JP6569556B2 - Urea water injection control device - Google Patents

Description

  The present invention relates to a urea water 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. The urea water stored in the urea water tank is supplied to the injector through the urea water passage and is injected from the injector into the exhaust flowing through the exhaust passage. The urea water is supplied to the injector by a urea water pump. The urea water may precipitate as urea as a solute due to freezing due to a decrease in the outside air temperature or a change in concentration accompanying evaporation of moisture. The precipitated solid urea causes clogging of the injector and the urea water passage. Therefore, in Patent Document 1, the urea water remaining in the urea water passage is collected in the urea water tank by driving the urea water pump in the direction opposite to that when supplying the urea water.

  However, in the case of Patent Document 1, the time for driving the urea water pump in the reverse direction is set according to the surrounding environment of the urea SCR system, such as temperature and atmospheric pressure. For this reason, when individual differences in sensors for detecting the temperature and atmospheric pressure or deterioration with time occur, the drive time in the reverse direction of the urea water pump that is set increases. As a result, if the driving time of the urea water pump in the reverse direction is too short, there is a problem that the urea water remaining in the urea water passage cannot be sufficiently recovered. On the other hand, if the driving time of the urea water pump in the reverse direction is too long, the urea water pump continues to be driven even though the urea water recovery from the urea water passage is completed, and unnecessary power consumption increases. There is a problem of doing.

JP 2009-2260 A

  Accordingly, an object of the present invention is to drive the urea water pump after completion of recovery while avoiding remaining urea water in the urea water passage by determining completion of recovery of urea water from the urea water passage. It is an object of the present invention to provide a urea water injection control device that reduces unnecessary power consumption due to the above.

In the first aspect of the invention, the reverse drive means drives the motor that drives the urea water pump in the direction opposite to that during the supply of the urea water in order to recover the urea water in the urea water passage to the urea water tank. Then, when the determination means is driving the motor by the reverse drive means, is the recovery of the urea water from the urea water passage to the urea water tank completed based on the motor drive state acquired by the drive state acquisition means? Determine whether or not. The motor that drives the urea water pump changes its driving state depending on the presence or absence of urea water in the urea water passage. Therefore, the determination unit determines whether or not the recovery of the urea water is completed from the change in the driving state of the motor acquired by the driving state acquisition unit. In this case, when the driving state acquisition unit determines that the motor is in a stable operating state, the driving state at this time is acquired as a stable driving state, and the determining unit sets a set value based on the stable driving state, It is determined whether or not the recovery of the urea water has been completed based on the driving state and set value of the motor acquired by the driving state acquisition means. Thereby, it is determined whether or not the recovery of the urea water is completed without being influenced by the influence of the external environment such as atmospheric pressure and temperature, and the error of the detection means for detecting them. That is, the completion of the urea water recovery is determined based on the driving state of the motor. Therefore, it is possible to avoid the remaining urea water in the urea water passage and to reduce unnecessary power consumption due to the driving of the urea water pump after the recovery is completed.

The block diagram which shows the urea water injection control apparatus by 1st Embodiment. The schematic diagram which shows the exhaust gas purification system to which the urea water injection control apparatus by 1st Embodiment is applied. Schematic which shows the process of the main routine in the urea water injection control apparatus by 1st Embodiment. Schematic which shows the flow of the determination process of the completion | finish of collection | recovery of urea water in the urea water injection control apparatus by 1st Embodiment. Schematic which shows the time change of the rotation speed of the motor in the urea water injection control apparatus by 1st Embodiment. Schematic which shows the flow of the stop process of the motor in the urea water injection control apparatus by 1st Embodiment. Schematic which shows the flow of the stop process of the motor in the urea water injection control apparatus by 1st Embodiment. Schematic which shows the flow of the determination process of the completion | finish of collection | recovery of urea water in the urea water injection control apparatus by 2nd Embodiment. Schematic which shows the time change of the rotation speed of the motor in the urea water injection control apparatus by 2nd Embodiment. Schematic which shows the flow of the determination process of the completion of collection | recovery of urea water in the urea water injection control apparatus by 3rd Embodiment. Schematic which shows the time change of the rotation speed of the motor in the urea water injection control apparatus by 3rd Embodiment. Schematic which shows the flow of the determination process of the completion of collection | recovery of urea water in the urea water injection control apparatus by 4th Embodiment. Schematic which shows the time change of the rotation speed of the motor in the urea water injection control apparatus by 4th Embodiment.

Hereinafter, urea water injection control devices (hereinafter abbreviated as “control devices”) according to a plurality of embodiments will be described with reference to the drawings. Note that, in a plurality of embodiments, substantially the same components are denoted by the same reference numerals, and description thereof is omitted.
(First embodiment)
First, the exhaust purification system 10 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, to reduce 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 passage portion 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 passage 19 formed by the urea water passage portion 16. The reduction catalyst 17 is provided in the exhaust passage 13 formed by the exhaust pipe member 12. The injector 18 is connected to the urea water tank 14 via the urea water passage 19. The urea water discharged from the urea water pump 15 is supplied to the injector 18 via the urea water passage 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.

  The urea water pump 15 that supplies urea from the urea water tank 14 to the injector 18 is driven by a motor 21. The motor 21 drives the urea water pump 15 in the forward direction and the reverse direction by changing the energization direction or energization pattern from the battery 22. When the urea water pump 15 is driven in the forward direction by the motor 21, the urea water stored in the urea water tank 14 is supplied to the injector 18. On the other hand, when the urea water pump 15 is driven in the reverse direction by the motor 21, the urea water in the urea water passage 19 connected to the injector 18 is collected into the urea water tank 14.

  The above-described exhaust purification system 10 is controlled by the control device 30. As shown in FIG. 1, the control device 30 has a microcomputer 31 composed of a CPU, a ROM, and a RAM, and controls the exhaust purification system 10 by a computer program stored in the ROM. The control device 30 executes the computer program in the microcomputer 31 to realize the drive state acquisition unit 32, the reverse drive unit 33, the determination unit 34, and the motor stop unit 35 in software. The drive state acquisition unit 32, the reverse drive unit 33, the determination unit 34, and the motor stop unit 35 may be realized by hardware, or may be realized by cooperation of software and hardware.

  The drive state acquisition unit 32 acquires the drive state of the motor 21 that drives the urea water pump 15. Specifically, the drive state acquisition unit 32 acquires any one or more of the torque, rotation speed, and current magnitude of the motor 21. The motor 21 is controlled so that the torque or the rotational speed is constant. The drive state acquisition part 32 acquires the rotation speed of the motor 21 as a drive state, when controlling the motor 21 to a fixed torque. Moreover, the drive state acquisition part 32 acquires the electric current supplied to the motor 21 as a drive state, when controlling the motor 21 to a fixed rotation speed. The drive state acquisition unit 32 directly acquires the rotational speed of the motor 21 from, for example, a rotational speed sensor provided in the motor 21. Further, the drive state acquisition unit 32 may indirectly acquire the rotation speed of the motor 21 from the control pattern of the current and voltage supplied to the motor 21.

The reverse drive unit 33 drives the motor 21 that drives the urea water pump 15 in the reverse direction. As described above, the urea water pump 15 and the motor 21 that drives the urea water pump 15 rotate in the forward direction when the urea water stored in the urea water tank 14 is supplied to the injector 18. The reverse drive unit 33 drives the motor 21 in a direction opposite to the forward direction by changing the energization direction or energization pattern from the battery 22 to the motor 21. Thereby, the urea water pump 15 is driven in a direction opposite to that at the time of supplying the urea water. As a result, the urea water remaining in the urea water passage 19 is collected into the urea water tank 14 by the urea water pump 15 rotating in the reverse direction.
The determination unit 34 determines whether or not the recovery of the urea water from the urea water passage 19 to the urea water tank 14 is completed. Specifically, the determination unit 34 acquires the drive state of the motor 21 from the drive state acquisition unit 32 when the reverse drive unit 33 drives the motor 21 in the reverse direction. Then, the determination unit 34 determines completion of urea water recovery based on the acquired driving state of the motor 21.

  In the case of the first embodiment, the determination unit 34 determines whether the recovery of urea water is completed based on the number of rotations of the motor 21. The reverse drive unit 33 controls the torque of the motor 21 rotating in the reverse direction to be constant. At this time, the drive state acquisition unit 32 acquires the rotation speed Rc of the motor 21 rotating in the reverse direction as the drive state of the motor 21. The determination unit 34 determines that the recovery of the urea water from the urea water passage 19 to the urea water tank 14 is completed when the rotation speed Rc of the motor 21 acquired by the drive state acquisition unit 32 becomes equal to or higher than the increase rotation speed Rt. . When urea water remains in the urea water passage 19, the motor 21 that rotates in the reverse direction to collect the urea water is loaded by the urea water remaining in the urea water passage 19. By completing the recovery of the urea water, the load applied from the urea water to the motor 21 is reduced. Therefore, the rotational speed Rc of the motor 21 whose torque is controlled to be constant temporarily increases with the completion of the recovery of the urea water. Thus, the rotation speed Rc of the motor 21 changes according to the change in load caused by the remaining urea water. The determination unit 34 determines the time when the rotational speed Rc of the motor 21 changes as the time when the urea water recovery is completed.

  The motor stop unit 35 stops the motor 21 when the determination unit 34 determines that the recovery of the urea water from the urea water passage 19 to the urea water tank 14 is completed. That is, the motor stop unit 35 controls the stop of the motor 21 when the urea water recovery is completed. Thereby, the drive of the motor 21 after urea water collection | recovery is stopped, and consumption of useless electric power is reduced. In this case, when the determination unit 34 determines that the recovery of the urea water is completed, the motor stop unit 35 immediately stops the motor 21 or stops the motor 21 after a preset set period D has elapsed.

Hereinafter, the flow of processing of the control device 30 according to the first embodiment will be described.
(Main routine)
As shown in FIG. 3, the control device 30 is mainly composed of two processes. When it is time to collect the urea water, the control device 30 determines whether or not the urea water has been collected (S11). And if control device 30 judges with recovery of urea water having been completed, it will stop stop of motor 21 (S12).

(Judgment of collection completion)
Next, the flow of the collection completion determination according to the first embodiment will be described based on FIG. 4 and using the timing chart of FIG.
The control device 30 starts collecting urea water from the urea water passage 19 to the urea water tank 14 (S101). At time T <b> 11 in FIG. 5, the control device 30 drives the urea water pump 15 by the motor 21 to recover the urea water remaining in the urea water passage 19 to the urea water tank 14. At this time, the reverse drive unit 33 drives the motor 21 in the reverse direction.

  When the motor 21 is driven in S101, the drive state acquisition unit 32 determines whether or not the motor 21 is operating stably (S102). That is, the driving state acquisition unit 32 determines whether or not the motor 21 is in a stable operating state with the rotation speed being constant as shown in FIG. The motor 21 shifts to a stable rotational state after an acceleration period from the start time T11 to the time T12. The drive state acquisition unit 32 acquires the number of rotations of the motor 21 between time T12 and time T13 in FIG. 5 and determines whether or not the motor 21 is in a stable rotation state. At this time, the motor 21 is controlled by the reverse drive unit 33 so that the torque becomes constant.

  When determining that the motor 21 is in a stable operating state (S102: Yes), the drive state acquisition unit 32 acquires the rotation speed of the motor 21 at this time as the stable rotation speed Rs (S103). On the other hand, when determining that the motor 21 is not in a stable operation state (S102: No), the drive state acquisition unit 32 returns to S102 and waits until the motor 21 enters a stable operation state.

  When the stable rotational speed Rs is acquired, the determination unit 34 sets the increased rotational speed Rt (S104). The determination unit 34 sets the increased rotation speed Rt based on the stable rotation speed Rs acquired in S103. When recovering the urea water in the urea water passage 19, the rotation speed of the motor 21 changes according to factors that change the physical properties of the urea water, such as temperature. Therefore, the stable rotation speed Rs acquired in S103 changes every time the urea water is collected. Therefore, the determination unit 34 acquires the stable rotational speed Rs every time the urea water is collected, and sets the increased rotational speed Rt based on the acquired stable rotational speed Rs. In this case, the increased rotational speed Rt is set, for example, to a value that is increased from several% to several tens of% of the stable rotational speed Rs. The increasing rate of the increased rotational speed Rt with respect to the stable rotational speed Rs can be arbitrarily set according to the configuration of the exhaust purification system 10 and the like.

  The determination part 34 will acquire rotation speed Rc of the motor 21, if the increase rotation speed Rt is set in S104 (S105). That is, the determination unit 34 acquires the latest rotation number of the motor 21 as the rotation number Rc. Then, the determination unit 34 determines whether or not the rotational speed Rc acquired in S105 is equal to or greater than the increased rotational speed Rt (S106). That is, the determination unit 34 determines whether or not the latest rotational speed Rc of the motor 21 is equal to or greater than the increased rotational speed Rt set in S104.

If the determination part 34 determines with the rotation speed Rc being more than the increase rotation speed Rt (S106: Yes), it will determine with the collection | recovery of urea water having been completed (S107). That is, when the latest rotational speed Rc of the motor 21 is equal to or greater than the increased rotational speed Rt, the determination unit 34 determines that the recovery of the urea water from the urea water passage 19 to the urea water tank 14 has been completed. When the torque of the motor 21 is controlled to be constant, the load applied to the motor 21 due to the urea water decreases according to the remaining amount of urea water in the urea water passage 19. Therefore, at the time T14 in FIG. 5 when the urea water remaining in the urea water passage 19 decreases, the rotation speed Rc of the motor 21 gradually increases. Then, at time T15 in FIG. 5 when the urea water recovery in the urea water passage 19 is completed, the rotational speed Rc of the motor 21 becomes equal to or higher than the increased rotational speed Rt. Therefore, the determination unit 34 determines that the recovery of the urea water in the urea water passage 19 has been completed at the time T15 when the rotation speed Rc of the motor 21 becomes equal to or greater than the increase rotation speed Rt. Then, the control device 30 returns to S11 of the main routine shown in FIG.
On the other hand, if the determination part 34 determines with the rotation speed Rc being less than the increase rotation speed Rt (S106: No), it will return to S105. That is, the determination unit 34 continues to monitor the rotational speed Rc of the motor 21 until the time T15 is reached from the time T13 when the rotational speed Rc is smaller than the increased rotational speed Rt.

(Motor stop control)
When the process returns to S11 of the main routine shown in FIG. 3 from the determination of the completion of urea water recovery, the motor stop unit 35 controls the stop of the motor 21. The motor 21 is stopped immediately after the completion of the recovery of the urea water in S107 or after the set period D has elapsed from the determination.
When the motor 21 is stopped immediately after the completion of the recovery of the urea water, the motor stop unit 35 determines that the recovery of the urea water is completed in S107, and returns to S11 in FIG. 3, as shown in FIG. The stop of the motor 21 is controlled (S111). As a result, the motor 21 that drives the urea water pump 15 is stopped immediately after the recovery of the urea water from the urea water passage 19 to the urea water tank 14 is completed. That is, the motor 21 is stopped at time T15 in FIG.

  On the other hand, when the motor stop unit 35 is stopped after the set period D has elapsed since the determination of the completion of the recovery of the urea water, it is determined that the recovery of the urea water is completed in S107, and the process returns to S11 in FIG. As shown in FIG. 7, the time count Tc is set to “0” (S121). That is, the motor stop unit 35 sets the time count Tc, which is the count of the timer constituting the control device 30, to “0”. And the motor stop part 35 will increment the time count Tc, if the measurement of the time count Tc is started in S121 (S122).

  When the time count Tc is incremented in S122, the motor stop unit 35 determines whether or not the time count Tc is equal to or longer than the set period D (S123). That is, the motor stop unit 35 determines whether or not the time count Tc that has started measurement in S122 has reached the set period D. When determining that the time count Tc is equal to or longer than the set period D (S123: Yes), the motor stop unit 35 controls the stop of the motor 21 (S124). On the other hand, when determining that the time count Tc is less than the set period D (S123: No), the motor stop unit 35 returns to S122 and waits until the time count Tc reaches the set period D. Thereby, the motor 21 that drives the urea water pump 15 is stopped when the urea water recovery from the urea water passage 19 to the urea water tank 14 is completed and the set period D elapses. That is, in FIG. 5, even when the rotational speed Rc of the motor 21 becomes equal to or greater than the increased rotational speed Rt at time T15, the motor 21 continues to operate from time T15 to time T16 when the set period D has elapsed. The motor 21 is stopped after the time T16 has elapsed.

  In the first embodiment described above, when the determination unit 34 is driving the motor 21 in the reverse direction by the reverse drive unit 33, the urea water is based on the drive state of the motor 21 acquired by the drive state acquisition unit 32. It is determined whether or not the recovery of the urea water from the passage 19 to the urea water tank 14 is completed. The drive state of the motor 21 that drives the urea water pump 15 varies depending on the presence or absence of urea water in the urea water passage 19. Therefore, the determination unit 34 determines whether or not the recovery of the urea water has been completed from the change in the driving state of the motor 21 acquired by the driving state acquisition unit 32. Thereby, it is determined whether or not the recovery of the urea water is completed without being influenced by the influence of the external environment such as atmospheric pressure and temperature, and the error of the detection means for detecting them. That is, the determination unit 34 determines the completion of the recovery of urea water from the driving state of the motor 21. Therefore, urea water remaining in the urea water passage 19 can be avoided, and unnecessary power consumption due to driving of the urea water pump 15 after the recovery is completed can be reduced.

  Further, in the first embodiment, when the determination unit 34 controls the torque of the motor 21 to be constant, if the rotational speed Rc of the motor 21 becomes equal to or greater than the increased rotational speed Rt, the urea water tank 14 is connected from the urea water passage 19. It is determined that the recovery of urea water is complete. When the torque of the motor 21 that drives the urea water pump 15 is controlled to be constant, the rotational speed Rc of the motor 21 changes according to the urea water remaining in the urea water passage 19. When the recovery of urea water is completed, the load applied to the motor 21 decreases, and the rotation speed Rc of the motor 21 increases. The determination unit 34 determines that the recovery of the urea water is completed when the rotation speed Rc of the motor 21 increases and becomes equal to or higher than the increase rotation speed Rt. Thereby, the determination part 34 can determine the completion of the collection | recovery of urea water based on the rotation speed Rc of the motor 21. FIG. Therefore, urea water remaining in the urea water passage 19 can be avoided.

  Furthermore, in the first embodiment, when the determination unit 34 determines that the urea water recovery is completed, the motor stop unit 35 stops the motor 21 immediately or stops the motor 21 after the set period D has elapsed. To do. When the motor 21 is stopped as soon as the determination unit 34 determines that the urea water recovery is completed, the driving of the urea water pump 15 after the urea water recovery is completed is reduced. Therefore, unnecessary power consumption can be reduced.

  Further, when the motor 21 is stopped after the set period D has elapsed after the determination unit 34 determines that the recovery of the urea water has been completed, a more reliable recovery of the urea water is promoted. That is, the urea water pump 15 is not limited to the vicinity of the urea water tank 14, and may be provided at a position away from the urea water tank 14 in the urea water passage 19. In this case, if the motor 21 is stopped immediately after the rotational speed Rc of the motor 21 becomes equal to or greater than the increased rotational speed Rt, urea water may remain in a part of the urea water passage 19. For example, when the total length of the urea water passage 19 is long or there is a branch in the urea water passage 19, all the urea water may not be collected in the urea water tank 14 when the motor 21 is stopped. Thus, by waiting until the set period D is reached after the completion of the recovery of the urea water is determined, the urea water remaining in the urea water passage 19 is reliably recovered to the urea water tank 14. In this case, the setting period D is set according to the shape of the urea water passage 19 and the like. The shape of the urea water passage 19 does not change during use of the control device 30. Therefore, the set period D is set as a value specific to the exhaust purification system 10 to which the control device 30 is applied in order to reliably recover urea water according to the characteristics of the urea water passage 19. As a result, the drive of the motor 21 that continues until the set period D elapses is necessary for the recovery of the urea water remaining in the urea water passage 19 and does not drive the motor 21 unnecessarily. Therefore, urea water remaining in the urea water passage 19 can be avoided, and unnecessary power consumption due to driving of the urea water pump 15 after the recovery is completed can be reduced.

(Second Embodiment)
A control device 30 according to the second embodiment will be described.
The configuration of the control device 30 according to the second embodiment is common to the first embodiment. In the case of the second embodiment, the determination process of the urea water recovery completion by the determination unit 34 is different.
In the case of the second embodiment, the determination unit 34 determines whether or not the recovery of urea water has been completed based on the rotation speed of the motor 21. The reverse drive unit 33 controls the torque of the motor 21 rotating in the reverse direction to be constant. At this time, the drive state acquisition unit 32 acquires the rotation speed Rc of the motor 21 rotating in the reverse direction as the drive state of the motor 21. The determination unit 34 determines that the rotation speed Rc of the motor 21 acquired by the drive state acquisition unit 32 is equal to or greater than the increase rotation speed Rt. Determine that water recovery is complete. Similar to the first embodiment, the load applied to the motor 21 is changed by the urea water remaining in the urea water passage 19. Therefore, the rotation speed Rc of the motor 21 increases when the urea water to be recovered decreases. And the determination part 34 will determine this time as the time when collection | recovery of urea water was completed, if the period when the rotation speed Rc of this motor 21 becomes more than the increase rotation speed Rt becomes the setting period Tt. This setting period Tt is arbitrarily set according to, for example, the characteristics of the motor 21.

Next, the flow of determination of the completion of collection according to the second embodiment will be described based on FIG. 8 and using the timing chart of FIG. Note that a description of processes common to the first embodiment will be omitted.
The control device 30 starts recovery of urea water from the urea water passage 19 to the urea water tank 14 (S201). At time T21 in FIG. 9, the control device 30 drives the urea water pump 15 by the motor 21 to recover the urea water remaining in the urea water passage 19 to the urea water tank 14. At this time, the reverse drive unit 33 drives the motor 21 in the reverse direction.
When the motor 21 is driven in S201, the drive state acquisition unit 32 determines whether or not the motor 21 is operating stably (S202). When determining that the motor 21 is in a stable operating state (S202: Yes), the drive state acquisition unit 32 acquires the rotation speed of the motor 21 from time T22 to time T23 in FIG. 9 as the stable rotation speed Rs (S203). . On the other hand, if the drive state acquisition part 32 determines with the motor 21 not being in the stable operation state (S202: No), it will return to S202 and will wait until the motor 21 will be in the stable operation state.

  When the determination unit 34 acquires the stable rotation speed Rs, the determination unit 34 sets the increase rotation speed Rt (S204). The determination unit 34 sets the increased rotational speed Rt based on the stable rotational speed Rs acquired in S203. Also in this case, the increased rotational speed Rt can be arbitrarily set according to the configuration of the exhaust purification system 10 and the like. The determination unit 34 sets the time count Tm to “0” when the increased rotation speed Rt is set in S204 (S205). That is, the determination unit 34 sets the time count Tm, which is the count of the timer constituting the control device 30, to “0”.

  The determination unit 34 acquires the rotation speed Rc of the motor 21 when the time count Tm is set to “0” in S205 (S206). The rotational speed Rc of the motor 21 is the latest rotational speed of the motor 21. Then, the determination unit 34 determines whether or not the rotational speed Rc acquired in S206 is equal to or greater than the increased rotational speed Rt (S207). At time T24 in FIG. 9 when the urea water remaining in the urea water passage 19 decreases, the rotational speed Rc of the motor 21 gradually increases. Then, at time T25 in FIG. 9 when the urea water recovery in the urea water passage 19 is completed, the rotational speed Rc of the motor 21 becomes equal to or higher than the increased rotational speed Rt.

  When determining that the rotational speed Rc is equal to or greater than the increased rotational speed Rt (S207: Yes), the determination unit 34 increments the time count Tm (S208). That is, the determination unit 34 starts measuring the elapsed time when the rotational speed Rc is equal to or greater than the increased rotational speed Rt. On the other hand, if the determination part 34 determines with the rotation speed Rc being less than the increase rotation speed Rt (S207: No), it will return to S205.

When the determination unit 34 increments the time count Tm in S208, the determination unit 34 determines whether or not the time count Tm is equal to or longer than the set period Tt (S209). That is, the determination unit 34 determines whether or not the time count Tm at which the measurement is started in S208 has reached the set period Tt and has reached time T26. If it determines with the time count Tm being more than the setting period Tt (S209: Yes), the determination part 34 will determine with the collection | recovery of urea water having been completed (S210). Then, the control device 30 returns to S11 of the main routine shown in FIG. When it is determined in S210 that the urea water recovery has been completed, the motor stop unit 35 immediately stops the motor 21 at time T26 or stops the motor 21 at time T27 when the set period D has elapsed.
On the other hand, if the determination unit 34 determines that the time count Tm is less than the set period Tt (S209: No), the process returns to S206. That is, the determination unit 34 continues to monitor the rotational speed Rc of the motor 21 until the time count Tm reaches the set period Tt.

  In the second embodiment, when the determination unit 34 controls the torque of the motor 21 to be constant, if the period during which the rotational speed Rc of the motor 21 is equal to or greater than the increased rotational speed Rt is equal to or greater than the set period Tt, the urea water passage It is determined that the recovery of urea water from 19 to the urea water tank 14 is completed. For example, when bubbles are included in the urea water, the load of the motor 21 varies depending on the remaining amount of the urea water in the urea water passage 19, and the rotational speed Rc of the motor 21 temporarily exceeds the increased rotational speed Rt. There is a case. In such a case, the determination unit 34 may erroneously determine completion of urea water recovery. Therefore, the determination unit 34 determines that the recovery of the urea water is completed when the period in which the rotation speed Rc of the motor 21 is equal to or greater than the increase rotation speed Rt is equal to or greater than the set period Tt. Therefore, it is possible to reliably avoid the urea water remaining in the urea water passage 19 and reduce unnecessary power consumption due to the driving of the urea water pump 15 after the recovery is completed.

(Third embodiment)
A control device 30 according to the third embodiment will be described.
The configuration of the control device 30 according to the third embodiment is common to the first embodiment. In the case of the third embodiment, the determination process of the urea water recovery completion by the determination unit 34 is different.
In the case of the third embodiment, the determination unit 34 determines whether the recovery of urea water is completed based on the current supplied to the motor 21. The reverse drive unit 33 controls the rotation speed of the motor 21 rotating in the reverse direction to be constant. At this time, the drive state acquisition unit 32 acquires the current Ic supplied to the motor 21 rotating in the reverse direction as the drive state of the motor 21. When the current Ic supplied to the motor 21 acquired by the drive state acquisition unit 32 is equal to or less than the set current value It, the determination unit 34 determines that the recovery of urea water from the urea water passage 19 to the urea water tank 14 is completed. judge. When urea water remains in the urea water passage 19, the motor 21 that rotates in the reverse direction to collect the urea water is loaded by the remaining urea water. By completing the recovery of the urea water, the load applied from the urea water to the motor 21 is reduced. Therefore, the current Ic supplied to the motor 21 whose rotational speed is controlled to be constant decreases temporarily with the completion of the recovery of the urea water. Thus, the current Ic supplied to the motor 21 changes according to the change in load caused by the remaining urea water. The determination unit 34 determines the time when the current Ic supplied to the motor 21 changes as the time when the recovery of the urea water is completed.

Next, the flow of determination of completion of collection according to the third embodiment will be described based on FIG. 10 and using the timing chart of FIG. Note that description of processing that is common to the above-described embodiment is omitted.
The control device 30 starts collecting urea water from the urea water passage 19 to the urea water tank 14 (S301). At time T31 in FIG. 11, the control device 30 drives the urea water pump 15 by the motor 21 to recover the urea water remaining in the urea water passage 19 to the urea water tank 14. At this time, the reverse drive unit 33 drives the motor 21 in the reverse direction.

  When the motor 21 is driven in S301, the drive state acquisition unit 32 determines whether or not the motor 21 is operating stably (S302). When the drive state acquisition unit 32 determines that the motor 21 is in a stable operating state (S302: Yes), the drive state acquisition unit 32 acquires the current supplied to the motor 21 from time T32 to time T33 in FIG. 11 as the stable current value Is ( S303). On the other hand, when determining that the motor 21 is not in a stable operation state (S302: No), the drive state acquisition unit 32 returns to S302 and waits until the motor 21 enters a stable operation state.

  When determining the stable current value Is, the determination unit 34 sets the set current value It (S304). The determination unit 34 sets the set current value It based on the stable current value Is acquired in S303. When recovering urea water in the urea water passage 19, the current supplied to the motor 21 changes according to factors that change the physical properties of the urea water, such as temperature. Therefore, the stable current value Is acquired in S303 changes every time the urea water is recovered. Therefore, the determination unit 34 acquires the stable current value Is every time the urea water is collected, and sets the set current value It based on the acquired stable current value Is. In this case, the set current value It is set, for example, to a value that is reduced by several tens% from several% of the stable current value Is. The decreasing rate of the set current value It with respect to the stable current value Is can be arbitrarily set according to the configuration of the exhaust purification system 10 and the like.

  The determination part 34 will acquire the electric current Ic supplied to the motor 21, if the setting electric current value It is set in S304 (S305). That is, the determination unit 34 acquires the latest current supplied to the motor 21 as the current Ic. And the determination part 34 determines whether the electric current Ic acquired by this S305 is below the setting electric current value It (S306). That is, the determination unit 34 determines whether or not the latest current Ic supplied to the motor 21 is equal to or less than the set current value It set in S304.

When determining that the current Ic is equal to or less than the set current value It (S306: Yes), the determining unit 34 determines that the recovery of the urea water is completed (S307). That is, when the latest current Ic supplied to the motor 21 is equal to or less than the set current value It, the determination unit 34 determines that the recovery of the urea water from the urea water passage 19 to the urea water tank 14 has been completed. When the rotation speed of the motor 21 is controlled to be constant, the load applied to the motor 21 due to the urea water decreases according to the remaining amount of urea water in the urea water passage 19. Therefore, at time T34 in FIG. 11 when the urea water remaining in the urea water passage 19 decreases, the current Ic supplied to the motor 21 gradually decreases. Then, at time T35 in FIG. 11 when the urea water recovery in the urea water passage 19 is completed, the current Ic supplied to the motor 21 becomes equal to or less than the set current value It. Therefore, the determination unit 34 determines that the recovery of the urea water in the urea water passage 19 has been completed at the time T35 when the current Ic supplied to the motor 21 is equal to or less than the set current value It. Then, the control device 30 returns to S11 of the main routine shown in FIG. When it is determined in S307 that the urea water recovery is completed, the motor stop unit 35 immediately stops the motor 21 at time T35 or stops the motor 21 at time T36 when the set period D has elapsed.
On the other hand, if the determination part 34 determines with the electric current Ic being larger than the setting electric current value It (S306: No), it will return to S305. That is, the determination unit 34 continues to monitor the current Ic supplied to the motor 21 until the time T35 reaches the time T35 from the time T33 when the current Ic is larger than the set current value It.

  In the third embodiment, the determination unit 34 controls the number of rotations of the motor 21 to be constant, and if the current Ic supplied to the motor 21 becomes equal to or less than the set current value It, the urea water tank 19 is connected to the urea water tank. 14 determines that the recovery of urea water to 14 has been completed. When the rotational speed of the motor 21 that drives the urea water pump 15 is controlled to be constant, the current Ic supplied to the motor 21 changes according to the amount of urea water remaining in the urea water passage 19. When the recovery of the urea water is completed, the load applied to the motor 21 decreases, and the current Ic supplied to the motor 21 decreases. The determination unit 34 determines that the recovery of the urea water is completed when the current Ic supplied to the motor 21 decreases and becomes equal to or less than the set current value It. Thereby, the determination unit 34 can determine the completion of the recovery of the urea water based on the current Ic supplied to the motor 21. Therefore, urea water remaining in the urea water passage 19 can be avoided.

(Fourth embodiment)
A control device 30 according to the fourth embodiment will be described.
The configuration of the control device 30 according to the fourth embodiment is common to the first embodiment. In the case of the fourth embodiment, the determination process of the urea water recovery completion by the determination unit 34 is different.
In the case of the fourth embodiment, the determination unit 34 determines whether or not the recovery of urea water has been completed based on the current supplied to the motor 21. The reverse drive unit 33 controls the rotation speed of the motor 21 rotating in the reverse direction to be constant. At this time, the drive state acquisition unit 32 acquires the current Ic supplied to the motor 21 rotating in the reverse direction as the drive state of the motor 21. The determination unit 34 determines that the current Ic supplied to the motor 21 acquired by the drive state acquisition unit 32 is equal to or less than the set current value It, and when this period is equal to or greater than the set period Tt, the urea water passage 19 moves to the urea water tank 14. It is determined that the urea water recovery is complete. Similar to the first embodiment, the load applied to the motor 21 is changed by the urea water remaining in the urea water passage 19. Therefore, the current Ic supplied to the motor 21 decreases as the urea water recovery is completed. When the period during which the current Ic supplied to the motor 21 is equal to or less than the set current value It becomes the set period Tt, the determination unit 34 determines this time as the time when the urea water recovery is completed. This setting period Tt is arbitrarily set according to, for example, the characteristics of the motor 21.

  Next, the flow of determination of completion of collection according to the fourth embodiment will be described based on FIG. 12 and using the timing chart of FIG. Note that description of processing that is common to the above-described embodiment is omitted.

  The control device 30 starts collecting urea water from the urea water passage 19 to the urea water tank 14 (S401). At time T <b> 41 in FIG. 13, the control device 30 drives the urea water pump 15 by the motor 21 to collect the urea water remaining in the urea water passage 19 into the urea water tank 14. At this time, the reverse drive unit 33 drives the motor 21 in the reverse direction.

  When the motor 21 is driven in S401, the drive state acquisition unit 32 determines whether the motor 21 is operating stably (S402). When determining that the motor 21 is in a stable operating state (S402: Yes), the drive state acquisition unit 32 acquires the current supplied to the motor 21 from time T42 to time T43 in FIG. 13 as a stable current value Is ( S403). On the other hand, when determining that the motor 21 is not in a stable operation state (S402: No), the drive state acquisition unit 32 returns to S402 and waits until the motor 21 enters a stable operation state.

  When determining the stable current value Is, the determination unit 34 sets the set current value It (S404). The determination unit 34 sets the set current value It based on the stable current value Is acquired in S403. Also in this case, the set current value It can be arbitrarily set according to the configuration of the exhaust purification system 10 and the like. When the setting unit 34 sets the set current value It in S404, the determination unit 34 sets the time count Tm to “0” (S405). That is, the determination unit 34 sets the time count Tm of the timer that constitutes the control device 30 to “0”.

  When the time count Tm is set to “0” in S405, the determination unit 34 acquires the current Ic supplied to the motor 21 (S406). The current Ic supplied to the motor 21 is the latest current value supplied to the motor 21. Then, the determination unit 34 determines whether or not the current Ic acquired in S406 is equal to or less than the set current value It (S407). At time T44 in FIG. 13 when the urea water remaining in the urea water passage 19 decreases, the current Ic supplied to the motor 21 gradually decreases. Then, at time T45 in FIG. 13 when the urea water recovery in the urea water passage 19 is completed, the current Ic supplied to the motor 21 becomes equal to or less than the set current value It.

  When the determination unit 34 determines that the current Ic supplied to the motor 21 is equal to or less than the set current value It (S407: Yes), the time count Tm is incremented (S408). That is, the determination unit 34 starts measuring elapsed time when the current Ic supplied to the motor 21 is equal to or less than the set current value It. On the other hand, if the determination part 34 determines with the electric current Ic supplied to the motor 21 being larger than the setting electric current value It (S407: No), it will return to S405.

When the time count Tm is incremented in S408, the determination unit 34 determines whether or not the time count Tm is equal to or longer than the set period Tt (S409). That is, the determination unit 34 determines whether or not the time count Tm at which the measurement is started in S408 has reached the set period Tt and has reached time T46. If it determines with the time count Tm being more than the setting period Tt (S409: Yes), the determination part 34 will determine with the collection | recovery of urea water having been completed (S410). Then, the control device 30 returns to S11 of the main routine shown in FIG. When it is determined in S410 that the urea water recovery is completed, the motor stop unit 35 immediately stops the motor 21 at time T46, or stops the motor 21 at time T47 when the set period D has elapsed.
On the other hand, if the determination unit 34 determines that the time count Tm is less than the set period Tt (S409: No), the process returns to S406. That is, the determination unit 34 continues to monitor the current Ic supplied to the motor 21 until the time count Tm reaches the set period Tt.

  In 4th Embodiment, when the determination part 34 is controlling the rotation speed of the motor 21 uniformly, when the period when the electric current Ic supplied to the motor 21 becomes below the setting electric current value It becomes more than the setting period Tt, It is determined that the recovery of the urea water from the urea water passage 19 to the urea water tank 14 is completed. For example, when bubbles are included in the urea water, the load of the motor 21 varies depending on the remaining amount of the urea water in the urea water passage 19, and the current Ic supplied to the motor 21 is temporarily set to the set current value It. May be: In such a case, the determination unit 34 may erroneously determine completion of urea water recovery. Therefore, the determination unit 34 determines that the recovery of the urea water is completed when the period in which the current Ic supplied to the motor 21 is equal to or less than the set current value It is equal to or greater than the set period Tt. Therefore, it is possible to reliably avoid the urea water remaining in the urea water passage 19 and reduce unnecessary power consumption due to the driving of the urea water pump 15 after the recovery is completed.

  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 drawings, 10 is an exhaust purification system, 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 passage, 21 is a motor, 30 is a control device (urea water injection control device), 32 is a drive state acquisition unit (drive state acquisition unit), 33 is a reverse drive unit (reverse drive unit), 34 is a determination unit (determination unit), and 35 is a motor stop unit. (Motor stop means) is shown.

Claims (8)

Was added to the urea water that is stored in the urea water tank (14) to the exhaust of an internal combustion engine (11), the nitrogen oxides contained in the exhaust in order to reduced with a reducing catalyst (17), exhaust passageway ( 13) provided in an injector (18) for injecting urea water, and a urea water passage (19) connecting the urea water tank (14) and the injector (18) from the urea water tank (14). A urea water injection control device (30) for controlling a urea water pump (15) for supplying urea water to the injector (18),
Drive state acquisition means (32) for acquiring a drive state of a motor (21) for driving the urea water pump (15);
Reverse drive for driving the motor (21) in the opposite direction to the supply of urea water to the injector (18) in order to recover the urea water in the urea water passage (19) to the urea water tank (14). Means (33);
When the reverse drive means (33) is driving the motor (21), the urea water passage (19) is based on the drive state of the motor (21) acquired by the drive state acquisition means (32). Determination means (34) for determining whether or not recovery of urea water from the urea water tank (14) to the urea water tank (14) is completed;
Equipped with a,
When it is determined that the motor is in a stable operating state, the driving state acquisition means acquires the driving state at this time as a stable driving state,
The determination unit sets a set value based on the stable drive state, and determines whether or not the urea water has been collected based on the drive state of the motor and the set value acquired by the drive state acquisition unit. A urea water injection control device for determining. When the rotational speed Rc when the torque of the motor (21) is controlled to be constant is equal to or higher than the increased rotational speed Rt which is the preset value, the determination means (34) The urea water injection control device according to claim 1, wherein the urea water recovery to the urea water tank (14) is determined to have been completed. In the determination means (34), the rotational speed Rc when the torque of the motor (21) is controlled to be constant is not less than the increased rotational speed Rt which is the preset setting value, and is not less than the increased rotational speed Rt. 2. The urea water injection control device according to claim 1, wherein the recovery of the urea water from the urea water passage (19) to the urea water tank (14) is determined to be completed when the predetermined period is equal to or longer than a preset setting period Tt. . When the current Ic when the rotational speed of the motor (21) is controlled to be constant is less than or equal to the preset current value It, which is the preset value, the determination means (34) The urea water injection control device according to claim 1, wherein the urea water recovery to the urea water tank (14) is determined to have been completed. The determination means (34) sets in advance a period during which the current Ic when the rotational speed of the motor (21) is controlled to be constant is less than or equal to a preset current value It and less than or equal to the preset current value It. 2. The urea water injection control device according to claim 1, wherein the urea water injection control device determines that the recovery of the urea water from the urea water passage (19) to the urea water tank (14) is completed when the set time Tt that is the set value or longer is reached. .   When the determination means (34) determines that the recovery of the urea water from the urea water passage (19) to the urea water tank (14) is completed, the motor stop means (35) that immediately stops the motor (21). The urea water injection control device according to any one of claims 1 to 5, further comprising:   If the determination means (34) determines that the recovery of the urea water from the urea water passage (19) to the urea water tank (14) has been completed, the motor (21) The urea water injection control device according to any one of claims 1 to 5, further comprising motor stop means (35) for stopping the motor. The urea water injection control apparatus according to claim 1, wherein the determination unit sets the set value every time the urea water is collected.

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