JP2012241594A - Function diagnostic device of oxidation catalyst, and exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a function diagnostic device of an oxidation catalyst and an exhaust emission control device capable of continuously or stepwise determining purification efficiency of the oxidation catalyst without considerably increasing fuel injection amount.SOLUTION: Normal time HC storage amount stored in the oxidation catalyst for a prescribed period is estimated on the assumption that the oxidation catalyst is not deteriorated, required oxygen amount to oxidize HC corresponding to the normal time HC storage amount is calculated, actual oxygen consumption amount consumed to oxidize HC actually stored for the prescribed time is calculated, and the purification efficiency of the oxidation catalyst is determined on the basis of a ratio of the required oxygen amount to the actual oxygen consumption amount.

Description

  The present invention relates to an oxidation catalyst function diagnosis device for diagnosing the function of an HC storage type oxidation catalyst provided in an exhaust passage of an internal combustion engine, and an exhaust emission control device including such an oxidation catalyst function diagnosis device.

  Conventionally, an exhaust passage of an internal combustion engine mounted on a vehicle or the like is provided with an oxidation catalyst used for purifying exhaust gas. As one aspect of this oxidation catalyst, there is one that purifies HC (unburned fuel) in exhaust gas by oxidation (combustion) on the catalyst.

  The oxidation catalyst efficiently oxidizes HC at a temperature higher than the activation temperature, and has a characteristic of occluding HC at a temperature lower than a predetermined temperature lower than the activation temperature (hereinafter referred to as “occlusion upper limit temperature”). Yes. Since the oxidation efficiency and occlusion amount of HC by the oxidation catalyst decrease as the deterioration of the oxidation catalyst proceeds, the exhaust purification efficiency decreases as the deterioration of the oxidation catalyst proceeds. For this reason, various apparatuses for detecting abnormality of the oxidation catalyst have been proposed.

  For example, a catalyst abnormality detection device has been proposed in which abnormality determination is accurately performed without the timing for determining whether the oxidation catalyst is abnormal being limited by the operating state of the internal combustion engine. Specifically, the exhaust temperature adjusting means controls the internal combustion engine to adjust the exhaust temperature upstream of the oxidation catalyst to a determination permission temperature that activates when the oxidation catalyst is normal and does not activate when the oxidation catalyst is abnormal. When the upstream exhaust temperature reaches the determination permission temperature, the unburned fuel supply means supplies unburned fuel to the oxidation catalyst, and the determination means obtains the amount of change in the downstream exhaust temperature with respect to the upstream exhaust temperature of the oxidation catalyst. A catalyst abnormality detection device configured to determine that the oxidation catalyst is abnormal when the amount of change is smaller than a determination value is disclosed (see Patent Document 1).

JP 2010-203238 A

  By the way, in recent years, the exhaust gas purification standard has been further increased with the increasing interest in environmental measures. For this reason, even in the standards of exhaust gas purification device self-diagnosis (On Board Diagnosis), it is beginning to be required to grasp the abnormal state of the exhaust gas purification device with higher accuracy and in more detail. In particular, regarding the state of the oxidation catalyst, it has begun to be required to know in detail the purification efficiency as well as whether or not an abnormality has occurred.

  However, the catalyst abnormality detection device described in Patent Document 1 only determines whether or not the amount of change in the downstream exhaust temperature with respect to the upstream exhaust temperature of the oxidation catalyst is greater than or equal to a predetermined amount, and the oxidation catalyst is abnormal. It can only be determined on or off whether or not there is. The various abnormality detection devices conventionally proposed in addition to Patent Document 1 are also used to determine whether the oxidation catalyst is abnormal or not on an on-off basis, and perform continuous or stepwise determination of purification efficiency. I can't. In other words, since the conventional oxidation catalyst abnormality detection device cannot grasp in detail how much the current purification efficiency of the oxidation catalyst is, the request for the self-diagnosis standard of the exhaust purification device is not required. You may not be satisfied.

  Further, the catalyst abnormality detection device described in Patent Document 1 uses an exothermic reaction due to oxidation of unburned fuel supplied when the abnormality determination of the oxidation catalyst is performed, and a relatively large amount of unburned fuel is removed. Since it is necessary to supply the oxidation catalyst, it is necessary to increase the fuel injection amount, and it is not possible to spend a long time for diagnosis.

  In view of such a problem, the inventors of the present invention have found that such a problem can be solved by determining the purification efficiency using the oxygen consumption consumed for oxidizing HC with an oxidation catalyst, The present invention has been completed. That is, an object of the present invention is to provide an oxidation catalyst function diagnosis device and an exhaust purification device that can determine the purification efficiency of an oxidation catalyst continuously or stepwise without significantly increasing the fuel injection amount. To do.

  According to the present invention, in the oxidation catalyst function diagnostic device for diagnosing the purification efficiency of the HC storage type oxidation catalyst provided in the exhaust passage of the internal combustion engine, assuming that the oxidation catalyst is not deteriorated, Normal HC storage amount estimation means for estimating a normal HC storage amount stored in the oxidation catalyst during a predetermined period, and a required oxygen amount for calculating a required oxygen amount for oxidizing HC equivalent to the normal HC storage amount A calculation means; an actual oxygen consumption estimation means for estimating an actual oxygen consumption consumed to oxidize HC actually stored in the predetermined period; and a ratio between the required oxygen amount and the actual oxygen consumption. And a determination means for determining the purification efficiency of the oxidation catalyst based on the above, a function diagnostic device for an oxidation catalyst is provided, which can solve the above-mentioned problems.

  That is, the function diagnostic device for an oxidation catalyst according to the present invention oxidizes a normal HC storage amount estimated to be stored in a predetermined period in an inactive state of the oxidation catalyst when it is assumed that the oxidation catalyst has not deteriorated. Purification of the oxidation catalyst based on the ratio of the required oxygen amount for the oxidation and the actual oxygen consumption amount consumed to oxidize the actual HC storage amount actually stored during a predetermined period, which is obtained based on the oxygen concentration It is configured to determine efficiency. According to the function diagnostic device for an oxidation catalyst having such a configuration, the purification efficiency of the oxidation catalyst can be determined continuously or step by step without a large amount of fuel injection, and the self-diagnosis standard of the exhaust purification device is satisfied. Can make it possible.

  In the oxidation catalyst function diagnostic apparatus of the present invention, it is preferable that the predetermined period is a period from when the internal combustion engine is cold started until the oxidation catalyst reaches the upper limit storage temperature.

  Thus, by determining the purification efficiency of the oxidation catalyst based on the ratio of the required oxygen amount obtained based on the amount of HC stored in the oxidation catalyst at the cold start and the actual oxygen consumption amount, It is possible to diagnose the purification efficiency of the oxidation catalyst without forcibly increasing the HC contained therein. If the purification efficiency is diagnosed at the time of cold start, it is possible to secure an opportunity to execute at least one diagnosis every time the internal combustion engine is operated.

  Further, in the oxidation catalyst function diagnosis device of the present invention, the normal time HC storage amount estimation means integrates the instantaneous storage amount until the oxidation catalyst reaches the storage upper limit temperature when the internal combustion engine is cold-started. Thus, it is preferable to estimate the normal HC occlusion amount.

  If the normal HC storage amount is estimated in this way, it is possible to estimate the normal HC storage amount relatively accurately and easily.

  In the oxidation catalyst function diagnostic apparatus of the present invention, the normal time HC storage amount estimation means calculates the instantaneous storage amount according to an exhaust gas temperature upstream of the oxidation catalyst detected using an exhaust gas temperature sensor. It is preferable to obtain.

  Thus, by obtaining the instantaneous storage amount of the oxidation catalyst at the time of cold start, the instantaneous storage amount can be accurately estimated, and as a result, the normal time HC storage amount can be accurately estimated.

  Further, in the oxidation catalyst function diagnosis apparatus according to the present invention, the actual oxygen consumption estimation means includes an oxygen concentration upstream of the oxidation catalyst determined based on a fuel injection amount of the internal combustion engine, and the oxidation catalyst. It is preferable to calculate the actual oxygen consumption by integrating the difference between the oxygen concentration and the downstream oxygen concentration.

  By calculating the actual oxygen consumption in this way, it is possible to relatively accurately calculate the actual oxygen consumption actually consumed in the oxidation catalyst.

  Further, in the function diagnostic apparatus for an oxidation catalyst of the present invention, the actual oxygen consumption estimation means has a difference between the oxygen concentration on the upstream side and the oxygen concentration on the downstream side equal to or greater than a predetermined first threshold value. It is preferable that sometimes the integration is started and the integration is terminated when the difference in oxygen concentration becomes equal to or less than a predetermined second threshold value.

  By estimating the actual oxygen consumption in this way, the actual oxygen consumption used for the oxidation of the HC from the time when the HC stored in the predetermined period starts to be oxidized until the end of the oxidation. It is possible to improve the estimation accuracy.

  According to another aspect of the present invention, an oxidation catalyst function diagnosis device for diagnosing the purification efficiency of an HC storage type oxidation catalyst provided in an exhaust passage of an internal combustion engine flows into the oxidation catalyst during a predetermined period. HC inflow estimation means for estimating HC inflow, actual oxygen consumption estimation means for estimating actual oxygen consumption actually consumed by the oxidation catalyst during the predetermined period, and the actual oxygen consumption based on the actual oxygen consumption HC oxidation amount estimation means for estimating the HC oxidation amount actually oxidized by the oxidation catalyst during a predetermined period, and determination for determining the purification efficiency of the oxidation catalyst based on a ratio between the HC inflow amount and the HC oxidation amount Means for diagnosing the function of an oxidation catalyst.

  That is, the oxidation catalyst function diagnosis apparatus according to another aspect of the present invention is obtained based on the HC inflow amount and oxygen concentration that flowed into the oxidation catalyst during a predetermined period when it is assumed that the oxidation catalyst has not deteriorated. The purification efficiency of the oxidation catalyst is determined based on the ratio with the HC oxidation amount actually oxidized by the oxidation catalyst during a predetermined period. According to the oxidation catalyst function diagnostic device having such a configuration, the purification efficiency of the oxidation catalyst can be determined continuously or step by step without significantly increasing the fuel consumption, and the self-diagnosis standard of the exhaust purification device is satisfied. Can be allowed to.

  Yet another aspect of the present invention is an exhaust emission control device including any of the above-described oxidation catalyst function diagnosis devices.

  That is, according to the exhaust emission control device of the present invention, since the oxidation catalyst function diagnostic device capable of determining the purification efficiency of the oxidation catalyst continuously or step by step without significantly increasing the fuel consumption, It is possible to grasp the appropriate purification efficiency in accordance with the self-diagnosis standard of the exhaust purification device, and to provide an exhaust purification device capable of maintaining the exhaust purification efficiency.

It is a figure shown in order to explain roughly the composition of the exhaust-air-purification device of an internal-combustion engine provided with the function diagnostic device of the oxidation catalyst concerning a 1st embodiment. It is a figure shown in order to demonstrate the structure of the function diagnostic apparatus of the oxidation catalyst concerning 1st Embodiment. It is a figure shown in order to demonstrate the relationship between the temperature of an oxidation catalyst, and HC occlusion amount. It is a figure shown in order to demonstrate the calculation method of HC occlusion amount at the time of normal. It is a figure which shows notionally the calculation method of real oxygen consumption. It is a figure shown in order to demonstrate the relationship between the temperature of an oxidation catalyst, and HC purification rate. It is a figure shown in order to demonstrate the determination method of purification efficiency. It is a timing chart figure shown in order to demonstrate the function diagnostic method of an oxidation catalyst. It is a flowchart figure shown in order to demonstrate the function diagnostic method of the oxidation catalyst performed by the function diagnostic apparatus of the oxidation catalyst concerning 1st Embodiment. It is a flowchart shown in order to demonstrate an example of the calculation method of HC occlusion amount at the time of normal. It is a flowchart figure shown in order to demonstrate an example of the calculation method of real oxygen consumption. It is a figure shown in order to demonstrate roughly the structure of the exhaust gas purification apparatus of the internal combustion engine provided with the function diagnostic apparatus of the oxidation catalyst concerning 2nd Embodiment. It is a figure shown in order to demonstrate the structure of the function diagnostic apparatus of the oxidation catalyst concerning 2nd Embodiment. It is a flowchart figure shown in order to demonstrate the function diagnostic method of the oxidation catalyst performed by the function diagnostic apparatus of the oxidation catalyst concerning 2nd Embodiment. It is a flowchart shown in order to demonstrate an example of the calculation method of HC inflow amount. It is a flowchart figure shown in order to demonstrate an example of the calculation method of real oxygen consumption.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to an oxidation catalyst function diagnosis apparatus and an exhaust purification apparatus according to the present invention will be specifically described below based on the drawings.
In addition, what is attached | subjected with the same code | symbol in each figure has shown the same component unless there is particular description, and description is abbreviate | omitted suitably.

[First Embodiment]
The oxidation catalyst function diagnosis apparatus and exhaust purification apparatus according to the first embodiment of the present invention improve the purification efficiency of the oxidation catalyst by utilizing the fact that HC is stored in the oxidation catalyst when the internal combustion engine is cold-started. It is comprised so that it may determine.

  FIG. 1 is a diagram for schematically explaining the configuration of an exhaust gas purification apparatus for an internal combustion engine provided with an oxidation catalyst function diagnosis apparatus according to a first embodiment. FIG. 2 is a diagram for explaining the configuration of the oxidation catalyst function diagnosis apparatus according to the first embodiment. FIG. 3 is a diagram for explaining the relationship between the temperature of the oxidation catalyst and the HC storage amount. FIG. 4 is a diagram for explaining a calculation method of the normal-time HC storage amount. FIG. 5 is a diagram conceptually illustrating a method of calculating actual oxygen consumption. FIG. 6 is a diagram for explaining the relationship between the temperature of the oxidation catalyst and the HC purification rate. FIG. 7 is a diagram for explaining a method for determining the purification efficiency. FIG. 8 is a timing chart for explaining the function diagnosis method of the oxidation catalyst. FIG. 9 to FIG. 11 are flowcharts for explaining an oxidation catalyst function diagnostic method executed by the oxidation catalyst function diagnostic apparatus according to the first embodiment.

1. Overall Configuration of Exhaust Purification Device In FIG. 1, an internal combustion engine 1 is typically a diesel engine, which includes a plurality of fuel injection valves 5 and an exhaust pipe 3 through which exhaust gas is circulated. The fuel injection valve 5 is energized and controlled by the electronic control unit 30. The electronic control unit 30 calculates the target fuel injection amount Q based on the engine speed Ne, the accelerator operation amount Acc, and other information, The energization timing and energization time of the fuel injection valve 5 are determined based on the calculated target fuel injection amount Q, and the energization control of the fuel injection valve 5 is executed.

An exhaust gas purification device 10 is provided in the exhaust pipe 3 connected to the internal combustion engine 1. The exhaust purification device 10 includes an oxidation catalyst 11, a particulate filter 12, and a NO _x purification catalyst 13 that are sequentially provided from the upstream side of the exhaust pipe 3. A first exhaust temperature sensor 17 is provided upstream of the oxidation catalyst 11, and a downstream oxygen concentration sensor 18 is provided between the oxidation catalyst 11 and the particulate filter 12. _{Between the X} purification catalyst 13, a second exhaust temperature sensor 15 is provided. In the exhaust gas purification apparatus 10 according to the first embodiment, a lambda sensor is used as the downstream oxygen concentration sensor 18, but it is not particularly limited. The sensor signals of these sensors are input to the electronic control unit 30.

  The oxidation catalyst 11 has a function of oxidizing (combusting) CO and HC contained in the exhaust in the active state, and has a function of storing HC contained in the exhaust in the inactive state. The oxidation catalyst 11 is used not only to purify the exhaust gas but also to raise the exhaust gas temperature by the oxidation heat generated with the oxidation of HC during the regeneration control of the particulate filter 12. The oxidation catalyst 11 that can be used is not particularly limited as long as it is a known diesel oxidation catalyst.

  The particulate filter 12 is a filter having a function of collecting particulates such as soot (hereinafter referred to as “PM (Particulate Material)”) contained in the exhaust gas discharged from the internal combustion engine 1. The particulate filter 12 is typically a filter having a honeycomb structure, but is not limited to such a filter.

The NO _x purification catalyst 13 is a catalyst having a function of decomposing nitrogen oxides contained in the exhaust gas. As the NO _x purification catalyst 13, a NO _x selective reduction catalyst or a NO _x storage catalyst is mainly used. The NO _x purification catalyst 13 provided in the exhaust purification device 10 shown in FIG. 1 selectively uses nitrogen oxides by using a reducing agent supplied from a reducing agent supply device 20 having a pump 23 and a reducing agent injection valve 25. This is a NO _x selective reduction catalyst to be reduced. As the reducing agent, an aqueous urea solution or unburned fuel is used, but other reducing agents may be used.

The second exhaust temperature sensor 15 is the directly detects a discharge temperature T2, detected exhaust gas temperature T2 is adapted to be used in such estimated temperature Tscr of the NO _X purification catalyst 13 Yes. Further, the estimated temperature Tscr of the NO _x purification catalyst 13 is used for reducing agent injection control by the reducing agent supply device 20, for example. Specifically, the maximum adsorption amount of the reducing agent component or the like in the NO _x purification catalyst 13 changes according to the catalyst temperature Tscr, and the nitrogen oxide purification efficiency also changes according to the current adsorption amount with respect to the maximum adsorption amount. . Therefore, the reducing agent supply device 20 is configured to control whether or not the reducing agent is injected and the injection amount based on the catalyst temperature Tscr estimated from the exhaust temperature T2 detected by the second exhaust temperature sensor 15. ing.

The first exhaust temperature sensor 17 directly detects the exhaust temperature T1 upstream of the oxidation catalyst 11, but the detected exhaust temperature T1 is also used to estimate the temperature Tdoc of the oxidation catalyst 11. It has come to be used. Further, the downstream oxygen concentration sensor 18 is used to detect the oxygen concentration O ₂ —D downstream of the oxidation catalyst 11. Specifically, in the exhaust gas purification device 10 according to the first embodiment, the lambda value is detected by the downstream oxygen concentration sensor 18, so the electronic control device 30 uses the downstream oxygen concentration based on the lambda value. O2_D is obtained. The required oxygen concentration O ₂ —D is used for monitoring the state of the fuel injection system, diagnosing the presence or absence of an abnormality in the injection system of the internal combustion engine 1, and the like.

  In the oxidation catalyst function diagnostic apparatus according to the first embodiment, the purification efficiency η of the oxidation catalyst 11 is determined using the first exhaust temperature sensor 17 and the downstream oxygen concentration sensor 18. Yes.

2. Electronic control device (function diagnostic device)
(1) Device Configuration FIG. 2 is a functional block diagram showing portions related to fuel injection control and functional diagnosis of the oxidation catalyst 11 in the configuration of the electronic control device 30 provided in the exhaust purification device 10. It is a thing. The electronic control device 30 has a function as a function diagnostic device for the oxidation catalyst.

  The electronic control unit 30 is configured around a known microcomputer, and includes a target fuel injection amount calculation means 31, a fuel injection valve control means 33, a normal HC storage amount estimation means 37, and a necessary oxygen amount. Computation means 39, actual oxygen consumption estimation means 41, and determination means 43 are provided. Specifically, each of these means is realized by executing a program by a microcomputer.

  Further, the electronic control unit 30 is provided with a storage means (not shown) composed of storage elements such as a RAM and a ROM, and a fuel injection valve drive circuit 35 for energizing the fuel injection valve 5. In the storage means, a control program and various calculation maps are stored in advance, and calculation results and the like by the respective means described above are written.

  The target fuel injection amount calculation means 31 calculates the target fuel injection amount Q based on the fuel injection amount map from, for example, information S1 on the engine speed Ne and information S2 on the accelerator operation amount Acc. A specific calculation method is not limited, and a conventionally known calculation method can be employed. The fuel injection valve control means 33 determines the energization timing and energization time for the fuel injection valve 5 based on the target fuel injection amount Q and other operating conditions of the internal combustion engine 1, and supplies the fuel injection valve drive circuit 35 with the fuel injection valve drive circuit 35. An instruction signal to be output is generated.

  The normal time HC storage amount estimation means 37 assumes that the temperature of the oxidation catalyst 11 has not deteriorated during the cold start of the internal combustion engine 1, and the period until the temperature Tdoc of the oxidation catalyst 11 reaches the storage upper limit temperature Tdoc_A. The normal HC storage amount Vhc_0 that is considered to be stored in the oxidation catalyst 11 is estimated. The normal-time HC storage amount estimation means 37 of the oxidation catalyst function diagnostic apparatus according to the first embodiment includes the engine start flag information S3, the cooling water temperature Tcl information S4 of the internal combustion engine 1, and the catalyst temperature Tdoc. Based on the information S5, when the engine start flag is On, the cooling water temperature Tcl is equal to or lower than a predetermined threshold Tcl0, and the catalyst temperature Tdoc is lower than the storage upper limit temperature Tdoc_A, the accumulation of the HC storage amount is continued. These conditions are conditions for determining whether or not the internal combustion engine 1 is in a cold start state, and the threshold value Tcl0 of the cooling water temperature Tcl is set to an optimum value obtained by simulation or the like. Can do.

  On the other hand, the normal HC storage amount estimation means 37 ends the integration of the HC storage amount when the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A, and stores the integrated value at that time as the normal HC storage amount Vhc_0. It is configured as follows.

  Specifically, the oxidation catalyst 11 has a characteristic of storing HC in a state below the storage upper limit temperature Tdoc_A, and the instantaneous storage amount at a certain point increases the catalyst temperature Tdoc as shown in FIG. It has a characteristic that decreases with time. Regardless of the deterioration state of the oxidation catalyst 11, the storage upper limit temperature Tdoc_A is a little less than 150 ° C. and is almost constant. Therefore, the internal combustion engine 1 is stopped and then cooled down in a relatively short time. The catalyst temperature Tdoc at the time of the intermediate start is less than the storage upper limit temperature Tdoc_A. Further, when the internal combustion engine 1 is cold started, the temperature of the internal combustion engine 1 is low, so that the fuel combustion efficiency is low, and the amount of HC contained in the exhaust gas is relatively large. Meanwhile, HC is occluded in the oxidation catalyst 11.

  Normally, at the time of cold start when the amount of HC in the exhaust gas increases, the amount of HC is larger than the amount of HC stored in the oxidation catalyst 11, so the total amount of stored HC is the HC of the oxidation catalyst 11. It can be estimated by integrating the amount of occlusion. For example, as shown in FIG. 3B, if the internal combustion engine 1 is started when the catalyst temperature Tdoc is T1, the hatched line obtained by integrating the HC storage amount until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A. The region represents the normal HC storage amount Vhc_0.

  FIG. 4 shows an example of the calculation logic of the normal time HC storage amount Vhc_0. In this example, the normal time HC storage amount estimation means 37 obtains the HC storage amount per unit time based on the catalyst temperature Tdoc estimated using the first exhaust temperature sensor 17, and the oxidation catalyst is used as the HC storage amount. By multiplying the capacity of 11, the HC occlusion amount per unit time in the entire oxidation catalyst 11 is obtained. Therefore, the HC storage amount per unit time obtained is divided by the calculation cycle t to obtain the HC storage amount for each calculation cycle t, and this is integrated to obtain the normal HC storage amount.

The required oxygen amount calculating means 39 calculates the required oxygen amount Vo ₂ _0 for oxidizing the HC for the normal HC storage amount Vhc_0 estimated by the normal HC storage amount estimation means 37 by calculation. For example, when the internal combustion engine 1 is a diesel engine, the theoretical air-fuel ratio is 14.5. Therefore, the intake air amount A to the internal combustion engine 1 is A = 14.5 × fuel injection amount (Q). Therefore, if the oxygen mass concentration in the air is α, the required oxygen amount Vo _{2 —} 0 for oxidizing the HC of the normal HC storage amount Vhc — 0 can be calculated using the following equation (1).

Vo _{2 —} 0 = α × 14.5 × Vhc — 0 (1)
Vo ₂ _0: Required oxygen amount (g)
α: Mass concentration of oxygen in air (%)
Vhc_0: Normal HC storage amount (g)

The actual oxygen consumption amount estimation means 41 is the actual oxygen consumption amount Vo consumed for oxidizing the HC actually stored by the oxidation catalyst 11 until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A at the cold start. ₂ Estimate _act. The actual oxygen consumption amount estimation means 41 of the oxidation catalyst function diagnostic apparatus according to the first embodiment uses the oxygen concentration O _{2 —} 0 upstream from the oxidation catalyst 11 estimated based on the target fuel injection amount Q, The actual oxygen consumption Vo ₂ —act is calculated by subtracting the downstream oxygen concentration O ₂ —D obtained based on the sensor signal S6 from the downstream oxygen concentration sensor 18 and integrating the obtained value ΔO _2. It is configured.

Since the upstream oxygen concentration O _{2 —} 0 obtained based on the target fuel injection amount Q can be regarded as the downstream oxygen concentration when oxygen is not consumed in the oxidation catalyst 11, the downstream oxygen concentration sensor The difference ΔO _{2 from the} downstream oxygen concentration O ₂ —D obtained based on 18 can be regarded as the amount of oxygen actually consumed by the oxidation catalyst 11. Therefore, as shown in FIG. 5, the shaded region obtained by integrating the difference ΔO ₂ between the upstream oxygen concentration O _{2 —} 0 and the downstream oxygen concentration O _{2 —} D is the actual oxygen consumption consumed by the oxidation catalyst 11. It represents Vo ₂ _act.

In addition, the actual oxygen consumption estimation means 41 of the oxidation catalyst function diagnostic apparatus according to the first embodiment is configured such that the oxygen concentration difference ΔO ₂ is the first threshold value after the oxidation catalyst 11 reaches the storage upper limit temperature Tdoc_A. Integration is started when ΔO ₂ —thre1 is reached, and thereafter, when the difference ΔO ₂ becomes equal to or smaller than the _second threshold value ΔO ₂ —thre2, the integration is ended. However, if the difference ΔO _{2 in the} oxygen concentration does not reach the first threshold value ΔO ₂ _thre1 even after a predetermined time has elapsed since the catalyst temperature Tdoc reached the storage upper limit temperature Tdoc_A, the actual oxygen consumption estimation means 41 The calculation of the actual oxygen consumption amount Vo ₂ _act by is interrupted.

The determination unit 43 determines the purification efficiency η of the oxidation catalyst 11 based on the ratio of the actual oxygen consumption amount Vo ₂ —act to the required oxygen amount Vo ₂ —0. That is, the difference between the required oxygen amount Vo _{2 —} 0 and the actual oxygen consumption amount Vo _{2 —} act is proportional to the difference between the normal HC storage amount Vhc — 0 and the actual HC storage amount Vhc_act actually stored in the oxidation catalyst 11. Therefore, the purification efficiency η of the oxidation catalyst 11 at that time can be continuously grasped based on the ratio of the actual oxygen consumption amount Vo ₂ —act to the required oxygen amount Vo ₂ —0.

  FIG. 6 is a graph showing the characteristics of the exhaust emission (mainly CO, HC) purification rate of the HC storage type oxidation catalyst 11. In a state where the catalyst temperature Tdoc is lower than the storage upper limit temperature Tdoc_A, HC in the exhaust is stored in the oxidation catalyst 11 and the HC concentration is reduced. On the other hand, when the catalyst temperature Tdoc rises and exceeds the storage upper limit temperature Tdoc_A, HC stored in the oxidation catalyst 11 and CO and HC in the exhaust start to be oxidized. In particular, when the catalyst temperature Tdoc becomes equal to or higher than the activation temperature Tdoc_LO, the oxidation efficiency of CO and HC is remarkably increased. At this time, a large amount of oxygen is consumed when the stored HC is oxidized.

Further, as shown in FIG. 6, the purification rate of the oxidation catalyst 11 changes according to the deterioration state of the oxidation catalyst 11. That is, in the region where the catalyst temperature Tdoc is equal to or lower than the storage upper limit temperature Tdoc_A, the purification rate (broken line) of the oxidation catalyst 11 undergoing deterioration is lower than the purification rate (solid line) of the oxidation catalyst 11 in the normal state. Therefore, in function diagnosis apparatus according oxidation catalyst to the first embodiment, the actual oxygen consumption Vo ₂ _act consumed by the oxidation catalyst 11 is estimated using the downstream oxygen concentration sensor 18, an oxidation catalyst 11 By comparing with the oxygen consumption model in the normal state (necessary oxygen amount Vo ₂ _0), the degree of decrease in the HC storage amount in the period until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A is estimated, and the oxidation catalyst 11 purification efficiency η is determined.

When the oxidation catalyst 11 is not deteriorated, the normal-time HC storage amount Vhc_0 is stored in the oxidation catalyst 11 until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A when the internal combustion engine 1 is cold started. Since it corresponds to the HC amount Vhc_act, the value of the actual oxygen consumption amount Vo ₂ —act is a value that approximates the required oxygen amount Vo ₂ —0.

On the other hand, when the oxidation catalyst 11 is deteriorated, the HC amount Vhc_act stored in the oxidation catalyst 11 until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A during the cold start of the internal combustion engine 1 is normal. It becomes less than the hour HC occlusion amount Vhc_0. Therefore, the value of the actual oxygen consumption amount Vo _{2 —} act consumed is smaller than the required oxygen amount Vo _{2 —} 0. By utilizing this fact, the purification efficiency η of the oxidation catalyst 11 at that time can be determined from the ratio of the actual oxygen consumption amount Vo ₂ —act to the required oxygen amount Vo ₂ —0.

  However, the purification efficiency η obtained by the calculation may cause an error due to the influence of various disturbances at the time of diagnosis, and it is often difficult to determine the purification efficiency η continuously. Therefore, in the oxidation catalyst function diagnostic apparatus according to the first embodiment, as shown in FIG. 7, the purification efficiency η is determined by dividing the purification efficiency η into a plurality of stages based on determination thresholds Thre1 to Thre3. Is configured to perform automatically.

(2) Flowchart Next, a function diagnosis method for the oxidation catalyst 11 executed by the electronic control device 30 as the function diagnosis device for the oxidation catalyst according to the first embodiment will be described with reference to the timing chart of FIG. This will be described with reference to the flowchart of FIG. The routine of the function diagnosis method described below is executed by interrupting the internal combustion engine 1 at all times or every predetermined number of times.

  First, in step S1 in FIG. 9, when the electronic control unit 30 detects the start of the internal combustion engine 1 based on the engine speed Ne or the like, the engine start flag is set to On (time t1 in FIG. 8). Next, in step S2, the electronic control unit 30 assumes that the oxidation catalyst 11 is normal, and is assumed to be occluded by the oxidation catalyst 11 until the catalyst temperature Tdoc reaches the occlusion upper limit temperature Tdoc_A. The HC occlusion amount Vhc_0 is estimated (period t1 to t2 in FIG. 8).

  The flowchart of FIG. 10 shows an example of a calculation method for estimating the normal HC storage amount Vhc_0. In this example, first, in step S11, the electronic control unit 30 determines whether or not the engine start flag is On and the temperature Tcl of the cooling water of the internal combustion engine 1 is equal to or lower than a threshold value Tcl0. If these conditions are not satisfied (in the case of No), the internal combustion engine 1 is not in the cold start state and the amount of HC in the exhaust gas is small, so the electronic control unit 30 proceeds to step S17. Reset the integrated value of HC occlusion amount and stop diagnosis.

  On the other hand, when it is determined in step S11 that the condition is satisfied (in the case of Yes), the electronic control unit 30 proceeds to step S12 and determines whether or not the catalyst temperature Tdoc is equal to or higher than the storage upper limit temperature Tdoc_A. If the catalyst temperature Tdoc is lower than the storage upper limit temperature Tdoc_A (in the case of No), since the HC is stored in the oxidation catalyst 11, the electronic control unit 30 proceeds to step S15, and based on the catalyst temperature Tdoc, After obtaining the HC occlusion amount at the current computation cycle t, the HC occlusion amount is integrated in step S16. The integration of the HC storage amount is performed by adding the HC storage amount in the current calculation cycle t to the stored integration value. After integrating the HC occlusion amount, the process returns to step S11 again and the steps so far are repeated.

  On the other hand, when the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A in Step S12 (in the case of Yes), the electronic control unit 30 proceeds to Step S13 and the stored integrated value is equal to or greater than the predetermined threshold value Vhc_thre1. It is determined whether or not. When the integrated value is less than the threshold value Vhc_thre1 (in the case of No), it is considered that the amount of HC that can be diagnosed with high accuracy is not exhausted. In this case also, the integrated value is reset in step S17 for diagnosis. Discontinue.

  In step S13, if the integrated value is greater than or equal to the threshold value Vhc_thre1 (in the case of Yes), the electronic control unit 30 proceeds to step S14, sets the integrated value to the normal HC storage amount Vhc_0, and sets the normal HC storage amount Vhc_0. The operation of is terminated.

Returning to FIG. 9, when the calculation of the normal HC storage amount Vhc_0 stored in the oxidation catalyst 11 by the time when the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A is completed, the electronic control unit 30 determines in step S3 that the normal HC A necessary oxygen amount Vo _{2 —} 0 required to oxidize the occlusion amount Vhc — 0 is obtained by calculation based on the above formula (1).

Then, in step S4, the electronic control unit 30 obtains by calculation the actual oxygen consumption Vo ₂ _act consumed in order to oxidize HC occluded actually the oxidation catalyst 11 (the period of t3~t4 in FIG. 8) .

The flowchart of FIG. 11 shows an example of a calculation method for obtaining the actual oxygen consumption amount Vo ₂ _act. In this example, the electronic control unit 30 first reads the target fuel injection amount Q in step S21, and then, in step S22, based on the target fuel injection amount Q read in step S21, the electronic control unit 30 is upstream of the oxidation catalyst 11. The oxygen concentration O _{2 —} 0 is obtained. Next, in step S23, the electronic control unit 30 obtains an oxygen concentration O ₂ _D downstream of the oxidation catalyst 11 based on the sensor value of the downstream oxygen concentration sensor 18.

Next, in step S24, the electronic control unit 30 determines whether or not the integration start flag is On. If integration start flag is not turned On (in the case of No), the process proceeds to step S28, the electronic control unit 30 is the difference delta O.D. ₂ from the oxygen concentration O ₂ _0 upstream by subtracting the oxygen concentration O ₂ _D downstream Then, it is determined whether or not it is equal to or larger than the first threshold value ΔO ₂ _thr1. If the difference ΔO _{2 in the} oxygen concentration is equal to or greater than the first threshold value ΔO ₂ _thr1 (in the case of Yes), it is estimated that oxygen has started to be consumed in the oxidation catalyst 11, and the electronic control unit 30 sets the integration start flag in step S29. After the On, the oxygen concentration difference ΔO ₂ is integrated over time in step S30, and the process returns to step S21.

On the other hand, when the difference ΔO ₂ in the oxygen concentration is less than the first threshold value ΔO ₂ _thr1 in step S28 (in the case of No), the electronic control unit 30 sets the counter value to +1 in step S31, and then proceeds to step S32. It is determined whether or not the counter value is equal to or greater than the threshold value C0. When the counter value is less than the threshold value C0 (in the case of No), the process directly returns to step S21. On the other hand, when the counter value reaches the threshold value C0 (in the case of Yes), after the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A, no oxygen consumption is observed even after a predetermined time has elapsed, and the diagnosis result The diagnosis is stopped because of the low reliability of

If the integration start flag has already been turned on in the above-described step S24 (in the case of Yes), the electronic control unit 30 proceeds to step S25 and the oxygen concentration difference ΔO ₂ is equal to or less than the second threshold value ΔO ₂ _thre2. It is determined whether or not. When the oxygen concentration difference ΔO ₂ exceeds the second threshold value ΔO ₂ _thre2 (in the case of No), since the oxygen is being consumed in the oxidation catalyst 11, the electronic control unit 30 proceeds to step S33. The oxygen consumption that is the difference ΔO ₂ in the advance oxygen concentration is integrated and stored, and the process returns to step S21.

On the other hand, when the oxygen concentration difference ΔO ₂ is less than the _second threshold value ΔO ₂ _thre2 (in the case of Yes), it is presumed that the consumption of oxygen in the oxidation catalyst 11 has ended, and therefore the electronic control unit 30 performs step S26. after the integration start flag to Off at, in step S27, the accumulated value stored by setting the actual oxygen consumption Vo ₂ _act, ends the actual oxygen consumption Vo ₂ _act estimation.

Returning to FIG. 9, when the calculation of the actual oxygen consumption amount Vo ₂ _act is completed in step S4 (at the time t4 in FIG. 8), the electronic control unit 30 in step S5, the required oxygen amount Vo ₂ _0 obtained in step S3 And the purification efficiency η of the oxidation catalyst 11 is determined using the actual oxygen consumption amount Vo ₂ _act obtained in step S4. In the oxidation catalyst function diagnostic apparatus according to the first embodiment, the ratio of the actual oxygen consumption amount Vo ₂ —act to the required oxygen amount Vo ₂ —0 is compared with the determination thresholds Thre1 to Thre3, and the purification efficiency η is The purification efficiency η is determined step by step by applying to one region.

As described above, the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the first embodiment can be used when it is assumed that the oxidation catalyst 11 has not deteriorated during the cold start of the internal combustion engine 1. The necessary amount of oxygen Vo ₂ _0 for oxidizing the normal HC storage amount Vhc_0 estimated to be stored in the period until the temperature Tdoc reaches the storage upper limit temperature Tdoc_A, and actually stored in the oxidation catalyst 11 during the same period The purification efficiency η of the oxidation catalyst 11 is determined based on the ratio with the actual oxygen consumption amount Vo ₂ —act consumed to oxidize the actual HC storage amount Vo ₂ —act. Therefore, the purification efficiency η of the oxidation catalyst 11 can be determined continuously or stepwise, and the self-diagnosis standard of the exhaust purification device can be satisfied.

  Further, according to the oxidation catalyst function diagnostic apparatus and the exhaust purification apparatus according to the first embodiment, the fuel injection control is intentionally changed without greatly changing the configuration of the conventional exhaust purification apparatus. The purification efficiency η of the oxidation catalyst 11 can be determined without forming a diagnostic mode.

Further, according to the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the first embodiment, the normal temperature in the period until the catalyst temperature Tdoc reaches the storage upper limit temperature Tdoc_A when the internal combustion engine 1 is cold started. Based on the ratio between the required oxygen amount Vo _{2 —} 0 for oxidizing the hourly HC storage amount Vhc — 0 and the actual oxygen consumption amount Vo _{2 —} act consumed to oxidize the actual stored HC storage amount Vo _{2 —} act Thus, the purification efficiency η of the oxidation catalyst 11 is determined. Therefore, it is possible to determine the purification efficiency of the oxidation catalyst 11 without forcibly increasing the HC in the exhaust gas by increasing the fuel injection amount. In addition, since the function diagnosis of the oxidation catalyst 11 is performed using the required oxygen amount Vo _{2 —} 0 and the actual oxygen consumption amount Vo _{2 —} act at the time of cold starting of the internal combustion engine 1, every time the internal combustion engine 1 is operated. An opportunity to perform at least one diagnosis can be secured.

  Further, according to the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the first embodiment, when the normal time HC storage amount Vhc_0 at the time of starting the internal combustion engine 1 is estimated, the oxidation catalyst 11 stores the storage upper limit temperature Tdoc_A. Therefore, the normal amount of HC occlusion Vhc_0 can be estimated relatively accurately and easily.

Further, according to the oxidation catalyst function diagnosis device and the exhaust purification device according to the first embodiment, the oxygen concentration O ₂ _0 upstream from the oxidation catalyst 11 obtained based on the fuel injection amount of the internal combustion engine can be obtained. Since the actual oxygen consumption O ₂ —D is calculated by integrating the difference with the oxygen concentration O ₂ —D downstream from the oxidation catalyst 11 obtained using the downstream oxygen concentration sensor 18, it becomes possible to relatively accurately calculate the actual oxygen consumption Vo ₂ _act consumed actually in the oxidation catalyst 11.

Further, according to the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the _first embodiment, when calculating the actual oxygen consumption amount Vo ₂ —act, the oxygen concentration difference ΔO ₂ is a predetermined first threshold value ΔO. ₂ _Thre1 starts the integration when it is above, by ending the integration when it becomes a second predetermined threshold delta O.D. ₂ _Thre2 less, when HC occluded in the oxidation catalyst 11 is started to be oxidized From this, it is possible to accurately calculate the amount of oxygen consumed until the oxidation is completed.

[Second Embodiment]
The oxidation diagnostic function diagnosis device according to the second embodiment of the present invention uses the oxygen consumption as in the case of the oxidation catalyst functional diagnosis device according to the first embodiment, as the basic principle of diagnosis. However, the oxidation catalyst function diagnosis apparatus according to the first embodiment is characterized in that the determination of the purification efficiency η of the oxidation catalyst is performed not in the cold start of the internal combustion engine but in a normal driving cycle. Is different. Hereinafter, the oxidation catalyst function diagnosis device and the exhaust purification device according to the second embodiment will be described focusing on differences from the oxidation catalyst function diagnosis device and the exhaust purification device according to the first embodiment.

  FIG. 12 is a diagram for schematically illustrating the configuration of an exhaust gas purification apparatus 10A for an internal combustion engine provided with the oxidation catalyst function diagnosis apparatus according to the second embodiment. FIG. 13 is a diagram for explaining the configuration of the oxidation catalyst function diagnostic apparatus according to the second embodiment. FIG. 14 to FIG. 16 are flowcharts for explaining a function diagnostic method for an oxidation catalyst executed by the function diagnostic apparatus for an oxidation catalyst according to the second embodiment.

1. Overall Configuration of Exhaust Gas Purification Device An exhaust gas purification device 10A for an internal combustion engine according to the second embodiment is provided with an upstream oxygen concentration sensor 19 upstream of the oxidation catalyst 11, and an electronic control device 50. The method for diagnosing the function of the oxidation catalyst according to the first embodiment differs from the configuration of the exhaust gas purification apparatus 10 for the internal combustion engine according to the first embodiment.

In the exhaust purification apparatus 10A according to the second embodiment, the upstream oxygen concentration sensor 19 uses a lambda sensor in the same manner as the downstream oxygen concentration sensor 18, and the electronic control unit 50 includes an upstream oxygen concentration sensor. Based on the 19 sensor values, the oxygen concentration O ₂ _U upstream of the oxidation catalyst 11 is calculated. In the oxidation catalyst function diagnostic apparatus according to the second embodiment, the upstream oxygen concentration sensor 19 is used together with the first exhaust temperature sensor 17 and the downstream oxygen concentration sensor 18 to purify the oxidation catalyst 11. The efficiency η is determined.

2. Electronic control device (function diagnostic device)
(1) Device Configuration FIG. 13 is a functional block diagram of a portion of the configuration of the electronic control device 50 related to fuel injection control and functional diagnosis of the oxidation catalyst 11. Similar to the electronic control device according to the embodiment, it is configured around a known microcomputer. The electronic control device 50 has a function as a function diagnostic device for the oxidation catalyst.

  The electronic control unit 50 includes target fuel injection amount calculation means 51, fuel injection valve control means 53, HC inflow amount estimation means 57, actual oxygen consumption amount estimation means 59, HC oxidation amount calculation means 61, and determination means. 63 and a fuel injection valve drive circuit 55 for energizing the fuel injection valve 5.

  The target fuel injection amount calculation means 51 and the fuel injection valve control means 53 can be basically configured in the same manner as in the electronic control device according to the first embodiment. However, the electronic control unit 50 according to the second embodiment is auxiliary injection that is performed after the main injection, and is capable of executing auxiliary injection for increasing the amount of HC in the exhaust gas. This auxiliary injection is so-called post-injection, and is mainly executed when PM collected in the particulate filter 12 is burned to regenerate the particulate filter 12.

  For this reason, the target fuel injection amount calculation means 51 calculates the auxiliary injection amount Vinj_HC together with the fuel injection amount Vinj_cmb for combustion such as pilot injection and main injection when the regeneration execution instruction of the particulate filter 12 is generated. Calculate. Further, the fuel injection valve control means 53 generates an instruction signal to be output to the fuel injection valve drive circuit 55 so that auxiliary injection is performed together with pilot injection and main injection.

  The regeneration execution instruction of the particulate filter 12 is, for example, when the difference between the pressure on the upstream side and the pressure on the downstream side of the particulate filter 12 reaches a predetermined threshold or when the amount of collected PM is accumulated. Generated when a predetermined threshold is reached.

  The HC inflow amount estimating means 57 estimates the HC inflow amount Vhc_in flowing into the oxidation catalyst 11 during the period in which the auxiliary injection by the fuel injection valve 5 is being executed. The HC inflow amount Vhc_in is an unburned portion of the total fuel injected into the internal combustion engine 1. The HC inflow amount estimation means 57 of the oxidation catalyst function diagnostic apparatus according to the second embodiment integrates the HC amount of unburned fuel during the period from the time when auxiliary injection is started to the time when it ends. The HC inflow amount Vhc_in is estimated.

Specifically, the relationship between the total HC amount Vhc_tot injected into the internal combustion engine 1, the HC amount Vhc_cmb for complete combustion, and the HC amount Vhc_nc for unburned can be expressed by the following equation (2). .
Vinj_tot = Vinj_cmb + Vinj_nc (2)

Here, when the upstream oxygen concentration sensor 19 is a lambda sensor, the sensor value λu of the lambda sensor is the ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio. For example, when the internal combustion engine 1 is a diesel engine, the sensor value λu of the lambda sensor can be expressed by the following equation (3).
λu = (A / Vinj_com) /14.5 (3)
A: Cylinder intake air amount

From the above equation (3), the HC amount Vinj_cmb for complete combustion can be expressed by the following equation (4).
Vinj_cmb = A / (14.5 × λu) (4)

Therefore, from the above equations (2) and (4), the HC amount Vinj_nc for the unburned amount is expressed as follows using the HC total amount Vinj_tot, the intake air amount A, and the sensor value λu of the upstream oxygen concentration sensor 19. (5) can be calculated.
Vinj_nc = Vinj_tot-A / (14.5 × λu) (5)

  Since the unburned HC amount Vinj_nc calculated by this equation (5) is the HC amount per calculation cycle t, the HC inflow amount estimating means 57 of the oxidation catalyst function diagnostic device according to the second embodiment. Estimates the HC inflow amount Vhc_in by integrating the unburned HC amount Vinj_nc calculated by the above equation (5) during a predetermined period.

Actual oxygen consumption estimating means 59 estimates the actual actual oxygen consumption Vo ₂ _act consumed by the oxidation catalyst 11. The actual oxygen consumption amount Vo _{2 —} act consumed in the oxidation catalyst 11 can be estimated by integrating the difference ΔO ₂ between the upstream oxygen concentration O _{2 —} U and the downstream oxygen concentration O _{2 —} D. The upstream oxygen concentration O ₂ —U and the downstream oxygen concentration O ₂ —D can be obtained based on the sensor values of the upstream oxygen concentration sensor 19 and the downstream oxygen concentration sensor 18, respectively.

The HC oxidation amount estimation means 61 estimates the HC oxidation amount Vhc_act actually oxidized in the oxidation catalyst 11 based on the actual oxygen consumption amount Vo ₂ —act estimated by the actual oxygen consumption amount estimation means 59. Specifically, when the internal combustion engine 1 is a diesel engine, the theoretical air-fuel ratio = intake air amount A / fuel amount F = 14.5, and oxygen amount = oxygen mass concentration α × intake air amount A. and HC oxidation amount Vhc_act oxidized by the oxidation catalyst 11, the relationship between the actual oxygen consumption Vo ₂ _act consumed for oxidation of the HC can be represented by the following formula (6).
(Vo ₂ _act / oxygen mass concentration α) /Vhc_act=14.5 (6)

That, HC oxidation amount estimating means 61 calculates the HC oxidation amount Vo ₂ _act by the following equation (7).
Vo ₂ _act = 14.5 × oxygen mass concentration α × Vhc_act (7)

  The determination unit 61 determines the purification efficiency η of the oxidation catalyst 11 based on the ratio of the HC oxidation amount Vhc_act estimated by the HC oxidation amount estimation unit 61 to the HC inflow amount Vhc_in estimated by the HC inflow amount estimation unit 57. To do. That is, the purification efficiency η of the oxidation catalyst 11 at that time can be continuously grasped by the ratio of the oxidized HC amount of the HC amount flowing into the oxidation catalyst 11.

  The oxidation catalyst function diagnostic apparatus according to the first embodiment includes a catalyst temperature Tdoc that is equal to or lower than the upper limit storage temperature Tdoc_A among the exhaust emission purification efficiency characteristics of the oxidation catalyst 11 shown in FIG. The function diagnosis device for the oxidation catalyst according to the second embodiment is used to perform the function diagnosis of the oxidation catalyst 11 in the region where the catalyst is occluded. The catalyst temperature Tdoc is higher than the normal activation temperature Tdoc_LO. The function diagnosis of the oxidation catalyst 11 is performed in a region where HC is oxidized by the oxidation catalyst 11.

As shown in FIG. 6, in the region where the catalyst temperature Tdoc is equal to or higher than the storage upper limit temperature Tdoc_A, the purification rate (broken line) of the oxidation catalyst 11 in which the deterioration is progressing is the purification rate (solid line) of the oxidation catalyst 11 in the normal state. Compared to lower. At the same time, the activation temperatures Tdoc_LO ′ and Tdoc_LO ″ of the oxidation catalyst 11 in which the deterioration has progressed rise compared to the activation temperature Tdoc_LO of the oxidation catalyst 11 in the normal state. That is, the purification efficiency η of the oxidation catalyst 11 changes depending on the deterioration state of the oxidation catalyst 11. Therefore, in the oxidation catalyst function diagnosis apparatus according to the _second embodiment, the HC oxidation amount Vhc_act is estimated from the actual oxygen consumption amount Vo 2_act consumed by the oxidation catalyst 11, and compared with the HC inflow amount Vhc_in. Then, the purification efficiency η of the oxidation catalyst 11 is determined.

  However, the purification efficiency η obtained by the calculation may cause an error due to the influence of various disturbances at the time of diagnosis, and it is often difficult to determine the purification efficiency η continuously. Therefore, in the oxidation catalyst function diagnostic apparatus according to the second embodiment, as shown in FIG. 7, the determination of the purification efficiency η is performed by dividing the purification efficiency η into a plurality of stages based on the determination thresholds Thre1 to Thre3. Is configured to perform automatically.

(2) Flowchart Next, the function diagnosis method for the oxidation catalyst 11 executed by the electronic control unit 50 as the function diagnosis apparatus for the oxidation catalyst according to the second embodiment is shown in the flowcharts of FIGS. I will explain. The routine of the function diagnosis method described below is executed at all times or by interrupting at predetermined intervals during the operation of the internal combustion engine 1.

  First, in step S41 of FIG. 14, the electronic control unit 50 determines that the catalyst temperature Tdoc of the oxidation catalyst 11 is equal to or higher than the normal activation temperature Tdoc_LO, and then starts auxiliary injection in step S42. For example, whether or not to start the auxiliary injection is determined by whether or not it is the regeneration time of the particulate filter 12, and for example, the differential pressure between the upstream side and the downstream side of the particulate filter 12, or the estimated collection of PM It is determined based on the amount. After starting the auxiliary injection, the electronic control unit 50 estimates the HC inflow amount Vhc_in flowing into the oxidation catalyst 11 during a predetermined period in step S43.

  The flowchart of FIG. 15 shows an example of a calculation method for estimating the HC inflow amount Vhc_in. In this example, the electronic control unit 30 first starts a timer in step S51, and then reads the lambda value λu, the intake air amount A, and the target fuel injection amount Q detected by the upstream oxygen concentration sensor 19 in step S52. . Further, in step S53, the electronic control unit 50 calculates the HC inflow amount in the current calculation cycle t from the above equation (5) based on the information read in step S52.

  Next, after integrating the HC inflow amount in step S54, the electronic control unit 50 determines in step S55 whether or not the timer value has reached a predetermined threshold value T0. The value of the threshold value T0 that defines the predetermined period can be set to an optimum value so that the HC inflow amount Vhc_in can be obtained to the extent that the diagnostic accuracy is ensured.

  When the timer value has not reached the threshold value T0 (in the case of No), the process returns to step S52 and the steps so far are repeated. On the other hand, when the timer value reaches the threshold value T0 (in the case of Yes), the process proceeds to step S56, and the electronic control unit 50 determines whether or not the stored integrated value is equal to or greater than a predetermined threshold value Vhc_in_thre1. . When the integrated value is less than the threshold value Vhc_in_thre1 (in the case of No), it is considered that an HC inflow amount sufficient for accurate diagnosis is not obtained, so the integrated value is reset in step S58 and the diagnosis is stopped.

  If the integrated value is greater than or equal to the threshold value Vhc_in_thre1 in step S56 (Yes), the electronic control unit 50 proceeds to step S57, sets the integrated value to the HC inflow amount Vhc_in, and ends the estimation of the HC inflow amount Vhc_in. To do.

Returning to FIG. 14, in parallel with the estimation of the HC inflow amount Vhc_in in step S <b> 43, in step S <b> 44, the electronic control unit 50 calculates the actual oxygen consumption amount Vo ₂ _act consumed for oxidizing HC in the oxidation catalyst 11. Calculate by calculation.

The flowchart of FIG. 16 shows an example of a calculation method for obtaining the actual oxygen consumption amount Vo ₂ _act. In this example, the electronic control unit 50 first starts a timer in step S61, and then in step S62, based on the sensor value of the upstream oxygen concentration sensor 19, the oxygen concentration O ₂ _U upstream of the oxidation catalyst 11 is detected. Ask for. Next, in step S63, the electronic control unit 50 obtains an oxygen concentration O ₂ _D downstream of the oxidation catalyst 11 based on the sensor value of the downstream oxygen concentration sensor 18.

Next, the electronic control unit 50 obtains a difference ΔO ₂ obtained by subtracting the downstream oxygen concentration O ₂ —D from the upstream oxygen concentration O ₂ —U in step S64, and then in step S65, the oxygen concentration difference ΔO _2. The time is accumulated.

Next, the electronic control unit 50 determines whether or not the timer value has reached a predetermined threshold value T0 in step S66. When the timer value has not reached the threshold value T0 (in the case of No), the process returns to step S62 and the steps so far are repeated. On the other hand, when the timer value reaches the threshold value T0 (in the case of Yes), the process proceeds to step S67, the electronic control unit 50 stores the integrated value stored as the actual oxygen consumption Vo ₂ _act, the actual The estimation of the oxygen consumption amount Vo ₂ _act is finished.

Returning to FIG. 14, when the calculation of the actual oxygen consumption amount Vo ₂ _act is completed in step S44, the electronic control unit 50 in step S45, based on the actual oxygen consumption amount Vo ₂ _act obtained in step S44, From 7), the HC oxidation amount Vhc_act oxidized by the oxidation catalyst 11 in a predetermined period is estimated.

  Next, in step S46, the electronic control unit 50 determines the purification efficiency η of the oxidation catalyst 11 using the HC inflow amount Vhc_in obtained in step S43 and the HC oxidation amount Vhc_act obtained in step S45. In the oxidation catalyst function diagnostic apparatus according to the second embodiment, the ratio of the HC oxidation amount Vhc_act to the HC inflow amount Vhc_in is compared with the determination thresholds Thre1 to Thre3, and the purification efficiency η is applied to four regions. The purification efficiency η is determined step by step.

As described above, the oxidation catalyst function diagnosis device and the exhaust purification device according to the second embodiment are configured so that the HC inflow amount Vhc_in flowing into the oxidation catalyst 11 during a predetermined period during the operation of the internal combustion engine 1 and the upstream on the basis of the ratio of the HC oxidation amount Vhc_act in a predetermined period that is estimated based on the difference delta O.D. ₂ the side oxygen concentration O ₂ _U and downstream oxygen concentration O ₂ _D, to determine the purification efficiency η of the oxidation catalyst 11 It is configured. Therefore, the purification efficiency η of the oxidation catalyst 11 can be determined continuously or stepwise, and the self-diagnosis standard of the exhaust purification device can be satisfied.

  Further, according to the oxidation catalyst function diagnosis device and the exhaust purification device according to the second embodiment, the fuel injection control is intentionally changed without greatly changing the configuration of the conventional exhaust purification device. The purification efficiency η of the oxidation catalyst 11 can be determined without forming a diagnostic mode.

  Further, according to the oxidation catalyst function diagnosis device and the exhaust purification device according to the second embodiment, the oxidation catalyst is utilized by using the time when the HC inflow amount Vhc_in increases due to the auxiliary injection in the regeneration control of the particulate filter 12. 11 purification efficiency η is determined. Therefore, it is possible to determine the purification efficiency η of the oxidation catalyst 11 without increasing the fuel injection amount for diagnosis. In addition, since the function diagnosis of the oxidation catalyst 11 is performed using the regeneration time of the particulate filter 12, a regular diagnosis opportunity can be secured.

Further, according to the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the second embodiment, the upstream oxygen concentration O ₂ _U obtained by using the upstream oxygen concentration sensor 19 and the downstream oxygen concentration sensor 18. Since the HC oxidation amount Vhc_act is calculated based on the actual oxygen consumption amount O ₂ _D obtained by integrating the difference ΔO ₂ with the downstream oxygen concentration O ₂ _D obtained using It is possible to relatively accurately calculate the HC oxidation amount Vhc_act actually oxidized.

[Other embodiments]
The oxidation catalyst function diagnosis device and the exhaust purification device according to the first and second embodiments described above show one aspect of the present invention and do not limit the present invention. The form can be arbitrarily changed within the scope of the present invention. The oxidation catalyst function diagnosis apparatus and the exhaust purification apparatus according to the first and second embodiments can be modified as follows, for example.

(1) The constituent elements constituting the exhaust system of the internal combustion engine described in the first and second embodiments, the set values and setting conditions of the electronic control units 30 and 50 are merely examples, and can be arbitrarily changed. Is possible.

(2) In the oxidation catalyst function diagnosis device and the exhaust gas purification device according to the first embodiment, the purification efficiency of the oxidation catalyst 11 based on the ratio between the required oxygen amount Vo _{2 —} 0 and the actual oxygen consumption amount Vo _{2 —} act. Although the determination of η is performed, the purification efficiency η of the oxidation catalyst 11 may be determined by replacing the normal HC storage amount Vhc_0 and the actual HC storage amount Vhc_act. By making such a determination, it is possible to obtain the same effect as that of the oxidation catalyst function diagnosis device according to the first embodiment.

(3) In the oxidation catalyst function diagnostic apparatus and the exhaust purification apparatus according to the second embodiment, the period until the timer value passes the predetermined threshold T0 is determined as the predetermined period. May be defined as a period until the HC inflow amount Vhc_in reaches a predetermined threshold. Or you may define the execution period of regeneration control of a particulate filter as a predetermined period. By configuring in this way, it is possible to obtain the same effects as those of the oxidation catalyst function diagnosis apparatus according to the second embodiment.

1: internal combustion engine, 3: exhaust pipe, 5: fuel injection valve, 10, 10A: exhaust purification device, 11: oxidation catalyst, 12: particulate filter, 13: NO _x purification catalyst, 15: second exhaust temperature sensor , 17: first exhaust temperature sensor, 18: downstream oxygen concentration sensor, 19: upstream oxygen concentration sensor, 20: reducing agent supply device, 23: pump, 25: reducing agent injection valve, 30: electronic control device ( Function diagnosis device), 31: target fuel injection amount calculation means, 33: fuel injection valve control means, 35: fuel injection valve drive circuit, 37: normal time HC storage amount estimation means, 39: required oxygen amount calculation means, 41: Actual oxygen consumption estimation means, 43: determination means, 50: electronic control device (function diagnostic device), 51: target fuel injection amount calculation means, 53: fuel injection valve control means, 55: fuel injection valve drive circuit, 57: HC inflow estimation Stage, 59: actual oxygen consumption calculating means, 61: HC oxidation amount estimating means, 63: determination means

Claims (8)

In the function diagnostic device for an oxidation catalyst for diagnosing the purification efficiency of the HC storage type oxidation catalyst provided in the exhaust passage of the internal combustion engine,
Assuming that the oxidation catalyst has not deteriorated, normal time HC storage amount estimation means for estimating a normal time HC storage amount stored in the oxidation catalyst during a predetermined period;
A required oxygen amount calculating means for calculating a required oxygen amount for oxidizing HC corresponding to the normal HC storage amount;
Actual oxygen consumption estimation means for estimating the actual oxygen consumption consumed to oxidize the HC actually stored in the predetermined period;
A determination means for determining a purification efficiency of the oxidation catalyst based on a ratio between the required oxygen amount and the actual oxygen consumption amount;
An oxidation catalyst function diagnostic device comprising:   2. The oxidation catalyst function diagnosis apparatus according to claim 1, wherein the predetermined period is a period from a cold start of the internal combustion engine until the oxidation catalyst reaches an activation temperature.   The normal-time HC storage amount estimation means estimates the normal-time HC storage amount by integrating the instantaneous storage amount until the oxidation catalyst reaches an activation temperature when the internal combustion engine is cold-started. The function diagnostic apparatus for an oxidation catalyst according to claim 1 or 2.   The normal-time HC storage amount estimation means obtains the instantaneous storage amount according to an exhaust gas temperature upstream of the oxidation catalyst detected by using an exhaust gas temperature sensor. The function diagnostic apparatus for an oxidation catalyst according to claim 1.   The actual oxygen consumption estimation means calculates the difference between the oxygen concentration upstream of the oxidation catalyst and the oxygen concentration downstream of the oxidation catalyst, which is obtained based on the fuel injection amount of the internal combustion engine. The function diagnostic apparatus for an oxidation catalyst according to any one of claims 1 to 4, wherein the actual oxygen consumption is estimated by integration.   The actual oxygen consumption estimation means starts the integration when the difference between the oxygen concentration on the upstream side and the oxygen concentration on the downstream side is equal to or greater than a predetermined first threshold, and 6. The function diagnosis apparatus for an oxidation catalyst according to claim 1, wherein the integration is terminated when the difference becomes equal to or less than a predetermined second threshold value. In the function diagnostic device for an oxidation catalyst for diagnosing the purification efficiency of the HC storage type oxidation catalyst provided in the exhaust passage of the internal combustion engine,
HC inflow amount estimating means for estimating an HC inflow amount flowing into the oxidation catalyst during a predetermined period;
Actual oxygen consumption estimation means for calculating actual oxygen consumption actually consumed to oxidize HC with the oxidation catalyst during the predetermined period;
HC oxidation amount estimation means for estimating the HC oxidation amount actually oxidized by the oxidation catalyst during the predetermined period based on the actual oxygen consumption amount;
Determination means for determining the purification efficiency of the oxidation catalyst based on the ratio of the HC inflow amount and the HC oxidation amount;
An oxidation catalyst function diagnostic device comprising:   An exhaust emission control device comprising the oxidation catalyst function diagnosis device according to any one of claims 1 to 7.

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