Control device, control method, and exhaust purification system

Abstract

One embodiment of the present invention is a control device for controlling the injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, wherein the control device comprises: a pre-correction injection amount calculation unit, which calculates the pre-correction injection amount of the reducing agent based on the operating state of the internal combustion engine; and an injection amount correction unit, which calculates a corrected injection amount after the pre-correction injection amount based on the time rate of change of the rotational speed of the internal combustion engine and the time rate of change of the fuel injection amount of the internal combustion engine in such a manner that the injection amount of the reducing agent increases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are positive, and decreases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are negative.

Description

Technical Field

[0001] The present invention relates to a control device, a control method and an exhaust gas purification system.

[0002] This application claims priority from Japanese Patent Application No. 2021-037402 filed in Japan on March 9, 2021, the contents of which are incorporated herein by reference. Background Art

[0003] Patent Document 1 describes the following exhaust gas purification control system. Specifically, the exhaust gas purification control system described in Patent Document 1 comprises: a catalyst, located in the exhaust passage of an internal combustion engine, for purifying exhaust gas; a reactant supply mechanism, which supplies the reactants required for the catalyst reaction upstream of the catalyst; and a control device for controlling the amount of reactant supplied by the reactant supply mechanism. Furthermore, the control device performs a process of calculating a base reactant supply amount based on the operating conditions of the internal combustion engine; a process of calculating a correction amount such that the correction amount decreases with increasing engine speed; and a process of calculating a target reactant supply amount based on the base reactant supply amount and the correction amount. Furthermore, the control device calculates the correction amount such that the correction amount increases with increasing accelerator opening.

[0004] Patent Document 2 also describes the following catalyst efficiency improvement method. Specifically, the catalyst efficiency improvement method described in Patent Document 1 is a method for improving the efficiency of a NOx reduction catalyst connected downstream of an internal combustion engine. The method includes the steps of detecting impending acceleration of the internal combustion engine and adjusting the amount of reducing agent injected into the NOx reduction catalyst to offset fluctuations in the amount of NOx supplied to the engine due to engine acceleration. This catalyst efficiency improvement method continuously monitors parameters that can quickly indicate the transient state of the internal combustion engine, such as the rate of change of pedal position, the rate of change of fuel injection amount, and the rate of change of engine speed or load. Using a function using these parameters, the reducing agent injection amount is continuously adjusted to account for increases or decreases in the amount of NOx entering the catalyst.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-214494

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2004-156615 Summary of the Invention

[0009] Problems that the invention will solve

[0010] In the exhaust gas purification control system described in Patent Document 1, the correction amount is calculated such that, on the one hand, the greater the increase in accelerator opening, the greater the correction amount, and, on the other hand, the greater the increase in engine speed, the smaller the correction amount. Therefore, for example, if the increase in accelerator opening and the increase in engine speed are both large, there is a problem that adjusting the correction amount may become complicated.

[0011] Furthermore, the catalyst efficiency improvement method described in Patent Document 2 does not describe how to use a plurality of parameters that quickly indicate the transient state of the internal combustion engine as a function for adjusting the injection amount of the reducing agent.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device, a control method, and an exhaust gas purification system that can solve the above problems and correct the injection amount of the reducing agent with a simple configuration.

[0013] Means for solving problems

[0014] In order to solve the above-mentioned problems, one embodiment of the present invention is a control device for controlling the injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, wherein the control device comprises: a pre-correction injection amount calculation unit, which calculates the pre-correction injection amount of the reducing agent based on the operating state of the internal combustion engine; and an injection amount correction unit, which calculates a corrected injection amount after the pre-correction injection amount based on the time change rate of the rotational speed of the internal combustion engine and the time change rate of the fuel injection amount of the internal combustion engine, in such a manner that the injection amount of the reducing agent increases when at least the time change rate of the rotational speed and the time change rate of the fuel injection amount are positive, and decreases when at least the time change rate of the rotational speed and the time change rate of the fuel injection amount are negative.

[0015] In addition, one embodiment of the present invention is a control method for controlling the injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, the control method comprising the following steps: calculating a pre-corrected injection amount of the reducing agent based on the operating state of the internal combustion engine; and calculating a corrected post-injection amount that corrects the pre-corrected injection amount based on the time rate of change of the rotational speed of the internal combustion engine and the time rate of change of the fuel injection amount of the internal combustion engine in such a manner that the injection amount of the reducing agent increases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are positive, and decreases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are negative.

[0016] In addition, one embodiment of the present invention is an exhaust purification system comprising: a selective reduction catalyst, which is arranged in the exhaust passage of an internal combustion engine; an injection device, which injects a reducing agent supplied to the selective reduction catalyst; and a control device, which controls the injection amount of the reducing agent injected by the injection device, the control device comprising: a pre-corrected injection amount calculation unit that calculates the pre-corrected injection amount of the reducing agent based on the operating state of the internal combustion engine; and an injection amount correction unit that calculates a corrected post-injection amount that corrects the pre-corrected injection amount in a manner that increases the injection amount of the reducing agent at least when the time change rate of the speed and the time change rate of the fuel injection amount are both positive, and decreases the injection amount of the reducing agent at least when the time change rate of the speed and the time change rate of the fuel injection amount are both negative.

[0017] Effects of the Invention

[0018] According to each aspect of the present invention, the injection amount of the reducing agent can be corrected with a simple configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a system diagram showing a configuration example of an exhaust gas purification system according to an embodiment of the present invention.

[0020] Figure 2 Yes Figure 1 1 is a block diagram of a configuration example of the control device 100 shown.

[0021] Figure 3 Yes Figure 2 1 is a block diagram of a configuration example of the urea water injection amount correction unit 104.

[0022] Figure 4 Is used to illustrate Figure 3 FIG. 2 is a schematic diagram showing an example of the configuration of the urea water injection amount correction coefficient calculation unit 105 .

[0023] Figure 5 Yes Figure 3 1 is a block diagram showing an example configuration of the correction amount adjustment unit 107.

[0024] Figure 6 Yes Figure 5 Flowchart showing an example of the operation of the correction amount adjustment unit 107.

[0025] Figure 7 Yes Figure 1 Flowchart showing an example of the operation of the exhaust gas purification system 10.

[0026] Figure 8 Yes Figure 1Schematic diagram of an operation example of the exhaust gas purification system 10 shown. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Figure 1 It is a system diagram showing a configuration example of an exhaust gas purification system according to an embodiment of the present invention. Figure 2 Yes Figure 1 1 is a block diagram of a configuration example of the control device 100 shown. Figure 3 Yes Figure 2 1 is a block diagram of a configuration example of the urea water injection amount correction unit 104. Figure 4 Is used to illustrate Figure 3 FIG. 2 is a schematic diagram showing an example of the configuration of the urea water injection amount correction coefficient calculation unit 105 . Figure 5 Yes Figure 3 1 is a block diagram showing an example configuration of the correction amount adjustment unit 107. Figure 6 Yes Figure 5 Flowchart showing an example of the operation of the correction amount adjustment unit 107. Figure 7 Yes Figure 1 Flowchart showing an example of the operation of the exhaust gas purification system 10. Figure 8 Yes Figure 1 Schematic diagram of an operation example of the exhaust gas purification system 10 shown.

[0028] (Configuration Example of Exhaust Gas Purification System 10)

[0029] Figure 1 An example configuration of the exhaust gas purification system 10 according to the embodiment of the present invention is shown. Figure 1 The exhaust gas purification system 10 shown includes an engine 1, an exhaust passage 3, a DPF device 5, an SCR device 6, a urea water injector 7, an engine outlet NOx (nitrogen oxide) sensor 91, an SCR outlet NOx sensor 92, an SCR base temperature sensor 93, and a control device 100. In addition, the exhaust gas purification system 10 of this embodiment includes at least the SCR device 6, the urea water injector 7, and the control device 100. In addition, Figure 1 In the exhaust gas purification system 10 or the control device 100 of the present embodiment, the configuration for controlling the injection amount of the urea water injector 7 is mainly shown, and configurations for other functions such as fuel injection control of the engine 1 are appropriately omitted from the illustration.

[0030] The engine 1 is an example of an internal combustion engine, and in this embodiment, is a multi-cylinder diesel engine. An exhaust passage 3 discharges exhaust gas from the engine 1 into the atmosphere through a DPF device 5 and an SCR device 6 .

[0031] The DPF device 5 is, for example, a continuously regenerative DPF system, internally comprising a DOC (Diesel Oxidation Catalyst) 51 and a DPF (Diesel Particulate Filter) 52. The DPF 52 captures particulate matter (PM). The nitrogen dioxide converted by the DOC 51 oxidizes the PM captured downstream to form carbon dioxide, thereby removing the PM. However, the DPF device 5 may also be an automatically regenerative DPF system, a manually regenerative DPF system, or other systems.

[0032] The SCR device 6 includes an SCR (Selective Catalytic Reduction) catalyst 61. It converts nitrogen oxides (NOx) into nitrogen molecules (N2) and water (H2O) using urea water, an example of a reducing agent, supplied to the upstream side of the SCR 61 via a urea water injector 7. Alternatively, the reducing agent may be anhydrous urea.

[0033] The urea water injector 7 is an injector that injects urea water to be supplied to the SCR 61 in the SCR device 6 . The injection amount of the urea water injected into the exhaust passage 3 by the urea water injector 7 is controlled by the control device 100 .

[0034] The engine outlet NOx sensor 91 senses the NOx concentration near the exhaust outlet of the engine 1 in the exhaust passage 3 and outputs a signal indicating the sensing result to the control device 100. The SCR outlet NOx sensor 92 senses the NOx concentration near the exhaust outlet of the SCR device 6 in the exhaust passage 3 and outputs a signal indicating the sensing result to the control device 100. The engine outlet NOx sensor 91 and the engine outlet NOx sensor 92 are used, for example, to calculate the NOx reduction effect of the SCR 61 by comparing their respective measured values. The SCR base temperature sensor 93 measures the catalyst bed temperature of the SCR 61 of the SCR device 6 and outputs the measurement result to the control device 100. Alternatively, the SCR base temperature sensor 93 may be composed of multiple temperature sensors. In this case, for example, the average of the multiple measured values ​​may be used as the catalyst bed temperature.

[0035] The control device 100 repeatedly inputs analog or digital sensor signals output from multiple sensors, including an engine outlet NOx sensor 91, an SCR outlet NOx sensor 92, an SCR base temperature sensor 93, an unillustrated engine rotation sensor that senses the rotation speed (rotational speed) of the engine 1, and a pedal operation amount sensor that senses the operation amount of the accelerator pedal that is not shown, at a prescribed period, and uses multiple injectors of the engine 1 to control fuel injection, control various motors and valves, or control the injection amount of the urea water injector 7.

[0036] (Control device 100)

[0037] Figure 1 The engine control device 100 shown can be constructed using a computer such as a microcomputer and peripheral circuits and peripheral devices of the computer, and has a functional structure composed of a combination of hardware such as the computer and software such as a program executed by the computer. Figure 2 In addition, Figure 2 Among the plurality of functional configurations included in the control device 100 , a functional configuration related to injection amount control of the urea water injector 7 is shown. Figure 2 The control device 100 shown includes a fuel injection control unit 101 and a urea water injection amount control unit 102 . The urea water injection amount control unit 102 also includes a pre-correction urea water injection amount calculation unit 103 and a urea water injection amount correction unit 104 .

[0038] The fuel injection control unit 101 controls fuel injection by, for example, controlling a fuel injection device (not shown) of the engine 1 , and outputs information indicating the engine 1 speed, fuel injection amount, and the like to the urea water injection amount control unit 102 .

[0039] The urea water injection amount control unit 102 corrects and adjusts the pre-correction urea water injection amount D11 ( Figure 3 ), the urea water injection amount final value D16 ( Figure 3 ) is used as the target value to control the injection amount of urea water by the urea water injector 7.

[0040] The pre-correction urea water injection amount calculation unit 103 calculates the pre-correction urea water injection amount D11, which serves as a reference value for the target urea water injection amount, based on the operating state of the engine 1, for example, the predicted NOx emission amount. In this embodiment, information indicating the operating state of the engine 1 is information representing multiple parameters used to calculate (estimate) the amount of NOx contained in the exhaust gas of the engine 1, such as the engine 1 speed, cooling water temperature, intake air temperature, catalyst bed temperature of the SCR 61 of the SCR device 6, fuel injection amount, fuel injection period, sensing results from the engine outlet NOx sensor 91, and sensing results from the SCR outlet NOx sensor 92. Furthermore, in this embodiment, the information indicating the operating state of the engine 1 includes at least sensing information from the engine outlet NOx sensor 91 (or the SCR outlet NOx sensor 92), which senses the NOx concentration in the exhaust passage 3. However, the pre-correction urea water injection amount calculation unit 103 may also calculate (estimate) the amount of NOx contained in the exhaust gas of the engine 1 without using the sensing results from the engine outlet NOx sensor 91 or the SCR outlet NOx sensor 92.

[0041] The urea water injection amount corrector (injection amount corrector) 104 corrects the pre-correction injection amount calculated by the pre-correction urea water injection amount calculator 103 based on the time-dependent rate of change (time-dependent value, also referred to as "rate of change") of the engine 1's rotational speed and the time-dependent rate of change of the fuel injection amount of the engine 1 to calculate a corrected injection amount. The urea water injection amount corrector 104 corrects the pre-correction injection amount and calculates the corrected injection amount in such a way that the urea water injection amount increases when at least the time-dependent rate of change of the rotational speed and the time-dependent rate of change of the fuel injection amount are positive, and decreases when at least the time-dependent rate of change of the rotational speed and the time-dependent rate of change of the fuel injection amount are negative. Furthermore, the urea water injection amount corrector 104 may adjust the corrected injection amount so that the cumulative value of the difference between the pre-correction injection amount and the post-correction injection amount becomes zero. Furthermore, when reducing the urea water injection amount, the urea water injection amount corrector 104 may adjust the corrected injection amount so that it is equal to or greater than a predetermined lower limit.

[0042] Figure 3 Show Figure 2 The configuration example of the urea water injection amount correction unit 104 is shown. Figure 3The illustrated urea water injection amount correction unit 104 includes a urea water injection amount correction coefficient calculation unit 105, a multiplier 106, and a correction amount adjustment unit 107. The unit receives as input a pre-correction urea water injection amount D11, an engine speed change rate D12, and a fuel injection amount change rate D13. The unit corrects the pre-correction urea water injection amount D11 to calculate a post-correction urea water injection amount D15. The unit then adjusts the post-correction urea water injection amount D15 and outputs it as a final urea water injection amount value D16. Furthermore, the unit adjusts the post-correction urea water injection amount D15 so that the final urea water injection amount value D16 is equal to either the pre-correction urea water injection amount D11, the post-correction urea water injection amount D15, or a predetermined lower limit value (0.3 ml / s in the following example). The unit then calculates the final urea water injection amount value D16.

[0043] The urea water injection amount correction coefficient calculation unit 105 uses, for example, Figure 4 The urea water injection amount correction coefficient D14 is calculated using the table (or map) 1051. The multiplier 106 multiplies the pre-correction urea water injection amount D11 by the urea water injection correction coefficient D14 to calculate the post-correction urea water injection amount D15. Figure 4 Table 1051, shown, uses the fuel injection amount change rate (mg / stroke / s) and the engine speed change rate (rpm / s) as parameters to define the values ​​of the urea solution injection correction coefficient D14 corresponding to each combination of the fuel injection amount change rate and the engine speed change rate. A positive value for the fuel injection amount change rate indicates an increase in the fuel injection amount change rate, while a negative value indicates a decrease in the fuel injection amount change rate. A positive value for the engine speed change rate indicates an increase in the engine speed, while a negative value indicates a decrease in the engine speed.

[0044] The urea water injection amount correction coefficient calculation unit 105 uses Figure 4Table 1051 shows that, for example, when the fuel injection amount change rate is 200 [mg / stroke / s] and the engine speed change rate is 200 [rpm / s], the urea water injection correction amount coefficient D14 is calculated to be "2.0." Furthermore, the urea water injection correction amount coefficient calculation unit 105 calculates the urea water injection correction amount coefficient D14 to be "0.5" when the fuel injection amount change rate is -200 [mg / stroke / s] and the engine speed change rate is -200 [rpm / s]. When the urea water injection correction amount coefficient D14 is "1," the pre-correction urea water injection amount D11 and the post-correction urea water injection amount D15 are the same. When the coefficient D14 is greater than "1," the post-correction urea water injection amount D15 is greater than the pre-correction urea water injection amount D11 (increasing correction). When the coefficient D14 is less than "1," the post-correction urea water injection amount D15 is less than the pre-correction urea water injection amount D11 (increasing correction).

[0045] Table 1051 shows the following trend. Specifically, an increase in the fuel injection amount indicates an increase in load, predicting an increase in NOx flowing into the SCR 61. Conversely, a decrease in the fuel injection amount predicts a decrease in NOx. Furthermore, no correction is performed if the fuel injection amount remains unchanged. As the engine speed increases, the absolute amount of NOx increases. It can be inferred that as the engine speed decreases, the absolute amount of NOx decreases.

[0046] The correspondence between the combination of the fuel injection amount change rate and the engine speed change rate and the urea water injection correction amount coefficient D14 can be set based on actual machine experimental results or simulation results using a model.

[0047] In addition, when using Figure 4 In the case of the table 1051 shown in FIG. 1 , the urea water correction coefficient D14 is calculated as follows: when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both positive compared to the urea water injection amount before correction D11, the urea water injection amount after correction D15 is increased, and when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both negative, the urea water injection amount after correction D15 is decreased. Figure 4 In the case of the table 1051 shown, the urea water correction coefficient D14 is calculated as follows: when compared with the urea water injection amount before correction D11, the urea water injection amount after correction D15 is increased when the time change rate of the fuel injection amount is positive, and the urea water injection amount after correction D15 is reduced when the time change rate of the fuel injection amount is negative.

[0048] Alternatively, the multiplier 106 may interpolate the value of the urea water correction coefficient D14 based on each change rate and calculate the corrected urea water injection amount D15.

[0049] Next, Figure 3 The correction amount adjustment unit 107 shown in FIG. 1 is described below. The correction amount adjustment unit 107 is, for example, Figure 5 As shown, the system includes a temperature correction value calculation unit 1071 , an adder 1072 , a total correction amount calculation unit 1073 , and a urea water injection amount final value determination unit 1074 . Figure 5 The correction amount adjustment unit 107 shown in FIG. 1 receives the corrected urea water injection amount D15, the pre-corrected urea water injection amount D11, the SCR base temperature D17, and the urea water injection amount correction coefficient D14, calculates and outputs the final urea water injection amount value D16. Figure 5 In the example shown, the correction amount adjustment unit 107 and Figure 3 The correction amount adjustment unit 107 shown in FIG. 1 is different in that the SCR base temperature D17 is newly input.

[0050] Temperature correction value calculation unit 1071 calculates a correction value (referred to as SCR base temperature correction value D18) for calculating the cumulative value of the amount of ammonia adsorbed by SCR 61 based on SCR base temperature D17 and the saturation adsorption amount curve of SCR 61. The saturation adsorption amount curve is a curve showing the maximum amount of ammonia adsorbed by SCR 61 at various temperatures (e.g., Japanese Patent Application Laid-Open No. 2010-261388). SCR base temperature correction value D18 is a correction value used to prevent the cumulative value of the amount of ammonia adsorbed from exceeding the saturation adsorption amount. It is based on a certain temperature and can take a value such as zero, a positive value, or a negative value.

[0051] The adder 1072 calculates (urea water injection amount final value D16 )−(urea water injection amount before correction D11 )+(SCR base temperature correction value D18 ) and outputs the calculated result to the total correction amount calculation unit 1073 .

[0052] Total correction amount calculation unit 1073 integrates {(urea water injection amount final value D16) - (urea water injection amount before correction D11) + (SCR base temperature correction value D18)} to calculate a total correction amount S. Total correction amount S is the cumulative value obtained by adding a correction based on SCR base temperature correction value D18 to the difference between the final urea water injection amount D16 and the pre-correction urea water injection amount D11. This value corresponds to the amount of ammonia gas accumulated in SCR 61, estimated based on the difference from the corrected injection amount based on the pre-correction urea water injection amount D11. Total correction amount calculation unit 1073 limits the value of total correction amount S so that it is greater than zero.

[0053] Furthermore, the total correction amount calculation unit 1073 integrates the amount of urea-water injection increased by the correction from the base urea-water injection amount as a positive value. In this case, the post-correction urea-water injection amount D15 minus the pre-correction urea injection amount D11 takes a positive or negative value. Furthermore, when the injection amount is limited to, for example, 0.3 ml / s or more during reduction, the total correction amount S decreases from the base urea-water injection amount due to the decrease.

[0054] Alternatively, the total correction amount calculation unit 1073 may use the SCR base temperature correction value D18 as the upper limit of the total correction amount S. In this case, the temperature correction value calculation unit 1071 calculates and outputs the upper limit of the cumulative value of the ammonia adsorption amount of SCR 61 as the SCR base temperature correction value (upper limit) D18 based on the SCR base temperature D17 and the saturation adsorption amount curve of SCR 61. The SCR base temperature correction value D18 output by the temperature correction value calculation unit 1071 is not input to the adder 1072 but is input to the total correction amount calculation unit 1073. Furthermore, the adder 1072 calculates (urea water injection amount final value D16) minus (urea water injection amount before correction D11) and outputs the calculated result to the total correction amount calculation unit 1073. Then, the total correction amount calculation unit 1073 uses the SCR base temperature correction value D18 as the upper limit value, integrates {(urea water injection amount final value D16)-(urea water injection amount before correction D11)}, and calculates the total correction amount S (where S>0).

[0055] The urea water injection amount final value determination unit 1074 receives as input the corrected urea water injection amount D15, the pre-correction urea water injection amount D11, the total correction amount S, and the urea water injection amount correction coefficient D14. The unit adjusts the corrected urea water injection amount D15 (instead of using the corrected urea water injection amount D15 as the final urea water injection amount D16 directly, the corrected urea water injection amount D15 is set to a different value depending on the conditions) so that the total injection amount does not change relative to the reference urea water injection amount (the pre-correction urea water injection amount D11) due to the correction and the injection amount does not fall below a predetermined lower limit due to the correction in the decreasing direction. The unit then calculates and outputs the final urea water injection amount D16.

[0056] For example, when the SCR base temperature correction value D18 is within a predetermined range, the urea water injection amount final value determination unit 1074 can adjust the corrected urea water injection amount D15 so that the cumulative difference between the pre-correction urea water injection amount D11 (pre-correction injection amount) and the post-correction urea water injection amount D15 (post-correction injection amount) becomes zero, thereby calculating the urea water injection amount final value D16. Alternatively, when the urea water injection amount is reduced, the urea water injection amount correction unit 1074 can adjust the corrected urea water injection amount D15 so that it becomes equal to or greater than a predetermined lower limit, thereby calculating the urea water injection amount final value D16.

[0057] The urea water injection amount final value determination unit 1074 calculates the urea water injection amount final value D16, for example, in the following cases (1) to (3). (1) When the urea water injection amount correction coefficient D14 (correction coefficient) is greater than 1, the urea water injection amount final value D16 (final value) is set to the corrected urea water injection amount D15. (2) When the urea water injection amount correction coefficient D14 is less than or equal to 1 and the total correction amount S is greater than 0, the urea water injection amount final value D16 is set to the corrected urea water injection amount D15 (the minimum value is set to a predetermined lower limit value (e.g., 0.3 ml / s)). Furthermore, (3) When the urea water injection amount correction coefficient D14 is less than or equal to 1 and the total correction amount S is equal to 0, the urea water injection amount final value D16 is set to the pre-corrected urea water injection amount D11.

[0058] Figure 6 FIG. 2 shows an example of the operation of the urea water injection amount final value determination unit 1074. Figure 6 In the illustrated operation example, the urea water injection amount final value determination unit 1074 first temporarily sets the urea water injection amount final value D16 to the corrected urea water injection amount D15 (step S101). Next, the urea water injection amount final value determination unit 1074 determines whether the urea water injection amount correction coefficient D14 is less than 1 (step S102). If the urea water injection amount correction coefficient D14 is greater than 1 (if "N" in step S102), the urea water injection amount final value determination unit 1074 ends the operation. Figure 6 In this case, the urea water injection amount final value D16 becomes the corrected urea water injection amount D15.

[0059] On the other hand, when the urea water injection amount correction coefficient D14 is less than 1 ("Y" in step S102), the urea water injection amount final value determination unit 1074 determines whether the urea water injection amount D11 before correction exceeds the lower limit value (0.3 ml / s) (step S103). If the urea water injection amount D11 before correction does not exceed the lower limit value (0.3 ml / s) ("N" in step S103), the urea water injection amount final value determination unit 1074 sets the urea water injection amount final value D16 to the urea water injection amount D11 before correction (step S106), and ends. Figure 6 In this case, the urea water injection amount final value D16 becomes the urea water injection amount before correction D11.

[0060] On the other hand, if the urea water injection amount D11 before correction exceeds the lower limit value (0.3 ml / s) (if "Y" in step S103), the urea water injection amount final value determination unit 1074 determines whether the total correction amount S is greater than 0 (step S104). If the total correction amount S is greater than 0 (if "Y" in step S104), the urea water injection amount final value determination unit 1074 limits the urea water injection amount final value D16 to 0.3 ml / s with the total correction amount S = 0 as the limit (step S105), and ends. Figure 6 In this case, the urea water injection amount final value D16 becomes the corrected urea water injection amount D15 or 0.3 ml / s within the range of the total correction amount S>0.

[0061] On the other hand, when the total correction amount S=0 ("N" in step S104), the urea water injection amount final value determination unit 1074 sets the urea water injection amount final value D16 to the urea water injection amount before correction D11 (step S106), and ends. Figure 6 In this case, the urea water injection amount final value D16 becomes the urea water injection amount before correction D11.

[0062] As described above, the control device 100 of the present embodiment is a control device for controlling the injection amount of urea water (reducing agent) supplied to the SCR 61 (selective reduction catalyst) provided in the exhaust passage 3 of the engine 1 (internal combustion engine). The control device 100 includes: a pre-correction injection amount calculation unit 103 for calculating a pre-correction urea water injection amount D11 (pre-correction injection amount) of the urea water based on the operating state of the engine 1; and a urea water injection amount correction unit 104 (injection amount correction unit) for calculating a post-correction urea water injection amount D15 by correcting the pre-correction urea water injection amount D11 based on the time rate of change of the engine speed of the engine 1 (engine speed change rate D12) and the time rate of change of the fuel injection amount of the engine 1 (fuel injection amount change rate D13) so that the injection amount of the urea water is increased when at least both the engine speed change rate D12 and the fuel injection amount change rate D13 are positive, and the injection amount of the urea water is reduced when at least both the engine speed change rate D12 and the fuel injection amount change rate D13 are negative. According to the present embodiment, with a simple configuration, even when the increase in the fuel injection amount is large and the increase in the engine speed is large, the injection amount of the urea solution can be corrected.

[0063] Furthermore, the urea water injection amount correction unit 104 (injection amount correction unit) can further adjust the corrected urea water injection amount D15 so that the cumulative difference between the pre-correction urea water injection amount D11 and the post-correction urea water injection amount D15 reaches zero. This configuration allows the pre-correction and post-correction urea water injection amounts to be the same. Furthermore, according to this embodiment, even when the total injection amount for a predetermined period of time is optimized for the system, the pre-correction urea water injection amount D11 can be maintained at the optimized post-correction injection amount.

[0064] Furthermore, the urea water injection amount correction unit 104 (injection amount correction unit) can also adjust the corrected urea water injection amount D15 so as to be equal to or greater than a predetermined lower limit value when reducing the injection amount of urea water.

[0065] (Operation Example of Exhaust Gas Purification System 10)

[0066] Next, refer to Figure 7 , an operation example of the exhaust gas purification system 10 will be described. Figure 7 The actions shown are repeated at a specified cycle. Figure 7 In the illustrated operation, the control device 100 (e.g., the urea solution injection amount control unit 102) first obtains the engine speed and fuel injection amount (e.g., from the combustion injection amount control unit 101) (step S201). Next, the control device 100 (e.g., the urea solution injection amount control unit 102) calculates the rate of change of the engine speed and the rate of change of the fuel injection amount (step S202). Here, the engine 1 speed and fuel injection amount change (step S203).

[0067] Next, the pre-correction urea-water injection amount calculation unit 103 predicts the NOx emission amount and calculates the pre-correction urea-water injection amount D11 (step S204). In step S204, if the rate of change in the fuel injection amount is negative (NOx reduction), the urea-water injection amount correction unit 104 corrects the injection amount (step S205), and then reduces the urea-water injection amount (step S206). The engine outlet NOx sensor 91 then detects the decrease in NOx (step S207), resulting in a decrease in the pre-correction urea-water injection amount D11 (step S208).

[0068] On the other hand, in step S204, if the rate of change in the fuel injection amount is positive (NOx is increasing), the urea water injection amount correction unit 104 corrects the injection amount (step S209), and the urea water injection amount is increased (step S210). Then, the engine outlet NOx sensor 91 detects the increase in NOx (step S211), and the pre-correction urea water injection amount D11 is increased (step S212).

[0069] Figure 8 An example of controlling the urea water injection amount according to this embodiment is shown. From top to bottom, the temporal changes in the rate of change of the fuel injection amount and the rate of change of the engine speed, the temporal changes in the measurement results of the engine outlet NOx sensor 91 and the urea water injection amount (before correction), and the temporal changes in the measurement results of the engine outlet NOx sensor 91 and the urea water injection amount (after correction) are shown. The increase C1 in the urea water injection amount (after correction) and the rate of change of the fuel injection amount increases by the area A1 indicated by hatched lines. Subsequently, when the urea water injection amount (before correction) exceeds the lower limit of 0.3 ml / s, the urea water injection amount (after correction) decreases to the lower limit of 0.3 ml / s by the area A2. This area A2 is equal to the area A1. In this case, the urea water injection amount is suppressed from the maximum value to the lower limit of 0.3 ml / s. This shortens the time it takes for the urea water injection amount to reach its maximum value, thereby reducing the risk of urea precipitates accumulating within the exhaust passage.

[0070] On the other hand, since the fuel injection amount (before correction) is lower than the lower limit value 0.3 ml / s relative to the decrease C2 of the fuel injection amount change rate, the urea water injection amount (after correction) does not change from the fuel injection amount (before correction).

[0071] On the other hand, the urea water injection amount (after correction) increases by the area A3 with respect to the increase C3 of the rate of change of the fuel injection amount.

[0072] As described above, according to this embodiment, for example, (1) by calculating the change in NOx based on the rate of change in engine speed and the rate of change in fuel injection amount, the urea injection amount can be changed before the NOx sensor installed at the engine outlet senses the change in NOx in the exhaust gas. This can compensate for the delay time until the NOx sensor senses the change in the NOx amount in the exhaust gas, thereby increasing the degree of freedom in the installation location of the NOx sensor.

[0073] Furthermore, even when the urea injection amount is changed, the control device increases the urea injection amount by sensing a change in NOx in the exhaust gas through the NOx sensor. In this case, by subtracting the urea water injection amount increased in (1) above, the urea amount per exhaust gas unit can be reduced, thereby reducing the risk of urea precipitates accumulating inside the exhaust pipe.

[0074] The embodiments of the present invention have been described above with reference to the accompanying drawings, but the specific configuration is not limited to the above embodiments and includes design changes that do not depart from the scope of the present invention. Figure 3 In the embodiment, the correction amount adjustment unit 107 is omitted, and the corrected urea water injection amount D15 is used as the urea water injection amount final value D16, or in the embodiment Figure 5 In the embodiment, the temperature correction value calculation unit 1071 is omitted, or the total correction amount calculation unit 1073 is omitted and the division based on the total correction amount S in the urea water injection amount final value determination unit 1074 is omitted.

[0075] Furthermore, in the above-described embodiments, part or all of the program executed by the computer can be distributed via a computer-readable recording medium or a communication line.

[0076] Industrial applicability

[0077] According to each aspect of the present invention, the injection amount of the reducing agent can be corrected with a simple configuration.

[0078] Description of Reference Numerals

[0079] 1…Engine (internal combustion engine), 3…Exhaust passage, 5…DPF device, 51…DOC, 52…DPF, 6…SCR device, 61…SCR, 7…Urea water injector (injection device), 10…Exhaust gas purification system, 91…Engine outlet NOx sensor, 92…SCR outlet NOx sensor, 93…SCR base temperature sensor, 100…Control device, 101…Fuel injection control unit, 102…Urea water injection amount control unit, 103…Pre-correction urea water injection amount calculation unit, 104…Urea water injection amount correction unit.

Claims

1. A control device for controlling the injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, characterized in that: The control device comprises: a pre-correction injection amount calculation section that calculates a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; and An injection amount correction unit calculates a corrected injection amount after the pre-correction injection amount based on the time rate of change of the rotational speed of the internal combustion engine and the time rate of change of the fuel injection amount of the internal combustion engine, so that the injection amount of the reducing agent is increased at least when the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both positive, and the injection amount of the reducing agent is reduced at least when the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both negative.

2. The control device according to claim 1, characterized in that The injection amount correction unit further adjusts the post-correction injection amount so that an integrated value of a difference between the pre-correction injection amount and the post-correction injection amount becomes zero.

3. The control device according to claim 1 or 2, characterized in that: The injection amount correction unit further adjusts the corrected injection amount so as to be equal to or greater than a predetermined lower limit value when reducing the injection amount of the reducing agent.

4. The control device according to any one of claims 1 to 3, characterized in that: The information indicating the operating state includes at least sensing information of a sensor that senses the concentration of nitrogen oxides in the exhaust passage.

5. A control method for controlling the injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, characterized in that: The control method comprises the following steps: calculating a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; and Based on the time rate of change of the rotational speed of the internal combustion engine and the time rate of change of the fuel injection amount of the internal combustion engine, a corrected injection amount after the pre-correction injection amount is calculated in such a way that the injection amount of the reducing agent increases at least when the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both positive, and the injection amount of the reducing agent decreases at least when the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are both negative.

6. An exhaust purification system, characterized in that: have: A selective reduction catalyst is provided in an exhaust passage of an internal combustion engine; an injection device that injects the reducing agent to be supplied to the selective reducing catalyst; and a control device for controlling the injection amount of the reducing agent injected by the injection device, The control device includes: a pre-corrected injection amount calculation unit for calculating the pre-corrected injection amount of the reducing agent based on the operating state of the internal combustion engine; and an injection amount correction unit for calculating, based on the time rate of change of the rotational speed of the internal combustion engine and the time rate of change of the fuel injection amount of the internal combustion engine, a corrected post-injection amount that corrects the pre-corrected injection amount in a manner such that the injection amount of the reducing agent increases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are positive, and the injection amount of the reducing agent decreases when at least the time rate of change of the rotational speed and the time rate of change of the fuel injection amount are negative.

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