JP3511967B2 - Abnormality detection device for particulate filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate filter abnormality detection device for detecting abnormality, particularly damage, of a particulate filter.

[0002]

2. Description of the Related Art Exhaust gas from internal combustion engines, especially exhaust gas from diesel engines, contains particulate matter (PM) containing carbon as a main component. There is known a technique of providing a particulate filter (DPF) for trapping PM in an engine exhaust system in order to prevent the emission of these PM into the atmosphere. The DPF is usually provided with a filter element such as a metal mesh or a porous ceramic, and the filter element collects PM in the exhaust gas.

However, the DPF is subject to vibrations due to engine operation, high heat of exhaust gas, and thermal cycle stress due to engine stop and repeated operation. When the DPF is damaged, the PM in the exhaust gas is not captured by the DPF and is released to the atmosphere as it is, which causes a problem of deteriorating the surrounding environment. Further, even if the DPF is damaged, the operation itself of the engine is not adversely affected. For this reason, the driver
In many cases, even if F is damaged, the operation is continued without being noticed, which may further deteriorate the environment.

For this reason, an abnormality detecting device for detecting an abnormality such as damage of the DPF during engine operation has been conventionally proposed. An example of this type of DPF abnormality detecting device is described in Japanese Patent Application Laid-Open No. 8-121150. In the device of the publication, a sound sensor is arranged at a position on the filter element downstream side in a filter case accommodating a DPF filter element, and the sound signal detected by the sound sensor exceeds a predetermined threshold value. In this case, it is determined that the filter element is damaged.

[0005]

However, as in the device disclosed in Japanese Patent Laid-Open No. 8-121150, in order to determine whether the DPF is damaged or not based on the size of the sound signal detected by the sound sensor, the DPF Since it is necessary to provide a sound sensor and a sound signal processing circuit only for detecting damage, there is a problem that the device itself becomes complicated and the device cost rises. Also,
Since various noises are generated according to the operating state during engine operation, there is a problem that an erroneous determination is likely to occur if the presence or absence of damage to the DPF is detected only by the sound signal.

In view of the above problems, it is an object of the present invention to provide a DPF abnormality detecting device capable of easily and accurately detecting an abnormality such as DPF damage without providing a special sensor such as a sound sensor. I am trying.

[0007]

According to the invention described in claim 1, there is provided a particulate filter abnormality detecting device for detecting whether or not a particulate filter arranged in an exhaust passage of an internal combustion engine is damaged. While detecting the EGR passage connecting the engine exhaust system and the engine intake system, the EGR valve arranged in the EGR passage, and the engine intake air amount,
By controlling the EGR valve opening, the recirculation exhaust gas is recirculated from the exhaust system to the intake system through the EGR passage so that the engine intake air amount becomes a target intake air amount that is predetermined according to the engine operating state. E for feedback control of flow rate
It is the EGR valve opening degree in each engine operating state when the feedback control of the recirculated exhaust gas flow rate by the EGR control means is being performed in the reference state where the GR control means and the particulate filter are in a normal state. Storage means for storing the reference EGR valve opening degree in advance;
The EGR valve opening is detected during the feedback control of the recirculation exhaust flow rate by the control means, and the detected actual EG is detected.
When the R valve opening degree is larger than the reference EGR valve opening degree corresponding to the current operating state stored in the storage means, it is determined that an abnormality has occurred in the particulate filter, and the particulate means. A filter abnormality detection device is provided.

That is, according to the first aspect of the invention, the EGR valve opening degree during execution of the recirculation exhaust gas (EGR gas) flow rate control by the EGR control means is detected, and this opening degree is used as the reference EGR valve opening degree in the same operating state of the engine. DPF by comparing with
The presence or absence of abnormality is detected. Generally, when the DPF is damaged, the pressure loss of the exhaust gas passing through the DPF sharply decreases, and the exhaust back pressure of the engine decreases, so that the pressure difference across the EGR valve decreases. However, in the present invention, the EGR valve is the EGR valve.
Since the control means controls the EGR gas amount to be constant, when the engine exhaust back pressure decreases, the opening degree of the EGR valve is increased to maintain the EGR gas flow rate constant.

In the present invention, the reference state, that is, the DPF is in a normal state (for example, the DPF is not damaged, and the DPF is
EG during engine operation when PM is not collected in
A storage unit is provided that stores in advance the relationship between each engine operating state (for example, engine speed and fuel injection amount) during R control and the corresponding EGR valve opening degree. If the DPF is in the same state as the reference state during the actual operation of the engine, the EGR
The EGR valve opening during control is supposed to be equal to the reference EGR valve opening in the same engine operating state in the reference state (for example, operating state in which the engine speed and the fuel injection amount are the same).

On the other hand, if the DPF is damaged, the EGR
The valve opening is increased as compared with the case where the DPF is not damaged. Therefore, when the actual EGR valve opening is larger than the reference EGR valve opening corresponding to the same engine operating state, it can be determined that an abnormality such as damage to the DPF has occurred. In the present invention, focusing on the above, the DPF abnormality can be detected simply and accurately without using a sound sensor or the like.

According to the second aspect of the present invention, there is provided a particulate filter abnormality detecting device for detecting the presence or absence of damage of the particulate filter arranged in the exhaust passage of the internal combustion engine, which is arranged in the engine exhaust system. An exhaust turbocharger equipped with an exhaust turbine driven by the engine exhaust flow and a compressor arranged in the engine intake system to boost the engine intake air, an intake air temperature detection means for detecting the engine intake air temperature, and a particulate filter A storage unit that stores in advance a reference intake air temperature that is an intake air temperature in each engine operating state in a normal state, which is a normal state, and an engine intake air temperature detected by the intake air temperature detecting unit during engine operation are stored in the storage unit. When the temperature is higher than the reference intake air temperature corresponding to the current engine operating state including the engine intake air amount stored in the means, there is an abnormality in the particulate filter. A determination unit that Flip, the abnormality detecting apparatus of the particulate filter with is provided.

That is, according to the second aspect of the invention, the DPF abnormality is detected by comparing the engine intake air temperature with the reference intake air temperature in the same operating condition in the reference condition. In addition,
In this specification, the engine intake air means the temperature at the engine inlet (intake port) of the engine intake pipe, and the engine intake air means fresh air at the engine intake pipe inlet. As described above, when the DPF is damaged, the pressure loss of the exhaust gas passing through the DPF sharply decreases. For this reason, in an engine equipped with a supercharger having an exhaust turbine, even if the engine operating conditions are the same, the exhaust energy given to the exhaust turbine will be smaller when the DPF is damaged than when the DPF is normal. Increase. For example, when the DPF is arranged in the exhaust passage on the upstream side of the exhaust turbine, when the pressure loss of the DPF decreases, the exhaust pressure at the exhaust turbine inlet increases and the expansion ratio of the exhaust turbine increases. Also, when the DPF is arranged in the exhaust passage on the downstream side of the exhaust turbine, the exhaust back pressure at the exhaust turbine outlet decreases when the pressure loss of the DPF decreases.
The expansion ratio of the exhaust turbine increases. For this reason, if the DPF is damaged regardless of the position of the DPF, the expansion ratio of the exhaust turbine increases and the supercharger rotation speed increases. Therefore, in the compressor of the supercharger, the supercharging pressure increases and the intake air temperature at the compressor outlet rises. Therefore, if the DPF is damaged, the engine intake air temperature will rise.

In the present invention, as in the case of claim 1, the DP
When the engine is operated in the standard condition of F, that is, when the DPF is normal, the relationship between the engine operating condition including the intake air amount (for example, intake air amount, engine speed, fuel injection amount) and engine intake temperature is shown. It is stored in advance in the storage means. If the DPF is in the same state as the reference state during the actual operation of the engine, the engine intake air temperature is the same as the reference intake air in the same engine operating state (for example, the operating state in which the intake air amount, engine speed, and fuel injection amount are the same). Should be equal to temperature.

On the other hand, if the DPF is damaged, the intake air temperature rises as compared with the case where the DPF is not damaged. Therefore, when the actual intake air temperature is higher than the reference intake air temperature corresponding to the same engine operating state including the intake air amount, it can be determined that the DPF has an abnormality such as damage. It should be noted that the actual engine intake air temperature is compared with the reference intake air temperature corresponding to the same engine operating state including the intake air amount even if the engine speed, the fuel injection amount, etc. are the same, the intake throttle of the engine, etc. This is because the engine intake air temperature may change when the intake air amount changes.

In the present invention, similarly to the first aspect, it becomes possible to detect the damage of the DPF easily and accurately without disposing a sound sensor or the like. Further, since the DPF abnormality detection of the present invention does not use the EGR valve opening degree, for example, an engine operating region where EGR is not performed or an operating region where the EGR valve is held in a fully opened state in a region where a large amount of EGR gas is recirculated Also in the above, the DPF abnormality is accurately detected.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of an embodiment in which the present invention is applied to an automobile diesel engine. In FIG. 1, 1 is a diesel engine main body,
Reference numeral 2 is an intake passage of the engine 1, 20 is a surge tank provided in the intake passage 2, and 21 is an intake branch pipe connecting the surge tank 20 and the intake port of each cylinder. In this embodiment,
The intake passage 2 is provided with an intake throttle valve 27 that throttles the flow rate of intake air flowing through the intake passage 2 and an intercooler 26 that cools the intake air. The intake throttle valve 27 is a solenoid,
An electronic control unit (EC which will be described later) is provided with an actuator 27a of an appropriate type such as a vacuum actuator.
U) The opening degree according to the control signal from 30 is taken. In the present embodiment, the intake throttle valve 27 reduces the intake pressure, for example, when the engine is running at a low speed, to increase the amount of exhaust gas (EGR gas) that flows back to the surge tank 20 through the EGR passage 33 described later. Used.

Reference numeral 25 in FIG. 1 denotes an air flow meter provided near the intake inlet of the intake passage 2. In the present embodiment, the air flow meter 25 is of a type that can measure the mass flow rate of the intake air flowing through the intake passage 2, such as a hot wire type flow meter. After passing through the air flow meter 25, the atmosphere flowing into the intake passage 2 is boosted by the compressor of the exhaust supercharger (turbocharger) 35 and cooled by the intercooler 26 provided in the intake passage 2, and the surge tank 20, It is sucked into each cylinder through the branch pipe 21.

Reference numeral 111 in FIG. 1 denotes a fuel injection valve for directly injecting fuel into each cylinder. Fuel injection valve 111
Is a common accumulator (common rail) that stores high-pressure fuel
It is connected to 115. The fuel of the engine 1 is pressurized by the high-pressure fuel pump 113 and supplied to the common rail 115, and is directly injected into each cylinder from the common rail 115 via each fuel injection valve 111.

Further, reference numeral 31 in FIG. 1 denotes an exhaust manifold for connecting the exhaust port of each cylinder and the exhaust passage 3, and 35.
Shown in is a turbocharger. The turbocharger 35 includes an exhaust turbine 35a driven by the exhaust gas in the exhaust passage 3 and an intake compressor 35b driven by the exhaust turbine 35a. Further, in the present embodiment, the exhaust passage 3 is provided on the exhaust passage 3 on the downstream side of the turbocharger 35.
An exhaust throttling valve 37 for throttling the flow rate of exhaust gas flowing through is disposed. The exhaust throttle valve 37 includes an actuator 37a similar to the intake throttle valve 27, and takes a fully open position and a closed position with a predetermined opening degree according to a control signal from the ECU 30.
In the present embodiment, the exhaust throttle valve 37 is used when raising the exhaust temperature for regeneration of the particulate filter 43.

Further, in the present embodiment, an EGR device for recirculating a part of the engine exhaust gas to the intake system is provided. EGR
The apparatus includes an EGR passage 33 that connects the exhaust manifold 31 and the intake surge tank 20, an EGR valve 23 arranged on the EGR passage 33, and an EGR cooler 45 provided in the EGR passage upstream of the EGR valve 23. ing. The EGR valve 23 includes an actuator such as a stepper motor and a solenoid actuator (not shown), and the ECU
The opening degree corresponding to the control signal from 30 is taken, and the EGR passage 3
Exhaust gas that recirculates to the intake surge tank 20 through
R gas) flow rate is controlled. In this embodiment, a relatively large amount of EG is used in a wide operating range from the low load range to the high load range.
The EGR valve 23 is controlled to recirculate the R gas.
Therefore, in this embodiment, the intake air taken into each cylinder contains a relatively large amount of EGR gas. EGR
Since the gas is the high-temperature exhaust gas discharged from the cylinder, when a large amount of EGR gas is recirculated to the intake air, the intake temperature rises, and the intake volume efficiency of the engine decreases. In the present embodiment, in order to prevent this, a water-cooled or air-cooled EGR cooler 45 is provided in the EGR passage 33 on the upstream side of the EGR valve 23. In the present embodiment, the EGR cooler 45 is used to lower the temperature of the EGR gas that recirculates to the intake system, so that a reduction in the intake volume efficiency of the engine can be suppressed and a relatively large amount of EGR gas can be recirculated. ing.

Reference numeral 30 in FIG. 1 is an electronic control unit (ECU) of the engine 1. ECU 30 of the present embodiment
Is configured as a microcomputer having a known configuration, and has a configuration in which a CPU, a RAM, a ROM, an input port and an output port are connected to each other by a bidirectional bus. E
The CU 30 performs basic control such as fuel injection control and rotation speed control of the engine 1, and in this embodiment, as will be described later, feedback control of the EGR valve 23 opening based on the engine intake air amount and EGR valve opening. Based on the engine intake air temperature, the DPF abnormality detection operation is performed.

In order to perform these controls, a signal corresponding to the engine rotational speed NE is input to the input port of the ECU 30 from the rotational speed sensor 55 arranged near the crankshaft of the engine 1 and the air flow meter 25. A signal corresponding to the engine intake air amount (mass flow rate) Gn is output from the accelerator opening sensor 57 arranged near the engine accelerator pedal.
A signal corresponding to the driver's accelerator pedal depression amount (accelerator opening) ACCP is
It is input through the D converter. In addition, the EGR valve 23 is further provided at the input port of the ECU 30.
Signal VEG representing the EGR valve opening from the valve opening sensor 51
However, a signal representing the engine intake air temperature is also input from the intake air temperature sensor 59 arranged in the engine intake surge tank 20.

The output port of the ECU 30 is connected to the fuel injection valve 111 of the engine 1 via a fuel injection circuit (not shown), and controls the fuel injection amount from the fuel injection valve 111 and the fuel injection timing. The output port of the ECU 30 is connected to the EGR valve 23 and the intake throttle valve 2 via a drive circuit (not shown).
7 and the actuator of the exhaust throttle valve 37,
Each valve opening is controlled.

Although the EGR valve opening sensor 51 for detecting the EGR valve opening is separately provided in this embodiment, a stepper motor is used as the actuator of the EGR valve 23 without providing the opening sensor 51. In the case, based on the number of driving steps of the motor, and in the case of using a solenoid actuator as an actuator, based on the duty ratio of the solenoid drive pulse ON / OFF (the ratio of ON time of the drive pulse ON / OFF 1 cycle) E
It is also possible to calculate the GR valve opening.

In this embodiment, the exhaust purification catalyst 4 of a known type such as a three-way catalyst is provided downstream of the exhaust throttle valve in the exhaust passage 3.
1 and a particulate filter (DPF) 43 are arranged. The DPF 43 is composed of, for example, a filter made of a metal mesh, a ceramic porous material, or the like, and collects particulate matter (PM) in the exhaust gas. As described above, since the DPF 43 is arranged in the engine exhaust passage,
Vibration of the engine acts at high temperature. Further, the DPF 43 is repeatedly heated and cooled when the engine is stopped. For this reason, for example, when using a filter in which a metal mesh (metal non-woven fabric, etc.) is wound into a spiral cylinder, the center of the spiral filter is pushed out in the axial direction by repeating heating and cooling. There is a case where it is damaged by breakage or cracks are generated in a ceramic porous filter or the like. When the DPF is damaged, PM in the engine exhaust is discharged to the atmosphere without being collected by the filter. In addition, even if the DPF is damaged, the engine does not experience performance deterioration such as output reduction and deterioration of acceleration that the driver immediately notices. Therefore, the driver does not notice the damage of the DPF and the engine remains in the damaged state. May be operated for a long time.

Therefore, it is necessary to detect the damage of the DPF and notify the driver. In the present embodiment, the means described below detects damage to the DPF easily and accurately without using a special sensor such as a sound sensor. An embodiment of the DPF damage detection operation of the present invention will be described below.

(1) First Embodiment In this embodiment, the EGR valve opening degree VEG detected during execution of EGR feedback control based on the engine intake air amount
Is compared with a reference EGR valve opening degree VEGS, which is an EGR valve opening degree when the engine is operated under the same operating condition (same engine speed, fuel injection amount) in the DPF reference state. To detect. In addition, DP
The reference state of F means a state in which there is no damage such as cracking or tearing in the DPF, and the amount of collected PM is zero, that is, a new state immediately after mounting the DPF.

Hereinafter, the abnormality detection operation of the DPF of the present embodiment will be described, but before that, the EGR feedback control based on the engine intake air amount, which is the premise thereof, will be described. The exhaust gas of an internal combustion engine has a low oxygen concentration,
It functions as an inert gas that does not contribute to combustion. Therefore, generation of nitrogen oxides from combustion and reduced combustion air excess ratio of the engine by supplying (NO _X) is suppressed part of the exhaust as EGR gas into the combustion chamber. Generally the amount of exhaust gas to be recirculated to the combustion chamber but _the amount of NO _X generated as (EGR amount) is increased is reduced, the problem of the lack of oxygen in the combustion chamber and to increase the EGR amount excessively the combustion state deteriorates is there. Particularly in a diesel engine, problems such as increase in PM in exhaust gas and generation of exhaust smoke occur as the EGR amount increases.

Therefore, when the NO _X in the exhaust gas is suppressed by the EGR, the EGR rate (in this specification, the EGR rate is maximized so that the NO _X suppressing effect is maximized in the range where the deterioration of combustion and the increase of PM do not occur. EG in the mass of intake air drawn into the engine
It is necessary to accurately control the ratio of the mass of R gas, that is, EGR mass / (fresh air mass + EGR amount) is referred to as EGR rate) according to the engine operating state.

In this embodiment, the actual air intake amount of the engine (mass flow rate of the fresh air drawn into the engine) is detected by the air flow meter 25, and the detected intake air amount is the engine operating condition such as the engine load and the rotational speed. By performing feedback control of the opening degree of the EGR valve 23 so that the target intake air amount predetermined according to the above, the EGR rate according to the engine operating state is always obtained.

The volumetric flow rate of the intake air (mixture of fresh air and EGR gas) taken into the engine has a substantially constant value according to the operating condition of the engine. Therefore, when the engine operating condition is constant, if the amount of EGR gas that recirculates to the intake system is increased, the amount of fresh air drawn into the engine is reduced, and EG
If the amount of R gas is reduced, the amount of fresh air drawn into the engine will increase. Therefore, the amount of fresh air drawn into the engine (mass flow rate)
Is detected and the EGR valve opening is feedback-controlled so that this mass flow rate becomes a target value determined according to the engine operating state, so that the engine is supplied with the optimum amount of fresh air and EGR gas according to the operating state. Can be supplied. As a result, the fresh air amount in the intake air of the engine and the EGR rate are controlled to the optimum values according to the operating state, and the amount of PM in the exhaust gas is not increased and the exhaust smoke is not generated. N
The O _X can be reduced maximally.

FIG. 2 is a flow chart for specifically explaining the EGR feedback control operation (hereinafter referred to as "EGR feedback (F / B) control operation") based on the engine intake air amount in the present embodiment. This operation is performed as a routine executed by the ECU 30 at regular intervals. In the EGR feedback control operation of FIG. 2, first, at step 201, the engine speed NE and the intake air amount G are determined from the engine speed sensor 55 and the air flow meter 25.
n and n are read, and the value of the engine fuel injection amount Q _fin calculated by the fuel injection amount calculation operation separately executed by the ECU 30 is read.

In the present embodiment, the ECU 30 performs the fuel injection operation based on a predetermined relationship using the accelerator opening ACCP detected by the accelerator opening sensor 57 and the engine speed NE by the fuel injection calculation operation. The amount Q _fin is calculated. Since the value of the fuel injection amount Q _{fin is} a value corresponding to the engine load torque, in the present embodiment, the fuel injection amount Q _{fin
The fin} and the engine speed NE are used as parameters representing the engine operating state.

Next, at step 203, the value of the target intake air amount Gnt is calculated based on the rotational speed NE and the fuel injection amount Q _fin read as described above. The target intake air amount Gnt is the EGR rate (the ratio of EGR gas in the intake air taken into the engine, that is, (EGR gas amount) /
The intake air amount is preset for each operating state so that (EGR gas amount + intake air amount Gn)) becomes a predetermined value determined according to the engine operating state. That is, in order to reduce engine combustion temperatures to reduce the by the engine NO _X (nitrogen oxides) is preferably supplied to the large amount of the engine combustion chamber EGR gas as an inert gas. However, if the EGR gas amount supplied to the combustion chamber becomes excessively large, the engine combustion state deteriorates and the output decreases. Therefore, in the present embodiment, an optimum EGR rate is set in advance based on an experiment using an actual engine in accordance with the engine operating state, and the ratio of the intake air amount Gn and the EGR gas amount becomes the optimum EGR rate. The intake air amount in each of the following operating states is set as the target intake air amount Gnt. That is, when the engine operating conditions such as the engine speed NE and the fuel injection amount Q _fin are determined, the total intake air amount (EGR gas amount + intake air amount Gn) taken into the engine combustion chamber.
Is set to a constant value according to the driving condition. Therefore, N
If the optimum EGR rate is set in advance according to the operating state of E, Q _fin, etc., the intake air amount Gnt required to obtain the EGR rate will also be determined. In the present embodiment, the target intake air amount Gnt for obtaining the optimum EGR rate for each engine operating state determined in advance from NE and Q _fin is calculated, and the value of this target intake air amount Gnt is set to NE and Q fin. _fin
ECU 3 in the form of a numerical table using
It is stored in 0 ROM. Performing an operation for obtaining the target intake air amount Gnt from this numerical table based read the current and the rotational speed NE and the fuel injection amount Q _{fi n} in FIG. 2, step 203 in step 201.

Next, in steps 205 to 213,
The opening degree of the EGR valve 23 is feedback-controlled so that the actual intake air amount Gn matches the target intake air amount Gnt calculated above. That is, in step 205, it is first determined whether or not the actual intake air amount Gn is larger than the target air amount Gnt by a predetermined positive constant value α or more,
When it is larger than α, the target opening degree VEG ₀ of the EGR valve 23 is set to increase by a constant amount ΔV in step 207, and the actual opening degree VEG of the EGR valve 23 is fed back so as to become the target opening degree VEG ₀ in step 213. Control. As a result, the amount of EGR gas recirculated to the intake system increases, and the amount Gn of fresh air drawn into the engine relatively decreases. On the other hand, if Gn−Gnt ≦ α in step 205, then in step 209, the actual intake air amount G
Whether n is smaller than the target air amount Gnt by α or more (Gn-
Gnt <−α), and if smaller than α, the target opening degree VEG ₀ of the EGR valve 23 is decreased by a constant amount ΔV in step 211, and the actual opening degree VEG of the EGR valve 23 is calculated in step 213. Feedback control is performed so that the target opening VEG ₀ becomes. As a result, the amount of EGR gas recirculated to the intake system decreases, and the amount Gn of fresh air drawn into the engine relatively increases. Step two
By executing steps 05 to 213, the actual intake air amount Gn is controlled within the range of ± α with respect to the target intake air amount Gnt. Note that α is a relatively small positive value for preventing control hunting.

As described above, by controlling the EGR so that the intake air amount Gn becomes the target intake air amount Gnt according to the operating condition, the EGR rate of the engine is always maintained at an appropriate value according to the operating condition. Therefore, it is possible to suppress the generation of NO _{X to} the maximum without increasing PM and generating smoke. E based on the engine intake air amount in FIG.
When the opening degree control of the GR valve 23 is carried out, E passing through the EGR valve is maintained when the engine operating state (NE, Q _fin ) is constant.
The GR gas flow rate is kept constant. In this case, as long as the exhaust back pressure of the engine does not change, the pressure difference before and after the EGR valve 23 also becomes constant, so that the opening degree of the EGR valve 23 is kept constant.

However, if the DPF 43 is broken or broken, the pressure loss of the exhaust gas passing through the DPF 43 is significantly reduced, and the exhaust back pressure of the engine is also significantly reduced.
Therefore, even if the engine operating state is the same, if the DPF 43 is damaged, the opening V of the EGR valve 23 is controlled by the control of FIG.
The EG changes according to the exhaust back pressure. That is, if the DPF 43 is damaged and the exhaust back pressure decreases, E
The CU 30 increases the EGR valve opening degree in order to prevent the EGR gas amount from decreasing due to a decrease in exhaust back pressure (the EGR valve 23 upstream side pressure). Therefore, DPF4
If the engine 3 is damaged, if the engine operating condition is the same, the opening degree of the EGR valve 23 is always larger than that when the DPF 43 is normal.

In the present embodiment, the engine is operated by changing the engine speed NE and the fuel injection amount Q _fin in the state where the DPF in the standard state is mounted in advance, and the opening degree of the EGR valve 23 is measured in each operating state. ing. Then, the measured EGR valve opening degree in each operating state is set to the reference EGR valve opening degree VE.
The GS is stored in the ROM of the ECU 30 in the form of a numerical table using the rotational speed NE and the fuel injection amount Q _fin as variables.

In the present embodiment, the ECU 30 executes the EGR feedback control based on the engine intake air amount while the engine operating state at that time (the engine speed NE and the fuel injection amount Q).
_fin ), the reference EGR valve opening degree VE under the same operating condition
Read the GS from the above numerical table to obtain the actual EGR
The valve opening degree VEG is compared. If the actual VEG is larger than the reference EGR valve opening degree VEGS even if the error is taken into consideration, it is determined that the DPF 43 is damaged and the exhaust back pressure is reduced.

FIG. 3 is a flow chart for concretely explaining the above-mentioned abnormality detecting operation of the DPF 43. This operation is performed as a routine executed by the ECU 30 at regular intervals. In the operation of FIG. 3, first, step 301
Then, it is determined whether or not the feedback control (EGRF / B) of the EGR valve opening degree based on the engine intake air amount described in FIG. 2 is currently being executed. If EGRF / B is not currently executed, abnormality detection is performed. Immediately end this operation without performing. As described above, this abnormality detection operation is performed by EGRF / B
This is because it is assumed that is executed.

If EGRF / B is currently being executed at step 301, then at step 303, the current engine speed NE, fuel injection amount Q _fin , and EGR valve 23 opening VEG are read. . Then, in step 305, using the NE and Q _fin read as described above, the reference EG corresponding to the current engine operating state is read from the reference EGR valve opening numerical table stored in the ROM of the ECU 30 in advance.
The value VEGS of the R valve opening is read.

Further, in step 307, the current EGR
It is determined whether the valve opening degree VEG is larger than the reference EGR valve opening degree VEGS by a predetermined value β or more. In step 307, if VEG ≧ VEGS + β, then D
Exhaust back pressure decreases because PF43 is damaged, and EG
Since this means that the opening degree of the R valve 23 is larger than the reference EGR valve opening degree, the routine proceeds to step 309, where the value of the abnormality flag XF is set to 1 and this operation is ended. Flag X
When F is set to 1, in a separate operation performed by the ECU 30, a warning light arranged near the driver's seat is turned on to notify the driver that an abnormality has occurred in the DPF 43.
If VEG <VEGS + β in step 307, it is determined that the DPF 43 is not damaged, and thus the value of the flag XF is not changed and this operation is ended.

The value of β is set to a relatively small positive value for preventing erroneous determination due to a slight change in the EGR valve opening during the EGRF / B control. Further, the initial value of the flag XF is set to 0, and once XF = 1 is set in step 309, the value of XF = 1 is held until it is manually reset to 0 during DPF replacement repair. . As a result, the flag XF once set to 1
The value of is prevented from being accidentally reset when the operation of FIG. 3 is executed.

As described above, by executing the operation of FIG. 3, it is possible to easily and accurately determine the presence / absence of abnormality of the DPF 43 in this embodiment without using a special sensor such as a sound sensor. Becomes

(2) Second Embodiment Next, a second embodiment of the DPF abnormality detecting operation of the present invention will be described. In the above-described first embodiment, the DPF abnormality is determined by comparing the EGR valve opening during EGR feedback control with the reference EGR valve opening. However, in the first embodiment, the fact that the EGR feedback control is being performed is a necessary condition for the DPF abnormality detection operation. Therefore, for example, during operation at a high load where EGR is not performed,
There is a case where the DPF abnormality cannot be detected during operation at a low load such that the exhaust pressure is reduced and a large amount of EGR gas is recirculated so that the EGR valve opening is almost fully opened.

In this embodiment, by detecting whether or not there is an abnormality in the DPF 43 based on the engine intake air temperature TIN detected by the intake air temperature sensor 59, it is possible to perform an abnormality detection operation for the DPF even when the EGR feedback control is not being executed. I am trying. As described above, when the DPF 43 is damaged, regardless of the arrangement of the DPF and the supercharger,
The work of the supercharger increases and the supercharging pressure and temperature rise.
In this case, the supercharged air is cooled by the intercooler 26 by the time it reaches the engine surge tank, but the outlet temperature of the intercooler 26 also rises with the inlet temperature.
When the F43 is damaged, the temperature of the intake air reaching the surge tank 20 is always increased as compared with the case where the DPF 43 is normal.

When the EGR is performed, the intake air reaching the surge tank is mixed with the EGR gas and its temperature rises, but in this case as well, the temperature of the intake air before mixing rises. , Mixed intake (intake air and EGR
The temperature of the gas mixture with the gas also rises as compared with the case where the DPF 43 is normal. Therefore, by comparing the intake air temperature (reference intake air temperature) when the DPF 43 is normal under the same engine operating conditions with the actual intake air temperature, the DPF
It is possible to determine whether or not 43 is abnormal. However, in this case, since the discharge flow rate of the compressor of the supercharger changes when the intake air amount changes due to the opening degree of the intake throttle valve 27, the rotation speed of the supercharger and the discharge temperature of the compressor also change accordingly. Resulting in. Therefore, based on the intake air temperature, the DPF4
In order to detect the abnormality of No. 3, it is necessary to compare the reference intake air temperature and the actual intake air temperature in the engine operating state in which the engine intake air amount Gn is the same in addition to the engine speed NE and the fuel injection amount Q _fin. is there.

In this embodiment, when the DPF in the standard state is mounted on the engine and the intake air temperature in each operating state is measured in advance, the intake throttle valve is not operated during high load operation or low load operation without EGR feedback control. The intake air temperature is measured for each combination of the engine speed NE, the fuel injection amount Q _fin, and the intake air amount Gn by changing the opening degree 27 to change the intake air amount Gn. Similarly, in the region where the EGR feedback control is performed, the rotational speed NE and the fuel injection amount Q are similarly set.
_The intake air temperature is measured for each combination of _fin and intake air amount Gn, but since the engine intake air amount Gn is controlled to a value according to NE and Q _fin , if NE and Q _fin are determined, G
The value of n also becomes substantially fixed. In this embodiment,
The intake air temperature under each operating condition of the engine including the intake air amount Gn obtained above is stored in the ROM of the ECU 30 in the form of a numerical table using Gn, NE, and Q _fin as variables as the reference intake air temperature TINS. is there.

During engine operation, the ECU 30 reads from the numerical table the reference intake air temperature TINS in the same engine operating condition (engine rotational speed NE, fuel injection amount Q _fin , and intake air amount Gn) at that time. Then, it is compared with the actual intake air temperature TIN detected by the intake air temperature sensor 59. Then, even if the error is taken into consideration, the actual intake air temperature TIN
Is higher than the reference intake air temperature TINS, the DPF
It is determined that the engine intake air temperature has risen due to the damage of 43 and the reduction of the exhaust back pressure.

FIG. 4 shows the DPF 43 of this embodiment described above.
6 is a flowchart for specifically explaining the abnormality detection operation of FIG. This operation is performed as a routine executed by the ECU 30 at regular intervals. In the operation of FIG. 4, first, at step 401, the current engine speed NE and the fuel injection amount Q
_fin and the intake air amount Gn are read. Next, at step 403, it is judged if the engine is currently in steady operation. Whether or not the engine is in a steady operation is determined by, for example, the engine speed N between the time of the last execution of this operation and the current time.
E, fuel injection amount Q _fin , or intake air amount Gn is determined by whether it has changed by a predetermined amount or more, and NE, Q
_If either _fin or Gn changes by a predetermined amount or more, it is determined that the engine is not currently in steady operation. In this case, this operation ends immediately without performing the abnormality detection operation.

When the engine is not in steady operation, N
Since the changes in E, Q _fin , and Gn are large, the reference intake air amount temperature obtained from these changes _greatly , and the accuracy of the abnormality determination may decrease. Therefore, in the present embodiment, step 405 is performed only when the engine is in steady operation.
The following determination operation is performed. Step 40
In 5, the actual intake air temperature TIN of the engine is read from the intake air temperature sensor 59. Then, in step 407,
Using NE, Q _fin , and Gn read in step 401, the reference intake air temperature value TINS corresponding to the current engine operating state is read out from the reference intake air temperature table stored in the ROM of the ECU 30.

Next, at step 409, it is judged if the current intake air temperature TIN is higher than the reference intake air temperature TINS by a predetermined value γ or more. Step 4
If TIN ≧ TINS + γ at 09, that is, it is considered that the DPF 43 is damaged and the intake air temperature rises, so that the value of the abnormality flag XF is set to 1 at step 411. Here, γ is a value for preventing an erroneous determination due to a minute change in the intake air temperature TIN, and is set to a relatively small positive value. The flag XF has the first function
Embodiment (FIG. 3). Also,
When TIN <TINS + γ in step 409, the current intake air temperature is substantially equal to or lower than the reference intake air temperature, and therefore the DPF 43 is determined to be normal. In this case, the value of the flag XF is unchanged.

As described above, by executing the operation of FIG. 4, in the present embodiment, it is possible to easily and accurately detect the presence / absence of an abnormality in the DPF regardless of whether or not the EGR feedback control is performed. ing.

[0054]

According to the invention described in each claim, there is a common effect that the presence or absence of abnormality of the particulate filter can be detected easily and accurately. Further, according to the invention of claim 2, in addition to the common effect, there is an effect that it is possible to detect the presence or absence of abnormality of the particulate filter over a wide operating region of the engine.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an embodiment in which the present invention is applied to an automobile diesel engine.

FIG. 2 is a flowchart illustrating an example of an EGR valve opening feedback control operation based on an engine intake air amount.

FIG. 3 is a flowchart illustrating an embodiment of an abnormality detection operation of a particulate filter.

FIG. 4 is a flowchart illustrating an embodiment different from FIG. 3 of the abnormality detection operation of the particulate filter.

[Explanation of symbols]

1. Diesel engine body 3 ... Exhaust passage 23 ... EGR valve 30 ... Electronic control unit (ECU) 43 ... Particulate filter 59 ... Intake air temperature sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02M 25/07 570 F02M 25/07 570K (72) Inventor Takao Fukuma 1 Toyota-cho, Aichi Prefecture Toyota Motor Corporation ( 56) References JP-A-10-184343 (JP, A) JP-A-11-141405 (JP, A) JP-A-10-339216 (JP, A) JP-A-58-48764 (JP, A) JP-A Flat 8-170539 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 3/02 F02D 21/08 F02D 45/00 F02M 25/07

Claims (2)

(57) [Claims] 1. An abnormality detection device for a particulate filter, which detects whether or not a particulate filter arranged in an exhaust passage of an internal combustion engine is damaged, the EGR passage connecting an engine exhaust system and an engine intake system, By detecting the EGR valve disposed in the EGR passage and the engine intake air amount and controlling the EGR valve opening, the engine intake air amount is a target intake air amount that is predetermined according to the engine operating state. EGR control means for feedback-controlling the flow rate of the recirculated exhaust gas that recirculates from the exhaust system to the intake system through the EGR passage, and the recirculation exhaust gas by the EGR control means in a standard state where the particulate filter is in a normal state. Reference EGR valve that is the EGR valve opening in each engine operating state when the flow rate feedback control is being performed An EGR valve opening degree is detected during the feedback control of the recirculation exhaust gas flow rate by the EGR control means and the storage means that stores the opening degree in advance, and the detected actual EGR valve opening degree is stored in the storage means. An abnormality detection device for a particulate filter, comprising: determination means for determining that an abnormality has occurred in the particulate filter when the opening is larger than the reference EGR valve opening degree corresponding to the current operating state. 2. An abnormality detection device for a particulate filter, which detects whether or not a particulate filter arranged in an exhaust passage of an internal combustion engine is damaged, the exhaust turbine being arranged in an engine exhaust system and driven by an engine exhaust flow. And an exhaust supercharger equipped with a compressor arranged in the engine intake system to boost the engine intake air, an intake air temperature detecting means for detecting the engine intake air temperature, and a particulate filter in a normal state in a normal state, A storage unit that stores in advance a reference intake air temperature that is an intake air temperature in each engine operating state, and an engine intake air temperature detected by the intake air temperature detection unit during engine operation indicates the engine intake air amount stored in the storage unit. When the temperature is higher than the reference intake air temperature corresponding to the current engine operating state, including a determining means for determining that an abnormality has occurred in the particulate filter Abnormality detecting device of the particulate filter with.