JP6547779B2 - Engine control unit - Google Patents

Description

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

Conventionally, sulfur oxides adsorbed on a catalyst provided in the exhaust pipe of a diesel engine (SO ₂ or SO ₃ , hereinafter referred to collectively as “SOx” when these are not distinguished from each other) are periodically desorbed. It is known to perform temperature rise control. As a document relevant to temperature rising control, Unexamined-Japanese-Patent No. 2013-029038 is mentioned, for example. 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, raising the bed temperature of the catalyst to control it at 500 to 550 ° C. It is done. According to this publication, SOx is not released from the catalyst when the bed temperature is less than 500 ° C, and SOx is released from the catalyst at a low concentration when the bed temperature is 500 to 550 ° C, and the bed temperature exceeds 600 ° C. The catalyst is characterized as having a high concentration of SOx released from the catalyst and the catalyst. Therefore, if the bed temperature of the catalyst having such characteristics is controlled to 500 to 550 ° C., SOx can be desorbed from the catalyst at a low concentration to restore its function. In addition, the generation of white smoke from SOx desorbed at a low concentration can also be suppressed.

JP, 2013-029038, A JP, 2015-169105, A

  The technique of the above publication focuses on the characteristics of the SOx release amount from the catalyst with respect to the bed temperature of the catalyst. However, the amount of SOx desorbed from the catalyst is affected not only by the bed temperature of the catalyst but also by the change in the bed temperature. For this reason, in the technique of the above-mentioned publication, there is a possibility that the amount of SOx desorbed from the catalyst can not be accurately estimated under the condition that the temperature change of the catalyst is large.

  The present invention has been made in view of the problems as described above, and in temperature-rise control of the catalyst, recovery of the function of the catalyst by desorption of SOx by accurately estimating the amount of SOx desorbed from the catalyst and It is an object of the present invention to provide an engine control device capable of achieving, at a high level, the suppression of the generation of white smoke caused by the desorbed SOx.

The present invention is directed to an engine control device that executes temperature increase control to raise 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. The engine control device estimates temperature control means for obtaining a representative temperature which is a representative value of the temperature of the purifier at predetermined control cycles, and the amount of SOx flowing into the purifier as the amount of inflow SOx for each control period. New desorbed SOx that estimates the amount of SOx newly desorbed from the purifier as the amount of newly desorbed SOx for each control cycle using the inflowing SOx amount estimating means, the inflowing SOx amount, and the representative temperature Final figure represented as a graph in which the amount of SOx finally adsorbed to the purification device at each temperature rise of the purification device is associated with the representative temperature using the amount estimation means and the new desorption SOx amount The target temperature is controlled using the final adsorption SOx distribution estimation means for estimating the adsorption SOx distribution for each control cycle, and the final adsorption SOx distribution and the allowable desorption SO ₃ amount. And target temperature calculation means for calculating each cycle. The newly desorbed SOx amount estimation means corrects the correction value by reflecting the correction value on the representative temperature, calculating means for calculating a correction value representing the degree of change from the past value of the representative temperature to the current value. And correction means for calculating a post-representative temperature, wherein the newly desorbed SOx amount is estimated using the inflow SOx amount and the corrected representative temperature. Further, the correction means is configured such that the degree of reflection of the degree of change on the representative temperature after correction is monotonically non-increasing and decreases as the representative temperature increases.

  In the engine control device according to the present invention, the correction means calculates a correction coefficient which decreases monotonically non-increasing as the representative temperature increases, and adds a value obtained by multiplying the correction value by the correction coefficient to the representative temperature. Thus, the corrected representative temperature may be calculated.

  Further, in the engine control device of the present invention, the calculation means may be configured to calculate a difference value between the current value of the representative temperature and the previous value as the correction value.

In the engine control apparatus according to the present invention, an adsorbed SOx distribution represented as a graph in which the amount of SOx adsorbed to the purification device is correlated with the representative temperature at each temperature during the temperature rise of the purification device; Using the saturated SOx distribution represented as a graph in which the maximum amount of SOx adsorbed to the purifier is associated with the representative temperature at each temperature during temperature rise, the SOx saturation rate in the purifier for each control cycle The amount of SOx which flows into the purifier and is newly adsorbed to the purifier using the SOx saturation rate estimation means to be estimated, the inflow SOx amount and the SOx saturation rate as the new adsorption SOx amount for each control cycle Using the newly adsorbed SOx amount estimating means to estimate the amount and the newly adsorbed SOx amount, the adsorbed SOx after new SOx is adsorbed to the purification device A post-adsorption SOx distribution estimating means for estimating for each of the control period as SOx distribution after adsorption fabric may comprise. In this case, the newly desorbed SOx amount estimating means may be configured to estimate the newly desorbed SOx amount for each control cycle using the post-adsorption SOx distribution and the representative temperature. Further, the engine control device according to the present invention uses the newly adsorbed SOx amount to estimate the SOx amount which flows into the purification device and slips without being adsorbed to the purification device as the SOx amount which is slipped through for each control cycle. SOx amount estimation means, a conversion rate map representing the relationship between the conversion rate of SO ₂ converted to SO ₃ in the purifier and the representative temperature, the representative temperature in this estimated cycle, and the amount of SOx slipped-off , is used to estimate for each of the control period as the purifier slip 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 SO ₃ amount and SO ₃ amount estimating means slipping, said the SO ₃ content in the downstream of the purification device corresponding to constraints on sulfate white smoke slipped SO With the amount, and the allowable desorbed SO ₃ amount calculating means for calculating an SO ₃ amount that is allowed to detach from the purification device to each of the control period as the allowable desorbed SO ₃ amount, further comprising as the May be configured.

  Furthermore, in the engine control device of the present invention, the temperature acquisition means may be configured to acquire the temperature of the gas that has flowed to the downstream side of the purification device in the exhaust pipe as the representative temperature.

  Further, in the engine control device of the present invention, the purification device may include a filter that collects particulates flowing through the exhaust pipe. In this case, the temperature rise control may be started when the estimated value of the amount of particulates collected by the filter reaches a required removal amount.

  According to the present invention, the representative temperature of the purification device is used to estimate the amount of desorption SOx which is newly desorbed from the purification device. At this time, a correction is made to reflect the degree of change from the past value of the representative temperature to the present value on the representative temperature, and the amount of newly desorbed SOx is estimated using the corrected corrected representative temperature. Here, the correction of the representative temperature is performed so that the degree of reflection of the correction value on the representative temperature monotonously does not increase and decreases as the representative temperature increases. The amount of released SOx is affected not only by the representative temperature of the purifier but also by the degree of change of the representative temperature. Specifically, while the low temperature region of the purifier is greatly affected by the degree of change in the representative temperature, the high temperature region of the purifier is less affected than the low temperature region. Therefore, according to the present invention, even if the temperature of the purification device is high, the amount of desorption SOx can be accurately estimated. Therefore, in the temperature elevation control of the catalyst, recovery of the function of the catalyst by desorption of SOx And the suppression of the generation of white smoke due to this SOx can be achieved at a high level.

It is a figure showing the system configuration of an embodiment of the invention. It is a figure for demonstrating adsorption and desorption of SOx in DOC22a. It is a functional block diagram which shows the logic for calculating the 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 relationship between reference | standard saturated SOx distribution and saturated 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 the amount of novel adsorption SOx, and the amount of slip-through SOx. It is a figure for demonstrating the adsorption rate map. It is a figure for demonstrating SOx distribution after adsorption | suction. It is a figure for demonstrating the amount of detachable SOx. Corrected current is a functional block diagram showing the logic for calculating the bed temperature T _{2 '.} Before correction is a diagram showing an example of a map that currently associated with the temperature correction coefficient K to the floor temperature T _2. It is a figure for demonstrating the relationship between final adsorption SOx distribution and SOx distribution after adsorption. 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 time chart for explaining the effect of temperature amendment of present bed temperature.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, when the number of the number, the number, the quantity, the range, etc. of each element is mentioned in the embodiment shown below, the mention is made unless otherwise specified or the number clearly specified in principle. The present invention is not limited to the above numbers. In addition, the structures, steps, and the like described in the embodiments below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

Embodiment 1
Embodiment 1 of the present invention will be described with reference to the drawings.

[Description of system configuration]
FIG. 1 is a diagram showing a system configuration of the embodiment of the present invention. The system shown in FIG. 1 includes a diesel engine 10 mounted on a vehicle (hereinafter, also simply referred to as "engine 10"). 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. Also, one of the four injectors 12 is depicted in FIG.

An inlet of an exhaust turbine 16 a of the turbocharger 16 is connected to an exhaust manifold 14 of the engine 10. 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 the intake air. An exhaust pipe 20 is connected to the outlet of the exhaust turbine 16a. An exhaust 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 to convert them into water (H ₂ O) and carbon dioxide (CO ₂ ). The DPF 22 b 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 random access memory (RAM), a read only memory (ROM), a central processing unit (CPU), and the like. The ECU 30 takes in and processes signals of various sensors mounted on the vehicle. The various sensors include an air flow meter 32 provided near 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. The ECU 30 processes the signal of each sensor taken in and operates various actuators in accordance with 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, temperature increase control (hereinafter also referred to as “PM regeneration control”) of the DPF 22 b 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 22 b reaches the removal requirement 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 heat of oxidation reaction raises the bed temperature of the DPF 22b to 600 ° C. or more. Thus, the PM collected by the DPF 22b can be burned and removed, so that the collection function of the DPF 22b can be recovered. The amount of fuel added from the fuel addition valve 24 to raise the bed temperature of the DPF 22b to 600 ° C. or more (hereinafter “the amount of DPF fuel”) is determined based on the map associated with the bed temperature of the DPF. Such a map can be stored, for example, in the ROM of the ECU 30, and can be read appropriately in accordance with the actual floor temperature of the DPF 22b.

[Problems in PM regeneration control]
By the way, fuel is generally contained in diesel engine fuel and lubricating oil, and SOx is generated from such sulfur as the fuel is burned. Similarly in the present embodiment, SOx is generated as the fuel burns in the engine 10. The generated SOx is discharged from the engine 10, flows into the exhaust purification device 22, and is adsorbed mainly to the DOC 22a. However, when the bed temperature of DOC 22a becomes high, SOx adsorbed here starts to be desorbed. Although it fluctuates somewhat depending on the composition of the DOC 22a, SOx is released from the DOC 22a to the downstream side in the temperature range where the PM regeneration control is performed.

The adsorption and desorption of SOx in the DOC 22a will be described with reference to FIG. FIG. 2 is a diagram for explaining the adsorption and desorption of SOx in the DOC 22a. As shown to this figure, DOC22a is provided with the coating material 22c which covers the surface of a base material (not shown), and noble metals 22d (Pt, Pd, etc.). The noble metal 22d is dispersed and supported on the coating material 22c, and becomes an active point when oxidizing HC or CO. However, SO ₂ in the exhaust gas is adsorbed to the noble metal 22 d, or SO _{3 in} the exhaust gas is adsorbed to the coating material 22 c. Some of SO ₂ adsorbed on the noble metal 22d returns to the exhaust desorbed from the noble metal 22d, or is oxidized over a noble metal 22d SO _3, and the adsorbed to the coating material 22c in a 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 of SOx inhibits the oxidation function of HC and the like in the DOC 22a.

The SO ₃ adsorbed to the coating material 22 c by the two paths described above is desorbed when the bed temperature of the coating material 22 c becomes high. Moreover, since the conversion from SO ₂ to SO ₃ on the noble metal 22 d is promoted by the bed temperature of the coating material 22 c becoming high, such SO ₃ is also desorbed from the coating material 22 c. Therefore, by performing PM regeneration control, not only the collection function of the DPF 22b described above, but also the oxidation function of HC or the like in the DOC 22a can be restored. However, as shown in FIG. 2, SO ₃ released from the coating material 22 c reacts with H ₂ O present in the exhaust pipe 20 to generate H ₂ SO ₄ . Then, when the concentration of H ₂ SO ₄ exceeds a certain concentration, visible white smoke (sulfate white smoke) is obtained, and therefore, the commercial value of the vehicle equipped with the engine 10 may be impaired.

[Features of this embodiment]
By adding fuel from the fuel addition valve 24 so that the concentration of H ₂ SO ₄ in the exhaust gas downstream of the DOC 22 a is not too high, it is possible to suppress the generation of sulfate white smoke during PM regeneration control. Therefore, in the present embodiment, the target temperature of the bed temperature of DOC 22a during PM regeneration control (hereinafter also referred to as "target bed temperature Ttrg") so that the concentration of SO ₃ downstream of DOC 22a satisfies the constraint on sulfate white smoke. Is calculated, and based on the target bed temperature Ttrg, the amount of fuel added from the fuel addition valve 24 (hereinafter also referred to as “restriction satisfying fuel amount”) is calculated. Note that such a restricted SO ₃ concentration (upper limit value of the SO ₃ concentration downstream of the DOC 22 a) can be stored, for example, in the ROM of the ECU 30. When the DPF fuel amount is larger than the constraint satisfaction fuel amount, adopting the constraint satisfaction fuel amount instead of the DPF fuel amount allows oxidation of HC, etc. in the DOC 22a while satisfying the constraint on sulfate white smoke. Function can be recovered.

[Calculation logic of target floor temperature Ttrg]
FIG. 3 is a functional block diagram showing a logic for calculating the target floor temperature Ttrg, which 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 newly adsorbed SOx amount and a slip-through SOx amount estimation unit M3, a post adsorption SOx distribution estimation unit M4, and a new removal A separation SOx amount estimation unit M5, a final adsorbed SOx distribution estimation unit M6, a slip through SO ₃ amount estimation unit M7, an allowable desorption SO ₃ amount calculation unit M8, and a white smoke suppression target bed temperature calculation unit M9 The target bed temperature Ttrg is calculated for each control cycle (specifically, for each combustion cycle of the engine 10) by these elements M1 to M9. In the following description, the elements M1 to M9 are simplified, and for example, the inflow SOx amount estimating unit M1 is also referred to as an “estimating unit M1”.

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

More specifically, the estimation unit M1 uses the following formula (1) with the injection fuel amount from the injector 12 (in-cylinder injection amount) and the addition fuel amount from the fuel addition valve 24 (exhaust addition amount) as variables: Estimate the amount of inflow SOx in the second cycle. The concentration of fuel S in the equation (1) is the concentration of sulfur in the fuel, and the detection value of a sulfur concentration sensor separately provided in the fuel supply system may be used, or the 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 inflowing fuel amount (exhaust addition amount (t), in-cylinder injection amount (t)) of equation (1) is the amount in the t-th cycle of the fuel from which "SOx flowing into DOC 22a" is derived. It is calculated according to 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 / cm3] + in-cylinder 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 the inflow SOx amount (t). Further, the inflowing fuel amount (exhaust addition amount (t), in-cylinder injection amount (t)) is also referred to as the inflowing fuel amount (t).

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

FIG. 4 is a view for explaining the adsorbed SOx distribution and the saturated SOx distribution. 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 to the DOC 22a at the bed temperature shown as "current temperature" in FIG. Subsequently, the amount of SO ₃ desorbed from the DOC 22a at each bed temperature during the bed temperature rise of the DOC 22a is measured under the condition that the rate of rise is constant. Then, the amount of released SO ₃ is associated with the bed temperature of DOC 22a to create a graph. Thus, (hereinafter also referred to as "desorption SO ₃ distribution".) Distribution represents a leaving SO ₃ amount can be obtained. A graph (hereinafter also referred to as “desorbed SO ₂ distribution”) in which the amount of SO ₂ desorbed from DOC 22 a at each bed temperature during rising bed temperature of DOC 22 a is related to the bed temperature of DOC 22 a by the same method. 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 be considered to be a SO _3. Based on such an assumption, when the vertical axis of the above-described desorption SO ₃ distribution is replaced with the amount of SO ₃ adsorbed to the DOC 22 a at each bed temperature during the bed temperature rise of the DOC 22 a, “adsorption shown in FIG. A graph of “SO ₃ content” data can be obtained, ie an adsorbed SO ₃ distribution. Then, the adsorbed SO ₂ distribution can also be obtained by the same method as this.

The data indicated as "saturated SO ₃ amount" in FIG. 4 is collected by the same method as the data of "adsorption SO ₃ amount." Specifically, the data of “the amount of saturated SO ₃ ” are SO desorbed from DOC 22 a at each bed temperature (for example, 5 ° C. interval) during the rise of bed temperature of DOC 22 a under the condition that the rise rate is extremely low. It corresponds to the amount of _three . Since the rate of increase of the bed temperature of DOC 22a is extremely low, it can be considered that this "saturated SO ₃ amount" data is the maximum value of the amount of SO ₃ released from DOC 22a. In addition, the above-described assumption can be applied to this maximum value. That is, the maximum amount of SO ₃ desorbed from DOC 22a at a certain bed temperature can be considered to be equal to the largest amount of SO ₃ that could be adsorbed to DOC 22a at that 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 You can get Then, a saturated SO ₂ distribution can be obtained by the same method as this.

The estimation unit M2 estimates the SOx saturation ratio (T ₂ (t), t) in the t-th cycle according to the following equation (3) using the current bed temperature T ₂ of the DOC 22a in the t-th cycle as a variable . Note that the current bed temperature T ₂ are, can be used as a representative temperature of the current bed temperature of DOC22a, for example, the detection value of the temperature sensor 34.
SO x saturation ratio (T ₂ (t), t) = 1-(total adsorption margin (T ₂ (t), t) / total saturation (T ₂ (t), t)) (3)

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

The reference saturated SO ₂ distribution of the equation (4) is such that the bed temperature (“current temperature” in FIG. 4) at which a sufficient amount of SOx is adsorbed to the DOC 22 a becomes the reference bed temperature (for example, the aforementioned adsorption limit amount becomes maximum) It is a saturated SO ₂ distribution created as a bed temperature around 300 ° C.). The reference saturated SO ₃ distribution of equation (5) is similar to this. The bed temperature correction SO ₂ map (T ₂ (t)) of the equation (4) is a map in which correction values for converting the reference saturated SO ₃ distribution into the saturated SO ₂ distribution of the current bed temperature T ₂ are defined. The bed temperature correction SO ₃ map (T ₂ (t)) of Formula (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 saturated SOx distribution after correction will be described with reference to FIG. 5 using SO ₂ as an example. FIG. 5 is a diagram for explaining the relationship between the reference saturated SOx distribution and the saturated SOx distribution after correction. Note that TL and TH on the horizontal axis of this figure are the temperature at which SO ₂ begins to desorb from DOC 22 a (lower limit temperature) and the temperature at which SO ₂ ceases to desorb from DOC 22 a (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, if the current floor temperature T ₂ is lower than the reference temperature (left) and, if the current floor temperature T ₂ is higher than the reference temperature (right), the shape of the saturation SO ₂ distribution after the correction reference saturation It will not match the shape of the SO ₂ distribution. Incidentally, when the current bed temperature T ₂ is higher than the reference temperature (right), the shape of the saturation SO ₂ distribution after the correction, such as the low temperature side of the data than the current floor temperature T ₂ is missing 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 Calculate ₂ (t), t). 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 .

Once the total saturated SO ₂ amount (T ₂ (t), t) and the total saturated SO ₃ amount (T ₂ (t), t) have been calculated, these are substituted into the following equation (8) to obtain the t th cycle Calculate the total amount of saturation (T ₂ (t), t) in
Total saturated amount (T ₂ (t), t) = total saturated SO ₂ amount (T ₂ (t), t) + total saturated 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). Also, the total saturated SO ₃ amount (T ₂ (t), t) is simply referred to as the total saturated SO ₃ amount (t). Also, the total saturated amount (T ₂ (t), t) is simply referred to as the total saturated 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 adsorbed SO ₂ distribution in the t-th cycle estimated by the estimation unit M6 The adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) in the t-th cycle is calculated by substituting (T ₁ , t) into the following equation (9). Further, the saturated SO ₃ distribution (T ₁ , T ₂ (t), t) and the final adsorbed SO ₃ distribution (T ₁ , t) in the t-th cycle estimated by the estimation unit M6 are expressed by the following equation (10) To calculate the adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) in the t-th cycle.
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 adsorbed SO ₂ distribution (T ₁ , t) [μg / ° C.], 0} (9)
Adsorption margin SO ₃ distribution _{(T 1, T 2 (t} ), t) [μg / ℃] = max { saturated SO ₃ distribution _{(T 1, T 2 (t} ), t) [μg / ℃] - Final adsorption SO ₃ distribution (T ₁ , t) [μg / ° C.], 0} (10)

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 Calculate (T ₂ (t), t). Further, the total adsorption margin SO ₃ amount (t 1st cycle) is substituted for the distribution (T ₁ , T ₂ (t), t) of the adsorption margin SO ₃ calculated by the equation (10) into the following equation (12) Calculate T ₂ (t), t).

In the following description, the adsorption margin SO ₂ distribution (T ₁ , T ₂ (t), t) is also simply referred to as the adsorption margin SO ₂ distribution (t). In addition, the adsorption margin SO ₃ distribution (T ₁ , T ₂ (t), t) is simply referred to as the adsorption margin SO ₃ distribution (t). Further, 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). Further, 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. FIG. 6 is a diagram for explaining the total amount of adsorption margin SO ₂ . 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. As indicated by the region A in the distribution on the right side of the figure, the amount of SO ₂ adsorbed to the DOC 22a at each bed temperature during the rise of the bed temperature of the DOC 22a, ie, the adsorbed SO ₂ amount is the maximum amount, ie, If it exceeds the saturated SO ₂ amount, it is considered that the DOC 22 a is saturated, so it 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.

Then, after calculating the total adsorption margin SO ₂ amount (t) and the total adsorption margin SO ₃ amount (t), these are substituted into the following equation (13) to obtain the total adsorption margin amount (T ₂ in the t th cycle) Calculate (t), t).
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 ratio (T ₂ (t) , T) can be calculated. In the following description, the saturation ratio (T ₂ (t), t) is also simply referred to as the saturation ratio (t).

  Returning to FIG. 3, the explanation of the calculation logic of the target floor temperature Ttrg is continued. The estimation unit M3 is “SOx flowing into DOC 22a” and is an amount of SOx newly adsorbed to DOC 22a (hereinafter, also referred to as “newly adsorbed SOx amount”), and “SOx flowing into DOC 22a”; DOC 22a Estimate the amount of SOx slipped through without adsorbing to (hereinafter also referred to as “the amount of slipped SOx”). First, the relationship between the amount of newly adsorbed SOx and the amount of slipped-through SOx will be described with reference to FIG. FIG. 7 is a diagram for explaining the relationship between the amount of newly adsorbed SOx and the amount of slip-through SOx. As indicated by the arrows in this figure, the sum of the amount of newly adsorbed SOx and the amount of slipped-through SOx becomes equal to the amount of inflowing SOx. The reason for this is that a part of the "SOx flowing into DOC 22a" is adsorbed to DOC 22a, and the remainder is slipped off without being adsorbed to DOC 22a.

More specifically, the estimating unit M3 uses the following equation (14) with the inflow SOx amount (t) estimated by the estimating unit M1 and the saturation ratio (t) estimated by the estimating unit M2 as variables: The amount of SOx is estimated by the following equation (15).
New adsorbed SOx amount (inflow SOx amount (t), saturation rate (t)) [μg / s] = inflow SOx amount (t) × adsorption rate map (saturation rate (t)) (14)
Amount of slipped SOx (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 amount of newly adsorbed SOx (the amount of inflow SOx (t), the saturation ratio (t)) is also simply referred to as the amount of newly adsorbed SOx (t). Further, the amount of slipped SOx (the amount of inflow SOx (t), the saturation ratio (t)) is also simply referred to as the amount of slipped SOx (t).

In the adsorption rate map of the equations (14) and (15), the proportion (ie, the adsorption rate) of SOx adsorbed to the DOC 22a in the “SOx flowing into the DOC 22a” in the t-th cycle is the saturation rate (t) It is a map created based on the characteristic that it changes with. FIG. 8 is a diagram for explaining the adsorption rate map. As shown in this figure, the characteristics of the adsorption rate map are such 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.

Referring back to FIG. 3, the estimating unit M4 reflects the amount of the newly adsorbed SOx estimated by the estimating unit M3 in the adsorbed SOx distribution to estimate the post-adsorption SOx distribution. The SOx distribution after adsorption will be described with reference to FIG. 9 in which SO ₂ is taken as an example. FIG. 9 is a view for explaining the SOx distribution after adsorption. As shown in this figure, the post-adsorption SO ₂ distribution is newly added to the DOC 22 a in the present cycle (for example, the t-th cycle) to the final adsorbed SO ₂ distribution in the previous cycle (for example, the t−1st cycle). It is estimated by adding the distribution (hereinafter, also referred to as “newly adsorbed SO ₂ distribution”) representing the amount of SO ₂ adsorbed to the

More specifically, the estimation unit M4 first uses the following equation (16) with the newly adsorbed SOx amount (t), the total adsorption margin (t) and the adsorption margin SO ₂ distribution (t) as variables: Calculate the new adsorbed SO ₂ distribution in the cycle. Similar to the new adsorbed SO ₂ distribution, the estimation unit M4 calculates a distribution (hereinafter, also referred to as “newly adsorbed SO ₃ distribution”) representing the amount of SO ₃ newly adsorbed to the DOC 22 a by the following equation (17) Do. As the adsorption margin SO ₂ distribution (t) and the total adsorption margin amount (t), those calculated in the estimation unit M2 are used.
Novel adsorption SO ₂ distribution (new adsorption SOx amount (t), adsorption margin SO ₂ distribution (t), total adsorption margin (t)) [μg / ° C] = adsorption margin SO ₂ distribution (t) [μg / ° C] × {newly adsorbed SOx amount (t) / total adsorption margin amount (t)} (16)
Novel adsorption SO ₃ distribution (new adsorption SOx amount (t), adsorption margin SO ₃ distribution (t), total adsorption margin (t)) [μg / ° C] = adsorption margin SO ₃ distribution (t) [μg / ° C] × {newly adsorbed SOx amount (t) / total adsorption margin amount (t)} (17)
In the following description, the newly adsorbed SO ₂ distribution (newly adsorbed SOx amount (t), adsorption margin SO ₂ distribution (t), total adsorption margin amount (t)) is simply referred to as newly adsorbed SO ₂ distribution (t) It is also called. Further, 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).

The estimating unit M4 subsequently substitutes the calculated newly adsorbed SO ₂ distribution and the final adsorbed SO ₂ distribution (t−1) in the t−1 th cycle into the following equation (18), ₂ Calculate the distribution. In addition, the newly adsorbed SO ₃ distribution calculated and the adsorbed SO ₃ distribution (t-1) estimated by the estimation unit M6 in the (t-1) th cycle are substituted into the following equation (19) to obtain SO ₃ after adsorption Calculate the distribution.
SO ₂ distribution after adsorption (t) [μg / ° C] = final adsorption SO ₂ distribution (t-1) [μg / ° C] + new adsorption SO ₂ distribution (t) [μg / ° C] (18)
SO ₃ distribution after adsorption (t) [μg / ° C] = final adsorption SO ₃ distribution (t-1) [μg / ° C] + new adsorption SO ₃ distribution (t) [μg / ° C] (19)

  Referring back to FIG. 3, the estimating unit M5 estimates the amount of SOx to be newly desorbed from the DOC 22a (hereinafter, also referred to as "newly desorbed SOx amount") based on the SOx distribution after adsorption estimated by the estimating unit M4. .

Specifically, the estimation unit M5 first estimates the total amount of SOx (hereinafter, also referred to as "removable total SOx amount") that can be eliminated from the DOC 22a. The removable total SOx amount will be described with reference to FIG. 10 taking SO ₂ as an example. FIG. 10 is a diagram for explaining the removable total SOx amount. Note that TL and TH on the horizontal axis of this figure respectively correspond to the lower limit temperature and the upper limit temperature described above. 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 the DOC 22a, that is, the total removable amount of SO ₂ is calculated by the following equation (20) with the current bed temperature T ₂ as a variable. The total amount of SO _{3 which} can be desorbed from the DOC 22a, that is, the total removable amount of SO ₃ is calculated by the following equation (21) with the current bed temperature T ₂ as a variable.

The estimating unit M5 substitutes the calculated total removable amount of SO ₂ into the following equation (22), and newly releases the amount of SO ₂ desorbed from the DOC 22a in the t-th cycle, that is, newly desorbed SO ₂ Calculate the quantity. Also, the calculated total removable SO ₃ amount is substituted into the following equation (23) to calculate the amount of newly released SO ₃ from the DOC 22 a in the t-th cycle, that is, the amount of newly removed SO ₃ Do. In addition, a setting value is used for the desorption rate of Formula (22) and (23), for example, it can be memorize | stored in ROM of ECU30.
New amount of desorbed SO ₂ (T ₂ (t), t) [μg] = desorbable total amount of SO ₂ [μg] × desorption rate (22)
New amount of desorbed SO ₃ (T ₂ (t), t) [μg] = desorbable total SO ₃ amount [μg] × desorption rate (23)

Next, a description will be given problems of estimation method of the current new desorption SOx amount using the bed temperature T _2. In the method described above, removable total SOx amount is expressed as the area between the current and the lower limit temperature TL in the adsorption after SOx distribution floor temperature T _2. However, the post-adsorption SOx distribution shown in FIG. 10 is premised on the condition that the rate of increase of the bed temperature is constant. For this reason, there is a possibility that the total removable SOx amount can not be accurately estimated under the condition that the rising speed of the bed temperature changes.

Therefore, in the system of the first embodiment adopts a method of estimating the current new desorption SOx amount change degree also considered to a value just not current bed temperature T ₂ of the floor temperature T _2. Hereinafter, the specific contents of the method for estimating the amount of newly released SOx will be described in detail.

  The SOx adsorbed to the DOC 22a includes those adsorbed near the surface layer of the coating material 22c of the DOC 22a and those adsorbed near the deep layer of the coating material 22c. While SOx adsorbed near the surface layer of the coating material 22c is desorbed with a relatively low energy, SOx adsorbed near the depth layer of the coating material 22c has a relatively high energy to desorb Is required. If SOx distribution after adsorption is considered on the premise of such knowledge, SOx adsorbed mainly in the vicinity of the surface of the coating material 22c can be desorbed on the low temperature side of the bed temperature at desorption, and the bed temperature at desorption is high On the side, it is considered that SOx adsorbed mainly in the vicinity of the depth of the coating material 22c can be desorbed.

Here, the temperature distribution inside the DOC 22a changes in a complex manner due to the heat received from the inflowing gas. More specifically, since the surface layer of the coating material 22c of the DOC 22a is a position directly exposed to the inflowing gas, the sensitivity to the temperature change of the inflowing gas is high. On the other hand, since the depth of the coating material 22c of the DOC 22a is a position not directly exposed to the inflowing gas, the sensitivity to the temperature change of the inflowing gas is low. Thus, removable SOx amount estimated using the SOx distribution after adsorption, the higher the current floor temperature T ₂ is the value of the low temperature side is considered to be deviate from the actual eliminable SOx amount. Therefore, it is conceivable to apply a correction to reflect the influence of temperature changes on the current floor temperature T _2, when subjected to uniform the correction based on the current low-temperature side of the bed temperature T _2, the current high-temperature side of the bed temperature T ₂ Correction may be excessive.

Therefore, in the system of the first embodiment, using the control logic described below, it is set to be currently corrected bed temperature T ₂ to be used to estimate the removable total SOx amount. FIG. 11 is a functional block diagram showing control logic for calculating the current bed temperature T ₂ ′ after correction. The correction unit M30 shown in this figure is a functional block configured as a part of the estimation unit M3, and is realized by the ECU 30. In the following description, it referred to as the uncorrected current current bed temperature T ₂ before correcting the bed temperature T _2, it is assumed that the corrected current bed temperature T ₂ of the corrected current referred to as bed temperature T _{2 '.}

As shown in this figure, the correction unit M30 includes a temperature change amount calculation unit M31, a temperature correction coefficient calculation unit M32, a lower limit guard unit M33, a correction value calculation unit M34, and a corrected current floor temperature calculation unit M35. And. The calculation unit M31 is before correction for each cycle currently bed temperature T ₂ is input. Uncorrected current floor temperature _T 2 which is input, as a representative temperature of DOC22a, outlet temperature of DOC22a detected by the temperature sensor 34 is used. Incidentally, the pre-correction current bed temperature T ₂ are, may be used directly detected value the temperature inside the DOC22a, may also be used bed temperature of DOC22a estimated using known techniques. The calculation unit M31, the current difference value between floor temperature _T 2 (t-1) of the t-th cycle of the current bed temperature _T 2 (t) and the (t-1) th cycle, i.e. the current bed temperature _{T 2} The difference value between the present value and the previous value is calculated as the temperature change amount ΔT. The temperature change amount ΔT is not limited to the above difference value as long as it represents a degree of change from the past value of the current bed temperature T ₂ before correction to the current value. For example, in order to eliminate the influence of noise superimposed uncorrected current floor temperature T _2, the average value of the current bed temperature T ₂ and _(t-1) and the current bed temperature T _{2 (t-2),} The difference value between the current bed temperature T ₂ (t) and the average value may be taken as the temperature change amount ΔT. In addition, another known smoothing process may be applied to the calculation of the temperature change amount ΔT.

  The calculated temperature change amount ΔT is input to the guard unit M33. In the guard portion M33, the temperature change amount ΔT is guarded at the lower limit value zero by selecting the fixed value zero and the maximum value of the temperature change amount ΔT.

The calculation unit M32, receives the uncorrected current inputs bed temperature T ₂ calculates the temperature correction coefficient K. Figure 12 shows an example of a map that associates a temperature correction coefficient K before correction current to the bed temperature T _2. The temperature correction coefficient K can be calculated, for example, from the map shown in FIG. In this map, the temperature correction coefficient K is set to a constant value (positive value) in a region where the current bed temperature T ₂ before correction is smaller than 400 ° C. The temperature correction coefficient K is set to zero in a region larger than 500 ° C. ing. Further, in this map, the uncorrected current floor temperature T ₂ is in between 500 ° C. from 400 ° C., as the temperature correction coefficient K current is large bed temperature T ₂ before correction is set to be smaller. As a result, the temperature correction coefficient K changes so as to be monotonically non-increasing as the current bed temperature T ₂ before correction increases. The calculation of the temperature correction coefficient K is not limited to the method using the map shown in FIG. Namely, before correction may be configured to use other maps smaller tendency defined by monotone nonincreasing accordance currently bed temperature T ₂ becomes large.

The temperature correction coefficient K and the temperature change amount ΔT are input to the calculation unit M34. In the calculation unit M34, a correction value (K × ΔT) is calculated by multiplying the temperature change amount ΔT by the temperature correction coefficient K. The correction value (K × ΔT) becomes smaller as the current bed temperature T ₂ before correction becomes larger, that is, as the temperature correction coefficient K becomes smaller. When the temperature correction coefficient K becomes zero, the correction value (K × ΔT) also becomes zero. Become.

The calculation unit M35 are uncorrected current bed temperature T ₂ and the correction value (K × ΔT) are inputted. In the calculation unit M35, the corrected current bed temperature T ₂ ′ is calculated by adding the correction value (K × ΔT) to the current bed temperature T ₂ before correction. Thus, pre-correction after a large correction for reflecting the degree of temperature variation ΔT the current floor temperature T _{2 'is} calculated when the current is small bed temperature T _2, the uncorrected temperature change when the current is large bed temperature T ₂ The current bed temperature T ₂ ′ after correction with which the degree of reflection of the amount ΔT is small is calculated. Thus, according to the process of the correction unit M30, it is possible to change the reflection degree of the temperature change ΔT in accordance with the magnitude of the correction before the current floor temperature T _2.

The control logic for calculating the current bed temperature T ₂ ′ after correction is not limited to the configuration of the above functional block. Namely, before correction in the control logic for calculating a corrected current floor temperature T _{2 'by} performing the current compensation to reflect the temperature variation ΔT in bed temperature T _2, the temperature variation ΔT uncorrected Currently bed temperature T ₂ The degree of reflection may be configured so as to be monotonically non-increasing and smaller as the pre-correction current bed temperature T ₂ becomes larger.

In the system of the first embodiment, the current floor temperature T ₂ of the corrected in the above equation (20) and (21) are used. As a result, in the temperature range where the current bed temperature is low, the degree of reflection of the temperature change amount ΔT on the current bed temperature can be increased, so the estimated removable SOx amount can be made closer to the actual removable SOx amount. In addition, since the degree of reflection of the temperature change amount ΔT on the current bed temperature is weakened in the temperature range where the current bed temperature is low, the removable SOx amount estimated by correcting the current bed temperature excessively is an actual removal It is possible to prevent separation from the amount of releasable SOx.

The removable SOx amount calculated in the above equations (20) and (21) is used to calculate the amount of newly released SO ₂ according to the above equations (22) and (23). This makes it possible to accurately estimate the amount of newly desorbed SO ₂ regardless of the degree of change in the current bed temperature.

  Returning to FIG. 3, the estimating unit M6 reflects the amount of newly desorbed SOx estimated by the estimating unit M5 in the post-adsorption SOx distribution to estimate the final adsorbed SOx distribution.

More specifically, assuming that the SOx is desorbed by the amount of the newly desorbed SOx estimated by the estimating unit M5 and the shape of the SOx distribution after adsorption is deformed, the estimation unit M6 determines the final adsorbed SOx distribution (SOx distribution after desorption) Estimate). The relationship between the final adsorbed SOx distribution and the SOx distribution after adsorption will be described with reference to FIG. 13 in which SO ₂ is taken as an example. FIG. 13 is a diagram for explaining the relationship between the final adsorbed SOx distribution and the SOx distribution after adsorption. Note that TL and TH on the horizontal axis of this figure respectively correspond to the lower limit temperature and the upper limit temperature described above. 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 a new desorption SO ₂ amount, i.e., from the lower limit temperature TL to a temperature _{Td SO2} the area, the distribution that remains after shaved from post-adsorption SOx distribution, the final adsorbed SO ₂ distribution.

When the above temperature _{Td SO2} floor temperature _{T 1} of the FIG. 13 means that the SO ₂ is all desorbed from DOC22a. Taking this into consideration, the final adsorbed SO ₂ distribution in the t-th cycle is expressed by the following equation (24) with the bed temperature T ₁ as a variable, and the final adsorbed SO ₃ distribution in the t-th cycle is It will be represented by). 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 state of SO ₃ among the above-mentioned through-holes SOx (hereinafter, also referred to as “the amount of through SO ₃ ”).

As described in FIG. 2, in the DOC 22 a, a part of SO ₂ adsorbed to the noble metal 22 d is converted to SO ₃ . Assuming that this conversion also occurs in SO ₂ in slip-through SOx, the estimation unit M 7 calculates the slip-through 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 quantity. The amount of SOx discharged from the DOC 22a in the state of SO ₂ among the slipped SOx (hereinafter, also referred to as “the amount of slipped SO ₂ ”) can be expressed by the following equation (29).
Amount of slipped SO ₃ (amount of slipped (t), T ₂ (t)) [μg / s] = amount of slipped SOx (t) × SO ₃ conversion map (T ₂ (t)) (28)
Amount of slipped SO ₂ (amount of slipped (t), T ₂ (t)) [μg / s] = amount of slipped SOx (t) × {1-SO ₃ conversion map (T ₂ (t))} 29)

The SO ₃ conversion map (T ₂ (t)) in the equations (28) and (29) is the SOx discharged from the DOC 22 a in the SO ₃ state out of “SO x flowing into the DOC 22 a” in the t th cycle. The ratio of SO ₂ (ie, SO ₃ conversion) is a map created based on the characteristic that it changes with the current bed temperature T _{2 of} DOC 22 a. FIG. 14 is a diagram for explaining the SO ₃ conversion map. Characteristics of SO ₃ conversion map, for example, as shown in FIG. 14, when in the temperature range B which currently have bed temperature T ₂ higher the SO ₃ conversion rate, low-temperature side and high temperature side than the temperature range B In this case, the conversion of SO ₂ to SO ₃ is less likely 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 22 a during the bed temperature rise of the DOC 22 a (hereinafter, also referred to as “the amount of allowable desorption SO ₃ ”). The amount of allowable desorption SO ₃ will be described with reference to FIG. FIG. 15 is a diagram for explaining the amount of allowable desorption SO ₃ . The amount of restricted SO ₃ shown in this figure corresponds to the restriction on sulfate white smoke, and in this figure, the sum of the amount of through SO _{3 and the} amount of allowable desorption SO ₃ is equal to the amount of restricted SO ₃ . Since the sum of the through SO ₃ amount and the allowable desorption SO ₃ amount is the amount of SO ₃ downstream of the DOC 22a, if the value of this sum is smaller than the restriction SO ₃ amount, the restriction is satisfied. Become.

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

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

Returning to FIG. 3, the calculation unit M9 calculates the target bed temperature Ttrg in the t-th cycle for suppressing the generation of sulfate white smoke during the PM regeneration control. The target bed temperature Ttrg will be described with reference to FIG. FIG. 16 is a diagram for explaining the target bed temperature Ttrg. Note that TL and TH on the horizontal axis of this figure respectively correspond to the lower limit temperature and the upper limit temperature described above. As shown in this figure, the bed temperature T ₁ when the value obtained by multiplying the integrated value from the low temperature side of the final adsorbed SO ₃ distribution by the desorption rate matches the allowable desorption SO ₃ amount calculated by the calculation unit M ₈ Corresponds to the target bed temperature Ttrg.

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

The effects of the present embodiment will be described with reference to FIG. FIG. 17 is a time chart for explaining the effect of the temperature correction of the current bed temperature. The first stage of the chart of the figure shows the correction before the current floor temperature T ₂ of the corrected current time change of bed temperature T _{2 ',} respectively. The second chart shows the estimated value and the measured value of the newly desorbed SO ₃ amount when the current bed temperature T ₂ before correction is used. As shown in these charts, in the region of the current high-temperature side of the bed temperature T ₂ is a correction degree current for bed temperature T ₂ is smaller. This makes it possible to close the currently measured value of the estimated value of the new desorbed SO ₃ content by suppressing excessive correction in the high temperature side region of the floor temperature T _2.

In the embodiment described above, the estimation unit M1 corresponds to the "inflow SOx amount estimation means" of the present invention, the estimation unit M2 corresponds to the "SOx saturation rate estimation means" of the present invention, and the estimation unit M3 The estimation unit M4 corresponds to the "post-adsorption SOx distribution estimation unit" of the present invention, and the estimation unit M5 corresponds to the "newly adsorbed SOx amount estimation unit" and the "pass through SOx amount estimation unit" of the present invention. The estimating unit M6 corresponds to the "final adsorbed SOx distribution estimating unit" of the present invention, and the estimating unit M7 corresponds to the "through-SO ₃ amount estimating unit" of the present invention. calculator M8 corresponds to the "acceptable desorption SO ₃ amount calculation means" of the present invention, calculation unit M9 is equivalent to the "target temperature calculation unit" of the present invention.

Further, in the embodiment described above, the current corresponds to the "representative temperature" bed temperature T ₂ and the uncorrected current floor temperature T ₂ the present invention, the corrected current floor temperature T ₂ "corrected representative of the present invention The temperature correction coefficient K corresponds to the "correction coefficient" of the present invention, the temperature change amount ΔT corresponds to the "correction value" of the present invention, and the calculation unit M31 corresponds to the "calculation means" of the present invention. The calculation unit M35 corresponds to the "correction unit" of the present invention.

By the way, in the embodiment described above, PM regeneration control is performed by the addition of fuel from the fuel addition valve 24. However, the PM regeneration control may be performed by injection of fuel from the injector 12 (specifically, sub injection (for example, post injection) after main injection). In this case, the exhaust gas addition amount of the formula (1) may be replaced with the sub injection amount from the injector 12.
Moreover, in embodiment mentioned above, target temperature of bed temperature of DOC22a was computed taking PM regeneration control as an example. However, when control to release SOx from the DOC 22a is performed in combination with PM regeneration control, the target temperature of the bed temperature of the DOC 22a may be calculated by the method described above during this desorption control. As described above, the calculation method of the target temperature described above can be generally applied to control for raising the bed temperature of the DOC 22a to a temperature range where the DOC 22a releases SOx.
Further, in the embodiment described above, the exhaust gas control apparatus 22 including the DOC 22a and the DPF 22b has been described as an example. However, the DOC 22a may be omitted from the exhaust gas purification device 22 by providing the DPF 22b with an oxidation function such as HC in the DOC 22a. In this case, the same effect as that of the above-described embodiment can be obtained by applying the calculation method of the target temperature described above to the DPF 22b to which the oxidation function is added.
Further, although the engine 10 includes the turbocharger 16 in the above-described embodiment, the engine 10 may not include the turbocharger 16. That is, the calculation method of the target temperature mentioned above is applicable also to the system of a non-supercharged diesel engine.

Reference Signs List 10 diesel engine 12 injector 20 exhaust pipe 22 exhaust purification device 22a DOC
22b DPF
22c Coating material 22d Precious metal 24 Fuel addition valve 30 ECU

Claims (7)

An engine control apparatus that executes temperature increase control to raise 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,
Temperature acquisition means for acquiring a representative temperature which is a representative value of the temperature of the purifier at predetermined control cycles;
Inflow SOx amount estimation means for estimating the amount of SOx flowing into the purification device as the amount of inflow SOx every control cycle;
New desorbed SOx amount estimating means for estimating the amount of SOx newly desorbed from the purifier as the newly desorbed SOx amount for each control cycle using the inflow SOx amount and the representative temperature;
The final adsorbed SOx distribution represented as a graph in which the amount of SOx which is finally adsorbed to the purifier at each temperature rise of the purifier using the newly desorbed SOx amount is shown as a graph associated with the representative temperature Final adsorbed SOx distribution estimation means for estimating for each control period;
Target temperature calculation means for calculating the target temperature for each control cycle using the final adsorption SOx distribution and the allowable desorption SO ₃ amount;
The new desorption SOx amount estimating means is
Calculating means for calculating a correction value representing the degree of change from the past value of the representative temperature to the current value;
And correcting means for calculating a representative temperature after correction by performing correction to reflect the correction value on the representative temperature, and estimating the amount of newly desorbed SOx using the amount of inflow SOx and the representative temperature after correction. Configured to
The correction means may be configured such that the degree of reflection of the degree of change on the corrected representative temperature decreases monotonically and non-increasingly as the representative temperature increases. The correction means is
Calculating a correction coefficient that decreases monotonically and not as the representative temperature increases;
The engine control apparatus according to claim 1, wherein the representative temperature after correction is calculated by adding a value obtained by multiplying the correction value by the correction coefficient to the representative temperature.   The engine control device according to claim 1, wherein the calculation unit is configured to calculate a difference between the current value of the representative temperature and the previous value as the correction value. The adsorbed SOx distribution represented as a graph in which the amount of SOx adsorbed to the purifier at each temperature rise of the purifier is associated with the representative temperature, and the purifier at each temperature during the temperature rise of the purifier SOx saturation ratio estimation means for estimating the SOx saturation ratio in the purifier at each control cycle using a saturated SOx distribution represented as a graph in which the maximum amount of SOx adsorbed to the SOx is associated with the representative temperature;
New adsorbed SOx amount estimating means for estimating the amount of SOx which flows into the purifier and is newly adsorbed to the purifier using the inflow SOx amount and the SOx saturation rate as a new adsorbed SOx amount for each control cycle When,
Post-adsorption SOx distribution estimating means for estimating the adsorbed SOx distribution after the new SOx is adsorbed to the purification device as the post-adsorption SOx distribution for each control cycle using the newly adsorbed SOx amount;
The novel desorbed SOx amount estimating means is configured to estimate the amount of the newly desorbed SOx for each of the control cycles using the SOx distribution after adsorption and the representative temperature. The engine control device according to any one of Items 1 to 3. A slipped SOx amount estimating unit that estimates the SOx amount that flows into the purification device and slips without being adsorbed to the purification device using the newly adsorbed SOx amount as the slipped SOx amount for each control cycle;
The conversion map representing the relationship between the conversion rate of SO ₂ to be converted to SO ₃ in the purification device and the representative temperature, the representative temperature in the present estimation cycle, and the amount of SOx passed through, slipped SO ₃ amount estimating means for estimating for each of the control period as the SO ₃ content slipped through SO ₃ amount discharged in the form of SO ₃ to pass through without the purifying device and flows in the form of SOx adsorbed to the purifier When,
Using the SO ₃ content slipping said the SO ₃ content in the downstream of the purification device corresponding to constraints on sulfate white smoke, the purifying device wherein the SO ₃ amount that is allowed to detach from the allowable desorption SO ₃ weight And an allowable desorbed SO ₃ amount calculating means which is calculated for each control cycle as
The engine control device according to claim 4, further comprising:   The said temperature acquisition means is comprised so that the temperature of the gas which flowed to the downstream of the said purification apparatus in the said exhaust pipe may be acquired as said representative temperature, The said any one of the Claims 1 to 5 characterized by the above-mentioned. The engine control device according to claim 1. The purification device includes a filter that collects particulates flowing through the exhaust pipe,
The control according to any one of claims 1 to 6, wherein the control to raise the temperature to the target temperature is started when the estimated value of the amount of particulates collected by the filter reaches a removal requirement amount. Engine control unit.

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