control device

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

[Technical Field]

[0001] The present invention relates to a control device for controlling a urea solution supply device that supplies an aqueous urea solution to the upstream side of a selective catalytic reduction catalyst provided in an exhaust passage of an internal combustion engine. [Background technology]

[0002] Exhaust gas emitted from internal combustion engines such as diesel engines mounted on vehicles may contain NOx (nitrogen oxides). As one type of device for purifying exhaust gas by reducing and decomposing such NOx into nitrogen, water, etc., a urea SCR (Selective Catalytic Reduction) system has been put into practical use. The urea SCR system uses a urea aqueous solution as a liquid reducing agent, and decomposes the ammonia produced by the decomposition of the urea aqueous solution, thereby decomposing NOx in the exhaust gas.

[0003] The urea SCR system includes a selective catalytic reduction catalyst disposed in an exhaust passage and a urea solution supply device for supplying a urea solution to the exhaust passage upstream of the selective catalytic reduction catalyst. The selective catalytic reduction catalyst adsorbs ammonia produced by decomposition of the urea solution and promotes the reduction reaction between NOx and ammonia in the inflowing exhaust gas. The urea solution supply device also includes a pump that pressure-feeds the urea solution stored in a storage tank and an injection valve that injects the urea solution pressure-feed by the pump, and the pump and injection valve are driven and controlled by a control device.

[0004] In a urea SCR system, when the injection valve is exposed to high temperatures, the solvent in the urea solution evaporates inside the injection valve, increasing its concentration and causing the urea solution to crystallize. For example, if the cooling function for the injection valve stops when the internal combustion engine is stopped, the urea solution inside the injection valve may be heated by the residual exhaust heat and crystallize. If the urea solution crystallizes inside the injection valve, the valve disc may become stuck and unable to operate, which may result in the injection valve being stuck in an open position (stuck open) or in a closed position (stuck closed).

[0005] Patent Document 1 describes a recovery determination unit that, when it is determined that an injection valve is stuck in an open state, determines whether the sticking in the open state has been resolved based on the output of a pump when the indicated value of the injection amount of reducing agent is set to a reference value or less. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-127960 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, if the injection valve is stuck open, an excess of urea solution is supplied into the exhaust passage, and the ammonia resulting from this urea solution cannot be adsorbed by the selective catalytic reduction catalyst, and may flow out downstream of the selective catalytic reduction catalyst. For this reason, if the injection valve is stuck open, it is necessary to stop the outflow of urea solution as soon as possible.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for a urea solution supply device that can accurately determine whether or not an injection valve is stuck open, and that can quickly stop the outflow of urea solution if the injection valve is stuck open, and that can quickly supply urea solution if the injection valve is not stuck open. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a control device for a urea solution supplying device having an injection valve that supplies urea solution to an upstream side of a selective catalytic reduction catalyst provided in an exhaust passage of an internal combustion engine, and a pump that communicates with the injection valve via a urea solution pipe, the control device including a control unit that controls operation of the injection valve and the pump, and the control unit having: a urea solution supplying unit that drives the pump in a supply mode and controls the injection valve to be driven at a first frequency in order to supply urea solution from the injection valve into the exhaust passage while the internal combustion engine is in operation; and a first urea solution recovery unit that drives the pump in a recovery mode and controls the injection valve to be driven at a second frequency in order to recover urea solution in the injection valve toward the pump when an output of the pump is equal to or greater than a threshold while the internal combustion engine is in operation. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a control device for a urea water supply device that can accurately determine whether or not an injection valve is stuck open, and if the injection valve is stuck open, can quickly stop the outflow of urea aqueous solution, and if the injection valve is not stuck open, can quickly supply urea aqueous solution. [Brief explanation of the drawings]

[0011] [Figure 1] 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 present invention is applied. [Figure 2] 2 is a block diagram showing a functional configuration of a control device according to the embodiment of the present invention; FIG. [Figure 3] 4 is a flowchart illustrating an example of a process executed by a control device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described in detail 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 modified within the scope of the present invention.

[0013] <1. Overall configuration of urea SCR system> First, a configuration example of a urea SCR system to which the control device according to this embodiment can be applied will be described. Fig. 1 is a schematic diagram showing a configuration example of a urea SCR system 1.

[0014] The urea SCR system 1 is a system for removing the urea from the exhaust passage 3 of an internal combustion engine 2, typically a diesel engine. The exhaust passage 3 is provided with a selective catalytic reduction catalyst 5 and a urea water supply device 10 for supplying a urea water solution, which is a reducing agent, into the exhaust passage 3 upstream of the selective catalytic reduction catalyst 5. 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 from 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 to the vehicle on which the internal combustion engine 2 is mounted as independent sensors, or may be arranged within the control device 80 so as to be able to measure the outside air temperature Ta and the atmospheric pressure Pa, respectively.

[0015] 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 produced by decomposition of the urea aqueous solution supplied by the urea aqueous solution supply device 10, and reduces NOx in the inflowing exhaust gas by causing it to react with the ammonia. Note that the selective reduction catalyst 5 may also have the function of a particulate filter. Furthermore, a known oxidation catalyst 7 may be provided in the exhaust passage 3 upstream of the selective reduction catalyst 5.

[0016] <2. Urea water supply device> The urea water supply device 10 injects a urea water solution into the exhaust passage 3 upstream 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 to the exhaust passage 3 upstream of the selective reduction catalyst 5 and downstream of the oxidation catalyst 7, and injects the urea water 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 a control device 80.

[0017] 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 supplies the urea water solution to the injection valve 50 through the second urea water pipe 65 (supply mode of the pump 40). The second urea water pipe 65 is connected to a return pipe 67, the other end of which is connected to the urea water tank 20. The return pipe 67 is provided with an orifice or a one-way valve (not shown) so as to increase the pressure in the second urea water pipe 65. In addition, the second urea water pipe 65 is provided with a urea water pressure sensor 95. 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 outputs a sensor signal to the control device 80.

[0018] The pump 40 may be, for example, an electromagnetically driven diaphragm pump or a gear pump. The output PumpD of the pump 40 is controlled based on a drive signal output from the 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 solution supplied to the injection valve 50 is maintained at a predetermined target value Ptgt. The pump 40 is controlled, for example, by a duty ratio. The duty ratio is set as the ratio of the energization time to the total time of a constant cycle, so that the output PumpD of the pump 40 increases as the duty ratio increases. The duty ratio of the drive signal of the pump 40 can be used as an alternative value for the output PumpD of the pump 40.

[0019] The injection valve 50 is an electromagnetically driven injection valve that has, for example, an electromagnetic solenoid and can be switched between open and closed states by controlling the flow of current. The electromagnetically driven injection valve 50 has an electromagnetic coil and is structured so that a valve element moves and opens due to magnetic force generated when current is passed through the electromagnetic coil. The injection valve 50 injects the urea aqueous solution directly into the exhaust passage 3 and is attached to the exhaust passage 3 so that its nozzle faces the inside of the exhaust passage 3.

[0020] Furthermore, the urea water supply device 10 can recover the urea water solution in the injection valve 50 in the direction of the pump 40. Because the freezing temperature of the urea water solution is at least about −11° C., the urea water solution may freeze while the internal combustion engine 2 is stopped. If the urea water solution freezes, its volume will expand, which may damage the injection valve 50 and the like. For this reason, after the internal combustion engine 2 is stopped, the control device 80 operates the pump 40 in a recovery mode, so that the urea water solution remaining in the injection valve 50 and the like is recovered in the direction of the pump 40.

[0021] For example, if the pump 40 includes a pump for pressurizing a reducing agent and a pump for recovering a reducing agent, the control device 80 drives the pump for recovering a reducing agent to recover the urea solution remaining in the injection valve 50, etc., in the direction of the pump for recovering a reducing agent. In this case, the recovery mode of the pump 40 means driving the pump for recovering a reducing agent. Furthermore, if the pump 40 is a reversible pump, the control device 80 reverses the rotation of the pump 40 to recover the urea solution remaining in the injection valve 50, etc., in the direction of the pump 40. In this case, the recovery mode of the pump 40 means rotating the pump 40 in the reverse direction. Furthermore, the pump 40 may be provided with a flow path switching valve. The control device 80 switches 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 from the second urea water pipe 65 to the first urea water pipe 60 (recovery direction connection) using the flow path switching valve, thereby reversing the flow of the urea water solution and recovering the urea water solution remaining in the injection valve 50, etc., toward the pump 40. In this case, the recovery mode of the pump 40 means that the flow path switching valve is in the recovery direction connection and the pump 40 is rotated in the forward direction.

[0022] <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 the portion of the configuration of the control device 80 that is related to this embodiment.

[0023] A part or all of the control device 80 may be configured, for example, by a microcomputer or a microprocessor unit, or may be configured with updatable firmware, etc. Also, a part or all of the control device 80 may be configured with a CPU (Central Processing Unit). The control device 80 may be, for example, a single device or may be divided into multiple devices.

[0024] As shown in FIG. 2, the control device 80 includes, for example, an acquisition unit 82 and a control unit 84.

[0025] The acquisition unit 82 acquires information from each device of the vehicle equipped with the internal combustion engine 2 and outputs the information to the 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, etc. When the target injection amount DVtgt of the urea water solution is calculated by another control device, the acquisition unit 82 acquires the target injection amount DVtgt from the other control device.

[0026] The control unit 84 controls the driving of the pump 40, the injection valve 50, etc. provided in the urea water supply device 10. The control unit 84 includes a determination unit 85, a urea water supply unit 86, a first urea water recovery unit 87, a second urea water recovery unit 88, and a urea water filling unit 89.

[0027] The determination unit 85 performs various determinations. The determination results by the determination unit 85 are used in processes 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, etc.

[0028] The urea water supply unit 86 controls the pump 40 to operate in a supply mode and the injection valve 50 to operate at a first frequency f1 in order to supply the urea water solution from the injection valve 50 into the exhaust passage 3 while the internal combustion engine 2 is operating.

[0029] 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 water solution supplied to the injection valve 50 may be acquired based on a sensor signal of a urea water pressure sensor 95 attached to the second urea water pipe 65.

[0030] Furthermore, when controlling the injector 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 injector 50, to adjust the opening and closing time of the injector 50, thereby controlling the injection amount of the urea water solution to be the target injection amount DVtgt. Here, the first frequency f1, which is the frequency of the injection cycle, is 1 to 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 catalytic reduction catalyst 5, etc., or may be configured so that the control device 80 receives a value calculated by another control device.

[0031] When the internal combustion engine 2 is operating and the pump output PumpD is equal to or greater than the threshold value PumpDth, the first urea water recovery unit 87 drives the pump 40 in a recovery mode and controls the injection valve 50 to be driven at the second frequency f2 in order to recover the urea water solution in the injection valve 50 toward the pump 40.

[0032] Normally, while the internal combustion engine 2 is operating, the urea water supply unit 86 controls the supply of 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 a pump output threshold 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 recovery unit 87 starts the drive control of the pump 40 and the injection valve 50.

[0033] For example, the pump output threshold PumpDth is the upper limit of the pump output PumpD when the target injection amount DVtgt is zero. The pump output PumpD when the target injection amount DVtgt is zero is the pump output when the urea solution pumped from the pump 40 is returned to the urea solution tank 20 through the return pipe 67 while the pressure in the second urea solution pipe 65 is maintained at Ptgt. 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 configured to be determined as needed by the control device 80. Furthermore, when determining whether the pump output PumpD is equal to or greater than the threshold PumpDth, it is not necessary to directly compare the pump output PumpD with the threshold PumpDth. For example, a case in which the pump output PumpD is calculated by the control device 80 and it is determined that the pump output PumpD is greater than an expected threshold is also included in the case in which the pump output PumpD is equal to or greater than the threshold PumpDth.

[0034] When the target injection amount DVtgt is zero, if the pump output PumpD is equal to or greater than the pump output threshold PumpDth, it is possible that the urea aqueous solution is leaking somewhere in the circulation path. One of the causes of this is, for example, the injection valve 50 being stuck open.

[0035] When the pump output PumpD becomes equal to or greater than the pump output threshold PumpDth, the first urea water recovery unit 87 drives the pump 40 in recovery mode. After a first predetermined time T1 has elapsed since the pump 40 started operating in recovery mode, or after the urea water pressure Pu has dropped below a predetermined pressure, a drive signal is sent to the injector 50 to open and close at a second frequency f2. The second frequency f2 is a frequency higher than the first frequency f1 and is a frequency to which the valve element of the injector 50 can respond. For example, the second frequency f2 is 3 to 4 Hz. In this case, the duty ratio during one cycle is, for example, 50%. Gas is introduced from the opening of the injector 50, and as a result, the urea water solution remaining in the injector 50, etc. is recovered toward the pump 40.

[0036] During control of the first urea water recovery unit 87, the determination unit 85 determines whether the injector 50 is stuck open or not based on information about the current flowing through the injector 50. Specifically, the determination unit 85 determines that the injector 50 is stuck open when there is no change point in the current waveform, and determines that the injector 50 is not stuck open when there is a change point in the current waveform.

[0037] If the valve disc is not stuck, when the current is applied and the valve disc reaches the maximum lift position, a transition point appears in the current waveform where the current value drops once and then rises again.On the other hand, if the valve disc is stuck, the valve disc does not move even when current is applied, so no transition point appears in the current waveform.

[0038] Based on both the information that the output PumpD is equal to or greater than the pump output threshold PumpDth and the information that the valve disc does not move, the determining unit 85 can determine that the injection valve 50 is stuck open.

[0039] If the injection valve 50 is stuck open, the first urea water recovery unit 87 continues recovery until the recovery of the urea water is completed, and then notifies the driver that the operation of the urea water supply device 10 will be stopped, and stops the urea water supply device 10. Furthermore, the first urea water recovery unit 87 may be configured to notify the driver that it is necessary to stop the internal combustion engine 2. As another example, for example, the first urea water recovery unit 87 may be configured to instruct other control function units or control devices to notify the driver or to stop the urea water supply device 10.

[0040] If the injection valve 50 is not stuck open, the first urea water recovery unit 87 stops drive control of the pump 40 and the injection valve 50, and the urea water filling unit 89 starts drive control of the pump 40 and the injection valve 50. The urea water filling unit 89 drives the pump 40 in supply mode. When filling is complete, drive control of the pump 40 and the injection valve 50 is handed over from the urea water filling unit 89 to the urea water supply unit 86. Here, the completion of filling may be determined by calculating the time (fourth predetermined time T4) required to fill the injection valve 50 with the urea water solution before drive control of the urea water filling unit 89, and determining that filling is complete when the fourth predetermined time T4 has elapsed since the pump 40 started to be driven in the supply mode. The fourth predetermined time T4 can be set taking into account the control time of the first urea water recovery unit 87 performed previously. For example, the fourth predetermined time T4 can be set to a long time depending on the length of the control time of the first urea water recovery unit 87. This is because, when the control time of the first urea water recovery section 87 is long, the amount of recovered urea water solution is large and it is considered that it will take a long time to fill, and conversely, when the control time of the first urea water recovery section 87 is short, the amount of recovered urea water solution is small and it is considered that it will take a short time to fill. Furthermore, the completion of filling may be determined based on the urea water pressure.

[0041] In controlling the first urea water recovery unit 87, a drive signal is sent to the injector 50 to perform opening and closing operation at a second frequency f2, which is higher than the first frequency f1. By using the second frequency f2, current information can be acquired quickly, and whether the injector 50 is stuck open or not can be determined early. Furthermore, if the injector 50 is not stuck open, the injector 50 performs opening and closing operation at the second frequency f2, so that the introduction of gas from the opening of the injector 50 is intermittent, which slows down the recovery of the urea water solution. Therefore, when it is determined that the injector 50 is not stuck open, the amount of recovered urea water is small and the urea water filling time is shortened, so that the supply of the urea water solution can be resumed quickly. In the case of the stuck open state, the injector 50 does not respond to the second frequency f2 and the opening of the injector 50 remains open, so that the urea water solution can be recovered quickly regardless of the frequency.

[0042] As described above, according to the control device 80 of the urea water supply device 10 of this 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 control of the pump 40 and the injection valve 50 is taken over from the urea water supply unit 86 to the first urea water recovery unit 87, the urea water solution is recovered, and it is determined whether the injection valve 50 is stuck open.If the injection valve 50 is stuck open, the outflow of the urea water solution is stopped early, and if the injection valve 50 is not stuck open, the supply of the urea water solution can be quickly resumed.

[0043] When the internal combustion engine 2 is stopped, the second urea water recovery unit 88 controls the pump 40 to operate in a recovery mode in order to recover the urea water solution in the injection valve 50 toward the pump 40. When receiving information that the internal combustion engine 2 has stopped, the urea water supply unit 86 stops controlling the drive of the pump 40 and the injection valve 50, and instead the second urea water recovery unit 88 starts controlling the drive of the pump 40 and the injection valve 50.

[0044] The second urea water recovery unit 88 first sends a signal to the injector 50 to close it, and drives the pump 40 in recovery mode. After a second predetermined time T2 has elapsed since the start of operation in the recovery mode, or after the urea water pressure Pu has dropped below a predetermined pressure, the second urea water recovery unit 88 sends a drive signal to the injector 50 to open it. After the injector 50 opens, gas is introduced from the opening of the injector 50, and as a result, the urea water solution remaining in the injector 50, etc. is recovered toward the pump 40.

[0045] The operation and stop of the internal combustion engine 2 may be detected by a signal from an ignition switch 90, for example.

[0046] <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.

[0047] First, in step S10, 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 urea water solution is calculated by another control device, the acquisition unit 82 acquires the target injection amount DVtgt from the other control device.

[0048] In step S20, the determination unit 85 determines whether the target injection amount DVtgt is zero and whether the outside air temperature Ta acquired from the outside air temperature sensor 70, the atmospheric pressure Pa acquired from the atmospheric pressure sensor 75, and the urea water pressure Pu acquired from the urea water pressure sensor 95 are each within a predetermined range. If the target injection amount DVtgt is zero and the outside air temperature Ta, the atmospheric pressure Pa, and the urea water pressure Pu are all within the predetermined range (YES), the process proceeds to step S30. If the target injection amount DVtgt is not zero or 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.

[0049] Here, the predetermined range of the outside air temperature Ta is a temperature range suitable for the placement and operation of the urea water supplying apparatus 10, for example, not less than -10°C and not more than 80°C. The predetermined range of the atmospheric pressure Pa is a pressure range suitable for the placement and operation of the urea water supplying apparatus 10, for example, not less than 900 hPa and not more than 1030 hPa. The predetermined range of the urea water pressure Pu is, for example, a range not less than the target value Ptgt - 1000 hPa and not more than the target value Ptgt + 1000 hPa. Here, the target value Ptgt is a target value for the pressure of the urea water solution supplied to the injection valve 50, for example, 9000 hPa.

[0050] In step S30, the determination unit 85 determines whether the pump output PumpD is equal to or greater than the pump output threshold PumpDth. If the pump output PumpD is equal to or greater than 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.

[0051] In step S40, the urea water supply unit 86 stops the drive control of the pump 40 and the injection valve 50, and the first urea water recovery unit 87 starts the drive control of the pump 40 and the injection valve 50, and the process proceeds to step S50.

[0052] In step S50, the acquisition unit 82 acquires information about the current flowing through the injector 50, and the process proceeds to step S60. The acquisition unit 82 acquires information about the current flowing through the injector 50 from the drive circuit of the injector 50 or the like. Here, the current information is time-series data about the current value flowing through the injector 50 when a step-like voltage signal is applied to the injector 50 so that it opens and closes at the second frequency f2. Furthermore, if the time-series data about the current value is plotted as a graph with a time axis and a current value axis, the current information is represented as a current waveform.

[0053] In step S60, the determination unit 85 determines whether the injector 50 is stuck open or not based on information about the current flowing through the injector 50. Specifically, the determination unit 85 determines that the injector 50 is stuck open if there is no change point in the current waveform, and determines that the injector 50 is not stuck open if there is a change point in the current waveform. If the injector 50 is stuck open (YES), the process proceeds to step S70, and if the injector 50 is not stuck open (NO), the process proceeds to step S100.

[0054] In step S70, the determination unit 85 determines whether or not the recovery of the urea aqueous solution has finished. If the recovery has finished (YES), the process proceeds to step S80, and if the recovery has not finished (NO), the process returns to the determination in step S70. The completion of recovery may also be determined based on whether or not a third predetermined time T3 has elapsed. For example, it may be determined that recovery has finished when the third predetermined time T3 has elapsed since the pump 40 started to be driven in the recovery mode, and that recovery has not finished when the third predetermined time T3 has not elapsed.

[0055] In step S80, the first urea water recovery unit 87 notifies the driver that the operation of the urea water supply device 10 will be stopped, and stops the urea water supply device 10. Furthermore, the first urea water recovery unit 87 may be configured to notify the driver that the internal combustion engine 2 needs to be stopped. As another example, in step S80, the first urea water recovery unit 87 may be configured to instruct other control function units to notify the driver or to stop the urea water supply device 10. After step S80, this flow ends.

[0056] In step S100, the first urea water recovery unit 87 stops the drive control of the pump 40 and the injection valve 50, and the urea water filling unit 89 starts the drive control of the pump 40.

[0057] In step S110, the determination unit 85 determines whether the urea water filling unit 89 has completed filling with the urea water solution. If the filling has completed (YES), the process proceeds to step S120. If the filling has not completed (NO), the process returns to the determination in step S110. The completion of filling may be determined based on time. For example, before the urea water filling unit 89 performs drive control, the time required for filling the injection valve 50 with the urea water solution from the start of drive of the pump 40 (a fourth predetermined time T4) is calculated. The filling may be determined to be completed when the fourth predetermined time T4 has elapsed since the pump 40 started to be driven in the supply mode, and may be determined to be incomplete when the fourth predetermined time T4 has not elapsed. The fourth predetermined time T4 may be set taking into consideration the control time of the first urea water recovery unit 87 performed previously. For example, the longer the control time of the first urea water recovery unit 87, the longer the fourth predetermined time T4 may be set. This is because, when the control time of the first urea water recovery section 87 is long, the amount of recovered urea water solution is large and it is considered that filling will take a long time, and conversely, when the control time of the first urea water recovery section 87 is short, the amount of recovered urea water solution is small and it is considered that filling will take a short time. Furthermore, the completion of filling may be determined based on the urea water pressure.

[0058] In step S120, the urea water filling unit 89 stops controlling the drive of the pump 40 and the injection valve 50, and instead the urea water supply unit 86 starts controlling the drive of the pump 40 and the injection valve 50, and the process returns to step S10.

[0059] As described above, according to the process executed by the control device 80 of the urea water supplying device 10 of this 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 drive control of the pump 40 and the injection valve 50 is taken over from the urea water supplying unit 86 to the first urea water recovery unit 87, and the urea water solution is recovered. Furthermore, since it is determined whether the injection valve 50 is stuck open, if the injection valve 50 is stuck open, the outflow of the urea water solution can be stopped early. Furthermore, if the injection valve 50 is not stuck open, the supply of the urea water solution can be quickly resumed. [Explanation of symbols]

[0060] 1 Urea SCR system, 2 Internal combustion engine, 3 Exhaust passage, 5 Selective catalytic reduction catalyst, 7 Oxidation catalyst, 10 Urea water supply device, 20 Urea water tank, 40 Pump, 50 Injector, 60 First Urea water piping, 65 Second Urea water piping, 67 Return piping, 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 Second Urea water recovery unit, 89 Urea water filling unit, 90 Ignition switch, 95 Urea water pressure sensor.

Claims

1. A control device (80) for a urea water supply device (10) including an injection valve (50) for supplying a urea water solution to the upstream side of a selective catalytic reduction catalyst (5) provided in an exhaust passage (3) of an internal combustion engine (2), and a pump (40) communicating with the injection valve (50) via a urea water pipe (65), The control device (80) includes a control unit (84) that controls the operation of the injection valve (50) and the pump (40); The control unit (84) a urea water supply unit (86) that controls the pump (40) to be driven in a supply mode and the injection valve (50) to be driven at a first frequency (f1) in order to supply the urea water solution from the injection valve (50) into the exhaust passage (3) during operation of the internal combustion engine (2); a first urea water recovery unit (87) that controls the drive of the injection valve (50) and the pump (40) in place of the urea water supply unit (86) when the internal combustion engine (2) is in operation and an output (PumpD) of the pump (40) is equal to or greater than a threshold value (PumpDth), and controls the pump (40) to be driven in a recovery mode and the injection valve (50) to be driven at a second frequency (f2); a determination unit (85) that determines whether or not the injection valve (50) is stuck open based on information about a current flowing through the injection valve (50) when the first urea water recovery unit (87) drives the injection valve (50) at the second frequency (f2); and When the determination unit (85) determines that the stuck-open state is not present, the first urea water recovery unit (87) stops controlling the drive of each of the pump (40) and the injection valve (50), The control unit (84) a urea water filling unit (89) that drives the pump (40) in the supply mode to supply the urea water solution to the injection valve (50) through the urea water pipe (65) after the first urea water recovery unit (87) stops drive control of the pump (40) and the injection valve (50) when the injection valve (50) is not stuck open, When the urea water filling unit (89) fills the urea water from the urea water pipe (65) to the injection valve (50) with the urea water solution, the urea water supply unit (86) resumes control of the drive of each of the pump (40) and the injection valve (50). Control device.

2. The control unit (84) determines that the urea aqueous solution has been filled from the urea aqueous solution piping (65) to the injection valve (50) when a fourth predetermined time (T4) has elapsed since the urea aqueous solution filling unit (89) started to drive the pump (40) in the supply mode, The control device according to claim 1, wherein the fourth predetermined time (T4) is set based on a control time of the first urea water recovery section (87).

3. The second frequency is higher than the first frequency. The control device according to claim 1 or 2.

4. The control unit (84) The system further includes a second urea water recovery unit (88) that controls the pump (40) to operate in a recovery mode in order to recover the urea water solution in the injection valve (50) toward the pump (40) when the internal combustion engine (2) is stopped. The control device according to claim 1 or 2.

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