JP2022110637A - Controller - Google Patents

Abstract

To provide a controller of a urea water supply device capable of preventing a urea water solution from outflowing in an early stage to minimize generation of ammonia when an injection valve is openly fixed, and capable of supplying the urea water solution quickly when the injection valve is not openly fixed.SOLUTION: A control unit of a controller has a first urea water recovery unit (87) that when an internal combustion engine (2) is running and an output (PumpD) of a pump (40) is equal to or larger than a threshold (PumpDth), controls the driving of an injection valve (50) and the pump (40) instead of a urea water supply unit (86), drives the pump (40) in recovery mode, and drives the injection valve (50) at a second frequency (f2).SELECTED DRAWING: Figure 3

Description

The present invention relates to a control device for controlling an aqueous urea supply device that supplies an aqueous urea solution upstream of a selective reduction catalyst provided in an exhaust passage of an internal combustion engine.

NOx (nitrogen oxides) may be contained in exhaust gas discharged from an internal combustion engine such as a diesel engine mounted on a vehicle. A urea SCR (Selective Catalytic Reduction) system has been put into practical use as one aspect of a device for purifying exhaust gas by reducing such NOx and decomposing it into nitrogen, water, and the like. The urea SCR system is a system that uses an aqueous urea solution as a liquid reducing agent, and decomposes NOx by reacting NOx in exhaust gas with ammonia produced by decomposition of the aqueous urea solution.

The urea SCR system includes a selective reduction catalyst arranged in an exhaust passage, and a urea water supply device for supplying an aqueous urea solution to the exhaust passage on the upstream side of the selective reduction catalyst. The selective reduction catalyst has a function of adsorbing ammonia generated by decomposition of the aqueous urea solution and promoting a reduction reaction between NOx and ammonia in the inflowing exhaust gas. The urea water supply device includes a pump for pumping the urea aqueous solution contained in the storage tank, and an injection valve for injecting the urea aqueous solution pressure-fed by the pump, and the pump and the injection valve are driven and controlled by a control device. be done.

In the urea SCR system, when the injection valve is exposed to high temperatures, the solvent of the urea aqueous solution evaporates within the injection valve, increasing the concentration and possibly causing the urea aqueous solution to crystallize. For example, if the cooling function for the injection valve stops when the internal combustion engine is stopped, the urea aqueous solution in the injection valve may be heated and crystallized under the influence of the residual exhaust heat. When the urea aqueous solution crystallizes in the injection valve, the valve body becomes stuck in an unoperable state, and the injection valve may become stuck open or stuck when the valve is closed.

In Patent Document 1, when it is determined that the injection valve is stuck in the open state, the injection valve is opened based on the output of the pump in a state in which the indicated value of the injection amount of the reducing agent is set to a reference value or less. A recovery determination unit that determines whether or not the sticking in the valve state has been resolved is described.

JP 2018-127960 A

Here, when the injection valve is in a stuck open state, an excessive urea aqueous solution is supplied into the exhaust passage, and the ammonia caused by this urea aqueous solution cannot be adsorbed by the selective reduction catalyst, and is downstream of the selective reduction catalyst. may leak into Therefore, when the injection valve is stuck open, it is necessary to stop the outflow of the aqueous urea solution at an early stage.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to accurately determine whether or not an injection valve is stuck open, and to detect a urea aqueous solution when the injection valve is stuck open. To provide a control device for an aqueous urea supply device capable of quickly stopping the outflow of urea and rapidly supplying an aqueous urea solution when an injection valve is not stuck open.

According to one aspect of the present invention, an injection valve that supplies an aqueous urea solution to the upstream side of a selective reduction catalyst provided in an exhaust passage of an internal combustion engine, and a pump that communicates with the injection valve via an aqueous urea pipe. , wherein the control device includes a control section that controls driving of the injection valve and the pump, and the control section controls the injection valve to the a urea water supply section for controlling the pump to be driven in a supply mode and the injection valve to be driven at a first frequency to supply the urea aqueous solution into the exhaust passage; and the internal combustion engine being in operation, When the output of the pump is equal to or greater than a threshold, the pump is driven in a recovery mode and the injection valve is controlled to be driven at a second frequency in order to collect the aqueous urea solution in the injection valve in the direction of the pump. and a first aqueous urea recovery unit.

According to the present invention, it is possible to accurately determine whether or not the injection valve is stuck open, and when the injection valve is stuck open, the outflow of the aqueous urea solution is stopped early, and when the injection valve is not stuck open. , it is possible to provide a control device for an aqueous urea supply device capable of rapidly supplying an aqueous urea solution.

1 is a diagram showing an example of the overall configuration of a urea SCR system to which a control device according to an embodiment of the invention is applied; FIG. 3 is a block diagram showing the functional configuration of the control device according to the embodiment of the invention; FIG. 4 is a flow chart showing an example of processing executed by the control device according to the embodiment of the present invention;

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. However, this embodiment shows one aspect of the present invention, does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

<1. Overall configuration of urea SCR system>
First, a configuration example of a urea SCR system to which the control device according to the present embodiment can be applied will be described. FIG. 1 is a schematic diagram showing a configuration example of a urea SCR system 1. As shown in FIG.

The urea SCR system 1 includes a selective reduction catalyst 5 provided in the middle of an exhaust passage 3 of an internal combustion engine 2 represented by a diesel engine, and a reducing agent in the exhaust passage 3 on the upstream side of the selective reduction catalyst 5. and a urea water supply device 10 for supplying the urea water solution. A urea water pressure sensor 95 is provided in a second urea water pipe 65 of the urea water supply device 10, which will be described later. A sensor signal of the urea water pressure sensor 95 is transmitted to the control device 80 . In addition, signals from an outside air temperature sensor 70 , an atmospheric pressure sensor 75 and an ignition switch 90 are input to the control device 80 . The outside air temperature sensor 70 and the atmospheric pressure sensor 75 may be attached as independent sensors to the vehicle in which the internal combustion engine 2 is mounted, or may be arranged in the control device 80 so as to measure the outside air temperature Ta and the atmospheric pressure Pa, respectively. It's okay to be there.

The selective reduction catalyst 5 selectively reduces NOx contained in the exhaust gas of the internal combustion engine 2 . Specifically, the selective reduction catalyst 5 adsorbs ammonia generated by decomposition of the urea aqueous solution supplied by the urea water supply device 10, and reduces NOx in the inflowing exhaust gas by reacting it with ammonia. . The selective reduction catalyst 5 may also have the function of a particulate filter. Further, a known oxidation catalyst 7 may be provided in the exhaust passage 3 on the upstream side of the selective reduction catalyst 5 .

<2. Aqueous urea supply device>
The urea water supply device 10 injects the urea water solution into the exhaust passage 3 on the upstream side of the selective reduction catalyst 5 . The urea water supply device 10 includes a pump 40 and an injection valve 50 . The injection valve 50 is fixed in the exhaust passage 3 upstream of the selective reduction catalyst 5 and downstream of the oxidation catalyst 7 , and injects the urea aqueous solution pressure-fed from the pump 40 into the exhaust passage 3 . The pump 40 and the injection valve 50 are driven and controlled by the control device 80 .

When the urea water supply device 10 supplies the urea water solution into the exhaust passage 3, the pump 40 sucks up the urea water solution through the first urea water pipe 60 and sprays the urea water solution through the second urea water pipe 65. 50 (supply mode of pump 40). A return pipe 67 having the other end connected to the urea water tank 20 is connected to the second urea water pipe 65 . The return pipe 67 is provided with an orifice or a one-way valve (not shown) so that the pressure inside the second urea water pipe 65 is increased. A urea water pressure sensor 95 is provided in the second urea water pipe 65 . The urea water pressure sensor 95 is a sensor that detects the pressure Pu of the urea water solution supplied to the injection valve 50 , and the sensor signal is output to the control device 80 .

As the pump 40, for example, an electromagnetically driven diaphragm pump or gear pump is used. The output PumpD of pump 40 is controlled based on the drive signal output from control device 80 . For example, in the supply mode of the pump 40, the control device 80 controls the output PumpD of the pump 40 so that the pressure Pu of the urea aqueous solution supplied to the injection valve 50 is maintained at a predetermined target value Ptgt. The pump 40 is controlled by, for example, a duty ratio. Since the duty ratio is set as the ratio of the energization time to the total time of the constant cycle, the output PumpD of the pump 40 increases as the duty ratio increases. As an alternative value for the output PumpD of pump 40, the duty ratio of the driving signal of pump 40 can be used.

The injection valve 50 is provided with, for example, an electromagnetic solenoid, and an electromagnetically driven injection valve that can be switched between opening and closing by energization control is used. The electromagnetically driven injection valve 50 has an electromagnetic coil, and has a structure in which the valve body is moved by a magnetic force generated by energizing the electromagnetic coil to open the valve. The injection valve 50 directly injects the aqueous urea solution into the exhaust passage 3 and is attached to the exhaust passage 3 so that the injection hole faces the inside of the exhaust passage 3 .

Further, the urea water supply device 10 can recover the urea water solution in the injection valve 50 toward the pump 40 . Since the freezing temperature of the urea aqueous solution is about −11° C. at the lowest, the urea aqueous solution may freeze while the internal combustion engine 2 is stopped. When the urea aqueous solution freezes, its volume expands, which may damage the injection valve 50 and the like. Therefore, after the internal combustion engine 2 is stopped, the control device 80 operates the pump 40 in the recovery mode, whereby the urea aqueous solution remaining in the injection valve 50 and the like is recovered in the direction of the pump 40 .

For example, when the pump 40 includes a reducing agent pumping pump and a reducing agent recovery pump, the control device 80 drives the reducing agent recovery pump to remove the urea aqueous solution remaining in the injection valve 50 and the like for reducing agent recovery. Collect in the direction of the pump. In this case, the recovery mode of the pump 40 is to drive the reducing agent recovery pump. If the pump 40 is a reverse-rotatable pump, the control device 80 reversely rotates the pump 40 to recover the urea aqueous solution remaining in the injection valve 50 and the like toward the pump 40 . In this case, the recovery mode of the pump 40 is to rotate the pump 40 in reverse. Also, the pump 40 may be provided with a channel switching valve. The controller 80 uses the flow path switching valve to change the connection destination of the suction port of the pump 40 from the first urea water pipe 60 to the second urea water pipe 65, and the connection destination of the discharge port of the pump 40 to the second urea water pipe. By switching from 65 to the first urea water pipe 60 (recovery direction connection), the flow of the urea aqueous solution is reversed, and the urea aqueous solution remaining in the injection valve 50 and the like is recovered in the direction of the pump 40 . In this case, the recovery mode of the pump 40 means that the channel switching valve is connected in the recovery direction and the pump 40 is rotated in the forward direction.

<3. Control device>
Next, a configuration example of the control device 80 of the urea water supply device 10 according to this embodiment will be described. FIG. 2 is a block diagram showing the functional configuration of a portion of the configuration of the control device 80 that is related to this embodiment.

A part or all of the control device 80 may be configured by, for example, a microcomputer or a microprocessor unit, or may be configured by an updatable device such as firmware. In addition, part or all of the control device 80 is a CPU (Central Processing
It may be a program module or the like that is executed by a command from a Unit) or the like. For example, one controller 80 may be provided, or a plurality of controllers may be provided.

The control device 80 includes, for example, an acquisition unit 82 and a control unit 84, as shown in FIG.

Acquisition unit 82 acquires information from each device of the vehicle in which internal combustion engine 2 is mounted, and outputs the information to control unit 84 . For example, the acquisition unit 82 acquires information from the outside air temperature sensor 70, the atmospheric pressure sensor 75, the ignition switch 90, the urea water pressure sensor 95, and the like. When the target injection amount DVtgt of the aqueous urea solution is calculated by another control device, the acquisition unit 82 acquires the target injection amount DVtgt from the other control device.

The control unit 84 controls driving of the pump 40, the injection valve 50, and the like provided in the urea water supply device 10. FIG. Control unit 84 includes determination unit 85 , urea water supply unit 86 , first urea water recovery unit 87 , second urea water recovery unit 88 , and urea water filling unit 89 .

The determination unit 85 makes various determinations. The determination result by the determination unit 85 is used for processing performed by the urea water supply unit 86, the first urea water recovery unit 87, the second urea water recovery unit 88, the urea water filling unit 89, and the like.

The urea water supply unit 86 drives the pump 40 in the supply mode to supply the urea aqueous solution from the injection valve 50 into the exhaust passage 3 while the internal combustion engine 2 is running, and drives the injection valve 50 at the first frequency. Control to drive with f1.

At this time, the urea water supply unit 86 feedback-controls the output PumpD of the pump 40 so that the pressure Pu of the urea water solution supplied to the injection valve 50 becomes a predetermined target value Ptgt. The pressure Pu of the urea aqueous solution supplied to the injection valve 50 may be obtained based on the sensor signal of the urea water pressure sensor 95 attached to the second urea water pipe 65 .

Further, when controlling the injection valve 50 to be driven at the first frequency f1, the urea water supply unit 86 adjusts the duty ratio, which is the ratio of the energization time to the total time of one injection cycle of the injection valve 50. Thus, the opening/closing time of the injection valve 50 is adjusted to control the injection amount of the aqueous urea solution to the target injection amount DVtgt. Here, the first frequency f1, which is the frequency of the injection cycle, is 1-2 Hz. The target injection amount DVtgt may be calculated by the control device 80 based on the NOx in the exhaust gas, the ammonia adsorption amount of the selective reduction catalyst 5, or the like, or may be calculated by another control device. may be configured to receive

When the internal combustion engine 2 is in operation and the pump output PumpD is equal to or greater than the threshold value PumpDth, the first urea water recovery unit 87 operates to recover the urea water solution in the injection valve 50 toward the pump 40. is driven in the recovery mode, and the injection valve 50 is controlled to be driven at the second frequency f2.

Normally, during operation of the internal combustion engine 2 , the urea water supply unit 86 is controlled to supply the urea water solution from the injection valve 50 into the exhaust passage 3 . However, when the pump output PumpD becomes equal to or greater than the pump output threshold value PumpDth, the urea water supply unit 86 stops the drive control of the pump 40 and the injection valve 50, and the first urea water collection unit 87 controls the pump 40 and the injection valve 50. Drive control of the valve 50 is started.

For example, the pump output threshold PumpDth is the upper limit of the pump output PumpD when the target injection amount DVtgt is zero. When the target injection amount DVtgt is zero, the pump output PumpD is such that the urea aqueous solution pressure-fed from the pump 40 is kept at the pressure Ptgt in the second urea water pipe 65 and all passes through the return pipe 67 to the urea water tank. 20 is the pump output. Considering that the pump output threshold PumpDth changes due to changes in the performance of each component and changes in environmental conditions, the pump output threshold PumpDth may be determined by the controller 80 at any time. Further, when determining whether or not the pump output PumpD is equal to or greater than the threshold value PumpDth, it is not necessary to directly compare the pump output PumpD and the threshold value PumpDth. For example, the case where the pump output PumpD is arithmetically processed in the control device 80, and as a result, the case where it is determined that the pump output PumpD is larger than the expected threshold is also included in the case where the pump output PumpD is equal to or greater than the threshold PumpDth.

When the target injection amount DVtgt is zero, if the pump output PumpD is greater than or equal to the pump output threshold value PumpDth, it is possible that the urea aqueous solution is leaking somewhere in the circulation path. One of the causes is, for example, that the injection valve 50 is stuck open.

When the pump output PumpD becomes equal to or greater than the pump output threshold value PumpDth, the first urea water recovery unit 87 drives the pump 40 in the recovery mode. After the first predetermined time T1 has elapsed from the start of recovery mode driving of the pump 40, or after the urea water pressure Pu has decreased below the predetermined pressure, a drive signal is transmitted to the injection valve 50 so as to open and close at the second frequency f2. The second frequency f2 is a frequency higher than the first frequency f1 and a frequency to which the valve element of the injection valve 50 can respond. For example, the second frequency f2 is 3-4 Hz. The duty ratio during one cycle at this time is, for example, 50%. Gas is introduced from the opening of the injection valve 50 , and along with this, the urea aqueous solution remaining in the injection valve 50 and the like is collected in the direction of the pump 40 .

During the control of the first urea water recovery unit 87 , the determination unit 85 determines whether or not the injection valve 50 is stuck open based on the current information flowing through the injection valve 50 . Specifically, the determination unit 85 determines that the injection valve 50 is stuck open when there is no change point in the current waveform, and determines that the injection valve 50 is not stuck open when there is a change point in the current waveform. .

If the valve body is not stuck, when the valve body reaches the maximum lift position by energization, the current waveform shows a change point where the current value once decreases and then increases again. On the other hand, when the valve body is stuck, the valve body does not move even if the current is supplied, so no change point appears in the current waveform.

Based on both the information that the output PumpD is equal to or greater than the pump output threshold value PumpDth and the information that the valve body does not move, the determination unit 85 can determine that the injection valve 50 is stuck open.

When the injection valve 50 is stuck open, the first aqueous urea recovery unit 87 continues recovery until the recovery of the aqueous urea is completed, and then notifies the driver that the operation of the aqueous urea supply device 10 is to be stopped. Then, the urea water supply device 10 is stopped. Furthermore, the first urea water recovery section 87 may be configured to notify the driver that the internal combustion engine 2 needs to be stopped. As another embodiment, for example, the first urea water recovery unit 87 is configured to notify other control function units and control devices to the driver and to instruct the urea water supply device 10 to stop. may

When the injection valve 50 is not stuck open, the first aqueous urea recovery unit 87 stops driving control of the pump 40 and the injection valve 50, and the urea water filling unit 89 starts driving control of the pump 40 and the injection valve 50. . The urea water filling section 89 drives the pump 40 in supply mode. When filling is completed, drive control of the pump 40 and the injection valve 50 is handed over from the urea water filling section 89 to the urea water supply section 86 . Here, the determination of filling completion is performed by calculating the time (fourth predetermined time T4) required for filling the urea aqueous solution up to the injection valve 50 before driving control of the urea water filling unit 89, and starting driving the pump 40 in the supply mode. It may be determined that the filling is completed when the fourth predetermined time T4 has elapsed from the time when the filling is completed. The fourth predetermined time T4 can be set in consideration of the control time of the first urea water recovery section 87 performed before. For example, according to the length of the control time of the first urea water recovery section 87, the fourth predetermined time T4 can be set as a long time. When the length of the control time of the first urea water recovery unit 87 is long, the amount of the recovered urea aqueous solution is large, and it is considered that filling takes a long time. This is because it is considered that when the length of the control time of is short, the amount of the urea aqueous solution recovered is small and the charging time is short. Also, the completion of filling may be determined by the urea water pressure.

In the control of the first urea water recovery section 87, a drive signal is transmitted to the injection valve 50 so as to open and close at a second frequency f2 higher than the first frequency f1. By using the second frequency f2, current information can be acquired quickly, and it can be determined early whether or not the valve is stuck open. In addition, when the injection valve 50 is not stuck open, the injection valve 50 opens and closes at the second frequency f2, so the introduction of gas from the opening of the injection valve 50 is intermittent, and the recovery of the aqueous urea solution is slow accordingly. Become. Therefore, the amount of recovered urea water is small when it is determined that there is no open sticking, and the urea water filling time is shortened. In the case of open fixation, the injection valve 50 does not respond to the second frequency f2, and the opening of the injection valve 50 remains open, so the aqueous urea solution can be quickly recovered regardless of the frequency.

As described above, according to the control device 80 of the urea water supply device 10 of the present embodiment, when the pump output PumpD becomes equal to or greater than the threshold value PumpDth during operation of the internal combustion engine 2, the pump 40 and the injection valve 50 are controlled. The urea water solution is taken over from the urea water supply unit 86 to the first urea water recovery unit 87 to recover the aqueous urea solution, and it is determined that the injection valve 50 is stuck open. This can be stopped early, and when the injection valve 50 is not stuck open, the supply of the aqueous urea solution can be quickly restarted.

The second urea water recovery unit 88 controls the pump 40 to be driven in recovery mode in order to recover the urea aqueous solution in the injection valve 50 toward the pump 40 when the internal combustion engine 2 is stopped. When the information about the stop of the internal combustion engine 2 is obtained, the urea water supply unit 86 stops the drive control of the pump 40 and the injection valve 50, and instead the second urea water collection unit 88 controls the drive of the pump 40 and the injection valve 50. to start.

The second urea water recovery unit 88 first sends a signal to the injection valve 50 to close it, and drives the pump 40 in recovery mode. After the second predetermined time T2 has elapsed from the start of driving in the recovery mode, or after the urea water pressure Pu has decreased below the predetermined pressure, a drive signal is transmitted to the injection valve 50 so as to open it. After the injection valve 50 is opened, gas is introduced from the opening of the injection valve 50 , and the urea aqueous solution remaining in the injection valve 50 and the like is recovered in the direction of the pump 40 .

The operation or stop of the internal combustion engine 2 may be detected by a signal from the ignition switch 90, for example.

<4. Flowchart>
Next, an example of processing executed by the control device 80 of the urea water supply device 10 of this embodiment will be described with reference to FIG.

First, in step S<b>10 , the acquisition unit 82 acquires information from the outside air temperature sensor 70 , the atmospheric pressure sensor 75 and the urea water pressure sensor 95 . When the target injection amount DVtgt of the aqueous urea solution is calculated by another control device, the acquisition unit 82 acquires the target injection amount DVtgt from the other control device.

In step S20, the determination unit 85 determines whether or not the target injection amount DVtgt is zero, the outside air temperature Ta acquired from the outside air temperature sensor 70, the atmospheric pressure Pa acquired from the atmospheric pressure sensor 75, the urea water pressure sensor It is determined whether the urea water pressure Pu obtained from 95 is within a predetermined range. If the target injection amount DVtgt is zero and all of the outside air temperature Ta, the atmospheric pressure Pa, and the urea water pressure Pu are within the predetermined ranges (YES), the process proceeds to step S30. If the target injection amount DVtgt is not zero, or if any of the outside air temperature Ta, the atmospheric pressure Pa, and the urea water pressure Pu is outside the predetermined range (NO), the process returns to step S10.

Here, the predetermined range of the outside air temperature Ta is a temperature range suitable for placing and operating the urea water supply device 10, for example, -10°C or higher and 80°C or lower. The predetermined range of the atmospheric pressure Pa is a pressure range suitable for arranging and operating the urea water supply device 10, and is, for example, 900 hPa or more and 1030 hPa or less. The predetermined range of the urea water pressure Pu is, for example, the range between the target value Ptgt−1000 hPa and the target value Ptgt+1000 hPa or less. Here, the target value Ptgt is the target value of the pressure of the urea aqueous solution supplied to the injection valve 50, and is, for example, 9000 hPa.

In step S30, the determination unit 85 determines whether or not the pump output PumpD is equal to or greater than the pump output threshold value PumpDth. If the pump output PumpD is greater than or equal to the pump output threshold PumpDth (YES), the process proceeds to step S40, and if the pump output PumpD is smaller than the pump output threshold PumpDth (NO), the process returns to step S10.

In step S40, the urea water supply unit 86 stops driving control of the pump 40 and the injection valve 50, and the first urea water recovery unit 87 starts driving control of the pump 40 and the injection valve 50, and the process proceeds to step S50.

In step S50, the acquisition unit 82 acquires information on the current flowing through the injection valve 50, and the process proceeds to step S60. Acquisition unit 82 acquires current information flowing through injection valve 50 from a drive circuit of injection valve 50 or the like. Here, the current information is time-series data of current values flowing through the injection valve 50 when a stepped voltage signal is applied to the injection valve 50 so as to open and close at the second frequency f2. Further, when the time-series data of the current value is a graph having a time axis and a current value axis, the current information is represented by a current waveform.

In step S<b>60 , the determination unit 85 determines whether or not the injection valve 50 is stuck open based on the current information flowing through the injection valve 50 . Specifically, the determination unit 85 determines that the injection valve 50 is stuck open when there is no change point in the current waveform, and determines that the injection valve 50 is not stuck open when there is a change point in the current waveform. . If the injection valve 50 is stuck open (YES), the process proceeds to step S70, and if the injection valve 50 is not stuck open (NO), the process proceeds to step S100.

In step S70, the determination unit 85 determines whether or not the urea aqueous solution has been recovered. If the collection has ended (YES), the process proceeds to step S80, and if the collection has not ended (NO), the process returns to the determination of step S70. The end of collection may be determined based on whether or not the third predetermined time T3 has elapsed. For example, if the third predetermined time T3 has elapsed since the pump 40 was started to be driven in the recovery mode, it is determined that the recovery has been completed, and if the third predetermined time T3 has not elapsed, it is determined that the recovery has not been completed. can be

In step S<b>80 , the first urea water recovery unit 87 notifies the driver that the operation of the urea water supply device 10 is to be stopped, and stops the urea water supply device 10 . Furthermore, the first urea water recovery section 87 may be configured to notify the driver that the internal combustion engine 2 needs to be stopped. As another embodiment, for example, in step S80, the first urea water recovery unit 87 is configured to notify other control function units to the driver and to instruct the urea water supply device 10 to stop. may be After step S80, the flow ends.

In step S<b>100 , the first aqueous urea recovery unit 87 stops driving control of the pump 40 and the injection valve 50 , and the aqueous urea filling unit 89 starts controlling driving of the pump 40 .

In step S110, the determination unit 85 determines whether or not the urea solution filling unit 89 has completed filling the urea solution. If the filling is completed (YES), the process proceeds to step S120, and if the filling is not completed (NO), the determination returns to step S110. Completion of filling may be determined by time. For example, before drive control by the urea water filling unit 89, the time (fourth predetermined time T4) required for filling the injection valve 50 with the urea water solution from the start of driving the pump 40 is calculated. Even if it is determined that the filling is completed when the fourth predetermined time T4 has passed since the pump 40 was started to be driven in the supply mode, and it is determined that the filling is not completed when the fourth predetermined time T4 has not passed. good. The fourth predetermined time T4 can be set in consideration of the control time of the first urea water recovery section 87 performed before. For example, the longer the control time of the first urea water recovery unit 87, the longer the fourth predetermined time T4 can be set. If the length of the control time of the first urea water recovery unit 87 is long, the amount of the recovered urea aqueous solution is large, and it is thought that filling will take a long time. This is because if the length of the control time of 87 is short, the amount of the recovered urea aqueous solution is small, and it is considered that the filling can be completed in a short time. Also, the completion of filling may be determined by the urea water pressure.

In step S120, the urea water filling unit 89 stops driving control of the pump 40 and the injection valve 50, and instead, the urea water supply unit 86 starts driving control of the pump 40 and the injection valve 50, and the process returns to step S10.

As described above, according to the processing executed by the control device 80 of the urea water supply device 10 of the present embodiment, when the pump output PumpD becomes equal to or greater than the threshold value PumpDth during operation of the internal combustion engine 2, the pump 40 and the injection Drive control of the valve 50 is handed over from the aqueous urea supply unit 86 to the first aqueous urea recovery unit 87 to recover the aqueous urea solution, and it is determined that the injection valve 50 is stuck open. , the outflow of the urea aqueous solution can be stopped at an early stage. Further, when the injection valve 50 is not stuck open, the supply of the aqueous urea solution can be resumed promptly.

1 Urea SCR system, 2 Internal combustion engine, 3 Exhaust passage, 5 Selective reduction catalyst, 7 Oxidation catalyst, 10 Urea water supply device, 20 Urea water tank, 40 Pump, 50 Injection valve, 60 First urea water pipe, 65 Second 2 urea water pipes, 67 return pipe, 70 outside air temperature sensor, 75 atmospheric pressure sensor, 80 control device, 82 acquisition unit, 84 control unit, 85 determination unit, 86 urea water supply unit, 87 first urea water recovery unit, 88 2nd urea water collection part, 89 urea water filling part, 90 ignition switch, 95 urea water pressure sensor.

Claims (4)

an injection valve (50) for supplying an aqueous urea solution to the upstream side of a selective reduction catalyst (5) provided in an exhaust passage (3) of an internal combustion engine (2); 65) in a control device (80) for a urea water supply device (10) having a pump (40) communicating through
The control device (80) includes a control section (84) that controls driving of the injection valve (50) and the pump (40),
The control unit (84)
During operation of the internal combustion engine (2), the pump (40) is driven in a supply mode to supply the aqueous urea solution from the injection valve (50) into the exhaust passage (3), and the injection valve ( 50) to drive at the first frequency (f1); and
When the internal combustion engine (2) is in operation and the output (PumpD) of the pump (40) is equal to or greater than a threshold value (PumpDth), the injection valve (50) replaces the urea water supply section (86). and a first aqueous urea recovery unit ( 87) and
having
Control device. The second frequency is a frequency higher than the first frequency,
A control device according to claim 1 . The control unit (84) determines whether the injection valve (50) is stuck open based on current information flowing through the injection valve (50) when the injection valve (50) is driven at the second frequency (f2). It further has a determination unit (85) that determines whether or not
3. A control device according to claim 1 or 2. The control unit (84)
When the internal combustion engine (2) stops, the pump (40) is controlled to be driven in a recovery mode in order to recover the urea aqueous solution in the injection valve (50) toward the pump (40). Further having a second urea water recovery unit (88),
A control device according to any one of claims 1 to 3.

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