JP2001152830A - Exhaust gas emission control apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and correctly judge a particulate correcting condition of a particulate filter(DPF). SOLUTION: An airflow meter for detecting intake air amount is disposed in an intake passage 2 of an engine 1, and a particulate filter(DPF) for collecting particulates in the exhaust gas is disposed in an exhaust passage 3. An engine electronic control unit(ECU) 30 detects engine rotating speed NE and a fuel injection amount Qfin, and a intake air amount Gn during operation of the engine, to judge the amount of the particulate collected by the particulate filter DPE by comparing a real intake air amount Gn, with an intake air amount Gnb which is stored beforehand in an operation of the same engine speed of rotation NE and the fuel injection amount Qfin in the reference condition in which particulate is not collected in the particulate filter DPE.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a particulate filter for trapping particulates (exhaust particulates) in the exhaust gas of the engine. The present invention relates to an exhaust gas purification device for an internal combustion engine that can accurately detect an increase in the amount of particulates.

[0002]

2. Description of the Related Art Exhaust gas from an internal combustion engine, particularly exhaust gas from a diesel engine, contains particulates mainly composed of carbon. There is known a technique in which a particulate filter (DPF) for trapping particulates is provided in an engine exhaust system in order to prevent the emission of these particulates into the atmosphere. However, when particulates are trapped in the DPF, the pressure loss of exhaust gas passing through the DPF increases as the trapping amount increases. For this reason, if the amount of particulates trapped in the DPF becomes excessive, so-called clogging of the DPF occurs, in which a decrease in engine output and deterioration in fuel efficiency due to an increase in exhaust back pressure of the engine cannot be ignored.

[0003] In order to solve the problem of clogging of the DPF, the amount of particulates trapped in the DPF is detected, and when the trapped amount reaches a certain amount, the exhaust gas temperature is raised. It is necessary to regenerate the DPF by burning and removing the particulates on the DPF. For this reason, various methods have been proposed for detecting the particulate collection state (particulate collection amount) of the DPF in order to perform an appropriate DPF regeneration operation.

In these methods, for example, a pressure sensor is provided in an exhaust passage on the upstream side of the DPF to detect an exhaust pressure (back pressure) on the upstream side of the DPF due to an increase in the amount of particulate matter trapped in the DPF, and the back pressure is set to a predetermined value. When the amount of particulates collected by the DPF increases, the method of determining that the amount of particulates collected by the DPF has increased (see, for example, Japanese Patent Application Laid-Open No. 60-153415). There is a method of judging that the collection amount has increased, and the like. Further, since particulates are mainly composed of conductive carbon particles, a method has been proposed in which the trapped amount of particulates is detected by a change in the electrical resistance of the DPF due to the trapped amount of the particulates (Japanese Patent Laid-Open No. Hei 8 (1994)). -68313). In this method, the filter element of the DPF is formed using a mesh made of a conductive material, and the electric resistance of the DPF is monitored during operation. When particulates are trapped in the DPF and clogging occurs, current flows through the particulates trapped in the gaps of the mesh, and the electric resistance of the entire mesh decreases.
Therefore, by measuring the electrical resistance of the DPF, the DP
The amount of trapped particulates of F can be detected.

[0005]

However, the conventional DP
Determination of particulate collection state of F or DPF
There are problems in any of the methods for determining clogging. For example,
In the method of detecting exhaust back pressure as disclosed in Japanese Patent Application Laid-Open No. 60-153415, it is necessary to install a new pressure sensor in the exhaust passage upstream of the DPF only for detecting the particulate collection state. There is a problem that the overall manufacturing cost increases. Further, since the exhaust back pressure greatly varies depending on the engine operating state or the pulsation of the exhaust pressure, it is difficult to accurately determine the particulate collection state of the DPF by the method of directly detecting the exhaust back pressure.

[0006] Further, since the amount of emitted particulate varies greatly depending on the operating state of the engine, a large error may occur in the method of determining the particulate collection state of the DPF based on the accumulated engine speed and traveling distance. .
Further, as disclosed in JP-A-8-68313, the DP
In the method of determining the particulate collection state based on the F electric resistance, it is necessary to change the material and structure of the DPF only for the determination of the collection state and to provide a separate means for detecting the electric resistance. However, there is a problem that the cost of the system greatly increases.

In view of the above problems, the present invention does not require a special device only for determining the particulate trapping state of the DPF, and can easily and accurately determine the particulate trapping state of the exhaust gas of an internal combustion engine. It is intended to provide a device.

[0008]

According to the first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine provided with a particulate filter disposed in an exhaust passage of the internal combustion engine for trapping particulates in exhaust gas. Operating state detecting means for detecting a current operating state of the engine, load parameter detecting means for detecting a load parameter related to a load state of the engine, and a particulate trapping amount of the particulate filter is predetermined. A storage unit for storing a relationship between the engine operating state and the load parameter in a reference state, which is a value, a value of the load parameter detected by the load parameter detecting unit during engine operation, and a value detected by the operating state detecting unit. By comparing the value of the load parameter in the reference state stored in the storage means corresponding to the current operation state, Exhaust purification apparatus for an internal combustion engine having a determining means for collecting particulates state of the particulate filter, is provided.

That is, according to the first aspect of the present invention, the storage means stores the reference amount in the reference state in which the amount of particulates collected by the particulate filter is a predetermined value (for example, in the non-collecting state in which the amount of particulates collected is zero). The relationship between the engine operating state and the value of the load parameter is stored. The determining means obtains the value of the load parameter in the reference state corresponding to the current engine operating state by using the value of the load parameter stored in the storage means. The particulate collection state of the particulate filter is determined by comparing the value of the parameter with the value of the parameter.

[0010] As the particulate trapping amount of the particulate filter increases, the exhaust back pressure of the engine increases, so that the engine output decreases as the particulate trapping amount increases. For this reason, the value of the load parameter related to the engine load greatly changes as the amount of trapped particulates increases even if the other operating conditions are the same. In the present invention, the determination means determines the value of the load parameter in the current operating state when the value of the load parameter in the reference state corresponding to the current operating state, that is, the particulate trapping amount of the particulate filter is a predetermined value. The trapping state of particulates is determined by comparing the value with the value of the actual load parameter.

For example, when the actual value of the load parameter in the current operating state greatly changes from the value of the load parameter in the reference state, the current particulate trapping amount of the particulate filter is equal to the reference amount. It can be determined that the amount differs greatly from the predetermined trapping amount in the state. Therefore, for example, if the predetermined particulate collection amount in the reference state is set to zero (non-collection state), if the current load parameter value greatly changes from that in the reference state, the particulate matter is not collected. It can be determined that the trapping amount has increased significantly. The storage means may store all values of the load parameter in each operating state of the engine in the reference state, or may store only the load parameter in a specific operating state in the reference state. Alternatively, the trapping amount may be determined when the operating state matches the specific operating state in actual operation.

According to the present invention, since parameters used for normal control, such as an engine intake air amount and a fuel injection amount, can be used as load parameters, it is necessary to newly provide a sensor for measuring load parameters. There is no.
Moreover, since the value of the load parameter is not affected by the pulsation of the exhaust pressure or the like, the trapping state can be accurately determined.

According to the second aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, wherein the load parameter detecting means detects an engine intake air amount as the load parameter.

That is, in the present invention, the intake air amount (flow rate) of the engine is used as the load parameter. When the trapping amount of the particulate filter increases and the back pressure of the engine exhaust system increases, the engine intake air amount decreases even if the engine operation state is the same (for example, the engine speed and the fuel injection amount are the same). Therefore, by comparing the engine intake air amount in the current operation state with the engine intake air amount in the same operation state in the reference state, the difference between the current collection amount of the particulate filter and the collection amount in the reference state, That is, the collection state of the particulates can be determined. Further, since the engine intake air amount is used for normal engine control, it is not necessary to provide a separate sensor or the like for determining the trapping amount of the particulate filter in the present invention.

According to the third aspect of the invention, the load parameter detecting means detects an engine fuel injection amount as the load parameter, and the determining means determines a current operating state detected by the operating state detecting means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a particulate collection state of the particulate filter is determined when the engine is in an idling operation.

That is, in the invention of claim 3, the engine fuel injection amount is used as the load parameter. If the trapping amount of the particulate filter increases and the back pressure of the engine exhaust system increases, the engine output decreases due to the increase of the exhaust back pressure. ), The fuel injection amount increases. Therefore, by comparing the fuel injection amount in the current operation state with the fuel injection amount in the same operation state in the reference state, the difference between the current collection amount of the particulate filter and the collection amount in the reference state, that is, The collection state of the curate can be determined. Further, since the fuel injection amount is constantly calculated by normal engine control, it is not necessary to provide a separate sensor or the like for determining the trapping amount of the particulate filter in the present invention.

Further, in particular, in an engine provided with an idle speed control device for controlling the engine idle speed to a constant value, the idle speed is controlled to be constant irrespective of the particulate collection state of the particulate filter. The same operation state as the state can be easily reproduced, and the determination of the particulate collection state of the particulate filter becomes easy.

According to the fourth aspect of the present invention, the judging means further detects the particulate collection state of the particulate filter when the current operation state detected by the operation state detection means is a deceleration operation. Claim 2
The exhaust gas purifying apparatus for an internal combustion engine according to (1) is provided.

That is, in the invention of claim 4, the determination of the particulate collection state is performed during the engine deceleration operation (for example, when the engine accelerator opening or the fuel injection amount is zero). In the case where the trapping state of particulates is determined using the engine intake air amount as a load parameter, for example, in an engine equipped with an EGR device that recirculates a part of the exhaust gas to the intake system, the engine is affected by the EGR gas amount. The intake air volume may change. However, during deceleration, the exhaust gas is not normally recirculated, and the EGR amount is set to zero. For this reason, in the present invention, it is possible to more accurately determine the particulate collection state by determining the particulate collection state during deceleration.

According to the fifth aspect of the invention, the internal combustion engine recirculates to the engine intake system through the EGR passage connecting the engine exhaust system and the engine intake system and the EGR passage arranged in the EGR passage. An EGR valve for controlling an exhaust gas flow rate, and an EGR valve for feedback-controlling the opening degree of the EGR valve so that the engine intake air amount becomes a predetermined value according to the engine operating state.
The exhaust gas purification device for an internal combustion engine according to claim 1, further comprising a control unit, wherein the load parameter detection unit detects the EGR valve opening as the load parameter.

In other words, according to the fifth aspect of the present invention, the engine is operated so that the amount of intake air becomes an amount determined according to the operating state of the engine.
EGR control means for performing feedback control of the GR gas amount is provided. In an engine equipped with such an EGR control means, when the exhaust back pressure increases and the intake air amount decreases, the EGR gas amount recirculated from the exhaust system to the intake system is reduced by the EGR control means. The engine intake air amount is maintained at an amount determined according to the operating state. For this reason, EGR
In an engine equipped with a control means, the engine intake air amount cannot be used as a load parameter for determining the particulate collection state of the particulate filter.

On the other hand, when the amount of trapped particulates by the particulate filter increases, the EGR control means controls the EG to maintain the engine intake air amount at a predetermined value.
The EGR gas amount is reduced by reducing the opening of the R valve. Therefore, other operating conditions (for example, engine speed and fuel injection amount)
However, under the same conditions, the EGR valve opening decreases as the amount of particulates collected by the particulate filter increases. Therefore, the EGR in the current operation state
By comparing the valve opening (or the EGR flow rate) with the EGR valve opening (or the flow rate) in the same operation state in the reference state, the current collection amount of the particulate filter and the collection amount in the reference state are obtained. The difference, that is, the particulate collection state can be determined. Also, EGR
Since the engine that performs feedback control of the gas amount always detects the opening degree of the EGR valve, it is not necessary to provide a separate sensor or the like in the present invention for determining the trapping amount of the particulate filter.

According to the present invention, the determination means includes means for burning and removing the particulates collected by the particulate filter, and the amount of the particulates collected by the particulate filter. Is determined to be greater than or equal to a predetermined amount, the particulate matter trapped in the particulate filter is burned, and after completion of combustion, the engine operating state and the E
6. The relationship between a GR valve opening degree and a new relationship between an engine operating state and an EGR valve opening degree in a reference state stored in the storage means, which is updated after the completion of the combustion, is updated. The present invention provides an exhaust gas purifying apparatus for an internal combustion engine.

That is, in the invention according to claim 6, when the determination means determines that the particulate trapping amount of the particulate filter increases and reaches a predetermined value, the fuel injection amount of the engine is increased, for example. The particulates on the particulate filter are burned by means such as raising the exhaust gas temperature. As a result, the particulate filter originally returns to the state where the amount of collected particulates is zero (non-collection state). However, in addition to particulates mainly composed of carbon, engine exhaust contains fine particles (ash) mainly composed of an inorganic component such as calcium sulfate generated by combustion of lubricating oil. This ash is also trapped in the particulate filter in the same manner as the particulates, but unlike the particulates containing carbon as a main component, the ash does not burn. It cannot be removed by the method. For this reason, the amount of ash collected by the particulate filter gradually increases with the operation time. As described above, since the amount of ash collected by the particulate filter gradually increases with the operating time, the pressure loss of the particulate filter after burning and removing the particulate also gradually increases with the cumulative operating time of the engine. Become like Therefore, if the amount of ash actually deposited is different, the pressure loss of the particulate filter becomes a different value even if the amount of trapped particulate of the particulate filter is the same. By comparing the value of the load parameter with the current value of the load parameter when a predetermined amount of particulates is collected, the particulate collection state (collection amount) of the particulate filter can be accurately determined. May not be able to do so.

According to the present invention, each time the particulate matter collected by the particulate filter is burned, the state after combustion, that is, the state where only the ash is deposited on the particulate filter and the particulate matter is not collected, is determined. As a new reference state, a relation between the operating state and the EGR valve opening is obtained, and the relation in the new reference state is stored in the storage means. That is, in the present invention, each time the particulate combustion is performed, the operating state in the reference state and the E
The relationship with the GR valve opening is learned and stored. This relationship in the new reference state is based on the pressure loss of the particulate filter corresponding to the current ash accumulation amount. In the present invention, the EG in this new reference state is
By comparing the R valve opening with the actual EGR valve opening, it is possible to accurately determine the particulate collection state of the particulate filter.

According to the seventh aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine including a particulate filter disposed in an exhaust passage of the internal combustion engine for collecting particulates in exhaust gas. The first operation condition
Operating state changing means for changing the operating state of the engine to a predetermined second operating state, load parameter detecting means for detecting a load parameter related to the load state of the engine, and a particulate trapping amount of the particulate filter. Storage means for storing a change amount of the value of the load parameter before and after the change from the first operating state to the second operating state in a reference state which is a predetermined value; The amount of change in the load parameter before and after the change detected by the load parameter detecting means when the means changes the engine operating state from the first operating state to the second operating state, and the storage means stores A particulate collection state of the particulate filter is determined by comparing a change amount of the load parameter in a reference state. Exhaust purification apparatus for an internal combustion engine having a determining means, is provided.

That is, according to the present invention, a predetermined change is given to the operating state under the actual condition under the actual condition of the load parameter before and after the predetermined change in the operating state of the engine in the reference state. Then, the particulate collection state of the particulate filter is determined by comparing the change amount of the load parameter before and after the change. If the pressure loss of the particulate filter is different, the amount of change in the load parameter before and after the change in the operating state will also be different. In the present invention, it is possible to accurately determine the particulate collection state of the particulate filter by comparing the change amount of the load parameter when a predetermined change is given to the operation state with the change amount in the reference state. I have.

According to the invention described in claim 8, the operating state changing means includes exhaust throttle means for reducing an engine exhaust flow rate, and the degree of exhaust throttle by the exhaust throttle means is changed from a first state to a predetermined state. 2. The engine operation state is changed from the first operation state to the second operation state by changing the state to the second state, and the load parameter detection means detects an intake air amount of the engine as the load parameter. 7. An exhaust gas purification device for an internal combustion engine according to 7 is provided.

That is, in the invention of claim 8, the operating state is changed from the first state to the second state by performing a constant exhaust throttle using the exhaust throttle means. As the exhaust throttle means, for example, an exhaust throttle valve provided in an engine exhaust passage can be used. When the engine exhaust is throttled by the exhaust throttle means, the resistance of the exhaust passage increases and the exhaust back pressure increases. However, in the state where particulates are collected by the particulate filter, the exhaust back pressure is originally high, so even if the exhaust is throttled, the increase in the back pressure will be greater than when no particulates are collected. Becomes smaller. Further, when the exhaust throttle is performed, the engine intake air amount also changes (decreases) with an increase in the exhaust back pressure, but the change width becomes smaller as the amount of the particulate matter collected by the particulate filter increases. In particular, in an engine equipped with an exhaust supercharger such as a turbocharger, if the exhaust throttle is performed by closing the exhaust throttle valve in a state where particulates are not collected in the particulate filter, the exhaust back pressure will increase. In addition, since the work of the turbocharger is reduced, the amount of intake air is significantly reduced. On the other hand, in the state where the particulates are collected by the particulate filter, the intake air amount is reduced due to the increase of the back pressure and the reduction of the work of the supercharger even when the exhaust throttle is not performed. Therefore, even if the exhaust throttle is performed, the reduction width of the intake air amount is relatively small. Therefore, by comparing the change width of the intake air amount before and after the exhaust throttle with the change width of the reference state, it is possible to accurately determine the particulate collection state of the particulate filter.

According to the ninth aspect of the present invention, the internal combustion engine includes a turbocharger provided in an engine exhaust system,
An EGR passage that connects the engine exhaust system and the engine intake system, an EGR valve that is arranged in the EGR passage, and controls an exhaust gas flow rate that returns to the engine intake system through the EGR passage, and an EGR passage that is arranged in the EGR passage, An EGR cooler for cooling the exhaust gas flowing back to the engine intake air amount system, and the EGR cooler so that the engine intake air amount becomes a predetermined value according to the engine operating state.
EGR control means for performing feedback control of a GR valve opening degree, wherein the load parameter detection means detects an engine intake pipe pressure as the load parameter, and the determination means detects the load parameter detection means during operation of the engine. By comparing the measured intake pipe pressure with the value of the intake pipe pressure in the reference state stored in the storage means corresponding to the current operation state detected by the operation state detection means, the EGR flow path of the EGR cooler is compared. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a particulate collection state of the particulate filter is determined regardless of whether clogging of the particulate filter occurs.

That is, according to the ninth aspect of the present invention, the EGR passage is provided with an EGR cooler. Since the exhaust gas passes through the EGR cooler, clogging may occur due to accumulation of particulates in the exhaust gas, similarly to the particulate filter. However, in an engine equipped with EGR control means for performing feedback control of the EGR valve opening so that the engine intake air amount becomes a predetermined value according to the operating state, the EGR gas is supplied so that the engine intake air amount becomes a predetermined amount. Since the amount is feedback controlled, even if a clogging occurs in the EGR cooler or the particulate filter, the intake air amount does not change and it is difficult to determine the clogging based on the intake air amount. Further, when the EGR cooler is clogged, the amount of EGR gas recirculated to the intake system decreases and the amount of engine intake air increases, so the EGR control means increases the EGR valve opening to maintain the intake air amount at a predetermined value. try to. Further, when the amount of particulates accumulated in the particulate filter increases, the engine intake air amount decreases due to the increase in exhaust back pressure. Therefore, the EGR control means reduces the EGR valve opening to maintain the intake air amount at a predetermined value. I do. That is, E
The opening degree of the GR valve is adversely affected by clogging of the EGR cooler and clogging of the particulate filter. Therefore, in an engine including both an EGR valve and an EGR cooler, it is not possible to accurately determine whether the particulate filter or the EGR cooler is clogged based on the EGR valve opening.

On the other hand, the engine intake pipe pressure is affected only by the particulate collection state of the particulate filter, and is not affected by clogging of the EGR cooler. That is, when the amount of particulates collected by the particulate filter increases, the back pressure of the exhaust supercharger increases, so that the turbocharger rotation speed decreases and the supercharger discharge pressure (supercharge pressure, that is, the intake pipe pressure) increases. descend. On the other hand, when the EGR cooler is clogged, the engine intake air amount is maintained at a predetermined amount by the EGR control means. Therefore, unless the back pressure of the supercharger is increased, the supercharger speed is reduced. It does not decrease, and the intake pipe pressure does not decrease. In the present invention, the engine intake pipe pressure is used as a load parameter, and the actual intake pipe pressure is compared with the intake pipe pressure corresponding to the same operation state in the reference state, thereby affecting the presence or absence of the clogging of the EGR cooler. Accurately, the particulate collection state of the particulate filter is determined without receiving the particulate filter.

By accurately determining the trapping state of the particulate filter as described above, it is possible to accurately determine whether the EGR cooler is clogged. For example, when it is determined that the trapping amount of the particulate filter is increased by the above-described method, and when the EGR valve opening is not so much lower than the reference state, the EGR cooler may be clogged. It can be determined that it has occurred.

[0034]

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. 1, reference numeral 1 denotes a diesel engine main body, 2 denotes an intake passage of the engine 1, and 20 denotes an intake passage 2.
Is an intake branch pipe connecting the surge tank 20 and the intake port of each cylinder. In the present embodiment, the intake passage 2 is provided with an intake throttle valve 27 for reducing the flow rate of intake air flowing through the intake passage 2 and an intercooler 26 for cooling intake air. The intake throttle valve 27 includes an actuator 27a of an appropriate type such as a solenoid or a vacuum actuator, and takes an opening in accordance with a control signal from an electronic control unit (ECU) 30 described later. In the present embodiment, the intake throttle valve 27 reduces the intake pressure, for example, when the engine is running at a low speed, so that an EGR passage
In addition to being used to increase the amount of exhaust gas (EGR gas) recirculated to the surge tank 20 through the fuel tank 3, the intake air is used when burning the particulates collected by the particulate filter 43 (regenerating the particulate filter 43). Is used to raise the exhaust temperature.

In FIG. 1, reference numeral 25 denotes an air flow meter provided near the intake port of the intake passage 2. In the present embodiment, an air flow meter 25 such as a hot wire flow meter that can directly measure the weight flow rate of the intake air flowing through the intake passage 2 is used. The air flowing into the intake passage 2 passes through an air flow meter 25, is pressurized by a compressor of an exhaust supercharger (turbocharger) 35, is cooled by an intercooler 26 provided in the intake passage 2, and It is sucked into each cylinder via 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) for storing high-pressure fuel
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 from the common rail 115 into each cylinder via each fuel injection valve 111. In FIG. 1, reference numeral 31 denotes an exhaust manifold connecting the exhaust port of each cylinder and the exhaust passage 3, and reference numeral 35 denotes a turbocharger.
The turbocharger 35 includes an exhaust turbine driven by exhaust gas in the exhaust passage 3 and an intake compressor driven by the exhaust turbine. In the present embodiment,
A variable nozzle 35a is provided at the exhaust inlet of the exhaust turbine. The variable nozzle 35a is a nozzle whose opening area can be changed. For example, when the exhaust flow rate of the engine is low and the load is low, the variable nozzle 35a narrows the nozzle opening area to increase the flow rate of exhaust gas flowing into the exhaust turbine. . By squeezing the variable nozzle 35a during low engine load operation,
Since the rotation speed of the exhaust turbine is kept high, a decrease in compressor discharge pressure (supercharging pressure) is prevented. When the variable nozzle 35a is throttled, the exhaust flow path resistance increases, and the exhaust back pressure of the engine 1 increases.

In this embodiment, the turbocharger 3
An exhaust throttle valve 37 for reducing the flow rate of exhaust gas flowing through the exhaust passage 3 is disposed on the exhaust passage 3 on the downstream side 5. The exhaust throttle valve 37 includes an actuator 37a similar to the intake throttle valve 27, and takes an opening degree according to a control signal from the ECU 30. In the present embodiment, the exhaust throttle valve 37 is used when adjusting the EGR gas amount and regenerating the particulate filter 43 to raise the exhaust gas temperature, similarly to the intake throttle valve 27. The exhaust throttle valve 37 can be used when restricting exhaust gas to determine the particulate collection state of the particulate filter 43, as described in an embodiment described later.

Further, in this embodiment, an EGR device for recirculating a part of the engine exhaust gas to the intake system is provided. E
The GR device includes an exhaust manifold 31 and an intake surge tank 2
0 and an EGR passage 33 communicating with the EGR passage 33
An EGR valve 23 disposed above and an EGR cooler 45 provided in an EGR passage upstream of the EGR valve 23 are provided. The EGR valve 23 includes an actuator (not shown), and takes an opening degree in accordance with a control signal from the ECU 30.
The flow rate of the EGR gas that flows back to the intake surge tank 20 through the GR passage 33 is controlled. In the present embodiment, a relatively large amount of E in a wide operating range from a low load range to a high load range.
The EGR valve 23 is controlled to recirculate the GR gas. For this reason, in this embodiment, the intake air drawn into each cylinder contains a relatively large amount of EGR gas. E
Since GR gas is high-temperature exhaust gas discharged from a cylinder,
When a large amount of EGR gas is recirculated to the intake air, the intake air temperature rises, and the intake volume efficiency of the engine decreases. In the present embodiment, in order to prevent this, EGR
The EGR passage 33 upstream of the valve 23 has a water-cooled or air-cooled EGR passage.
A GR cooler 45 is provided. In the present embodiment, E
By using the GR cooler 45 to lower the temperature of the EGR gas recirculated to the intake system, a large amount of EGR gas can be recirculated without lowering the intake volume efficiency of the engine.

In FIG. 1, reference numeral 30 denotes an electronic control unit (ECU) of the engine 1. ECU 3 of the present embodiment
Reference numeral 0 denotes a microcomputer having a known configuration, in which a CPU, a RAM, a ROM, an input port, and an output port are mutually connected 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 the present embodiment, functions as a determination unit that determines the trapping state of the DPF 43.

In order to perform these controls, a signal corresponding to the engine speed NE is input to an input port of the ECU 30 from a speed sensor 55 disposed near the crankshaft of the engine 1, and an air flow meter 25. A signal corresponding to the engine intake air amount Gn is output from the accelerator opening sensor 57 disposed near the engine accelerator pedal to a signal corresponding to the accelerator pedal depression amount (accelerator opening) ACCP of the driver and the EGR valve 23. A signal VEG representing the EGR valve opening from the disposed EGR valve opening sensor 51 and a signal representing the intake pipe pressure PM from the intake pressure sensor 59 disposed in the intake surge tank 20 are input.

The output port of the ECU 30 is connected to a fuel injection valve 11 of the engine 1 through a fuel injection circuit (not shown).
1 and controls the fuel injection amount and fuel injection timing from the fuel injection valve 111. An output port of the ECU 30 is connected to actuators of the EGR valve 23, the intake throttle valve 27, and the exhaust throttle valve 37 and a variable nozzle 35a of the turbocharger 35 via a drive circuit (not shown), and controls the respective valve openings. I have.

In this embodiment, a well-known exhaust gas purifying catalyst 41 such as a three-way catalyst and a particulate filter (DPF) 4 are disposed downstream of the exhaust throttle valve in the exhaust passage 3.
3 are arranged. The DPF 43 is made of, for example, a metal mesh or a ceramic porous filter, and collects particulates in exhaust gas. In the present embodiment, the DPF 43
Any known type of particulate filter can be used.

As described above, the particulates contained in the exhaust gas during the operation of the engine are collected by the DPF 43, and are gradually reduced.
The pressure loss of the exhaust flowing through the PF 43 increases. For this reason, D
When the amount of particulate matter trapped by the PF increases, the exhaust pressure in the exhaust manifold 31 increases, and an increase in back pressure causes a decrease in engine output, an increase in fuel consumption, and the like. For this reason, the particulate collection state of the DPF 43 is monitored, and the particulate matter collected by the DPF 43 is burned before the amount of particulate collection increases and the exhaust back pressure of the engine exceeds an allowable value. Need to be removed. D
An increase in back pressure due to an increase in the amount of particulates collected by the PF 43 can be determined theoretically by detecting the exhaust pressure in the exhaust manifold 31. However, as described above, the exhaust pressure fluctuates not only in accordance with the engine operating state, but also constantly fluctuates due to exhaust pulsation. For this reason, it is actually difficult to accurately determine the particulate collection state of the DPF 43 based on the exhaust pressure.
Also, the exhaust pressure of the engine is not used for normal engine control. For this reason, based on the exhaust pressure, the DPF 43
In order to detect the particulate collection state, it is necessary to dispose an exhaust pressure sensor used only for the particulate collection state determination in the exhaust manifold 31.
This results in an increase in the manufacturing cost of the entire engine.

However, when the amount of trapped particulates increases and the exhaust back pressure of the engine increases, the engine output decreases. For this reason, when the amount of trapped particulates increases, among the parameters indicating the operating state of the engine, the values of the parameters related to the load change even if the values of the other operating parameters are kept the same. Moreover,
Since the operation parameters related to the load are used for normal engine control, they can be detected without adding any special sensor or the like. Therefore, for example, the operating parameters representing the operating state of the engine and the load parameters related to the engine load are selected in advance, and the DPF 43 is selected.
The engine is operated in a new state in which no particulate matter is collected, and the values of the operation parameters and the load parameters are measured, and the values of these operation parameters are stored as the values of the operation parameters in the reference state. deep. Then, the value of the load parameter in the reference state is obtained from the value of the operation parameter measured in the actual operation, and the value of the load parameter measured in the actual operation greatly changes from the value of the load parameter in the reference state. In such a case, it can be determined that an increase in the engine back pressure, that is, an increase in the particulate collection amount of the DPF 43 has occurred. As typical operating parameters related to the engine load, for example, an engine intake air amount, a fuel injection amount, an EGR amount, and the like are used.

In the embodiment of the present invention described below, by using the load parameter of the engine for the determination of the particulate collection state of the DPF 43 as described above, a sensor or the like used only for the determination of the collection state is used. Without the provision, the particulate collection state of the DPF 43 is accurately determined by a simple method. Hereinafter, some embodiments of the particulate collection state determination operation of the present invention will be described.

(1) First Embodiment In this embodiment, the particulate collection state of the DPF 43 is determined using the engine intake air amount (weight flow rate) Gn among the load parameters. When the amount of trapped particulates of the DPF 43 increases, the exhaust back pressure increases, so that the amount of burned gas remaining in the cylinder during the exhaust stroke increases. Therefore, the amount of air taken into the cylinder decreases.
In the present embodiment, for example, the engine speed NE and the fuel injection amount Q _fin (or the accelerator pedal depression amount (accelerator opening) ACCP by the driver) are used as operation parameters representing the operation state of the engine. Normally, in a diesel engine, the engine speed NE and the accelerator opening ACCP are detected, and the fuel injection amount _Qfin is calculated from a predetermined relationship based on these values. That is, NE, ACCP, Q
_fin is a parameter used for normal engine control. Further, in the present embodiment, as will be described later, EGR that performs feedback control of the EGR gas amount so that the engine intake air amount Gn becomes a value determined according to the engine operating state.
Perform control. For this purpose, an air flow meter 25 for detecting an engine intake air amount is provided. Therefore, DP
It is not necessary to provide a separate sensor or the like in order to determine the particulate collection state in F43.

In the present embodiment, the engine 1 is set in a reference state in which the DPF 43 has not previously collected particulates.
Is operated in different operation states, and NE,
Obtained relation between Q _{fi n} and Gn, are stores these relationships in the ROM of the ECU 30. Then, during the actual operation, the values of the rotational speed NE, the fuel injection amount Q _fin , and the intake air amount Gn are detected, and the ECU 3 uses the detected values of NE and Q _fin.
The value Gnb of the intake air amount in the reference state corresponding to these values is calculated from the relationship stored in 0. Then, the actual intake air amount Gn and the intake air amount Gnb in the reference state
Is compared, the particulate collection state of the DPF 43 is determined. That, NE, if Q _fin is kept the same, the exhaust back pressure of the engine increases as the particulate collection amount of DPF43 is increased, the intake air amount Gn decreases as the amount of collection increases. Therefore, when the value of the actual intake air amount Gn is lower than the intake air amount Gnb in the reference state by the predetermined value ΔGn or more, it can be determined that the particulate collection amount of the DPF 43 has exceeded the predetermined amount.

FIG. 2 is a flowchart for explaining the DPF trapping amount determination operation of the present embodiment. This operation is performed by ECU3
This is performed by a routine executed at regular intervals of 0. In FIG. 2, when the operation starts, step 20 is executed.
1, the rotation speed sensor 55 and the air flow meter 25
, The engine speed NE, the intake air amount Gn, and the engine fuel injection amount Q calculated by a fuel injection amount calculation operation (not shown) separately executed by the ECU 30.
_fin is read respectively.

In step 203, it is determined whether or not the recirculation of the EGR gas is currently stopped (cut). If the EGR cut is not performed in step 203, the current operation is terminated without executing step 205 and subsequent steps. That is, in this case, the collection amount determination of the DPF is not performed. In the present embodiment, as will be described later, an EG that controls the EGR gas amount so that the engine intake air amount Gn becomes an amount determined according to the operating state.
R control is performed. Therefore, during execution of the EGR control, the DP
Regardless of the collection amount of F43, the intake air amount Gn is controlled to a value determined in accordance with the operation state, so that the value of Gn is
The amount of PF collected cannot be determined. For this reason, in this embodiment, the collection amount determination of the DPF is performed under the condition that the EGR is stopped (cut), such as during a high load operation. It should be noted that whether or not the EGR is being cut is determined by the EGR
The determination is made based on whether or not the valve opening is zero.

If it is determined in step 203 that the EGR is currently being cut, then in step 205, it is determined whether or not the engine is currently operating normally. Whether or not the engine is in steady operation is determined, for example, by determining the value of the engine speed NE and the fuel injection amount _Qfin read in step 201,
The determination is made based on whether or not a change from the value at the time of executing the last operation is within a predetermined value. If the engine is not currently operating in a steady state, the values of Gn, NE, and _Qfin may not be stable and erroneous determination may occur. Therefore, also in this case, the current operation is immediately terminated without executing the determination of step 207 and subsequent steps.

If it is determined in step 205 that the current operation state is a steady operation, then in step 207, the EC is calculated using the values of NE and _Qfin read in step 201.
NE and Q in the reference state stored in the ROM of U30
The intake air amount Gnb in the reference state is calculated based on the relationship between _fin and Gn. Then, in step 209,
It is determined whether or not the value of the difference (Gnb-Gn) between the calculated intake air amount Gnb in the reference state and the actual intake air amount Gn is larger than a predetermined value ΔGn. Here, ΔGn is the difference between Gnb and Gn when the amount of particulate matter trapped in the DPF increases to the maximum allowable amount, and differs depending on the type of DPF used.
Is a value set based on an experiment using.

If Gnb-Gn> ΔGn in step 209, that is, it is considered that the trapped amount of DPF increases and reaches the maximum allowable amount. Therefore, in this case, the process proceeds to step 211, where the value of the trapping amount alarm flag XDPF is set to 1, the value of the DPF regeneration operation execution flag XR is set to 1, and the operation ends. In step 209, Gnb-
If Gn ≦ ΔGn, that is, since the amount of trapped particulates in the DPF is within the allowable range, the flag XD
This operation ends without changing the values of PF and XR.

In this embodiment, the alarm flag XDPF
Is set to 1, a warning lamp arranged near the driver's seat is turned on by a routine (not shown) separately executed by the ECU 30 to notify the driver that the collection amount of DPF is increasing. When the value of the reproduction flag XR is set to 1, a reproduction operation (not shown) separately executed by the ECU 30 is started. In the regeneration operation, one or both of the intake throttle valve 27 and the exhaust throttle valve 37 are closed to a predetermined opening to reduce the intake air amount of the engine 1 and increase the fuel injection amount from the fuel injection valve 111. Is done.

As a result, the exhaust gas temperature of the engine rises, and the particulates collected by the DPF 43 burn. When a predetermined time has elapsed after the start of the regeneration operation and it is determined that the entire amount of the particulates collected in the DPF 43 has burned, the regeneration operation is stopped, and the intake throttle valve 27 and the exhaust throttle valve 37 are connected to the normal state. While returning to the opening degree, the increase in the fuel injection amount of the engine is stopped. The alarm flag XDPF and the regeneration operation execution flag XR
Are reset to zero when the reproduction operation ends.

Further, in this embodiment, the engine 1 is an EGR
Since the determination of the particulate collection state of the DPF is performed after the operation is stopped under the condition of stopping the operation, the frequency at which the collection amount determination is performed may decrease depending on the operation situation. Therefore, instead of waiting for the engine 1 to be driven under the condition of stopping the EGR, the EGR is forcibly stopped at regular time intervals or at regular traveling distances to perform the above-described collection amount determination operation. It is also possible to prevent the collection frequency determination operation execution frequency from decreasing.

(2) Second Embodiment Next, a second embodiment of the present invention will be described. In the present embodiment, it is determined collection amount using the fuel injection quantity Q _fin instead of the intake air amount Gn as the load parameter. The trapping amount determination operation is performed only when the engine is idling.

When the amount of particulates collected by the DPF increases, the exhaust back pressure of the engine increases. For this reason, the output torque of the engine decreases due to the increase in the exhaust resistance, and the engine speed decreases if the other operating conditions are the same. For this reason, in order to maintain the same engine speed when the trapping amount is increased when the trapping amount is small (when no trapping is performed), the engine needs to perform more work than when the trapping is not performed. is there. Therefore, when the rotation speed is kept the same, the fuel injection amount of the engine increases as the trapping amount increases when the trapping amount of the DPF increases, compared to when the DPF does not trap.

In this embodiment, the ECU 30 performs idle speed control (ISC) for controlling the fuel injection amount so that the engine speed becomes a predetermined idle speed during the idle operation of the engine. For this reason, during idling operation, the engine speed is fixed at a constant value,
The fuel injection amount is controlled to a value determined according to the change in the engine load during idling, that is, the particulate collection state of the DPF 43. Therefore, if the fuel injection amount during idle operation in the reference state is measured in advance, the DPF 43 can be calculated from the fuel injection amount during actual idle operation.
Can be determined. Further, during the execution of the idle speed control, the engine speed is controlled to the idle speed and the fluctuation of the engine speed is reduced, so that the variation of the fuel injection amount is reduced, and the determination of the trapping state based on the fuel injection amount is performed. The accuracy of the judgment at the time of performing is improved. For this reason, in the present embodiment, the collection amount determination based on the fuel injection amount is performed during the idle operation of the engine.

FIG. 3 is a flowchart for explaining the trapping state determination operation of this embodiment. This operation is performed by a routine executed by the ECU 30 at regular intervals.
When the operation starts in FIG. 3, in step 301, it is determined whether or not the idle speed control (ISC) is currently being performed. In the present embodiment, if the idle control is not currently being performed, the current operation is immediately terminated. If the ISC is currently being performed, the process proceeds to step 303, where the separately calculated value of the fuel injection amount _Qfin is read, and in step 305,
It determines whether the increased predetermined amount Delta] Q _fin or the fuel injection amount Q _Finb during idle operation in the reference state value of Q _fin is previously stored.

In step 305, when Q _fin is larger than Q _finb by more than ΔQ _fin (Q _fin −Q _finb
> ΔQ _fin ), it is determined that the amount of particulates collected by the DPF 43 exceeds the maximum allowable value, and step 307 is executed.
And 309, the collection amount alarm flags XDPF and D, respectively.
The value of the PF regeneration operation execution flag XR is set to 1, and the current operation ends. In step 305, Q _fin −
If Q _finb ≦ ΔQ _fin , the trapping amount is within the allowable range, and the current operation ends without changing the values of the flags XDPF and XR.

The determination value ΔQ _{fin for} increasing the fuel injection amount is:
This is a difference between the fuel injection amount in the idling operation when the trapping amount of the DPF 43 reaches the maximum allowable amount and the fuel injection amount in the reference state. The functions of the flags XDPF and XR are the same as those of the first embodiment.

(3) Third Embodiment In this embodiment, the collection amount is determined using the engine intake air amount Gn as a load parameter. The trapping amount determination operation is executed only when the engine is decelerated, that is, when the accelerator opening is zero (when fuel injection is stopped). As described above, when the collection amount determination is performed using the intake air amount Gn as the load parameter, an accurate determination cannot be made when the EGR feedback control of the intake air amount is performed. However, since the EGR is generally stopped when the engine is decelerated, the intake air amount Gn becomes a value corresponding to the particulate collection state of the DPF. Further, at the time of deceleration, the fuel injection of the engine is stopped (fuel injection cut), so that the intake air amount Gn is a function of only the engine speed NE. Therefore, when determining the trapping amount during deceleration,
The fuel injection amount as the operating state parameter is always a constant value (zero), and the operating state parameter used is only the engine speed NE. That is, by determining the trapping state at the time of deceleration, the relationship between the operating state parameters and the load parameters stored in advance becomes a one-dimensional numerical map of only the rotational speed NE and the intake air amount Gn. Therefore, there is an advantage that the relationship between the operating state parameter and the load parameter in the reference state stored in advance is simplified, and the calculation of the value of the load parameter in the reference state at the time of the trapping amount determination is facilitated.

FIG. 4 is a flowchart for explaining the collection amount determination operation of this embodiment. This operation is performed by a routine executed by the ECU 30 at regular intervals.
When the operation is started in FIG. 4, in step 401, the engine speed NE and the intake air amount Gn are read from the engine speed sensor 55 and the air flow meter 25, respectively. In step 403, it is determined whether or not the current value of the fuel injection amount _Qfin calculated by the fuel injection amount calculation operation separately executed by the ECU 30 is zero. If Q _fin = 0 in step 403, that is, since the engine 1 is in a deceleration operation state in which fuel injection is currently cut, the collection amount determination operation in step 405 and subsequent steps is performed.

In step 405, the relationship between the engine speed NE and the intake air amount Gnb during the engine deceleration operation in the reference state (a state in which the amount of trapped particulates of the DPF 43 is zero) previously determined by experiments or the like is separately determined. Based on this, the intake air amount Gnb in the reference state corresponding to the current rotational speed NE read in step 401 is calculated. Then, in steps 407 to 411, Gnb-
G is determined based on whether the value of Gn is greater than a predetermined value ΔGn.
The particulate collection state of the PF 43 is determined, and if the collection amount is determined to be larger than the maximum allowable amount, the values of the collection amount alarm flag XDPF and the DPF regeneration operation execution flag XR are set to 1. To end this operation. The operations in steps 407 to 411 are the same as the operations in steps 209 to 213 in FIG.

(4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described. In the present embodiment, the opening degree of the EGR valve 23 is used as a load parameter. The determination of the trapping amount is performed during the execution of the EGR feedback control. In the present embodiment, EG is set so that the intake air amount Gn of the engine becomes a value determined according to the operating state.
EGR feedback control for performing feedback control of the R gas amount is performed. For this reason, the EGR gas amount changes according to the engine load state, and if the engine load state is originally constant, the EGR gas amount will be the same,
The opening degree of the EGR valve for adjusting the EGR gas amount becomes the same.

However, when the amount of trapped particulates in the DPF 43 increases, the EGR valve 2 can be operated even in the same operation state.
The opening degree of No. 3 changes. When the amount of trapped particulates in the DPF 43 increases, the exhaust back pressure in the exhaust manifold 31 increases. Therefore, the exhaust resistance increases and the engine intake air amount decreases. Therefore, when the EGR feedback control is being performed, the amount of EGR gas is reduced to adjust the intake air amount to a predetermined value, and the EGR valve opening is reduced. Further, when the exhaust pressure in the exhaust manifold 31 increases, the exhaust gas flow through the EGR valve increases even with the same EGR valve opening, so that the EGR valve opening is further reduced. Therefore, even if other operating conditions are the same, EGR
When the feedback control is performed, the EGR valve opening is DPF
43 decreases as the collection amount increases.
In the present embodiment, focusing on this point, the DPF 43 is determined based on the EGR valve 23 opening during the EGR feedback control.
Is determined. Thus, the DPF is determined based on the opening of the EGR valve 23.
43, the collection state is determined.
Since it is possible to accurately determine the collection state during the execution of the GR feedback control, it is possible to greatly increase the execution frequency of the determination of the collection state.

FIG. 5 is a flowchart for explaining the EGR feedback control operation in this embodiment, and FIG.
It is a flowchart explaining the DPF collection amount determination operation based on the EGR valve opening degree performed during the GR feedback control. 5 and 6 are performed by a routine executed by the ECU 30 at regular intervals. First, the EGR feedback control operation will be described.

In the EGR feedback control operation of FIG. 5, first, at step 501, the engine speed NE and the intake air amount G are obtained from the speed sensor 55 and the air flow meter 25.
n is read, and the value of the engine fuel injection amount _Qfin calculated by the fuel injection amount calculation operation separately executed by the ECU 30 is read. Then, in step 503, the value of the target intake air quantity Gnt on the basis of the rotational speed NE and the fuel injection amount Q _fin read by the is calculated.

The target intake air amount Gnt is determined by the EGR rate (the ratio of EGR gas in the intake air taken into the engine, that is, (EGR gas amount) / (EGR gas amount + intake air amount Gn)). The intake air amount is set in advance for each operation state so as to have a predetermined value determined according to the following. That is, it is preferable to supply a large amount of EGR gas as an inert gas to the engine combustion chamber in order to lower the combustion temperature of the engine and reduce NO _x (nitrogen oxide) of the engine. However, when the amount of EGR gas supplied to the combustion chamber becomes excessive, the combustion state of the engine deteriorates and the output decreases. Therefore, in the present embodiment, the optimum EGR rate is experimentally set in advance according to the engine operating state, and the ratio of the intake air amount Gn to the EGR gas amount is set to the optimum EGR rate. The amount is set as the target intake air amount Gnt. That is, when the engine operation state such as the engine speed NE and the fuel injection amount _Qfin is determined, the total intake amount (EGR gas amount + intake air amount Gn) drawn into the engine combustion chamber is uniquely determined. Thus, NE, by setting in advance the optimum EGR ratio according to the operating conditions such as Q _fin, may uniquely determined intake air amount Gnt required to obtain the EGR ratio. In this embodiment, by calculating the target intake air amount Gnt for optimal EGR rate for the engine operating condition determined in advance from the NE, Q _fin, during engine operation, the actual intake air amount Gn is this Target intake air amount Gnt
The EGR valve 23 performs feedback control to adjust the actual EGR amount by performing feedback control so that the EGR valve 23 coincides with the following. Thus, the engine is always to be operated in an optimal EGR rate, it is possible to reduce the generation of no NO _X causing a reduction in the deterioration and the output of the combustion.

[0070] In this embodiment, the value of the target intake air amount Gnt is NE, Yes stored in ECU30 the ROM in the form of a numerical table using the Q _fin as a parameter, the current read in step 501 in FIG. 5 step 503 performing an operation for obtaining the target intake air amount Gnt from the numerical table based on the rotational speed NE and the fuel injection amount Q _fin. Next, in steps 505 to 513, 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 as described above.

That is, in step 505, 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 fixed value α or more. 23 target opening VE
With increasing set the G ₀ by a predetermined amount [Delta] V, the actual EGR valve 23 opening VEG is target opening VE at step 513
Adjusted to be G _0. As a result, the amount of EGR gas returning to the intake system increases, and the amount Gn of fresh air sucked into the engine relatively decreases. On the other hand, step 505
If Gn−Gnt ≦ α, then in step 509, it is determined whether or not the actual intake air amount Gn is smaller than the target air amount Gnt by α or more (whether Gn−Gnt <−α). If it is smaller than α, the EGR is performed in step 511.
The target opening degree VEG ₀ of the valve 23 is reduced by a fixed amount ΔV, and at step 513 the actual opening degree VEG
EG is adjusted to the target opening VEG _0. As a result, the amount of EGR gas recirculated to the intake system decreases, and the amount Gn of fresh air sucked into the engine relatively increases. By executing steps 505 to 513, the actual intake air amount Gn is controlled within a range of ± α with respect to the target intake air amount Gnt.

FIG. 6 shows a DPF trapping state determination operation performed during the execution of the EGR feedback control of FIG. In FIG. 6, when the operation is started, it is determined in a step 601 whether or not the EGR feedback control of FIG. 5 is currently being performed. This operation is terminated as it is.

At step 601, the current EGR feedback
If the lock control is being executed, then in step 603
Current engine speed NE and fuel injection amount Q_finWith
Next, the EGR valve opening sensor 51 detects the current EGR valve 23
The opening degree VEG is read. Then, in step 605,
Current engine speed NE and fuel injection amount Q_finCorresponding to
EG in the reference state (the non-collection state of the DPF 43)
Calculate the R valve opening degree VEGb. VEGb is in the reference state
The current rotational speed NE and the fuel injection amount Q_finAnd engine
This is the opening of the EGR valve when the
NE and Q _finE in the form of a numerical table using
It is stored in the ROM of the CU 30.

Next, at step 607, the EGR valve opening VEGb in the reference state and the actual EGR valve opening VEG
Is larger than a predetermined value ΔVEG (ΔVEG is a positive value). If VEGb−VEG> ΔVEG, that is, it is considered that the EGR feedback control has reduced the EGR valve opening degree as compared with the reference state because the particulate collection amount of the DPF 43 has increased. The value of the collection alarm flag XDPF and the value of the DPF regeneration operation execution flag XR are set to 1, and the current operation ends. ΔVEG is D
This is the difference between VEGb and VEG when PF collects particulates up to the maximum allowable amount, and is set in advance by experiments. The functions of the flags XDPF and XR are the same as those in the first embodiment. In step 607, V
If EGb−VEG ≦ ΔVEG, the current DP
Since the particulate collection amount in F43 is within the allowable range, the current operation ends without changing the values of the flags XDPF and XR.

In this embodiment, a sensor for detecting the opening of the EGR valve 23 is provided to determine the trapping amount based on the actually detected opening of the EGR valve. For example, an EGR valve having a solenoid actuator is used. In such cases, the duty ratio of the drive pulse signal of the solenoid actuator (the ratio of the period during which the drive pulse is on to one drive pulse period) is a value corresponding to the EGR valve opening. For this reason, when such an EGR valve is used, the trapping amount is determined using the duty ratio of the EGR valve drive pulse instead of the EGR valve opening without providing the EGR valve opening sensor. Is also good.

(5) Fifth Embodiment In this embodiment, the DP in the fourth embodiment is different from the DP in the fourth embodiment.
When it is determined that the particulate trapping amount of F is increasing and the DPF regeneration operation is performed, the operation time immediately after regeneration is set as a new reference state, and N in the reference state is newly set.
E, performs an operation to determine the relationship between the Q _fin and the EGR valve opening VEG.

After the DPF is regenerated and the entire amount of the particulate matter trapped in the DPF is burned and removed, the relationship between NE, _Qfin and VEG was originally stored in the reference state which was initially stored. There is no need to seek these relationships again to return to. However, in the actual operation, the nonflammable ash component contained in the exhaust gas is collected in the DPF together with the particulates, and remains on the DPF even after the regeneration of the DPF. For this reason, the ash component is gradually accumulated in the DPF, and the DPF pressure loss after the execution of the regeneration operation increases. For this reason, if the collection state of particulates is determined using the relationship of the reference state created when the DPF is new, accurate determination may not be possible.
Therefore, in the present embodiment, when the regeneration operation of the DPF is completed, the engine speed NE and the fuel injection amount Q during the EGR feedback control during a predetermined operation period after the regeneration is completed.
The values of _fin and the EGR valve opening degree VEG are stored, and a numerical table of a new reference state is created. As a result, it is possible to prevent an error in the determination of the amount of trapped particulates in the DPF due to ash accumulation. When the ash accumulation amount increases, the EGR valve opening degree VEG after the end of the DPF regeneration operation
Gradually decreases. Therefore, it is also possible to determine the ash accumulation state from the change in the EGR valve opening VEG in a new reference state created after the end of the regeneration operation.

(6) Sixth Embodiment Next, a sixth embodiment of the present invention will be described. In the present embodiment, the operating state of the engine 1 is changed from a predetermined first state to a second state, and the particulate collection state of the DPF is determined based on the amount of load parameter change before and after the change. Further, in the present embodiment, the change from the first operating state to the second operating state is based on the engine exhaust passage 3.
The exhaust throttle valve 37 disposed in the above is throttled from a fully opened state to a predetermined opening degree, and the intake air amount of the engine is used as a load parameter.

When the exhaust throttle valve 37 is throttled, the back pressure of the exhaust increases, so that the difference between the intake pipe pressure and the exhaust manifold pressure increases. For this reason, even if the EGR valve opening is maintained constant, the amount of EGR gas recirculated to the intake system increases. Further, since the exhaust resistance of each cylinder increases due to the increase of the exhaust manifold pressure, the amount of intake air taken into the cylinder further decreases. In particular, in the present embodiment, since the engine provided with the turbocharger 35 is used, when the exhaust throttle valve 37 performs the exhaust throttle, the turbine back pressure increases and the turbocharger rotation speed decreases. For this reason, the influence of the decrease of the supercharging pressure is added to the above, and the intake air amount further decreases.

On the other hand, in the state where the amount of trapped particulates of the DPF 43 is increased, the back pressure has already increased to some extent due to the increased pressure loss of the DPF 43. For this reason, when the same exhaust throttle is given by the exhaust throttle valve 37 in the same operation state, the influence of the exhaust throttle by the exhaust throttle valve 37 becomes relatively smaller as the amount of trapped particulates of the DPF 43 becomes larger. The amount of decrease in the amount of air is small. In the present embodiment, the exhaust throttle valve 37 is previously opened from the fully opened state in each operating state of the engine (rotational speed NE, fuel injection amount Q _fin ) in the particulate non-collecting state (reference state) of the DPF 43 in advance. The amount of change ΔGnb of the engine intake air amount Gn when the engine
In the form of a numerical table using NE and _Qfin . Then, when a predetermined condition is satisfied during the actual operation of the engine, the exhaust throttle valve 37 is throttled from the fully opened state to the predetermined opening degree, and the intake air amount change amount ΔGn at that time is reduced.
The same rotational speed NE, by comparing the variation ΔGnb in the reference state in the fuel injection amount Q _fin determines collected particulates status of DPF 43.

FIG. 7 is a flowchart for explaining the DPF trapping state determination operation of this embodiment. This operation is EC
This is performed as a routine executed by the U30 at regular intervals. When the operation of FIG.
Then, it is determined whether or not a condition for executing the determination of the particulate collection state of the DPF 43 is currently satisfied.
The conditions for performing the determination in step 701 include that the EGR feedback control is not currently being performed, that a predetermined time has elapsed since the previous collection state determination was performed (or that the engine speed integrated value or vehicle (E.g., the traveling distance has become equal to or greater than a predetermined value), and that the engine is operating in a steady state under a predetermined load condition (for example, low load). The reason why the collection determination is not performed during the execution of the EGR feedback control is that the EGR amount is controlled so that the engine intake air amount becomes a predetermined value during the execution of the feedback control, so that accurate determination may not be performed. is there. Further, the condition that a predetermined time has elapsed since the previous execution of the collection determination is set as a condition that, when the intake throttle valve 37 is closed for the determination of the collection state, the output of the engine may be reduced. This is because it is not preferable to perform the determination too frequently.

If any of the above conditions is not satisfied in step 701, the operation immediately ends without executing the determination in step 703 and subsequent steps. If all the above determination operation conditions are satisfied in step 701, it is next determined in step 703 whether the value of the determination operation execution flag XF is set to 1. XF is a flag indicating whether or not the determination operation is currently being performed. When the value of XF is set to 1 (execute), the ECU separately determines
The exhaust throttle valve 37 is executed by a routine executed by the exhaust throttle valve 37.
Is closed to a predetermined opening, and when it is set to 0, the exhaust throttle valve 37 is opened. In addition, the flag XF has a function of executing steps 705 to 711, which will be described later, only once when the determination condition is satisfied.

In step 703, the current collection state determination operation
If not executed (XF （1), the next step
Proceeding to 705, the rotation speed sensor 55, the air flow meter 2
5 to read the current rotational speed NE and the intake air amount Gn.
And the fuel injection amount separately executed by the ECU 30
The current fuel injection amount Q calculated by the arithmetic operation_finRead
See in. Also, in step 707, in step 705
The read value of the intake air amount Gn is changed before the operating state changes (exhaust
Gn)₁As well as step
In step 709, the operating state read in step 705 is changed.
NE, Q before _finOf the ECU 30 based on the value of
From the numerical table stored in M, the suction air in the reference state
A change amount reference value ΔGnb of the air volume is obtained. And the above operation
After completion of the operation, in step 711, the judgment operation execution flag XF is set.
The value is set to 1 and the current operation ends.

Next, when the operation is executed, step 703 is executed.
Since XF = 1, step 713 is executed after step 703. That is,
Steps 705 to 709 are executed only once at the start of the collection state determination operation. In step 713, after the current collection state determination operation is started, that is, in step 703,
It is determined whether or not the elapsed time since the establishment of XF = 1 has reached a predetermined time. This predetermined time is
This is the time required for the intake throttle valve 37 to close to a predetermined opening and the amount of intake air to finish changing to a value corresponding to the opening of the throttle valve 37, and is determined in detail by experiments and the like.

If the predetermined time has not elapsed in step 713, the current execution of this operation is immediately terminated. On the other hand, if the predetermined time has elapsed in step 713, the current value of the intake air amount Gn is read from the air flow meter 25 in step 715, and the value of Gn is read after the operating state changes (after the exhaust throttle). stored as the intake air amount Gn _2. In step 719, the difference (i.e., the variation ΔGn the intake air amount) is the reference state of the intake air quantity Gn ₂ of the intake air amount Gn ₁ before operation state change stored operating state after the change in step 707 Change amount ΔGnb
It is determined whether the value is smaller than the predetermined value β.

(Gn ₁ -Gn ₂ ) ≦ ΔGnb-β, that is, the change amount (Gn ₁ -Gn ₂ ) is the change amount ΔG of the reference state.
If it is smaller than nb by a predetermined value β or more, it is considered that the particulate trapping amount of the DPF has increased and has reached the maximum allowable value. Therefore, in steps 721 and 723, the trapping amount alarm XDPF and the DPF regeneration operation are executed. After setting the value of the flag XR to 1, the value of the collection determination operation execution flag XF is set to 1 in step 725, and the operation ends.
The determination value β of the intake air change amount is a change amount of the intake air amount before and after the exhaust throttle when the amount of trapped particulates of the DPF reaches the maximum allowable value, and is set in advance based on an experiment or the like. You. When the values of the flag XDP and the flag XF are reset to 0, the exhaust throttle valve 37 is opened,
The collecting operation ends.

Since the functions of the flags XDPF and XR in steps 7721 and 723 are the same as those of the first embodiment, detailed description is omitted here. If Gn ₁ −Gn ₂ > Gn−β in step 719,
Since the amount of change in the intake air amount has not changed much from the amount of change in the reference state, and the amount of trapped particulates in the DPF 43 has not increased, the values of the flags XDPF and XR are not changed, and the flow proceeds to step 725. Collection determination operation execution flag XF
Is reset to 0, and the operation is terminated.

In the present embodiment, the operating state is changed by the exhaust throttle, but instead of the exhaust throttle, a waste gate valve (hereinafter referred to as “WGV”) of a turbocharger is used.
(Hereinafter referred to as “open”), it is also possible to determine the particulate collection state of the DPF based on a change in the intake air amount when the operating state is changed. Usually, a turbocharger is provided with a WGV for preventing the discharge pressure from excessively increasing. The WGV communicates a turbine inlet and outlet with a portion of exhaust gas bypassing the turbine and leading to a downstream exhaust passage. When the WGV opens, the flow rate of exhaust gas flowing into the turbine decreases, so that the turbocharger rotation speed decreases and the supercharging pressure decreases. Therefore, when the WGV is opened, the intake air amount of the engine decreases. However, also in this case, if the amount of trapped particulates in the DPF is increased, the turbocharger has already decreased in rotational speed even before the WGV valve is opened due to the increase in the back pressure. Is relatively smaller than the reference state. Therefore, by comparing the change (decrease) amount ΔGn of the intake air amount when the WGV valve is opened with the change amount ΔGnb in the reference state, the DP similar to FIG.
It is possible to determine the collection amount of F.

(7) Seventh Embodiment Next, a seventh embodiment of the present invention will be described. In the present embodiment, the trapping state of the DPF 43 is determined using the engine intake pipe pressure as a load parameter. Determining the trapping state using the intake pipe pressure is particularly effective for an engine having an EGR cooler in the EGR passage.

In an engine that performs EGR feedback control, when particulates accumulate in the exhaust passage of the EGR cooler and the pressure loss of the cooler increases, the EGR feedback control is performed in a direction to increase the EGR valve opening. On the other hand, as described above, when the particulate matter trapping amount of the DPF increases, the EGR feedback control
Control is performed in a direction to reduce the R valve opening. For this reason,
In an engine equipped with an EGR cooler, the effects of an increase in the amount of particulates accumulated in the EGR cooler and an increase in the amount of trapped particulates in the DPF cancel each other,
Accurate DPF collection amount determination cannot be made from the EGR valve opening during the EGR feedback control.

However, the intake pipe pressure changes only in accordance with the amount of particulates collected by the DPF irrespective of the state of particulate accumulation in the EGR cooler. That is, DP
When the particulate collection amount of F increases, the back pressure of the turbocharger increases, so that the turbocharger rotation speed decreases and the supercharging pressure decreases. On the other hand, even if the particulate matter accumulation amount of the EGR cooler increases, the supercharging pressure does not change because the back pressure of the turbocharger does not increase. For this reason, by using the intake pipe pressure (supercharging pressure) as a load parameter, it is possible to determine the particulate collection state of only the DPF without being affected by the EGR cooler.

FIG. 8 is a flowchart for explaining the DPF trapping state determination operation of this embodiment. This operation is EC
This is performed by a routine executed at regular intervals by U30. In the operation of FIG. 8, first, at step 801, it is determined whether the engine 1 is currently in a steady operation. The DPF trapping amount determination based on the intake pipe pressure PM can be executed regardless of whether or not the EGR feedback control is being performed during the steady operation in which the fluctuation of the intake pipe pressure PM is small.

In step 801, the vehicle is currently in steady operation.
In this case, next, at step 803, the current engine speed NE
And fuel injection quantity Q_finIs read, and the intake pressure sensor
From 59, the current intake pipe pressure PM is read. Soshi
In step 805, the rotational speed N read as described above is used.
E and fuel injection quantity Q _finFrom the same in the reference state
The intake pipe pressure PMb at the rotational speed and the fuel injection amount is calculated.
You. In this embodiment, the reference state (the putty of the DPF 43) is determined in advance.
The engine 1 is rotated and the fuel is
The value of the intake pipe pressure PM actually measured by changing the injection amount and operating
As the intake pipe pressure PMb in the reference state, the rotational speed NE
And fuel injection quantity Q_finEC in the form of a numerical table using
It is stored in the ROM of U30. In step 805,
NE and Q read in step 803_finAnd using
From this numerical table, the intake pipe pressure PM in the reference state
Read b.

After calculating PMb as described above, step 807
In, it is determined whether or not the difference between the intake pipe pressure PMb in the reference state and the current intake pipe pressure PM is larger than a determination value ΔPM. Here, ΔPM is the value when the particulate collection amount of the DPF 43 increases to the maximum allowable amount.
This corresponds to the amount of decrease in the intake pipe pressure with respect to the reference state, and is set by an experiment using an actual engine and DPF.

If PMb−PM> ΔPM in step 807, the particulate matter is collected in the DPF 43 in excess of the maximum allowable amount.
In 811 and 811, the values of the trapped amount alarm XDPF and the DPF regeneration operation execution alarm XR are set to 1. The functions of the flags XDPF and XR are the same as those of the first embodiment.

In the present embodiment, the determination operation shown in FIG.
Accurate D without being affected by GR cooler blockage
It is possible to determine the particulate collection state of the PF.
Further, in the present embodiment, the particulate collection state of the DPF is accurately determined by the determination operation of FIG.
Subsequent to the above operation, it is also possible to easily determine whether or not the EGR cooler is clogged. That is, for example, when it is determined in the operation of FIG.
During the GR feedback control, when the EGR valve opening increases compared to the reference state, it can be determined that the EGR cooler is clogged. Therefore, FIG.
When the amount of particulates collected by the DPF is small in the operation (or immediately after the DPF regeneration operation is performed), for example, the fourth
The operation (FIG. 6) described in the first embodiment is performed, and the actual EG
EGR valve opening VEG when R valve opening VEG is in reference state
When it is larger than b by a predetermined value or more, it can be determined that the EGR cooler is clogged.

[0097]

According to the invention described in each of the claims, the particulate filter of the particulate filter can be easily and accurately collected without providing a special detector only for judging the particulate collection state of the particulate filter. There is a common effect that allows determination of the gathering state.

[Brief description of the 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 a first embodiment of a particulate filter trapped amount determination operation according to the present invention.

FIG. 3 is a flowchart illustrating a second embodiment of a particulate filter trapped amount determination operation according to the present invention.

FIG. 4 is a flowchart illustrating a third embodiment of a particulate filter trapped amount determination operation according to the present invention.

FIG. 5 is a flowchart illustrating an EGR feedback control operation according to a fourth embodiment of the present invention.

FIG. 6 is a flowchart illustrating a fourth embodiment of a particulate filter trapped amount determination operation according to the present invention.

FIG. 7 is a flowchart illustrating a sixth embodiment of the particulate filter trapped amount determination operation of the present invention.

FIG. 8 is a flowchart illustrating a seventh embodiment of the particulate filter trapped amount determination operation according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine main body 2 ... Intake passage 3 ... Exhaust passage 23 ... EGR valve 35 ... Turbocharger 37 ... Exhaust throttle valve 43 ... Particulate filter 45 ... EGR cooler

Continued on the front page (72) Inventor Takao Fukuma 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Tomoyuki Ono 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Invention Person Masahito Shibata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Hiroki Matsuoka 1 Toyota Town, Toyota City, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yoshimitsu Heda Toyota City Toyota City, Aichi Prefecture No. 1 Toyota Motor Corporation (72) Inventor Kazuo Takahashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yasuhiko Otsubo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Motoshiro Endo 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (Reference) 3G062 AA01 BA04 BA06 ED08 GA06 GA15 GA21 3G090 AA02 BA01 CB23 DA09 DA18 DA20 DB03 DB07 DB10 EA05 EA06

Claims (9)

[Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine, comprising a particulate filter disposed in an exhaust passage of the internal combustion engine for trapping particulates in exhaust gas, wherein the operating state detection detects a current operating state of the engine. Means, a load parameter detecting means for detecting a load parameter related to the load state of the engine, and the engine operation state and the load parameter in a reference state in which the particulate collection amount of the particulate filter is a predetermined value. Storage means for storing the relationship; a value stored in the storage means corresponding to a value of the load parameter detected by the load parameter detection means and a current operation state detected by the operation state detection means during engine operation. The particulate filter of the particulate filter is compared with the value of the load parameter in the state. Exhaust gas purification apparatus for an internal combustion engine and a determining means for collecting state. 2. The load parameter detecting means detects an engine intake air amount as the load parameter.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 3. The load parameter detecting means detects an engine fuel injection amount as the load parameter, and the determining means determines whether or not the current operation state detected by the operating state detecting means is idling. 2. A method for judging a particulate collection state of a curated filter.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 4. The internal combustion engine according to claim 2, wherein said determination means determines the particulate collection state of said particulate filter when the current operation state detected by said operation state detection means is a deceleration operation. Engine exhaust purification device. 5. An internal combustion engine, comprising: an EGR passage connecting an engine exhaust system and an engine intake system; an EGR valve arranged in the EGR passage to control an exhaust gas flow returning to the engine intake system through the EGR passage; EGR control means for performing feedback control of the EGR valve opening so that the engine intake air amount becomes a predetermined value in accordance with the engine operating state, wherein the load parameter detecting means includes the EGR valve opening as the load parameter. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the degree is detected. 6. The determination means includes means for burning and removing the particulates collected by the particulate filter, and when the amount of the particulates collected by the particulate filter is equal to or more than a predetermined amount. When it is determined that there is, the particulate matter collected by the particulate filter is burned, and after the combustion is completed, the relationship between the engine operating state and the EGR valve opening degree is newly obtained. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein a relationship between an engine operating state and an EGR valve opening is updated using a relationship obtained after the completion of the combustion. 7. An exhaust gas purifying apparatus for an internal combustion engine, comprising a particulate filter disposed in an exhaust passage of the internal combustion engine for trapping particulates in exhaust gas, wherein the first operating condition of the engine is predetermined. Operating state changing means for changing a state to a predetermined second operating state; load parameter detecting means for detecting a load parameter related to a load state of the engine; and a particulate trapping amount of the particulate filter is predetermined. Storage means for storing an amount of change in the value of the load parameter before and after the change from the first operating state to the second operating state in the reference state, the operating state changing means during engine operation. When the engine operating state is changed from the first operating state to the second operating state, a negative value before and after the change detected by the load parameter detecting means is obtained. A determination unit that determines a particulate collection state of the particulate filter by comparing a variation amount of the parameter with a variation amount of the load parameter in the reference state stored in the storage unit. Exhaust gas purification device. 8. The operating state changing means includes exhaust throttle means for reducing an engine exhaust flow rate, and changes the degree of exhaust throttling by the exhaust throttle means from a first state to a second state which is predetermined. The exhaust gas purification of an internal combustion engine according to claim 7, wherein the operating state is changed from the first operating state to the second operating state, and the load parameter detecting means detects an intake air amount of the engine as the load parameter. apparatus. 9. The internal combustion engine includes a turbocharger provided in an engine exhaust system, an EGR passage connecting the engine exhaust system and the engine intake system, and an EGR passage arranged in the EGR passage to the engine intake system. EG for controlling the recirculated exhaust flow rate
An R valve, an EGR cooler that is disposed in the EGR passage, and cools the exhaust gas flowing back to the engine intake air amount system through the EGR passage, such that the engine intake air amount becomes a predetermined value according to the engine operating state. EGR control means for performing feedback control of the EGR valve opening degree, wherein the load parameter detection means detects an engine intake pipe pressure as the load parameter, and the determination means determines whether the load parameter detection means By comparing the detected intake pipe pressure with the value of the intake pipe pressure in the reference state stored in the storage means corresponding to the current operation state detected by the operation state detection means, the EGR flow of the EGR cooler is compared. 2. The exhaust gas of an internal combustion engine according to claim 1, wherein a particulate collection state of the particulate filter is determined irrespective of whether a path is clogged. 3. Purification device.