JP5914151B2 - Reducing agent injection valve abnormality detection device and reducing agent supply device - Google Patents

Description

  The present invention relates to an abnormality detecting device for a reducing agent injection valve for detecting clogging generated in a reducing agent injection valve for injecting a liquid reducing agent into an exhaust pipe, and a reducing agent supply including such an abnormality detecting device. It relates to the device.

Exhaust gas discharged from an internal combustion engine mounted on a vehicle or the like contains nitrogen oxides (NO _x ). As one of exhaust purifying apparatus for purifying the NO _X, the reduction for injecting a reducing catalyst disposed in an exhaust passage of an internal combustion engine, a liquid reducing agent from ammonia, such as urea aqueous solution on the upstream side of the reduction catalyst There is known an exhaust emission control device including an agent supply device. The exhaust gas purification apparatus uses a reducing catalyst, and an ammonia generated from the NO _X and the liquid reducing agent in the exhaust efficiently by reduction reaction, which is assumed to decompose to nitrogen and water, etc. The NO _X .

  As one aspect of the reducing agent supply device used in such an exhaust purification device, a pump and a reducing agent injection valve are provided, the liquid reducing agent is pumped by the pump, and through a reducing agent injection valve fixed to the exhaust pipe. There is an injection-type reducing agent supply device that supplies a liquid reducing agent into an exhaust pipe.

  Even if the freezing temperature of the urea aqueous solution is low, it is about −11 ° C., and the urea aqueous solution may freeze during the period in which the supply of the urea aqueous solution by the reducing agent supply device is stopped. When the aqueous urea solution freezes, the volume of the urea solution expands and may cause damage to the components of the reducing agent supply device. Therefore, when the internal combustion engine is stopped, the liquid reducing agent remaining in the reducing agent supply device is put into the tank. Control to collect is performed. The liquid reducing agent can be recovered by rotating the pump that pumps the liquid reducing agent in the reverse direction or by switching the connection of the flow path of the liquid reducing agent so that the liquid reducing agent is sent to the tank side. This is performed by reducing the pressure in the reducing agent supply passage.

  In addition, when an aqueous urea solution is used as the liquid reducing agent, urea may crystallize due to evaporation of water in the aqueous urea solution, and when this urea crystallization occurs in the nozzle hole portion of the reducing agent injection valve, the reducing agent injection Causes valve blockage. During the injection control of the liquid reducing agent, the relatively low temperature liquid reducing agent is sequentially sent to the reducing agent injection valve, so that there is little possibility that the reducing agent injection valve becomes hot and the moisture evaporates. Even if urea can be crystallized in the pores, the crystal is blown away by the injection pressure of the liquid reducing agent, so that the risk of the blocking of the reducing agent injection valve is small.

  On the other hand, in the above-described liquid reducing agent recovery control, when the reducing agent injection valve is opened to reduce the pressure in the supply passage, residual gas (air) in the exhaust pipe enters the supply passage. . At that time, if the liquid reducing agent is attached near the nozzle hole of the reducing agent injection valve, the reducing agent injection valve is heated by the amount of heat of the residual gas, and the urea aqueous solution attached near the nozzle hole of the reducing agent injection valve Urea may crystallize due to evaporation of the water inside. Such crystallization of urea may cause clogging of the reducing agent injection valve.

  Therefore, when the liquid reducing agent is recovered in the tank, a reducing agent injection valve abnormality detection device is proposed that detects whether the reducing agent injection valve is blocked by using the pressure value in the reducing agent supply device. Has been. More specifically, in the reducing agent supply apparatus configured to be able to suck the air in the exhaust pipe into the supply passage through the nozzle hole of the reducing agent injection valve by decompressing the inside of the supply passage of the liquid reducing agent, An abnormality detection device for a reducing agent injection valve is disclosed that uses a pressure value detected by a pressure sensor after the start of decompression processing to determine whether or not the reducing agent injection valve is blocked (see Patent Document 1). ).

JP 2011-117440 A

  By the way, the crystallization of urea in the nozzle hole affects the injection amount of the liquid reducing agent while the reducing agent injection valve is closed, but unlike the failure or failure of the component parts, It is possible to return to the state. Therefore, it must be distinguished from a mechanical failure of the components of the reducing agent supply device. However, the detection of the presence or absence of blocking of the reducing agent injection valve described in Patent Document 1 is based on the premise that the sensor value of the pressure sensor is reliable, and the reliability of the sensor value of the pressure sensor is guaranteed. If not, it is impossible to distinguish between the abnormality of the pressure sensor and the blocking of the reducing agent injection valve.

  Accordingly, the inventors of the present invention diligently tried to reduce the pressure in the supply passage of the liquid reducing agent, thereby sucking the gas into the supply passage through the nozzle hole of the reducing agent injection valve. In the reducing agent supply device configured to be recoverable, the presence or absence of blocking of the reducing agent injection valve is determined in consideration of the transition of the sensor value of the pressure sensor after the decompression process is stopped after the start of the decompression process. Thus, the present inventors have found that such a problem can be solved and completed the present invention. That is, an object of the present invention is to provide a reducing agent injection valve abnormality detection device and a reducing agent supply device with improved accuracy in determining whether or not the reducing agent injection valve is blocked.

According to the present invention, a pump that pumps the liquid reducing agent contained in a tank, a reducing agent injection valve that injects the liquid reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine, the pump, and the pump A supply passage for connecting the reducing agent injection valve, and pressure detecting means for detecting the pressure in the supply passage, and reducing the pressure in the supply passage to reduce the injection hole of the reducing agent injection valve. In the reducing agent injection valve abnormality detection device for detecting the blocking of the reducing agent injection valve in the reducing agent supply device configured to be able to collect the liquid reducing agent in the tank while sucking gas into the supply passage through After the start of the decompression process, the decompression process is stopped, and the reducing agent injection valve is closed using the pressure value detected by the pressure detection means until a predetermined time elapses. Whether it provided with a determination unit that, from the start of the decompression process to the stopping of the vacuum treatment is a first period, from stopping of the vacuum processing until the predetermined time elapses as a second period, the determination The unit determines that the reducing agent injection valve is closed when a predetermined condition is satisfied in each of the first period and the second period, and in the second period, the pressure reduction Control is performed to release the supply passage to the atmosphere after the process is stopped and the reductant injection valve is instructed to open, and the determination unit is configured to control the pressure in the supply passage during the first period. Is less than or equal to a predetermined threshold, and when the pressure in the supply passage returns to atmospheric pressure after the supply passage is opened to the atmosphere in the second period, the reducing agent injection valve is blocked. that you determined that there Abnormality detection device of the reducing agent injection valve according to symptoms is provided, it is possible to solve the problems described above.

In other words, the abnormality detecting device for a reducing agent injection valve according to the present invention performs reduction using the pressure value in the supply passage detected by the pressure detection means in the period from when the supply passage is depressurized until returning to atmospheric pressure. Since it is determined whether or not the agent injection valve is blocked, it is possible to detect the blockage of the reducing agent injection valve with high accuracy in distinction from the abnormality of the pressure detecting means. Further, by determining whether or not the reducing agent injection valve is blocked in this way, the reduction is performed based on the pressure value in the supply passage during the decompression process and the pressure value in the supply passage when returning to atmospheric pressure. The blockage of the agent injection valve can be detected with high accuracy. Further, by determining whether or not the reducing agent injection valve is blocked as described above, it is easy to distinguish whether there is an abnormality in the pressure detection means itself, and it is possible to detect the blocking of the reducing agent injection valve with high accuracy.

Further, in configuring the reducing agent injection valve abnormality detection device of the present invention, the determination unit is configured such that the pressure in the supply passage is equal to or lower than a predetermined threshold in the first period, and the second period. When the reducing agent injection valve is instructed to open, the pressure in the supply passage does not quickly return to atmospheric pressure, and it is determined that the reducing agent injection valve is closed. Is preferred.
By determining whether or not the reducing agent injection valve is blocked as described above, a large negative pressure is generated in the first period, and a return to the atmospheric pressure is delayed in the second period. Thus, the blocking of the reducing agent injection valve can be detected with high accuracy.

In another aspect of the present invention, a pump that pumps the liquid reducing agent contained in the tank, a reducing agent injection valve that injects the liquid reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine, A supply passage connecting the pump and the reducing agent injection valve; and pressure detecting means for detecting a pressure in the supply passage; and reducing the pressure in the supply passage, thereby reducing the reducing agent injection valve. In the reducing agent supply apparatus configured to be able to collect the liquid reducing agent in the tank while sucking gas into the supply passage through the nozzle hole, the decompression process is stopped after the decompression process is started, further comprising a determination unit for determining the presence or absence of clogging of the reducing agent injection valve with a pressure value detected by said pressure detecting means during a period until a predetermined time elapses, the the start of the decompression process The period until the stop of the pressure process is the first period, the period until the predetermined time has elapsed since the stop of the pressure reduction process is the second period, and the determination unit is respectively in the first period and the second period When the predetermined condition is satisfied, it is determined that the reducing agent injection valve is closed, and in the second period, the decompression process is stopped and an opening instruction is issued to the reducing agent injection valve. Control is performed to release the supply passage to the atmosphere after waiting in a state, and the determination unit determines that the pressure in the supply passage is less than or equal to a predetermined threshold in the first period, and in the second period. when the pressure in the supply passage after the supply passage is the air release is returned to atmospheric pressure, the reducing agent injection valve is a reducing agent supply apparatus characterized that you determined to be closed .

That is, the reducing agent supply apparatus according to the present invention uses the pressure value in the supply passage detected by the pressure detection means in the period from when the supply passage is depressurized to when it returns to atmospheric pressure. Since it is provided with the determination part which determines the presence or absence of obstruction | occlusion, it can distinguish from the abnormality of a pressure sensor, and the obstruction | occlusion of a reducing agent injection valve can be detected accurately. Further, by determining whether or not the reducing agent injection valve is blocked in this way, the reduction is performed based on the pressure value in the supply passage during the decompression process and the pressure value in the supply passage when returning to atmospheric pressure. The blockage of the agent injection valve can be detected with high accuracy. Further, by determining whether or not the reducing agent injection valve is blocked as described above, it is easy to distinguish whether there is an abnormality in the pressure detection means itself, and it is possible to detect the blocking of the reducing agent injection valve with high accuracy.

1 is an overall view showing a configuration example of an exhaust gas purification apparatus provided with a reducing agent injection valve abnormality detection device and a reducing agent supply device according to an embodiment of the present invention. It is a block diagram which shows the structural example of the electronic controller as an abnormality detection apparatus of the reducing agent injection valve which concerns on embodiment of this invention. It is a time chart for demonstrating the abnormality detection method of the reducing agent injection valve performed by the abnormality detection apparatus of the reducing agent injection valve which concerns on embodiment of this invention. It is a flowchart for demonstrating the abnormality detection method of the reducing agent injection valve performed by the abnormality detection apparatus of the reducing agent injection valve which concerns on embodiment of this invention. It is a flowchart for demonstrating the example of the specific determination method of the presence or absence of obstruction | occlusion of a reducing agent injection valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to a reducing agent injection valve abnormality detection device and a reducing agent supply device according to 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.

[First Embodiment]
1. FIG. 1 shows an exhaust emission control device provided with a reducing agent injection valve abnormality detection device (electronic control unit: ECU) 40 and a reducing agent supply device 20 according to a first embodiment of the present invention. It is a figure shown in order to demonstrate an example of 10 whole structure.
Exhaust purification apparatus 10 is an apparatus for purifying NO _X in the exhaust gas, is provided in the 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.

The reduction catalyst 13 is a catalyst having a function of promoting the decomposition 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 apparatus 20 of the present embodiment 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.

2. Reducing Agent Supply Device (1) Basic Configuration In FIG. 1, a reducing agent supply device 20 includes a tank 21 in which a liquid reducing agent is accommodated, a pump unit 30 that pumps the liquid reducing agent, and an exhaust passage 11 that discharges the liquid reducing agent. A reducing agent injection valve 25 is provided as a reducing agent injection unit for injecting the inside. 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 the ECU 40.

  The pump 23 and the 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 has a pressure sensor as pressure detection means for detecting the pressure in the second supply passage 28, that is, the pressure of the liquid reducing agent pumped to the reducing agent injection valve 25. 31 is provided. 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 tank 21 side is located in the vicinity of the bottom surface of the tank 21 so that the liquid reducing agent can be sucked up.

  In the flow path switching valve 33, the flow direction of the liquid reducing agent pumped by the pump 23 flows in the forward direction flowing from the tank 21 side to the reducing agent injection valve 25 side, and the reverse direction flowing from the reducing agent injection valve 25 side to the tank 21 side. It has a function to switch between directions. In the reducing agent supply apparatus 20 according to the present embodiment, the flow path switching valve 33 communicates the first supply passage 27 with the inlet side 23a of the pump 23 in a non-energized state and the second supply passage 28 with the pump 23. The first supply passage 27 is in communication with the outlet side 23b of the pump 23 and the second supply passage 28 is in communication with the inlet side 23a of the pump 23. Yes.

  That is, in the operating state of the internal combustion engine, 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. On the other hand, when the internal combustion engine is stopped, the flow path switching valve 33 is energized in order to collect the liquid reducing agent in the reducing agent supply device 20 in the tank 21.

  The configuration in which the liquid reducing agent can be collected in the tank 21 when the internal combustion engine is stopped is not limited to the example in which the flow path switching valve 33 is provided. For example, the liquid reducing agent can be collected by using the pump 23 that can rotate in reverse.

In addition, a return passage 29 having the other end connected to the tank 21 is branched in the middle of the second supply passage 28. An end of the return passage 29 on the tank 21 side is connected to a gas phase portion in the tank 21.
The 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 path area is provided so that the pressure in the second supply passage 28 can be increased. The return passage 29 closer to the second supply passage 28 than the throttle portion 37 is provided with a one-way valve 35 for preventing the liquid reducing agent from flowing from the tank 21 side to the second supply passage 28 side. It has been.

  In the reducing agent supply device 20 according to the present embodiment, the pressure sensor 31 is provided in the pump unit 30, but may be provided at any position in the second supply passage 28.

  The pump 23 pumps a liquid reducing agent at a predetermined flow rate by energization control by the ECU 40. In the present embodiment, the pump 23 is an electromagnetic pump, and the output (discharge amount) of the pump 23 increases as the drive duty ratio increases.

  During the injection control of the liquid reducing agent, the pressure value in the second supply passage 28 detected by the pressure sensor 31 (hereinafter, this value is referred to as “detected pressure”) Pu is a predetermined value set in advance. The output of the pump 23 is feedback-controlled so that the target pressure Pu_tgt is maintained. Specifically, the ECU 40 detects the pressure by the pressure sensor 31 provided in the second supply passage 28 while circulating the liquid reducing agent pumped to the second supply passage 28 to the tank 21 through the return passage 29. The output of the pump 23 is PID controlled based on a difference ΔPu between the detected pressure Pu to be set and a predetermined target pressure Pu_tgt set in advance. In the case where the liquid reducing agent is recovered in the tank 21, the ECU 40 controls the pump 23 with a predetermined output, for example.

  The reducing agent injection valve 25 is controlled to open and close by energization control, and injects a predetermined amount of liquid reducing agent into the exhaust passage 11. In the present embodiment, 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.

2. Electronic control device (abnormality detection device)
FIG. 2 shows a configuration example in which functional blocks are used to represent parts related to the control of the reducing agent supply device 20 and the abnormality detection of the reducing agent injection valve 25 in the ECU 40 of the present embodiment. The ECU 40 has not only a function as a control device of the reducing agent supply device 20, but also a function as an abnormality detection device of the reducing agent injection valve 25 according to the present invention.

  The ECU 40 is configured around a known microcomputer, and includes a reducing agent recovery instruction unit 41, a flow path switching valve control unit 43, a pump drive control unit 45, and a reducing agent injection valve drive control unit 47. And a determination unit 49. Specifically, each of these units is realized by executing a program by a microcomputer.

  In addition to this, the ECU 40 is shown for energizing a memory element (not shown) such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a pump 23, a flow path switching valve 33, and a reducing agent injection valve 25. The drive circuit etc. which are not provided are provided. The ECU 40 receives sensor values of various sensors provided in the reducing agent supply device 20, the internal combustion engine, the exhaust passage 11, and the like, in addition to the sensor value of the pressure sensor 31, and values such as the detected pressure Pu are obtained. It is stored in the storage element.

  For example, the reducing agent recovery instruction unit 41 generates the execution signal Sp of the decompression process triggered by the key switch of the internal combustion engine being turned off. In addition, the flow path switching valve control unit 43 always maintains the flow path switching valve 33 in a non-energized state so that the liquid reducing agent flows in the forward direction, while the decompression processing execution signal Sp is generated. , The flow path switching valve 33 is energized and maintained so that the liquid reducing agent flows in the reverse direction.

  The pump drive control unit 45 controls the pump 23 so that the detected pressure Pu in the second supply passage 28 is maintained at the target pressure Pu_tgt based on the detected pressure detected by the pressure sensor 31 during operation of the internal combustion engine. Perform feedback control of the output. The pump drive control unit 45 is configured to drive the pump 41 for a predetermined time with a predetermined output when the internal combustion engine is stopped and the decompression process execution signal Sp is generated. Send instructions to.

Information reducing agent injection valve drive control unit 47, during operation of the internal combustion engine, exhaust gas temperature Tgas, the temperature Tcat of the reduction catalyst 13, NO _X concentration Nnox on the downstream side of the reduction catalyst 13, further relates to the rotation speed Ne of the internal combustion engine Based on the above, the target injection amount Qdv_tgt of the liquid reducing agent is calculated, and a control signal corresponding to the target injection amount Qdv_tgt is output to the drive circuit of the reducing agent injection valve. Further, when the internal combustion engine is stopped and the reducing signal execution signal Sp is received, the reducing agent injection valve drive control unit 47 generates a control signal for holding the reducing agent injection valve 25 in the open state. Output to the drive circuit. In the present embodiment, the reducing agent injection valve drive control unit 47 causes the reducing agent injection valve 25 to be slightly delayed after the flow path switching valve 33 is energized and the output of the pump 23 is set to a predetermined output. Open the valve.

  The determination unit 49 determines whether or not the reducing agent injection valve 25 is blocked using the detected pressure Pu in the second supply passage 58 detected by the pressure sensor 31 after the execution signal Sp of the decompression process is generated. To do. Specifically, in the present embodiment, the determination unit 49 determines that the reducing agent injection valve is based on the detected pressure Pu in a period from when the decompression process is started to when the decompression process is stopped until a predetermined time elapses. It is comprised as what determines the presence or absence of 25 obstruction | occlusion.

3. Detection of Abnormality of Reducing Agent Injection Valve (1) Outline of Abnormality Detection Method Hereinafter, an outline of an abnormality detection method for the reducing agent injection valve 25 executed by the ECU 40 in the reducing agent supply apparatus 20 according to the present embodiment will be described.
FIG. 3 is a time chart for explaining an abnormality detection method for the reducing agent injection valve 25. The on / off state of the key switch of the internal combustion engine, the output (drive duty ratio) of the pump 23, the flow path switching valve 33 The energized on / off state, the drive duty ratio of the reducing agent injection valve 25, and the detected pressure Pu detected by the pressure sensor 31 are shown as time passes.

  When the key switch of the internal combustion engine is turned off at the time t1, the output of the pump 23 is once made zero. Next, at time t2, the flow path switching valve 33 is energized to switch the flow direction of the liquid reducing agent in the reverse direction, and the output of the pump 23 is fixed to a predetermined specified value. From this time t2, the decompression process of the second supply passage 28 is started. Next, at the time t3 when the time T1 has elapsed from the time t2, the driving duty ratio of the reducing agent injection valve 25 is set to 100% and a valve opening instruction is issued to the reducing agent injection valve 25. Thereby, the residual gas (air) in the exhaust passage 11 can be sucked into the second supply passage 28 via the reducing agent injection valve 25, and the inside of the second supply passage 28 is being replaced with air. The liquid reducing agent is collected in the tank 21.

  Thereafter, at the time t4 when the time T2 has elapsed from the time t3, the driving of the pump 23 is stopped, the output of the pump 23 becomes zero, and the decompression process is ended. Thereafter, the flow path switching valve 33 and the reducing agent injection valve 25 are continuously held in the energized state until the time t5 when the time T3 elapses from the time t4. The period from t4 to t5 is a pressure compensation period and is a period for returning the inside of the second supply passage 28 to the atmospheric pressure state. At time t5, the energization to the flow path switching valve 33 is stopped, and the energization to the reducing agent injection valve 25 is stopped a little later. The reason why the closing of the reducing agent injection valve 25 is delayed is to prevent the pressure from rapidly increasing due to the reaction of returning the flow path switching valve 33 to the original state. Thereafter, at time t6 when the time T4 has elapsed from time t5, it is determined whether or not the reducing agent injection valve 25 is closed.

  As described above, when the second supply passage 28 is decompressed and the liquid reducing agent recovery control is performed, if the reducing agent injection valve 25 is not closed, the period from t2 to t4 (hereinafter, this period). Is referred to as a “decompression treatment period (first period)”), air is sucked into the second supply passage 28, so that the pressure in the second supply passage 28 does not drop significantly. (See the pressure indicated by the solid line in FIG. 3). On the other hand, when the reducing agent injection valve 25 is closed, air is not sucked into the second supply passage 28 in the decompression processing period (first period), and therefore, the second supply passage 28 has the inside. A great amount of negative pressure is generated (see the pressure indicated by the one-dot chain line in FIG. 3). In other words, in the period from the time t3 when the opening instruction to the reducing agent injection valve 25 is issued to the time t4 when the driving of the pump 23 is stopped, the second depends on whether or not the reducing agent injection valve 25 is blocked. A difference occurs in the pressure in the supply passage 28.

  Further, if the reducing agent injection valve 25 is not closed during a period after the time point t4 when the decompression process is stopped (hereinafter, this period is referred to as a “second period”), the process after the stop of the decompression process is performed. However, since air is introduced into the second supply passage 28 through the nozzle hole of the reducing agent injection valve 25 due to the negative pressure in the second supply passage 28, the pressure in the second supply passage 28 is It quickly returns to atmospheric pressure (see the pressure indicated by the solid line in FIG. 3). On the other hand, when the reducing agent injection valve 25 is closed, the negative pressure in the second supply passage 28 is maintained even after the decompression process is stopped, and the energization to the flow path switching valve 33 is stopped. After the time t5, the pressure in the second supply passage 28 is returned to the atmospheric pressure by the introduction of the atmospheric pressure from the tank 21 side (see the pressure indicated by the one-dot chain line in FIG. 3). Hereinafter, in the second period, the period from the time t4 when the driving of the pump 23 is stopped to the time t5 when the energization to the flow path switching valve 33 is stopped is referred to as a “pressure return period”, and the flow path switching is performed. A period after time t5 when the energization of the valve 33 is stopped is referred to as a “reset period”.

  Since the difference in the pressure change in the second supply passage 28 appears as described above depending on whether or not the reducing agent injection valve 25 is blocked, the abnormality detection device 40 for the reducing agent injection valve 25 of the present embodiment is configured as described above. Whether or not the reducing agent injection valve 25 is blocked is determined based on a change in the detected pressure Pu in the second supply passage 28 in the first period (decompression process period) and the second period (pressure return period and reset period). It has become something to try. By making such a determination, it is possible to accurately determine whether or not the reducing agent injection valve 25 is blocked, as distinguished from the case where the abnormality of the pressure sensor 31, in particular, the sticking of the sensor value occurs.

(2) Flowchart Next, a specific example of the abnormality detection method for the reducing agent injection valve 25 executed by the ECU 40 according to the present embodiment will be described based on the flowcharts of FIGS. 4 and 5. The abnormality detecting method for the reducing agent injection valve 25 shown in the following flowchart is executed every time or every predetermined number of times when the key switch of the internal combustion engine is turned off.

  First, when it is detected in step S1 of FIG. 4 that the key switch of the internal combustion engine has been turned off, the ECU 40 generates an instruction to start the liquid reducing agent recovery control in step S2. When the liquid reducing agent recovery control is started, the ECU 40 energizes the flow path switching valve 33 in step S3, and the flow of the liquid reducing agent pumped by the pump 23 from the reducing agent injection valve 25 side to the tank 21. Switch to the side.

  Next, in step S4, the ECU 40 fixes the output (drive duty ratio) of the pump 23 to a predetermined value, and starts the pressure reducing process for the second supply passage 28. Next, in step S5, the ECU 40 maintains the state until the standby time A from the start of the decompression process reaches a predetermined threshold T1, and when the standby time A reaches the threshold T1, the ECU 40 proceeds to step S6. The reducing agent injection valve 25 is maintained in the open state.

  Here, the time difference between the start of the decompression process and the opening of the reducing agent injection valve 25 is provided because the reducing agent injection valve 25 is opened while the second supply passage 28 is in a positive pressure state. This is because if the valve is used, the liquid reducing agent may leak into the exhaust passage 11. The threshold T1 of the waiting time A is an optimum time during which the inside of the second supply passage 28 is in a negative pressure state in consideration of the pipe diameter and length of the second supply passage 28 to be used, the output of the pump 23, and the like. It can be obtained and set in advance.

  If the reducing agent injection valve 25 is not blocked, after the reducing agent injection valve 25 is opened, the air (residual gas) in the exhaust passage 11 passes through the injection hole of the reducing agent injection valve 25 to the second position. Therefore, the liquid reducing agent in the second supply passage 28 is efficiently tanked while maintaining a relatively small negative pressure in the second supply passage 28. 21 is collected. On the other hand, when the reductant injection valve 25 is closed, even if an instruction to open the reductant injection valve 25 is issued, the valve is actually closed. A large negative pressure is generated.

  Next, in step S7, the ECU 40 determines whether or not the time B during which the decompression process is executed has reached a predetermined threshold value T2. In the time chart shown in FIG. 3, the pressure reduction time B is measured from the time when the output of the pump 23 is fixed. The pressure reduction time B is, for example, when the reducing agent injection valve 25 is opened in step S6. The time point may be counted. The threshold T2 for the pressure reduction time B is the liquid remaining in the reducing agent supply device 20 in consideration of the pipe diameters and lengths of the first supply passage 27 and the second supply passage 28 to be used, the output of the pump 23, and the like. An optimum time during which the reducing agent can be collected in the tank 21 can be obtained and set in advance.

  When the pressure reduction time B reaches the threshold value T2 in step S7, the ECU 40 stops driving the pump 23 in step S8 and ends the pressure reduction processing period. Thereafter, in step S9, the ECU 40 stands by until the standby time C after stopping the pump 23 reaches a predetermined threshold value T3. The period until the waiting time C reaches the threshold value T3 is a pressure return period for returning the pressure in the second supply passage 28 to atmospheric pressure, and when the reducing agent injection valve 25 is not blocked. The air in the exhaust pipe 11 is introduced into the second supply passage 28 through the injection hole of the reducing agent injection valve 25, and the inside of the second supply passage 28 is at atmospheric pressure. On the other hand, when the reducing agent injection valve 25 is blocked, the second supply passage 28 is maintained in a negative pressure state even when the driving of the pump 23 is stopped.

  At this time, when the pressure sensor 31 fails and the detected pressure Pu is stuck to a constant value, the reducing agent injection valve 25 is not blocked, and the pressure in the second supply passage 28 is reduced. Even when the pressure is actually returned to the atmospheric pressure, no change is observed in the detected pressure Pu.

  Thereafter, when the standby time C reaches the threshold value T3 in step S9, the ECU 40 stops energizing the flow path switching valve 33 in step S10, and changes the flow direction of the liquid reducing agent pumped by the pump 23 to the tank 21 side. Is switched to the reducing agent injection valve 25 side, and in step S11, the energization to the reducing agent injection valve 25 is stopped. In step S12, the ECU 40 waits until the standby time D reaches a predetermined threshold value T4. The period until the waiting time D reaches the threshold value T4 is a reset period, and atmospheric pressure can be introduced from the tank 21 side into the second supply passage 28 via the first supply passage 27 and the pump 21. When the reducing agent injection valve 25 is blocked, the second supply passage 28 returns to atmospheric pressure during this period.

  Even in this case, if the pressure sensor 31 fails and the detected pressure Pu is stuck to a constant value, even if the pressure in the second supply passage 28 actually returns to atmospheric pressure. Thus, no change is observed in the detected pressure Pu.

  Thereafter, when the standby time D reaches the threshold value T4 in step S12, the ECU 40 proceeds to step S13, and executes a blockage determination. FIG. 5 shows a specific flowchart for carrying out the blocking determination in the present embodiment. This blockage determination is performed with reference to the detected pressure Pu recorded in the storage element in the period from step S1 to step S11 in FIG.

  In the example of the blockage determination illustrated in FIG. 5, in step S21, the ECU 40 determines whether or not the detected pressure Pu in the second supply passage 28 in the pressure reduction process period (first period) is less than a predetermined threshold Thre_pu1. judge. The value of the threshold Thre_pu1 is determined based on whether the reducing agent injection valve 25 is closed or not during the pressure reduction process. The detected pressure Pu in each case is obtained in advance by experiments or the like, and the presence or absence of blockage is determined in consideration of the allowable range of blockage. Can be appropriately set to an optimum value (see FIG. 3). In addition, as the detected pressure Pu to be compared with the threshold Thre_pu1, for example, it is preferable to use a value in a state where the detected pressure Pu is stable for a predetermined time with a small pressure fluctuation.

  If it is determined Yes in step S21, then, in step S22, the ECU 40 determines the maximum value Pu2 and the minimum value Pu1 of the pressure in the second supply passage 28 during the pressure return period (= the detected pressure during the pressure reduction process period). , That is, whether or not the pressure fluctuation range ΔPu1 (see FIG. 3) is less than a predetermined threshold Thre2_dpu. When the reducing agent injection valve 25 is closed, the pressure fluctuation range ΔPu1 during the pressure return period should be very small, and the threshold Thre2_dpu is not closed by the reducing agent injection valve 25. In some cases, the fluctuation range when the inside of the second supply passage 28 returns to the atmospheric pressure can be obtained in advance by experiments or the like, and can be appropriately set to a value slightly larger than the fluctuation range.

  When it is determined Yes in step S22, the ECU 40 further determines, in step S23, the maximum value Pu3 and the minimum value Pu2 of the pressure in the second supply passage 28 in the reset period (= maximum value of the decompression process period). , That is, whether or not the pressure fluctuation range ΔPu2 (see FIG. 3) exceeds a predetermined threshold Thre3_dpu. When the reducing agent injection valve 25 is not blocked, the second supply passage 28 is already at atmospheric pressure, so the pressure fluctuation range ΔPu2 during this reset period should be close to zero. It is. On the other hand, when the reducing agent injection valve 25 is blocked, the negative pressure state in the second supply passage 28 should be canceled and the atmospheric pressure should be restored during this reset period. Therefore, the value of the threshold Thre3_dpu can be appropriately set to an optimal value by obtaining a pressure fluctuation range when the reducing agent injection valve 25 is blocked by an experiment or the like in advance and considering the fluctuation range.

  When all of the above steps S21 to S23 are determined to be Yes, it is estimated that the reducing agent injection valve 25 is closed, the ECU 40 proceeds to step S24, and the reducing agent injection valve. It is determined that 25 blockages have occurred, and processing such as setting a flag is performed. Then, in step S25, the ECU 40 performs error processing so as to turn on the alarm lamp or suppress the injection of the liquid reducing agent, and ends the blockage determination. Specifically, at the next start of the internal combustion engine, the driver is informed to suppress the injection of the liquid reducing agent until the crystallization of the liquid reducing agent is eliminated, or the operating state of the internal combustion engine is changed. It will be suppressed.

On the other hand, if it is determined No in any of steps S21 to S23, it is not a sufficient situation to determine that the reducing agent injection valve 25 is closed. Exit. When the reductant injection valve 25 is not blocked, it is determined as No in any step, and when the sensor value of the pressure sensor 31 is stuck, either step S22 or step S23 is performed. No will be determined.
After the blockage determination is completed, as shown in the flowchart of FIG. 4, the reducing agent injection valve abnormality detection method is terminated, and the power supply of the ECU 40 is also turned off.

4). Advantages Obtained by the Reducing Agent Injection Valve Abnormality Detection Device of the Present Embodiment As described above, according to the reducing agent injection valve abnormality detection device 40 and the reducing agent supply device 20 of the present embodiment, the internal combustion engine At the time of stop, whether or not the reducing agent injection valve 25 is blocked by using the detected pressure Pu in the second supply passage 28 during the period until the predetermined time elapses after the decompression process is started. Therefore, the state in which the detected pressure Pu in the second supply passage 28 returns to the atmospheric pressure is also monitored. Therefore, it is possible to detect the blockage of the reducing agent injection valve 25 with high accuracy in distinction from abnormality of the pressure sensor 31.

  Further, in the reducing agent injection valve abnormality detection device 40 according to the present embodiment, predetermined conditions are respectively satisfied in the first period (decompression process period) and the second period (pressure return period and reset period). Since it is determined that the reducing agent injection valve 25 is closed when it is satisfied, based on the detected pressure Pu1 during the pressure reduction process and the pressure fluctuation ranges ΔPu1, ΔPu2 when returning to the atmospheric pressure Further, the blocking of the reducing agent injection valve 25 can be detected with high accuracy.

  In the reducing agent injection valve abnormality detection device 40 according to the present embodiment, the detected pressure Pu1 in the second supply passage 28 in the first period (decompression process period) is less than the first threshold Thre_pu1. In addition, when the detected pressure Pu does not return to the atmospheric pressure during the pressure return period can be grasped based on the pressure fluctuation range ΔPu1, it is determined that the reducing agent injection valve 25 is closed. Therefore, it is possible to detect the blockage of the reducing agent injection valve 25 with high accuracy.

  In the reducing agent injection valve abnormality detection device 40 according to the present embodiment, the detected pressure Pu1 in the second supply passage 28 in the first period (decompression process period) is less than the first threshold Thre_pu1. In addition to the fact that the detected pressure Pu does not return to the atmospheric pressure during the pressure return period based on the pressure fluctuation range ΔPu1, the detected pressure Pu has returned to the atmospheric pressure during the reset period. When it can be grasped based on the pressure fluctuation range ΔPu2, it is determined that the reducing agent injection valve 25 is closed. Therefore, it is possible to detect the blockage of the reducing agent injection valve 25 with high accuracy by distinguishing from the abnormality in which the sensor value of the pressure sensor 31 is stuck.

  It should be noted that the reducing agent injection valve abnormality detection device 40 and the reducing agent supply device 20 according to the embodiments described so far show one aspect of the present invention and do not limit the present invention. Any change can be made within the scope of the invention.

10: exhaust purification device, 11: exhaust passage, 13: reduction catalyst, 20: reducing agent supply device, 21: 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 part, 40: ECU (Reducing agent injection valve abnormality detecting device), 41: reducing agent recovery instruction unit, 43: flow path switching valve control unit, 45: pump drive control unit, 47: reducing agent injection valve drive control unit, 49: determination unit

Claims (3)

A pump that pumps the liquid reducing agent contained in the tank, a reducing agent injection valve that injects the liquid reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine, and the pump and the reducing agent injection valve are connected. And a pressure detecting means for detecting the pressure in the supply passage, and the gas is supplied through the nozzle hole of the reducing agent injection valve by reducing the pressure in the supply passage. In the reducing agent injection valve abnormality detection device for detecting the blocking of the reducing agent injection valve in the reducing agent supply device configured to be able to collect the liquid reducing agent in the tank while being sucked into the passage,
Determining whether or not the reducing agent injection valve is blocked using the pressure value detected by the pressure detection means during a period until the predetermined time elapses after the decompression process is started. with a part,
The first period is from the start of the decompression process to the stop of the decompression process, and the second period is from the stop of the decompression process until the predetermined time has elapsed,
The determination unit determines that the reducing agent injection valve is closed when a predetermined condition is satisfied in each of the first period and the second period,
In the second period, control is performed to release the supply passage to the atmosphere after stopping the pressure reduction process and waiting in a state in which a valve opening instruction is issued to the reducing agent injection valve.
The determination unit determines that the pressure in the supply passage is less than or equal to a predetermined threshold value in the first period, and the pressure in the supply path after the supply passage is opened to the atmosphere in the second period. when returned to atmospheric pressure, the abnormality detecting device of a reducing agent injection valve the reducing agent injection valve is characterized that you determined to be closed. The determination unit is configured in spite of the fact that the pressure in the supply passage is equal to or lower than a predetermined threshold value in the first period, and the valve opening instruction is issued to the reducing agent injection valve in the second period. not when said pressure in the supply passage does not return to the atmospheric pressure quickly, the abnormality detecting device of a reducing agent injection valve according to claim 1, wherein the reducing agent injection valve and judging to be closed . A pump that pumps the liquid reducing agent contained in the tank, a reducing agent injection valve that injects the liquid reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine, and the pump and the reducing agent injection valve are connected. And a pressure detecting means for detecting the pressure in the supply passage, and the gas is supplied through the nozzle hole of the reducing agent injection valve by reducing the pressure in the supply passage. In the reducing agent supply apparatus configured to be able to collect the liquid reducing agent in the tank while sucking into the passage,
Determining whether or not the reducing agent injection valve is blocked using the pressure value detected by the pressure detection means during a period until the predetermined time elapses after the decompression process is started. with a part,
The first period is from the start of the decompression process to the stop of the decompression process, and the second period is from the stop of the decompression process until the predetermined time has elapsed,
The determination unit determines that the reducing agent injection valve is closed when a predetermined condition is satisfied in each of the first period and the second period,
In the second period, control is performed to release the supply passage to the atmosphere after stopping the pressure reduction process and waiting in a state in which a valve opening instruction is issued to the reducing agent injection valve.
The determination unit determines that the pressure in the supply passage is less than or equal to a predetermined threshold value in the first period, and the pressure in the supply path after the supply passage is opened to the atmosphere in the second period. when returned to atmospheric pressure, the reducing agent supply device wherein the reducing agent injection valve is characterized that you determined to be closed.

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