Urea water supply system

Abstract

A urea water supply system includes a first supply valve (11) for supplying urea water, a second supply valve (12) for supplying urea water, a supply passage (14) for connecting a urea water tank (13) and the first and second supply valves (11, 12), and an electronic control unit (ECU (30)). The supply passage (14) branches so as to have a first supply passage (14b) extending from a branch point (P1) to the first supply valve (11) and a second supply passage (14c) extending from the branch point (P1) to the second supply valve (12), and a volume of the first supply passage (14b) is larger than a volume of the second supply passage (14c). The ECU (30) opens the first supply valve (11) while keeping the second supply valve (12) closed to start filling of urea water to the supply passage (14), and then determines completion of filling of urea water in the first supply passage (14b) based on a urea water pressure detected by a pressure sensor (16), and closes the first supply valve (11).

Description

Technical Field

[0001] This disclosure generally relates to a urea water supply system for supplying urea water. Background Technology

[0002] In the comparative examples, selective catalytic reduction (SCR) catalysts are considered typical NOx purification catalysts, used to purify nitrogen oxides (NOx) and similar substances contained in internal combustion engine exhaust. Ammonia (NH3) and the like are supplied to the SCR catalysts as reducing agents for NOx purification. Patent Document 1 discloses a urea-water supply system in which the exhaust purification device has a supply valve for supplying urea-water upstream of each SCR catalyst (NOx catalyst) connected in parallel or series in the exhaust passage. As described in Patent Document 1, urea-water cannot be left idle in the supply passage or path; therefore, the urea-water supply system of Patent Document 1 is configured to (i) recover urea-water from the supply passage when urea-water is not supplied, and (ii) fill the supply passage with urea-water when urea-water is supplied.

[0003] In such a urea water supply system, if the volume of the supply channel to each supply valve is different, urea water supply problems may occur due to overfilling or underfilling of urea water. Therefore, in Patent Document 1, when the pump is driven, by appropriately controlling the opening time of the two supply valves, urea water supply problems caused by the volume difference of the supply channel to each supply valve can be suppressed.

[0004] Patent Document 1 (Japanese Patent No. 6222168) describes a method where, at the start of urea water filling, only the first supply valve located in the small first supply channel is opened, or the second supply valve located in the large second supply channel is opened together with the first supply valve. Then, based on the pressure value in the supply channel or the pump, the first supply channel is filled with urea water before the second supply channel, and then the first supply valve is closed.

[0005] However, when urea solution is first filled into the smaller first supply channel in this manner, air remains in the larger second supply channel. Since the volume change of air is greater than that of urea solution, if a significant amount of air remains in the second supply channel (i.e., it remains), the pressure detection accuracy will decrease. Specifically, the residual air is compressed, and the detected pressure value is lower. Therefore, the valve closing time of the first supply valve is incorrect, resulting in urea solution leakage. In particular, when the difference in volume between the first and second supply channels is large, and the filling of the larger second supply channel is performed later than that of the first supply channel, the amount of residual air increases, and its effect cannot be ignored. Summary of the Invention

[0006] The purpose of this disclosure is to provide a urea water supply system that can properly fill the supply channel with urea water.

[0007] To address the above issues, the following solutions are provided.

[0008] That is, a urea water supply system for supplying urea water is provided in the exhaust passage of an internal combustion engine, which is used in an exhaust purification device having first and second catalysts, wherein the first catalyst is a selective reduction catalyst disposed in the exhaust passage of the internal combustion engine and using ammonia to purify nitrogen oxides in the exhaust, comprising:

[0009] The first supply valve supplies urea water upstream of the first catalyst in the exhaust passage;

[0010] The second supply valve supplies urea water upstream of the second catalyst in the exhaust passage;

[0011] The supply channel is configured to connect the urea tank for storing urea solution and each of the first and second supply valves through which the urea solution flows.

[0012] A pump is used to pump urea solution from the urea tank to the supply channel.

[0013] A pressure detector is used to detect the pressure value of urea solution; and

[0014] The controller is used to perform pump drive control and opening / closing control of the first and second supply valves, as well as...

[0015] The supply channel branches on its way to the two supply valves; more specifically, it is designated as a common channel extending from the urea tank to the branch point, a first supply channel extending from the branch point to the first supply valve, and a second supply channel extending from the branch point to the second supply valve.

[0016] The volume of the first supply channel is greater than the volume of the second supply channel, and

[0017] The controller opens the first supply valve and drives the pump to pump urea solution while keeping the second supply valve closed, thereby starting to fill the supply channel with urea solution; the filling of urea solution in the first supply channel is determined by the pressure value detected by the pressure detector, and the first supply valve is closed when the filling of urea solution in the first supply channel is detected to be complete.

[0018] With the above configuration, when the first supply valve and the first supply channel are filled with urea solution, the amount of residual air in the second supply channel is reduced. In other words, filling the larger first supply channel with urea solution first helps reduce the amount of residual air in the supply channel, rather than filling the smaller second supply channel first. Therefore, the detection error of the urea solution pressure value can be reduced, and the completion status of filling the first supply channel with urea solution can be accurately determined. Thus, overfilling of the supply channel with urea solution and urea solution leakage can be prevented. Attached Figure Description

[0019] The objects, features, and advantages of this disclosure will become more apparent from the following detailed description with reference to the accompanying drawings, in which:

[0020] Figure 1 This is a schematic diagram of the exhaust purification device and the urea water supply system;

[0021] Figure 2 This is a flowchart illustrating the flow of the filling process;

[0022] Figure 3A This is a graph showing the relationship between the temperature and density of urea solution. Figure 3B This is a graph showing the relationship between urea solution temperature and threshold.

[0023] Figure 4A This is a graph showing the relationship between urea water concentration and urea water density. Figure 4B This is a graph showing the relationship between urea concentration and threshold.

[0024] Figure 5A It is a time graph showing the pump's driving state. Figure 5B This is a time graph showing the urea water pressure values. Figure 5C This is a time graph showing the opening / closing modes of the first supply valve. Figure 5D This is a time graph showing the opening / closing modes of the second supply valve. Figure 5E This is a time-varying graph showing the change in residual air volume;

[0025] Figure 6 This is a flowchart illustrating the flow of the filling process according to the second embodiment;

[0026] Figure 7 This is a graph showing the relationship between the pipe volume difference and the third threshold;

[0027] Figure 8A This is a graph showing the relationship between the temperature and viscosity of urea solution. Figure 8B This is a graph showing the relationship between urea solution temperature and the third threshold.

[0028] Figure 9A It is a time graph showing the pump's driving state. Figure 9B This is a time graph showing the urea water pressure values. Figure 9C This is a time graph showing the pressure fluctuations in urea solution. Figure 9D This is a time graph showing the opening / closing modes of the first supply valve. Figure 9E This is a time graph showing the opening / closing modes of the second supply valve. Figure 9F It is a time graph showing the changes in residual air volume. Detailed Implementation

[0029] Hereinafter, embodiments of the urea water supply system are discussed and described with reference to the accompanying drawings. In the following embodiments, the same or equivalent parts are indicated by the same reference numerals in the drawings, and reference is made to the description of these parts indicated by the same reference numerals in one embodiment.

[0030] (First embodiment, Figure 1 -5)

[0031] like Figure 1 As shown, a urea water supply system 100 for a vehicle is installed on the vehicle and applied to the vehicle's exhaust purification device 200. The vehicle includes an internal combustion engine 10 and an exhaust passage 20 for the internal combustion engine 10. The internal combustion engine 10 can be a diesel engine or a gasoline engine.

[0032] The exhaust purification device 200 includes a first selective reduction catalyst 21 that uses ammonia to purify nitrogen oxides (NOx) in the exhaust gas and a second selective reduction catalyst 22 that similarly uses ammonia to purify nitrogen oxides (NOx) in the exhaust gas. The exhaust purification device 200 is disposed in the exhaust passage 20, wherein the first catalyst 21 is disposed in series downstream of the internal combustion engine 10, and the second catalyst 22 is disposed in series downstream of the first catalyst 21.

[0033] Despite Figure 1 Although not shown in the diagram, an oxidation catalyst with an oxidation function and a filter for collecting particulate matter in the exhaust gas may be provided upstream of the first catalyst 21. Furthermore, an oxidation catalyst with an oxidation function and a filter for collecting particulate matter in the exhaust gas may be provided downstream of the first catalyst 21 and upstream of the second catalyst 22. Additionally, although not shown in the diagram... Figure 1 As shown, but an oxidation catalyst (ASC catalyst) for oxidizing ammonia sliding out from the first catalyst 21 or the second catalyst 22 may also be provided downstream of the first / second catalyst 21, 22.

[0034] The urea water supply system 100 includes a first supply valve 11 disposed upstream of a first catalyst 21 in an exhaust passage 20, and a second supply valve 12 disposed downstream of the first catalyst 21 and upstream of a second catalyst 22. Furthermore, the urea water supply system 100 includes a urea water tank 13 for storing urea water, a supply passage 14 through which urea water flows, a pump 15 for pumping urea water, and a pressure sensor 16 for detecting urea water pressure. Additionally, the urea water supply system 100 includes a urea water temperature sensor 17 and a urea water concentration sensor 18 in the urea water tank 13. Furthermore, the urea water supply system 100 includes an ECU (electronic control unit) 30 as a controller performing various controls.

[0035] The first supply valve 11 supplies urea solution, a precursor of ammonia, upstream of the first catalyst 21 in the exhaust passage 20. The urea solution supplied by the first supply valve 11 is thermally decomposed and hydrolyzed by the heat of the exhaust to generate ammonia. The ammonia flows into the first catalyst 21 and is adsorbed there, thereby causing a reduction reaction between ammonia and NOx in the exhaust, and the NOx is purified.

[0036] The second supply valve 12 supplies urea solution (a precursor to ammonia) to the upstream of the second catalyst 22 in the exhaust passage 20. The urea solution supplied by the second supply valve 12 purifies NOx as described above.

[0037] Supply channel 14 is configured to connect urea tank 13 to each of the first supply valve 11 and the second supply valve 12. Supply channel 14 branches at an intermediate point, between its two ends, into a common channel 14a extending from urea tank 13 to branch point P1, a first supply channel 14b extending from branch point P1 to the first supply valve 11, and a second supply channel 14c extending from point P1 to the second supply valve 12. The volume of the first supply channel 14b is set to be larger than the volume of the second supply channel 14c.

[0038] Pump 15 is located in common channel 14a and configured to pump urea water from urea water tank 13 and pump urea water from urea water tank 13 to supply channel 14, i.e. pressure and flow.

[0039] Pressure sensor 16 detects the pressure of the urea solution pumped from pump 15, i.e., the pressure of the urea solution in supply channel 14. Urea solution temperature sensor 17 detects the temperature of the urea solution stored in urea solution tank 13. Urea solution concentration sensor 18 detects the concentration of the urea solution stored in urea solution tank 13.

[0040] ECU 30 is an electronic control device, including a microcomputer composed of well-known components such as CPU, ROM, and RAM. ECU 30 has various functions and implements these functions by executing programs stored in ROM or other memory within ECU 30. These functions can be implemented through circuitry as hardware, or at least some of them can be implemented through software, i.e., processing executed on a computer.

[0041] For example, ECU 30 functions as a drive controller, which performs drive control of pump 15, and as an on / off controller, which performs on / off control of the first supply valve 11 and the second supply valve 12. The various functions of ECU 30 will be described later. ECU 30 is connected to pressure sensor 16, urea water temperature sensor 17, and urea water concentration sensor 18, and inputs their detection results. ECU 30 then performs various functions based on the detection results.

[0042] The urea water supply system 100 supplies urea water to the exhaust passage 20 to purify NOx contained in the exhaust gas emitted during the operation (i.e., combustion) of the internal combustion engine 10. Here, if urea water remains in the supply valves 11 and 12 and the supply passage 14 when the internal combustion engine 10 stops, the residual urea water freezes and expands in volume, potentially damaging the supply valves 11 and 12 and the supply passage. It is also conceivable that the residual urea water generates ammonia, which corrodes the supply valves 11 and 12, the supply passage 14, etc. Therefore, when the internal combustion engine 10 stops operating, the ECU 30 of the urea water supply system 100 implements suction control to draw the residual urea water in the supply valves 11 and 12 and the supply passage 14 back to the urea water tank 13. Specifically, the ECU 30 drives the pump 15 to rotate in the opposite direction when the supply valves 11 and 12 are open, to pump the urea water in the supply passage 14 back to the urea water tank 13. As a result, the interior of the supply passage 14 becomes empty, i.e., filled with air.

[0043] Furthermore, during the start-up of the internal combustion engine 10, the urea water supply system 100 implements filling control to fill urea water into the supply valves 11 and 12 and the supply channel 14. At this time, it is desirable to fill the volumes of the supply valves 11 and 12 and the supply channel 14 with urea water in an appropriate proportion. That is, if the urea water is overfilled relative to the volume or its capacity, urea water leakage will occur; if the urea water is insufficient, air will remain, resulting in a reduced injection volume and / or a decrease in pressure during injection.

[0044] Therefore, in the first embodiment, as Figure 2 The procedure shown involves performing a filling process related to filling control. See below for reference. Figure 2 A detailed description is provided. The filling process is performed by ECU 30 at a predetermined time (e.g., when the internal combustion engine 10 starts running).

[0045] When the filling process begins, ECU 30 drives pump 15 to rotate forward to pump urea solution from pump 15 to supply channel 14 (step S101). Then, ECU 30 opens the first supply valve 11 while keeping the second supply valve 12 closed (step S102). As a result, the urea solution pumped from pump 15 is filled into common channel 14a and the first supply channel 14b. At this time, because the second supply valve 12 is closed, residual air exists in the second supply channel 14c.

[0046] Next, ECU 30 receives the pressure value of the urea solution detected by pressure sensor 16 and determines whether the pressure value of the urea solution is equal to or higher than the first threshold Th1 (step S103). Note that, as Figure 3A As shown, the density of urea solution decreases as the temperature increases. Then, as the density of urea solution decreases, the flow rate of urea solution decreases, and the pressure loss in the urea solution pipeline decreases. Therefore, if the first threshold Th1 is set to a constant value, an error may occur in the determination process. Therefore, as... Figure 3B As shown, as the temperature of the urea solution increases, ECU 30 changes the first threshold Th1 to decrease it, similar to the density of the urea solution.

[0047] In addition, such as Figure 4A As shown, the density of urea solution increases proportionally to its concentration. Then, as the density of urea solution increases, the flow rate of urea solution increases, and the pressure loss in the urea solution pipeline increases. Therefore, if the first threshold Th1 is set to a constant value, an error may occur. Therefore, as... Figure 4B As shown, ECU30 changes the first threshold Th1 to make it proportional to the urea concentration.

[0048] If the determination result in step S103 is negative (no), then ECU 30 will execute step S103 again after a certain period of time. That is, ECU 30 waits until the pressure value of the urea water reaches the first threshold Th1.

[0049] On the other hand, if the determination result in step S103 is affirmative (yes), then ECU 30 closes the first supply valve 11 (step S104) and opens the second supply valve 12 (step S105). As a result, the residual air in the second supply channel 14c is discharged to the exhaust channel 20 through the second supply valve 12, and the second supply channel 14c is filled with urea water.

[0050] Next, the ECU 30 receives the pressure value of the urea solution detected by the pressure sensor 16 and determines whether the pressure value of the urea solution is greater than the second threshold Th2 (step S106). The second threshold Th2 is set to be equal to or higher than the first threshold Th1. Furthermore, similar to the first threshold Th1, the ECU 30 changes the second threshold Th2 according to the urea solution temperature and urea solution concentration.

[0051] If the determination result is negative (No), then after a certain period of time, ECU 30 executes step S106 again. That is, ECU 30 waits until the pressure value of the urea water becomes greater than the second threshold Th2. On the other hand, if the determination result in step S106 is positive (Yes), then ECU 30 closes the second supply valve 12 (step S107) and ends the filling process.

[0052] Next, refer to Figures 5A to 5E Describe the effect of the filling process. Figure 5A This is a time graph showing the driving state (forward rotation drive) of pump 15. Figure 5B This is a time graph showing the pressure values ​​of urea solution. Figure 5C This is a timeline showing the opening / closing modes of the first supply valve 11. Figure 5D This is a time graph showing the opening / closing modes of the second supply valve 12. Figure 5E This is a time-varying diagram showing the change in the amount of residual air in supply channel 14.

[0053] like Figures 5A to 5E As shown, when pump 15 is driven at time T1 and the first supply valve 11 is opened, the pressure of the urea water increases as the common channel 14a and the first supply channel 14b are filled with urea water. Then, the pressure becomes constant (after time T2). On the other hand, air is discharged from the supply channel 14 through the first supply valve 11, and the amount of residual air in the supply channel 14 decreases.

[0054] Subsequently, when the urea solution in the first supply valve 11 and the first supply channel 14b is filled (at time T3), the pressure of the urea solution gradually increases. At this time, the urea solution flows into the second supply channel 14c, simultaneously compressing the residual air in the second supply channel 14c.

[0055] When the pressure of the urea solution becomes equal to or greater than the first threshold Th1 (at time T4), the first supply valve 11 closes while the second supply valve 12 opens. As a result, urea solution flows into the second supply channel 14c, filling both the second supply valve 12 and the second supply channel 14c. At this time, the urea solution pushes residual air in the second supply channel 14c out through the second supply valve 12 from the supply channel 14c to the exhaust channel 20, reducing the amount of residual air in the supply channel 14c. The pressure of the urea solution temporarily decreases at this point.

[0056] Subsequently, when the urea solution in the second supply valve 12 and the second supply channel 14c is fully filled (at time T5), the urea solution loses its escape space, and the pressure of the urea solution increases. When the pressure of the urea solution becomes greater than the second threshold Th2 (at time T6), the second supply valve 12 closes. In this way, the filling of the supply channel 14 with urea solution is completed. At this time, urea solution is filled into the supply channel 14 while maintaining a pressure suitable for injection.

[0057] Now, as described above, at time T3, when the filling of urea solution in the first supply valve 11 and the first supply channel 14b is completed, air remains in the second supply channel 14c. When the filling of urea solution in the first supply channel 14b is completed, urea solution also flows into the second supply channel 14c. Since the second supply valve 12 is closed, the residual air in the second supply channel 14c is compressed by the urea solution flowing into it. Furthermore, since the volume of air is more likely to change (i.e., more compressible) than the volume of urea solution, if air remains, the residual air acts as an error factor, resulting in an error in the detection of the urea solution pressure value.

[0058] Here, for example, when the volume of the second supply channel 14c is larger than the volume of the first supply channel 14b, more residual air will result compared to the case where the volume of the second supply channel 14c is smaller (i.e., in the case of this embodiment), which often leads to a larger detection error. As a result, even if the first supply channel 14b is filled, the pressure value of the urea solution is easily detected as low due to the presence of residual air, i.e., lower than the actual pressure, and excessive urea solution supply may lead to urea solution leakage.

[0059] Therefore, in this embodiment, the volume of the second supply channel 14c is smaller than the volume of the first supply channel 14b. First, the first supply valve 11 is opened to fill the first supply channel 14b with urea solution. Then, the second supply valve 12 is opened, and subsequently, urea solution is filled into the second supply channel 14c. In this way, the amount of residual air can be reduced when the filling of urea solution in the first supply channel 14b is complete, and the detection error of the urea solution pressure value can be reduced when determined based on the first threshold Th1.

[0060] It is also conceivable that both the first supply valve 11 and the second supply valve 12 will be open from the start of filling. However, in this case, even if the urea solution is filled in the small second supply channel 14c, the urea solution flows into the first supply channel 14b, simultaneously expelling air from the first supply channel 14b, resulting in a very small and difficult-to-detect increase in pressure. Therefore, if the threshold for determining the urea solution pressure is set to a larger value, the urea solution may be overfilled, and leakage may occur. On the other hand, if the threshold for determining the urea solution pressure is lowered, it may be more susceptible to slight pressure fluctuations, leading to problems such as incorrect determinations due to slight blockages. Therefore, it can be said that the method of simultaneously opening the first supply valve 11 and the second supply valve 12 from the start of filling is inappropriate.

[0061] The following advantages can be obtained through the first embodiment described above.

[0062] With the second supply valve 12 remaining closed, the ECU 30 opens the first supply valve 11 and drives the pump 15 to pump urea solution, beginning to fill the supply channel 14 with urea solution. Subsequently, the ECU 30 determines that urea solution has filled the first supply channel 14b based on the pressure value detected by the pressure sensor 16, and then closes the first supply valve 11.

[0063] As a result, when the urea solution in the first supply valve 11 and the first supply channel 14b is fully filled, the amount of air remaining in the second supply channel 14c at time T3 will be reduced. In other words, compared to filling the smaller second supply channel 14c with urea solution first, as shown in this embodiment, filling the larger first supply channel 14b with urea solution first can more effectively reduce the amount of air remaining in the supply channel 14. Therefore, the detection error of the urea solution pressure value can be reduced, and the completion of filling the first supply channel 14b with urea solution can be accurately determined. Therefore, overfilling of the supply channel with urea solution and urea solution leakage can be prevented.

[0064] ECU 30 closes the first supply valve 11 and opens the second supply valve 12 substantially simultaneously, beginning to fill the second supply channel 14c with urea solution. Therefore, compared to the case where the second supply valve 12 is opened after a predetermined time has elapsed since the first supply valve 11 was closed, the time from the start of filling to the completion of filling (the time related to the filling process) can be shortened.

[0065] After opening the first supply valve 11, ECU 30 closes the first supply valve 11 when the pressure of the urea solution is equal to or higher than the first threshold Th1. After opening the second supply valve 12, ECU 30 closes the second supply valve 12 when the pressure of the urea solution is greater than the second threshold Th2. Furthermore, the second threshold Th2 is equal to or higher than the first threshold Th1. Therefore, the completion of filling of the first supply channel 14b and the second supply channel 14c can be appropriately determined.

[0066] The first threshold Th1 and the second threshold Th2 are adjusted based on the temperature and concentration of the urea solution. Therefore, even if the temperature or concentration of the urea solution changes, the completion status of the filling can be appropriately determined.

[0067] (Second embodiment, Figure 6 )

[0068] The urea water supply system 100 of the first embodiment may be partially modified. The urea water supply system 100 of the second embodiment is described below. In the second embodiment, its basic configuration is described based on the first embodiment.

[0069] refer to Figure 6 The filling process in the second embodiment is described. The filling process is performed by the ECU 30 at a predetermined time (e.g., when the internal combustion engine 10 starts running). When the filling process begins, the ECU 30 performs steps S101 to S104 as in the first embodiment.

[0070] After executing step S104, ECU 30 determines whether the time elapsed since the first supply valve 11 was closed is equal to or greater than a third threshold Th3 corresponding to a predetermined time (step S201). If the determination result is negative (no in S201), ECU 30 executes step S201 again after a certain period of time. That is, ECU 30 waits until a predetermined time has elapsed since the first supply valve 11 was closed.

[0071] Taking into account the volume difference between the first supply channel 14b and the second supply channel 14c and the viscosity of the urea water, the third threshold Th3 is set as the duration for which urea water flowing into the second supply channel 14c is allowed to reach the second supply valve 12 after the first supply valve 11 is closed.

[0072] More specifically, the value of the third threshold Th3 is set based on the volume difference between the first supply channel 14b and the second supply channel 14c. That is, as... Figure 7 As shown, the volume difference ( Figure 7The larger the volume difference in the pipes (the larger the volume difference in the pipes), the smaller the set third threshold Th3. This configuration is based on the consideration that the larger the volume of the first supply channel 14b, the longer it takes to fill the first supply channel 14b with urea water, and during this period, some urea water easily flows into the second supply channel 14c. Furthermore, this configuration is based on the consideration that the smaller the volume of the second supply channel 14c, the shorter the time required for the urea water flowing into the second supply channel 14c to reach the second supply valve 12 after the first supply valve 11 is closed. Based on this consideration, such as... Figure 7 As shown, the larger the volume difference, the smaller the set third threshold Th3.

[0073] In addition, such as Figure 8A As shown, the viscosity of urea solution decreases inversely with its temperature. That is, the lower the temperature of the urea solution, the higher its viscosity. Furthermore, it is known that (a) urea solution flows easily when its temperature is high and its viscosity is low, while (b) urea solution flows poorly when its temperature is low and its viscosity is high. Therefore, it may be desirable to adjust the third threshold Th3 according to the temperature of the urea solution.

[0074] Specifically, as the temperature of the urea solution decreases, it is desirable to change the third threshold Th3 to a larger value, and as the temperature of the urea solution increases, it is desirable to change the third threshold Th3 to a smaller value. Therefore, as... Figure 8B As shown, as the temperature of the urea solution decreases, ECU 30 changes the third threshold Th3 to have a larger value (i.e., sets a longer duration to Th3).

[0075] If the determination result in step S201 is positive (yes), then ECU 30 executes the process as after step S105 in the first embodiment.

[0076] According to the second embodiment, in addition to the effects of the first embodiment, the following effects can also be obtained.

[0077] If urea crystals that could cause blockage are present in supply channel 14, they can be dissolved by immersion in urea water. Therefore, after a predetermined time (i.e., the third threshold Th3) has elapsed since the first supply valve 11 was closed, the ECU 30 opens the second supply valve 12 and allows urea water to flow into the second supply channel 14c to begin filling the second supply channel 14c with urea water. By waiting for the predetermined time, the urea water reaches the second supply valve 12. That is, crystals present in the second supply valve 12 or the second supply channel 14c can be pre-immersed in urea water to dissolve in advance. Subsequently, by opening the second supply valve 12, urea crystals that could cause blockage can be quickly eliminated. Furthermore, by allowing urea water to reach the second supply valve 12 in advance, the opening time of the second supply valve 12 can be shortened, and the deterioration of the second supply valve 12 can be suppressed.

[0078] The third threshold Th3 (i.e., a predetermined time) is changed according to the temperature of the urea solution. In this way, urea solution can be properly introduced into the second supply valve 12 after the first supply valve 11 is closed and before the second supply valve 12 is opened (i.e., urea solution is allowed to reach the second supply valve 12).

[0079] Furthermore, a third threshold Th3 (i.e., a predetermined time) is set based on the volume difference between the first supply channel 14b and the second supply channel 14c. In this way, urea water can be appropriately introduced into the second supply valve 12 after the first supply valve 11 is closed and before the second supply valve 12 is opened (i.e., urea water is allowed to reach the second supply valve 12).

[0080] (Other embodiments)

[0081] The configuration of each of the above embodiments can be changed / modified as follows.

[0082] In the above embodiment, the valve closing time is determined by comparing the pressure value of the urea solution with thresholds Th1 and Th2. However, the valve closing time can also be determined by comparing the pressure fluctuation of the urea solution with the thresholds. This time can be determined. The pressure change of the urea solution is the change in the previous urea solution pressure value per unit time.

[0083] When implementing this modification example, refer to Figures 9A to 9F The comparison effect is described. Figure 9A and 9B and Figure 5A and 5B The attached diagram is the same. Figure 9C It is a time graph showing the change in urea water pressure fluctuations. Figures 9D to 9F respectively with Figures 5C to 5E same.

[0084] like Figures 9A to 9F As shown, when pump 15 is driven at time T1 and the first supply valve 11 is opened, the pressure fluctuation of the urea solution (i.e., pressure increase) is caused by the start of filling urea solution into the common channel 14a and the first supply channel 14b. However, since the pressure fluctuation becomes equal to or less than the first fluctuation threshold Th11, the filling of urea solution continues.

[0085] Note that the first fluctuation threshold Th11 is a threshold used to determine the amount of pressure fluctuation at the moment the first supply valve 11 closes. For the same reason as in the first embodiment, the ECU 30 changes the first fluctuation threshold Th11 based on the urea water temperature and urea water concentration. The pattern of changing the first threshold Th11 is the same as in the first embodiment.

[0086] After this (i.e., after time T2), the pressure becomes constant and the pressure fluctuation becomes zero. On the other hand, air is discharged from the supply channel 14 through the first supply valve 11, and the amount of residual air in the supply channel 14 is reduced.

[0087] Subsequently, when the filling of urea solution in the first supply valve 11 and the first supply channel 14b is completed (at time T3), the pressure fluctuation of the urea solution increases. When the pressure fluctuation of the urea solution becomes equal to or greater than the first fluctuation threshold Th11 (at time T4), the first supply valve 11 closes, while the second supply valve 12 opens. Therefore, residual air is discharged from the second supply valve 12, and urea solution flows into the second supply channel 14c, filling both the second supply valve 12 and the second supply channel 14c with urea solution.

[0088] Subsequently, when the filling of urea solution in the second supply valve 12 and the second supply channel 14c is completed (at time T5), the pressure fluctuation of the urea solution increases. When the pressure fluctuation of the urea solution becomes greater than the second fluctuation threshold Th12 (at time T6), the second supply valve 12 closes. In this way, the filling of urea solution in the supply channel 14 is completed.

[0089] Note that the second threshold Th12 is a threshold used to determine the amount of pressure fluctuation at the moment the second supply valve 12 closes. The second threshold Th12 is changed by EUC30 according to the urea water temperature and urea water concentration, for the same reason as in the first embodiment. The pattern of changing the second threshold Th12 is the same as in the first embodiment. Furthermore, the second threshold Th12 is set to a value greater than the first threshold Th11. This configuration is based on the consideration that when the urea water in the second supply channel 14c is fully filled, since there is no residual air, the amount of pressure fluctuation is expected to change significantly compared to when the urea water in the first supply channel 14b is fully filled.

[0090] Furthermore, in this alternative example, the second supply valve 12 is opened while the first supply valve 11 is closed. However, as in the second embodiment, the second supply valve 12 can be opened after a predetermined time has elapsed since the first supply valve 11 was closed (i.e., after the third threshold Th3).

[0091] By using / utilizing pressure fluctuations in this way, the effects of changes in density due to variations in urea solution temperature or concentration can be prevented, and the completion status of urea solution filling can be accurately determined. Furthermore, the effects of variations (i.e., detection errors) caused by the pressure sensor 16, which serves as a pressure detector, can be suppressed.

[0092] In the above embodiment, values ​​Th1 and Th11 change according to the urea solution temperature and urea solution concentration. However, this threshold can remain constant. Similarly, values ​​Th2 and Th12 do not need to change according to the urea solution temperature and urea solution concentration. That is, they can have fixed values. In this case, the urea solution temperature sensor 17 and the urea solution concentration sensor 18 can be omitted.

[0093] In the second embodiment described above, the third threshold Th3 is changed according to the urea water temperature. However, the third threshold Th3 does not necessarily need to be changed in this way. That is, it can have a fixed value. In this case, the urea water temperature sensor 17 can be omitted.

[0094] In the second embodiment described above, the third threshold Th3 is changed based on the volume difference between the first supply channel 14b and the second supply channel 14c. However, the third threshold Th3 need not be changed in this manner.

[0095] In the above embodiment, the first catalyst 21 and the second catalyst 22 are arranged in series. However, these two catalysts can be arranged in parallel. That is, the exhaust passage 20 from the internal combustion engine 10 can be supplied in parallel, and the first catalyst 21 and the second catalyst 22 can be arranged separately.

Claims

1. A urea water supply system provided in an exhaust passage of an internal combustion engine for supplying urea water, which is used in an exhaust purification apparatus having a first catalyst and a second catalyst, wherein the first catalyst is a selective reduction type catalyst provided in the exhaust passage of the internal combustion engine and purifies nitrogen oxides in exhaust gas using ammonia, the urea water supply system comprising: a first supply valve (11) for supplying urea water upstream of the first catalyst in the exhaust passage; a second supply valve (12) for supplying urea water upstream of the second catalyst in the exhaust passage; a urea water tank (13) for storing urea water; a supply passage (14) provided to connect the urea water tank with each of the first supply valve and the second supply valve, and through which the urea water passes; a pump (15) for pumping the urea water from the urea water tank to the supply passage; a pressure detector (16) that detects a pressure value of the urea water, and a controller (30) for performing drive control of the pump and opening / closing control of the first supply valve and the second supply valve, wherein the supply passage branches on the way to the two supply valves, and comprises: (i) a common passage (14a) extending from the urea water tank to a branching point, (ii) a first supply passage (14b) extending from the branching point to the first supply valve, and (iii) a second supply passage (14c) extending from the branching point to the second supply valve, a volume of the first supply passage is larger than a volume of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passage with the urea water, (ii) determine completion of filling the first supply passage with urea water based on the pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling with urea water in the first supply passage, wherein the controller is further configured to open the second supply valve while closing the first supply valve, so that filling of the second supply passage with urea water starts.

2. A urea water supply system provided in an exhaust passage of an internal combustion engine for supplying urea water, which is used in an exhaust purification apparatus having a first catalyst and a second catalyst, wherein the first catalyst is a selective reduction type catalyst provided in the exhaust passage of the internal combustion engine and purifies nitrogen oxides in exhaust gas using ammonia, the urea water supply system comprising: a first supply valve (11) for supplying urea water upstream of the first catalyst in the exhaust passage; a second supply valve (12) for supplying urea water upstream of the second catalyst in the exhaust passage; a urea water tank (13) for storing urea water; a supply passage (14) provided to connect the urea water tank with each of the first supply valve and the second supply valve, and through which the urea water passes; a supply passage (14) provided to connect the urea water tank with each of the first and second supply valves, through which the urea water passes; a pump (15) for pumping the urea water from the urea water tank to the supply passage; a pressure detector (16) for detecting a pressure value of the urea water, and a controller (30) for performing drive control of the pump and opening / closing control of the first and second supply valves, wherein the supply passage branches on the way to the two supply valves and includes: (i) a common passage (14a) extending from the urea water tank to a branching point, (ii) a first supply passage (14b) extending from the branching point to the first supply valve, and (iii) a second supply passage (14c) extending from the branching point to the second supply valve, the volume of the first supply passage is larger than that of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passage with the urea water, (ii) determine completion of filling the first supply passage with urea water based on the pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling with urea water in the first supply passage, wherein the controller is further configured to, after closing the first supply valve, wait for a predetermined time therefrom and then open the second supply valve to start filling the second supply passage with urea water.

3. The urea water supply system according to claim 2, wherein the predetermined time is set based at least in part on the volume difference between the first and second supply passages.

4. The urea water supply system according to claim 2 or 3, wherein the predetermined time is changed at least in part in accordance with the temperature of the urea water.

5. A urea water supply system provided in an exhaust passage of an internal combustion engine for supplying urea water, which is used in an exhaust purification device having a first catalyst and a second catalyst, wherein the first catalyst is a selective reduction type catalyst provided in the exhaust passage of the internal combustion engine and purifies nitrogen oxides in exhaust gas using ammonia, the urea water supply system includes: a first supply valve (11) for supplying urea water upstream of the first catalyst in the exhaust passage; a second supply valve (12) for supplying urea water upstream of the second catalyst in the exhaust passage; a urea water tank (13) for storing urea water; a supply passage (14) provided to connect the urea water tank with each of the first and second supply valves, through which the urea water passes; a pump (15) for pumping the urea water from the urea water tank to the supply passage; a pressure detector (16) for detecting a pressure value of the urea water, and a controller (30) for performing drive control of the pump and opening / closing control of the first and second supply valves, wherein the supply passage branches on the way to the two supply valves and includes: (i) a common passage (14a) extending from the urea water tank to a branching point, (ii) a first supply passage (14b) extending from the branching point to the first supply valve, and (iii) a second supply passage (14c) extending from the branching point to the second supply valve, the volume of the first supply passage is larger than that of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passage with the urea water, (ii) determine completion of filling the first supply passage with urea water based on the pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling with urea water in the first supply passage, wherein the controller is further configured to, after closing the first supply valve, wait for a predetermined time therefrom and then open the second supply valve to start filling the second supply passage with urea water. a controller (30) for performing drive control of the pump and opening / closing control of the first supply valve and the second supply valve, wherein the supply passage branches on the way to the two supply valves, and includes: (i) a common passage (14a) extending from the urea water tank to a branching point, (ii) a first supply passage (14b) extending from the branching point to the first supply valve, and (iii) a second supply passage (14c) extending from the branching point to the second supply valve, the volume of the first supply passage is larger than the volume of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passage with the urea water, (ii) determine completion of filling of the first supply passage with urea water based on the pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling of the first supply passage with urea water, wherein the controller is configured to close the first supply valve when the pressure value of the urea water detected by the pressure detector is equal to or higher than a first threshold value (Th1) after opening the first supply valve, the controller is configured to close the second supply valve upon determining that the pressure value of the urea water detected by the pressure detector is equal to or higher than a second threshold value after opening the second supply valve, and the second threshold value (Th2) is a value equal to or higher than the first threshold value.

6. The urea water supply system according to claim 5, wherein at least one of the first threshold value and the second threshold value is changed in accordance with a value of at least one of a temperature of urea water and a concentration of urea water.

7. A urea water supply system provided in an exhaust passage of an internal combustion engine for supplying urea water, which is used in an exhaust purification device having a first catalyst and a second catalyst, wherein the first catalyst is a selective reduction type catalyst provided in the exhaust passage of the internal combustion engine and purifies nitrogen oxides in exhaust gas using ammonia, the urea water supply system includes: a first supply valve (11) for supplying urea water upstream of the first catalyst in the exhaust passage; a second supply valve (12) for supplying urea water upstream of the second catalyst in the exhaust passage; a urea water tank (13) for storing urea water; a supply passage (14) provided to connect the urea water tank with each of the first supply valve and the second supply valve, and through which the urea water passes; a pump (15) for pumping the urea water from the urea water tank to the supply passage; a pressure detector (16) that detects a pressure value of the urea water, and a controller (30) for performing drive control of the pump and opening / closing control of the first supply valve and the second supply valve, wherein the supply passage branches on the way to the two supply valves, and includes: (i) a common passage (14a) extending from the urea water tank to a branching point, (ii) a first supply passage (14b) extending from the branching point to the first supply valve, and (iii) a second supply passage (14c) extending from the branching point to the second supply valve, the volume of the first supply passage is larger than the volume of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passage with the urea water, (ii) determine completion of filling of the first supply passage with urea water based on the pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling of the first supply passage with urea water, wherein the controller is configured to close the first supply valve when the pressure value of the urea water detected by the pressure detector is equal to or higher than a first threshold value (Th1) after opening the first supply valve, the controller is configured to close the second supply valve upon determining that the pressure value of the urea water detected by the pressure detector is equal to or higher than a second threshold value after opening the second supply valve, and the second threshold value (Th2) is a value equal to or higher than the first threshold value.

6. The urea water supply system according to claim 5, wherein at least one of the first threshold value and the second threshold value is changed in accordance with a value of at least one of a temperature of urea water and a concentration of urea water.

7. A urea water supply system provided in an exhaust passage of an internal combustion engine for supplying urea water, which is used in an exhaust purification device having a first catalyst and a second catalyst, wherein the first catalyst is a selective reduction type catalyst provided in the exhaust passage of the internal combustion engine and purifies nitrogen oxides in exhaust gas using ammonia, the urea water supply system includes: a first supply valve (11) for supplying urea water upstream of the first catalyst in the exhaust passage; a second supply valve (12) for supplying urea water upstream of the second catalyst in the exhaust passage; a urea water tank (13) for storing urea water; a supply passage (14) provided to connect the urea water tank with each of the first supply valve and the second supply valve, and through which the urea water passes; a pump (15) for pumping the urea water from the urea water tank to the supply passage; a pressure detector (16) that detects a pressure value of the urea water, and a controller (30) for performing drive control of the pump and opening / closing control of the first supply valve and the second supply valve, wherein the supply passage branches on the way to the two supply valves, and includes: (i) a common passage (14a) extending from the urea water tank to a branch point, (ii) a first supply passage (14b) extending from the branch point to the first supply valve, and (iii) a second supply passage (14c) extending from the branch point to the second supply valve, a volume of the first supply passage is greater than a volume of the second supply passage, and the controller is configured to: (i) open the first supply valve while keeping the second supply valve closed and drive the pump to pump the urea water, thereby starting to fill the supply passages with the urea water, (ii) determine completion of filling the first supply passage with urea water based on a pressure value detected by the pressure detector, and (iii) close the first supply valve upon detecting completion of filling with urea water in the first supply passage, wherein the controller is configured to close the first supply valve when the pressure fluctuation of urea water detected by the pressure detector is equal to or greater than a first fluctuation threshold (Thl l) after opening the first supply valve, the controller is configured to close the second supply valve when the pressure fluctuation of urea water detected by the pressure detector is greater than a second fluctuation threshold (Thl 2) after opening the second supply valve, and the second fluctuation threshold is a value greater than the first fluctuation threshold.

8. A controller for controlling a urea water supply system (100), wherein the urea water supply system comprises: a urea water tank (13), a pump (15), a pressure sensor (16), a branch point (Pl), a common passage (14a) between the pump and the branch point, a first supply valve (11), a first supply passage (14b) between the branch point and the first supply valve, a second supply valve (12), and a second supply passage (14c) between the branch point and the second supply valve, and wherein the controller comprises: a processor; and a non-transitory computer-readable storage medium, and wherein the controller is configured to: drive the pump; open the first supply valve while keeping the second supply valve closed; determine that the pressure is greater than or equal to a first threshold (Thl); close the first supply valve; open the second supply valve; determine that the pressure is greater than or equal to a second threshold (Th2); and close the second supply valve, wherein: a volume of the first supply passage is greater than a volume of the second supply passage, and the second threshold is greater than the first threshold.

9. The controller of claim 8, wherein: the first threshold varies based at least in part on a urea water temperature such that the first threshold decreases as the urea water temperature increases, and the second threshold varies based at least in part on the urea water temperature such that the second threshold decreases as the urea water temperature increases.

10. The controller of claim 8, wherein: the first threshold varies based at least in part on a urea water concentration such that the first threshold increases as the urea water concentration increases, and the second threshold varies based at least in part on the urea water concentration such that the second threshold increases as the urea water concentration increases.

11. The controller of claim 8, wherein: the first supply valve closes substantially at the same time the second supply valve opens.

12. The controller of claim 8, wherein: the second supply valve opens substantially after the first supply valve closes.

13. The controller of claim 8, wherein the controller is further configured to: determine that an elapsed time since the first supply valve closed has been greater than or equal to a time threshold (Th3); open the second supply valve; determine that the pressure is greater than or equal to a second threshold (Th2); and close the second supply valve.

14. The controller of claim 13, wherein: the time threshold is based at least in part on a pipe volume difference, such that the time threshold decreases as the pipe volume difference increases.

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