JP2019035343A - Electronic control unit for exhaust emission control system - Google Patents

Abstract

To provide an electronic control unit for an exhaust emission control system for determining adhesion of urea to a motor by using a simple configuration by using torque of the motor for driving an urea water pump.SOLUTION: An electronic control unit 30 is used for an exhaust emission control system for reducing nitrogen oxide included in exhaust gas of an internal combustion engine. The electronic control unit 30 includes a torque calculation section 32 and a determination section 36. The torque calculation section 32 acquires torque generated by a motor 21 for driving an urea water pump 15 as motor torque. When the motor torque calculated by the torque calculation section 32 is larger than preset set torque, the determination section 36 determines that urea adheres to the motor 21.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic control device of an exhaust purification system.

Conventionally, a urea SCR (Selective Catalytic Reduction) system using urea is known as an exhaust gas purification system for purifying exhaust gas from an internal combustion engine (see Patent Document 1). In the urea SCR system, nitrogen oxide (NOx) contained in the exhaust is reduced by adding urea to the exhaust.
However, since urea water is an aqueous solution of urea, the contained urea adheres to the motor as crystals due to, for example, a change in concentration. If urea adheres to the motor that drives the urea water pump, the mechanical part malfunctions. As a result, there is a problem in that the NOx purification rate is reduced due to the short supply amount of urea water, and the current consumption in the motor is increased due to an increase in required torque.

Japanese Patent Laid-Open No. 2006-142249

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic control device for an exhaust purification system that determines the adhesion of urea to a motor with a simple structure by using the torque of a motor that drives a urea water pump.

  In the first aspect of the invention, the torque calculation unit calculates the torque of the motor that drives the urea water pump as the motor torque. The determination unit determines that urea is fixed to the motor when the motor torque calculated by the torque calculation unit is larger than a preset set torque. A difference occurs in the torque generated by the load applied to the motor. For example, when the load applied to the motor increases, the torque generated by the motor, that is, the motor torque also increases. On the other hand, when the motor is fixed due to urea contained in the urea water, the load applied to the motor by the fixed urea increases. Thus, there is a correlation between the adhesion of urea in the motor and the motor torque. Therefore, the determination unit determines that urea is fixed to the motor when the motor torque is larger than the set torque. In this case, the determination unit uses the motor torque calculated by the torque calculation unit. Therefore, it is possible to determine the adhesion of urea to the motor with an existing configuration and a simple structure without incurring additional parts.

1 is a schematic block diagram showing an electronic control unit of an exhaust purification system according to a first embodiment. The schematic diagram which shows the exhaust gas purification system by 1st Embodiment Schematic showing the relationship between motor rotation speed and PWM signal duty ratio and motor generated torque Schematic which shows the flow of control by the electronic controller of the exhaust gas purification system by 1st Embodiment. Schematic which shows the flow of control by the electronic controller of the exhaust gas purification system by 2nd Embodiment. Schematic which shows the flow of control by the electronic controller of the exhaust gas purification system by 3rd Embodiment.

Hereinafter, an electronic control unit of an exhaust purification system according to a plurality of embodiments will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the site | part substantially common in several embodiment, and description is abbreviate | omitted.
(First embodiment)
An exhaust purification system 10 according to the first embodiment shown in FIG. 2 constitutes an SCR system that adds urea water to exhaust discharged from an internal combustion engine 11 mounted on a vehicle, for example, and reduces NOx contained in the exhaust. ing. 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 is not limited to a diesel engine as the internal combustion engine 11, but may be applied 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 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 pressure sensor 17, a reduction catalyst 18, and an injector 19. The urea water tank 14 stores an aqueous solution of urea that is urea water. The urea water pump 15 is accommodated in the urea water tank 14. The urea water pump 15 is driven by a motor 21. That is, the urea water pump 15 is driven by supplying electric power to the motor 21, pressurizes the urea water sucked from the urea water tank 14, and discharges it to the urea water passage 22 formed by the urea water pipe section 16. Further, the urea water pump 15 discharges the urea water stored in the urea water tank 14 to the urea water passage 22 when the motor 21 rotates in the preset normal rotation direction. On the other hand, the urea water pump 15 sucks the urea water present in the urea water passage 22 and the injector 19 back into the urea water tank 14 when the motor 21 rotates in the reverse rotation direction opposite to the normal rotation direction. The urea water pump 15 may be provided outside the urea water tank 14 without being accommodated in the urea water tank 14. The reduction catalyst 18 is provided in the exhaust passage 13 formed by the exhaust pipe member 12. The pressure sensor 17 is provided in the urea water passage 22 and detects the pressure of the urea water in the urea water passage 22.

  The injector 19 is provided in the exhaust pipe member 12 that forms the exhaust passage 13. The injector 19 penetrates the exhaust pipe member 12 and the tip is exposed to the exhaust passage 13. The urea water passage 22 is connected to the injector 19 at the end opposite to the urea water tank 14. The urea water discharged from the urea water pump 15 is supplied to the injector 19 via the urea water passage 22. The urea water supplied from the urea water tank 14 is injected into the exhaust gas flowing through the exhaust passage 13 from a nozzle hole (not shown) provided at the tip of the injector 19. Exhaust gas discharged from the internal combustion engine 11 and urea water injected from the injector 19 are mixed in the exhaust passage 13 and flow into the reduction catalyst 18. NOx contained in the exhaust is reduced by a chemical reaction with urea contained in the urea water in the reduction catalyst 18.

  The above-described exhaust purification system 10 is controlled by the electronic control unit 30. The electronic control unit 30 is composed of a microcomputer having a CPU, ROM and RAM (not shown). The electronic control unit 30 controls each part of the vehicle on which the internal combustion engine 11 including the exhaust purification system 10 is mounted. As an example, the electronic control unit 30 sets the injection amount of urea water injected from the injector 19 based on the amount and concentration of NOx contained in the exhaust gas detected by a NOx sensor (not shown). In this case, the electronic control unit 30 corrects the injection amount of the urea water based on, for example, the amount of fuel supplied to the internal combustion engine 11 and the temperature of exhaust gas flowing through the exhaust passage.

  As shown in FIG. 1, the electronic control unit 30 includes a pump drive unit 31, a torque calculation unit 32, a target pressure control unit 33, an injector drive unit 34, an operation acquisition unit 35, a determination unit 36, and a removal control unit 37. . The electronic control unit 30 executes a computer program stored in the ROM to thereby execute a pump drive unit 31, a torque calculation unit 32, a target pressure control unit 33, an injector drive unit 34, an operation acquisition unit 35, a determination unit 36, and The removal control unit 37 is realized by software. The pump drive unit 31, the torque calculation unit 32, the target pressure control unit 33, the injector drive unit 34, the operation acquisition unit 35, the determination unit 36, and the removal control unit 37 may be realized in hardware, and software It may be realized by cooperation with hardware.

  The pump drive unit 31 is connected to the motor 21 of the urea water pump 15 and controls the drive of the motor 21. Thereby, the pump drive unit 31 drives the motor 21 in the forward rotation direction or the reverse rotation direction. The torque calculation unit 32 is connected to the motor 21 and calculates the torque of the motor 21 as the motor torque T1. Specifically, the torque calculation unit 32 acquires the rotation speed of the motor 21 and the duty ratio of the PWM signal from the motor 21. The rotational speed of the motor 21 and the duty ratio of the PWM signal are acquired from a command output from the pump drive unit 31 to the motor 21. For example, as shown in FIG. 3, the torque calculation unit 32 calculates the motor torque T1 based on a map showing the relationship between the rotational speed R acquired from the motor 21 and the duty ratio Dr of the PWM signal. The ROM of the electronic control device 30 stores, for example, a map shown in FIG. The map shown in FIG. 3 is an example. The map indicating the relationship between the rotational speed R and the duty ratio Dr of the PWM signal can be arbitrarily set according to the exhaust purification system 10 to be applied. Further, the map indicating the relationship between the rotational speed R and the duty ratio Dr of the PWM signal is not limited to the ROM of the electronic control device 30 and may be stored in a storage medium (not shown) connected to the electronic control device 30. Further, the torque calculation unit 32 may calculate the torque of the motor 21 using a parameter other than the above index, or may be configured to directly detect the torque of the motor 21 using a torque sensor (not shown).

  The target pressure control unit 33 controls the motor 21 through the pump drive unit 31. Specifically, the target pressure control unit 33 controls the motor so that the pressure P of urea water discharged from the urea water pump 15 in the urea water passage 22 becomes the preset target pressure Pt. The target pressure control unit 33 is connected to the pressure sensor 17 and controls the motor 21 based on the urea water pressure P in the urea water passage 22 acquired by the pressure sensor 17. In this case, the pressure sensor 17 is provided as an essential member in the exhaust purification system 10 regardless of whether or not the present embodiment is the present embodiment. That is, the pressure sensor 17 is provided as an essential configuration for driving the motor 21 based on the pressure of urea water.

  The injector drive unit 34 is connected to the injector 19 and controls the injection of urea water from the injector 19. The operation acquisition unit 35 is connected to the ignition switch 41. The ignition switch 41 turns on or off the operation of the internal combustion engine 11. The driving acquisition unit 35 acquires whether the ignition switch 41 is turned on or off.

  The determination unit 36 determines whether or not urea adheres to the motor 21. The determination unit 36 compares the motor torque T1 calculated by the torque calculation unit 32 with a preset set torque Tt. Then, the determination unit 36 determines that urea is fixed to the motor 21 when the acquired motor torque T1 is larger than the set torque Tt. The torque generated by the motor 21 varies depending on the load applied to the motor 21. When the load applied to the motor 21 increases, the torque generated by the motor 21, that is, the motor torque T1 also increases. Here, when the motor 21 is fixed due to urea contained in the urea water, the fixed urea prevents the motor 21 from rotating. Therefore, when urea is fixed, the load on the motor 21 increases. Thus, there is a correlation between the adhesion of urea in the motor 21 and the motor torque T1. Therefore, the determination unit 36 determines that urea is fixed to the motor 21 when the motor torque T1 is larger than the set torque Tt. The set torque Tt can be arbitrarily set in accordance with the exhaust purification system 10 to be applied, for example, several millimeters Nm to several tens of millimeters Nm. The determination unit 36 preferably determines whether or not urea is stuck in the motor 21 after the pressure P of the urea water discharged from the urea water pump 15 reaches the target pressure Pt.

  The removal control unit 37 executes control for removing the fixed urea. Specifically, when the determination unit 36 determines that urea is fixed to the motor 21, the removal control unit 37 performs control for removing urea fixed to the motor 21. In the case of the first embodiment, the removal control unit 37 executes sticking removal control in order to remove stuck urea.

  The sticking removal control includes purge control, filling control, and re-purge control. The removal control unit 37 drives the motor 21 in the forward rotation direction through the pump drive unit 31 during the filling control. Thus, the removal control unit 37 fills the urea water passage 22 with the urea water in the urea water tank 14 during the filling control. That is, during the filling control, the urea solution in the urea solution tank 14 is fed into the urea solution passage 22 by the urea solution pump 15 by driving the motor 21 in the forward rotation direction. In the case of this filling control, the removal control unit 37 sets the pressure of the urea water that fills the urea water passage 22 to the filling pressure Pp. This filling pressure Pp is set to a pressure higher than the target pressure Pt. Thereby, in the case of filling control, urea water is filled into the urea water passage 22 at a filling pressure Pp higher than the target pressure Pt. On the other hand, the removal control unit 37 drives the motor 21 in the reverse rotation direction through the pump drive unit 31 during purge control and re-purge control. Thereby, the removal control unit 37 sucks the urea water supplied to the urea water passage 22 back into the urea water tank 14 during the purge control and the re-purge control. That is, during the purge control and the re-purge control, the urea solution existing in the urea solution passage 22 is sucked back into the urea solution tank 14 by the urea solution pump 15 by driving the motor 21 in the reverse rotation direction. In this way, the removal control unit 37 sequentially executes purge control, filling control, and re-purge control as the sticking removal control. That is, the urea water is sucked back from the urea water passage 22 to the urea water tank 14 and then filled into the urea water passage 22 at a high pressure in the sticking removal control. The urea water filled in the urea water passage 22 at a high pressure is sucked back into the urea water tank 14 again.

Next, the procedure of sticking determination and urea removal by the electronic control unit 30 having the above configuration will be described with reference to FIG.
The sticking determination process for determining the sticking of urea shown in FIG. 4 is performed after the operation of the internal combustion engine 11 is started. The internal combustion engine 11 starts operation when the ignition switch 41 is turned on (S101). When the internal combustion engine 11 starts operation, the target pressure control unit 33 drives the motor 21 of the urea water pump 15 to control the urea water pressure P to the target pressure Pt (S102). That is, the target pressure control unit 33 drives the motor 21 through the pump drive unit 31. Then, the target pressure control unit 33 controls the pressure P of the urea water discharged from the urea water pump 15 to the urea water passage 22 to the target pressure Pt. At this time, the pump drive unit 31 drives the motor 21 of the urea water pump 15 in the forward rotation direction.

  When the motor 21 is driven and discharge of urea water is started, the determination unit 36 determines whether or not the pressure P of urea water has reached the target pressure Pt (S103). That is, the determination unit 36 acquires the urea water pressure P in the urea water passage 22 from the pressure sensor 17. Then, the determination unit 36 determines whether or not the pressure P of urea water acquired from the pressure sensor 17 has reached the target pressure Pt, that is, whether Pt ≦ P. When determining that the pressure P of the urea water in the urea water passage 22 is less than the target pressure Pt (S103: No), the determination unit 36 waits until the pressure P of the urea water reaches the target pressure Pt.

  When the determination unit 36 determines that the pressure P of the urea water in the urea water passage 22 has reached the target pressure Pt (S103: Yes), the torque calculation unit 32 acquires the rotational speed R of the motor 21 (S104). . The torque calculation unit 32 acquires the duty ratio Dr of the PWM signal in addition to the rotational speed R of the motor 21 (S105). The torque calculator 32 calculates the torque generated by the motor 21 as the motor torque T1 from the acquired rotation speed R of the motor 21 and the duty ratio Dr of the PWM signal using the map shown in FIG. 3 (S106). Then, the determination unit 36 determines whether or not the motor torque T1 calculated by the torque calculation unit 32 is larger than the set torque Tt (S107). That is, the determination unit 36 determines whether or not the motor torque T1 calculated by the torque calculation unit 32 is equal to or lower than the set torque Tt when the urea water pressure P reaches the target pressure Pt.

  When the determination unit 36 determines that the motor torque T1 is equal to or less than the set torque Tt (S107: Yes), the motor 21 of the urea water pump 15 is continuously driven through the target pressure control unit 33 and the pump drive unit 31, and the urea water Is maintained at the target pressure Pt (S108). That is, the determination unit 36 determines that urea does not adhere to the motor 21 when the motor torque T1 is equal to or less than the set torque Tt. Thereby, the target pressure control part 33 drives the motor 21 through the pump drive part 31, and maintains the pressure P of the urea water in the urea water passage 22 at the target pressure Pt as usual. As described above, the torque generated by the motor 21 increases according to the load of the motor 21. If urea is fixed to the motor 21, the load on the motor 21 increases and the motor torque T1 exceeds the set torque Tt. On the other hand, when the motor torque T1 is equal to or less than the set torque Tt, it is considered that urea is not fixed to the motor 21. Therefore, when the determination unit 36 determines that the motor torque T1 is equal to or less than the set torque Tt, the target pressure control unit 33 maintains the urea water pressure P in the urea water passage 22 at the target pressure Pt.

  The determination unit 36 determines whether or not the ignition switch 41 is turned off when the urea water pressure P in the urea water passage 22 is maintained at the target pressure Pt (S109). The determination unit 36 continues the process in S108 while the ignition switch 41 is on (S109: No). On the other hand, when the ignition switch 41 is turned off (S109: Yes), the determination unit 36 performs purge control (S110). During the purge control, the pump drive unit 31 drives the motor 21 of the urea water pump 15 in the reverse rotation direction. As a result, the urea water filling the urea water passage 22 is sucked back from the urea water passage 22 to the urea water tank 14. The pump drive unit 31 stops the motor 21 when the urea water suction back of the urea water passage 22 is completed (S111). For example, the pump drive unit 31 determines completion of sucking back of the urea water based on the pressure of the urea water in the urea water passage 22 detected by the pressure sensor 17. When the motor 21 is stopped in S111, the sticking determination process ends.

  By the way, if the determination part 36 determines in S107 that the motor torque T1 is larger than the set torque Tt (S107: No), it performs sticking removal control. Specifically, in the sticking removal control, the removal control unit 37 first executes purge control (S112). During the purge control, the removal control unit 37 drives the motor 21 of the urea water pump 15 in the reverse rotation direction through the pump drive unit 31 as in S110. As a result, the urea water filling the urea water passage 22 is sucked back from the urea water passage 22 to the urea water tank 14. When the purge control in S112 is completed, the removal control unit 37 executes the filling control (S113). During the filling control, the removal control unit 37 drives the motor 21 of the urea water pump 15 in the forward rotation direction through the pump drive unit 31. Then, during this filling control, the removal control unit 37 drives the motor 21 so that the pressure P of urea water in the urea water passage 22 becomes a filling pressure Pp higher than the target pressure Pt. That is, during the filling control, the removal control unit 37 increases the load of the motor 21 more than the supply of the urea water to the normal target pressure Pt so that the urea water pressure P in the urea water passage 22 is reduced to the filling pressure Pp. Increase. The removal control unit 37 drives the motor 21 based on the urea water pressure P in the urea water passage 22 acquired by the pressure sensor 17 to control the filling pressure Pp.

  When the urea water pressure P in the urea water passage 22 reaches the filling pressure Pp by the filling control, the removal control unit 37 executes the re-purge control (S114). During the re-purge control, the removal control unit 37 drives the motor 21 of the urea water pump 15 in the reverse rotation direction through the pump drive unit 31 as in the purge control in S112. As a result, the urea water filled in the urea water passage 22 at the filling pressure Pp is sucked back into the urea water tank 14 from the urea water passage 22. In this way, the removal control unit 37 removes urea adhering to the motor 21 by sequentially executing purge control, filling control, and re-purge control. Urea adhering to the motor 21 is removed by the pressure change of urea water in these purge control, filling control and re-purge control, and the flow of urea water accompanying this pressure change. When the removal control unit 37 executes the sticking removal control from S112 to S114, the removal control unit 37 returns to S108. Thereby, the target pressure control unit 33 controls the pressure P of the urea water in the urea water passage 22 to the target pressure Pt.

  As described above, in the first embodiment, the torque calculation unit 32 calculates the torque generated by the motor 21 that drives the urea water pump 15 as the motor torque T1. The determination unit 36 determines that urea is fixed to the motor 21 when the motor torque T1 calculated by the torque calculation unit 32 is greater than a preset set torque Tt. In this case, the determination unit 36 only compares the calculated motor torque T1. The rotation speed R of the motor 21 and the duty ratio Dr of the PWM signal, which are the basis for calculating the motor torque T1, are acquired as essential data for controlling the urea water pump 15 of the exhaust purification system 10. That is, the motor torque T1 is a value necessary for control, and is not a value that is additionally acquired for determination of sticking. Therefore, it is possible to determine the adhesion of urea to the motor 21 with an existing configuration and a simple structure without incurring additional parts for the determination of urea adhesion.

  In the first embodiment, when the determination unit 36 determines that urea is fixed to the motor 21, sticking removal control for removing the fixed urea is executed. The removal control unit 37 performs purge control, filling control, and re-purge control as the sticking removal control by repeating the rotation of the motor 21 in the reverse direction or the forward direction. By such control, the pressure of the urea water in the urea water passage 22 extending from the urea water tank 14 to the injector 19 is repeatedly reduced by suction and increased to a filling pressure Pp equal to or higher than the target pressure Pt. As a result, urea fixed to the motor 21 is removed with a large pressure change of the urea water. Therefore, urea fixed to the motor 21 can be removed by simple control.

(Second Embodiment)
An electronic control device of an exhaust purification system according to a second embodiment will be described.
The electronic control device 30 of the second embodiment has the same configuration as that of the first embodiment shown in FIG. In the case of the second embodiment, the control executed by the removal control unit 37 is different from that of the first embodiment. In the case of the second embodiment, the removal control unit 37 executes simple removal control in order to remove the fixed urea.

  The simple removal control includes injection control and filling control. The removal control unit 37 injects urea water from the injector 19 through the injector driving unit 34 during injection control. Thereby, the removal control unit 37 drives the injector 19 so as to inject urea water into the exhaust during the injection control. That is, at the time of injection control, the injector 19 opens, so that the urea water in the urea water passage 22 is injected from the injector 19 into the exhaust gas flowing through the exhaust passage 13. On the other hand, the removal control unit 37 drives the motor 21 in the forward rotation direction through the pump drive unit 31 in the same manner as in the first embodiment during the filling control. Thus, the removal control unit 37 fills the urea water passage 22 with the urea water in the urea water tank 14 during the filling control. In the case of this filling control, the removal control unit 37 sets the pressure of the urea water that fills the urea water passage 22 to the filling pressure Pp. Thus, the removal control part 37 performs injection control and filling control in order as simple removal control. That is, the urea water is injected into the exhaust gas from the urea water passage 22 through the injector 19 in the simple removal control, and then filled into the urea water passage 22 at a high pressure.

Next, the procedure of sticking determination and urea removal by the electronic control unit 30 having the above configuration will be described with reference to FIG.
In the second embodiment, the urea sticking determination process from S201 to S211 is the same as S101 to S111, which is the sticking judgment process in the first embodiment, and a description thereof will be omitted.
In the case of the second embodiment, the removal control unit 37 executes simple removal control. When it is determined in S207 that the motor torque T1 is larger than the set torque Tt (S207: No), the removal control unit 37 first executes injection control as the simple removal control (S212). During the injection control, the removal control unit 37 drives the injector 19 through the injector driving unit 34. As a result, the urea water filling the urea water passage 22 is injected into the exhaust gas flowing through the exhaust passage 13 through the injector 19. When the injection control in S212 is completed, the removal control unit 37 performs filling control (S213). The filling control is the same as the control in S113 of the first embodiment. That is, at the time of filling control, the removal control unit 37 drives the motor 21 of the urea water pump 15 in the normal rotation direction through the pump drive unit 31. Then, during this filling control, the removal control unit 37 drives the motor 21 so that the pressure P of urea water in the urea water passage 22 becomes a filling pressure Pp higher than the target pressure Pt. In this way, the removal control unit 37 removes urea fixed to the motor 21 by executing injection control and filling control. Urea adhering to the motor 21 is removed by the flow of urea water accompanying the pressure change of the urea water in these injection control and filling control.

  When the urea water pressure P in the urea water passage 22 reaches the filling pressure Pp by the filling control, the removal control unit 37 returns to S208. Thereby, the target pressure control unit 33 controls the pressure P of the urea water in the urea water passage 22 to the target pressure Pt.

  In the second embodiment, when the determination unit 36 determines that urea is stuck to the motor 21, simple removal control for removing the stuck urea is executed. The removal control unit 37 performs injection control and filling control as simple removal control by injection of urea water from the injector 19 and filling of urea water into the urea water passage 22. By such control, the pressure of the urea water in the urea water passage 22 is repeatedly reduced and increased up to the filling pressure Pp as the urea water is injected. As a result, urea fixed to the motor 21 is removed by a large pressure change of the urea water and the flow of the urea water accompanying this pressure change. Moreover, in 2nd Embodiment, it is not necessary to stop the injection of urea water for the removal of the fixed urea by injecting urea water from the injector 19. Therefore, the fixed urea can be removed while maintaining the urea water injection. Therefore, urea that has adhered to the motor 21 can be removed with simple control while purifying the exhaust gas.

(Third embodiment)
An electronic control device of an exhaust purification system according to a third embodiment will be described.
The configuration of the electronic control device 30 of the third embodiment is the same as that of the first embodiment shown in FIG. In the case of the third embodiment, the control executed in the removal control unit 37 is different from that in the first embodiment, and the determination timing in the determination unit 36 is partially different from that in the first embodiment. In the case of the third embodiment, the removal control unit 37 performs simple removal control in order to remove the fixed urea. At the same time, in the third embodiment, the removal control unit 37 also executes the sticking removal control when it is determined by the simple removal control that urea removal is insufficient. That is, in the third embodiment, when the determination unit 36 determines that urea is stuck to the motor 21, the removal control unit 37 performs simple removal control as a first stage. Then, after removing the fixed urea by the simple removal control, the target pressure control unit 33 executes re-pressurization control with the urea water in the urea water passage 22 as the target pressure Pt. When the urea water is controlled to the target pressure Pt by the re-pressurization control, the determination unit 36 re-determines the fixation of urea to the motor 21. If the removal control unit 37 determines that the urea has been stuck to the motor 21 as a result of the redetermination by the judgment unit 36, the removal control unit 37 executes the sticking removal control.

Next, the sticking determination and urea removal procedures by the electronic control unit 30 having the above-described configuration will be described with reference to FIG.
In the third embodiment, the urea sticking determination process from S301 to S311 is common to S101 to S111, which is the sticking judgment process in the first embodiment, and thus the description thereof is omitted.
In the case of the third embodiment, the removal control unit 37 executes simple removal control in advance. Therefore, when it is determined in S307 that the motor torque T1 is larger than the set torque Tt (S307: No), the removal control unit 37 first executes injection control as the simple removal control (S312). The injection control is the same as the control in S212 of the second embodiment. When the injection control in S312 is completed, the removal control unit 37 executes filling control (S313). The filling control is the same as the control in S113 of the first embodiment and S213 of the second embodiment.

  When the simple removal control including the injection control in S312 and the filling control in S313 is completed, the determination unit 36 controls the urea water pressure P in the urea water passage to the target pressure Pt through the target pressure control unit 33 (S314). That is, the target pressure control unit 33 drives the motor 21 to control the urea water pressure P in the urea water passage 22 to the target pressure Pt. In this case, the target pressure control unit 33 controls the urea water, which has been controlled to the filling pressure Pp in S313, to the target pressure Pt by injecting it from the injector 19 or sucking it back into the urea water tank 14. The control in S314 corresponds to repressurization control. The determination unit 36 determines whether or not the urea water pressure P has reached the target pressure Pt (S315).

  When the urea water pressure P in the urea water passage 22 has not reached the target pressure Pt (S315: No), the determination unit 36 waits until the urea water pressure P reaches the target pressure Pt. When the determination unit 36 determines that the pressure P of urea water in the urea water passage 22 has reached the target pressure Pt (S315: Yes), the torque calculation unit 32 acquires the rotational speed R of the motor 21 (S316). . The torque calculation unit 32 acquires the duty ratio Dr of the PWM signal in addition to the rotation speed R of the motor 21 (S317). The torque calculation unit 32 calculates the torque generated by the motor 21 as the motor torque T1 from the acquired rotation speed R of the motor 21 and the duty ratio Dr of the PWM signal using the map shown in FIG. 3 (S318). Then, the determination unit 36 determines whether or not the motor torque T1 calculated by the torque calculation unit 32 is larger than the set torque Tt (S319). That is, the determination unit 36 determines whether or not the motor torque T1 calculated by the torque calculation unit 32 is equal to or less than the set torque Tt when the pressure P of the urea water reaches the target pressure Pt by the repressurization control.

  If the determination unit 36 determines that the motor torque T1 is equal to or less than the set torque Tt (S319: Yes), the determination unit 36 returns to S308, and drives the motor 21 of the urea water pump 15 through the target pressure control unit 33 and the pump drive unit 31. continue. That is, when the determination unit 36 determines in S319 that the motor torque T1 is equal to or less than the set torque Tt, the determination unit 36 determines that the fixed urea is removed by the simple removal control. Therefore, the determination unit 36 returns to S308. Thereby, the target pressure control unit 33 maintains the pressure P of the urea water at the target pressure Pt.

  On the other hand, when the determination unit 36 determines in S319 that the motor torque T1 is greater than the set torque Tt (S319: No), it performs sticking removal control. That is, when the determination unit 36 determines in S319 that the motor torque T1 is greater than the set torque Tt, the determination unit 36 determines that the fixed urea is not sufficiently removed by the simple removal control. Therefore, the removal control unit 37 executes the sticking removal control in order to further remove the stuck urea. In the sticking removal control, the removal control unit 37 first executes purge control (S320). This purge control is the same as S112 of the first embodiment. When the purge control in S320 is completed, the removal control unit 37 executes filling control (S321). This filling control is the same as S113 in the first embodiment. Then, when the urea water pressure P in the urea water passage 22 reaches the filling pressure Pp by the filling control, the removal control unit 37 executes the re-purge control (S322). This re-purge control is the same as S114 in the first embodiment.

  When the removal control unit 37 executes the sticking removal control from S320 to S322, the process returns to S308. Thereby, the target pressure control unit 33 controls the pressure P of the urea water in the urea water passage 22 to the target pressure Pt.

  In the third embodiment, when the determination unit 36 determines that urea is stuck to the motor 21, simple removal control is executed prior to the sticking removal control in order to remove the stuck urea. In the third embodiment, the simple removal control is preceded before the sticking removal control, so that the sticking removal of urea is executed while maintaining the urea water injection. If it is determined that the removal of the fixed urea is insufficient, the sticking removal control is further executed. As a result, urea removal according to the degree of urea sticking is executed, and the light sticking is removed by simple removal control that maintains the injection of urea water. Therefore, the fixed urea can be reliably removed without sucking back or pressurizing unnecessary urea water.

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.
For example, in the above-described plurality of embodiments, the sticking determination process for determining whether or not urea is stuck to the motor 21 is executed, and when the sticking of urea is determined, the sticking removal control or the simple removal control for removing the stuck urea. An example of executing is described. However, only the sticking determination process may be executed without necessarily performing the sticking removal control or the simple removal control.

  Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

  In the drawings, 10 is an exhaust purification system, 11 is an internal combustion engine, 14 is a urea water tank, 15 is a urea water pump, 19 is an injector, 21 is a motor, 22 is a urea water passage, 30 is an electronic control device, and 32 is a torque calculation. , 33 denotes a target pressure control unit, 36 denotes a determination unit, and 37 denotes a removal control unit.

Claims (7)

Exhaust gas purification system (10) in which urea water stored in a urea water tank (14) is pressurized by a urea water pump (15) and injected into the exhaust of the internal combustion engine (11) to reduce nitrogen oxides contained in the exhaust. Electronic control device)
A torque calculator (32) for calculating the torque of the motor (21) for driving the urea water pump (15) as a motor torque;
A determination unit (36) for determining that urea is fixed to the motor (21) when the motor torque calculated by the torque calculation unit (32) is larger than a preset set torque;
An electronic control unit for an exhaust purification system. A target pressure control unit (33) for controlling the pressure of urea water discharged by driving the urea water pump (15) to a preset target pressure;
The determination unit (36) determines whether urea is fixed to the motor (21) after the pressure reaches the target pressure in the urea water discharged from the urea water pump (15). Item 2. An electronic control unit for an exhaust purification system according to Item 1.   The determination unit (36) further includes a removal control unit (37) that executes control for removing the fixed urea when it is determined that urea is fixed to the motor (21). 3. An electronic control unit for an exhaust purification system according to 1 or 2. The removal control unit (37)
Purge control for driving the motor (21) to suck the urea water supplied to the urea water passage (22) connected to the urea water pump (15) back into the urea water tank (14);
Filling control for driving the motor (21) to fill the urea water passage (22) from the urea water tank (14);
Re-purge control for driving the motor (21) and sucking urea water back from the urea water passage (22) to the urea water tank (14) following the filling control;
The electronic control unit for an exhaust gas purification system according to claim 3, wherein The removal control unit (37)
In the urea water passage (22) connected to the urea water pump (15), the injector (19) connected to the end opposite to the urea water pump (15) is driven, and the urea from the injector (19) Injection control to inject water,
Filling control for driving the motor (21) to fill the urea water passage (22) from the urea water tank (14);
The electronic control unit for an exhaust gas purification system according to claim 3 or 4, wherein:   The said target pressure control part (33) performs the repressurization control which makes the pressure of urea water the said target pressure after the said injection control and the said filling control are performed in the said removal control part (37). 5. An electronic control unit for an exhaust purification system according to 5. The determination unit (36) re-determines whether urea has adhered to the motor (21) after the pressure of urea water is controlled to the target pressure by the repressurization control,
In the determination unit (36), when it is determined again that urea is fixed to the motor (21),
The removal control unit (37)
Purge control for driving the motor (21) to suck the urea water supplied to the urea water passage (22) connected to the urea water pump (15) back into the urea water tank (14);
Filling control for driving the motor (21) to fill the urea water passage (22) from the urea water tank (14);
Re-purge control for driving the motor (21) and sucking urea water back from the urea water passage (22) to the urea water tank (14) following the filling control;
The electronic control unit for an exhaust purification system according to claim 6, wherein:

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