual intake air amount) of the air flow meter 11 stored in the RAM 353, and reads the actual intake air amount, the target intake air amount, and the like. Compare.
[0114]
When the actual intake air amount is smaller than the target intake air amount, the CPU 351 closes the EGR valve 26 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 8 from the EGR passage 25 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.
[0115]
On the other hand, when the actual intake air amount is larger than the target intake air amount, the CPU 351 opens the EGR valve 26 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 8 from the EGR passage 25 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.
[0116]
In addition, in the reducing agent addition control, the CPU 351 first determines whether a reducing agent addition condition is satisfied. As the reducing agent addition conditions, for example, the storage reduction NOx catalyst 20 is in an active state, the output signal value (exhaust temperature) of the exhaust temperature sensor 24 is equal to or lower than a predetermined upper limit, Conditions such as that the temperature increase control, SOx poisoning regeneration control, and the like are not executed to recover SOx poisoning and the like can be exemplified.
[0117]
If the CPU 351 determines that the above-described reducing agent addition condition is satisfied, the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst 20 spikes with a stoichiometric air-fuel ratio or a rich air-fuel ratio in a relatively short cycle. The nitrogen oxides (NOx) stored in the NOx storage reduction catalyst 20 are released and reduced in a short period by controlling the flow control valve 30 so as to obtain the fuel ratio.
[0118]
At this time, the CPU 351 reads the engine speed, the output signal of the accelerator opening sensor 36 (accelerator opening), the output signal value of the air flow meter 11 (intake air amount), the fuel injection amount, and the like, which are stored in the RAM 353. The CPU 351 accesses the flow control valve control map in the ROM 352 using the above-described engine speed, accelerator opening, intake air amount, and fuel injection amount as parameters, and calculates the opening timing of the flow control valve 30. The CPU 351 opens the flow control valve 30 according to the valve opening timing.
[0119]
In this case, the high-pressure fuel discharged from the fuel pump 6 is supplied to the reducing agent injection valve 28 via the reducing agent supply passage 29, and the pressure of the fuel applied to the reducing agent injection valve 28 is equal to or higher than the valve opening pressure. , The reducing agent injection valve 28 opens to inject fuel as a reducing agent into the exhaust branch pipe 18.
[0120]
The reducing agent injected from the reducing agent injection valve 28 into the exhaust branch pipe 18 mixes with the exhaust gas flowing from the upstream of the exhaust branch pipe 18 to form an exhaust gas having a stoichiometric air-fuel ratio or a rich air-fuel ratio. Exhaust gas having a stoichiometric air-fuel ratio or a rich air-fuel ratio flows into the NOx storage reduction catalyst 20.
[0121]
As described above, when the exhaust gas having the stoichiometric air-fuel ratio or the rich air-fuel ratio flows into the NOx storage reduction catalyst 20, the nitrogen oxides (NOx) stored in the NOx storage reduction catalyst 20 are released and the nitrogen (Nx) is released.₂) Etc.
[0122]
Next, the reducing agent leakage determination control which is the gist of the present invention will be described.
[0123]
In the reducing agent addition mechanism, when the flow control valve 30 is opened, a part of the fuel discharged from the fuel pump 6 is supplied to the reducing agent injection valve 28 via the reducing agent supply passage 29, whereby the reducing agent When the pressure of the fuel applied to the injection valve 28 becomes equal to or higher than the valve opening pressure, the reducing agent injection valve 28 opens to inject the fuel as the reducing agent into the exhaust branch pipe 18.
[0124]
When the flow control valve 30 is switched from the open state to the closed state, the supply of fuel from the fuel pump 6 to the reducing agent injection valve 28 is shut off, and the pressure of the fuel applied to the reducing agent injection valve 28 is opened. Since the pressure drops below the pressure, the reducing agent injection valve 28 automatically closes.
[0125]
At this time, since the fuel discharged from the fuel pump 6 is supplied to the reducing agent supply path 29 upstream of the flow control valve 30, fuel leakage occurs in a path from the fuel pump 6 to the flow control valve 30. If not, the pressure in the reducing agent supply passage 29 upstream of the flow control valve 30 (hereinafter, referred to as added fuel pressure) becomes a pressure corresponding to the discharge pressure of the fuel pump 6 (hereinafter, referred to as a pump corresponding pressure).
[0126]
On the other hand, when the fuel leaks from the reducing agent supply passage 29 upstream of the flow adjustment valve 30 to the reducing agent supply passage 29 downstream of the flow adjustment valve 30 due to a valve closing failure of the flow adjustment valve 30 or the like, the fuel pump 6 The added fuel pressure becomes lower than the pressure corresponding to the pump when fuel in the path leaks out of the path due to breakage of the path leading to the flow control valve 30 or the like.
[0127]
Therefore, if the output signal value (addition fuel pressure) of the reducing agent pressure sensor 32 is lower than the pump corresponding pressure, it can be determined that the fuel is leaking in the reducing agent supply mechanism.
[0128]
By the way, since the fuel pump 6 according to the present embodiment uses the rotational torque of the crankshaft as a drive source, the discharge pressure of the fuel pump 6 changes according to the engine speed, and the reducing agent upstream of the flow control valve 30. The pressure corresponding to the pump in the supply passage 29 also changes according to the engine speed as shown in FIG.
[0129]
On the other hand, in the reducing agent leak determination control according to the present embodiment, the CPU 351 inputs the output signal value (addition fuel pressure) of the reducing agent pressure sensor 32 when the flow control valve 30 is in the closed state, and The pump corresponding pressure corresponding to the engine speed at that time is calculated, and the added fuel pressure and the pump corresponding pressure are compared to determine the leakage of the reducing agent.
[0130]
However, since the pressure of the fuel may change due to external factors such as the wall surface temperature of the reducing agent supply passage 29 and the outside air temperature, the CPU 351 determines that the reducing agent is lower than the pump corresponding pressure by a predetermined pressure or more. Is preferably determined to be leaking.
[0131]
The relationship between the engine speed and the pump corresponding pressure may be experimentally determined in advance, and the relationship may be mapped and stored in the ROM 352.
[0132]
Hereinafter, the reducing agent leakage determination control according to the present embodiment will be described with reference to the flowchart of FIG.
[0133]
The flowchart shown in FIG. 5 is a flowchart showing a reducing agent leakage determination control routine. The reducing agent leakage determination control routine is executed by the CPU 351 at predetermined time intervals (for example, every time the crank position sensor 33 outputs a predetermined number of pulse signals). ) Is a routine that is repeatedly executed.
[0134]
In the reducing agent leak determination control routine, the CPU 351 first determines in S501
It is determined whether "1" is not stored in the reducing agent leakage flag storage area set in the RAM 353.
[0135]
The reducing agent leakage flag storage area is set to “1” when it is determined by the reducing agent addition mechanism that the reducing agent (fuel) has leaked, and is set to “0” when it is determined that the reducing agent has not leaked. Is a storage area to be reset.
[0136]
If it is determined in step S501 that “1” is not stored in the reducing agent leakage flag storage area, in other words, if it is determined that “0” is stored in the reducing agent leakage flag storage area, The CPU 351 proceeds to S502, and determines whether “1” is not stored in the reducing agent addition execution flag storage area set in the RAM 353.
[0137]
In the reducing agent addition execution flag storage area, “1” is set when addition of the reducing agent is performed in a separate reducing agent addition control routine, and “0” is set when the execution of the reducing agent addition is stopped. This is the storage area to be reset.
[0138]
When it is determined in step S502 that “1” is stored in the reducing agent addition execution flag storage area, the CPU 351 determines that the flow rate adjustment valve 30 is not in the closed state, and once ends the execution of this routine. I do.
[0139]
On the other hand, if it is determined in step S502 that “1” is not stored in the reducing agent addition execution flag storage area, that is, “0” is stored in the reducing agent addition execution flag storage area, the CPU 351 determines Then, the flow control valve 30 is considered to be in the closed state, and the process proceeds to S503.
[0140]
In S503, the CPU 351 accesses the RAM 353 and reads the latest engine speed and the output signal value (addition fuel pressure) of the reducing agent pressure sensor 32.
[0141]
In S504, the CPU 351 accesses a map indicating the relationship between the engine speed and the pump corresponding pressure, and calculates the pump corresponding pressure corresponding to the engine speed read in S503.
[0142]
In S505, the CPU 351 determines whether or not the differential pressure obtained by subtracting the added fuel pressure read in S503 from the pump corresponding pressure calculated in S504 is higher than a predetermined pressure.
[0143]
If it is determined in step S505 that the differential pressure obtained by subtracting the added fuel pressure from the pump corresponding pressure is equal to or less than a predetermined pressure, the CPU 351 determines that the leakage of fuel has not occurred in the reducing agent addition mechanism. The process proceeds to S508, where "0" is reset to the reducing agent leakage flag storage area of the RAM 353, and the execution of this routine ends.
[0144]
On the other hand, when it is determined in S505 that the differential pressure obtained by subtracting the additional fuel pressure from the pump corresponding pressure is higher than a predetermined pressure, the CPU 351 determines that fuel leakage has occurred in the reducing agent addition mechanism. It proceeds to S506.
[0145]
In S506, the CPU 351 sets “1” in the reducing agent leakage flag storage area of the RAM 353.
[0146]
In S507, the CPU 351 turns on a warning lamp (not shown) provided in the vehicle interior, and ends the execution of this routine. The CPU 351 may turn on the warning lamp and close the shutoff valve 31 to prohibit the addition of the reducing agent.
[0147]
In this way, when the CPU 351 executes the reducing agent leak determination control routine as described above, the abnormality determining means according to the present invention is realized.
[0148]
According to the above-described embodiment, since it is possible to detect the leakage of the reducing agent in the reducing agent addition mechanism based on the fuel pressure in the reducing agent supply passage 29, the leakage of the reducing agent is controlled by the reducing agent addition control. By reflecting this, it is possible to suppress the excessive supply or insufficient addition of the reducing agent to the NOx storage reduction catalyst 20, and it is possible to minimize the deterioration of the exhaust emission.
[0149]
Further, according to the present embodiment, when the leakage of the reducing agent in the reducing agent adding mechanism is detected, the shutoff valve 31 is closed to prohibit the addition of the reducing agent. It is also possible to prevent the leakage of the reducing agent and the careless addition of the reducing agent to the exhaust branch pipe 18 from the reducing agent supply mechanism. Thereby, it is also possible to prevent overheating of the NOx storage reduction catalyst 20 due to excessive addition of the reducing agent to the NOx storage reduction catalyst 20.
[0150]
<Embodiment 2>
Next, a second embodiment of the abnormality detecting device for the reducing agent supply 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.
[0151]
In the reducing agent leakage determination control according to the first embodiment described above, the leakage of the reducing agent is determined based on the added fuel pressure when the flow control valve 30 is in the closed state and the shut-off valve 31 is in the open state. Therefore, when a relatively large amount of the reducing agent leaks, it is easy to detect the leaking of the reducing agent. However, when a small amount of the reducing agent leaks, the amount of the leak is reduced by the discharge amount of the fuel pump 6. May be exceeded, and it may be difficult to detect a small amount of leakage of the reducing agent.
[0152]
On the other hand, in the present embodiment, the CPU 351 determines the leakage of the reducing agent based on the change in the added fuel pressure when the flow control valve 30 is in the closed state and the shut-off valve 31 is in the closed state. I made it.
[0153]
When both the flow control valve 30 and the shutoff valve 31 are in the closed state, the reducing agent supply passage 29 between the flow control valve 30 and the shutoff valve 31 becomes a closed space, and a pressure corresponding to the pump is applied to the closed space. Fuel will be trapped.
[0154]
At this time, leakage of the reducing agent from the reducing agent supply passage 29 upstream of the flow regulating valve 30 to the reducing agent supply passage 29 downstream of the flow regulating valve 30 due to a valve closing failure of the flow regulating valve 30 or the like, and shutoff due to a poor closing of the shutoff valve 31 or the like. Reduction of the reductant from the reductant supply passage 29 upstream of the valve 31 to the reductant supply passage 29 downstream of the valve 31, or the breakage of the passage from the shut-off valve 31 to the flow regulating valve 30, for example, from the inside of the passage to the outside of the passage. If the leakage of the agent occurs, the added fuel pressure in the closed space decreases or increases.
[0155]
If the leakage of the reducing agent in the closed space is relatively small, the added fuel pressure in the closed space will gradually change, but by detecting the change in the added fuel pressure after a certain period, a relatively small amount Of the reducing agent can be easily detected.
[0156]
Therefore, in the reducing agent leakage determination control according to the present embodiment, the CPU 351 closes the shutoff valve 31 for a predetermined period when the flow control valve 30 is in a closed state, and detects a change in the added fuel pressure during the predetermined period. If the amount of change in the added fuel pressure is equal to or more than a predetermined amount, it is determined that the reducing agent has leaked to the reducing agent supply mechanism.
[0157]
Hereinafter, the reducing agent leakage determination control according to the present embodiment will be described with reference to the flowchart of FIG.
[0158]
The flowchart shown in FIG. 6 is a flowchart showing a reducing agent leakage determination control routine. The reducing agent leakage determination control routine is executed by the CPU 351 at predetermined time intervals (for example, every time the crank position sensor 33 outputs a predetermined number of pulse signals). ) Is a routine that is repeatedly executed.
[0159]
In the reducing agent leakage determination control routine, the CPU 351 first accesses the reducing agent leakage flag storage area of the RAM 353 in S601, and determines whether or not “1” is stored in the reducing agent leakage flag storage area.
[0160]
If it is determined in step S601 that "1" has already been stored in the reducing agent leakage flag storage area, the CPU 351 proceeds to step S610, turns on a warning lamp provided in the vehicle interior, and returns to the driver of the vehicle. Encourages repair of the agent supply mechanism.
[0161]
On the other hand, if it is determined in step S601 that “1” is not stored in the reducing agent leakage flag storage area, the CPU 351 proceeds to step S602, where “1” is stored in the reducing agent addition execution flag storage area set in the RAM 353. "Is not stored.
[0162]
If it is determined in step S602 that “1” is stored in the reducing agent addition execution flag storage area, the CPU 351 determines that the flow rate adjustment valve 30 is not in the closed state, and once ends the execution of this routine. I do.
[0163]
On the other hand, if it is determined in step S602 that “1” is not stored in the reducing agent addition execution flag storage area, that is, “0” is stored in the reducing agent addition execution flag storage area, the CPU 351 determines Then, the flow control valve 30 is considered to be in the closed state, and the process proceeds to S603.
[0164]
In S603, the CPU 351 closes the shutoff valve 31, and sets the reducing agent supply passage 29 from the shutoff valve 31 to the flow control valve 30 as a closed space.
[0165]
In S604, the CPU 351 inputs the output signal value of the reducing agent pressure sensor 32 (additional fuel pressure in the closed space): P1, and stores the additional fuel pressure: P1 in the RAM 353.
[0166]
In S605, the CPU 351 accesses the counter storage area set in a predetermined area of the RAM 353, and increments the counter value: C stored in the counter storage area by one. The counter storage area is an area for storing an elapsed time from a point in time when the additional fuel pressure: P1 is input.
[0167]
In S606, the CPU 351 determines whether or not the counter value: C updated in S605 is equal to or longer than the predetermined time: Cb, in other words, the elapsed time from the point in time when the additional fuel pressure: P1 is input is equal to or longer than the predetermined time: Cb It is determined whether or not it has become.
[0168]
If it is determined in S606 that the counter value: C is less than the predetermined time: Cb, the CPU 351 repeatedly executes the processing from S605 described above until the counter value: C reaches the predetermined time: Cb or more.
[0169]
When it is determined in S606 that the counter value: C is equal to or more than the predetermined time: Cb, that is, when it is determined that the elapsed time from the time when the added fuel pressure: P1 is input has reached the predetermined time: Cb or more, The CPU 351 proceeds to S607, and inputs again the output signal value of the reducing agent pressure sensor 32 (the added fuel pressure in the closed space): P2 at that time.
[0170]
In S608, the CPU 351 reads the added fuel pressure: P1 detected in S604 from the RAM 353. The CPU 351 calculates the absolute value of the difference between the added fuel pressure: P1 and the added fuel pressure: P2 input in S607, and the calculated absolute value (| P1-P2 |) is equal to or more than a predetermined change amount: ΔP. Is determined.
[0171]
The above-mentioned change amount: ΔP is a value obtained by experimentally obtaining a change amount of the added fuel pressure when the reducing agent supply mechanism does not cause leakage of the reducing agent, and a value such as the outside air temperature or the fuel temperature. This is a value obtained by adding a margin considering external factors. The amount of change: ΔP may be stored in a predetermined area of the ROM 352 in advance.
[0172]
If it is determined in S608 that the absolute value (| P1−P2 |) of the difference between the added fuel pressure: P1 and the added fuel pressure: P2 is smaller than the change amount: ΔP, the CPU 351 supplies the reducing agent. The process proceeds to S612 assuming that no leakage of fuel has occurred in the mechanism.
[0173]
In S612, the CPU 351 resets “0” to the reducing agent leakage flag storage area of the RAM 353. The CPU 351 that has finished executing the processing of S612 resets the counter value: C in the counter storage area to “0” in S611, and ends the execution of this routine.
[0174]
On the other hand, if it is determined in S608 that the absolute value (| P1−P2 |) of the difference between the added fuel pressure: P1 and the added fuel pressure: P2 is equal to or larger than the change amount: ΔP, the CPU 351 returns The process proceeds to S609 assuming that fuel leakage has occurred in the agent supply mechanism.
[0175]
In S609, the CPU 351 sets “1” in the reducing agent leakage flag storage area of the RAM 353.
[0176]
In S610, the CPU 351 turns on a warning lamp (not shown) provided in the vehicle interior.
[0177]
In S611, the CPU 351 resets the counter value: C in the counter storage area to “0”. After completing the process of S611, the CPU 351 terminates the execution of this routine.
[0178]
According to the above-described embodiment, a closed space is formed in the reducing agent addition mechanism, and the leakage of the reducing agent is determined based on the pressure change of the closed space for a predetermined period. Can be detected.
[0179]
<Embodiment 3>
Next, a third embodiment of the abnormality detecting device for the reducing agent supply device according to the present invention will be described with reference to FIGS. Here, a configuration different from the above-described second embodiment will be described, and a description of a similar configuration will be omitted.
[0180]
In the above-described second embodiment, an example was described in which a closed space was formed in the reducing agent addition mechanism, and leakage of the reducing agent was determined based on a pressure change in the closed space for a predetermined period. The longer the predetermined period (judgment period), the easier it is to detect a small pressure change. Therefore, in order to detect the leakage of a very small amount of reducing agent, it is preferable to make the judgment period longer.
[0181]
However, when the reducing agent leak determination control is being executed, the flow rate adjusting valve 30 and the shutoff valve 31 are kept closed, and the reducing agent addition control cannot be executed. Becomes longer, the execution prohibition period of the reducing agent addition control becomes longer, which may lead to deterioration of exhaust emission.
[0182]
Therefore, in the reducing agent leakage determination control according to the present embodiment, the CPU 351 holds the flow regulating valve 30 and the shutoff valve 31 in a closed state during a period from the time when the operation of the internal combustion engine 1 is stopped to the time when it is restarted. Leakage of the reducing agent is determined based on the change in the added fuel pressure during that period.
[0183]
Hereinafter, the reducing agent leakage determination control according to the present embodiment will be described with reference to the flowcharts of FIGS. 7 and 8.
[0184]
The flowchart shown in FIG. 7 is a flowchart showing a first reducing agent leak determination control routine. This first reducing agent leak determination control routine is executed by the CPU 351 at predetermined time intervals (for example, when the crank position sensor 33 This is a routine that is repeatedly executed each time a pulse signal is output.
[0185]
On the other hand, the flowchart shown in FIG. 8 is a flowchart showing a second reducing agent leakage determination control routine. This second reducing agent leakage determination control routine is performed when the internal combustion engine 1 is started. This is a routine that is executed by the CPU 351 in response to a switch being switched from off to on.
[0186]
First, in the first reducing agent leak determination control routine, the CPU 351 determines in S701 whether or not the operation of the internal combustion engine 1 has been stopped. As a method of determining the operation stop of the internal combustion engine 1, a method of determining the operation stop of the internal combustion engine 1 on the condition that an ignition switch (not shown) is switched from on to off, and the engine speed decreases to less than a predetermined number of times For example, a method of determining whether to stop the operation of the internal combustion engine 1 on the basis of the above can be exemplified.
[0187]
If it is determined in step S701 that the operation of the internal combustion engine 1 has not been stopped, in other words, that the internal combustion engine 1 is in the operating state, the CPU 351 ends the execution of this routine once.
[0188]
On the other hand, if it is determined in S701 that the operation of the internal combustion engine 1 has been stopped, the CPU 351 proceeds to S702, closes both the flow control valve 30 and the shutoff valve 31, and moves from the flow control valve 30 to the shutoff valve 31. Let the path be a closed space.
[0189]
In S703, the CPU 351 inputs the output signal value of the reducing agent pressure sensor 32 (addition fuel pressure immediately after the engine operation is stopped): P1.
[0190]
In S704, the CPU 351 stores the added fuel pressure: P1 input in S703 in a predetermined area of the backup RAM 354. The CPU 351 that has finished executing the processing of S704 ends the execution of this routine.
[0191]
Next, in the second additive leakage determination control routine, the CPU 351 first determines in S801 whether the internal combustion engine 1 is in a start state or a start complete state. Examples of a method for determining the start state of the internal combustion engine 1 include a method for determining that the internal combustion engine 1 is in a start state on condition that a starter switch (not shown) is switched from off to on. Further, as a method of determining the start completion state of the internal combustion engine 1, a method of determining that the internal combustion engine 1 is in the start completion state on condition that the engine speed is equal to or higher than a predetermined speed can be exemplified. .
[0192]
When it is determined in S801 that the internal combustion engine 1 is not in the start state or the start completion state, that is, when it is determined that the internal combustion engine 1 is in the operation stop state, the CPU 351 ends the execution of this routine.
[0193]
On the other hand, if it is determined in S801 that the internal combustion engine 1 is in the starting state or the starting completed state, the CPU 351 proceeds to S802, accesses the reducing agent leakage flag storage area of the RAM 353, and stores “1”. It is determined whether or not there is.
[0194]
If it is determined in step S802 that “1” has already been stored in the reducing agent leakage flag storage area, the CPU 351 proceeds to step S810, turns on a warning lamp provided in the vehicle interior, and returns to the driver of the vehicle. Encourages repair of the agent supply mechanism.
[0195]
On the other hand, if it is determined in step S802 that “1” is not stored in the reducing agent leakage flag storage area, the CPU 351 proceeds to step S803 and inputs an output signal value (cooling water temperature) of the water temperature sensor 34.
[0196]
In S804, the CPU 351 determines whether the cooling water temperature input in S803 is equal to or higher than a predetermined temperature.
[0197]
If it is determined in S804 that the cooling water temperature is lower than the predetermined temperature, the CPU 351 determines that an excessive time has elapsed from the time when the operation of the internal combustion engine 1 is stopped to the time when it is restarted, and executes this routine. To end.
[0198]
This is because if the elapsed time from the stop of the operation of the internal combustion engine 1 to the restart of the internal combustion engine 1 becomes excessively long, even if the leakage of the reducing agent does not occur in the closed space, the outside air temperature, the temperature in the engine room of the vehicle, Alternatively, the added fuel pressure in the closed space may significantly change due to an external factor such as the fuel temperature, and if the determination of the leakage of the reducing agent is performed in such a situation, an erroneous determination may be caused. It is.
[0199]
The temperature of the lubricating oil (oil temperature) of the internal combustion engine 1 may be used instead of the cooling water temperature as a parameter for estimating the elapsed time from when the operation of the internal combustion engine 1 is stopped to when it is restarted. Both of the oil temperatures may be used.
[0200]
On the other hand, if it is determined in step S804 that the cooling water temperature is equal to or higher than the predetermined temperature, the CPU 351 determines that an excessive time has not elapsed from the time when the operation of the internal combustion engine 1 was stopped until the time when the internal combustion engine 1 was restarted. move on.
[0201]
In S805, the CPU 351 maintains the closed state of the flow control valve 30 and the shutoff valve 31, and maintains the reducing agent supply path 29 from the shutoff valve 31 to the flow control valve 30 in a closed space.
[0202]
In S806, the CPU 351 inputs the output signal value of the reducing agent pressure sensor 32 (the added fuel pressure in the closed space): P2.
[0203]
In S807, the CPU 351 reads, from a predetermined area of the backup RAM 354, the added fuel pressure: P1 detected immediately after the operation of the internal combustion engine 1 is stopped.
[0204]
In S808, the CPU 351 calculates the absolute value of the difference between the added fuel pressure: P2 detected in S806 and the added fuel pressure: P1 read in S807, and calculates the calculated absolute value (| P1-P2 |). Is greater than or equal to a predetermined change amount: ΔP.
[0205]
The above-mentioned change amount: ΔP is a value obtained by experimentally obtaining a change amount of the added fuel pressure when the reducing agent supply mechanism does not cause leakage of the reducing agent, and a value such as the outside air temperature or the fuel temperature. This is a value obtained by adding a margin considering external factors.
[0206]
If it is determined in S808 that the absolute value (| P1−P2 |) of the difference between the added fuel pressure: P1 and the added fuel pressure: P2 is less than the change amount: ΔP, the CPU 351 supplies the reducing agent. The process proceeds to S811 on the assumption that no leakage of fuel has occurred in the mechanism.
[0207]
In S811, the CPU 351 resets “0” in the reducing agent leakage flag storage area of the RAM 353. The CPU 351 that has finished executing the processing of S811 ends the execution of this routine.
[0208]
On the other hand, if it is determined in S808 that the absolute value (| P1−P2 |) of the difference between the added fuel pressure: P1 and the added fuel pressure: P2 is equal to or greater than the change amount: ΔP, the CPU 351 returns The process proceeds to S809 on the assumption that fuel leakage has occurred in the agent supply mechanism.
[0209]
In S809, the CPU 351 sets “1” in the reducing agent leakage flag storage area of the RAM 353.
[0210]
In S810, the CPU 351 turns on a warning lamp (not shown) provided in the vehicle interior. The CPU 351 that has finished executing the processing of S810 ends the execution of this routine.
[0211]
According to the above-described embodiment, a closed space is formed in the reducing agent addition mechanism for a relatively long period from the time when the operation of the internal combustion engine 1 is stopped to the time when the internal combustion engine 1 is restarted, and based on the pressure change in the closed space. Since the leak of the reducing agent is determined, it is possible to detect the leak of the trace amount of the reducing agent.
[0212]
【The invention's effect】
According to the abnormality detection device for the reducing agent supply device according to the present invention, it is possible to detect the leakage of the reducing agent based on the pressure of the reducing agent in the reducing agent supply mechanism. Thus, it is possible to contribute to suppression of deterioration of exhaust emission caused by excessive supply or insufficient supply of the reducing agent to the exhaust purification catalyst, prevention of breakage of the exhaust purification catalyst, and the like.
[0213]
Further, when the abnormality detection device of the reducing agent supply device according to the present invention includes a blocking unit that blocks the flow of the reducing agent from the reducing agent discharge unit to the reducing agent supply path, Since the path leading to the reducing agent addition section is a closed space, and the leakage of the reducing agent can be determined based on the pressure change in the closed space, it is possible to detect the leakage of a relatively small amount of the reducing agent. Become.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an abnormality detection device for a reducing agent supply device according to the present invention is applied and an intake and exhaust system thereof.
FIG. 2 (A) is a diagram for explaining the NOx storage mechanism of a storage-reduction type NOx catalyst.
(B) Diagram for explaining the NOx release mechanism of the NOx storage reduction catalyst
FIG. 3 is a block diagram showing an internal configuration of an ECU.
FIG. 4 is a diagram showing a relationship between a pump corresponding pressure and an engine speed;
FIG. 5 is a flowchart illustrating a reducing agent leakage determination control routine according to the first embodiment.
FIG. 6 is a flowchart illustrating a reducing agent leakage determination control routine according to a second embodiment.
FIG. 7 is a flowchart illustrating a first reducing agent leak determination control routine according to a third embodiment;
FIG. 8 is a flowchart showing a second reducing agent leakage determination control routine according to the third embodiment.
[Explanation of symbols]
1 ... Internal combustion engine
2 .... cylinder
3 ... Fuel injection valve
4 .... Common rail
5. Fuel supply pipe
6. Fuel pump
18 ・ ・ ・ Exhaust branch pipe
19 ・ ・ ・ Exhaust pipe
20 ... NOx storage reduction catalyst
21 ・ ・ ・ Exhaust throttle valve
25 ... EGR passage
26 ... EGR valve
27 ・ ・ ・ EGR cooler
28 ・ ・ ・ Reducing agent injection valve
29 ・ ・ ・ Reducing agent supply path
30 ・ ・ ・ Flow control valve
31 ... shut-off valve
32 ... Reducing agent pressure sensor
33 ・ ・ ・ Crank position sensor
34 ・ ・ ・ Water temperature sensor
35 ... ECU
351 CPU
352 ROM
353 RAM
354 .. Backup RAM

Claims (4)

An exhaust purification catalyst provided in an exhaust passage of the internal combustion engine to purify harmful gas components in exhaust gas in the presence of the reducing agent; a reducing agent supply mechanism for supplying the reducing agent to an exhaust passage upstream of the exhaust purification catalyst; a pressure detecting means for detecting the pressure of the reducing agent in the reducing agent supply mechanism, the reducing agent supply device comprising an abnormality judging means for judging an abnormality of the reducing agent supply mechanism based on the pressure detected by the pressure detecting means, Abnormality detection device,
The reducing agent supply mechanism includes a reducing agent discharge unit that discharges the reducing agent at a predetermined pressure, and a reducing agent addition unit that is provided in an exhaust passage upstream of the exhaust gas purification catalyst and adds the reducing agent to exhaust gas flowing through the exhaust passage. A reducing agent supply path for guiding the reducing agent discharged from the reducing agent discharging section to the reducing agent adding section, and a shutoff section for blocking a flow of the reducing agent from the reducing agent discharging section to the reducing agent supply path. And
The reducing agent pressure detecting means detects a pressure in the reducing agent supply passage downstream of the blocking unit,
The abnormality determining unit determines an abnormality of the reducing agent supply mechanism based on a pressure detected by the pressure detecting unit when the blocking unit interrupts the flow of the reducing agent in the reducing agent supply path. Abnormality detecting device for the reducing agent supply device. The abnormality determining means may be configured such that a change amount of the pressure detected by the pressure detecting means exceeds a predetermined amount when the shutoff unit is blocking the flow of the reducing agent from the reducing agent discharge unit to the reducing agent supply path. 2. The abnormality detecting device for a reducing agent supply device according to claim 1 , wherein it is determined that the reducing agent supply mechanism is abnormal. The abnormality determining means is configured such that a deviation between a pressure detected by the pressure detecting means when the operation of the internal combustion engine is stopped and a pressure detected by the pressure detecting means when the internal combustion engine is restarted exceeds a predetermined amount. 3. The abnormality detecting device for a reducing agent supply device according to claim 2, wherein it is determined that the reducing agent supply mechanism is abnormal. The abnormality determining means, the elapsed time until the restart when the operation stop of the internal combustion engine is equal to or greater than a predetermined time, according to claim 3, characterized in that prohibiting abnormality determination of the reducing agent supply mechanism Abnormality detection device for the reducing agent supply device.

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