JP6319282B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to a control device for a diesel engine provided with a catalyst in an exhaust pipe.

Conventionally, sulfur oxides adsorbed on a catalyst provided in an exhaust pipe of a diesel engine (referred to as SO ₂ or SO ₃ , hereinafter collectively referred to as “SOx” unless they are distinguished below) are periodically desorbed. It is known to perform temperature rise control. For example, Japanese Patent Application Laid-Open No. 2013-029038 is cited as a document related to temperature rise control. This publication discloses a technique for estimating the accumulated amount of SOx accumulated in the catalyst and, when the estimated accumulated amount reaches the required release amount, increasing the bed temperature of the catalyst and controlling it to 500 to 550 ° C. Has been. According to this publication, when the bed temperature is less than 500 ° C., SOx is not released from the catalyst, and when the bed temperature is 500 to 550 ° C., SOx is released from the catalyst at a low concentration, and the bed temperature exceeds 600 ° C. The catalyst has the characteristic that SOx is released at a high concentration from the catalyst. Therefore, if the bed temperature of the catalyst having such characteristics is controlled to 500 to 550 ° C., the function can be recovered by desorbing SOx from the catalyst at a low concentration. It is also possible to suppress the generation of white smoke from SOx desorbed at a low concentration. That is, it is possible to achieve both the recovery of the function of the catalyst by the desorption of SOx and the suppression of the generation of white smoke due to this SOx.

JP 2013-029038 A Japanese Patent Laid-Open No. 11-081993

  The technique of the above publication pays attention to SOx already adsorbed on the catalyst. However, even during temperature rise control, SOx is discharged from the diesel engine and flows into the catalyst, so there is a high possibility that this SOx will be newly adsorbed on the catalyst. Then, it is expected that the technique of the above publication that does not consider such new adsorption of SOx does not necessarily have high accuracy in estimating the accumulated amount of SOx. Therefore, although the accumulated amount of SOx actually exceeds the required release amount, the temperature increase control may not be started because the estimated accumulated amount of SOx is lower than the required release amount. Further, even if the temperature rise control is started when the estimated accumulated amount of SOx reaches the required release amount after that, the actual accumulated amount of SOx at the start time is far beyond the required release amount. In some cases, recovery of the catalyst function may take time, or recovery of the catalyst function may be insufficient.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to recover the function of the catalyst by desorption of SOx and to suppress the generation of white smoke due to this SOx in the temperature rise control of the catalyst. Is to achieve both at a high level.

The present invention is an engine control device that executes control to increase the temperature of a purification device provided in an exhaust pipe of a diesel engine to a target temperature in a temperature range where SOx is desorbed from the purification device, and an inflow SOx amount estimating means SOx saturation rate estimation means, new adsorption SOx amount estimation means, slipping SOx amount estimation means, post-adsorption SOx distribution estimation means, new desorption SOx amount estimation means, final adsorption SOx distribution estimation means, slip-through SO ₃ amount estimating means, allowable desorption SO ₃ amount calculating means, and target temperature calculating means are provided.
The inflow SOx amount estimating means estimates the SOx amount flowing into the purification device as the inflow SOx amount for each cycle.
The SOx saturation rate estimation means includes an adsorption SOx distribution represented as a graph in which the amount of SOx adsorbed to the purification device at each temperature during the temperature increase of the purification device is related to the temperature of the purification device, and the temperature of the purification device The SOx saturation rate in the purification device is estimated for each cycle using a saturated SOx distribution represented as a graph in which the maximum amount of SOx adsorbed to the purification device at each temperature rising is related to the temperature of the purification device. To do. Here, the saturated SOx distribution corresponds to the temperature of the purifier in the current estimation cycle of the SOx saturation rate.
The new adsorption SOx amount estimation means estimates, based on the inflow SOx amount and the SOx saturation rate, the SOx amount that flows into the purification device and is newly adsorbed to the purification device as a new adsorption SOx amount for each cycle. .
The slip-through SOx amount estimation means estimates the amount of SOx that flows into the purification device and slips through without being adsorbed by the purification device as the slip-through SOx amount for each cycle, using the new adsorption SOx amount.
The post-adsorption SOx distribution estimation means estimates the SOx distribution after the new SOx is adsorbed on the purification device as the post-adsorption SOx distribution for each cycle, using the new adsorption SOx amount.
The new desorption SOx amount estimation means estimates the SOx amount newly desorbed from the purification device for each cycle as the new desorption SOx amount using the post-adsorption SOx distribution and the temperature of the purification device.
The final adsorption SOx distribution estimating means reflects the amount of the new desorption SOx in the post-adsorption SOx distribution, and sets the SOx distribution after desorption of new SOx from the purification device as the final adsorption SOx distribution for each cycle. presume.
The slipping SO ₃ amount estimation means includes a conversion rate map representing a relationship between a conversion rate of SO ₂ converted to SO ₃ in the purification device and a temperature of the purification device, a temperature of the purification device in the current estimation cycle, and the slipped and SOx amount, using the the purifier and flows in the form of SOx slipped through SO ₃ amount discharged in the form of SO ₃ to pass through without being adsorbed on the purifying device cycle as SO ₃ weight Estimate every time.
The allowable desorption SO ₃ amount calculation means uses the SO ₃ amount downstream of the purification device corresponding to the restriction on sulfate white smoke and the slip-through SO ₃ amount to allow SO to be desorbed from the purification device. ₃ amounts are calculated for each cycle as the allowable desorption SO ₃ amount.
The target temperature calculation means calculates the target temperature for each cycle using the final adsorption SOx distribution and the allowable desorption SO ₃ amount so that the SO ₃ concentration downstream of the purification device satisfies the constraint.
Further, the SOx saturation rate estimating means corresponds to a total saturated SOx amount corresponding to the area of the saturated SOx distribution and an area obtained by removing an overlapping portion of the saturated SOx distribution and the adsorption SOx distribution from the saturated SOx distribution. The SOx saturation rate is calculated using the total adsorption margin SOx amount.
Further, the post-adsorption SOx distribution estimating means reflects the final adsorption SOx distribution estimated in the previous estimation cycle in the new adsorption SOx amount, and estimates the post-adsorption SOx distribution in the current estimation cycle.

  In the present invention, the purification device may include a filter that collects particulates flowing through the exhaust pipe. In this case, the control for increasing the temperature to the target temperature may be started when the estimated value of the amount of fine particles collected by the filter reaches the removal request amount.

According to the present invention, inflow SOx amount estimation means, SOx saturation rate estimation means, new adsorption SOx amount estimation means, slip-through SOx amount estimation means, post-adsorption SOx distribution estimation means, and new desorption SOx amount estimation means And the final adsorption SOx distribution estimation means, the slip-through SO ₃ amount estimation means, the allowable desorption SO ₃ amount calculation means, and the target temperature calculation means, so that the SOx adsorption state on the catalyst is accurately grasped for each cycle. It becomes possible. Therefore, in the temperature rise control of the catalyst, it is possible to achieve both a restoration of the function of the catalyst by desorption of SOx and a suppression of the generation of white smoke due to this SOx at a high level.

It is a figure which shows the system configuration | structure of embodiment of this invention. It is a figure for demonstrating adsorption | suction and desorption of SOx in DOC22a. It is a functional block diagram which shows the logic for calculating target bed temperature Ttrg. It is a figure for demonstrating adsorption | suction SOx distribution and saturated SOx distribution. It is a figure for demonstrating the problem of the estimation method of the SOx saturation rate using adsorption | suction SOx distribution and saturated SOx distribution. It is a figure for demonstrating the relationship between a reference | standard saturation SOx distribution and the saturation SOx distribution after correction | amendment. It is a diagram for explaining the total adsorption margin SO ₂ amount. It is a figure for demonstrating the relationship between new adsorption | suction SOx amount and slip-through SOx amount. It is a figure for demonstrating adsorption rate map. It is a figure for demonstrating SOx distribution after adsorption | suction. It is a figure for demonstrating the detachable total SOx amount. It is a figure for demonstrating the relationship between final adsorption | suction SOx distribution and SOx distribution after adsorption | suction. It is a diagram for explaining the SO ₃ conversion rate map. Acceptable is a diagram for explaining the elimination SO ₃ amount. It is a figure for demonstrating target bed temperature Ttrg. It is a figure for demonstrating the effect by this Embodiment.

[Description of system configuration]
FIG. 1 is a diagram showing a system configuration according to an embodiment of the present invention. The system shown in FIG. 1 includes a diesel engine 10 (hereinafter also simply referred to as “engine 10”) mounted on a vehicle. Each cylinder of the engine 10 is provided with an injector 12 for injecting light oil as fuel. Although the engine 10 depicted in FIG. 1 is an in-line four-cylinder engine, the number of cylinders and the cylinder arrangement of the engine 10 are not particularly limited. FIG. 1 also depicts one of the four injectors 12.

An exhaust manifold 14 of the engine 10 is connected to an inlet of an exhaust turbine 16 a of a turbocharger 16. The exhaust turbine 16 a is connected to a compressor 16 b provided in the intake pipe 18. The compressor 16b is driven by the rotation of the exhaust turbine 16a to supercharge intake air. An exhaust pipe 20 is connected to the outlet of the exhaust turbine 16a. An exhaust gas purification device 22 is provided in the exhaust pipe 20. The exhaust purification device 22 includes a DOC (Diesel Oxidation Catalyst) 22a and a DPF (Diesel Particulate Filter) 22b. The DOC 22a is a catalyst having a function of oxidizing hydrocarbons (HC) and carbon monoxide (CO) in exhaust gas and converting them into water (H ₂ O) and carbon dioxide (CO ₂ ). The DPF 22b is a filter that collects particulates (PM) contained in the exhaust gas. A fuel addition valve 24 for adding fuel common to the injector 12 to the exhaust pipe 20 is provided upstream of the exhaust purification device 22.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 30 as a control device. The ECU 30 includes a RAM (Random Access Memory), a ROM (Read Only Memory), a CPU (Central Processing Unit), and the like. The ECU 30 captures and processes signals from various sensors mounted on the vehicle. The various sensors include an air flow meter 32 provided in the vicinity of the inlet of the intake pipe 18, a temperature sensor 34 for detecting the outlet temperature of the DOC 22a, and a differential pressure sensor 36 for detecting a pressure difference upstream and downstream of the DPF 22b. ECU30 processes the signal of each taken-in sensor, and operates various actuators according to a predetermined control program. The actuator operated by the ECU 30 includes the injector 12 and the fuel addition valve 24 described above.

[Regeneration control of DPF 22b]
In the present embodiment, regeneration control of the DPF 22b (hereinafter also referred to as “PM regeneration control”) is performed as engine control by the ECU 30. The PM regeneration control is control for adding fuel from the fuel addition valve 24 when the estimated value of PM collected by the DPF 22b reaches the removal request amount. For example, when the pressure difference detected by the differential pressure sensor 36 reaches a predetermined value, it can be determined that the estimated value of PM has reached the required removal amount. By adding fuel from the fuel addition valve 24, the added fuel is oxidized in the DOC 22a, and the bed temperature of the DPF 22b is raised to 600 ° C. or higher by this oxidation reaction heat. Thereby, the PM collected by the DPF 22b can be burned and removed, so that the collecting function of the DPF 22b can be recovered. The amount of fuel added from the fuel addition valve 24 for raising the bed temperature of the DPF 22b to 600 ° C. or higher (hereinafter referred to as “DPF fuel amount”) is determined based on a map associated with the bed temperature of the DPF. Such a map can be stored in, for example, the ROM of the ECU 30, and can be appropriately read according to the actual bed temperature of the DPF 22b.

[Problems in PM regeneration control]
By the way, the fuel and lubricating oil of diesel engines generally contain sulfur, and SOx is generated from such sulfur as the fuel burns. The same applies to the present embodiment, and SOx is generated with the combustion of fuel in the engine 10. The generated SOx is discharged from the engine 10, flows into the exhaust purification device 22, and is mainly adsorbed by the DOC 22a. However, when the bed temperature of the DOC 22a increases, the SOx adsorbed here starts to desorb. Although it varies somewhat depending on the composition of the DOC 22a, SOx is desorbed from the DOC 22a and released downstream in the temperature range where PM regeneration control is performed.

The adsorption and desorption of SOx in the DOC 22a will be described with reference to FIG. As shown in this figure, the DOC 22a includes a coating material 22c that covers the surface of a base material (not shown) and a noble metal 22d (Pt, Pd, etc.). The noble metal 22d is dispersedly supported on the coating material 22c and serves as an active point when oxidizing HC and CO. However, SO ₂ in the exhaust is adsorbed on the noble metal 22d, or SO _{3 in} the exhaust is adsorbed on the coating material 22c. Part of the SO ₂ adsorbed on the noble metal 22d is desorbed from the noble metal 22d and returned to the exhaust, or oxidized on the noble metal 22d to become SO ₃ and adsorbed on the coating material 22c in the state of SO ₃ . In other words, the noble metal 22 d SO ₂ is adsorbed, the coating material 22c is SO ₃ and SO ₂ from the SO ₃ from the exhaust adsorption. In any case, the adsorption function of SOx inhibits the oxidation function of DOC 22a such as HC.

The SO ₃ adsorbed on the coating material 22c through the two paths described above is desorbed when the bed temperature of the coating material 22c increases. Moreover, since the conversion from SO ₂ to SO ₃ on the noble metal 22d is promoted by increasing the bed temperature of the coating material 22c, such SO ₃ is also detached from the coating material 22c. Therefore, by performing PM regeneration control, it is possible to recover not only the above-described DPF 22b collection function but also an oxidation function such as HC in the DOC 22a. However, as shown in FIG. 2, H ₂ SO ₄ is generated when SO ₃ desorbed from the coating material 22 c reacts with H ₂ O present in the exhaust pipe 20. And if the concentration of H ₂ SO ₄ exceeds a certain concentration, it becomes visible white smoke (sulfate white smoke), which may impair the commercial value of the vehicle equipped with the engine 10.

[Features of this embodiment]
If fuel is added from the fuel addition valve 24 so that the concentration of H ₂ SO ₄ in the exhaust downstream of the DOC 22a does not become too high, the generation of sulfate white smoke during PM regeneration control can be suppressed. Therefore, in the present embodiment, the target temperature of the DOC 22a bed temperature during PM regeneration control (hereinafter also referred to as “target bed temperature Ttrg”) so that the SO ₃ concentration downstream of the DOC 22a satisfies the restrictions on sulfate white smoke. And the amount of fuel added from the fuel addition valve 24 (hereinafter also referred to as “constraint satisfaction fuel amount”) is calculated based on the target bed temperature Ttrg. Such a restricted SO ₃ concentration (the upper limit value of the SO ₃ concentration downstream of the DOC 22a) can be stored in the ROM of the ECU 30, for example. When the amount of fuel for DPF is greater than the amount of fuel for constraint satisfaction, by adopting the amount of fuel for constraint satisfaction instead of the amount of fuel for DPF, oxidation of HC and the like in DOC 22a is satisfied while satisfying the constraints on sulfate white smoke. Function can be restored.

[Calculation logic of target bed temperature Ttrg]
FIG. 3 is a functional block diagram showing logic for calculating the target bed temperature Ttrg, and this is realized by the ECU 30. As shown in this figure, the ECU 30 includes an inflow SOx amount estimation unit M1, an SOx saturation rate estimation unit M2, a new adsorption SOx amount and slipping SOx amount estimation unit M3, a post-adsorption SOx distribution estimation unit M4, and a new removal. includes a release SOx amount estimation unit M5, a final suction SOx distribution estimating unit M6, and slipped SO ₃ amount estimating unit M7, the allowable desorption SO ₃ amount calculating section M8, and white smoke suppression target bed temperature calculation unit M9, the The target bed temperature Ttrg is calculated for each cycle (specifically, for each combustion cycle of the engine 10) using these elements M1 to M9. In the following description, elements M1 to M9 are simplified, and for example, the inflow SOx amount estimation unit M1 is also referred to as “estimation unit M1”.

  The estimation unit M1 estimates the amount of SOx flowing into the DOC 22a (hereinafter also referred to as “inflow SOx amount”). The “SOx flowing into the DOC 22a” in this specification includes not only the SOx that is generated by the engine 10 and discharged from here and flows into the DOC 22a, but also the fuel added from the fuel addition valve 24 at the DOC 22a. It is assumed that SOx generated along with the oxidation reaction and flowing on the DOC 22a is also included.

Specifically, the estimation unit M1 calculates the t th by the following equation (1) using the injected fuel amount (in-cylinder injection amount) from the injector 12 and the added fuel amount (exhaust addition amount) from the fuel addition valve 24 as variables. Estimate the inflow SOx amount in the second cycle. The fuel S concentration in equation (1) is the sulfur concentration in the fuel, and a detection value of a sulfur concentration sensor separately provided in the fuel supply system may be used, or a set value may be used.
Inflow SOx amount (exhaust addition amount (t), in-cylinder injection amount (t)) [μg / s] = inflow fuel amount (exhaust addition amount (t), in-cylinder injection amount (t)) [g / s] × Fuel S concentration [ppm] (1)

The inflow fuel amount (exhaust gas addition amount (t), in-cylinder injection amount (t)) in equation (1) is the amount of fuel in the t-th cycle that originated from “SOx flowing into DOC 22a”, It is calculated by the following equation (2) using the specific gravity of fuel (light oil specific gravity).
Inflow fuel amount (exhaust addition amount (t), in-cylinder injection amount (t)) [g / s] = (exhaust addition amount (t) [g / s] ÷ 1000 × light oil specific gravity [g / cm ³ ] + cylinder Internal injection amount (t) [g / s]) (2)
In the following description, the inflow SOx amount (exhaust addition amount (t), in-cylinder injection amount (t)) is also referred to as inflow SOx amount (t). The inflow fuel amount (exhaust gas addition amount (t), in-cylinder injection amount (t)) is also referred to as inflow fuel amount (t).

The estimation unit M2 estimates the SOx saturation rate (hereinafter also referred to as “SOx saturation rate”) in the DOC 22a. In the estimation of the SOx saturation rate, the amount of SOx adsorbed on the DOC 22a at each bed temperature during the rise in the bed temperature of the DOC 22a (hereinafter also referred to as “adsorbed SOx amount”) is represented as a graph related to the bed temperature of the DOC 22a. Distribution (hereinafter also referred to as “adsorption SOx distribution”) and the maximum amount of SOx adsorbed to the DOC 22a at each bed temperature during the rise in the bed temperature of the DOC 22a (hereinafter also referred to as “saturated SOx amount”). A distribution expressed as a graph related to temperature (hereinafter also referred to as “saturated SOx distribution”) is used. First, the adsorption SOx distribution and the saturated SOx distribution will be described with reference to FIG. 4 using SO ₃ as an example.

The data shown as “adsorbed SO ₃ amount” in FIG. 4 is collected by the following method. Specifically, first, a sufficient amount of SOx is adsorbed on the DOC 22a at the bed temperature indicated as "current temperature" in FIG. Subsequently, the amount of SO ₃ desorbed from the DOC 22a at each bed temperature while the bed temperature of the DOC 22a is rising is measured under the condition that the rising speed is constant. Then, a graph is created by associating this desorbed SO ₃ amount with the bed temperature of the DOC 22a. As a result, a distribution representing the amount of desorbed SO ₃ (hereinafter also referred to as “desorbed SO ₃ distribution”) can be obtained. A graph in which the amount of SO ₂ desorbed from the DOC 22a at each bed temperature while the bed temperature of the DOC 22a is rising is related to the bed temperature of the DOC 22a (hereinafter also referred to as “desorption SO ₂ distribution”) by the same method as this. You can also get Note that the SO ₃ desorbed from DOC22a, which to a may be directly measured by the sensor, to measure both using the sensor for detecting the SOx or SO _2, be calculated from these differences good _{(SO 3 = SOx-SO 2} ).

Here, SO ₃ desorbed from DOC22a in increased bed temperature of DOC22a is SO ₃ which actually adsorbed to DOC22a in bed temperature shown as "current temperature" in FIG. However, SO ₃ desorbed from DOC22a at some bed temperature, the bed is SO ₃ which could continue to adsorb to DOC22a up to temperature and, more could be adsorbed to DOC22a in that bed temperature It can also be considered SO ₃ . Based on this assumption, if the vertical axis of the desorption SO ₃ distribution described above is replaced with the amount of SO ₃ adsorbed on the DOC 22a at each bed temperature during the rise in the bed temperature of the DOC 22a, the “adsorption” shown in FIG. A graph of the “SO ₃ amount” data, that is, an adsorption SO ₃ distribution can be obtained. Then, the same method as this, it is possible to obtain an adsorption SO ₂ distribution.

Further, the data shown as “saturated SO ₃ amount” in FIG. 4 is collected by the same method as the “adsorption SO ₃ amount” data. Specifically, this “saturated SO ₃ amount” data is obtained from the SO 2 desorbed from the DOC 22a at each bed temperature (for example, at intervals of 5 ° C.) while the bed temperature of the DOC 22a is increasing under the condition that the rising speed is extremely low. _This corresponds to an amount of ₃ . Since the rising speed of the bed temperature of the DOC 22a is extremely low, this “saturated SO ₃ amount” data can be considered to be the maximum value of the amount of SO ₃ desorbed from the DOC 22a. Moreover, the assumption mentioned above is applicable to this maximum value. That is, it can be considered that the maximum amount of SO ₃ desorbed from the DOC 22a at a certain bed temperature is equal to the maximum amount of SO ₃ that can be adsorbed to the DOC 22a at the bed temperature. Replacing the vertical axis of the elimination SO ₃ distribution described above on the basis of this assumption the maximum amount of the SO _3, graph data shown in FIG. 4 "saturated SO ₃ amount", i.e., saturated SO ₃ distribution Can be obtained. A saturated SO ₂ distribution can also be obtained by a method similar to this.

Next, problems of the SOx saturation rate estimation method using the adsorption SOx distribution and the saturated SOx distribution will be described with reference to FIG. 5 in addition to FIG. As described above, the saturated SO ₃ distribution explained in FIG. 4 is obtained by desorbing SO ₃ adsorbed on the DOC 22a at the bed temperature indicated as “current temperature” in this figure while the bed temperature of the DOC 22a is rising. It is the created graph. Therefore, by dividing the total amount of the “adsorbed SO ₃ amount” data in FIG. 4 by the total amount of the “saturated SO ₃ amount” data in the same figure, the saturation rate of SO ₃ in the DOC 22a, that is, the SO ₃ saturation rate is obtained. Can be calculated. Further, the saturation rate of SO _{2 in} the DOC 22a, that is, the SO ₂ saturation rate can also be calculated by the same method as this.

  By the way, the above-mentioned “SOx flowing into the DOC 22a” is also a SOx that may be adsorbed to the DOC 22a. Here, the amount of SOx that flows into the DOC 22a and is newly adsorbed here has a correlation with the amount of SOx that is already adsorbed on the DOC 22a. Specifically, the amount of SOx that is already adsorbed on the DOC 22a is small. The amount of SOx newly adsorbed on the DOC 22a increases (see FIG. 9). In this regard, if the SOx saturation rate is estimated using the adsorption SOx distribution and the saturated SOx distribution, it is possible to determine how much SOx adsorption margin is in the DOC 22a.

  However, on the other hand, the amount of SOx that can be adsorbed to the DOC 22a is limited in the first place. Here, this adsorption limit amount correlates with the bed temperature of the DOC 22a. Specifically, the adsorption limit amount increases as the bed temperature of the DOC 22a becomes higher at a lower temperature side than a certain temperature, and at a higher temperature side than this temperature. It decreases as the floor temperature of the DOC 22a increases. FIG. 5 shows a problem caused by such an adsorption limit amount.

The data shown as “saturated SO ₃ amount” in FIG. 5 indicates that a sufficient amount of SOx is adsorbed to the DOC 22a at the bed temperature indicated as “current temperature” in this figure, and the bed temperature of the DOC 22a is increased at each bed temperature. The amount of SO ₃ desorbed from the DOC 22a corresponds to data measured under conditions where the rising speed is extremely low. On the other hand, the data shown as “adsorption SO ₃ amount” in this figure is the same data as the “adsorption SO ₃ amount” in FIG. As can be seen from FIG. 5, in the region where the bed temperature of the DOC 22a is low, the “adsorption SO ₃ amount” is lower than the “saturated SO ₃ amount”, but in the region where the bed temperature of the DOC 22a is high, It will be reversed.

When the reversal of the magnitude relationship between “adsorption SO ₃ amount” and “saturated SO ₃ amount” occurs, the DOC 22a is actually in a region where the bed temperature is low, and there is room to adsorb SO ₃ on the DOC 22a even in the bed temperature region. In spite of this, the value of the saturation rate of SO ₃ obtained by the above division exceeds 1 and there are cases where it is determined that the DOC 22a does not have such an adsorption margin. As described above, the method of simply dividing the total amount of “adsorbed SO ₃ amount” data as described in FIG. 4 by the total amount of “saturated SO ₃ amount” data may not be able to accurately calculate the SOx saturation rate. is there.

In view of the above-described problem, the estimation unit M2 calculates the SOx saturation rate (T ₂ (t ₂ (t) in the t-th cycle) by the following equation (3) using the current bed temperature T ₂ of the DOC 22a in the t-th cycle as a variable. ), T). Note that the current bed temperature T ₂ are, for example, it can be used detected value of the temperature sensor 34.
SOx saturation rate (T ₂ (t), t) = 1− (total adsorption margin amount (T ₂ (t), t) / total saturation amount (T ₂ (t), t)) (3)

The calculation process of the SOx saturation rate (T ₂ (t), t) in Expression (3) is as follows. First, the saturated SO ₂ distribution (T ₁ , T ₁ , T ₂ ) in the t-th cycle is calculated by the following equations (4) and (5) using the bed temperature T ₁ during the rise of the bed temperature of the DOC 22a and the current bed temperature T ₂ as variables. T ₂ (t), t) and saturated SO ₃ distribution (T ₁ , T ₂ (t), t) are respectively calculated.
Saturated SO ₂ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] = Standard saturated SO ₂ distribution × bed temperature corrected SO ₂ map (T ₂ (t)) [μg / ° C.] 4)
Saturated SO ₃ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] = Reference saturated SO ₃ distribution × bed temperature corrected SO ₃ map (T ₂ (t)) [μg / ° C.] 5)

The reference saturated SO ₂ distribution of the equation (4) is obtained by using the bed temperature (“current temperature” in FIGS. 4 and 5) when a sufficient amount of SOx is adsorbed by the DOC 22a as the reference bed temperature (for example, the above-described adsorption limit amount is This is a saturated SO ₂ distribution created as a maximum (bed temperature around 300 ° C.). The reference saturated SO ₃ distribution of the equation (5) is similar to this. The bed temperature correction SO ₂ map (T ₂ (t)) in Expression (4) is a map that defines a correction value for converting the reference saturated SO ₃ distribution into the saturated SO ₂ distribution at the current bed temperature T ₂ . The bed temperature correction SO ₃ map (T ₂ (t)) in the equation (5) is the same as this. Such criteria saturated SOx distribution and the correction map can be memorized for example in the ECU30 in the ROM, a read appropriately according currently bed temperature T _2.

The relationship between the reference saturated SOx distribution and the corrected saturated SOx distribution will be described with reference to FIG. 6 using SO ₂ as an example. Note that TL and TH on the horizontal axis in this figure are the temperature at which SO ₂ begins to desorb from the DOC 22a during the rise in the bed temperature of the DOC 22a (lower limit temperature), and the temperature at which SO ₂ finishes desorbing from the DOC 22a (upper limit temperature). Each corresponds. The difference of the three distribution shown in this figure, is currently in bed temperature T _2. That is, if the current floor temperature T ₂ is equal to the reference temperature, saturated SO ₂ distribution shape of the corrected coincides with the reference saturation SO ₂ distribution shape (middle). On the other hand, when the current bed temperature T ₂ is lower than the reference temperature (left side) or when the current bed temperature T ₂ is higher than the reference temperature (right side), the corrected saturation SO ₂ distribution shape is the reference saturation. It does not match the shape of the SO ₂ distribution. When the current bed temperature T ₂ is higher than the reference temperature (right side), the corrected saturated SO ₂ distribution shape is missing data on the lower temperature side than the current bed temperature T _2. It becomes a shape. The reason for this is currently the low temperature side than the bed temperature T ₂ are, the SOx that could have been of continuing to adsorb to DOC22a In this bed temperature range would otherwise, be due believed already desorbed from DOC22a .

Subsequently, the saturated SO ₂ distribution (T ₁ , T ₂ (t), t) calculated by the equation (4) is substituted into the following equation (6), and the total saturated SO ₂ amount (T ₂ (t), t) are calculated. Further, the saturated SO ₃ distribution (T ₁ , T ₂ (t), t) calculated by the equation (5) is substituted into the following equation (7) to calculate the total saturated SO ₃ amount in the t-th cycle. .

When the total saturated SO ₂ amount (T ₂ (t), t) and the total saturated SO ₃ amount (T ₂ (t), t) are calculated, these are substituted into the following equation (8), and the t-th cycle The total saturation amount at (T ₂ (t), t) is calculated.
Total saturation amount (T ₂ (t), t) = Total saturation SO ₂ amount (T ₂ (t), t) + Total saturation SO ₃ amount (T ₂ (t), t) (8)
In the following description, the total saturated SO ₂ amount (T ₂ (t), t) is also simply referred to as the total saturated SO ₂ amount (t). The total saturated SO ₃ amount (T ₂ (t), t) is also simply referred to as the total saturated SO ₃ amount (t). The total saturation amount (T ₂ (t), t) is also simply referred to as the total saturation amount (t).

When the total saturation amount (t) is calculated by the equation (8), the saturated SO ₂ distribution (T ₁ , T ₂ (t), t) and the final adsorption SO ₂ distribution in the t-th cycle estimated by the estimation unit M6. Substituting (T ₁ , t) into the following equation (9), the adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) in the t-th cycle is calculated. Further, the saturated SO ₃ distribution (T ₁ , T ₂ (t), t) and the final adsorption SO ₃ distribution (T ₁ , t) in the t-th cycle estimated by the estimation unit M6 are expressed by the following equation (10). And the adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) in the t-th cycle is calculated.
Adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] = Max {saturated SO ₂ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] − Final adsorption SO ₂ distribution (T ₁ , t) [μg / ° C.], 0} (9)
Adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] = Max {saturated SO ₃ distribution (T ₁ , T ₂ (t), t) [μg / ° C.] − Final adsorption SO ₃ distribution (T ₁ , t) [μg / ° C.], 0} (10)

なお、以下の説明においては、吸着余裕ＳＯ_２分布（Ｔ_１，Ｔ_２（ｔ），ｔ）を単に吸着余裕ＳＯ_２分布（ｔ）ともいう。また、吸着余裕ＳＯ_３分布（Ｔ_１，Ｔ_２（ｔ），ｔ）を単に吸着余裕ＳＯ_３分布（ｔ）ともいう。また、総吸着余裕ＳＯ_２量（Ｔ_２（ｔ），ｔ）を単に総吸着余裕ＳＯ_２量（ｔ）ともいう。また、総吸着余裕ＳＯ_３量（Ｔ_２（ｔ），ｔ）を単に総吸着余裕ＳＯ_３量（ｔ）ともいう。 Subsequently, the adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) calculated by the equation (9) is substituted into the following equation (11), and the total adsorption margin SO ₂ amount in the t-th cycle is calculated. (T ₂ (t), t) is calculated. Further, the adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) calculated by the equation (10) is substituted into the following equation (12), and the total adsorption margin SO ₃ amount in the t-th cycle ( T ₂ (t), t) is calculated.

In the following description, the adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) is also simply referred to as an adsorption margin SO ₂ distribution (t). The adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) is also simply referred to as an adsorption margin SO ₃ distribution (t). The total adsorption margin SO ₂ amount (T ₂ (t), t) is also simply referred to as the total adsorption margin SO ₂ amount (t). The total adsorption margin SO ₃ amount (T ₂ (t), t) is also simply referred to as the total adsorption margin SO ₃ amount (t).

The total adsorption margin SO ₂ amount (t) will be described with reference to FIG. The total adsorption margin SO ₃ amount (t) is the same as this. As shown in this figure, the total adsorption margin SO ₂ amount (t) may be a saturated SO ₂ distribution, expressed as the area excluding the overlapping portions of the adsorption SO ₂ distribution and saturated SO ₂ distribution. In addition, as shown as a region A in the distribution on the right side of this figure, the amount of SO ₂ adsorbed on the DOC 22a at each bed temperature during the rise of the bed temperature of the DOC 22a, that is, the amount of adsorbed SO ₂ is the maximum amount, that is, When the amount exceeds the saturated SO ₂ amount, it is considered that the DOC 22a is saturated, and thus is excluded from the calculation of the total adsorption margin SO ₂ amount (t). Further, in the distribution of the right, the reason why the low-temperature side of the data than the current floor temperature T ₂ is missing, is as described in FIG.

When the total adsorption margin SO ₂ amount (t) and the total adsorption margin SO ₃ amount (t) are calculated, these are substituted into the following equation (13) to obtain the total adsorption margin amount (T ₂ ) in the t-th cycle. (T), t) are calculated.
Total adsorption margin (T ₂ (t), t) = Total adsorption margin SO ₂ amount (t) + Total adsorption margin SO ₃ amount (t) (13)
Furthermore, if the total saturation amount (t) calculated by the equation (8) and the total adsorption margin amount (t) calculated by the equation (13) are substituted into the equation (3), the saturation rate (T ₂ (t) , T) can be calculated. In the following description, the saturation rate (T ₂ (t), t) is also simply referred to as the saturation rate (t).

  Returning to FIG. 3, the description of the calculation logic of the target bed temperature Ttrg will be continued. The estimation unit M3 is “SOx flowing into the DOC 22a” and the amount of SOx newly adsorbed to the DOC 22a (hereinafter also referred to as “new adsorbed SOx amount”), and “SOx flowing into the DOC 22a” and DOC 22a. The amount of SOx that slips through without being adsorbed on the surface (hereinafter also referred to as “the amount of slip-through SOx”) is estimated. First, the relationship between the new adsorption SOx amount and the slip-through SOx amount will be described with reference to FIG. As indicated by the arrows in this figure, the sum of the newly adsorbed SOx amount and the slip-through SOx amount becomes equal to the inflow SOx amount. This is because a part of “SOx flowing into the DOC 22a” is adsorbed on the DOC 22a, and the rest is not adsorbed on the DOC 22a.

Specifically, the estimation unit M3 calculates the new adsorption SOx amount by the following equation (14) using the inflow SOx amount (t) estimated by the estimation unit M1 and the saturation rate (t) estimated by the estimation unit M2 as variables. The estimated SOx amount is estimated by the following equation (15).
New adsorption SOx amount (inflow SOx amount (t), saturation rate (t)) [μg / s] = inflow SOx amount (t) × adsorption rate map (saturation rate (t)) (14)
Slip-through SOx amount (inflow SOx amount (t), saturation rate (t)) [μg / s] = inflow SOx amount (t) × {1−adsorption rate map (saturation rate (t))} (15)
In the following description, the new adsorption SOx amount (inflow SOx amount (t), saturation rate (t)) is also simply referred to as a new adsorption SOx amount (t). The slip-through SOx amount (inflow SOx amount (t), saturation rate (t)) is also simply referred to as a slip-through SOx amount (t).

The adsorption rate map of the formulas (14) and (15) is the saturation rate (t) in the ratio of SOx adsorbed to the DOC 22a (that is, the adsorption rate) in the “SOx flowing into the DOC 22a” in the t-th cycle. It is a map created based on the characteristic of changing depending on. As shown in FIG. 9, this characteristic is that the adsorption rate is high in the region where the saturation rate (t) is low, and the adsorption rate gradually decreases as the saturation rate (t) increases. Such a map, for example is stored in ECU30 the ROM can keep, can be read out as appropriate in accordance currently bed temperature T _2.

Returning to FIG. 3, the estimation unit M4 estimates the post-adsorption SOx distribution by reflecting the amount of new adsorption SOx estimated by the estimation unit M3 in the adsorption SOx distribution. The SOx distribution after adsorption will be described with reference to FIG. 10 using SO ₂ as an example. As shown in this figure, the post-adsorption SO ₂ distribution is updated to the final adsorption SO ₂ distribution in the previous cycle (for example, the (t−1) th cycle), and to the DOC 22a in the current cycle (for example, the tth cycle). It is estimated by adding a distribution representing the amount of SO ₂ adsorbed on (hereinafter also referred to as “new adsorbed SO ₂ distribution”).

Specifically, the estimation unit M4 firstly calculates the t-th number by the following equation (16) using the new adsorption SOx amount (t), the total adsorption margin amount (t), and the adsorption margin SO ₂ distribution (t) as variables. Calculate the new adsorption SO ₂ distribution in the cycle. Similar to the new adsorption SO ₂ distribution, the estimation unit M4 calculates a distribution representing the amount of SO ₃ newly adsorbed on the DOC 22a (hereinafter also referred to as “new adsorption SO ₃ distribution”) by the following equation (17). To do. Note that the suction afford SO ₂ distribution (t) and the total adsorption allowance (t), which is calculated in the estimation unit M2 are used.
New adsorption SO ₂ distribution (new adsorption SOx amount (t), adsorption margin SO ₂ distribution (t), total adsorption margin amount (t)) [μg / ° C.] = Adsorption margin SO ₂ distribution (t) [μg / ° C.] × {New adsorption SOx amount (t) / Total adsorption margin amount (t)} (16)
New adsorption SO ₃ distribution (new adsorption SOx amount (t), adsorption margin SO ₃ distribution (t), total adsorption margin amount (t)) [μg / ° C.] = Adsorption margin SO ₃ distribution (t) [μg / ° C.] × {New adsorption SOx amount (t) / Total adsorption margin amount (t)} (17)
In the following description, the new adsorption SO ₂ distribution (new adsorption SOx amount (t), adsorption margin SO ₂ distribution (t), total adsorption margin amount (t)) is simply referred to as new adsorption SO ₂ distribution (t). Also called. The new adsorption SO ₃ distribution (new adsorption SOx amount (t), adsorption margin SO ₃ distribution (t), total adsorption margin amount (t)) is also simply referred to as new adsorption SO ₃ distribution (t).

Subsequently, the estimation unit M4 substitutes the calculated new adsorption SO ₂ distribution and the final adsorption SO ₂ distribution (t−1) in the (t−1) -th cycle into the following equation (18) to obtain the post-adsorption SO 2 _Two distributions are calculated. Further, the calculated new adsorption SO ₃ distribution and the adsorption SO ₃ distribution (t−1) estimated by the estimation unit M6 in the (t−1) -th cycle are substituted into the following equation (19), and the post-adsorption SO ₃ Calculate the distribution.
Post-adsorption SO ₂ distribution (t) [μg / ° C.] = Final adsorption SO ₂ distribution (t−1) [μg / ° C.] + New adsorption SO ₂ distribution (t) [μg / ° C.] (18)
Post-adsorption SO ₃ distribution (t) [μg / ° C.] = Final adsorption SO ₃ distribution (t−1) [μg / ° C.] + New adsorption SO ₃ distribution (t) [μg / ° C.] (19)

  Returning to FIG. 3, the estimation unit M5 estimates the amount of SOx newly desorbed from the DOC 22a (hereinafter also referred to as “new desorption SOx amount”) based on the post-adsorption SOx distribution estimated by the estimation unit M4. .

Specifically, the estimation unit M5 first estimates the total amount of SOx that can be desorbed from the DOC 22a (hereinafter also referred to as “total desorbable SOx amount”). The total amount of detachable SOx will be described with reference to FIG. 11 using SO ₂ as an example. Note that TL and TH on the horizontal axis in this figure correspond to the above-described lower limit temperature and upper limit temperature, respectively. As shown in this figure, detachable total SOx amount, the current low temperature side than the floor temperature T _2, besides, than the lower limit temperature TL corresponds to the area of the post-adsorption SOx distribution of the high temperature side.

The total amount of SO ₂ that can be desorbed from DOC22a, i.e., removable total SO ₂ amount is calculated by the current equation of the bed temperature _{T 2} and a variable (20). The total amount of SO ₃ that can be desorbed from the DOC 22a, that is, the total amount of desorbable SO ₃ is calculated by the following equation (21) using the current bed temperature T ₂ as a variable.

The estimation unit M5 substitutes the calculated total desorbable SO ₂ amount into the following equation (22), and the amount of SO ₂ newly desorbed from the DOC 22a in the t-th cycle, that is, new desorbed SO _2. Calculate the amount. Further, calculating the calculated removable total SO ₃ content by substituting the following equation (23), the amount of SO ₃ newly desorbed from DOC22a in the t-th cycle, i.e., a new desorption SO ₃ weight To do. Note that set values are used for the desorption rates in the equations (22) and (23), and can be stored in the ROM of the ECU 30, for example.
New amount of desorbed SO ₂ (T2 (t), t) [μg] = total desorbable SO ₂ amount [μg] × desorption rate (22)
New desorption SO ₃ amount (T2 (t), t) [μg] = total desorbable SO ₃ amount [μg] × desorption rate (23)

  Returning to FIG. 3, the estimation unit M6 reflects the newly desorbed SOx amount estimated by the estimation unit M5 in the post-adsorption SOx distribution, and estimates the final adsorption SOx distribution.

Specifically, the estimation unit M6 assumes that the SOx is desorbed by the amount of the new desorption SOx estimated by the estimation unit M5 and the shape of the post-adsorption SOx distribution is deformed, and the final adsorption SOx distribution (post-desorption SOx distribution). ). The relationship between the final adsorption SOx distribution and the post-adsorption SOx distribution will be described with reference to FIG. 12 using SO ₂ as an example. Note that TL and TH on the horizontal axis in this figure correspond to the above-described lower limit temperature and upper limit temperature, respectively. As shown in this figure, the area of the post-adsorption SO ₂ distribution when the integrated value from the lower limit temperature TL of the post-adsorption SO ₂ distribution matches the newly desorbed SO ₂ amount, that is, from the lower limit temperature TL to the temperature Td _{SO 2.} The distribution remaining after removing the area of the SOx distribution after adsorption is the final adsorption SO ₂ distribution.

When the above temperature _{Td SO2} floor temperature _{T 1} of the FIG. 12 means that the SO ₂ is all desorbed from DOC22a. Considering this, the final adsorption SO ₂ distribution in the t-th cycle is expressed by the following equation (24) using the bed temperature T ₁ as a variable, and the final adsorption SO ₃ distribution in the t-th cycle is expressed by the following equation (25 ). The temperature _{Td SO3} of formula (25) corresponds to the bed temperature _{T 1} of the when the integrated value from the lower limit temperature TL of SO ₃ distribution after adsorption to match the new desorption SO ₃ amount.

The relationship between the novel desorbed SO ₂ amount and temperature _{Td SO2} can be represented by the following formula (26), the relationship between the new desorbed SO ₃ content and the temperature _{Td SO3} can be expressed by the following equation (27).

Returning to FIG. 3, the estimation unit M7 estimates the amount of SOx discharged from the DOC 22a in the SO ₃ state in the above-described slip-through SOx (hereinafter also referred to as “pass-through SO ₃ amount”).

As described with reference to FIG. 2, in the DOC 22a, a part of SO ₂ adsorbed on the noble metal 22d is converted to SO ₃ . Assuming that this conversion also occurs in the SO ₂ in the slip-through SOx, the estimation unit M7 passes through the SO ₃ in the t-th cycle according to the following equation (28) using the slip-through amount and the current bed temperature T ₂ as variables. Estimate the amount. Note that the amount of SOx discharged from the DOC 22a in the SO ₂ state (hereinafter also referred to as “the amount of slip-through SO ₂ ”) of the slip-through SOx can be expressed by the following equation (29).
Amount of slip-through SO ₃ (amount of slip-through (t), T ₂ (t)) [μg / s] = amount of slip-through SOx (t) × SO ₃ conversion map (T ₂ (t)) (28)
Amount of slip-through SO ₂ (amount of slip-through (t), T ₂ (t)) [μg / s] = amount of slip-through SOx (t) × {1-SO ₃ conversion rate map (T ₂ (t))} 29)

The SO ₃ conversion rate map (T ₂ (t)) of the equations (28) and (29) is the SOx discharged in the state of SO ₃ from the DOC 22a among “SOx flowing into the DOC 22a” in the t-th cycle. ratio of (i.e., SO ₃ conversion rate) is a map created based on the characteristics of the current vary bed temperature _{T 2} of the DOC22a. As shown in FIG. 13, when the current bed temperature T ₂ is in a certain temperature range B, the SO ₃ conversion rate is high. On the lower temperature side and the higher temperature side than this temperature region B, SO ₂ to SO ₃ The conversion to is difficult to occur. Such a map can be memorized for example in the ECU30 in the ROM, a read appropriately according currently bed temperature T _2.

Returning to FIG. 3, the calculation unit M8 calculates the amount of SO ₃ that may be desorbed from the DOC 22a while the bed temperature of the DOC 22a is rising (hereinafter also referred to as “allowable desorption SO ₃ amount”). The amount of allowable desorption SO ₃ will be described with reference to FIG. Constraints SO ₃ amount shown in this figure, which corresponds to the constraints on sulfate white smoke, the sum of the SO ₃ content and acceptable desorbed SO ₃ weight slipping in this figure is equal to the constraint SO ₃ amount. Since the sum of the slip-through SO ₃ amount and the allowable desorption SO ₃ amount is the amount of SO ₃ downstream of the DOC 22a, the constraint is satisfied if the value of this sum is smaller than the constraint SO ₃ amount. Become.

The amount of constraint SO ₃ can be calculated by the following equation (30) using the exhaust flow rate (gas flow rate) of the engine 10 in the t-th cycle as a variable. For example, the detected value of the air flow meter 32 can be used as the exhaust flow rate of the engine 10.
Restricted SO ₃ amount (gas flow rate (t)) [μg / s] = restricted SO ₃ concentration [ppm] × gas flow rate (t) [g / s] ÷ average molar mass of air × SO ₃ molecular weight (30 )

Therefore, the constraint is satisfied if the allowable desorption SO ₃ amount satisfies the following equation (31) using the constraint SO ₃ amount and the slip-through SO ₃ amount as variables.
Allowable desorption SO ₃ amount (restricted SO ₃ amount (gas flow rate (t)), slip-through SO ₃ amount (t)) [μg / s] ≦ restricted SO ₃ amount (gas flow rate (t)) [μg / s] − Slip-through SO ₃ amount (t) [μg / s] (31)
In the following description, the allowable desorption SO ₃ amount (restricted SO ₃ amount (gas flow rate (t)), slip-through SO ₃ amount (t)) is also simply referred to as allowable desorption SO ₃ amount (t).

Returning to FIG. 3, the calculation unit M9 calculates the target temperature Ttrg in the t-th cycle for suppressing the generation of sulfate white smoke during PM regeneration control. The target bed temperature Ttrg will be described with reference to FIG. Note that TL and TH on the horizontal axis in this figure correspond to the above-described lower limit temperature and upper limit temperature, respectively. As shown in this figure, the bed temperature T ₁ when the value obtained by multiplying the integral value from the low temperature side of the final adsorption SO ₃ distribution by the desorption rate matches the allowable desorption SO ₃ amount calculated by the calculation unit M8. Corresponds to the target bed temperature Ttrg.

The relationship between the allowable desorption SO ₃ amount and the target temperature Ttrg in the t-th cycle can be expressed by the following equation (32). A set value is used as the desorption rate in the equation (32), and can be stored in the ROM of the ECU 30, for example.

With reference to FIG. 16, the effect by this Embodiment is demonstrated. This figure shows (i) ~ (iii) corresponds to the case with the start of PM regeneration control at time t ₀ of the three set the target bed temperature of DOC22a. Specifically, the case (i) corresponds to a case where the target temperature is switched to a step shape at time t ₀ and set to a high temperature. In this case, the actual catalyst bed temperature (middle stage) of the DOC 22a rapidly increases. Therefore, the SO ₃ concentration (lower stage) downstream of the DOC 22a exceeds the restricted SO ₃ concentration. Further, it corresponds to when increasing the target temperature at a constant rate in case the time t ₀ of (ii). In this case, the actual catalyst bed temperature (middle stage) of the DOC 22a can also be increased at a constant speed. In addition, by setting the rate of increase in consideration of the restricted SO ₃ concentration, the SO ₃ concentration (lower stage) downstream of the DOC 22a can be suppressed to be equal to or lower than the restricted SO ₃ concentration. However, on the other hand, it takes a long time to complete the PM regeneration control. In this case, in the case of (iii) corresponding to the method of the present embodiment, not only the SO ₃ concentration (lower stage) downstream of the DOC 22a is kept below the constrained SO ₃ concentration, but PM regeneration control is completed in a short time. You can also

In the embodiment described above, the estimation unit M1 is the “inflow SOx amount estimation unit” of the present invention, the estimation unit M2 is the “SOx saturation rate estimation unit” of the present invention, and the estimation unit M3 is the “ In the “new adsorption SOx amount estimation means” and “pass-through SOx amount estimation means”, the estimation unit M4 is the “post-adsorption SOx distribution estimation means” of the present invention, and the estimation unit M5 is the “new desorption SOx amount estimation means” of the present invention. The estimation unit M6 is the “final adsorption SOx distribution estimation unit” of the present invention, the estimation unit M7 is the “passing SO ₃ amount estimation unit” of the present invention, and the calculation unit M8 is the “allowable desorption SO ₃ amount of the present invention”. The calculation unit M9 corresponds to the “target temperature calculation unit” of the present invention.

In the above-described embodiment, PM regeneration control is performed by adding fuel from the fuel addition valve 24. However, this PM regeneration control may be performed by fuel injection from the injector 12 (specifically, sub injection (for example, post injection) after the main injection). In this case, the exhaust addition amount in the equation (1) may be replaced with the sub injection amount from the injector 12.
In the above-described embodiment, the target temperature of the bed temperature of the DOC 22a is calculated by taking PM regeneration control as an example. However, when the control for desorbing SOx from the DOC 22a is performed together with the PM regeneration control, the target temperature of the bed temperature of the DOC 22a may be calculated by the above-described method during the desorption control. As described above, the target temperature calculation method described above can be generally applied to control for increasing the bed temperature of the DOC 22a from the DOC 22a to a temperature range where SOx is desorbed.
Moreover, in embodiment mentioned above, the exhaust gas purification apparatus 22 provided with DOC22a and DPF22b was demonstrated as an example. However, an oxidation function such as HC in the DOC 22a may be added to the DPF 22b, and the DOC 22a may be omitted from the exhaust purification device 22. In this case, the same effect as that of the above-described embodiment can be obtained by applying the above-described method for calculating the target temperature to the DPF 22b having an oxidation function.
In the above-described embodiment, the engine 10 includes the turbocharger 16. However, the engine 10 may not include the turbocharger 16. That is, the target temperature calculation method described above can also be applied to a non-supercharged diesel engine system.

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 20 Exhaust pipe 22 Exhaust gas purification apparatus 22a DOC
22b DPF
22c Coat material 22d Precious metal 24 Fuel addition valve 30 ECU

Claims (2)

An engine control device that performs control to increase the temperature of a purification device provided in an exhaust pipe of a diesel engine to a target temperature in a temperature range where SOx is desorbed from the purification device,
An inflow SOx amount estimating means for estimating the SOx amount flowing into the purification device as an inflow SOx amount for each cycle;
The adsorption SOx distribution expressed as a graph in which the amount of SOx adsorbed to the purification device at each temperature during the temperature increase of the purification device is related to the temperature of the purification device, and the temperature at each temperature during the temperature increase of the purification device. SOx saturation rate estimating means for estimating the SOx saturation rate in the purification device for each cycle using a saturation SOx distribution represented as a graph in which the maximum amount of SOx adsorbed to the purification device is related to the temperature of the purification device. And the SOx saturation rate estimating means in which the saturation SOx distribution corresponds to the temperature of the purifier in the current estimation cycle of the SOx saturation rate;
Using the inflow SOx amount and the SOx saturation rate, a new adsorption SOx amount estimation means for estimating, for each cycle, a SOx amount that flows into the purification device and is newly adsorbed to the purification device as a new adsorption SOx amount;
By using the new adsorption SOx amount, the SOx amount estimating means for estimating the SOx amount that flows into the purification device without passing through the purification device and is not adsorbed to the purification device as the slipping SOx amount for each cycle;
A post-adsorption SOx distribution estimation unit that estimates the SOx distribution after the new SOx is adsorbed on the purification device as the post-adsorption SOx distribution for each cycle using the new adsorption SOx amount;
Using the post-adsorption SOx distribution and the temperature of the purification device, a new desorption SOx amount estimation means that estimates the amount of SOx newly desorbed from the purification device as a new desorption SOx amount for each cycle;
Final adsorbed SOx distribution estimating means for reflecting the amount of the new desorbed SOx in the post-adsorption SOx distribution and estimating the SOx distribution after desorbing new SOx from the purification device as a final adsorbed SOx distribution for each cycle. When,
A conversion rate map showing the relationship between the conversion rate of SO ₂ converted to SO ₃ in the purification device and the temperature of the purification device, the temperature of the purification device in the current estimation cycle, and the amount of slip-through SOx used, it slipped SO ₃ amount estimating for each cycle as SO ₃ weight slipped through SO ₃ amount discharged in the form of SO ₃ to pass through without being adsorbed on the purifier flows into a state of SOx to the purifier An estimation means;
Using the SO ₃ content above the slipped SO ₃ amount in the downstream of the purification device corresponding to constraints on sulfate white smoke, the SO ₃ amount is allowed desorbed from the purifier acceptable leaving SO ₃ weight An allowable desorption SO ₃ amount calculating means for calculating for each cycle;
Using the final adsorption SOx distribution and the allowable desorption SO ₃ amount, target temperature calculation means for calculating the target temperature for each cycle so that the SO ₃ concentration downstream of the purification device satisfies the constraint; Prepared,
The SOx saturation rate estimation means includes a total saturated SOx amount corresponding to the area of the saturated SOx distribution, and a total adsorption corresponding to an area obtained by removing an overlapping portion of the saturated SOx distribution and the adsorption SOx distribution from the saturated SOx distribution. The SOx saturation rate is calculated using a margin SOx amount,
The post-adsorption SOx distribution estimating means reflects the new adsorption SOx amount in the final adsorption SOx distribution estimated in the previous estimation cycle, and estimates the post-adsorption SOx distribution in the current estimation cycle. Engine control device. The purification device includes a filter that collects particulates flowing through the exhaust pipe,
2. The engine control device according to claim 1, wherein the control for increasing the temperature to the target temperature is started when an estimated value of the amount of fine particles collected by the filter reaches a removal request amount. 3.

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