JP6575441B2 - Urea injection control device - Google Patents

Description

  The present invention relates to a urea injection control device.

  Conventionally, a urea SCR (Selective Catalytic Reduction) system using urea as post-processing for purifying exhaust gas of an internal combustion engine is known. In the urea SCR system, nitrogen oxide (NOx) contained in the exhaust is reduced by adding urea to the exhaust. Urea used in the urea SCR system is supplied as urea water. Urea contained in the urea water precipitates as a solid due to concentration or temperature change. The solid precipitate causes clogging in a path from a urea water tank that stores urea water to an injector that injects urea water. Such clogging leads to a shortage of urea water injection amount and hinders normal purification of NOx. Therefore, as a technique for detecting clogging in the path, it has been proposed to check whether or not the motor that drives the urea water pump that pressurizes the urea water has stepped out. However, in this method, it is difficult to detect precipitates that are generated after the motor is stopped and before the motor is started again.

  In Patent Document 1, it is proposed to detect clogging while operating a motor that drives a urea water pump in order to quickly detect clogging. In the case of Patent Document 1, clogging is detected while the motor is operated, thereby detecting clogging due to freezing of urea water and clogging due to precipitates in the urea water path. However, in the case of Patent Document 1, it is not possible to determine a mechanical abnormality that occurs in the motor that drives the urea water pump. Therefore, in Patent Document 1, even when a mechanical abnormality occurs in the motor, an erroneous determination is caused if the urea water path is clogged. As described above, Patent Document 1 has a problem that the cause of insufficient supply of urea water becomes insufficient.

Japanese Patent Laying-Open No. 2015-175362

  Accordingly, an object of the present invention is to provide a urea injection control device that identifies the cause of insufficient supply of urea water including a mechanical abnormality of a motor.

  According to the first aspect of the present invention, consumption determining means is provided. The consumption amount determination means acquires the consumption amount of urea water from the amount of urea water stored in the urea water tank. The comprehensive determination unit determines whether the motor is abnormal including the determination result in the consumption determination unit or whether the urea water path is clogged. That is, the comprehensive judgment means uses the rotation speed of the motor, the presence / absence of freezing of urea water, the pressure of urea water, and the consumption amount of urea water to cause the lack of urea water injection from the injector. Determine if it is abnormal or in the urea water pathway. Therefore, it is possible to identify the cause of the insufficient supply of urea water including the mechanical abnormality of the motor.

The block diagram which shows the structure of the urea injection control apparatus by one Embodiment. The schematic diagram which shows the exhaust gas purification system to which the urea injection control apparatus by one Embodiment is applied Schematic showing the relationship between time and motor torque Schematic showing the relationship between time and motor speed Schematic showing the relationship between time and the temperature of urea water in the urea water tank Schematic showing the relationship between time and urea water pressure in the urea water path Schematic showing the relationship between time and the level of urea water in the urea water tank Schematic which shows the flow of a process of the urea injection control apparatus by one Embodiment.

Hereinafter, an embodiment of a urea injection control device will be described with reference to the drawings.
First, an exhaust gas purification system for an internal combustion engine to which a urea injection control device (hereinafter abbreviated as “control device”) is applied will be described.

  As shown in FIG. 2, the exhaust gas purification system 10 constitutes an SCR system that adds urea water to exhaust gas discharged from an internal combustion engine 11 mounted on a vehicle, for example, and reduces NOx contained in the exhaust gas. Exhaust gas from the internal combustion engine 11 is released to the atmosphere via an exhaust passage 13 formed by the exhaust pipe member 12. The internal combustion engine 11 is a diesel engine, for example. The exhaust purification system 10 may be applied not only to a diesel engine but also to a gasoline engine or a gas turbine engine. Further, the exhaust purification system 10 is not limited to the on-board internal combustion engine 11, but may be applied to a stationary internal combustion engine 11 such as a power generation unit, for example.

  The exhaust purification system 10 includes a urea water tank 14, a urea water pump 15, a urea water piping unit 16, a reduction catalyst 17, and an injector 18. The urea water tank 14 stores an aqueous solution of urea that is urea water. The urea water pump 15 discharges the urea water stored in the urea water tank 14 to the urea water path 19 formed by the urea water piping section 16. The reduction catalyst 17 is provided in the exhaust passage 13 formed by the exhaust pipe member 12. The urea water tank 14 and the injector 18 are connected via a urea water path 19 formed by the urea water piping section 16. Thereby, the urea water pump 15 supplies the urea water pumped from the urea water tank 14 to the injector 18 via the urea water path 19. The injector 18 is provided on the exhaust pipe member 12. The injector 18 penetrates the exhaust pipe member 12 and has a tip exposed to the exhaust passage 13. The urea water supplied to the injector 18 is injected into the exhaust gas flowing through the exhaust passage 13. Exhaust gas discharged from the internal combustion engine 11 and urea water injected from the injector 18 are mixed in the exhaust passage 13 and flow into the reduction catalyst 17. NOx contained in the exhaust is reduced by a chemical reaction with urea contained in the urea water in the reduction catalyst 17.

  A urea water pump 15 that supplies urea water from the urea water tank 14 to the injector 18 is driven by a motor 21. The motor 21 is, for example, a DC three-phase sensorless brushless motor. The motor 21 generates driving force by the electric power supplied from the control device 30. The control device 30 receives power supply from the battery 22. The urea water stored in the urea water tank 14 is supplied to the injector 18 by driving the urea water pump 15 with the motor 21.

  The above-described exhaust purification system 10 is controlled by the control device 30. Specifically, the control device 30 controls the operation of the urea water pump 15 and the injector 18 that constitute the exhaust purification system 10. The control device 30 implements a motor abnormality determination unit 32, a freezing determination unit 33, a blockage determination unit 34, a consumption amount determination unit 35, a comprehensive determination unit 36, and a heater drive unit 37 in software. The motor abnormality determination unit 32, the freezing determination unit 33, the blockage determination unit 34, the consumption amount determination unit 35, the comprehensive determination unit 36, and the heater drive unit 37 may be realized in hardware. It may be realized by cooperation.

  In addition to the motor 21, the control device 30 is connected to a temperature sensor 41, a pressure sensor 42, a level sensor 43 and a thawing heater 44 as shown in FIGS. 1 and 2. The control device 30 supplies power to the motor 21 and detects the torque and rotation speed of the motor 21. The motor abnormality determination unit 32 acquires the torque and rotation speed from the motor 21. The temperature sensor 41 is provided in the urea water tank 14 and detects the temperature of the urea water stored in the urea water tank 14. The freeze determination unit 33 acquires the temperature of the urea water detected by the temperature sensor 41 from the temperature sensor 41. In this case, the temperature sensor 41 may be provided not only in the urea water tank 14 but also in the urea water path 19. Further, the temperature of the urea water is not only detected directly from the temperature sensor 41 provided in the urea water tank 14 or the urea water path 19 but also indirectly detected from, for example, the outside air temperature or the temperature of the cooling water of the internal combustion engine 11. It is good also as a structure. The pressure sensor 42 is provided on the urea water outlet side of the urea water pump 15 and detects the pressure of the urea water discharged from the urea water pump 15. The blockage determination unit 34 acquires the pressure of the urea water detected by the pressure sensor 42 from the pressure sensor 42. In this case, the pressure sensor 42 may be provided not only on the outlet side of the urea water pump 15 but in the urea water path 19. The level sensor 43 is provided in the urea water tank 14 and detects the liquid level position of the urea water stored in the urea water tank 14. The consumption determination unit 35 acquires the level of urea water detected by the level sensor 43 from the level sensor 43. In this case, the level sensor 43 may be configured to indirectly detect the urea water level from the volume or weight of the urea water instead of the urea water level. The thawing heater 44 is provided in the urea water tank 14. The thawing heater 44 generates heat when energized from the heater driving unit 37 of the control device 30. As a result, the urea water frozen in the urea water tank 14 is thawed by the heat generated by the thawing heater 44.

  The motor abnormality determination unit 32 determines whether there is an abnormality in the motor 21 that drives the urea water pump 15. Specifically, the motor abnormality determination unit 32 acquires at least one of the torque or the rotation speed of the motor 21 from the motor 21. And the motor abnormality determination part 32 determines whether the torque of the motor 21 is more than the upper limit torque Ta from the acquired rotation of the motor 21, or the rotation speed of the motor 21 is below the lower limit rotation speed Ri. . That is, the motor abnormality determination unit 32 determines whether the torque of the motor 21 is equal to or higher than the upper limit torque Ta between the abnormality detection start timing D1 and the abnormality detection end timing D2, as shown in FIG. In this embodiment, the motor abnormality determination unit 32 detects the torque of the motor 21 from the value of the current that drives the motor 21. Further, as shown in FIG. 4, the motor abnormality determination unit 32 determines whether or not the rotational speed of the motor 21 is equal to or lower than the lower limit rotational speed Ri between the abnormality detection start timing D1 and the abnormality detection end timing D2. The upper limit torque Ta and the lower limit rotational speed Ri are arbitrarily set according to, for example, the performance of the motor 21, the urea water pump 15, and the exhaust purification system 10 using these. Further, a period from the abnormality detection start time D1 to the abnormality detection end time D2 is also arbitrarily set. As an example, in this embodiment, the upper limit torque Ta is set to Ta = 70 mN / m, and the lower limit rotation speed is set to 900 rpm. The period from the abnormality detection start time D1 to the abnormality detection end time D2 is set to 5.0 seconds. Thus, the motor abnormality determination unit 32 determines whether or not an abnormality has occurred in the motor 21 based on whether or not the torque of the motor 21 is equal to or higher than the upper limit torque Ta or the rotational speed is equal to or lower than the lower limit rotational speed Ri. judge.

  The freezing determination unit 33 determines whether or not the urea water is frozen. Specifically, the freezing determination unit 33 acquires the temperature of the urea water stored in the urea water tank 14 from the temperature sensor 41. And the freezing determination part 33 determines whether the urea water is frozen from the temperature of the acquired urea water. The freezing determination unit 33 determines that the urea water is frozen when the detected temperature of the urea water is equal to or lower than the melting point Tm. That is, as shown in FIG. 5, the freezing determination unit 33 determines whether or not the temperature of the urea water is equal to or lower than the melting point Tm between the abnormality detection start timing D1 and the abnormality detection end timing D2. In the case of this embodiment, the freezing determination unit 33 detects the temperature of the urea water from the voltage output from the temperature sensor 41. Although the melting point Tm depends on the concentration of urea water, in the case of general-purpose urea water, Tm = −11 ° C. As described above, the freezing determination unit 33 determines whether or not the urea water is frozen based on the temperature of the urea water.

  The blockage determination unit 34 determines whether or not the urea water path 19 is clogged. Specifically, the blockage determination unit 34 acquires the pressure of the urea water discharged from the urea water pump 15 to the urea water path 19 from the pressure sensor 42. And the blockade determination part 34 determines whether the pressure of urea water is below upper limit pressure Px from the pressure of the acquired urea water. That is, the blockage determination unit 34 determines whether or not the pressure of the urea water is equal to or lower than the upper limit pressure Px between the abnormality detection start timing D1 and the abnormality detection end timing D2, as shown in FIG. In the case of this embodiment, the blockage determination unit 34 detects the pressure of urea water from the voltage output from the pressure sensor 42. The upper limit pressure Px is arbitrarily set according to, for example, the performance of the motor 21, the urea water pump 15, and the exhaust purification system 10 using these. As an example, in the present embodiment, the upper limit pressure Px is set to Px = 600 kPa. As described above, the blockage determination unit 34 determines whether or not the urea water path 19 is clogged based on the pressure of the urea water in the urea water path 19.

  The consumption determination unit 35 determines whether there is an abnormality in the urea water consumption. Specifically, the consumption amount determination unit 35 acquires the consumption amount of urea water in the urea water tank 14, that is, the change in the liquid level from the level sensor 43. And the consumption determination part 35 determines whether the acquired consumption C of urea water is below predetermined consumption Cs. That is, the consumption determination unit 35 calculates the urea water consumption C from the change in the liquid level position of the urea water tank 14 between the abnormality detection start timing D1 and the abnormality detection end timing D3 as shown in FIG. . Then, the consumption determination unit 35 determines whether or not the calculated consumption C is equal to or less than the predetermined consumption Cs. In the present embodiment, the consumption determination unit 35 detects the liquid level position of the urea water from the voltage output from the level sensor 43. The abnormality detection end time D3 is set after the abnormality detection end time D2. In the present embodiment, the period from the abnormality detection start time D1 to the abnormality detection end time D3 is set to 540 seconds.

  The consumption amount C of urea water correlates with the period from the abnormality detection start timing D1 to the abnormality detection end timing D3. That is, when there is no abnormality in the urea water path 19 and the motor 21, the consumption amount C of the urea water increases with the passage of time from the abnormality detection start timing D1, and the liquid level position of the urea water in the urea water tank 14 decreases. On the other hand, when there is an abnormality in the urea water path 19 or the motor 21, the consumption amount C of the urea water does not increase sufficiently even if time elapses from the abnormality detection start timing D1. Thus, the consumption amount C of urea water correlates with the period from the abnormality detection start timing D1 to the abnormality detection end timing D3, that is, the operation period of the motor 21. The predetermined consumption Cs is determined in advance according to the period from the abnormality detection start timing D1 to the abnormality detection end timing D3, the performance of the exhaust purification system 10, and the like.

  As described above, when there is no abnormality in the urea water path 19 and the motor 21, the urea water stored in the urea water tank 14 is consumed with time. That is, the liquid level position of the urea water tank 14 decreases with time. That is, when there is no abnormality in the motor 21 and the urea water passage 19, the liquid level position Vh in FIG. 7 is lowered to the liquid level position Vl. However, when there is an abnormality in the urea water path 19 or the motor 21, the urea water stored in the urea water tank 14 is not consumed sufficiently with time. That is, the liquid level position of the urea water tank 14 becomes dull in comparison with a case where there is no abnormality. That is, when there is an abnormality in the motor 21 or the urea water path 19, the liquid surface position in the urea water tank 14 does not decrease from the liquid surface position Vh to the liquid surface position Vl in FIG. It drops only to the liquid level position Vm between Vl. That is, the predetermined consumption Cs corresponds to the difference between the liquid level position Vh and the liquid level position Vl. Accordingly, the consumption amount determination unit 35 calculates the urea water consumption amount C from the change amount of the liquid surface position from the abnormality detection start timing D1 to the abnormality detection end timing D3, and the calculated consumption amount C is the predetermined consumption amount. It is determined whether it is Cs or less. As described above, the consumption determination unit 35 determines whether or not the urea water consumption C is abnormal based on the urea water consumption C in the urea water tank 14.

  Based on the determination results of the above-described motor abnormality determination unit 32, freezing determination unit 33, blockage determination unit 34, and consumption amount determination unit 35, the comprehensive determination unit 36 determines whether there is a mechanical abnormality in the motor 21 or the urea water path. It is determined whether 19 is clogged. That is, the comprehensive determination unit 36 includes a motor abnormality determination unit 32, a freezing determination unit 33, a blockage determination unit 34, and a consumption amount determination unit 35. The overall determination unit 36 determines that the motor 21 is abnormal by the motor abnormality determination unit 32, determines that the urea water is not frozen by the freezing determination unit 33, and determines that the pressure of the urea water is abnormal by the blockage determination unit 34. When the consumption amount determination unit 35 determines that the consumption amount C of the urea water is equal to or less than the predetermined consumption amount Cs, it is determined that the urea water path 19 is clogged. On the other hand, the general determination unit 36 determines that the motor 21 has an abnormality in the motor abnormality determination unit 32, determines that the urea water is not frozen in the freezing determination unit 33, and abnormally determines the pressure of the urea water in the blockage determination unit 34. And when the consumption determining unit 35 determines that the urea water consumption C is greater than the predetermined consumption Cs, it is determined that a mechanical abnormality has occurred in the motor 21 that drives the urea water pump 15. To do.

  The heater driving unit 37 intermittently energizes the thawing heater 44 based on the temperature of the urea water acquired by the freezing determination unit 33. That is, the heater driving unit 37 turns on the thawing heater 44 when it is determined that the temperature of the urea water is equal to or lower than the melting point Tm and the urea water is frozen. Thus, the heater driving unit 37 controls energization to the thawing heater 44 based on the determination in the freezing determination unit 33.

Next, a processing flow of the control device 30 according to the present embodiment will be described with reference to FIG.
When the clogging determination is started, the control device 30 starts driving the motor 21 (S101). The control device 30 drives the motor 21 by energizing the motor 21 along a preset energization pattern. When the motor 21 is driven, the motor abnormality determination unit 32 acquires at least one of the torque and the rotation speed of the motor 21 (S102). The motor abnormality determination unit 32 determines whether the torque of the motor 21 is equal to or higher than the upper limit torque Ta or the rotation speed of the motor 21 is equal to or lower than the lower limit rotation speed Ri from the torque or rotation speed of the motor 21 acquired in S102. (S103).

  If the motor abnormality determination unit 32 determines in S103 that the torque is equal to or higher than the upper limit torque Ta, or the rotational speed of the motor is equal to or lower than the lower limit rotational speed Ri (S103: Yes), the process proceeds to abnormality detection in the urea water path 19 (S104). That is, when the torque of the motor 21 is equal to or higher than the upper limit torque Ta or the rotational speed of the motor 21 is equal to or lower than the lower limit rotational speed Ri, there is a possibility that an abnormality has occurred in either the motor 21 or the urea water path 19. Therefore, in addition to the determination of the abnormality of the motor 21 by the motor abnormality determination unit 32, the determination of the abnormality in the urea water path 19 by the freezing determination unit 33, the blockage determination unit 34, and the consumption determination unit 35 is started.

  The freezing determination part 33 will acquire the temperature of urea water from the temperature sensor 41, if it transfers to determination of the abnormality in the urea water path | route 19 in S104 (S105). And the freezing determination part 33 determines whether the temperature of the urea water acquired by S105 is below melting | fusing point Tm (S106). That is, the freezing determination unit 33 determines whether or not the temperature of the urea water is below the melting point Tm and is frozen.

  When the freezing determination unit 33 determines that the temperature of the urea water is higher than the melting point Tm (S106: No), the blockage determination unit 34 acquires the pressure of the urea water from the pressure sensor 42 (S107). That is, the freezing determination unit 33 determines that the urea water is not frozen when the temperature of the urea water is higher than the melting point Tm. Thereby, the blockade determination part 34 acquires the pressure of urea water in S107, when it determines with urea water not being frozen. Then, the blockage determination unit 34 determines whether or not the pressure of the urea water acquired in S107 is equal to or higher than the upper limit pressure Px (S108). That is, the blockage determination unit 34 determines whether or not the pressure of the urea water in the urea water path 19 is equal to or higher than the upper limit pressure Px.

  If the blockage determination unit 34 determines that the pressure of the urea water is equal to or higher than the upper limit pressure Px (S108: Yes), the consumption determination unit 35 acquires the urea water level from the level sensor 43 (S109). . And the consumption determination part 35 calculates the consumption C of urea water from the liquid level position of urea water acquired by S109. Furthermore, the consumption determination unit 35 determines whether or not the calculated consumption C of urea water is equal to or less than the predetermined consumption Cs (S110). That is, the consumption determination unit 35 determines whether or not the consumption C of urea water is equal to or less than the predetermined consumption Cs.

  When the consumption determining unit 35 determines that the consumption amount of urea water is equal to or less than the predetermined consumption amount Cs (S110: Yes), the overall determination unit 36 determines that the urea water path 19 is clogged ( S111). That is, the comprehensive determination unit 36 determines that the motor 21 is abnormal in S103, the urea water is not frozen in S106, the pressure of the urea water is equal to or higher than the upper limit pressure Px in S108, and the urea water When the consumption amount C is less than or equal to the predetermined consumption amount Cs, it is determined that the urea water path 19 is clogged. That is, when the consumption amount C of urea water is equal to or less than the predetermined consumption amount Cs, it is considered that the flow of urea water is inhibited in any part of the urea water path 19. Therefore, when it is determined in S110 that the consumption amount C of urea water is equal to or less than the predetermined consumption amount Cs, the overall determination unit 36 finally determines that the urea water path 19 is clogged.

  On the other hand, when the consumption determining unit 35 determines that the urea water consumption C is greater than the predetermined consumption Cs (S110: No), the overall determination unit 36 determines that the motor 21 has a mechanical abnormality. (S112). That is, the comprehensive determination unit 36 determines that the motor 21 is abnormal in S103, the urea water is not frozen in S106, the pressure of the urea water is equal to or higher than the upper limit pressure Px in S108, and the urea water When the consumption amount C is greater than the predetermined consumption amount Cs, it is determined that a mechanical abnormality has occurred in the motor 21. That is, when the consumption amount C of urea water is larger than the predetermined consumption amount Cs, it is unlikely that the flow of urea water is hindered in any part of the urea water path 19. Therefore, if it is determined in S110 that the consumption amount C of urea water is greater than the predetermined consumption amount Cs, the overall determination unit 36 finally determines that a mechanical abnormality has occurred in the motor 21.

  By the way, when it is determined that the torque of the motor 21 is less than the upper limit torque Ta and the rotation speed of the motor 21 is greater than the lower limit rotation speed Ri in S103 (S103: No), the comprehensive determination unit 36 is abnormal in the urea water path 19. (S113). That is, when the motor abnormality determination unit 32 determines that the torque of the motor 21 is less than the upper limit torque Ta and the rotation speed is greater than the lower limit rotation speed Ri, the motor 21 is operating normally. Therefore, the comprehensive determination unit 36 finally determines that there is no abnormality in the urea water path 19. Similarly, when it is determined in S108 that the pressure of the urea water is lower than the upper limit pressure Px (S108: No), the comprehensive determination unit 36 determines that there is no abnormality in the urea water path 19 (S113). That is, when the blockage determination unit 34 determines that the pressure of the urea water is less than the upper limit pressure Px, the urea water path 19 is not clogged. Therefore, the comprehensive determination unit 36 finally determines that there is no abnormality in the urea water path 19.

  Further, when it is determined in S106 that the temperature of the urea water is equal to or lower than the melting point Tm (S106: Yes), the freezing determination unit 33 determines that the urea water is frozen (S114). Therefore, the freezing determination unit 33 turns on the thawing heater 44 (S115). Thereby, the frozen urea water is thawed by the heat generated by the thawing heater 44. The freezing determination unit 33 continues the thawing process in S115 until the temperature of the urea water becomes higher than the melting point Tm.

  In the embodiment described above, the control device 30 includes the consumption determination unit 35. The consumption amount determination unit 35 acquires the consumption amount C of urea water from the change in the liquid level position of the urea water stored in the urea water tank 14. The comprehensive determination unit 36 determines whether the motor 21 is abnormal including the determination result in the consumption determination unit 35 or whether the urea water path 19 is clogged. That is, the comprehensive determination unit 36 uses the urea water consumption C as an element for determining clogging in addition to the torque and rotation speed of the motor 21, the presence or absence of freezing of urea water, and the pressure of urea water. Thereby, it is specified whether the cause of insufficient urea water injection from the injector 18 is a mechanical abnormality of the motor 21 or clogging in the urea water path 19. Specifically, the comprehensive determination unit 36 determines the torque and rotation speed of the motor 21 by the motor abnormality determination unit 32, the determination of the freezing of the urea water in the freezing determination unit 33, and the pressure of the urea water in the blockage determination unit 34. In addition to the determination, the cause of the shortage of urea water injection including the consumption amount C of the urea water in the consumption determination unit 35 is specified. When the consumption determination unit 35 determines that the urea water consumption C has not reached the predetermined consumption Cs, the overall determination unit 36 determines that the urea water path 19 is clogged. On the other hand, when it is determined by the consumption determination unit 35 that the consumption amount C of the urea water has reached the predetermined consumption amount Cs, the comprehensive determination unit 36 does not clog the urea water path 19 but mechanically applies it to the motor 21. It is determined that an abnormality has occurred. As described above, the overall determination unit 36 determines whether the urea water path 19 is clogged or the motor 21 is mechanically abnormal based on the urea water consumption C in the consumption determination unit 35. Therefore, it is possible to accurately identify the cause of the insufficient supply of urea water including the mechanical abnormality of the motor 21.

  The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

  In the drawing, 11 is an internal combustion engine, 13 is an exhaust passage, 14 is a urea water tank, 15 is a urea water pump, 17 is a reduction catalyst, 18 is an injector, 19 is a urea water path, 21 is a motor, and 30 is a control device (urea). Injection control apparatus), 32 is a motor abnormality determination unit (motor abnormality determination unit), 33 is a freezing determination unit (freezing determination unit), 34 is a blockage determination unit (blockage determination unit), and 35 is a consumption amount determination unit (consumption amount determination). Means) and 36 indicate a comprehensive judgment unit (general judgment means).

Claims (5)

In order to add the urea water stored in the urea water tank (14) to the exhaust of the internal combustion engine (11) and reduce the nitrogen oxides contained in the exhaust by the reduction catalyst (17), the exhaust passage ( 13) and the urea water tank (14) connecting the urea water tank (14) and the injector (18) to the injector (18) from the urea water tank (14). A urea injection control device (30) for controlling a urea water pump (15) for supplying urea water to 18),
Motor abnormality determination means (32) for acquiring rotation of the motor (21) for driving the urea water pump (15) and determining whether the motor (21) is abnormal;
Freezing determination means (33) for acquiring the temperature of the urea water supplied from the urea water tank (14) and determining whether or not the urea water is frozen;
Whether the pressure of the urea water discharged from the urea water pump (15) to the urea water path (19) is acquired, and the pressure of the urea water in the urea water path (19) is equal to or lower than a preset upper limit pressure Occlusion determination means (34) for determining whether or not ;
A consumption determining means (35) for acquiring the amount of urea water stored in the urea water tank (14) and determining whether there is an abnormality in the consumption of urea water;
Based on the determination results of the motor abnormality determination means (32), the freezing determination means (33), the blockage determination means (34), and the consumption amount determination means (35) , injection of urea water from the injector (18) Comprehensive judgment means (36) for judging whether the cause of the shortage is an abnormality of the motor (21) or clogging in the urea water path (19);
A urea injection control device comprising:
The motor abnormality determination means (32) determines whether the torque of the motor (21) is equal to or higher than a preset upper limit torque from the acquired rotation of the motor (21), or the rotational speed of the motor (21). Whether or not is below the lower limit rotational speed,
The freezing determination means (33) determines whether the urea water is frozen from the acquired temperature of the urea water,
The blockage determining means (34) determines whether the pressure of the urea water is equal to or lower than a preset upper limit pressure from the acquired pressure of the urea water,
The urea injection control device according to claim 1, wherein the consumption determination means (35) determines whether or not the acquired consumption of urea water is equal to or less than a predetermined consumption determined in advance. The comprehensive judgment means (36)
The determination as to whether the urea water path (19) is clogged or the motor (21) is mechanically abnormal is based on a determination result by the consumption determination means (35). 3. The urea injection control device according to 2. The comprehensive judgment means (36)
In the motor abnormality determination means (32), it is determined that the torque of the motor (21) is not less than the upper limit torque, or the rotation speed of the motor (21) is not more than the lower limit rotation speed,
In the freezing determination means (33), it is determined that the urea water is not frozen,
In the blockage determining means (34), it is determined that the pressure of the urea water is equal to or higher than the upper limit pressure,
When it is determined in the consumption determination means (35) that the consumption of the urea water is equal to or less than the predetermined consumption,
The urea injection control device according to claim 3, wherein it is determined that clogging has occurred in the urea water path (19). The comprehensive judgment means (36)
In the motor abnormality determination means (32), it is determined that the torque of the motor (21) is not less than the upper limit torque, or the rotation speed of the motor (21) is not more than the lower limit rotation speed,
In the freezing determination means (33), it is determined that the urea water is not frozen,
In the blockage determining means (34), it is determined that the pressure of the urea water is equal to or higher than the upper limit pressure,
When the consumption determining means (35) determines that the consumption amount of the urea water is the predetermined consumption amount,
The urea injection control device according to claim 1, wherein it is determined that a mechanical abnormality has occurred in the motor (21).

Images