Exhaust emission control device and exhaust emission control method

Abstract

To remove SOx adhered to a catalyst at appropriate timing.SOLUTION: An exhaust emission control device 20 includes: an estimating unit 222 for estimating an estimated value of NOx purification rate of a catalyst 13 on the basis of a first amount of NOx contained in exhaust gas flowing upstream of the catalyst 13, an injection amount of urea water injected to the exhaust gas, and a temperature of the catalyst 13; an actual measurement unit 223 for specifying an actual measurement value of the NOx purification rate of the catalyst 13 on the basis of the first amount of NOx, and a second amount of NOx contained in the exhaust gas which has passed through the catalyst 13; and a temperature control unit 224 which raises a temperature of the exhaust gas flowing upstream of the catalyst 13 to a first temperature to remove SOx contained in the exhaust gas when a differential value between the estimated value of the NOx purification rate and the actual measurement value of the NOx purification rate is equal to or larger than a threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification control device and an exhaust gas purification control method. [Background technology]

[0002] The exhaust purification device of Patent Document 1 removes sulfur oxides adhering to the catalyst by raising the exhaust temperature at predetermined intervals, and suppresses a decrease in the NOx purification rate caused by ammonia contained in urea water injected into the exhaust to reduce NOx adhering to sulfur oxides instead of adhering to the catalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-176429 Summary of the Invention [Problem to be solved by the invention]

[0004] The exhaust purification device of Patent Document 1 does not remove sulfur oxides (so-called SOx) until a predetermined period of time has elapsed, even if the SOx has adhered to the catalyst. Therefore, the longer the time from when SOx adhered to the catalyst until the predetermined period of time has elapsed, the longer the time for which the NOx purification rate decreases becomes a problem.

[0005] The present invention has been made in view of these points, and has as its object to remove SOx adhering to a catalyst at an appropriate timing. [Means for solving the problem]

[0006] An exhaust purification control device according to a first aspect of the present invention includes an estimation unit that estimates an estimated value of the NOx purification rate of the catalyst based on a first amount of NOx contained in exhaust gas flowing upstream of a catalyst, an injection amount of urea water to be injected into the exhaust, and the temperature of the catalyst; an actual measurement unit that determines an actual measured value of the NOx purification rate of the catalyst based on the first amount and a second amount of NOx contained in exhaust gas that has passed through the catalyst; and a temperature control unit that, when a difference between the estimated value and the actual measured value is equal to or greater than a threshold value, raises the temperature of the exhaust gas flowing upstream of the catalyst to a first temperature for removing SOx contained in the exhaust gas.

[0007] The temperature control unit may start increasing the temperature to the first temperature at a timing when the difference value changes from less than the threshold value to equal to or greater than the threshold value.

[0008] The temperature control unit may raise the temperature of the exhaust gas flowing upstream of the catalyst to the first temperature until the difference value changes from equal to or greater than the threshold value to less than the threshold value.

[0009] The estimation unit may estimate an estimated adsorption amount of ammonia adsorbed on the catalyst out of the ammonia contained in the urea water based on the first amount, the injection amount of the urea water, and the temperature of the catalyst, and may estimate the estimated value based on the estimated adsorption amount and the first amount.

[0010] The estimation unit may increase the estimated amount of adsorption as the temperature of the catalyst decreases.

[0011] The estimation unit may increase the estimated amount of adsorption as the first amount increases.

[0012] The temperature control unit may divide the actual measurement value by the estimated value, and subtract the resulting quotient from 1 to calculate the difference value.

[0013] When the difference value is less than the threshold value, the temperature control unit may raise the temperature of the exhaust gas flowing upstream of the catalyst to a second temperature lower than the first temperature in order to remove particulate matter adhering to a filter that captures particulate matter contained in the exhaust gas.

[0014] An exhaust purification control method according to a second aspect of the present invention includes an estimation step of estimating an estimated value of the NOx purification rate of the catalyst based on a first amount of NOx contained in exhaust gas flowing upstream of a catalyst, an injection amount of urea water to be injected into the exhaust, and the temperature of the catalyst; an actual measurement step of determining an actual measured value of the NOx purification rate of the catalyst based on the first amount and a second amount of NOx contained in exhaust gas that has passed through the catalyst; and a temperature control step of raising the temperature of the exhaust gas flowing upstream of the catalyst to a first temperature for removing SOx contained in the exhaust gas when the difference between the estimated value and the actual measured value is greater than or equal to a threshold value. [Effects of the Invention]

[0015] According to the present invention, it is possible to effectively remove SOx adhering to the catalyst at an appropriate timing. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram for explaining an overview of a vehicle S according to the present embodiment. [Figure 2] 3 is a diagram showing an example of an estimated adsorption amount map stored in a storage unit 21. FIG. [Figure 3] 3 is a diagram showing an example of a purification rate map stored in a storage unit 21. FIG. [Figure 4] 4 is a diagram showing the operation of the exhaust purification control device 20 to remove SOx. FIG. [Figure 5] FIG. 10 is a diagram illustrating an operation of the temperature control unit 224 for calculating a difference value. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Overview of Vehicle S> Fig. 1 is a diagram illustrating an overview of a vehicle S according to this embodiment. The vehicle S shown in Fig. 1 includes an exhaust flow path 10, a filter 11, a fuel injection nozzle 12, a catalyst 13, an NH3 sensor 14, a temperature sensor 15, a first NOx sensor 16, a second NOx sensor 17, a urea water injection nozzle 18, and an exhaust purification control device 20. The vehicle S has the function of collecting particulate matter (PM) contained in the exhaust of an engine (not shown) and purifying nitrogen oxides (so-called NOx) contained in the exhaust.

[0018] The filter 11 is provided downstream of the engine and upstream of the catalyst 13 in the exhaust flow path 10 through which the exhaust flows in the direction D, and is, for example, a DPF (Diesel Particulate Filter). The filter 11 includes an oxidation catalyst that oxidizes hydrocarbons and carbon monoxide contained in the exhaust, and a filter for collecting PM contained in the exhaust. The fuel injection nozzle 12 is a device that injects fuel to supply fuel to the oxidation catalyst contained in the filter 11.

[0019] The catalyst 13 is provided downstream of the filter 11 in the exhaust flow path 10 and is, for example, an SCR (Selective Catalytic Reduction) catalyst. The catalyst 13 adsorbs ammonia contained in urea water injected into the exhaust gas by a urea water injection nozzle 18 provided upstream of the catalyst 13 in the exhaust flow path 10, and purifies the NOx by reacting the ammonia with the NOx contained in the exhaust gas to generate water and nitrogen.

[0020] The NH3 sensor 14, temperature sensor 15, and first NOx sensor 16 are sensors provided in the exhaust flow path 10 downstream of the filter 11 and upstream of the catalyst 13. The NH3 sensor 14 detects the concentration of ammonia contained in the exhaust. The temperature sensor 15 detects the temperature of the inlet through which the exhaust flows into the catalyst 13. The first NOx sensor 16 detects the concentration of NOx contained in the exhaust flowing upstream of the catalyst 13. The second NOx sensor 17 is provided in the exhaust flow path 10 downstream of the catalyst 13, and is a sensor that detects the concentration of NOx contained in the exhaust that has passed through the catalyst 13.

[0021] The exhaust gas purification control device 20 is a device for removing PM trapped by the filter 11. The exhaust gas purification control device 20 removes the PM trapped by the filter 11 (so-called DPF regeneration) by, for example, raising the temperature of the exhaust gas flowing through the exhaust passage 10 and causing heat exchange between the exhaust gas and the filter 11. The exhaust gas purification control device 20 may have a housing containing electronic components, or may be a printed circuit board on which electronic components are mounted.

[0022] Incidentally, unburned fuel (unburned gas) contained in the exhaust gas of the engine contains sulfur oxides (so-called SOx). The catalyst 13 adsorbs SOx contained in the exhaust gas in addition to ammonia contained in the urea water injected by the urea water injection nozzle 18. When SOx is adsorbed by the catalyst 13, the ammonia is adsorbed onto the SOx, and the amount of ammonia adsorbed by the catalyst 13 decreases, thereby reducing the NOx purification rate of the catalyst 13.

[0023] Therefore, when the exhaust purification control device 20 determines that a predetermined amount of SOx has adhered to the catalyst 13 (so-called sulfur poisoning state), it removes the SOx adhered to the catalyst 13. The exhaust purification control device 20 removes the SOx adhered to the catalyst 13, for example, by raising the temperature of the exhaust gas flowing through the exhaust passage 10 and causing heat exchange between the exhaust gas and the catalyst 13. By operating in this manner, the exhaust purification control device 20 can remove the SOx adhered to the catalyst 13 at an appropriate timing, thereby suppressing a decrease in the NOx purification rate of the catalyst 13.

[0024] <Configuration of exhaust gas purification control device 20> 1, the exhaust gas purification control device 20 includes a storage unit 21 and a control unit 22. The control unit 22 includes an acquisition unit 221, an estimation unit 222, a measurement unit 223, and a temperature control unit 224.

[0025] The storage unit 21 has a storage medium such as a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), or an SSD (Solid State Drive). The storage unit 21 stores a program executed by the control unit 22 and a program for the exhaust purification control device 20 to detect PM and It stores various information for removing SOx.

[0026] The control unit 22 is a processor such as a CPU (Central Processing Unit) or an ECU (Electronic Control Unit). The control unit 22 executes a program stored in the storage unit 21 to function as an acquisition unit 221, an estimation unit 222, a measurement unit 223, and a temperature control unit 224. The control unit 22 may be configured with one processor, or may be configured with multiple processors or a combination of one or more processors and an electronic circuit.

[0027] The acquisition unit 221 acquires various types of information from outside the exhaust purification control device 20. For example, the acquisition unit 221 acquires the ammonia concentration detected by the NH3 sensor 14, and identifies the injection amount of urea water corresponding to the amount of ammonia based on the engine intake amount detected by an air flow sensor (not shown) provided in the vehicle S and the ammonia concentration. The acquisition unit 221 acquires, for example, the temperature detected by the temperature sensor 15 as the temperature of the catalyst 13.

[0028] The acquisition unit 221 acquires, for example, the NOx concentration detected by the first NOx sensor 16, and determines a first amount of NOx contained in the exhaust gas flowing upstream of the catalyst 13 based on the intake air volume of the engine and the NOx concentration. The acquisition unit 221 acquires, for example, the NOx concentration detected by the second NOx sensor 17, and determines a second amount of NOx contained in the exhaust gas that has passed through the catalyst 13 based on the intake air volume of the engine and the NOx concentration.

[0029] The estimation unit 222 estimates an estimated value of the NOx purification rate of the catalyst 13 based on a first amount of NOx contained in the exhaust gas flowing upstream of the catalyst 13, the injection amount of urea water injected into the exhaust gas, and the temperature of the catalyst 13. The estimated value of the NOx purification rate is the NOx purification rate of the catalyst 13 in a state where no SOx adheres to the catalyst 13. For example, the estimation unit 222 estimates an estimated adsorption amount of ammonia adsorbed on the catalyst 13 out of the ammonia contained in the urea water, based on the first amount of NOx, the injection amount of the urea water, and the temperature of the catalyst 13. Then, the estimation unit 222 estimates the estimated value of the NOx purification rate based on the estimated adsorption amount and the first amount of NOx.

[0030] The estimation unit 222 estimates the estimated adsorption amount of ammonia corresponding to the first amount of NOx, the injection amount of urea water, and the temperature of the catalyst 13, for example, by referring to an estimated adsorption amount map stored in the memory unit 21. Fig. 2 is a diagram showing an example of the estimated adsorption amount map stored in the memory unit 21. For ease of explanation, Fig. 2 shows the estimated adsorption amount map including the estimated adsorption amount corresponding to the first amount of NOx ("NOx first amount" shown in Fig. 2) and the temperature of the catalyst 13 ("catalyst temperature" shown in Fig. 2).

[0031] The catalyst 13 adsorbs a larger amount of ammonia as the temperature is lower. Therefore, as shown in FIG. 2, the estimation unit 222 increases the estimated adsorption amount as the temperature of the catalyst 13 decreases. Furthermore, the urea water injection nozzle 18 injects more urea water as the amount of NOx contained in the exhaust gas increases. Therefore, as shown in FIG. 2, the estimation unit 222 increases the estimated adsorption amount as the first amount of NOx increases. By operating in this manner, the estimation unit 222 can estimate the estimated adsorption amount with high accuracy.

[0032] The estimation unit 222 estimates an estimated value of the NOx purification rate corresponding to the estimated adsorption amount and the first amount of NOx, for example, by referring to a purification rate map stored in the storage unit 21. Fig. 3 is a diagram showing an example of the purification rate map stored in the storage unit 21. As shown in Fig. 3, the purification rate map includes estimated values ​​of the NOx purification rate corresponding to the estimated adsorption amount and the first amount of NOx. As shown in Fig. 3, the estimation unit 222 increases the estimated value as the estimated adsorption amount increases, and increases the estimated value as the first amount of NOx decreases.

[0033] The measurement unit 223 determines the actual value of the NOx purification rate of the catalyst 13 based on the first amount of NOx and the second amount of NOx contained in the exhaust gas that has passed through the catalyst 13. The measurement unit 223, for example, calculates a quotient by dividing the second amount of NOx by the first amount of NOx, and then determines the actual value of the NOx purification rate by subtracting the quotient from 1 and converting the result into a percentage.

[0034] When the difference between the estimated value of the NOx purification rate and the actual measured value of the NOx purification rate is equal to or greater than a threshold value, the temperature control unit 224 raises the temperature of the exhaust gas flowing upstream of the catalyst 13 to a first temperature for removing SOx contained in the exhaust gas. The threshold value is the minimum value at which it can be determined that the catalyst 13 has deteriorated due to sulfur poisoning of the catalyst 13 and that the NOx purification rate has decreased, and is, for example, 10% (0.1 when the purification rate is expressed as a percentage). The first temperature is, for example, 650°C.

[0035] For example, if the difference value is equal to or greater than a threshold value, the temperature control unit 224 determines the target temperature of the exhaust gas to be the first temperature. Then, for example, the temperature control unit 224 supplies fuel to the oxidation catalyst included in the filter 11 by injecting an amount of fuel corresponding to the target temperature (first temperature) from the fuel injection nozzle 12, and raises the temperature of the exhaust gas with the heat generated when the oxidation catalyst oxidizes the fuel.

[0036] By operating as described above, the temperature control unit 224 can determine that the catalyst 13 is sulfur-poisoned and can raise the temperature of the exhaust gas based on the difference between the NOx purification rate when no SOx is adhering to the catalyst 13 and the NOx purification rate at the current time. Then, in the vehicle S, from the point in time when the temperature control unit 224 determines that the catalyst 13 is sulfur-poisoned, heat exchange is performed between the heated exhaust gas and the catalyst 13, thereby causing the SOx to be desorbed from the catalyst 13. In this way, the temperature control unit 224 can remove the SOx by desorbing the SOx adhering to the catalyst 13 at an appropriate timing.

[0037] For example, the temperature control unit 224 starts raising the temperature to the first temperature when the difference value changes from less than the threshold value to greater than or equal to the threshold value, and raises the temperature of the exhaust gas flowing upstream of the catalyst 13 to the first temperature until the difference value changes from greater than or equal to the threshold value to less than the threshold value. By operating in this manner, the temperature control unit 224 can start raising the temperature of the exhaust gas from the time it is determined that the catalyst 13 is in a sulfur-poisoned state, and stop raising the temperature of the exhaust gas when it is determined that the sulfur-poisoned state has been resolved. As a result, the temperature control unit 224 can set the time for raising the temperature of the exhaust gas to a time appropriate for removing SOx, thereby suppressing unnecessary use of fuel or electricity used for removing SOx.

[0038] If the difference value is less than the threshold value, the temperature control unit 224 raises the temperature of the exhaust gas flowing upstream of the catalyst 13 to a second temperature lower than the first temperature in order to remove PM adhering to the filter 11 that collects PM contained in the exhaust gas. When the first temperature is 650°C, the second temperature is, for example, 600°C.

[0039] For example, if the difference value is less than the threshold value, the temperature control unit 224 determines the target temperature of the exhaust gas to be the second temperature. Then, for example, if the time at which the difference value is calculated is a time when a predetermined period has elapsed, the temperature control unit 224 raises the temperature of the exhaust gas to the target temperature (second temperature). The predetermined period is the period at which the vehicle S performs DPF regeneration. By operating in this manner, the temperature control unit 224 can remove PM adhering to the filter 11 at the predetermined period.

[0040] Note that temperature control unit 224 may calculate the difference value by dividing the actual measurement value of the NOx purification rate by the estimated value of the NOx purification rate and subtracting the resulting quotient from 1. Specifically, when the actual measurement value is 60% and the estimated value is 80%, temperature control unit 224 calculates the difference value as 0.25 by subtracting the quotient 0.75 from 1. Then, since the subtraction value 0.25 is equal to or greater than the threshold value 0.1, temperature control unit 224 determines the target temperature to be the first temperature and raises the temperature of the exhaust gas to the target temperature.

[0041] By operating as described above, the temperature control unit 224 can narrow the range of actual measurement values ​​for determining that the catalyst 13 is not in a sulfur-poisoned state as the estimated value of the NOx purification rate becomes smaller, making it easier to determine that the catalyst 13 is in a sulfur-poisoned state. Specifically, when the threshold value is 0.1, the temperature control unit 224 determines that the catalyst 13 is in a sulfur-poisoned state when the actual measurement value is 81% or less compared to the estimated value of 90%, and determines that the catalyst 13 is in a sulfur-poisoned state when the actual measurement value is 54% or less compared to the estimated value of 60%. As a result, the temperature control unit 224 makes it easier to remove SOx adhering to the catalyst 13 as the estimated value of the NOx purification rate decreases, and improves the NOx purification rate, thereby enabling SOx to be removed at a more appropriate timing than when a difference value is used, which is the difference value obtained by subtracting the actual measurement value from the estimated value.

[0042] <Processing sequence in exhaust purification control device 20> Figures 4 and 5 are diagrams showing an example of a processing sequence in the exhaust purification control device 20. Figure 4 is a diagram showing the operation of the exhaust purification control device 20 to remove SOx, and Figure 5 is a diagram showing the operation of the temperature control unit 224 to calculate a difference value. The processing sequence shown in Figure 5 is a sub-process of the processing sequence shown in Figure 4, and corresponds to step S11 and step S15 shown in Figure 4.

[0043] As shown in Fig. 4, the temperature control unit 224 calculates a difference between the estimated value of the NOx purification rate and the actual measured value of the NOx purification rate (S11). Here, the operation of the temperature control unit 224 to calculate the difference will be described with reference to Fig. 5. The acquisition unit 221 acquires the first amount of NOx, the second amount of NOx, the injection amount of urea water, and the temperature of the catalyst 13 (S21). The estimation unit 222 estimates an estimated adsorption amount of ammonia based on the first amount of NOx, the injection amount of urea water, and the temperature of the catalyst 13 (S22), and estimates an estimated value of the NOx purification rate based on the estimated adsorption amount and the second amount of NOx (S23).

[0044] The actual measurement unit 223 identifies the actual measurement value of the NOx purification rate based on the first amount of NOx and the second amount of NOx (S24). The temperature control unit 224 calculates a quotient by dividing the actual measurement value of the NOx purification rate by the estimated value of the NOx purification rate (S25). The temperature control unit 224 subtracts the calculated quotient from 1 to calculate the difference value between the estimated value of the NOx purification rate and the actual measurement value of the NOx purification rate (S26).

[0045] Returning to FIG. 4, if the calculated difference value is less than the threshold value (NO in S12), the temperature control unit 224 determines that the catalyst 13 is not in a sulfur-poisoned state and sets the target temperature to the second temperature (S18). Then, the exhaust purification control device 20 ends the processing. If the difference value is less than the threshold value (NO in S12), the temperature control unit 224 may raise the temperature of the exhaust gas to the second temperature for a predetermined time, on the condition that the time at which the difference value is calculated is a time when a predetermined period has elapsed. Then, the temperature control unit 224 may stop raising the temperature after the predetermined time has elapsed, and end the processing.

[0046] If the calculated difference value is equal to or greater than the threshold value (YES in S12), the temperature control unit 224 determines that the catalyst 13 is in a sulfur-poisoned state and sets the target temperature to the first temperature (S13). Then, the temperature control unit 224 raises the temperature of the exhaust gas to the first temperature, which is the target temperature (S14). In this way, by the temperature control unit 224 raising the temperature of the exhaust gas to the first temperature, SOx is desorbed from the catalyst 13 that has exchanged heat with the exhaust gas, and therefore the SOx adhering to the catalyst 13 is removed.

[0047] The temperature control unit 224 updates the difference value by calculating the difference value at the time after executing the process of step S14 (S15). If the updated difference value is equal to or greater than the threshold value (NO in S16), the temperature control unit 224 repeats the processes of steps S14 and S15. If the updated difference value is less than the threshold value (YES in S16), the temperature control unit 224 determines that the SOx adhering to the catalyst 13 has been removed, and stops increasing the temperature of the exhaust gas (S17). The temperature control unit 224 stops increasing the temperature of the exhaust gas, for example, by stopping the injection of fuel from the fuel injection nozzle 12. The temperature control unit 224 determines the target temperature to be the second temperature (S18), and ends the process.

[0048] <First Modification> In the above description, the temperature control unit 224 has been described as increasing the temperature of the exhaust gas by injecting fuel from the fuel injection nozzle 12 provided upstream of the filter 11 in the exhaust flow path 10, but the present invention is not limited to this. The temperature control unit 224 may supply fuel to the oxidation catalyst included in the filter 11 and increase the temperature of the exhaust gas by injecting an amount of fuel corresponding to a target temperature from an injector (not shown) included in the common rail during the expansion stroke of the engine.

[0049] <Second Modification> In the above description, the temperature control unit 224 has been described as raising the temperature of the exhaust gas by supplying fuel to the oxidation catalyst contained in the filter 11, but the present invention is not limited to this. The temperature control unit 224 may raise the temperature of the exhaust gas by heating a heating device such as a heater (not shown) provided in the exhaust flow path 10.

[0050] <Effects of the exhaust purification control device 20> As described above, the exhaust purification control device 20 has an estimation unit 222 that estimates an estimated value of the NOx purification rate of the catalyst 13 based on a first amount of NOx contained in the exhaust gas flowing upstream of the catalyst 13, the amount of urea water injected into the exhaust gas, and the temperature of the catalyst 13; an actual measurement unit 223 that determines an actual measured value of the NOx purification rate of the catalyst 13 based on the first amount of NOx and a second amount of NOx contained in the exhaust gas that has passed through the catalyst 13; and a temperature control unit 224 that raises the temperature of the exhaust gas flowing upstream of the catalyst 13 to a first temperature for removing SOx contained in the exhaust gas when the difference between the estimated value of the NOx purification rate and the actual measured value of the NOx purification rate is equal to or greater than a threshold value.

[0051] By configuring the exhaust purification control device 20 in this manner, the exhaust purification control device 20 can identify the sulfur-poisoning state of the catalyst 13 based on the difference between the estimated value of the NOx purification rate when no SOx is adhering to the catalyst 13 and the actual measured value of the NOx purification rate at the current time. Then, when it is identified that the catalyst 13 is in a sulfur-poisoning state (i.e., when the difference value is equal to or greater than a threshold), the temperature of the exhaust gas is raised to remove SOx and eliminate the sulfur poisoning of the catalyst 13. In this way, the exhaust purification control device 20 can remove SOx adhering to the catalyst 13 at an appropriate timing, thereby suppressing a decrease in the NOx purification rate of the catalyst 13.

[0052] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0053] S vehicle 10 Exhaust flow path 11 Filters 12 fuel injection nozzle 13 Catalyst 14 NH3 sensor 15 Temperature Sensor 16 No. 1 NOx sensor 17 Second NOx sensor 18 Urea water injection nozzle 20 Exhaust gas purification control device 21 Memory section 22 Control Unit 221 Acquisition Department 222 Estimation Department 223 Measurement Section 224 Temperature control unit

Claims

1. an estimation unit that estimates an estimated value of a NOx purification rate of the catalyst based on a first amount of NOx contained in exhaust gas flowing upstream of a catalyst, an injection amount of urea water to be injected into the exhaust gas, and a temperature of the catalyst; a measuring unit that determines an actual measurement value of a NOx purification rate of the catalyst based on the first amount and a second amount of NOx contained in the exhaust gas that has passed through the catalyst; a temperature control unit that, when a difference between the estimated value and the actual measurement value is equal to or greater than a threshold value, raises a temperature of the exhaust gas flowing upstream of the catalyst to a first temperature for removing SOx contained in the exhaust gas. Exhaust purification control device.

2. the temperature control unit starts increasing the temperature to the first temperature at a timing when the difference value changes from less than the threshold value to equal to or greater than the threshold value. The exhaust gas purification control device according to claim 1.

3. the temperature control unit increases the temperature of the exhaust gas flowing upstream of the catalyst to the first temperature until the difference value changes from equal to or greater than the threshold value to less than the threshold value. The exhaust gas purification control device according to claim 1.

4. the estimation unit estimates an estimated adsorption amount of ammonia adsorbed on the catalyst out of the ammonia contained in the urea water based on the first amount, the injection amount of the urea water, and a temperature of the catalyst, and estimates the estimated value based on the estimated adsorption amount and the first amount. The exhaust gas purification control device according to claim 1.

5. the estimation unit increases the estimated adsorption amount as the temperature of the catalyst decreases; The exhaust gas purification control device according to claim 4.

6. the estimation unit increases the estimated amount of adsorption as the first amount increases, The exhaust gas purification control device according to claim 4.

7. the temperature control unit calculates the difference value by dividing the actual measurement value by the estimated value and subtracting the result from 1; The exhaust gas purification control device according to claim 1.

8. When the difference value is less than the threshold value, the temperature control unit raises the temperature of the exhaust gas flowing upstream of the catalyst to a second temperature lower than the first temperature in order to remove particulate matter adhering to a filter that traps particulate matter contained in the exhaust gas. The exhaust gas purification control device according to claim 1.

9. an estimation step of estimating an estimated value of a NOx purification rate of the catalyst based on a first amount of NOx contained in exhaust gas flowing upstream of a catalyst, an injection amount of urea water to be injected into the exhaust gas, and a temperature of the catalyst; an actual measurement step of determining an actual measurement value of a NOx purification rate of the catalyst based on the first amount and a second amount of NOx contained in the exhaust gas that has passed through the catalyst; a temperature control step of raising the temperature of the exhaust gas flowing upstream of the catalyst to a first temperature for removing SOx contained in the exhaust gas when the difference between the estimated value and the actual measurement value is equal to or greater than a threshold value. Exhaust gas purification control method.

Images