Reductant supply device, and control device and control method for reductant supply device

Abstract

To provide a control device of a reductant supply device that, when a residual urea aqueous solution in a reductant injection valve is solidified when starting an internal combustion engine, can eliminate the solidification of the urea aqueous solution by energizing a coil of the reductant agent injection valve, and can prevent subsequent re-solidification.SOLUTION: In a control device (100) for a reductant supply device (20) that fills a device with a urea aqueous solution as a reductant when starting an internal combustion engine (1) and controls a reductant injection valve (25) to inject the urea aqueous solution into an exhaust pipe (11) of the internal combustion engine (1), electricity is conducted to a coil (25c) of the reductant injection valve (25) to eliminate sticking in the reductant injection valve (25), and after the sticking of the reductant injection valve (25) is eliminated, electric conduction is continued to be applied to the coil (25c) until the coil (25c) reaches a threshold temperature (Tth).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a reducing agent supply device for injecting a urea aqueous solution as a reducing agent into an exhaust passage of an internal combustion engine, and a control device and method for the reducing agent injection device. [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 system is a reducing agent supplying device that includes a pump and a reducing agent injection valve, and that pressure-feeds the urea aqueous solution in a storage tank using the pump and supplies the urea aqueous solution into the exhaust pipe via the reducing agent injection valve fixed to the exhaust pipe (see Patent Document 1).

[0004] Patent Document 1 describes that, in order to prevent the urea aqueous solution, which is the reducing agent, from freezing in the reducing agent injection valve or in the reducing agent supply pipe after the internal combustion engine is stopped, a control is performed in which the reducing agent injection valve is opened and a pump is rotated in the reverse direction to suck the urea aqueous solution in the reducing agent injection valve and the reducing agent supply pipe back toward the tank, and further, when the internal combustion engine is subsequently restarted, a control is performed in which the reducing agent injection valve is opened to bleed air from inside the reducing agent injection valve while filling the reducing agent injection valve with the urea aqueous solution.

[0005] Furthermore, Patent Document 2 describes that an aqueous urea solution frozen in a reducing agent injection valve is thawed by passing current through a coil of the reducing agent injection valve. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-027364 A [Patent Document 2] JP 2013-221425 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the reducing agent supply device described in Patent Document 1, in order to prevent the urea aqueous solution from freezing after the internal combustion engine is stopped, a control is performed to suck back the urea aqueous solution in the reducing agent injection valve toward the tank. At this time, if the urea aqueous solution remains in the reducing agent injection valve, it may solidify and cause the reducing agent injection valve to malfunction due to sticking. In such a case, when the internal combustion engine is restarted, the sticking can be eliminated by energizing the coil of the reducing agent injection valve described in Patent Document 2. After that, the reducing agent injection valve whose sticking has been eliminated can be opened to bleed the air in the reducing agent injection valve while filling the reducing agent injection valve with the urea aqueous solution. However, even after the solidification of the urea aqueous solution is eliminated by energizing the reducing agent injection valve, there is a possibility that the urea aqueous solution may resolidify due to the influence of the ambient temperature, for example. This is because the temperature rise caused by energizing the coil is concentrated in the vicinity of the coil and is easily affected by the ambient temperature. If the resolidification occurs, it is necessary to energize again, and it is assumed that there will be a problem such as a longer time until the urea aqueous solution is supplied to the exhaust pipe after the internal combustion engine is started.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a reducing agent supply device, a control device for a reducing agent supply device, and a control method thereof that are capable of eliminating solidification of the urea aqueous solution and preventing subsequent re-solidification by passing current through the coil of the reducing agent injection valve when the reducing agent injection valve is stuck due to solidification of residual urea aqueous solution at the start of an internal combustion engine. [Means for solving the problem]

[0009] The control device for a reducing agent supply device according to the present invention comprises: A control device (100) for a reducing agent supply device (20) that fills the device with a urea aqueous solution as a reducing agent at the start of an internal combustion engine (1) and controls a reducing agent injection valve (25) to inject the urea aqueous solution into an exhaust pipe (11) of the internal combustion engine (1), The control device (100) for the reducing agent supply device (20) supplies current to a coil (25c) of the reducing agent injector (25) in order to eliminate sticking inside the reducing agent injector (25), and continues to supply current to the coil (25c) until the coil (25c) reaches a threshold temperature (Tth) after the sticking of the reducing agent injector (25) is eliminated.

[0010] A method for controlling a reducing agent supply device according to the present invention includes: A method for controlling a reducing agent supply device (20) for filling a device with a urea aqueous solution as a reducing agent at the start of an internal combustion engine (1) and controlling a reducing agent injection valve (25) to inject the urea aqueous solution into an exhaust pipe (11) of the internal combustion engine (1), comprising: a step of energizing a coil (20c) of the reducing agent injection valve (25) to eliminate sticking in the reducing agent injection valve (25); a step of continuing to energize the coil (20c) until the coil (20c) reaches a threshold temperature (Tth) after the sticking of the reducing agent injection valve (25) is resolved; The present invention relates to a method for controlling a reducing agent supply device (20). Effect of the Invention

[0011] According to the present invention, when the reducing agent injection valve is stuck due to solidification of residual urea aqueous solution at the start of an internal combustion engine, it is possible to provide a reducing agent supply device, a control device for a reducing agent supply device, and a control method thereof, which are capable of eliminating the solidification of the urea aqueous solution and preventing subsequent re-solidification by passing current through the coil of the reducing agent injection valve. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an example of the configuration of an exhaust gas purification device including a control device for a reducing agent supply device according to an embodiment of the present invention; [Diagram 2]2 is a schematic diagram showing an example of a reducing agent injection valve controlled by a control device of a reducing agent supply device according to an embodiment of the present invention. FIG. [Diagram 3] FIG. 2 is a schematic diagram showing a configuration example in which components provided in a control device for a reducing agent supply device according to an embodiment of the present invention are represented by functional blocks. [Figure 4] 5 is a flowchart for illustrating control for recovering the urea aqueous solution in the reducing agent injection valve toward the tank, which is executed after the internal combustion engine is stopped. [Diagram 5] 4 is a flowchart for illustrating control executed by a control device of a reducing agent supply device according to an embodiment of the present invention. [Figure 6] 4 is an example of a current waveform when current is applied to a reducing agent injection valve by a control device of a reducing agent supply device according to an embodiment of the present invention. [Figure 7] 4 is an example of a current waveform when current is applied to a reducing agent injection valve by a control device of a reducing agent supply device according to an embodiment of the present invention. [Figure 8] FIG. 4 is a phase diagram of an aqueous urea solution whose injection is controlled by the control device of the reducing agent supply device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a reducing agent supply device, a control device for a reducing agent supply device, and a 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.

[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 including a reducing agent supply device 20 and a control device 100 thereof according to an embodiment of the present invention. The 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 includes a reducing catalyst 13 disposed midway through the exhaust pipe 11, and a reducing agent supply device 20 for supplying a urea aqueous solution as a reducing agent into the exhaust pipe 11 upstream of the reducing catalyst 13.

[0015] The reduction catalyst 13 is a catalyst that has a function of promoting the reduction reaction of NOx in the exhaust gas, adsorbing a reducing component generated from a 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 a urea aqueous solution as a reducing agent, and the urea aqueous solution is decomposed in the exhaust pipe 11 to generate ammonia as a reducing component.

[0016] <Reducing agent supply device> As shown in FIG. 1, the reducing agent supply device 20 mainly comprises a tank 21 that stores a urea aqueous solution, a reducing agent injection valve 25 for injecting the urea aqueous solution into the exhaust pipe 11, a supply module 31 that pumps out the urea aqueous solution in the tank 21 and pressure-feeds it to the reducing agent injection valve 25, or recovers the urea aqueous solution remaining in the reducing agent injection valve 25 or the like into the tank 21, and a control device 100 that is electrically connected to the reducing agent injection valve 25 and the supply module 31 and electronically controls them.

[0017] The tank 21 and the supply module 31 are connected by a first passage 51. Moreover, the supply module 31 and the reducing agent injector 25 are connected by a second passage 52 (reducing agent supply pipe). The urea aqueous solution pumped out from the tank 21 is guided to the reducing agent injector 25 via the first passage 51 and the second passage 52 in this order. The urea aqueous solution recovered from the reducing agent injector 25 is returned to the tank 21 via the second passage 52 and the first passage 51 in this order. Furthermore, the supply module 31 and the tank 21 may be connected by a third passage 53. For example, the third passage 53 may be connected to the second passage 52 in the supply module 31, and when the urea aqueous solution is supplied to the reducing agent injector 25 from the second passage 52, an excess urea aqueous solution may be returned to the tank 21 via the third passage 53.

[0018] The supply module 31 includes a pump 33. The pump 33 is, for example, an electric diaphragm pump or a motor pump. The output of the pump is controlled based on a control signal from the control device 100.

[0019] The pump 33 included in the supply module 31 may have, for example, a flow path switching valve. The flow path switching valve switches the flow path direction of the urea aqueous solution pressure-fed by the pump 33. One flow path direction is the direction in which the urea aqueous solution flows from the tank 21 to the reducing agent injector 25 (direction A). The other flow path direction is the direction in which the urea aqueous solution flows from the reducing agent injector 25 to the tank 21 (direction B). The pump 33 may also be, for example, a pump capable of reversible rotation. The direction A and the direction B can be switched by switching the rotation direction of the pump 33. Furthermore, the pump 33 may be composed of a supply pump that pumps the urea aqueous solution from the tank 21 and pressure-fed it in the direction of the reducing agent injector 25, and a recovery pump that recovers the urea aqueous solution from the reducing agent injector 25 and pressure-fed it in the direction of the tank 21.

[0020] FIG. 2 is a schematic diagram showing an example of the reducing agent injection valve 25. The reducing agent injection valve 25 shown in FIG. 2 includes a connection port 25a, a spring 25b, a coil 25c, a valve body 25d, an injection hole 25e, and a stopper 25f. The connection port 25a is connected to the second passage 52, and the urea aqueous solution is supplied into the reducing agent injection valve 25 through the connection port 25a. The spring 25b is a compression spring that urges the valve body 25d toward the injection hole 25e. The coil 25c is electrically connected to a drive circuit that the control device 100 has. When a drive current is applied to the coil 25c, the valve body 25d is attracted and moves toward the connection port 25a by the generated electromagnetic force. The stopper 25f is a stopper for restricting the movement of the valve body 25d. The reducing agent injection valve 25 may also be provided with a cooling water passage (not shown). The cooling water passage may be formed so that cooling water diverted from the cooling water passage for the internal combustion engine flows through it. The cooling water passage may be provided in contact with the reducing agent injector 25 or within the reducing agent injector 25 so that the temperature of the cooling water affects the temperature of the reducing agent injector 25.

[0021] When the coil 25c is in a non-energized state, the biasing force of the spring 25b and, when the urea aqueous solution is being supplied, the pressure of the urea aqueous solution also act to push the valve body 25d toward the injection hole 25e, closing the injection hole 25e (valve closed). On the other hand, when the coil 25c is switched from a non-energized state to a current-carrying state, the electromagnetic force generated in the coil 25c attracts the valve body 25d toward the connection port 25a against the biasing force of the spring 25b and the like, and the reducing agent injector 25 opens. When the reducing agent injector 25 opens, the urea aqueous solution is injected into the exhaust pipe 11.

[0022] A sliding portion 25g is formed between the valve body 25d and a hole (slide hole) that holds the valve body 25d. Since the radial gap of the sliding portion 25g is very narrow, if this gap is filled with a solid object or the like, the valve body 25d may not respond to a drive command from the control device 100. This phenomenon in which the valve body 25d sticks to the sliding portion 25g and does not operate is referred to as sticking inside the reducing agent injection valve 25.

[0023] For example, after the internal combustion engine is stopped, control is performed to recover the urea aqueous solution in the reducing agent injection valve 25 toward the tank. At that time, if the urea aqueous solution remains in the reducing agent injection valve 25, particularly in the sliding portion 25g, the remaining urea aqueous solution may solidify by the time the internal combustion engine is restarted, which may cause the inside of the reducing agent injection valve 25 to become stuck.

[0024] An exhaust temperature sensor 80 for detecting a temperature Tgas inside the exhaust pipe 11 is attached to the exhaust pipe 11 (see FIG. 1). The exhaust temperature sensor 80 is preferably attached at a position where it can measure the temperature in the vicinity of the reducing agent injector 25. The temperature Tgas detected by the exhaust temperature sensor 80 is acquired by the control device 100.

[0025] A pressure sensor 82 that detects the pressure P in the second passage 52 is attached to the second passage 52 (see FIG. 1). The pressure sensor 82 may be attached to a location in the supply module 31 where the pressure P in the second passage 52 can be detected. The pressure P detected by the pressure sensor 82 is acquired by the control device 100.

[0026] A tank temperature sensor 86 for detecting a temperature Tta of the urea aqueous solution in the tank 21 is attached in the tank 21 (see FIG. 1). The temperature Tta of the urea aqueous solution in the tank 21 detected by the tank temperature sensor 86 is acquired by the control device 100.

[0027] In addition, the control device 100 may be configured to acquire detection values ​​from a coolant temperature sensor 88 that detects the coolant temperature Tcool, an outside air temperature sensor that detects the air temperature around the reducing agent supply device 20, an outside air pressure sensor that detects the air pressure around the reducing agent supply device 20, etc.

[0028] <Control device for reducing agent supply device and control method thereof> The control device 100 of the reducing agent supply device 20 according to the embodiment of the present invention and a control method thereof will be described in detail below. FIG. 3 shows a configuration example in which the parts of the control device 100 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 determination unit 107. Specifically, each of these units is realized by the execution of a program by the microcomputer. The control device 100 may have other configurations.

[0029] In addition, the control device 100 is equipped with memory elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory), not shown, a timer counter, a supply module 31, a drive circuit for controlling the supply of electricity to the reducing agent injection valve 25, and the like.

[0030] The acquisition unit 103 acquires a signal IG from the ignition switch 84, a temperature Tgas detected by the exhaust temperature sensor 80, a temperature Tta of the urea aqueous solution in the tank 21 detected by the tank temperature sensor 86, a pressure P detected by the pressure sensor 82, and a coolant temperature Tcool detected by the coolant temperature sensor 88. Furthermore, the acquisition unit 103 can acquire a current I flowing through the reducing agent injector 25 and a voltage V applied to the reducing agent injector 25. The acquisition unit 103 may be configured to acquire information from devices other than these. The acquired information is sent to the control unit 105 and / or the determination unit 107.

[0031] The control unit 105 executes various calculation processes based on the information of the acquisition unit 103 and the determination unit 107, and controls the driving of the reducing agent injection valve 25, the supply module 31, etc. The control unit 105 may be configured to perform other controls.

[0032] The determination unit 107 performs various determinations within the control device 100. For example, the determination unit 107 makes determinations regarding the signal IG from the ignition switch 84, the temperature Tgas detected by the exhaust temperature sensor 80, the temperature Tta of the urea aqueous solution in the tank 21 detected by the tank temperature sensor 86, the pressure P detected by the pressure sensor 82, the temperature Tcool of the cooling water detected by the cooling water temperature sensor 88, the current flowing through the reducing agent injector 25, the temperature of the coil 25c, and the time t. The determination unit 107 may make determinations regarding other information.

[0033] The acquisition unit 103, the control unit 105, and the determination unit 107 may be configured to share information.

[0034] The operations of the acquisition unit 103, the control unit 105, and the determination unit 107 will be further described with reference to the flow chart of FIG.

[0035] The operation of the control device 100 of the reducing agent supply device 20 according to the present invention is performed when the internal combustion engine 1 is restarted. Before describing this, the control of recovering the urea aqueous solution in the reducing agent injection valve 25 toward the tank 21, which is performed after the internal combustion engine 1 is stopped, will be described using the flowchart of FIG. 4. The control device 100 of the reducing agent supply device 20 according to the present invention may be configured to perform the control including the control of recovering the urea aqueous solution toward the tank 21. When the urea aqueous solution, which is a reducing agent, freezes, its volume increases. For this reason, when the environmental temperature drops after the internal combustion engine is stopped, the reducing agent in the reducing agent injection valve 25 freezes, and this freezing may cause malfunctions such as damage. The recovery of the reducing agent is performed to avoid these malfunctions.

[0036] In step S10, the acquisition unit 103 acquires the signal IG from the ignition switch 84 and sends it to the determination unit 107. The determination unit 107 determines whether or not the ignition switch 84 has been turned off. If the ignition switch 84 has been turned off, the process proceeds to step S20, and if the ignition switch 84 has been turned on, the process returns to step S10.

[0037] In step S20, the control unit 105 closes the reducing agent injector 25 by de-energizing it, and operates the supply module 31 so that the urea aqueous solution moves in a direction (direction B) from the reducing agent injector 25 toward the tank 21. As a result, the pressure P in the reducing agent injector 25 and the second passage 52 starts to decrease. After step S20, the process proceeds to step S30.

[0038] In step S30, 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 S40, and if the pressure P is higher than the first predetermined pressure Pth1, the process returns to step S30. The first predetermined pressure Pth1 is, for example, a pressure lower than the pressure in the exhaust pipe when the internal combustion engine is stopped. By setting the pressure P in the second passage 52 to such a pressure, when the reducing agent injection valve 25 is opened in the next step, the air (including exhaust gas) in the exhaust pipe flows into the opening of the reducing agent injection valve 25. Therefore, when the reducing agent injection valve 25 is opened, there is no risk of the urea aqueous solution leaking from the opening of the reducing agent injection valve 25. For example, the pressure in the exhaust pipe when the internal combustion engine is stopped is atmospheric pressure or a pressure close to atmospheric pressure.

[0039] In step S40, the control unit 105 energizes the reducing agent injector 25 to open it. Since the supply module 31 continues to control the urea aqueous solution to move in the direction from the reducing agent injector 25 toward the tank 21 (direction B), the reducing agent injector 25 and the urea aqueous solution in the second passage 52 move toward the tank 21 via the supply module 31. Accompanying this movement of the urea aqueous solution, air flows in from the opening of the reducing agent injector 25.

[0040] In step S50, the determination unit 107 determines whether the urea aqueous solution has been sufficiently recovered. For example, whether the urea aqueous solution has been sufficiently recovered is determined based on whether the time t1 after the reducing agent injector 25 is opened (step S50) is equal to or longer than a first predetermined time tp1. If the time after the reducing agent injector 25 is opened reaches the first predetermined time tp1, the process proceeds to step S60, and if the time after the reducing agent injector 25 is opened does not reach the first predetermined time tp1, the process returns to step S50. The first predetermined time tp1 can be determined by a prior experiment or the like.

[0041] In step S60, the control unit 105 de-energizes the reducing agent injector 25, closes it, and stops the operation of the supply module 31.

[0042] As described above, by the recovery control executed after the internal combustion engine 1 is stopped, even if the environmental temperature drops thereafter, it is possible to prevent the urea aqueous solution in the reducing agent injector 25 from freezing and causing breakdowns such as damage. However, after the recovery control, a small amount of urea aqueous solution may remain in the sliding portion 25g, which is a narrow gap in the reducing agent injector 25. The remaining urea aqueous solution may solidify, causing the reducing agent injector 25 to stick and malfunction. The mechanism behind this is described below.

[0043] FIG. 8 is a phase diagram of a urea aqueous solution (reducing agent). The horizontal axis is the concentration (%) of the urea aqueous solution, and the vertical axis is temperature (°C). When the concentration of the urea aqueous solution is 32.5%, the urea aqueous solution can maintain its liquid state at the lowest temperature (-11°C). A new urea aqueous solution is prepared at this concentration of 32.5%. On the other hand, when the concentration becomes higher than 32.5%, the temperature at which the liquid state can be maintained also increases. In FIG. 8, the boundary at which the liquid state can be maintained is indicated by the boundary line Lf. In FIG. 8, the boundary line Lg is also indicated further above the boundary line Lf, which is the boundary between gas and liquid. Therefore, the urea aqueous solution in the region between the boundary line Lf and the boundary line Lg exists as a liquid. On the other hand, below the boundary line Lf on the higher temperature side, the urea aqueous solution exists in an intermediate state between liquid and solid, for example, in a gel or gel-like state. As the temperature becomes lower, the flexibility decreases and the solution becomes more solid. In this specification, the solidification of the urea aqueous solution is expressed to include gel and gel-like states. Therefore, the urea aqueous solution is in a solidified state below the boundary line Lf.

[0044] As described above, after the control for recovering the urea aqueous solution in the direction of the tank 21 is performed, the urea aqueous solution may remain in the reducing agent injection valve 25. The initial concentration of the residual urea aqueous solution is about 32.5%. As an example, the initial state of the residual urea aqueous solution is U1 (temperature T1, concentration C1 = 32.5%) and plotted in FIG. 8. After the internal combustion engine is stopped, moisture may evaporate due to heat from the exhaust pipe 11, etc., and the concentration of the residual urea aqueous solution may increase. As an example of the state of the residual urea aqueous solution with the increased concentration, U2 (temperature T2, concentration C2) is plotted in FIG. 8. Here, since U2 is below the boundary line Lf, the residual urea aqueous solution is in a solidified state. In particular, when a certain amount of the urea aqueous solution remains in the sliding portion 25g and solidifies, there is a risk of the reducing agent injection valve 25 sticking. The above is the mechanism by which the urea aqueous solution remaining in the reducing agent injection valve 25 solidifies after the recovery control, causing the reducing agent injection valve 25 to stick and malfunction.

[0045] The operation of the control device 100 for the reducing agent supply device 20 according to the present invention will be described with reference to the flowchart of FIG.

[0046] In step S110, acquisition unit 103 acquires signal IG from ignition switch 84 and sends it to determination unit 107. Determination unit 107 determines whether or not ignition switch 84 is turned on. If ignition switch 84 is turned on, the process proceeds to step S120, and if ignition switch 84 is turned off, the process returns to step S110.

[0047] In step S120, the control unit 105 applies a drive current to (the coil 25c of) the reducing agent injector 25. The drive current is a current of a magnitude that, when applied to the reducing agent injector 25 in which no sticking has occurred, causes the valve body 25d to move in the direction of the connection port 25a by the generated electromagnetic force.

[0048] In step S130, the acquisition unit 103 acquires the current flowing through the reducing agent injector 25 and sends it to the judgment unit 107. The judgment unit 107 checks the current waveform within a predetermined time and judges whether there is a change point BIP in the current waveform. If there is no change point BIP (YES), the process proceeds to step S140, and if there is a change point BIP (NO), the process proceeds to step S330. FIG. 6 is an example of a current waveform detected when no sticking occurs in the reducing agent injector 25 (horizontal axis: time t, vertical axis: current I). The current waveform is characterized in that a change point BIP appears in the middle of the increasing current. This is due to the back electromotive force when the valve body 25d starts to move. On the other hand, FIG. 7 is an example of a current waveform detected when sticking occurs in the reducing agent injector 25 (horizontal axis: time t, vertical axis: current I). Since the valve body 25d does not move, no back electromotive force is generated and no change point BIP appears.

[0049] In step S140, control unit 105 starts timer A and timer B, and the process proceeds to step S150.

[0050] In step S150, the control unit 105 applies a heating current to the reducing agent injector 25 (the coil 25c of the reducing agent injector 25). The heating current is a current of a magnitude that does not move the valve body 25d due to the generated electromagnetic force even if the heating current is applied to the reducing agent injector 25 in which no sticking has occurred. The coil 25c generates heat due to the heating current, and the temperature of the reducing agent injector 25 can be increased. In the case where the sticking in the reducing agent injector 25 is caused by the solidification of the remaining urea aqueous solution, the solidified urea aqueous solution can be liquefied by increasing the temperature of the reducing agent injector 25, and the sticking in the reducing agent injector 25 can be eliminated. After step S150, the process proceeds to step S170. Note that after step S150 and before step S170, a control may be inserted so that the temperature of the coil 25c does not exceed the melting temperature of urea. The measurement of the temperature of the coil 25c will be described later.

[0051] In step S170, the judgment unit 107 judges whether or not the timer A is equal to or greater than the first predetermined time TM1. If the timer A is equal to or greater than the first predetermined time TM1, the process proceeds to step S180, and if the timer A is shorter than the first predetermined time TM1, the process returns to step S170.

[0052] In step S180, the control unit 105 applies a drive current to the reducing agent injector 25 (the coil 25c thereof).

[0053] In step S190, the acquisition unit 103 acquires the current flowing through the reducing agent injector 25 and sends it to the judgment unit 107. The judgment unit 107 checks the current waveform within a predetermined time and judges whether there is a change point BIP in the current waveform. If there is no change point BIP (YES), the process proceeds to step S200, and if there is a change point BIP (NO), the process proceeds to step S300. Here, a case where there is no change point BIP means that the sticking in the reducing agent injector 25 has not yet been resolved. Also, a case where there is a change point BIP means that the sticking in the reducing agent injector 25 has been resolved by the heating current.

[0054] Here, the state of the urea aqueous solution when sticking occurs in the reducing agent injector 25 when the internal combustion engine is restarted is, for example, U2 (temperature T2, concentration C2) in FIG. 8, and an example of the state of the residual urea aqueous solution when the sticking in the reducing agent injector 25 is subsequently resolved by the current flow is plotted as U3 (temperature T3, concentration C3) in FIG. 8. Since U3 is above the boundary line Lf, this residual urea aqueous solution (U3) is in a liquid state. This means that the sticking in the reducing agent injector 25 has also been resolved. With the residual urea aqueous solution in this state (U3), the process proceeds to step S300.

[0055] In step S200, the control unit 105 resets and restarts the timer A. When the first predetermined time TM1 is 30 seconds, it is confirmed approximately every 30 seconds whether or not the sticking in the reducing agent injector 25 has been resolved.

[0056] In step S210, the judgment unit 107 judges whether or not the timer B is equal to or greater than the second predetermined time TM2. If the timer B is equal to or greater than the second predetermined time TM2, the process proceeds to step S220, and if the timer B is shorter than the second predetermined time TM2, the process returns to step S160. The second predetermined time TM2 is, for example, 600 seconds.

[0057] In step S220, the control unit 105 stops the supply of the heating current to the reducing agent injector 25 (the coil 25c thereof). This is because it is estimated that the sticking inside the reducing agent injector 25 is likely not due to the solidified residual urea aqueous solution but is due to some other cause, and the sticking inside the reducing agent injector 25 cannot be expected to be resolved even if the supply of the heating current is continued any further.

[0058] In step S230, the control unit 105 reports that an error has occurred and ends the flow. The control unit 105 may be configured to inform the driver of the vehicle that an error has occurred.

[0059] Next, the operation of the control device 100 for the reducing agent supply device 20 after step S300 will be described.

[0060] In step S300, the control unit 105 determines the threshold temperature Tth, and proceeds to step S310. As described above, if the state of the residual urea aqueous solution when proceeding to step S300 is U3 (concentration C3, temperature T3), the threshold temperature Tth is higher than T3.

[0061] In step S310, the acquisition unit 103 acquires the current I flowing through the coil 25c and the voltage V applied to the coil 25c, and sends them to the determination unit 107. The determination unit 107 calculates the resistance value of the coil 25c from the current I and voltage V, and calculates the temperature of the coil 25c from the relationship between the resistance value and temperature. The determination unit 107 determines whether the calculated temperature of the coil 25c is equal to or lower than the threshold temperature Tth. If the temperature of the coil 25c is equal to or lower than the threshold temperature Tth (YES), the process returns to step S310, and if the temperature of the coil 25c exceeds the threshold temperature Tth (NO), the process proceeds to step S320.

[0062] In step S320, the heating energization is stopped. Then, the flow proceeds to step S330, the urea aqueous solution is filled into the reducing agent injector 25, and the pressure in the reducing agent injector 25 is increased to the system pressure, and the flow ends. After the pressure in the reducing agent injector 25 is increased to the system pressure, the control device 100 starts supplying the reducing agent into the exhaust pipe 11. Specifically, the control unit 105 controls the reducing agent injector 25 and the supply module 31 so that the amount of reducing agent to be supplied becomes a target reducing agent amount calculated separately. The target reducing agent amount may be determined based on the combustion conditions of the internal combustion engine 1, including, for example, the combustion temperature, the intake air amount, the fuel supply amount, and the like. In addition to this, the target reducing agent amount may be determined in consideration of the amount of reducing agent absorbed and stored in the reduction catalyst 13.

[0063] In this way, the control device 100 and the control method of the reducing agent supply device 20 according to the embodiment of the present invention are configured to raise the temperature from the temperature T3 at which the adhesion in the reducing agent injection valve 25 is resolved to the threshold temperature Tth, which is a higher temperature. If the temperature increase is stopped and the filling of the urea aqueous solution is started immediately after the adhesion in the reducing agent injection valve 25 is resolved, for example, there is a risk that the temperature of the residual urea aqueous solution will drop and solidify again depending on the urea aqueous solution introduced from the tank 21 thereafter. Therefore, in the present invention, the temperature is raised from the temperature T3 at which the adhesion in the reducing agent injection valve 25 is resolved to the threshold temperature Tth, which is a higher temperature, and then the filling of the urea aqueous solution is started. Therefore, even if the temperature of the residual urea aqueous solution drops due to the urea aqueous solution introduced from the tank 21, there is no risk of it solidifying again. For example, the threshold temperature Tth may be determined so that the temperature T4 (not shown) after it has been lowered due to the introduction of the urea aqueous solution introduced from the tank 21 is above the boundary line Lf.

[0064] For example, the threshold temperature Tth may be the melting temperature of urea, which is approximately 130° C. If the temperature of the residual urea aqueous solution is raised to the melting temperature of urea, the residual urea aqueous solution is gasified, and there is no risk of the residual urea aqueous solution solidifying again even if the temperature drops slightly thereafter.

[0065] For example, the threshold temperature Tth may be determined based on the temperature Tta of the urea aqueous solution in the tank 21. When the temperature Tta of the urea aqueous solution introduced from the tank 21 is low, the threshold temperature Tth may be set high since the effect on the temperature decrease of the residual urea aqueous solution is large, and when the temperature Tta of the urea aqueous solution introduced from the tank 21 is high, the effect on the temperature decrease of the residual urea aqueous solution is small, so the threshold temperature Tth may be set low. The threshold temperature Tth may be determined based on the temperature T3 when the sticking in the reducing agent injection valve 25 is resolved and the temperature Tta of the urea aqueous solution in the tank 21. For example, the temperature Tta of the urea aqueous solution in the tank 21 is detected by the tank temperature sensor 86.

[0066] For example, the threshold temperature Tth may be determined based on the temperature Tgas in the exhaust pipe 11. When the temperature Tgas in the exhaust pipe 11 is low, the threshold temperature Tth is set high since the influence on the temperature decrease of the residual urea aqueous solution is large. On the other hand, when the temperature Tgas in the exhaust pipe 11 is high, the influence on the temperature decrease of the residual urea aqueous solution is small, so the threshold temperature Tth may be set low. The threshold temperature Tth may be determined based on the temperature T3 when the sticking in the reducing agent injector 25 is resolved and the temperature Tgas in the exhaust pipe 11. The temperature Tgas in the exhaust pipe 11 is detected by the exhaust temperature sensor 80.

[0067] For example, the threshold temperature Tth may be determined based on the coolant temperature Tcool. When the coolant temperature Tcool is low, the influence on the temperature decrease of the residual urea aqueous solution is large, so the threshold temperature Tth may be set high, and when the coolant temperature Tcool is high, the influence on the temperature decrease of the residual urea aqueous solution is small, so the threshold temperature Tth may be set low. The threshold temperature Tth may be determined based on the temperature T3 when the sticking inside the reducing agent injection valve 25 is resolved and the coolant temperature Tcool. For example, the coolant temperature Tcool is detected by the coolant temperature sensor 88.

[0068] For example, the threshold temperature Tth may be determined based on at least two of the temperature Tta of the urea aqueous solution in the tank 21, the temperature Tgas in the exhaust pipe 11, and the temperature Tcool of the coolant. The threshold temperature Tth can be determined by taking into consideration the magnitude of the influence of each of the temperature Tta of the urea aqueous solution in the tank 21, the temperature Tgas in the exhaust pipe 11, and the temperature Tcool of the coolant. Therefore, the threshold temperature Tth may be determined based on the temperature T3 when the sticking in the reducing agent injector 25 is resolved, and at least two of the temperature Tta of the urea aqueous solution in the tank 21, the temperature Tgas in the exhaust pipe 11, and the temperature Tcool of the coolant.

[0069] As described above, according to the present invention, when the residual urea aqueous solution in the reducing agent injector 25 is solidified at the start of the internal combustion engine 1, the solidification of the urea aqueous solution is eliminated by passing current through the coil 25c of the reducing agent injector 25, and current is continued to be passed through the coil 25c until the coil 25c reaches the threshold temperature Tth. This makes it possible to provide a reducing agent supplying device 20, a control device 100 for the reducing agent supplying device 20, and a control method thereof that are capable of preventing subsequent re-solidification.

[0070] 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]

[0071] 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, 25a connection port, 25b spring, 25c coil, 25d valve body, 25e injection hole, 25f stopper, 31 supply module, 33 pump, 41 51 first passage, 52 second passage, 53 third passage, 80 exhaust temperature sensor, 82 pressure sensor, 84 ignition switch, 86 tank temperature sensor, 88 cooling water temperature sensor, 100 control device, 103 acquisition unit, 105 control unit, 107 judgment unit

Claims

1. A control device (100) for a reducing agent supply device (20) that fills the device with a urea aqueous solution as a reducing agent at the start of an internal combustion engine (1) and controls a reducing agent injection valve (25) to inject the urea aqueous solution into an exhaust pipe (11) of the internal combustion engine (1), A control device (100) for a reducing agent supply device (20), which energizes a coil (25c) of the reducing agent injection valve (25) to eliminate sticking in the reducing agent injection valve (25), and continues to energize the coil (25c) until the coil (25c) reaches a threshold temperature (Tth) after the sticking of the reducing agent injection valve (25) is eliminated.

2. The control device for a reducing agent supply device according to claim 1 , wherein the threshold temperature (Tth) is a melting temperature of urea.

3. 2. The control device for a reducing agent supply device according to claim 1, wherein the threshold temperature (Tth) is determined based on a temperature (Tta) of an aqueous urea solution in a tank that is supplied to the reducing agent injection valve (25).

4. 2. The control device for a reducing agent supply device according to claim 1, wherein the threshold temperature (Tth) is determined based on a temperature (Tgas) in the exhaust pipe (11).

5. The control device for a reducing agent supply device according to claim 1 , wherein the threshold temperature (Tth) is determined based on a coolant temperature (Tcool).

6. 2. The control device for a reducing agent supply device according to claim 1, wherein the threshold temperature (Tth) is determined based on at least two of a temperature (Tta) of the urea aqueous solution in a tank supplied to the reducing agent injection valve (25), a temperature (Tgas) in the exhaust pipe (11), and a cooling water temperature (Tcool).

7. A reducing agent supply device (20) having a control device (100) for the reducing agent supply device (20) according to any one of claims 1 to 6.

8. A method for controlling a reducing agent supply device (20) for filling the device with a urea aqueous solution as a reducing agent at the start of an internal combustion engine (1) and controlling a reducing agent injection valve (25) to inject the urea aqueous solution into an exhaust pipe (11) of the internal combustion engine (1), comprising: energizing a coil (20c) of the reducing agent injection valve (25) to eliminate sticking in the reducing agent injection valve (25); a step of continuing to energize the coil (20c) until the coil (20c) reaches a threshold temperature (Tth) after the sticking of the reducing agent injection valve (25) is resolved; A method for controlling a reducing agent supply device (20).

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