Control device, control method, and exhaust purification system

Abstract

To correct injection amount of a reducing agent by using a simple configuration.SOLUTION: In one embodiment of the present invention, a control device controls injection amount of a reducing agent to be supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine. The control device includes: a pre-correction injection amount calculation section for calculating pre-correction injection amount of the reducing agent on the basis of an operating state of the internal combustion engine; and an injection amount correction section for calculating post-correction injection amount obtained by correcting the pre-correction injection amount so that on the basis of a time change rate of speed of the internal combustion engine and a time change rate of the fuel injection amount of the internal combustion engine, the injection amount of the reducing agent is increased at least when both of the time change rate of the speed and the time change rate of the fuel injection amount are positive and the injection amount of the reducing agent is reduced at least when both of the time change rate of the speed and the time change rate of the fuel injection amount are negative.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 describes the following exhaust purification control system. That is, the exhaust purification control system described in Patent Document 1 includes a catalyst that is provided in an exhaust passage of an internal combustion engine to purify exhaust gas, a reactant supply means that supplies a reactant required for the reaction of the catalyst upstream of the catalyst, and a control device that controls the amount of reactant supplied by the reactant supply means. The control device executes the steps of: calculating a basic reactant supply amount from the operating conditions of the internal combustion engine; calculating a correction amount such that the correction amount becomes smaller as the increase in engine speed increases; and calculating a target reactant supply amount from the basic reactant supply amount and the correction amount. The control device also calculates the correction amount such that the correction amount becomes larger as the increase in accelerator opening increases.

[0003] Also, Patent Document 2 describes the following method for improving catalyst efficiency. That is, the method for improving catalyst efficiency described in Patent Document 1 is a method for improving the efficiency of a NOx reduction catalyst connected downstream of an internal combustion engine, and includes a step of detecting an impending acceleration of the internal combustion engine, and a step of adjusting the amount of reducing agent injected into the NOx reduction catalyst to offset fluctuations in the amount of NOx supplied to the internal combustion engine caused by the acceleration of the internal combustion engine. In this method for improving catalyst efficiency, parameters that can quickly indicate engine transient states, 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, are continuously monitored, and the amount of reducing agent injected is continuously adjusted by using a function having these parameters, taking into account increases and decreases in the amount of NOx entering the catalyst. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-214494 A [Patent Document 2] JP 2004-156615 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the exhaust purification control system described in Patent Document 1, the correction amount is calculated so that the larger the increase in the accelerator opening, the larger the correction amount, and the larger the increase in the engine speed, the smaller the correction amount. Therefore, for example, when the increase in the accelerator opening and the increase in the engine speed are large, there is a problem that adjustment of the correction amount may become complicated.

[0006] Furthermore, the method for improving catalyst efficiency described in Patent Document 2 does not show how multiple parameters that quickly indicate engine transient states are used in a function for adjusting the amount of injection of reducing agent.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a control device, a control method, and an exhaust purification system that can solve the above-mentioned problems and correct the amount of reducing agent injected with a simple configuration. [Means for solving the problem]

[0008] In order to solve the above problems, one aspect of the present invention is a control device that controls an injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, the control device including: a pre-correction injection amount calculation unit 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 that calculates a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, such that the injection amount of the reducing agent increases when at least both the time rate of change of the rotation 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 both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative.

[0009] Moreover, one aspect of the present invention is a control method for controlling an 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 including the steps of: calculating a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; and calculating a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, such that the injection amount of the reducing agent increases when at least both the time rate of change of the rotation 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 both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative.

[0010] Moreover, one aspect of the present invention is an exhaust purification system including a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, an injection device that injects a reducing agent supplied to the selective reduction catalyst, and a control device that controls the injection amount of the reducing agent by the injection device, wherein the control device includes: a pre-correction injection amount calculation unit 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 that calculates a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, so that the injection amount of the reducing agent increases when at least both the time rate of change of the rotation 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 both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative. Effect of the Invention

[0011] 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]

[0012] [Figure 1] 1 is a system diagram showing a configuration example of an exhaust gas purification system according to an embodiment of the present invention. [Diagram 2]2 is a block diagram showing an example of the configuration of a control device 100 shown in FIG. [Diagram 3] 3 is a block diagram showing an example of the configuration of a urea water injection amount correction unit 104 shown in FIG. 2. [Figure 4] FIG. 4 is a schematic diagram for explaining a configuration example of a urea water injection amount correction coefficient calculation unit 105 shown in FIG. 3. [Diagram 5] 4 is a block diagram showing an example of the configuration of a correction amount adjustment unit 107 shown in FIG. 3. [Figure 6] 6 is a flowchart showing an example of the operation of the correction amount adjustment unit 107 shown in FIG. 5. [Figure 7] 2 is a flowchart showing an example of the operation of the exhaust purification system 10 shown in FIG. [Figure 8] 2 is a schematic diagram showing an example of operation of the exhaust purification system 10 shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the same reference numerals are used for the same or corresponding configurations in each drawing, and the description is omitted as appropriate. FIG. 1 is a system diagram showing an example of the configuration of an exhaust purification system according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the control device 100 shown in FIG. 1. FIG. 3 is a block diagram showing an example of the configuration of the urea water injection amount correction unit 104 shown in FIG. 2. FIG. 4 is a schematic diagram for explaining an example of the configuration of the urea water injection amount correction coefficient calculation unit 105 shown in FIG. 3. FIG. 5 is a block diagram showing an example of the configuration of the correction amount adjustment unit 107 shown in FIG. 3. FIG. 6 is a flowchart showing an example of the operation of the correction amount adjustment unit 107 shown in FIG. 5. FIG. 7 is a flowchart showing an example of the operation of the exhaust purification system 10 shown in FIG. 1. FIG. 8 is a schematic diagram showing an example of the operation of the exhaust purification system 10 shown in FIG. 1.

[0014] (Example of configuration of exhaust purification system 10) FIG. 1 shows an example of the configuration of an exhaust purification system 10 according to an embodiment of the present invention. The exhaust purification system 10 shown in FIG. 1 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 bed temperature sensor 93, and a control device 100. Note that the exhaust purification system 10 according to this embodiment includes at least the SCR device 6, the urea water injector 7, and the control device 100, for example. Note that FIG. 1 mainly shows the configuration related to the injection amount control of the urea water injector 7 in the exhaust purification system 10 or the control device 100 of this embodiment, and the configuration related to other functions such as fuel injection control of the engine 1 is appropriately omitted.

[0015] 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 through a DPF device 5 and an SCR device 6 into the atmosphere.

[0016] The DPF device 5 is, for example, a continuous regeneration type DPF system, and includes a DOC (Diesel Oxidation Catalyst) 51 and a DPF (Diesel Particulate Filter) 52. The DPF 52 captures PM (Particulate Matter), and the nitrogen dioxide converted by the DOC 51 oxidizes the PM captured downstream to carbon dioxide, thereby removing the PM. However, the DPF device 5 may be another type of system, such as an automatic regeneration type DPF system or a manual regeneration type DPF system.

[0017] The SCR device 6 includes an SCR (Selective Catalytic Reduction) 61 therein, and converts nitrogen oxides (NOx) into nitrogen molecules (N2) and water (H2O) using urea water, which is an example of a reducing agent, supplied into the exhaust gas upstream of the SCR 61 by a urea water injector 7. The reducing agent may be anhydrous urea or the like.

[0018] The urea water injector 7 is an injection device that injects urea water to be supplied to the SCR 61 in the SCR device 6. The injection amount of urea water that the urea water injector 7 injects into the exhaust passage 3 is controlled by the control device 100.

[0019] The engine outlet NOx sensor 91 is a sensor that detects the concentration of NOx in the vicinity of the exhaust outlet of the engine 1 in the exhaust passage 3, and outputs a signal indicating the detection result to the control device 100. The SCR outlet NOx sensor 92 is a sensor that detects the concentration of NOx in the vicinity of the exhaust outlet of the SCR device 6 in the exhaust passage 3, and outputs a signal indicating the detection result to the control device 100. The engine outlet NOx sensor 91 and the engine outlet NOx sensor 92 are used, for example, when calculating the NOx reduction effect by the SCR 61 by comparing each measurement value. The SCR bed 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. Note that the SCR bed temperature sensor 93 may be composed of multiple temperature sensors, and in that case, for example, the average value of the multiple measurement values ​​can be set as the catalyst bed temperature.

[0020] The control device 100 repeatedly inputs analog or digital sensor signals at a predetermined period from multiple sensors including an engine outlet NOx sensor 91, an SCR outlet NOx sensor 92, an SCR bed temperature sensor 93, an engine rotation sensor (not shown) that detects the rotation speed (rotational speed) of the engine 1, a pedal operation amount sensor (not shown) that detects the operation amount of an accelerator pedal, etc., and performs fuel injection control using multiple injectors equipped in the engine 1, controls various motors and valves, and controls the injection amount of the urea water injector 7.

[0021] (Control device 100) The engine control device 100 shown in Fig. 1 can be configured using a computer such as a microcomputer and peripheral circuits and devices of the computer, and includes multiple blocks shown in Fig. 2 as a functional configuration formed by a combination of hardware such as the computer and software such as a program executed by the computer. Fig. 2 shows a functional configuration related to injection amount control of the urea water injector 7, among the multiple functional configurations included in the control device 100. The control device 100 shown in Fig. 2 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.

[0022] The fuel injection control unit 101 performs fuel injection control, for example, by controlling a fuel injection device (not shown) of the engine 1. The fuel injection control unit 101 outputs information indicating the rotation speed of the engine 1, the fuel injection amount, etc. to the urea water injection amount control unit 102.

[0023] The urea water injection amount control unit 102 corrects and adjusts the pre-correction urea water injection amount D11 (Figure 3) calculated by the pre-correction urea water injection amount calculation unit 103, thereby controlling the amount of urea water injected by the urea water injector 7, with the urea water injection amount final value D16 (Figure 3) output by the urea water injection amount correction unit 104 as a target value.

[0024] The pre-correction urea water injection amount calculation unit 103 predicts, for example, the amount of NOx emissions based on the operating state of the engine 1, and calculates a pre-correction urea water injection amount D11 which is a reference value for the target value of the injection amount of urea water. In this embodiment, the information representing the operating state of the engine 1 is information representing a plurality of parameters used when calculating (estimating) the amount of NOx contained in the exhaust gas of the engine 1, such as the rotation speed of the engine 1, the coolant temperature, the intake air temperature, the catalyst bed temperature of the SCR 61 of the SCR device 6, the fuel injection amount, the fuel injection period, the detection result of the engine outlet NOx sensor 91, and the detection result of the SCR outlet NOx sensor 92. Note that in this embodiment, the information representing the operating state of the engine 1 includes at least the detection information of the engine outlet NOx sensor 91 (or the SCR outlet NOx sensor 92) which detects the concentration of NOx in the exhaust passage 3. However, the pre-correction urea water injection amount calculation unit 103 may calculate (estimate) the amount of NOx contained in the exhaust gas of the engine 1 without using the detection results of the engine outlet NOx sensor 91 and the SCR outlet NOx sensor 92.

[0025] The urea water injection amount correction unit (injection amount correction unit) 104 calculates a corrected injection amount by correcting the pre-correction injection amount calculated by the pre-correction urea water injection amount calculation unit 103 based on the time rate of change (time differential value, also simply referred to as the change rate) of the rotation speed of the engine 1 and the time rate of change of the fuel injection amount of the engine 1. At this time, the urea water injection amount correction unit 104 calculates the corrected injection amount by correcting the pre-correction injection amount so that the injection amount of urea water increases when at least both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are positive, and decreases when at least both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative. The urea water injection amount correction unit 104 may further adjust the corrected injection amount so that the integrated value of the difference between the pre-correction injection amount and the corrected injection amount becomes zero. The urea water injection amount correction unit 104 may further adjust the corrected injection amount so that the injection amount of urea water is equal to or greater than a predetermined lower limit when decreasing the injection amount of urea water.

[0026] Fig. 3 shows a configuration example of the urea water injection amount correction unit 104 shown in Fig. 2. The urea water injection amount correction unit 104 shown in Fig. 3 includes a urea water injection amount correction coefficient calculation unit 105, a multiplier 106, and a correction amount adjustment unit 107, and receives an uncorrected urea water injection amount D11, an engine speed change rate D12, and a fuel injection amount change rate D13, corrects the uncorrected urea water injection amount D11 to calculate a corrected urea water injection amount D15, and further adjusts the corrected urea water injection amount D15 to output it as a urea water injection amount final value D16. The urea water injection amount correction unit 104 adjusts the corrected urea water injection amount D15 to calculate the final urea water injection amount D16 so that the final urea water injection amount D16 becomes equal to either the pre-correction urea water injection amount D11, the corrected urea water injection amount D15, or a predetermined lower limit value (0.3 ml / s in the following example).

[0027] The urea water injection amount correction coefficient calculation unit 105 calculates the urea water injection amount correction coefficient D14 by using, for example, a table (or map) 1051 shown in Fig. 4. Moreover, the multiplier 106 multiplies the pre-correction urea water injection amount D11 by the urea water injection correction amount coefficient D14 to calculate the corrected urea water injection amount D15. The table 1051 shown in Fig. 4 defines each value of the urea water injection correction amount coefficient D14 corresponding to each combination of the fuel injection amount change rate and the engine speed change rate, using the fuel injection amount change rate [mg / stroke / s] and the engine speed change rate [rpm / s] as parameters. Here, the fuel injection amount change rate indicates an increase in the fuel injection amount change rate when it is a positive value, and indicates a decrease in the fuel injection amount change rate when it is a negative value. The engine speed change rate indicates an increase in the engine speed when it is a positive value, and indicates a decrease in the engine speed when it is a negative value.

[0028] 4, the urea water injection amount correction coefficient calculation unit 105 calculates the urea water injection correction amount coefficient D14 to be "2.0" when the fuel injection amount change rate is 200 [mg / stroke / s] and the engine speed change rate is 200 [rpm / s]. Also, the urea water injection amount correction 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, and when it is greater than "1", the post-correction urea water injection amount D15 becomes larger than the pre-correction urea water injection amount D11 (an upward correction), and when it is less than "1", the post-correction urea water injection amount D15 becomes smaller than the pre-correction urea water injection amount D11 (a downward correction).

[0029] Table 1051 also corresponds to the following trends. That is, when the fuel injection amount increases, it indicates that the load is increasing, and an increase in NOx flowing into SCR 61 can be predicted. Conversely, when the fuel injection amount decreases, a decrease in NOx can be predicted. Also, when there is no change in the fuel injection amount, no correction is made. If the rotation speed increases, the absolute amount of NOx increases. If the rotation speed decreases, it can be inferred that the absolute amount of NOx decreases.

[0030] In addition, the correspondence relationship between the combination of the rate of change of the fuel injection amount and the rate of change of the engine speed and the urea water injection correction amount coefficient D14 can be set based on the results of experiments using an actual machine or the results of simulations using a model.

[0031] 4 is used, the urea water correction coefficient D14 is calculated so that the corrected urea water injection amount D15 increases when at least both the rate of change of the rotation speed and the rate of change of the fuel injection amount are positive, and decreases when at least both the rate of change of the rotation speed and the rate of change of the fuel injection amount are negative, compared to the pre-correction urea water injection amount D11. Also, when the table 1051 shown in FIG. 4 is used, the urea water correction coefficient D14 is calculated so that the corrected urea water injection amount D15 increases when the rate of change of the fuel injection amount is positive, and decreases when the rate of change of the fuel injection amount is negative, compared to the pre-correction urea water injection amount D11.

[0032] Note that the table 1051 is merely an example, and for example, the range of each change rate may be subdivided. Alternatively, the multiplier 106 may calculate the corrected urea water injection amount D15 after interpolating the value of the urea water correction coefficient D14 based on each change rate.

[0033] Next, the correction amount adjustment unit 107 shown in Fig. 3 will be described. For example, as shown in Fig. 5, the correction amount adjustment unit 107 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. The correction amount adjustment unit 107 shown in Fig. 5 receives the corrected urea-water injection amount D15, the uncorrected urea-water injection amount D11, the SCR bed temperature D17, and the urea-water injection amount correction coefficient D14, calculates and outputs the urea-water injection amount final value D16. Note that the example shown in Fig. 5 is different from the correction amount adjustment unit 107 shown in Fig. 3 in that the correction amount adjustment unit 107 newly receives the SCR bed temperature D17.

[0034] The temperature correction value calculation unit 1071 calculates a correction value (referred to as SCR bed temperature correction value D18) for calculating the integrated value of the adsorption amount of ammonia in the SCR 61 based on the SCR bed temperature D17 and the saturated adsorption amount curve of the SCR 61. The saturated adsorption amount curve is a curve that indicates the maximum value of the ammonia adsorption amount of the SCR 61 at each temperature (for example, JP 2010-261388 A), and the SCR bed temperature correction value D18 is a correction value for calculating the integrated value of the adsorption amount of ammonia so that the integrated value does not exceed the saturated adsorption amount, and takes, for example, zero, positive or negative values ​​based on a certain temperature.

[0035] The adder 1072 calculates (final urea water injection amount D16)-(uncorrected urea water injection amount D11)+(SCR bed temperature correction value D18) and outputs the calculation result to the total correction amount calculation unit 1073.

[0036] The total correction amount calculation unit 1073 integrates {(final urea water injection amount D16)-(pre-correction urea water injection amount D11)+(SCR bed temperature correction value D18)} to calculate a total correction amount S. The total correction amount S is an integrated value obtained by adding a correction by the SCR bed temperature correction value D18 to the difference between the final urea water injection amount D16 and the pre-correction urea water injection amount D11, and corresponds to the amount of ammonia estimated to have accumulated in the SCR 61 based on the difference from the injection amount after correction based on the pre-correction urea water injection amount D11. The total correction amount calculation unit 1073 limits the value of the total correction amount S so that the total correction amount S is a value greater than 0.

[0037] The total correction amount calculation unit 1073 integrates the amount of increase from the base urea water injection amount due to the correction as a positive value. At this time, the corrected urea water injection amount D15 minus the uncorrected urea injection amount D11 takes a positive or negative value. When the injection amount is reduced, for example, when the injection amount is limited to 0.3 ml / s or more, the injection amount is reduced from the base urea water injection amount, and the total correction amount S also decreases.

[0038] The total correction amount calculation unit 1073 may use the SCR bed temperature correction value D18 as an upper limit value of the total correction amount S. In this case, the temperature correction value calculation unit 1071 calculates and outputs an upper limit value when calculating an integrated value of the adsorption amount of the SCR 61 based on the SCR bed temperature D17 and the saturated adsorption amount curve of the SCR 61 as the SCR bed temperature correction value (upper limit value) D18. The SCR bed 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. The adder 1072 calculates (urea water injection amount final value D16)-(urea water injection amount before correction D11) and outputs the calculation result to the total correction amount calculation unit 1073. Then, the total correction amount calculation unit 1073 integrates {(urea water injection amount final value D16)-(urea water injection amount before correction D11)} with the SCR bed temperature correction value D18 as an upper limit value to calculate a total correction amount S (where S>0).

[0039] The urea water injection amount final value determination unit 1074 inputs 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, and calculates and outputs the urea water injection amount final value D16 by adjusting the corrected urea water injection amount D15 (by setting the value of the corrected urea water injection amount D15 to a different value depending on the conditions, rather than using the value of the corrected urea water injection amount D15 as the urea water injection amount final value D16 as it is) so that the total injection amount does not change due to the correction relative to the reference urea water injection amount (pre-correction urea water injection amount D11) and so that the injection amount does not fall below a predetermined lower limit value due to a decreasing correction.

[0040] For example, when the SCR bed temperature correction value D18 is within a predetermined range, the urea water injection amount final value determination unit 1074 can calculate the urea water injection amount final value D16 by adjusting the corrected urea water injection amount D15 so that the integrated value of the difference between the pre-correction urea water injection amount D11 (pre-correction injection amount) and the corrected urea water injection amount D15 (corrected injection amount) becomes zero. Alternatively, when the urea water injection amount correction unit 104 reduces the injection amount of urea water, for example, it can calculate the urea water injection amount final value D16 by adjusting the corrected urea water injection amount D15 so that it becomes equal to or greater than a predetermined lower limit value.

[0041] The urea water injection amount final value determination unit 1074 calculates the urea water injection amount final value D16 by dividing the case into the following (1) to (3), for example: (1) when the urea water injection amount correction coefficient D14 (correction coefficient)>1, the urea water injection amount final value D16 (final value)=the corrected urea water injection amount D15, (2) when the urea water injection amount correction coefficient D14≦1 and the total correction amount S>0, the urea water injection amount final value D16=the corrected urea water injection amount D15 (the minimum value is a predetermined lower limit value (e.g., 0.3 ml / s)), and (3) when the urea water injection amount correction coefficient D14≦1 and the total correction amount S=0, the urea water injection amount final value D16=the uncorrected urea water injection amount D11.

[0042] FIG. 6 shows an example of the operation of the urea water injection amount final value determination unit 1074. In the example of operation shown in FIG. 6, the urea water injection amount final value determination unit 1074 first provisionally 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 equal to or 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 process shown in FIG. 6. In this case, the urea water injection amount final value D16 becomes the corrected urea water injection amount D15.

[0043] On the other hand, when the urea water injection amount correction coefficient D14 is equal to or less than 1 ("Y" in step S102), the urea water injection amount final value determination unit 1074 judges whether the pre-correction urea water injection amount D11 exceeds the lower limit value (0.3 ml / s) (step S103). When the pre-correction urea water injection amount D11 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 pre-correction urea water injection amount D11 (step S106) and ends the process shown in FIG. 6. In this case, the urea water injection amount final value D16 becomes the pre-correction urea water injection amount D11.

[0044] On the other hand, if the pre-correction urea water injection amount D11 is below the lower limit (0.3 ml / s) (if "Y" in step S103), the urea water injection amount final value determination unit 1074 judges 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 up to the total correction amount S=0 (step S105), and ends the process shown in Fig. 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.

[0045] On the other hand, when the total correction amount S=0 (when "N" is determined in step S104), the urea water injection amount final value determination unit 1074 sets the urea water injection amount final value D16 to the pre-correction urea water injection amount D11 (step S106) and ends the process shown in Fig. 6. In this case, the urea water injection amount final value D16 becomes the pre-correction urea water injection amount D11.

[0046] As described above, the control device 100 of this embodiment is a control device that controls 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), and is equipped with a pre-correction injection amount calculation unit 103 that calculates a pre-correction urea water injection amount D11 (pre-correction injection amount) of urea water based on the operating state of the engine 1, and a urea water injection amount correction unit 104 (injection amount correction unit) that calculates a corrected urea water injection amount D15 by correcting the pre-correction urea water injection amount D11 based on the time rate of change of the rotation speed of the engine 1 (engine rotation 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 urea water increases when at least both the engine rotation speed change rate D12 and the fuel injection amount change rate D13 are positive, and decreases when at least both the engine rotation speed change rate D12 and the fuel injection amount change rate D13 are negative. According to this embodiment, the injection amount of urea water can be corrected with a simple configuration even when the increase in the fuel injection amount is large and the increase in the engine speed is large.

[0047] 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 integrated value of the difference between the pre-correction urea water injection amount D11 and the corrected urea water injection amount D15 becomes zero. With this configuration, the injection amounts of urea water before and after correction can be made the same. Furthermore, according to this embodiment, even if the pre-correction urea water injection amount D11 is such that the total amount of injection amount for a predetermined time is optimized for the system, the optimization can be maintained with the corrected injection amount.

[0048] Furthermore, when the urea water injection amount correction section 104 (injection amount correction section) further reduces the injection amount of urea water, it can adjust the corrected urea water injection amount D15 so that it is equal to or greater than a predetermined lower limit value.

[0049] (Example of operation of exhaust purification system 10) Next, an example of the operation of the exhaust purification system 10 will be described with reference to Fig. 7. The operation shown in Fig. 7 is repeated at a predetermined cycle. In the operation shown in Fig. 7, first, the control device 100 (e.g., the urea water injection amount control unit 102) acquires the engine speed and the fuel injection amount (e.g., from the fuel injection amount control unit 101) (step S201). Next, the control device 100 (e.g., the urea water 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 speed and fuel injection amount of the engine 1 change (S203).

[0050] Next, the uncorrected urea water injection amount calculation unit 103 predicts the NOx emission amount and calculates the uncorrected urea water injection amount D11 (step S204). If the rate of change of the fuel injection amount is a negative value (NOx decreases) in step S204, the urea water injection amount correction unit 104 corrects the injection amount (step S205), which reduces the urea water injection amount (step S206). Then, the engine outlet NOx sensor 91 detects the decrease in NOx (step S207), so the uncorrected urea water injection amount D11 decreases (step S208).

[0051] On the other hand, if the rate of change in the fuel injection amount is a positive value (NOx increases) in step S204, the urea water injection amount correction unit 104 corrects the injection amount (step S209), which increases the urea water injection amount (step S210). Then, the engine outlet NOx sensor 91 detects the increase in NOx (step S211), so the pre-correction urea water injection amount D11 increases (step S212).

[0052] FIG. 8 shows an example of the control of the urea water injection amount according to this embodiment. From the top, the graphs show the time change of the rate of change of the fuel injection amount and the rate of change of the engine speed, the time change of the measurement result of the engine outlet NOx sensor 91 and the urea water injection amount (before correction), and the time change of the measurement result of the engine outlet NOx sensor 91 and the urea water injection amount (after correction). The urea water injection amount (after correction) increases by an area A1 shown by hatching with diagonal lines corresponding to the increase C1 in the rate of change of the fuel injection amount. After that, when the urea water injection amount (before correction) exceeds the lower limit value of 0.3 ml / s, the urea water injection amount (after correction) decreases by an area A2 to the lower limit value of 0.3 ml / s. 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 value of 0.3 ml / s, the time during which the urea water injection amount reaches the maximum value is shortened, and the risk of urea deposits accumulating inside the exhaust passage can be suppressed.

[0053] On the other hand, for the decrease C2 in the rate of change of the fuel injection amount, since the fuel injection amount (before correction) is below the lower limit value of 0.3 ml / s, the urea water injection amount (after correction) does not change from the fuel injection amount (before correction).

[0054] On the other hand, with respect to the increase C3 in the rate of change of the fuel injection amount, the urea water injection amount (after correction) increases by the amount of the area A3.

[0055] As described above, according to this embodiment, for example, (1) by calculating the change in NOx from 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 detects the change in NOx in the exhaust gas. This makes it possible to cover the delay time until the NOx sensor detects the change in the amount of NOx in the exhaust gas, thereby increasing the degree of freedom in the installation location of the NOx sensor.

[0056] Even if the amount of urea injection is changed, the control device will increase the amount of urea injection if the NOx sensor detects a change in NOx in the exhaust gas. At this time, by subtracting the increased amount of urea water injection in (1) above, the amount of urea per unit of exhaust gas can be reduced, and the risk of urea deposits accumulating inside the exhaust pipe can be reduced.

[0057] Although the embodiment of the present invention has been described above with reference to the drawings, the specific configuration is not limited to the above embodiment, and design changes and the like within the scope of the gist of the present invention are also included. For example, in Fig. 3, the correction amount adjustment unit 107 may be omitted and the corrected urea water injection amount D15 may be set as the urea water injection amount final value D16, and in Fig. 5, the temperature correction value calculation unit 1071 may be omitted, or the total value correction amount calculation unit 1073 may be omitted and case classification based on the total correction amount S may be omitted in the urea water injection amount final value determination unit 1074.

[0058] Furthermore, a part or all of the programs executed by the computer in the above-described embodiments can be distributed via a computer-readable recording medium or a communication line. [Explanation of symbols]

[0059] 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 purification system, 91... engine outlet NOx sensor, 92... SCR outlet NOx sensor, 93... SCR bed 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 an injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, a pre-correction injection amount calculation unit that calculates a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; an injection amount correction unit that calculates a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, such that the injection amount of the reducing agent increases with respect to the pre-correction injection amount when at least both of the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are positive, and that the injection amount of the reducing agent decreases with respect to the pre-correction injection amount when at least both of the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative; A control device comprising:

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

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

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

5. A control method for controlling an injection amount of a reducing agent supplied to a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, comprising: calculating a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; calculating a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, such that the injection amount of the reducing agent increases with respect to the pre-correction injection amount when at least both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are positive, and such that the injection amount of the reducing agent decreases with respect to the pre-correction injection amount when at least both the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative; A control method comprising:

6. A selective reduction catalyst provided in an exhaust passage of the internal combustion engine; an injection device that injects a reducing agent to be supplied to the selective reduction catalyst; a control device that controls an injection amount of the reducing agent by the injection device, The control device includes a pre-correction injection amount calculation unit that calculates a pre-correction injection amount of the reducing agent based on an operating state of the internal combustion engine; an injection amount correction unit that calculates a corrected injection amount by correcting the pre-correction injection amount based on a time rate of change of a rotation speed of the internal combustion engine and a time rate of change of a fuel injection amount of the internal combustion engine, such that the injection amount of the reducing agent increases with respect to the pre-correction injection amount when at least both of the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are positive, and that the injection amount of the reducing agent decreases with respect to the pre-correction injection amount when at least both of the time rate of change of the rotation speed and the time rate of change of the fuel injection amount are negative; An exhaust purification system comprising:

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