Injection control device and injection control method

Abstract

To cool an injection section of urea water while injecting an amount of urea suitable for NOx emissions.SOLUTION: An injection control device 40 includes: a first catalyst 24 provided in an exhaust passage 13 in which exhaust gas of an engine 10 flows; a first injector 32 provided upstream of the first catalyst 24 in the exhaust passage 13; a specification section 422 that specifies a first cooling injection amount of urea water for cooling the first injector 32 and a first purification injection amount of urea water for eliminating NOx included in exhaust gas on the basis of an exhaust gas temperature, an exhaust gas flow rate and an NOx concentration in the exhaust passage 13; and an injection control section 423 that causes the first injector 32 to inject mixed water obtained by adding an amount of water specified on the basis of the first cooling injection amount and the first purification injection amount to the first purification injection amount of urea water when the first cooling injection amount is larger than the first purification injection amount.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In the exhaust purification device of Patent Document 1, when the urea water injector adds urea water to the exhaust gas and the ammonia concentration in the exhaust gas reaches a predetermined value, the condensed water injector condenses moisture in the intake air and adds condensed water to the exhaust gas, thereby suppressing ammonia slip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-72109 A Summary of the Invention [Problem to be solved by the invention]

[0004] The injection part (so-called needle valve) of the urea water injector is likely to become solidified when the exhaust gas temperature becomes high, so the injection part is cooled by injecting urea water. However, when the amount of urea water required to cool the injection part is greater than the amount of urea water required to reduce NOx, there is a problem in that if urea water is injected with priority given to cooling the injection part, NOx cannot be properly purified, and vice versa.

[0005] The present invention has been made in consideration of these points, and has an object to cool the injection portion of the urea solution while injecting an amount of urea suitable for the amount of NOx emissions. [Means for solving the problem]

[0006] An injection control device according to a first aspect of the present invention includes a first catalyst provided in an exhaust flow path through which exhaust gas from an engine flows, a first injection unit provided upstream of the first catalyst in the exhaust flow path, a determination unit that determines a first cooling injection amount of urea water for cooling the first injection unit and a first purification injection amount of the urea water for purifying NOx contained in the exhaust gas based on an exhaust temperature, an exhaust flow rate, and a NOx concentration in the exhaust flow path, and an injection control unit that, when the first cooling injection amount is greater than the first purification injection amount, injects a mixed water obtained by adding an amount of water determined based on the first cooling injection amount and the first purification injection amount to the urea water in the first purification injection amount into the first injection unit.

[0007] When the first cooling injection amount is larger than the first purification injection amount, the injection control unit may inject mixed water obtained by adding water in an amount obtained by subtracting the first purification injection amount from the first cooling injection amount to the first purification injection amount into the first injection unit.

[0008] The injection control section may inject the first purification injection amount of urea water into the first injection section when the first cooling injection amount is equal to or less than the first purification injection amount.

[0009] The specifying unit may specify the first cooling injection amount based on the exhaust temperature and the exhaust flow rate, and may specify the first purification injection amount based on the exhaust temperature, the exhaust flow rate, and the NOx concentration.

[0010] The exhaust gas temperature control unit may further include a memory unit that stores a cooling injection amount corresponding to the exhaust temperature and the exhaust flow rate, and a purification injection amount corresponding to the exhaust flow rate, the NOx concentration, and the exhaust temperature, and the determination unit may determine the first cooling injection amount and the first purification injection amount by referring to the cooling injection amount and the purification injection amount stored in the memory unit every time a predetermined time has elapsed.

[0011] The memory unit may store a minimum injection amount and a maximum injection amount of the first injection unit corresponding to the exhaust temperature, and the identification unit may identify, among a plurality of injection amounts from the minimum injection amount to the maximum injection amount, the injection amount that matches or is most similar to the cooling injection amount identified by referring to the cooling injection amount stored in the memory unit as the first cooling injection amount, and may identify, as the first purification injection amount, the injection amount that matches or is most similar to the purification injection amount identified by referring to the purification injection amount stored in the memory unit.

[0012] The system may further include a urea water tank for storing the urea water, a water tank for storing the water, and a pump for sending the urea water stored in the urea water tank or a mixed water obtained by mixing the urea water with the water stored in the water tank to the first injection unit, and the injection control unit may cause the pump to send out the urea water or the mixed water.

[0013] The exhaust gas turbine engine may further include a second catalyst provided downstream of the first catalyst in the exhaust flow path, and a second injection unit provided downstream of the first catalyst and upstream of the second catalyst in the exhaust flow path, wherein the identification unit identifies a second cooling injection amount of the urea water for cooling the second injection unit and a second purification injection amount of the urea water for purifying NOx contained in the exhaust downstream of the first catalyst based on an exhaust temperature, an exhaust flow rate, and a NOx concentration downstream of the first catalyst and upstream of the second injection unit in the exhaust flow path, and when the second cooling injection amount is greater than the second purification injection amount, the injection control unit may inject mixed water obtained by adding an amount of water obtained by subtracting the second purification injection amount from the second cooling injection amount to the urea water in the second purification injection amount, into the second injection unit.

[0014] An injection control method according to a second aspect of the present invention includes a determination step executed by a processor to determine a cooling injection amount of urea water for cooling an injection part upstream of a catalyst provided in an exhaust flow path and a purification injection amount of urea water for purifying NOx contained in the exhaust based on the exhaust temperature, exhaust flow rate, and NOx concentration in an exhaust flow path through which engine exhaust flows, and an injection step to inject, into the injection part, a mixed water obtained by adding an amount of water determined based on the cooling injection amount and the purification injection amount to the urea water of the purification injection amount when the cooling injection amount is greater than the purification injection amount.

[0015] An injection control device according to a third aspect of the present invention includes a catalyst provided in an exhaust flow path through which exhaust gas from an engine flows; an injection unit provided upstream of the catalyst in the exhaust flow path and configured to inject the urea water supplied from a tank for storing urea water toward the catalyst; a determination unit configured to determine a cooling injection amount of the urea water for cooling the injection unit and a purification injection amount of the urea water for purifying NOx contained in the exhaust gas based on the exhaust temperature, exhaust flow rate and NOx concentration in the exhaust flow path; and an injection control unit configured to control the amount of water to be mixed with the urea water so that the injection unit injects liquid that is equal to or greater than the cooling injection amount and contains an amount of urea corresponding to the purification injection amount of the urea water.

[0016] An injection control method according to a fourth aspect of the present invention includes a determination step executed by a processor to determine a cooling injection amount of urea water for cooling an injection unit upstream of a catalyst provided in the exhaust flow path and a purification injection amount of urea water for purifying NOx contained in the exhaust based on the exhaust temperature, exhaust flow rate, and NOx concentration in an exhaust flow path through which engine exhaust flows, and an injection step to control the amount of water to be mixed with the urea water so that the injection unit injects liquid that is equal to or greater than the cooling injection amount and contains an amount of urea corresponding to the purification injection amount of urea water. Effect of the Invention

[0017] According to the present invention, it is possible to provide an effect of cooling the injection portion of the urea solution while injecting an amount of urea suitable for the amount of NOx emissions. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram for explaining an overview of a vehicle S according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of an injection control device 40. [Diagram 3] 6A to 6C are diagrams for explaining an operation of injecting urea water or mixed water. [Figure 4] 5 is a diagram showing an example of a processing sequence in the injection control device 40. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] <Overview of Vehicle S> Fig. 1 is a diagram for explaining an overview of a vehicle S according to this embodiment. The vehicle S shown in Fig. 1 includes an engine 10, a turbocharger 11, an intake passage 12, an exhaust passage 13, an intake pressure sensor 14, a first purification device 21, a second purification device 22, a third purification device 23, a first catalyst 24, a second catalyst 25, a third catalyst 26, a fourth catalyst 27, a particulate collection device 28, a first temperature sensor 30, a first nitrogen oxide sensor 31, a first injector 32, a second temperature sensor 33, a second nitrogen oxide sensor 34, a second injector 35, a pump 36, a urea water tank 37, a water tank 38, and an injection control device 40. The vehicle S has a function of cooling the first injector 32 and the second injector 35 while purifying nitrogen oxides (NOx) by injecting urea water from the first injector 32 and the second injector 35.

[0020] The engine 10 is an internal combustion engine that burns and expands a mixture of fuel and intake air (air) to generate power. The supercharger 11 is, for example, a turbocharger, and uses the exhaust flow to increase the density of the intake air. The supercharger 11 has a turbine T provided in the exhaust passage 13 and a compressor C provided in the intake passage 12. The turbine T rotates by receiving exhaust air flowing through the exhaust passage 13. The compressor C is connected to the turbine T via a connecting shaft, and compresses the intake air by rotating together with the turbine T. The intake passage 12 is a passage through which air (intake air) supplied to the engine 10 flows. The exhaust passage 13 is a passage through which exhaust air from the engine 10 flows. The intake pressure sensor 14 is provided in the intake passage 12, and detects the air pressure (intake pressure) of the air supplied to the engine 10.

[0021] The first purification device 21, the second purification device 22, and the third purification device 23 are devices for purifying the exhaust gas of the engine 10. The second purification device 22 is provided downstream of the first purification device 21. The third purification device 23 is provided downstream of the second purification device 22. The first purification device 21 houses a first catalyst 24 and a third catalyst 26. The second purification device 22 houses a particulate collection device 28. The third purification device 23 houses a second catalyst 25 and a fourth catalyst 27.

[0022] The first catalyst 24 and the second catalyst 25 are, for example, SCR (Selective Catalytic Reduction) catalysts provided in the exhaust passage 13 through which the exhaust gas from the engine 10 flows, and purify nitrogen oxides (NOx) contained in the exhaust gas from the engine 10. Specifically, the first catalyst 24 and the second catalyst 25 reduce NOx to nitrogen. The second catalyst 25 is provided downstream of the first catalyst 24 in the exhaust passage 13. In the following description, the first catalyst 24 may be referred to as "SCR 24" and the second catalyst 25 as "SCR 25".

[0023] The third catalyst 26 and the fourth catalyst 27 are, for example, ASC (Ammonia Slip Catalyst), and reduce ammonia slip by oxidizing ammonia (NH3). The fourth catalyst 27 is provided downstream of the third catalyst 26 in the exhaust passage 13. The particulate collector 28 is, for example, DPD (Diesel Particulate Diffuser), and has a DOC (Diesel Oxidation Catalyst) and a particulate matter (PM) collection filter, and collects PM.

[0024] The first temperature sensor 30 and the second temperature sensor 33 are sensors for detecting the temperature of the exhaust gas of the engine 10 flowing through the exhaust path 13. The first temperature sensor 30 detects the temperature of the exhaust gas upstream of the first injector 32 in the exhaust path 13, and the second temperature sensor 33 detects the temperature of the exhaust gas upstream of the second injector 35 in the exhaust path 13. The first nitrogen oxide sensor 31 (hereinafter referred to as "NOx sensor 31") and the second nitrogen oxide sensor 34 (hereinafter referred to as "NOx sensor 34") are sensors for detecting the NOx concentration contained in the exhaust gas of the engine 10 flowing through the exhaust path 13. The NOx sensor 31 detects the NOx concentration of the exhaust gas upstream of the first injector 32 in the exhaust path 13, and the NOx sensor 34 detects the NOx concentration of the exhaust gas upstream of the second injector 35 in the exhaust path 13.

[0025] The first injector 32 and the second injector 35 are components for injecting the urea water or the mixed water of urea water and water delivered by the pump 36 into the exhaust passage 13. The first injector 32 is provided upstream of the SCR 24 in the exhaust passage 13, and injects the urea water or the mixed water into the exhaust gas of the engine 10. The second injector 35 is provided downstream of the SCR 24 and upstream of the SCR 25 in the exhaust passage 13, and injects the urea water or the mixed water into the exhaust gas of the engine 10. The urea water or the mixed water injected from the first injector 32 and the second injector 35 generates ammonia in the exhaust passage 13. Then, in the SCR 24 and the SCR 25, the ammonia reacts with NOx as a reducing agent to generate water and nitrogen, and the exhaust gas is purified. In addition, in the first injector 32 and the second injector 35, the urea water or the mixed water flows through the inside of each injector, so that the urea is less likely to stick. The first injector 32 and the second injector 35 may each be configured by a single injector, or may each include multiple injectors, such as a urea water injector and a water injector.

[0026] The pump 36 delivers urea water stored in a urea water tank 37 or mixed water obtained by mixing the urea water with water stored in a water tank 38 to the first injector 32 and the second injector 35. The pump 36 may deliver mixed water having a different ratio of urea water to water to the first injector 32 and the second injector 35. The pump 36 may deliver urea water to one of the first injector 32 and the second injector 35 and deliver mixed water to the other. The urea water tank 37 is a tank that stores urea water. The water tank 38 is a tank that stores water.

[0027] The injection control device 40 is a housing including electronic components or a printed circuit board on which electronic components are mounted. The injection control device 40 executes a process of determining the amount of urea water or mixed water to be injected by each of the first injector 32 and the second injector 35, and injecting the determined amount of urea water or mixed water to the first injector 32 and the second injector 35. The amount of water to be injected is determined by a cooling injection amount for suppressing adhesion of urea to the needle valves of the first injector 32 and the second injector 35, and a purification injection amount for purifying NOx contained in the exhaust gas flowing through the exhaust passage 13.

[0028] Incidentally, in a system in which an injector injects urea water of a fixed concentration, if the amount of injected water is adjusted to the amount of injected water for purification, and the amount of injected water is smaller than the amount of injected water for cooling, urea is likely to stick to the needle valve of the injector. On the other hand, if the amount of injected water is adjusted to the amount of injected water for cooling, and the amount of injected water is larger than the amount of injected water for purification (i.e., an excess of ammonia is supplied), ammonia slip is likely to occur.

[0029] Therefore, the injection control device 40 injects a liquid that is equal to or greater than the cooling injection amount and contains urea in an amount corresponding to the urea water purification injection amount to the first injector 32 and the second injector 35. The injection control device 40 also controls the concentration of the urea water injected by the first injector 32 and the second injector 35 based on the cooling injection amount and the purifying injection amount. Specifically, when the cooling injection amount is greater than the purifying injection amount, the injection control device 40 injects mixed water obtained by adding water in an amount obtained by subtracting the purifying injection amount from the cooling injection amount to the urea water purification injection amount. That is, the injection control device 40 injects urea water (liquid) in a cooling injection amount with a reduced urea concentration. By operating in this manner, the injection control device 40 injects liquid in an injection amount that does not cause urea to stick to the needle valve (i.e., an injection amount that can cool each injector) and suppresses ammonia slip.

[0030] On the other hand, when the cooling injection amount is smaller than the purification injection amount, the injection control device 40 injects the purification injection amount of urea water. By operating in this manner, the injection control device 40 can inject urea water or mixed water corresponding to the amount of water for cooling the needle valves of the first injector 32 and the second injector 35 so as to suppress adhesion of urea to the needle valves. Furthermore, since the injection control device 40 can inject an amount of urea suitable for the amount of NOx emissions, it is possible to suppress ammonia slip and purify NOx contained in the exhaust gas of the engine 10. The configuration and operation of the injection control device 40 will now be described in detail.

[0031] <Configuration of the injection control device 40> 2 is a diagram showing a configuration of the injection control device 40. The injection control device 40 has a storage unit 41 and a control unit 42. The control unit 42 has an acquisition unit 421, an identification unit 422, and an injection control unit 423.

[0032] The storage unit 41 includes a storage medium such as a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a solid state drive (SSD), etc. The storage unit 41 stores a program executed by the control unit 42.

[0033] The memory unit 41 stores various information for executing a process of determining the injection water amount of the first injector 32 and the second injector 35 and the ratio of urea water to water in the injection water amount. As an example, the memory unit 41 stores a cooling injection amount corresponding to the exhaust temperature and exhaust flow rate of the exhaust gas flowing through the exhaust passage 13, and a purification injection amount corresponding to the exhaust flow rate, NOx concentration, and exhaust temperature. The memory unit 41 also stores a minimum injection amount and a maximum injection amount of the first injector 32 and a minimum injection amount and a maximum injection amount of the second injector 35 corresponding to the exhaust temperature of the exhaust gas flowing through the exhaust passage 13. The minimum injection amount is an injection amount determined as a rating of the injector. The maximum injection amount is an upper limit value of the injection amount that can be injected so that white deposits (so-called deposits) due to urea are not generated.

[0034] The control unit 42 is, for example, a processor such as a CPU (Central Processing Unit) or an ECU (Electronic Control Unit). The control unit 42 functions as an acquisition unit 421, an identification unit 422, and an injection control unit 423 by executing a program stored in the storage unit 41. The control unit 42 may be configured with one processor, or may be configured with multiple processors or a combination of one or more processors and an electronic circuit.

[0035] The configuration of each unit realized by the control unit 42 will be described below. The temperature of the exhaust gas flowing through the exhaust passage 13 is higher upstream of the SCR 24 where the first injector 32 injects than downstream of the SCR 24 and upstream of the SCR 25 where the second injector 35 injects. Therefore, the first injector 32 has a higher risk of urea adhering than the second injector 35. Therefore, in the following description, the operation of the first injector 32 when injecting, out of the first injector 32 and the second injector 35, will be described.

[0036] The acquisition unit 421 acquires the exhaust flow rate of the engine 10, the exhaust temperature of the exhaust upstream of the first injector 32 in the exhaust path 13, and the NOx concentration of the exhaust upstream of the first injector 32 in the exhaust path 13 every time a predetermined time has elapsed. The predetermined time is, for example, 0.1 seconds. The acquisition unit 421 acquires, for example, the air pressure of the air supplied to the engine 10 detected by the intake pressure sensor 14, and calculates the amount of exhaust gas from the engine 10, thereby acquiring the amount of exhaust gas from the engine 10. The acquisition unit 421 acquires, for example, the exhaust temperature detected by the first temperature sensor 30 and the NOx concentration detected by the NOx sensor 31.

[0037] The identifying unit 422 identifies a first cooling injection amount of urea water for cooling the first injector 32, and a first purification injection amount of urea water for purifying NOx contained in the exhaust gas upstream of the first injector 32. The identifying unit 422 identifies the first cooling injection amount and the first purification injection amount based on the exhaust temperature, exhaust flow rate, and NOx concentration upstream of the first injector 32 in the exhaust path 13, which are acquired by the acquiring unit 421.

[0038] The identifying unit 422, for example, at each time a predetermined time has elapsed, refers to the cooling injection amount corresponding to the exhaust temperature and exhaust flow rate stored in the memory unit 41, thereby identifying a first cooling injection amount corresponding to the exhaust temperature and exhaust flow rate acquired by the acquiring unit 421. The identifying unit 422, for example, at each time a predetermined time has elapsed, refers to the purification injection amount corresponding to the exhaust flow rate, NOx concentration, and exhaust temperature stored in the memory unit 41, thereby identifying a first purification injection amount corresponding to the exhaust flow rate, NOx concentration, and exhaust temperature acquired by the acquiring unit 421.

[0039] The determination unit 422 may determine the first cooling injection amount and the first purification injection amount by referring to the minimum injection amount and the maximum injection amount of the first injector 32 corresponding to the exhaust temperature stored in the storage unit 41. The determination unit 422, for example, determines the minimum injection amount and the maximum injection amount corresponding to the exhaust temperature acquired by the acquisition unit 421 by referring to the minimum injection amount and the maximum injection amount of the first injector 32 corresponding to the exhaust temperature stored in the storage unit 41. Then, the determination unit 422 determines, as the first cooling injection amount, an injection amount that matches or is most similar to the cooling injection amount determined by referring to the cooling injection amount stored in the storage unit 41, among a plurality of injection amounts from the minimum injection amount to the maximum injection amount determined. The determination unit 422 determines, as the first purification injection amount, an injection amount that matches or is most similar to the purification injection amount determined by referring to the purification injection amount stored in the storage unit 41, among a plurality of injection amounts from the minimum injection amount to the maximum injection amount determined.

[0040] By operating the specifying unit 422 as described above, it is possible to specify the first cooling injection amount and the first purification injection amount suitable for the exhaust temperature within the range of the injection amount that can be injected by the first injector 32. As a result, it is possible to prevent the first injector 32 from being unable to inject by specifying at least one of the first cooling injection amount and the first purification injection amount smaller than the minimum injection amount, and to prevent the generation of white deposits by specifying at least one of the first cooling injection amount and the first purification injection amount larger than the maximum injection amount.

[0041] The injection control unit 423 causes the pump 36 to deliver urea water or mixed water. When causing the pump 36 to deliver urea water, the injection control unit 423 causes the pump 36 to deliver the urea water stored in the urea water tank 37 to the first injector 32, thereby causing the first injector 32 to inject the urea water. On the other hand, when causing the pump 36 to deliver mixed water, the injection control unit 423 causes the pump 36 to deliver the urea water stored in the urea water tank 37 and the water stored in the water tank 38 to the first injector 32, thereby causing the first injector 32 to inject the mixed water of urea water and water.

[0042] Fig. 3 is a diagram for explaining the operation of injecting urea water or mixed water. Fig. 3(a) shows the first purification injection amount and the first cooling injection amount identified by the identification unit 422. Fig. 3(b) shows the amount of urea water and the amount of water injected by the injector 32. The horizontal axis of Fig. 3 indicates time, and the vertical axis of Fig. 3 indicates the injection amount identified by the injection control unit 423.

[0043] When the first cooling injection amount identified by the identification unit 422 is equal to or less than the first purification injection amount, the injection control unit 423 injects the first purification injection amount of urea water into the first injector 32. For example, at a time before time T1 and a time after time T4 shown in FIG. 3(a), the first cooling injection amount identified by the identification unit 422 is equal to or less than the first purification injection amount. Therefore, as shown in FIG. 3(b), the injection control unit 423 injects the first purification injection amount of urea water (as an example, urea water of the first purification injection amount J0 at time T0) into the first injector 32. By the injection control unit 423 operating in this manner, it is possible to purify NOx contained in the exhaust gas of the engine 10 while cooling the first injector 32.

[0044] When the first cooling injection amount identified by the identification unit 422 is greater than the first purification injection amount, the injection control unit 423 injects mixed water obtained by adding water in an amount obtained by subtracting the first purification injection amount from the first cooling injection amount to the urea water of the first purification injection amount, into the first injector 32. For example, in the period from time T1 to time T4 shown in FIG. 3A, the first cooling injection amount identified by the identification unit 422 is greater than the first purification injection amount. Therefore, as an example, in the period from time T2 to time T3 shown in FIG. 3B, the injection control unit 423 injects mixed water obtained by adding water obtained by subtracting the first purification injection amount J3 from the first cooling injection amount J2 to the urea water of the first purification injection amount J3, into the first injector 32.

[0045] By operating the injection control unit 423 in this manner, the urea contained in the first purification injection amount of urea water can purify NOx contained in the exhaust gas of the engine 10, while the mixed water in the first cooling injection amount can cool the first injector 32. As a result, NOx can be purified while preventing ammonia slip, while suppressing adhesion of urea to the needle valve of the first injector 32.

[0046] Incidentally, even if the injection control unit 423 switches from the mixed water to the urea water and injects it, the pump 36 may cause the first injector 32 to inject the water stored in the water tank 38 for a certain period of time from the time of switching. For example, even if the injection control unit 423 stops the injection of water, the first injector 32 injects water less than the injection amount (J2-J3) for a certain period of time from the time T4 shown in FIG. 3(b). That is, at the time T4, the first injector 32 injects mixed water obtained by mixing the first purification injection amount of urea water necessary for purifying NOx with water less than the injection amount (J2-J3). As a result, the first injector 32 injects water more than the injection amount (J2-J3) for a certain period of time as an injection amount for suppressing the adhesion of urea to the needle valve, but can inject the amount of urea water necessary for purifying NOx.

[0047] <Processing sequence in the injection control device 40> Fig. 4 is a diagram showing an example of a processing sequence in the injection control device 40. The processing sequence shown in Fig. 4 is a sequence showing an operation of the injection control unit 423 to inject urea water or mixed water to the injector 32. The injection control device 40 repeats the processing sequence shown in Fig. 4 at regular time intervals.

[0048] The acquisition unit 421 acquires the exhaust flow rate of the engine 10 (S10), the exhaust temperature of the exhaust upstream of the first injector 32 (S11), and the NOx concentration of the exhaust upstream of the first injector 32 (S12). The identification unit 422 refers to the memory unit 41 to identify a first cooling injection amount A corresponding to the exhaust temperature and exhaust flow rate acquired by the acquisition unit 421 (S13). The identification unit 422 refers to the memory unit 41 to identify a first purification injection amount B corresponding to the exhaust flow rate, NOx concentration, and exhaust temperature acquired by the acquisition unit 421 (S14).

[0049] When the subtraction value obtained by subtracting the first purification injection amount B from the first cooling injection amount A is equal to or less than 0 (NO in S15), the injection control unit 423 injects the first purification injection amount B of urea water into the first injector 32 (S18). When the subtraction value obtained by subtracting the first purification injection amount B from the first cooling injection amount A is greater than 0 (YES in S15), the injection control unit 423 determines the calculated subtraction value (first cooling injection amount A-first purification injection amount B) as the amount of water (S16). The injection control unit 423 injects a mixture of the first purification injection amount B of urea water and the subtraction value (first cooling injection amount A-first purification injection amount B) of water into the first injector 32 (S17).

[0050] <First Modification> In the above description, the operation of the injection control device 40 to inject urea water or mixed water into the first injector 32 has been exemplified, but the present invention is not limited to this. The injection control device 40 may inject urea water or mixed water into the first injector 32 and the second injector 35. Hereinafter, the operation of the injection control device 40 to inject urea water or mixed water into the second injector 35 will be described.

[0051] The acquisition unit 421 further acquires the exhaust temperature upstream of the second injector 35 in the exhaust path 13 and the NOx concentration of the exhaust upstream of the second injector 35 in the exhaust path 13 every time a predetermined time has elapsed. The acquisition unit 421 acquires, for example, the exhaust temperature detected by the second temperature sensor 33 and the NOx concentration detected by the NOx sensor 34.

[0052] The determination unit 422 determines a second cooling injection amount of urea water for cooling the second injector 35 and a second purification injection amount of urea water for purifying NOx contained in the exhaust downstream of the SCR 24 based on the exhaust temperature, exhaust flow rate, and NOx concentration downstream of the SCR 24 and upstream of the second injector 35 in the exhaust path 13.

[0053] The identifying unit 422, for example, at each time a predetermined time has elapsed, refers to the cooling injection amount corresponding to the exhaust temperature and exhaust flow rate stored in the memory unit 41, thereby identifying the second cooling injection amount corresponding to the exhaust flow rate and the exhaust temperature upstream of the second injector 35 acquired by the acquiring unit 421. The identifying unit 422, for example, at each time a predetermined time has elapsed, refers to the purification injection amount corresponding to the exhaust flow rate, the NOx concentration, and the exhaust temperature stored in the memory unit 41, thereby identifying the second purification injection amount corresponding to the exhaust flow rate, the exhaust temperature upstream of the second injector 35, and the NOx concentration acquired by the acquiring unit 421.

[0054] When the second cooling injection amount is equal to or less than the second purification injection amount, the injection control unit 423 injects the second purification injection amount of urea water to the second injector 35. When the second cooling injection amount is greater than the second purification injection amount, the injection control unit 423 injects the second injector 35 with mixed water obtained by adding water in an amount obtained by subtracting the second purification injection amount from the second cooling injection amount to the second purification injection amount of urea water.

[0055] By operating the injection control unit 423 as described above, it is possible to inject mixed water having different ratios of urea water and water to the first injector 32 and the second injector 35. Also, it is possible to inject urea water to one of the first injector 32 and the second injector 35 and inject mixed water to the other. As a result, even if the exhaust temperature and NOx concentration upstream of the first injector 32 are different from the exhaust temperature and NOx concentration upstream of the second injector 35, it is possible to inject appropriate amounts of urea water or mixed water to each of the first injector 32 and the second injector 35.

[0056] <Second Modification> In the above description, the operation of the vehicle S equipped with the first purification device 21 and the third purification device 23 housing the SCR and the ASC has been exemplified, but is not limited to this. The vehicle S may be equipped with one of the first purification device 21 and the third purification device 23. When the vehicle S is equipped with the first purification device 21, the injection control device 40 causes the first injector 32 to inject urea water or mixed water, and when the vehicle S is equipped with the third purification device 23, the injection control device 40 causes the second injector 35 to inject urea water or mixed water.

[0057] <Effects of the injection control device 40> As described above, the injection control device 40 has an identification unit 422 that identifies a first cooling injection amount of urea water for cooling the first injector 32 and a first purification injection amount of urea water for purifying NOx contained in the exhaust gas based on the exhaust temperature, exhaust flow rate, and NOx concentration upstream of the first injector 32 in the exhaust path 13, and an injection control unit 423 that, when the first cooling injection amount is greater than the first purification injection amount, injects a mixed water obtained by adding the first purification injection amount of urea water to an amount of water obtained by subtracting the first purification injection amount from the first cooling injection amount, into the first injector 32.

[0058] By configuring the injection control device 40 in this manner, it is possible to purify NOx contained in the exhaust gas of the engine 10 while cooling the needle valve of the first injector 32 so as to suppress adhesion of urea to the needle valve. Furthermore, since the first injector 32 can inject an amount of urea suitable for the amount of NOx emissions, it is possible to suppress ammonia slip.

[0059] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0060] 10 Engine 11. Turbocharger 12 Intake passage 13 Exhaust duct 14 Intake pressure sensor 21 First Purification Device 22 Second Purification Device 23 Third Purification Device 24 First Catalyst 25 Second catalyst 26 Third Catalyst 27 4th Catalyst 28 Particulate collection device 30 First temperature sensor 31 First nitrogen oxide sensor 32 First injector 33 Second temperature sensor 34 No. 2 nitrogen oxide sensor 35 Second injector 36 Pump 37 Urea tank 38 Water Tank 40 Injection control device 41 Storage section 42 Control section 421 Acquisition Department 422 Specific part 423 Injection control unit

Claims

1. A first catalyst provided in an exhaust flow path through which exhaust gas from the engine flows; a first injection portion provided upstream of the first catalyst in the exhaust flow path; an identifying unit that identifies a first cooling injection amount of the urea water for cooling the first injection unit and a first purification injection amount of the urea water for purifying the NOx contained in the exhaust gas, based on an exhaust temperature, an exhaust flow rate, and a NOx concentration in the exhaust flow path; an injection control unit that, when the first cooling injection amount is greater than the first purification injection amount, injects mixed water obtained by adding water of the first purification injection amount to the urea water of the first purification injection amount and an amount of water determined based on the first cooling injection amount and the first purification injection amount into the first injection unit; An injection control device having

2. When the first cooling injection amount is larger than the first purification injection amount, the injection control unit injects mixed water obtained by adding water in an amount obtained by subtracting the first purification injection amount from the first cooling injection amount to the urea water in the first purification injection amount to the first injection unit. The injection control device according to claim 1 .

3. When the first cooling injection amount is equal to or less than the first purification injection amount, the injection control unit injects the first purification injection amount of urea water into the first injection unit. The injection control device according to claim 1 .

4. The determination unit determines the first cooling injection amount based on the exhaust temperature and the exhaust flow rate, and determines the first purification injection amount based on the exhaust temperature, the exhaust flow rate, and the NOx concentration. The injection control device according to claim 1 .

5. A storage unit stores a cooling injection amount corresponding to the exhaust temperature and the exhaust flow rate, and a purification injection amount corresponding to the exhaust flow rate, the NOx concentration, and the exhaust temperature, the determination unit determines the first cooling injection amount and the first purification injection amount by referring to the cooling injection amount and the purification injection amount stored in the storage unit every time a predetermined time has elapsed. The injection control device according to claim 4.

6. the memory unit stores a minimum injection amount and a maximum injection amount of the first injection unit corresponding to the exhaust temperature, the determination unit determines, among a plurality of injection amounts from the minimum injection amount to the maximum injection amount, the injection amount that matches or is most similar to the cooling injection amount determined by referring to the cooling injection amount stored in the memory unit, as the first cooling injection amount, and determines, as the first purification injection amount, the injection amount that matches or is most similar to the purification injection amount determined by referring to the purification injection amount stored in the memory unit. The injection control device according to claim 5.

7. a urea water tank for storing the urea water; A water tank for storing the water; a pump that delivers the urea water stored in the urea water tank or a mixed water obtained by mixing the urea water and the water stored in the water tank to the first injection part; and The injection control unit causes the pump to deliver the urea water or the mixed water. The injection control device according to claim 1 .

8. a second catalyst provided downstream of the first catalyst in the exhaust passage; a second injection portion provided in the exhaust flow path downstream of the first catalyst and upstream of the second catalyst, the determination unit determines a second cooling injection amount of the urea water for cooling the second injection unit and a second purification injection amount of the urea water for purifying NOx contained in the exhaust gas downstream of the first catalyst, based on an exhaust temperature, an exhaust flow rate, and a NOx concentration downstream of the first catalyst and upstream of the second injection unit in the exhaust flow path, When the second cooling injection amount is larger than the second purification injection amount, the injection control unit injects mixed water obtained by adding water in an amount obtained by subtracting the second purification injection amount from the second cooling injection amount to the urea water in the second purification injection amount to the second injection unit. The injection control device according to claim 1 .

9. The processor executes a determination step of determining a cooling injection amount of urea water for cooling an injection portion upstream of a catalyst provided in an exhaust flow path through which exhaust gas from an engine flows, and a purification injection amount of the urea water for purifying NOx contained in the exhaust gas, based on an exhaust temperature, an exhaust flow rate, and a NOx concentration in the exhaust flow path; an injection step of injecting mixed water obtained by adding a specified amount of water based on the cooling injection amount and the purification injection amount to the urea water of the purification injection amount, when the cooling injection amount is greater than the purification injection amount, into the injection part; The injection control method includes the steps of:

10. A catalyst provided in an exhaust flow path through which engine exhaust flows; an injection unit that is provided upstream of the catalyst in the exhaust flow path and that injects the urea water supplied from a tank that stores the urea water toward the catalyst; an identifying unit that identifies a cooling injection amount of the urea water for cooling the injection unit and a purification injection amount of the urea water for purifying NOx contained in the exhaust gas based on an exhaust temperature, an exhaust flow rate, and a NOx concentration in the exhaust flow path; an injection control unit that controls an amount of water to be mixed with the urea water so that the injection unit injects a liquid that is equal to or greater than the cooling injection amount and contains urea in an amount corresponding to the purification injection amount of the urea water; An injection control device having

11. The processor executes a determination step of determining a cooling injection amount of urea water for cooling an injection portion upstream of a catalyst provided in an exhaust flow path through which exhaust gas from an engine flows, and a purification injection amount of the urea water for purifying NOx contained in the exhaust gas, based on an exhaust temperature, an exhaust flow rate, and a NOx concentration in the exhaust flow path; an injection process for controlling an amount of water to be mixed with the urea water so that the injection unit injects a liquid having an amount of urea that is equal to or greater than the cooling injection amount and contains urea in an amount corresponding to the purification injection amount of the urea water; The injection control method includes the steps of:

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