JP2014177883A - Control method of reductant supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a reductant supply device for efficiently executing movement for dissolving such a state that an opening and closing movement of a reductant injection valve is impossible in the starting of an internal combustion engine.SOLUTION: In a control method of a reductant supply device for controlling the reductant supply device which is configured so as to recover remaining liquid reductant into a storage tank upon stoppage of an internal combustion engine, a primary estimation with respect to availability of the opening and closing movement of a reductant ejection valve is performed based on the state of preceding internal combustion engine stoppage, when it is estimated that the opening and closing movement is impossible as the result of the primary estimation, the reductant injection valve is driven a plurality of times to perform secondary determination with respect to availability of the opening and closing movement of the reductant injection valve and, when it is determined that the opening and closing movement is impossible as the result of secondary determination, melting control of the liquid reductant on the reductant injection valve is executed.

Description

  The present invention relates to a control method for a reducing agent supply device for controlling a reducing agent supply device for supplying an ammonia-derived liquid reducing agent to an exhaust passage of an internal combustion engine.

Nitrogen oxides (NO _x ) are contained in the exhaust of internal combustion engines such as diesel engines mounted on vehicles and the like. As one of exhaust purifying apparatus for purifying the NO _X, the selective reduction catalyst disposed in an exhaust passage of an internal combustion engine, for injecting liquid reducing agent from ammonia, such as urea aqueous solution on the upstream side of the selective reduction catalyst There is known an exhaust emission control device including a reducing agent supply device. This exhaust purification device efficiently reduces NO _x and ammonia in exhaust in a selective reduction catalyst and decomposes NO _x into nitrogen or water.

  As one aspect of the reducing agent supply device used in such an exhaust purification device, a reducing agent injection device that includes a pump and a reducing agent injection valve, pumps the liquid reducing agent in the storage tank by the pump, and is fixed to the exhaust pipe. There is a direct injection type reducing agent supply device that supplies liquid reducing agent into an exhaust pipe through a valve.

  Here, when the urea aqueous solution is used as the liquid reducing agent, the urea aqueous solution having the lowest freezing temperature is used so that the urea aqueous solution is not frozen as much as possible. However, the freezing temperature of the aqueous urea solution is about −11 ° C. even at a low temperature, and the aqueous urea solution may freeze in a cold region or the like during a period when the supply of the aqueous urea solution by the reducing agent supply device is stopped. Further, even when water in the urea aqueous solution evaporates and the concentration increases, the freezing temperature of the urea aqueous solution may rise and freeze.

  If the urea aqueous solution is frozen, the pump and the reducing agent injection valve cannot be operated normally, so that a long thawing time may be required at the next start. Therefore, when the internal combustion engine is stopped, control is generally performed to recover the urea aqueous solution remaining in the reducing agent supply device into the storage tank. To recover the urea aqueous solution, reverse the rotation of the pump that pumps the urea aqueous solution, or switch the connection of the urea aqueous solution flow path to depressurize the urea aqueous solution supply passage, and store the urea aqueous solution on the storage tank side. Done by sending to. (For example, see Patent Document 1).

JP 2010-007617 A (paragraphs [0037], [0047], etc.)

  However, even if the liquid reducing agent recovery control is executed, it may be difficult to completely recover the liquid reducing agent inside the reducing agent injection valve. In particular, the recovery control of the liquid reducing agent is performed while opening the reducing agent injection valve and taking in air (exhaust gas) in the exhaust passage into the reducing agent supply device. During the recovery control, the reducing agent injection is performed. In some cases, the water in the liquid reducing agent adhering to the vicinity of the nozzle hole of the valve is heated by residual exhaust heat and evaporated to crystallize, resulting in clogging of the nozzle hole. When the nozzle hole is clogged, it becomes more difficult to completely recover the liquid reducing agent in the reducing agent injection valve. If the opening / closing operation of the reducing agent injection valve is not performed due to crystallization of the liquid reducing agent at the time of starting the internal combustion engine, it is necessary to quickly resolve this.

  Therefore, the present invention provides a control method for a reducing agent supply apparatus for efficiently executing an operation for eliminating a state where the opening / closing operation of the reducing agent injection valve is impossible at the time of starting the internal combustion engine. It is an object.

  According to the present invention, during operation of the internal combustion engine, the liquid reducing agent in the storage tank is pumped by the pump and supplied to the reducing agent injection valve, and the liquid is introduced into the exhaust passage of the internal combustion engine by the reducing agent injection valve. In a control method of a reducing agent supply device for controlling a reducing agent supply device configured to inject a reducing agent while recovering the remaining liquid reducing agent into the storage tank when the internal combustion engine is stopped. When the internal combustion engine is started, a primary estimation is made as to whether or not the reducing agent injection valve can be opened and closed based on the previous state when the internal combustion engine was stopped. As a result of the primary estimation, it is estimated that the opening and closing operation is impossible. In such a case, the reducing agent injection valve is driven a plurality of times to make a secondary determination as to whether or not the reducing agent injection valve can be opened and closed. As a result of the secondary determination, it is determined that the opening and closing operation is impossible. In case, before Is provided a control method of the reducing agent supply apparatus characterized by performing said melting control of the liquid reducing agent in the reducing agent injection valve, it is possible to solve the problems described above.

  That is, according to the control method of the reducing agent supply apparatus of the present invention, after performing the primary estimation based on the previous state when the internal combustion engine was stopped and the secondary determination based on the driving state of the reducing agent injection valve, the reduction is performed. Only when it is determined that the opening / closing operation of the agent injection valve is impossible, the melting control of the liquid reducing agent is executed. Therefore, melting control is executed only when the possibility of crystallization of the liquid reducing agent is extremely high, so unnecessary melting control is omitted, and efficiency of melting control is achieved.

  Further, in carrying out the control method of the reducing agent supply apparatus of the present invention, the secondary determination is performed based on a waveform of a current flowing through the reducing agent injection valve when the reducing agent injection valve is driven. preferable. By executing the secondary determination in this way, it is possible to determine whether or not the reducing agent injection valve can be opened and closed without increasing the number of additional devices.

  Moreover, when implementing the control method of the reducing agent supply apparatus of this invention, it is preferable to perform the said melting control by driving the said reducing agent injection valve in multiple times and making the inside of the said reducing agent injection valve generate heat | fever. If the melting control is executed in this way, the crystallization of the liquid reducing agent generated in the reducing agent injection valve can be eliminated without increasing the number of additional devices. Further, since this melting control is executed only when the possibility of crystallization of the liquid reducing agent is extremely high, the number of times that the liquid reducing agent is executed before reaching the reducing agent injection valve is assumed. Therefore, the risk of damage to the seat portion of the reducing agent injection valve can be reduced.

  Further, when performing the control method of the reducing agent supply apparatus of the present invention, the secondary determination is performed again after the melting control is performed, and the opening / closing operation is not possible even if the melting control is repeated a predetermined number of times. It is preferable to determine that the reducing agent injection valve has a permanent failure. By determining the permanent failure in this way, when the reducing agent injection valve is not fixed due to the crystallization of the liquid reducing agent, the driver can be urged to take measures. .

  In carrying out the control method of the reducing agent supply apparatus of the present invention, the primary estimation is based on the crystallization of the liquid reducing agent in the reducing agent injection valve based on the exhaust temperature when the internal combustion engine was stopped last time. It is preferable to estimate the possibility. By performing the primary estimation in this way, the next secondary determination is performed when the internal combustion engine is stopped in a state where crystallization of the liquid reducing agent is likely to occur, and the possibility of crystallization of the liquid reducing agent is likely to occur. Can be accurately determined.

It is a general view which shows an example of the exhaust gas purification apparatus provided with the reducing agent supply apparatus. It is a block diagram which shows the structural example of the electronic controller which performs the control method of a reducing agent supply apparatus. It is a figure which shows an example of the map used for primary estimation. It is a figure shown in order to demonstrate secondary determination. It is a flowchart which shows an example of the control method of the reducing agent supply apparatus concerning this Embodiment.

Embodiments relating to a control method for a reducing agent supply apparatus of the present invention will be specifically described below with reference to the drawings as appropriate.
In addition, in each figure, about the thing which attached | subjected the same code | symbol, the same member is shown unless there is particular description, and description is abbreviate | omitted suitably.

1. Overall Configuration of Exhaust Gas Purification Device FIG. 1 is a diagram shown for explaining an example of the overall configuration of an exhaust gas purification device 10 provided with a reducing agent supply device 20.
The exhaust purification device 10 is a device for purifying NO _x in exhaust gas, and is provided in an exhaust passage 11 of an internal combustion engine such as a diesel engine (not shown). The exhaust purification device 10 includes a reduction catalyst 13 interposed in the middle of the exhaust passage 11 and a reducing agent supply device 20 for supplying a liquid reducing agent into the exhaust passage 11 upstream of the reduction catalyst 13. ing. In FIG. 1, an arrow written in the exhaust passage 11 indicates a direction in which the exhaust flows.

The reduction catalyst 13 is a catalyst having a function of promoting the reduction of NO _{x in} the exhaust, adsorbs the reducing component generated from the liquid reducing agent, and selectively reduces the NO _x in the exhaust flowing into the catalyst by the reducing component. It is a catalyst that reduces to The reducing agent supply device 20 uses a urea aqueous solution as a liquid reducing agent, and ammonia as a reducing component is generated when the urea aqueous solution is decomposed in the exhaust passage 11. An exhaust temperature sensor 15 is provided upstream of the reduction catalyst 13 and further upstream of the reducing agent supply device 20.

2. 1. Reducing agent supply device (1) Basic configuration In FIG. 1, a reducing agent supply device 20 includes a storage tank 21 in which a liquid reducing agent is stored, a pump unit 30 for pumping the liquid reducing agent, and a liquid reducing agent. And a reducing agent injection valve 25 for injecting into the exhaust passage 11. The pump unit 30 includes a pump 23 and a flow path switching valve 33. The reducing agent injection valve 25, the pump 23, and the flow path switching valve 33 are controlled by an electronic control unit (ECU) 40.

  The pump 23 and the storage tank 21 are connected by a first supply passage 27, and the pump 23 and the reducing agent injection valve 25 are connected by a second supply passage 28. Among these, the second supply passage 28 is provided with a pressure sensor 31 for detecting the pressure in the second supply passage 28, that is, the pressure of the liquid reducing agent fed to the reducing agent injection valve 25. Yes. The pump 23 is connected to the first supply passage 27 and the second supply passage 28 via a flow path switching valve 33. The end of the first supply passage 27 on the side of the storage tank 21 is located in the vicinity of the bottom surface of the storage tank 21 so that the liquid reducing agent can be sucked up.

  The flow path switching valve 33 has a direction in which the liquid reducing agent pumped by the pump 23 flows from the storage tank 21 side to the reducing agent injection valve 25 side (hereinafter referred to as “positive direction”), and a reducing agent injection valve. It has a function of switching from the 25 side to the direction of flowing to the storage tank 21 side (hereinafter referred to as “reverse direction”). In the reducing agent supply device 20, the flow path switching valve 33 communicates the first supply passage 27 to the inlet side 23 a of the pump 23 and the second supply passage 28 to the outlet side 23 b of the pump 23 in a non-energized state. On the other hand, the first supply passage 27 communicates with the outlet side 23b of the pump 23 and the second supply passage 28 communicates with the inlet side 23a of the pump 23 in an energized state.

  That is, when the liquid reducing agent injection control is performed, the flow path switching valve 33 is not energized in order to supply the liquid reducing agent to the reducing agent injection valve 25 side. At this time, the liquid reducing agent flows in the positive direction. On the other hand, when the internal combustion engine is stopped, when the liquid reducing agent in the reducing agent supply device 20 is collected in the storage tank 21, the flow path switching valve 33 is energized. At this time, the liquid reducing agent flows in the reverse direction.

  The configuration that enables the liquid reducing agent to be collected in the storage tank 21 is not limited to the example in which the flow path switching valve 33 is provided. For example, the liquid reducing agent can be configured to be recoverable by using a pump 23 that can rotate in reverse.

In addition, a return passage 29 having the other end connected to the storage tank 21 is provided in the middle of the second supply passage 28. The end of the return passage 29 on the storage tank 21 side is connected to a gas phase portion in the storage tank 21 in order to prevent the back flow of the liquid reducing agent. The position where the return passage 29 branches may be not the middle of the second supply passage 28 but the outlet side 23 b of the pump 23.
The storage tank 21 is provided with an air blizzard or the like, and is configured so that the internal pressure is maintained at atmospheric pressure.

  In the middle of the return passage 29, a throttle portion 37 having a reduced flow passage area is provided so that the pressure in the second supply passage 28 can be maintained. The return passage 29 closer to the storage tank 21 than the throttling portion 37 is provided with a one-way valve 35 for preventing the liquid reducing agent from flowing from the storage tank 21 side to the second supply passage 28 side. Yes. The one-way valve 35 may be omitted.

  In the reducing agent supply device 20 shown in FIG. 1, the pressure sensor 31 is provided in the pump unit 30, but at any position as long as the pressure in the second supply passage 28 can be detected. It does not matter.

  The pump 23 pumps a liquid reducing agent at a predetermined flow rate by energization control by the ECU 40. In the reducing agent supply apparatus 20 of FIG. 1, an electromagnetic pump is used as the pump 23, and the output (discharge flow rate) of the pump 23 increases as the drive duty ratio increases. The pump 23 also has a function as a means for recovering the liquid reducing agent in the storage tank 21.

  In the operating state of the internal combustion engine, the reducing agent injection valve 25 is controlled to be opened and closed by energization control by the ECU 40 and injects a predetermined amount of liquid reducing agent into the exhaust passage 11. The reducing agent injection valve 25 is an electromagnetic on / off valve that closes in a non-energized state and opens in an energized state. The ECU 40 obtains the target injection amount Qdv_tgt based on a predetermined arithmetic expression, and assumes that the detected pressure Pu in the second supply passage 28 is the target pressure Pu_tgt for each predetermined injection cycle. Then, the drive duty ratio corresponding to the target injection amount Qdv_tgt is determined, and energization control of the reducing agent injection valve 25 is performed. The drive duty ratio of the reducing agent injection valve 25 means the ratio of the valve opening time during one injection cycle.

  On the other hand, the reducing agent injection valve 25 is maintained in a state in which the reducing agent injection valve 25 is opened when recovering the liquid reducing agent when the internal combustion engine is stopped. As a result, air (exhaust gas) is introduced into the second supply passage 28 through the nozzle hole of the reducing agent injection valve 25, and the liquid reducing agent is easily collected in the storage tank 21.

3. Electronic control unit (ECU)
(1) Configuration of Electronic Control Unit FIG. 2 shows a configuration example in which a part related to control executed when the internal combustion engine is stopped and started in the ECU 40 is represented by functional blocks.
The ECU 40 is configured around a known microcomputer, and includes a pump control unit 41, a reducing agent injection valve control unit 43, a flow path switching valve control unit 45, a primary estimation unit 47, and a secondary. The determination part 49, the collection | recovery control part 51, and the melting control part 53 are comprised. Specifically, each of these units is realized by executing a program by a microcomputer.

  In addition to this, the ECU 40 has control of energization to a memory element (not shown) such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a timer counter, the pump 23, the flow path switching valve 33, and the reducing agent injection valve 25. A drive circuit and the like are provided. The ECU 40 receives an on / off signal of a key switch of the internal combustion engine and sensor signals of the pressure sensor 31 and the exhaust temperature sensor 15, and stores values such as the detected pressure Pu and the exhaust temperatures Temp_g and Temp_e in a storage element. It is like that.

  Among these, the recovery control unit 51 issues a command to start recovery control of the liquid reducing agent when the key switch of the internal combustion engine is turned off from on.

  During the operation of the internal combustion engine, the pump control unit 41 feedback-controls the output of the pump 23 such that the detected pressure Pu detected by the pressure sensor 31 becomes a predetermined target pressure. Further, when the internal combustion engine is stopped, when the recovery control unit 51 issues a start command for the recovery control of the liquid reducing agent triggered by the key switch of the internal combustion engine being turned off, The drive of the pump 23 is controlled with an output that varies as appropriate.

During the operation of the internal combustion engine, the reducing agent injection valve control unit 43 responds to the required injection amount of the liquid reducing agent obtained based on the amount of ammonia that can be adsorbed by the reduction catalyst 13 and the amount of NO _{x in} the exhaust gas. The energization time of the reducing agent injection valve 25 is controlled. Further, when the internal combustion engine is stopped, when the recovery control unit 51 issues a liquid reductant recovery control start command, the reductant injection valve 25 is opened, and during the liquid reductant recovery control, Air (exhaust gas) is introduced into the reducing agent supply path. In addition to this, the reducing agent injection valve control unit 43 performs predetermined energization control on the reducing agent injection valve 25 in accordance with a command from the secondary determination unit 49 or the melting control unit 53.

  The flow path switching valve controller 45 keeps the flow path switching valve 33 in a non-energized state during operation of the internal combustion engine so that the liquid reducing agent pumped by the pump 23 flows in the forward direction. On the other hand, when the internal combustion engine is stopped, when the recovery control unit 51 issues a command to start recovery control of the liquid reducing agent, the liquid switching agent 33 is energized and is pumped by the pump 23. To flow in the opposite direction.

  The primary estimation unit 47 estimates whether or not the reducing agent injection valve 25 can be opened and closed based on the previous state when the internal combustion engine was stopped when the internal combustion engine was started, that is, when the key switch was turned on. To do. For example, based on the exhaust temperature Temp_g when the key switch was turned off at the time of the previous stop of the internal combustion engine, the time Ts from the previous stop of the internal combustion engine to the start of the current internal combustion engine, etc. It is determined whether or not the liquid reducing agent may be crystallized in the injection valve 25.

  When the internal combustion engine is stopped, the cooling function of the reducing agent injection valve 25 by cooling water or air cooling means of the internal combustion engine is stopped. Therefore, if the exhaust temperature Temp_g at the time of stop of the internal combustion engine is high, the exhaust gas remaining after the internal combustion engine is stopped The reducing agent injection valve 25 is heated by heat, and the concentration of the remaining liquid reducing agent increases, so that the freezing point (melting point) of the liquid reducing agent may increase. In this case, as the reducing agent injection valve 25 is naturally cooled thereafter, the temperature of the liquid reducing agent remaining inside falls below the raised freezing point and becomes easier to crystallize.

  Therefore, in the primary estimation unit 47, the liquid reducing agent is actually crystallized from the exhaust temperature Temp_g at the time of the previous stop of the internal combustion engine having a correlation with the freezing point of the liquid reducing agent, the stop time Ts of the internal combustion engine, and the like. It is determined whether there is a risk. For example, in the present embodiment, a determination map as shown in FIG. 3 is prepared, and whether or not to open / close is determined based on the exhaust temperature Temp_g at the previous stop of the internal combustion engine and the stop time Ts of the internal combustion engine. Estimated.

That is, when the exhaust gas temperature Temp_g at the time of the previous stop of the internal combustion engine is low, it is estimated that the freezing point of the liquid reducing agent is unlikely to change and that the reducing agent injection valve 25 can be opened and closed. Even when the exhaust gas temperature Temp_g when the internal combustion engine is stopped is high and the freezing point of the liquid reducing agent is likely to rise, the reducing agent injection valve 25 can be opened and closed while the internal combustion engine stop time Ts is short. Estimated.
On the other hand, when the exhaust temperature Temp_g when the internal combustion engine is stopped is high, the liquid reducing agent is exposed to a lower temperature as the stop time Ts of the internal combustion engine becomes longer, and the opening and closing operation of the reducing agent injection valve 25 is impossible. Is likely to become. In this case, since the freezing point of the liquid reducing agent fluctuates according to the exhaust temperature Temp_g when the internal combustion engine is stopped, the higher the exhaust temperature Temp_g, the shorter the stop time that becomes an open / close boundary. Yes.

  However, the method of estimating whether or not the reducing agent injection valve can be opened / closed based on the previous stop state of the internal combustion engine is not limited to the above-described example. In particular, the exhaust temperature Temp_g at the time of the previous stop of the internal combustion engine does not have to be a temperature detected at a single point, and can be set as appropriate, such as the maximum temperature within a certain period after the stop.

  When the primary estimating unit 47 estimates that the opening / closing operation of the reducing agent injection valve 25 is impossible, the secondary determination unit 49 drives the reducing agent injection valve 25 a plurality of times to physically open / close the reducing agent injection valve 25. Judge whether operation is possible. Specifically, the reducing agent injection valve 25 is of a solenoid valve type, and when the valve body actually starts moving after energization starts, a change appears in the current waveform. Whether or not the reducing agent injection valve 25 can be opened and closed is determined by checking whether or not a waveform change has occurred. At this time, there is a possibility that the sticking of the valve body due to the crystallization of the liquid reducing agent cannot be eliminated by only one driving, and therefore the reducing agent injection valve 25 is driven a plurality of times.

  FIG. 4 shows a current waveform when the reducing agent injection valve 25 is driven a plurality of times. As shown in FIG. 4, after the energization of the reducing agent injection valve 25 is started, a point P at which the current value decreases momentarily appears when the valve body starts to move. Therefore, if this lowering point P appears, it can be determined that the valve body is physically operable. On the other hand, when the lowering point P is not seen, the valve body is fixed and cannot be physically opened and closed. It can be determined that

  The melting control unit 53 executes the melting control of the liquid reducing agent in the reducing agent injection valve 25 when it is determined that the opening / closing operation of the reducing agent injection valve 25 is impossible as a determination result by the secondary determination unit 49. Specifically, in the present embodiment, the liquid reducing agent crystallized by the heat generated when the drive command is issued a plurality of times to the electromagnetic valve type reducing agent injection valve 25 and the coil is energized. It is made to melt above the freezing point.

(2) Flowchart Next, a specific example of the control method of the reducing agent supply device 20 of the present embodiment executed by the ECU 40 will be described based on the flowchart of FIG. The control method of the reducing agent supply device shown in the following flowchart is always executed when the internal combustion engine is started.

  First, in step S1 of FIG. 5, the ECU 40 reads the exhaust temperature Temp_g at the time of the previous stop of the internal combustion engine and the stop time Ts of the internal combustion engine stored in the storage means, and then in step S2, the reducing agent injection valve 25. The primary estimation of whether or not to open and close is performed. As described above, in the present embodiment, using the map prepared and stored in advance (see FIG. 3), the recorded exhaust temperature Temp_g at the previous stop of the internal combustion engine and the internal combustion engine Based on the stop time Ts, whether the reducing agent injection valve 25 can be opened or closed is estimated.

  Next, in step S3, the ECU 40 determines whether or not the reducing agent injection valve 25 cannot be opened and closed as a result of the primary estimation. When it is estimated that opening and closing is possible (No determination), the process proceeds to step S10 as it is, permission to start injection of the liquid reducing agent is given, and the process proceeds to a main routine of liquid reducing agent injection control (not shown).

  On the other hand, in step S3, when it is estimated that the reducing agent injection valve 25 cannot be opened and closed as a result of the primary estimation (Yes determination), the process proceeds to step S4, and an opening / closing instruction is output to the reducing agent injection valve 25. To do. At this time, the current value flowing through the reducing agent injection valve 25 is stored in the storage means. Although the opening / closing instruction may be performed only once, the accuracy of the secondary determination in the next step can be improved by executing the opening / closing instruction a plurality of times.

  In step S5, the ECU 40 reads a current value during the opening / closing operation of the reducing agent injection valve 25, and performs a secondary determination as to whether the reducing agent injection valve 25 can be physically opened or closed. As described above, in the present embodiment, whether or not physical opening / closing is possible is determined based on whether or not the current value drop point P that appears when the valve body starts moving appears in the current waveform during the opening / closing operation (see FIG. 4). reference.).

  Next, in step S6, the ECU 40 determines whether or not the reducing agent injection valve 25 is physically open / closed as a result of the secondary determination. If physical opening / closing is possible (No determination), the process proceeds to step S10, permission to start the injection of the liquid reducing agent is given, and the process proceeds to a main routine of liquid reducing agent injection control (not shown).

  On the other hand, if it is determined in step S6 that the physical opening / closing of the reducing agent injection valve 25 is impossible as a result of the secondary determination (Yes determination), the process proceeds to step S7, where it is determined that the physical opening / closing is impossible. It is determined whether or not the number N of times reached the threshold value N0. When the number N is less than the threshold value N0, the process proceeds to step S9, and the ECU 40 executes the melting control of the liquid reducing agent crystallized in the reducing agent injection valve 25. As described above, in the present embodiment, the liquid reducing agent crystallized by the heat generated when the drive command is issued multiple times to the electromagnetic valve type reducing agent injection valve 25 and the coil is energized. It is made to melt above the freezing point.

  After executing the melting control, the ECU 40 returns to step S4 to make a secondary determination as to whether the reducing agent injection valve 25 can be physically opened or closed. If the reason why the reducing agent injection valve 25 cannot be physically opened and closed is the crystallization of the liquid reducing agent, the reducing agent injection valve 25 can be physically opened and closed by repeating this several times. Then, the injection of the liquid reducing agent can be started. That is, a No determination is made in step S6, and permission to start injection of the liquid reducing agent is given in step S10.

  On the other hand, when the secondary determination is repeated a plurality of times, the reducing agent injection valve 25 cannot be physically opened and closed, and when the number N reaches the threshold value N0 in Step S7 (Yes determination), the process proceeds to Step S8. It is determined that the reducing agent injection valve 25 is out of order, and the driver is notified by turning on a warning lamp or the like, and this routine is terminated without permitting the injection of the liquid reducing agent.

4). Advantageous Effects of the Present Embodiment According to the control method of the reducing agent supply apparatus according to the present embodiment described above, based on the previous stop state of the internal combustion engine, for example, the exhaust temperature Temp_g and the stop time Ts of the internal combustion engine. After the primary estimation and the secondary determination based on the driving state of the reducing agent injection valve 25, for example, the current waveform at the time of opening / closing instruction of the reducing agent injection valve 25, the opening / closing operation of the reducing agent injection valve 25 is impossible. Only when the determination is made, the melting control of the liquid reducing agent is executed. Therefore, melting control is executed only when the possibility of crystallization of the liquid reducing agent is extremely high, so unnecessary melting control is omitted, and efficiency of melting control is achieved.

  Moreover, in the control method of the reducing agent supply apparatus according to the present embodiment, the secondary determination is performed based on the waveform of the current flowing through the reducing agent injection valve 25 when the reducing agent injection valve 25 is driven. Therefore, it is possible to determine whether the physical opening / closing operation of the reducing agent injection valve 25 is possible without increasing the number of additional devices.

  Further, in the control method of the reducing agent supply device according to the present embodiment, the melting control is performed by driving the reducing agent injection valve 25 a plurality of times and generating heat in the reducing agent injection valve 25. The crystallization of the liquid reducing agent generated in the reducing agent injection valve 25 can be eliminated without increasing the number of additional devices. Further, such melting control is executed only when the possibility of crystallization of the liquid reducing agent is extremely high, and therefore is executed before the liquid reducing agent reaches the reducing agent injection valve 25. Thus, the risk of damage to the seat portion of the reducing agent injection valve 25 can be reduced.

  In the control method of the reducing agent supply apparatus according to the present embodiment, the secondary determination is performed again after the melting control is performed, and the number N of times when it is determined that the reducing agent injection valve 25 cannot be physically opened and closed. When the value reaches the threshold value N0, it is determined that the reducing agent injection valve 25 has a permanent failure. Therefore, when the reducing agent injection valve 25 is stuck due to crystallization of the liquid reducing agent. Can encourage the driver to take measures.

  Further, in the control method for the reducing agent supply apparatus according to the present embodiment, the primary estimation is based on the exhaust temperature Temp_g at the previous stop of the internal combustion engine and further the stop time Ts of the internal combustion engine. In order to estimate the possibility of crystallization of the liquid reducing agent in the engine, the next secondary determination is executed when the internal combustion engine is stopped in a state where crystallization of the liquid reducing agent is likely to occur. Thus, it is possible to accurately determine a state where the possibility of crystallization of the liquid reducing agent is extremely high.

  The embodiment described so far shows one embodiment of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

  For example, as a specific method of primary estimation or secondary determination, methods other than the above-described examples are possible. In particular, when performing the primary estimation, the liquid reduction is performed in consideration of not only the exhaust temperature Temp_g at the previous stop time of the internal combustion engine and the stop time Ts of the internal combustion engine, but also the current outside air temperature and the temperature in the storage tank 21. The crystallization of the agent can also be estimated. Further, the threshold value N0 for determining a permanent failure of the reducing agent injection valve 25 should be set to an appropriate value in consideration of the time that can be waited until the liquid reducing agent injection starts, the determination accuracy, and the like. Can do.

10: exhaust purification device, 11: exhaust passage, 13: reduction catalyst, 15: exhaust temperature sensor, 20: reducing agent supply device, 21: storage tank, 23: pump, 23a: inlet side, 23b: outlet side, 25: Reducing agent injection valve, 27: first supply passage, 28: second supply passage, 29: return passage, 30: pump unit, 31: pressure sensor, 33: flow path switching valve, 35: one-way valve, 37 : Throttle unit, 40: ECU (electronic control unit), 41: pump control unit, 43: reducing agent injection valve control unit, 45: flow path switching valve control unit, 47: primary estimation unit, 49: secondary determination unit, 51: Recovery control unit, 53: Melting control unit

Claims (5)

While the internal combustion engine is in operation, the liquid reducing agent in the storage tank is pumped by a pump and supplied to the reducing agent injection valve, and the liquid reducing agent is injected into the exhaust passage of the internal combustion engine by the reducing agent injection valve. In the control method of the reducing agent supply device for controlling the reducing agent supply device configured to recover the remaining liquid reducing agent into the storage tank when the internal combustion engine is stopped.
When starting the internal combustion engine, based on the previous stop state of the internal combustion engine, primary estimation of whether or not the reducing agent injection valve can be opened and closed,
As a result of the primary estimation, when it is estimated that the opening / closing operation is impossible, the reducing agent injection valve is driven a plurality of times to make a secondary determination as to whether the opening / closing operation of the reducing agent injection valve is possible,
As a result of the secondary determination, when it is determined that the opening / closing operation is impossible, a melting control of the liquid reducing agent at the reducing agent injection valve is executed. .   The method for controlling a reducing agent supply apparatus according to claim 1, wherein the secondary determination is performed based on a waveform of a current flowing through the reducing agent injection valve when the reducing agent injection valve is driven.   The method of controlling a reducing agent supply apparatus according to claim 1 or 2, wherein the melting control is performed by driving the reducing agent injection valve a plurality of times and generating heat in the reducing agent injection valve.   The secondary determination is performed again after the melting control is performed, and when the opening / closing operation is not possible even after the melting control is repeated a predetermined number of times, it is determined that the reducing agent injection valve has a permanent failure. The control method of the reducing agent supply apparatus as described in any one of Claims 1-3 characterized by the above-mentioned.   The primary estimation is for estimating the possibility of crystallization of the liquid reducing agent in the reducing agent injection valve based on the exhaust gas temperature when the internal combustion engine was stopped last time. The control method of the reducing agent supply apparatus as described in any one of 4.

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