Reducing agent supply device and control method for the same

Abstract

To provide a reducing agent supply device that can highly frequently check leakage in a pressure-feeding path and can check the leakage without interrupting purification of exhaust gas.SOLUTION: A reducing agent supply device 20 includes: a reducing agent injection valve 25 mounted to an upstream side of a reduction catalyst 13 provided in an exhaust pipe 11 of an internal combustion engine 1; a pump 31 for pressure-feeding a reducing agent to the reducing agent injection valve 25; a reducing agent supply passage 52 that connects the pump and the reducing agent injection valve; and a control device 100 that controls the pump and the reducing agent injection valve. In the reducing agent supply device, when detecting that an ignition switch of the internal combustion engine has been turned off, the control device determines whether or not there is leakage of the reducing agent in a pressure-feeding path including the pump, the reducing agent injection valve, and the reducing agent supply passage and then recovers the reducing agent.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reducing agent supply device for supplying a reducing agent to an exhaust pipe of an internal combustion engine and a control method thereof. [Background technology]

[0002] Exhaust gas discharged from internal combustion engines such as diesel engines contains nitrogen oxides (hereinafter referred to as "NOx") that may have an adverse effect on the environment. A known exhaust gas purification device used to purify this NOx is one that injects a reducing agent such as a urea solution upstream of a catalyst disposed in an exhaust pipe, and reduces the NOx in the exhaust gas in the catalyst.

[0003] One example of a reducing agent supplying device used in such an exhaust purification device is a reducing agent supplying device that includes a pump and a reducing agent injector, and pressure-feeds the reducing agent in a storage tank with the pump and supplies the reducing agent into the exhaust pipe via the reducing agent injector fixed to the exhaust pipe (see Patent Document 1).

[0004] Patent Document 1 discloses a diagnostic device and diagnostic method capable of detecting leakage of reducing agent from a reducing agent injector into an exhaust passage. Some abnormality may occur in the reducing agent injector due to deterioration over time of the seat part of the reducing agent injector, adhesion of relics, or sticking of the valve body open, which may cause reducing agent to leak from the reducing agent injector into the exhaust passage. This diagnostic device detects leakage of reducing agent from the reducing agent injector into the exhaust passage due to the valve body of the reducing agent injector being stuck open. Specifically, the reducing agent injector leakage diagnostic device includes an ammonia concentration detection means for detecting the ammonia concentration in exhaust gas, and determines whether or not there is leakage of reducing agent from the reducing agent injector into the exhaust passage based on the detected ammonia concentration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-149365 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, reducing agent leakage is not limited to leakage from the reducing agent injection valve into the exhaust passage. The reducing agent is pumped by a pump and sent to the reducing agent injection valve through a reducing agent supply passage. The pressure-feeding path, where the internal pressure is high, is more likely to cause leakage than other parts where the internal pressure is low. Therefore, it is necessary to check for leaks more frequently and, if a leak is detected, to be able to carry out repairs, etc. It is also important that leak checks are performed without interrupting the purification of exhaust gas. This is because if the purification of exhaust gas is interrupted, there is a risk that the amount of nitrogen oxides contained in the exhaust gas discharged into the atmosphere will increase during the interruption.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a reducing agent supply device and a control method thereof that enable frequent leak checks in a pressure path including a pump, a reducing agent injection valve, and a reducing agent supply passage, etc., and that, if a leak is detected, allows repairs, etc. to be carried out, and that enables leak checks to be performed without interrupting the purification of exhaust gas. [Means for solving the problem]

[0008] A reducing agent supply device according to the present invention is a reducing agent supply device (20) including: a reducing agent injector (25) attached upstream of a reducing catalyst (13) provided in an exhaust pipe (11) of an internal combustion engine (1); a pump (31) that pressure-feeds a reducing agent to the reducing agent injector (25); a reducing agent supply passage (52) that connects the pump (31) and the reducing agent injector (25); and a control device (100) that controls the pump (31) and the reducing agent injector (25), The control device (100) is a reducing agent supply device that, when it detects that the ignition switch of the internal combustion engine (1) has been turned off, determines whether or not there is a reducing agent leak in a pressure-feed path including the pump (31), the reducing agent injection valve (25), and the reducing agent supply passage (52), and then recovers the reducing agent.

[0009] A method for controlling a reducing agent supplying device according to the present invention is a method for controlling a reducing agent supplying device (20) including a reducing agent injector (25) attached upstream of a reducing catalyst (13) provided in an exhaust pipe (11) of an internal combustion engine (1), a pump (31) that pressure-feeds a reducing agent to the reducing agent injector (25), a reducing agent supply passage (52) that connects the pump (31) and the reducing agent injector (25), and a control device (100) that controls the pump (31) and the reducing agent injector (25), comprising: The control method is a control method for a reducing agent supply device, comprising: a step of determining whether or not there is a reducing agent leak in a pressure-feed path including the pump (31), the reducing agent injection valve (25), and the reducing agent supply passage (52) when it is detected that an ignition switch of the internal combustion engine has been turned off; and a step of recovering the reducing agent. Effect of the Invention

[0010] According to the present invention, it is possible to provide a reducing agent supply device and a control method thereof, which perform frequent leak checks in a pressure path including a pump, a reducing agent injection valve, and a reducing agent supply passage, etc., and, if a leak is detected, can carry out repairs, etc., and can perform leak checks without interrupting the purification of exhaust gas. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of the configuration of an exhaust gas purification device including a reducing agent supply device according to an embodiment of the present invention. [Diagram 2] 2 shows an example of a configuration in which components provided in a control device of a reducing agent supply device according to an embodiment of the present invention are represented by functional blocks. [Diagram 3]2 is a flowchart for explaining an example (Example 1) of the operation of the reducing agent supply device and a control method thereof according to the embodiment of the present invention. [Figure 4] 11 is a flowchart illustrating an example of a leak check. [Diagram 5] 4 is a flowchart for explaining an example of reducing agent recovery. [Figure 6] 5 is a flowchart for explaining an example (Example 2) of the operation of the reducing agent supply device and a control method thereof according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the reducing agent supply device and the control method thereof according to the present invention will be described in detail with reference to the drawings as appropriate. In each drawing, the same reference numerals denote the same members unless otherwise specified, and the description thereof will be omitted as appropriate.

[0013] Hereinafter, a reducing agent supply device and a method for controlling the reducing agent supply device according to an embodiment of the present invention will be described.

[0014] <Overall configuration of exhaust purification system> 1 is a schematic diagram for explaining an example of the overall configuration of an exhaust purification device 10 equipped with a reducing agent supply device 20. This exhaust purification device 10 is a device for purifying NOx in exhaust gas, and is provided in an exhaust pipe 11 of an internal combustion engine 1 such as a diesel engine. The exhaust purification device 10 is equipped with a reducing catalyst 13 interposed midway through the exhaust pipe 11, and a reducing agent supply device 20 for supplying a reducing agent into the exhaust pipe 11 upstream of the reducing catalyst 13.

[0015] The reduction catalyst 13 is a catalyst that has the function of promoting the reduction reaction of NOx in the exhaust gas, adsorbing the reducing component generated from the reducing agent, and selectively reducing the NOx in the exhaust gas that flows into the catalyst with the reducing component. The reducing agent supply device 20 uses urea water as the reducing agent, and the urea water is decomposed in the exhaust pipe 11 to generate ammonia as the reducing component.

[0016] <Reducing agent supply device> As shown in FIG. 1, the reducing agent supply device 20 includes as its main components a tank 21 that stores the reducing agent, a reducing agent injection valve 25 for injecting the reducing agent into the exhaust pipe 11, a supply pump 31 that pressure-feeds the reducing agent in the tank 21 to the reducing agent injection valve 25, a recovery pump 41 that recovers the reducing agent in the tank 21, and a control device 100 that is electrically connected to the reducing agent injection valve 25 and the pumps 31, 41 and electronically controls them.

[0017] The tank 21 and the pressurizing chamber of the supply pump 31 are in communication with each other via a first passage 51. A first filter 71 and a first check valve 61 are provided in the first passage 51. The first check valve 61 functions to allow the reducing agent to flow only in the direction from the tank 21 to the supply pump 31.

[0018] The pressurization chamber of the supply pump 31 and the reducing agent injection valve 25 are in communication with each other via a second passage 52. A second check valve 62 and a branch point 59 to the recovery pump 41 are provided in the middle of the second passage 52. The second check valve 62 functions to allow the reducing agent to flow only in the direction from the supply pump 31 to the branch point 59. The second passage 52 is a reducing agent supply passage that connects the supply pump 31 and the reducing agent injection valve 25.

[0019] The third passage 53 branches off at a branch point 59 provided in the middle of the second passage 52, and communicates with the pressurizing chamber of the recovery pump 41. A third check valve 63 is provided in the middle of the third passage 53. The third check valve 63 functions to allow the reducing agent to flow only in the direction from the branch point 59 to the recovery pump 41.

[0020] The pressurizing chamber of the recovery pump 41 and the tank 21 are in communication with each other via a fourth passage 54. A fourth check valve 64 and a second filter 72 are provided in the middle of the fourth passage 54. The fourth check valve 64 functions to allow the reducing agent to flow only in the direction from the recovery pump 41 to the tank 21.

[0021] The supply pump 31 has an internal electromagnetic coil, and is a type of pump that operates by repeatedly energizing and de-energizing (on and off) this electromagnetic coil. Hereinafter, the energization and de-energization of the electromagnetic coil of the supply pump 31 may be simply referred to as energization and de-energization of the supply pump 31. The energization and de-energization of the supply pump 31 is controlled by the control device 100.

[0022] The supply pump 31 is a diaphragm type pump having a diaphragm that defines a pressurized chamber. When the supply pump 31 is energized, the pressurized chamber of the supply pump 31 is compressed by the diaphragm, and the medium in the pressurized chamber, for example, the reducing agent, is pushed out in the direction of the second passage 52. When the supply pump 31 is de-energized, the diaphragm moves in a direction that expands the pressurized chamber by a spring, and the reducing agent and the like flow into the pressurized chamber from the first passage 51. When the supply pump 31 is maintained energized, the pressurized chamber of the supply pump 31 is closed, and the first passage 51 and the second passage 52 are hydraulically separated.

[0023] The recovery pump 41 also has an internal electromagnetic coil, and is a type of pump that operates by repeatedly energizing and de-energizing (on and off) this electromagnetic coil. Hereinafter, the energization and de-energization of the electromagnetic coil of the recovery pump 41 may be simply referred to as energization and de-energization of the recovery pump 41. The energization and de-energization of the recovery pump 41 is controlled by the control device 100.

[0024] The recovery pump 41 is a diaphragm type pump having a diaphragm that defines a pressurized chamber. When the recovery pump 41 is energized, the diaphragm moves to expand the pressurized chamber of the recovery pump 41, and reducing agent and the like flow into the pressurized chamber from the third passage 53. When the recovery pump 41 is de-energized, the pressurized chamber is compressed by the diaphragm pressed by a spring, and the reducing agent and the like in the pressurized chamber are pushed out in the direction of the fourth passage 54. When the recovery pump 41 is maintained in a de-energized state, the pressurized chamber of the recovery pump 41 is closed, and the third passage 53 and the fourth passage 54 are hydraulically separated.

[0025] The supply pump 31 and the recovery pump 41 may be configured as a supply module 27 included in one package. In this case, the supply module 27 also includes the first passage 51, the third passage 53, the fourth passage 54, and the branch point 59 in its configuration. The second passage 52, which is a reducing agent supply passage, is made up of the 2A passage 52A and the 2B passage 52B, and the 2B passage 52B is included in the supply module 27. The 2A passage 52A is configured as a pipe that connects the connection point 57 with the 2B passage 52B to the reducing agent injector 25. The range included in the supply module 27 is indicated by a dashed line in FIG. 1. The supply module 27 may be designed to be connected below the tank 21.

[0026] When the control device 100 supplies the reducing agent in the tank 21 to the reducing agent injector 25, it repeatedly energizes and de-energizes the supply pump 31 while keeping the recovery pump 41 de-energized. As a result, the reducing agent in the tank 21 is sucked into the pressurizing chamber of the supply pump 31, and is further pressure-fed by the supply pump 31 in the direction of the reducing agent injector 25.

[0027] Furthermore, when recovering the reducing agent in the reducing agent injection valve 25 to the tank 21, the control device 100 keeps the supply pump 31 de-energized and repeatedly energizes and de-energizes the recovery pump 41. As a result, the reducing agent in the reducing agent injection valve 25 is sucked into the pressurizing chamber of the recovery pump 41, and is further pressure-fed by the recovery pump 41 in the direction of the tank 21.

[0028] The reducing agent injector 25 is a so-called electromagnetic on / off valve. When an electromagnetic coil of the reducing agent injector 25 is energized, the reducing agent injector 25 opens, and when it is de-energized, the reducing agent injector 25 closes. Hereinafter, energization / de-energization of the electromagnetic coil of the reducing agent injector 25 may be referred to as energization / de-energization of the reducing agent injector 25 for simplicity. While the internal combustion engine 1 is operating, the reducing agent injector 25 is controlled to open and close by the control device 100 so that the required amount of reducing agent is supplied into the exhaust pipe 11.

[0029] An exhaust temperature sensor 80 for detecting the temperature inside the exhaust pipe 11 may be attached to the exhaust pipe 11 .

[0030] A pressure sensor 82 for detecting the pressure of the reducing agent in the second passage 52 is attached to the second passage 52. The pressure P detected by the pressure sensor 82 is acquired by the control device 100.

[0031] The first filter 71 is provided in the first passage 51 and is a filter that collects foreign matter such as dust in the reducing agent moving from the tank 21 to the supply pump 31. The second filter 72 is provided in the fourth passage 54 and is a filter that collects foreign matter such as dust in the reducing agent returned to the tank 21.

[0032] <Control device> 2 shows an example of the configuration of the control device 100, in which the parts related to the control of the present invention are represented by functional blocks. This control device 100 is configured mainly with a known microcomputer, and has an acquisition unit 103, a control unit 105, and a judgment unit 107. Specifically, each of these units is realized by the execution of a program by the microcomputer.

[0033] In addition, the control device 100 is equipped with memory elements (not shown) such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a timer counter, and a drive circuit for controlling the supply of electricity to each of the pumps 31, 41 and the reducing agent injection valve 25.

[0034] The acquisition unit 103 acquires a signal IG from an ignition switch (not shown) and a pressure P detected by the pressure sensor 82. The acquisition unit 103 may be configured to acquire information from devices other than these. For example, the acquisition unit 103 may be configured to acquire a temperature T from the exhaust temperature sensor 80, or may be configured to acquire information from the internal combustion engine control device 200. The acquired information is sent to the control unit 105 and / or the determination unit 107.

[0035] The control unit 105 drives and controls the reducing agent injector 25, the supply pump 31, and the recovery pump 41. Specifically, the control unit 105 controls the reducing agent injector 25, the supply pump 31, and the recovery pump 41 to be energized or de-energized. The control unit 105 may be configured to control devices other than these. For example, the control unit 105 may be configured to send information to a transmission device 210 intended to inform the driver of information.

[0036] The determination unit 107 performs various determinations executed within the control device 100. For example, the determination unit makes a determination regarding the signal IG from the ignition switch, the pressure P detected by the pressure sensor 82, and the time t. The determination unit 107 may make a determination regarding other information.

[0037] The operations of the acquisition unit 103, the control unit 105 and the decision unit 107 are further described below.

[0038] An example (Example 1) of the operation of the reducing agent supply device 20 according to the embodiment of the present invention and its control method will be described with reference to the flowcharts of Figures 3, 4, and 5. Note that Figure 3 is a flowchart of the main routine related to Example 1, Figure 4 is a flowchart of subroutine 1 related to leakage check, and Figure 5 is a flowchart of subroutine 2 related to reducing agent recovery. First, the flow of the main routine will be described with reference to Figure 3.

[0039] In step S10, the main routine of the first embodiment starts, and the process proceeds to step S20.

[0040] In step S20, acquisition unit 103 acquires signal IG from the ignition switch, sends it to decision unit 107, and the process proceeds to step S30.

[0041] In step S30, the determination unit 107 determines whether or not the ignition switch is turned off. If the ignition switch is turned off, the process proceeds to step S40, and if the ignition switch is turned on, the process returns to step S20.

[0042] In step S40, the process proceeds to subroutine 1. In subroutine 1, a leak in the pressure-feeding path is checked. The pressure-feeding path includes the supply pump 31, the recovery pump 41, the reducing agent injector 25, the second passage (reducing agent supply passage) 52, etc. After completing subroutine 1, the process proceeds to step S50.

[0043] In step S50, the flow proceeds to subroutine 2. In subroutine 2, recovery of the reducing agent is performed, which involves sucking the reducing agent from the reducing agent injection valve 25, etc., back toward the tank 21. After completing subroutine 2, the flow proceeds to step S60, where the flow chart ends.

[0044] Next, the flow of the leak check subroutine 1 will be described with reference to FIG.

[0045] In step S400, subroutine 1 starts, and the process proceeds to step S410.

[0046] In step S410, the control unit 105 closes the reducing agent injector 25, closes the pressurizing chamber of the supply pump 31, and confirms that the pressurizing chamber of the recovery pump 41 is closed, and then proceeds to step S420. In step S410, the reducing agent injector 25 is closed, and the pressurizing chambers of the supply pump 31 and the recovery pump 41 are closed, thereby sealing the pressure-feeding path. Therefore, if there is no leakage in the pressure-feeding path, theoretically, there should be no change in the pressure in the pressure-feeding path.

[0047] In step S420, the acquisition unit 103 acquires the pressure P from the pressure sensor 82 (the starting pressure Ps), and the control unit 105 starts the timer A, and the process proceeds to step S430.

[0048] In step S430, the judgment unit judges whether the time t counted by timer A is equal to or greater than the threshold time tth. If the time t is equal to or greater than the threshold time tth, the process proceeds to step S440, and if the time t is less than the threshold time tth, the process returns to step S430.

[0049] In step S440, the acquisition unit 103 acquires the pressure P from the pressure sensor 82 (end pressure Pf), and the process proceeds to step S450.

[0050] In step S450, the control unit 105 calculates the differential pressure ΔP (=Ps−Pf) by subtracting the end pressure Pf from the start pressure Ps, and proceeds to step S460.

[0051] In step S460, the judgment unit 107 judges whether the differential pressure ΔP is equal to or greater than the threshold differential pressure ΔPth. If the differential pressure ΔP is less than the threshold differential pressure ΔPth, the process proceeds to step S480, where the subroutine 1 is terminated and the process returns to the main routine. This is because if the pressure drop in the pumping path is less than the threshold differential pressure ΔPth, it is considered that there is no leakage in the pumping path and that the leakage is within the allowable range or the measurement error range. On the other hand, if the differential pressure ΔP is equal to or greater than the threshold differential pressure ΔPth, the process proceeds to step S470.

[0052] In step S470, the control unit 105 notifies the driver of the vehicle, for example through the transmission device 210, that a leak has occurred in the reducing agent supply device 20 and that repair is required. This is because if the pressure drop in the pressure-feeding path is equal to or greater than the threshold pressure difference ΔPth, it is believed that a leak has occurred somewhere in the pressure-feeding path. After that, the process proceeds to step S480, where subroutine 1 is ended, and the process returns to the main routine.

[0053] Next, the flow of the reducing agent recovery subroutine 2 will be explained using FIG. 5. When the reducing agent, urea water, freezes, its volume increases. Therefore, if the ambient temperature drops after the internal combustion engine is stopped, the reducing agent remaining in the reducing agent injection valve or the reducing agent supply pipe may freeze, which may damage the reducing agent injection valve or the reducing agent supply pipe. The purpose of recovering the reducing agent is to avoid these problems.

[0054] In step S500, subroutine 2 is started, and the process proceeds to step S510.

[0055] In step S510, the control unit 105 de-energizes the reducing agent injection valve 25 and the supply pump 31, and energizes the recovery pump 41, and then proceeds to step S520. By energizing the recovery pump 41, the diaphragm of the recovery pump 41 moves in a direction that connects the third passage 53 and the fourth passage 54. As a result, the pressure in the reducing agent supply passage, which had been adjusted to the system pressure, begins to decrease. The system pressure is the pressure of the reducing agent in the reducing agent supply passage when the reducing agent supply device supplies the reducing agent to the exhaust pipe 11.

[0056] In step S520, the acquisition unit 103 acquires the pressure P from the pressure sensor 82 and sends it to the judgment unit 107. The judgment unit 107 judges whether the pressure P detected by the pressure sensor 82 is equal to or lower than the first predetermined pressure Pth1. If the pressure P has dropped to equal to or lower than the first predetermined pressure Pth1, the process proceeds to step S530, and if the pressure P is higher than the first predetermined pressure Pth1, the process returns to step S520. The judgment unit 107 may make a judgment based on the elapsed time after the recovery pump 41 is energized. For example, the time required for the pressure P to change from the system pressure to the first predetermined pressure Pth1 may be examined in an experiment, and the process may proceed to step S530 when the time has elapsed.

[0057] In step S530, the control unit 105 controls the recovery pump 41 to be alternately energized and de-energized while keeping the reducing agent injector 25 and the supply pump 31 de-energized, and then proceeds to step S540. As a result, the pressure in the reducing agent supply passage begins to drop further.

[0058] In step S540, the acquisition unit 103 acquires the pressure P from the pressure sensor 82 and sends it to the judgment unit 107. The judgment unit 107 judges whether the pressure P detected by the pressure sensor 82 is equal to or lower than the second predetermined pressure Pth2. If the pressure P has dropped to equal to or lower than the second predetermined pressure Pth2, the process proceeds to step S550, and if the pressure P is higher than the second predetermined pressure Pth2, the process returns to step S540. The judgment unit 107 may make a judgment based on the elapsed time after the recovery pump 41 starts to be repeatedly energized and deenergized. For example, the time until the pressure P reaches the first predetermined pressure Pth1 may be examined by an experiment, and the process proceeds to step S550 when the time has elapsed. Here, the second predetermined pressure Pth2 is, for example, a pressure lower than the pressure in the exhaust pipe when the internal combustion engine is stopped. By setting the pressure in the reducing agent supply passage at such a pressure, when the reducing agent injector 25 is opened in the next step S550, the air (including exhaust gas) in the exhaust pipe flows into the opening of the reducing agent injector 25. Therefore, when the reducing agent injector 25 is opened, there is no risk of the reducing agent leaking from the opening of the reducing agent injector 25. The pressure in the exhaust pipe when the internal combustion engine is stopped is atmospheric pressure or a pressure close to atmospheric pressure.

[0059] In step S550, the control unit 105 energizes the reducing agent injector 25 and de-energizes the supply pump 31, controls the recovery pump 41 to be alternately energized and de-energized, and proceeds to step S560. By energizing the reducing agent injector 25, the reducing agent injector 25 is opened. By alternately energizing and de-energizing the recovery pump 41, the reducing agent in the reducing agent injector 25 and the reducing agent supply pipe (second passage 52) moves toward the tank 21 via the recovery pump 41. As the reducing agent moves, air flows in from the opening of the reducing agent injector 25.

[0060] In step S560, the judgment unit 107 judges whether or not the first predetermined time tp1 has elapsed since the start of recovery by the recovery pump 41. If the first predetermined time tp1 has elapsed since the start of recovery by the recovery pump 41, the process proceeds to step S570, and if the first predetermined time tp1 has not elapsed since the start of recovery by the recovery pump 41, the process returns to step S560.

[0061] In step S570, the control unit 105 de-energizes the reducing agent injection valve 25 and the supply pump 31, and stops the repeated energization and de-energization of the recovery pump 41. This stops the movement of the reducing agent and the accompanying inflow of air. The first predetermined time tp1 is set as the time it takes for the boundary between the reducing agent and the air to reach a predetermined recovery point located on the reducing agent injection valve 25 side of the branch point 59. The reducing agent passages (e.g., the first to fourth passages, etc.) leading from the recovery point toward the tank 21 are provided with dampers (not shown) in case the urea water freezes, and are structured to prevent malfunctions such as damage at low temperatures even if the urea water remains in these parts. Thereafter, the process proceeds to step S580, the subroutine 2 is ended, and the process returns to the main routine.

[0062] Thus, according to the present invention (Example 1), since the reducing agent leakage is checked every time the ignition switch of the internal combustion engine 1 is detected to be turned off, the frequency of checking for leakage in the pressure-feed path including the pumps 31, 41, the reducing agent injection valve 25, and the reducing agent supply passage 52 can be increased. Furthermore, according to the present invention, when a leakage occurs in the pressure-feed path, the occurrence of the leakage is notified to the driver of the vehicle through the transmission device 201 or the like, so that the leakage can be stopped before it spreads and becomes large by repair or the like. Furthermore, since the leakage check is performed after it is detected that the ignition switch of the internal combustion engine 1 is turned off, the purification of the exhaust gas is not interrupted. In addition, since the reducing agent in the reducing agent injection valve 25 or the like is recovered after the presence or absence of leakage is confirmed, there is no risk of the reducing agent injection valve 25 being damaged due to freezing of the reducing agent even if the surrounding temperature drops thereafter.

[0063] Next, an example (Example 2) of the operation of the reducing agent supply device 20 according to the embodiment of the present invention and its control method will be described with reference to the flowchart of Fig. 6. Note that Fig. 6 is a flowchart of a main routine, and subroutine 1 relating to the leak check and subroutine 2 relating to the reducing agent recovery are as previously described with reference to Figs. 4 and 5, respectively.

[0064] In step S100, the main routine of the second embodiment starts, and the process proceeds to step S110.

[0065] In step S110, the acquisition unit 103 acquires information IS relating to idling stop, sends it to the determination unit 107, and proceeds to step S120. The information IS relating to idling stop may be acquired, for example, from the internal combustion engine control device 200, or may be acquired from another device.

[0066] In step S120, the determination unit 107 determines whether or not the internal combustion engine 1 has been stopped by the idling stop function. If the internal combustion engine 1 has been stopped by the idling stop function, the process proceeds to step S130, and if the internal combustion engine 1 has not been stopped by the idling stop function, the process returns to step S110.

[0067] In step S130, the process proceeds to subroutine 1. In subroutine 1, a leak in the pressure-feeding path is checked. The pressure-feeding path includes the supply pump 31, the reducing agent injector 25, the second passage 52, and the like. After completing subroutine 1, the process proceeds to step S140, where the main routine of the second embodiment is terminated.

[0068] Thus, according to the present invention (Example 2), since the reducing agent leak is checked every time the internal combustion engine 1 is stopped by the idling stop function, it is possible to increase the frequency of leak checks in the pressure-feed path including the pumps 31, 41, the reducing agent injection valve 25, and the reducing agent supply passage 52, etc. Furthermore, according to the present invention, if a leak occurs in the pressure-feed path, the driver of the vehicle is notified of the occurrence of the leak via the transmission device 201, etc., so that the leak can be stopped before it spreads and becomes large by repairs, etc. Also, since the leak check is performed after it is detected that the internal combustion engine 1 has been stopped by the idling stop function, the purification of exhaust gas is not interrupted.

[0069] Furthermore, in the reducing agent supply device 20 according to the embodiment of the present invention and the control method thereof, it is also possible to combine Example 1 and Example 2. When Example 1 and Example 2 are combined, it is possible to further increase the frequency of leak checks in the pressure-feed path.

[0070] In the above embodiment, the reducing agent supply device 20 has the supply pump 31 and the recovery pump 41 separately, but the application of the present invention is not limited to this type of reducing agent supply device. For example, the present invention can also be applied to a reducing agent supply device equipped with one pump and a flow path switching valve. Here, the flow path switching valve switches the flow direction of the reducing agent pressure-fed by the pump. That is, when the flow path switching valve is switched in one direction, the reducing agent in the tank is pressure-fed in the direction of the reducing agent injection valve by the operation of the pump, as in the case where the supply pump 31 in the above embodiment is operated. Also, when the flow path switching valve is switched in the other direction, the reducing agent in the reducing agent injection valve is pressure-fed in the direction of the tank by the operation of the pump, as in the case where the recovery pump 41 in the above embodiment is operated. Furthermore, the present invention can also be applied to a reducing agent supply device equipped with a pump that can change the flow direction of the reducing agent by changing the rotation direction. In this way, the present invention can be applied to a reducing agent supply device having various pressure-fed paths.

[0071] Also, the leak check subroutine 1 described with reference to FIG. 4 is not limited to this. A different leak check may be selected according to the type of reducing agent supply device. For example, in a type of reducing agent supply device in which a pipe line having a restriction in the middle of a reducing agent supply passage branches off in a passage for returning excess reducing agent to a tank, the reducing agent injection valve may be closed, the input power to the pump may be kept constant (for example, when the input to the pump is duty controlled, the duty ratio may be kept constant) and reducing agent may be sent in the direction of the reducing agent injection valve to check for leaks based on the change in pressure in the reducing agent supply passage, etc. Compared to when there is no leak, when there is a leak, the pressure drop is greater, so the presence or absence of a leak can be determined based on the magnitude of the pressure drop. Conversely, the pump may be controlled to keep the pressure in the reducing agent supply passage constant, and leaks may be checked based on the change in the input power at that time (for example, when the input to the pump is duty controlled, the duty ratio changes). Compared to when there is no leak, when there is a leak, the input to the pump is greater (the duty ratio is greater), so the presence or absence of a leak can be determined based on the magnitude of the input to the pump (the magnitude of the duty ratio).

[0072] As described above, according to the present invention, it is possible to provide a reducing agent supply device and a control method thereof, which enable frequent leak checks in a pressure path including a pump, a reducing agent injection valve, and a reducing agent supply passage, etc., and, if a leak is detected, allows repairs, etc. to be carried out, and enables leak checks to be performed without interrupting the purification of exhaust gas.

[0073] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modified or amended examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0074] 1 internal combustion engine, 10 exhaust purification device, 11 exhaust pipe, 13 reduction catalyst, 20 reducing agent supply device, 21 tank, 25 reducing agent injection valve, 27 supply module, 31 supply pump, 41 recovery pump, 51 first passage, 52 second passage, 52A second A passage, 52B second B passage, 53 third passage, 54 fourth passage, 57 connection point, 59 branch point, 61 first check valve, 62 second check valve, 63 third check valve, 64 fourth check valve, 71 first filter, 72 second filter, 80 exhaust temperature sensor, 82 pressure sensor, 100 control device, 103 acquisition unit, 105 control unit, 107 judgment unit, 200 internal combustion engine control device, 210 transmission device

Claims

1. a reducing agent injection valve (25) installed upstream of a reducing catalyst (13) provided in an exhaust pipe (11) of an internal combustion engine (1); a pump (31) for pumping a reducing agent to the reducing agent injection valve (25); a reducing agent supply passage (52) connecting the pump (31) and the reducing agent injection valve (25); a control device (100) for controlling the pump (31) and the reducing agent injection valve (25); A reducing agent supply device (20) comprising: The control device (100) when it is detected that an ignition switch of the internal combustion engine (1) has been turned off, it is determined whether or not there is a leakage of the reducing agent in a pressure-feed path including the pump (31), the reducing agent injection valve (25), and the reducing agent supply passage (52), and then the reducing agent is recovered. Reductant supply device.

2. When the control device (100) acquires information that the internal combustion engine (1) has been stopped by an idling stop function of a vehicle equipped with the reducing agent supply device (20), the control device (100) further determines whether or not there is a reducing agent leak in a pressure-feed path including the pump (31), the reducing agent injection valve (25), and the reducing agent supply passage (52). The reducing agent supply device according to claim 1 .

3. A method for controlling a reducing agent supply device (20) including a reducing agent injection valve (25) attached upstream of a reducing catalyst (13) provided in an exhaust pipe (11) of an internal combustion engine (1), a pump (31) that pumps a reducing agent to the reducing agent injection valve (25), a reducing agent supply passage (52) that connects the pump (31) and the reducing agent injection valve (25), and a control device (100) that controls the pump (31) and the reducing agent injection valve (25), The control method includes: a step of determining whether or not there is a reducing agent leak in a pressure-feed path including the pump (31), the reducing agent injection valve (25), and the reducing agent supply passage (52) when it is detected that an ignition switch of the internal combustion engine has been turned off; and performing a recovery of the reducing agent. A method for controlling a reducing agent supply device.

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