JP2018127960A - Abnormality diagnosis device and abnormality diagnosis method for reducing agent injection device - Google Patents

Abstract

An abnormality diagnosis device and abnormality diagnosis method for a reducing agent injection device capable of easily determining whether or not an injection valve has returned from being stuck open. An abnormality diagnosing device for diagnosing an abnormality of a reducing agent injection device that injects a reducing agent pumped by a pump into an exhaust passage by an injection valve provided in an exhaust passage of an internal combustion engine. A pump control unit that controls the pump output so that the supply pressure of the reducing agent is maintained at the target value, a sticking determination unit that determines whether or not the injection valve is stuck in the open state, and the injection valve is opened. Whether or not the sticking in the valve-opening state has been resolved based on the output of the pump in a state where the instruction value of the reducing agent injection amount is set to a reference value or less when it is determined that the valve is sticking. A return determination unit for determining. [Selection] Figure 6

Description

  The present invention relates to an abnormality diagnosis device and an abnormality diagnosis method for diagnosing abnormality of a reducing agent injection device for injecting a reducing agent into an exhaust passage of an internal combustion engine.

NO _x (nitrogen oxide) is contained in the exhaust gas of an internal combustion engine such as a diesel engine mounted on a vehicle. A urea SCR (Selective Catalytic Reduction) system has been put to practical use as an apparatus for decomposing NO _x and purifying exhaust gas. In the urea SCR system, a urea aqueous solution is used as a reducing agent, and NO _x is decomposed by reacting ammonia produced by hydrolysis of the urea aqueous solution with NO _x in the exhaust gas.

The urea SCR system includes a selective reduction catalyst disposed in the exhaust passage and a reducing agent injection device for injecting a urea aqueous solution into the exhaust passage upstream of the selective reduction catalyst. The selective reduction catalyst adsorbs ammonia and promotes a reduction reaction between NO _x and ammonia in the flowing exhaust gas. The reducing agent injection device includes a pump that pumps the urea aqueous solution accommodated in the storage tank and an injection valve that jets the urea aqueous solution pumped by the pump, and drive control is performed by the control device.

  In the urea SCR system, when the injection valve is exposed to a high temperature, the solvent of the urea aqueous solution evaporates in the injection valve to increase the concentration, and the urea aqueous solution may crystallize. For example, if the cooling function of the injection valve is stopped when the internal combustion engine is stopped, the urea aqueous solution in the injection valve may be heated and crystallized under the influence of residual exhaust heat. Further, even when the internal combustion engine is in operation, if the urea aqueous solution is not injected for a long period of time, the urea aqueous solution in the injection valve may be heated by the exhaust heat and crystallize. When the urea aqueous solution crystallizes in the injection valve, the valve body becomes stuck so that it cannot operate, and the injection valve sticks in the open state (open sticking) or the valve sticks in the closed state (closed sticking) There is.

  Patent Document 1 proposes an abnormality determination device for a reducing agent injection valve that can accurately determine whether the injection valve is stuck open or closed when a malfunction of the valve body of the injection valve occurs. . Specifically, based on the pressure change in the reducing agent passage when the inside of the reducing agent passage for supplying the urea aqueous solution to the injection valve is depressurized, the malfunction of the valve element is due to open sticking or due to closed sticking. An abnormality determination device for determining whether an object is present is disclosed.

JP 2012-102737 A

  Here, when the injection valve is closed and fixed, the urea aqueous solution does not leak into the exhaust pipe even if the drive of the pump is maintained. On the other hand, when the injection valve is in an open-fixed state, the urea aqueous solution continues to leak into the exhaust pipe while maintaining the pump drive. For this reason, when the open sticking of the injection valve is not solved, it is necessary to stop the driving of the pump. However, when the open sticking of the injection valve is caused by the crystallization of the urea aqueous solution, the liquid urea aqueous solution reaches the crystal, the crystal melts, and the open sticking may be eliminated. Therefore, it is desirable to be able to determine whether or not the injection valve has returned to normal from the open fixation afterwards even when the open fixation of the injection valve is detected.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an abnormality diagnosis device for a reducing agent injection device and an abnormality that can easily determine whether the injection valve has returned from open fixation. It is to provide a diagnostic method.

  According to an aspect of the present invention, an abnormality diagnosing device for diagnosing an abnormality of a reducing agent injection device that injects a reducing agent pumped by a pump into an exhaust passage by an injection valve provided in an exhaust passage of an internal combustion engine. A pump control unit that controls the pump output so that the supply pressure of the reducing agent to the injection valve is maintained at the target value, and a sticking determination that determines whether or not the injection valve is stuck in the open state. In the valve open state based on the output of the pump in a state where the instruction value of the reducing agent injection amount is set to a reference value or less when it is determined that the injection valve is stuck in the valve open state. And a return determination unit that determines whether or not the problem has been resolved.

  According to another aspect of the present invention, an abnormality for diagnosing an abnormality of a reducing agent injection device that injects a reducing agent pumped by a pump into an exhaust passage by an injection valve provided in the exhaust passage of the internal combustion engine. A diagnostic method, the step of controlling the pump output so that the supply pressure of the reducing agent to the injection valve is maintained at the target value, and the step of determining whether or not the injection valve is stuck in the open state When the injection valve is determined to be stuck in the opened state, the sticking in the opened state is determined based on the output of the pump in a state where the instruction value of the reducing agent injection amount is set to a reference value or less. And a step of determining whether or not the problem has been resolved.

  As described above, according to the present invention, it is possible to easily execute the determination of the return from the open fixing of the injection valve of the reducing agent injection device.

It is a schematic diagram which shows the urea SCR system provided with the reducing agent injection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the abnormality diagnosis apparatus which concerns on the same embodiment. It is explanatory drawing which shows the relationship between the instruction | indication value of injection amount, and a pump output. It is explanatory drawing which shows the change of the pump output in the state where the instruction value of injection quantity is small. It is explanatory drawing which shows the change of the pump output in the state where the instruction | indication value of injection amount is large. It is explanatory drawing which shows the change of the pump output by the abnormality diagnosis apparatus based on the embodiment. It is a flowchart which shows the process by the abnormality diagnosis apparatus concerning the embodiment. It is explanatory drawing which shows the difference in the electric current waveform of the injection valve by the presence or absence of adhesion of a valve body. It is explanatory drawing which shows the output of the pump in the state of open fixed or closed fixed of an injection valve.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Configuration of Urea SCR System>
With reference to FIG. 1, the structural example of the urea SCR system 10 provided with the reducing agent injection apparatus 30 is demonstrated. FIG. 1 is a schematic diagram illustrating a configuration example of the urea SCR system 10. The urea SCR system 10 includes a selective reduction catalyst 13 disposed in the middle of an exhaust pipe 11 connected to an exhaust system of an internal combustion engine 5 such as a diesel engine, and a reduction in the exhaust passage upstream of the selective reduction catalyst 13. A reducing agent injection device 30 for injecting the agent. The urea SCR system 10 is mounted on a vehicle, a construction machine, an agricultural machine, or the like equipped with an internal combustion engine 5, decomposes NO _{x in} exhaust gas discharged from the internal combustion engine 5 using urea aqueous solution as a reducing agent, and exhausts the exhaust gas. It is a system to purify.

  As the urea aqueous solution, for example, a urea aqueous solution having a concentration of about 32.5% having the lowest freezing temperature is used. The freezing temperature in this case is about -11 ° C. Since the freezing temperature of such an aqueous urea solution rises when the concentration changes, the aqueous urea solution is easily frozen by evaporation of water as a solvent.

The selective reduction catalyst 13 selectively reduces NO _x contained in the exhaust gas of the internal combustion engine 5 using ammonia. In the present embodiment, ammonia generated by hydrolysis of the urea aqueous solution injected by the reducing agent injection device 30 is adsorbed to the selective reduction catalyst 13, and NO _X in the exhaust gas flowing into the selective reduction catalyst 13 reacts with ammonia. It is decomposed by doing. The selective reduction catalyst 13 has a characteristic that the amount of ammonia that can be adsorbed decreases as the catalyst temperature increases. The selective reduction catalyst 13 has a characteristic that the NO _x reduction efficiency increases as the ratio of the actual ammonia adsorption amount to the adsorbable amount increases.

The reducing agent injection device 30 injects the urea aqueous solution into the exhaust passage upstream of the selective reduction catalyst 13. The reducing agent injection device 30 is driven and controlled by the control device 100. Injection amount of the urea aqueous solution, NO _X concentration in the exhaust gas, based on the temperature of the adsorption capacity and the selective reduction catalyst 13 ammonia in the selective reduction catalyst 13, NO _X or ammonia flows out to the downstream side of the selective reduction catalyst 13 Is controlled to be equal to or lower than the reference value.

The exhaust pipes 11 on the upstream side and the downstream side of the selective reduction catalyst 13 are provided with temperature sensors 21 and 23 for detecting the exhaust temperature, respectively. Sensor signals from the temperature sensors 21 and 23 are output to the control device 100. The exhaust temperature detected by the temperature sensors 21 and 23 is also used for estimating the temperature of the selective reduction catalyst 13. In addition to this, the exhaust pipe 11 may be provided with a NO _x concentration sensor, an ammonia sensor, or the like (not shown).

<2. Configuration of Reducing Agent Injection Device>
Next, a configuration example of the reducing agent injection device 30 will be described in detail. The reducing agent injection device 30 includes an injection valve 31 and a pump 41. The injection valve 31 is fixed to the exhaust pipe 11 on the upstream side of the selective reduction catalyst 13. The pump 41 sucks up and pumps the urea aqueous solution in the storage tank 50. Drive control of the pump 41 and the injection valve 31 is performed by the control device 100.

  The pump 41 sucks up the urea aqueous solution through the first reducing agent passage 58 and supplies the urea aqueous solution to the injection valve 31 through the second reducing agent passage 57. A return passage 59 having the other end connected to the storage tank 50 is connected to the second reducing agent passage 57. The return passage 59 is provided with an orifice or a one-way valve (not shown) so that the pressure in the second reducing agent passage 57 is increased. A pressure sensor 43 is provided in the second reducing agent passage 57. The pressure sensor 43 is a sensor that detects the pressure Pu of the urea aqueous solution supplied to the injection valve 31, and the sensor signal is output to the control device 100.

  As the pump 41, for example, an electromagnetically driven diaphragm pump or a gear pump is used. The output of the pump 41 is controlled based on the drive signal output from the control device 100. In the present embodiment, the control device 100 controls the output of the pump 41 so that the pressure Pu of the aqueous urea solution supplied to the injection valve 31 is maintained at a predetermined target value Ptgt. For example, the control device 100 feedback-controls the output of the pump 41 based on the deviation ΔP between the pressure Pu detected by the pressure sensor 43 and the target value Ptgt.

  The injection valve 31 includes, for example, an electromagnetic solenoid, and an electromagnetically driven injection valve that is switched between opening and closing by energization control is used. The electromagnetically driven injection valve 31 includes an electromagnetic coil, and has a structure in which the valve body is moved and opened by a magnetic force generated by energization of the electromagnetic coil. In the present embodiment, the output of the pump 41 is controlled so that the pressure Pu of the urea aqueous solution supplied to the injection valve 31 becomes a predetermined target value Ptgt, and the control device 100 opens according to the target injection amount of the urea aqueous solution. Adjust the valve time. For example, the control device 100 controls the injection amount of the urea aqueous solution by adjusting the duty ratio, which is the ratio of the energization time to the total time of the injection cycle for every fixed injection cycle. The injection valve 31 directly injects the urea aqueous solution into the exhaust pipe 11, and is attached to the exhaust pipe 11 so that the injection hole faces the exhaust pipe 11.

<3. Configuration of control device (abnormality diagnosis device)>
Next, the structural example of the control apparatus 100 of the reducing agent injection apparatus 30 which concerns on this embodiment is demonstrated. The control device 100 includes a processor such as a CPU (Central Processing Unit), a storage element that stores a program executed by the processor, a drive circuit for the pump 41 and the injection valve 31, and the like. FIG. 2 is a block diagram functionally showing the configuration of the control device 100. In the present embodiment, the control device 100 corresponds to the abnormality diagnosis device of the present invention.

  The control device 100 includes a control unit 110, a storage unit 140, an injection valve driving unit 150, and a pump driving unit 160. The control unit 110 may be configured by, for example, a microcomputer or a microprocessor unit, may be configured by an updatable component such as firmware, and is further executed by a command from the CPU or the like. It may be a module or the like. Sensor signals from the pressure sensor 43 and the temperature sensors 21 and 23 are input to the control device 100. Further, the control device 100 can acquire information on the operating state of the internal combustion engine 5 such as the fuel injection amount, fuel injection timing, and engine speed of the internal combustion engine 5 directly or via communication means such as CAN. Yes.

  The storage unit 140 includes a storage element (not shown) such as a random access memory (RAM) or a read only memory (ROM). The storage unit 140 may include other storage media such as a CD-ROM and a storage device. The storage unit 140 stores programs executed by the control unit 110, various parameters used for calculation processing, calculation results, detection results, and the like. The injection valve driving unit 150 and the pump driving unit 160 are configured by an electric circuit. The injection valve drive unit 150 outputs a drive signal to the injection valve 31 based on a drive instruction signal from the control unit 110. The pump drive unit 160 outputs a drive signal to the pump 41 based on a drive instruction signal from the control unit 110.

  The control unit 110 includes a pressure detection unit 112, a sticking determination unit 114, a return control unit 116, a return determination unit 118, an injection valve control unit 120, and a pump control unit 122. Each of these units may be a function realized by the control unit 110 executing a program.

  The pressure detector 112 detects the pressure Pu of the urea aqueous solution supplied to the injection valve 31 based on the sensor signal of the pressure sensor 43.

  The pump control unit 122 controls the output of the pump 41. The pump control unit 122 feedback-controls the output of the pump 41 so that the pressure Pu detected by the pressure detection unit 112 becomes a preset target value Ptgt. For example, the pump control unit 122 performs PID control on the output of the pump 41 based on the difference ΔP between the detected pressure Pu and the target value Ptgt. Since the pressure Pu of the urea aqueous solution is likely to decrease as the injection amount of the urea aqueous solution from the injection valve 31 increases, the pump control unit 122 determines the urea aqueous solution in order to maintain the pressure Pu of the urea element solution at the target value Ptgt. The larger the injection amount, the larger the output of the pump 41 is set.

  For example, the pump control unit 122 sets a duty ratio that is a ratio of the energization time to the total time of the processing cycle for each fixed processing cycle. In this case, the output of the pump 41 increases as the duty ratio increases. The pump control unit 122 outputs a drive instruction signal to the pump drive unit 160 based on the set duty ratio. The pump drive unit 160 performs energization control of the pump 41 in accordance with the input drive instruction signal. The pump drive unit 160 is provided with an ammeter for measuring the current value supplied to the pump 41. The ammeter may be an ammeter using a shunt resistor, for example.

  FIG. 3 shows the relationship between the indicated value of the injection amount of the urea aqueous solution injected from the injection valve 31 and the output of the pump 41. The output of the pump 41 increases as the instruction value for the injection amount increases. In other words, since the pressure Pu of the urea aqueous solution is difficult to decrease when the injection valve 31 is closed and fixed, the output of the pump 41 is small. On the other hand, when the injection valve 31 is open and fixed, the pressure Pu of the urea aqueous solution is It is always in a state of being easily lowered, and the output of the pump 41 is maintained at a large value.

  The injection valve control unit 120 performs drive control of the injection valve 31. As described above, since the pressure Pu of the urea aqueous solution supplied to the injection valve 31 is controlled to be the target value Ptgt, the injection valve control unit 120 sets the pressure Pu of the urea aqueous solution to the target value Ptgt. As a premise, the valve opening time of the injection valve 31 is controlled according to the instruction value of the injection amount.

For example, the injection valve control unit 120 obtains the amount of ammonia necessary for reducing NO _x in the exhaust gas of the internal combustion engine 5. The amount of the NO _X in the exhaust gas, for example, the NO _X concentration detected by the NO _X concentration or NO _X sensor is estimated based on the operating state of the internal combustion engine 5, NO _X obtained by multiplying the flow rate of the exhaust gas An amount may be used.

Further, the injection valve control unit 120 obtains an excess / deficiency ammonia amount with respect to a target adsorption amount of ammonia in the selective reduction catalyst 13. As the target adsorption amount of ammonia in the selective reduction catalyst 13, for example, a value obtained by multiplying the target adsorption rate by the adsorbable amount according to the temperature of the selective reduction catalyst 13 estimated based on the exhaust temperature Tgas is used. The target adsorption rate may be, for example, 70 to 80%. If the target adsorption rate is 70 to 80%, the adsorption rate is kept relatively high and the NO _x reduction efficiency is kept high, while ammonia can be adsorbed even when the catalyst temperature rises rapidly. The amount is less likely to fall below the actual ammonia adsorption amount. The injection valve control unit 120 obtains an excess / deficiency ammonia amount based on the difference between the current ammonia adsorption amount and the target adsorption amount obtained by integration.

The injection valve control unit 120 adds the ammonia amount necessary for reducing NO _x in the exhaust gas and the ammonia amount that is excessive or insufficient with respect to the target adsorption amount of the selective reduction catalyst 13. The injection valve control unit 120 outputs a drive instruction signal to the injection valve driving unit 150 with the amount of urea aqueous solution that can generate the calculated ammonia amount as the target injection amount. The injection valve drive unit 150 performs energization control of the injection valve 31 in accordance with the input drive instruction signal. The injection valve driving unit 150 is provided with an ammeter for measuring a current value supplied to the injection valve 31. The ammeter may be an ammeter using a shunt resistor, for example. By performing the urea aqueous solution injection control in this way, the ammonia adsorption rate in the selective reduction catalyst 13 is maintained high while the ammonia outflow to the downstream side of the selective reduction catalyst 13 is suppressed, and the NO _x reduction efficiency. Can be improved.

  The sticking determination unit 114 determines whether the injection valve 31 is stuck open. The method for determining whether or not the injection valve 31 is stuck open is not particularly limited. For example, the sticking determination unit 114 can determine whether or not the injection valve 31 is stuck open using the output of the pump 41.

  When it is determined that the injection valve 31 is stuck, the return control unit 116 performs control for eliminating the sticking. For example, the return control unit 116 attempts to eliminate the sticking of the valve body by causing a liquid urea aqueous solution to reach the injection valve 31. When the valve body is fixed by crystallization of the urea aqueous solution, the crystal is melted by the liquid urea aqueous solution, and the injection valve 31 is not fixed. For example, the return control unit 116 repeats the supply of the urea aqueous solution to the second reducing agent passage 57 and the recovery of the urea aqueous solution from the second reducing agent passage 57 to the storage tank 50. Thus, even when the injection valve 31 is closed and stuck, the liquid urea aqueous solution can reach the injection valve 31. However, the method for eliminating the sticking of the injection valve 31 is not limited to the above example. In addition, since the sticking of the valve body may be resolved naturally, the return control unit 116 is not an essential element in the present invention.

  The return determination unit 118 determines whether or not the open sticking of the injection valve 31 has been eliminated when the sticking determination unit 114 determines that the open sticking of the injection valve 31 has occurred. For example, the return determination unit 118 determines whether or not the open sticking has been eliminated while a preset time or number of determinations has elapsed after it is determined that the open sticking of the injection valve 31 has occurred. Specifically, in this embodiment, the return determination unit 118 sets the instruction value for the injection amount of the urea aqueous solution by the injection valve 31 to be equal to or less than the reference value after determining that the injection valve 31 is stuck open. Based on the output of the pump 41, it is determined whether or not the open sticking has been eliminated.

  Usually, since the output of the pump 41 decreases due to the cancellation of the open sticking of the injection valve 31, the return determination unit 118 determines that the open sticking has been canceled due to the decrease of the output of the pump 41. However, in a state where the normal injection control of the urea aqueous solution is continued, when the indication value of the injection amount at the time of determining whether or not the open sticking is eliminated, it is determined whether or not the open sticking is eliminated. There are cases where it is not possible. That is, the output of the pump 41 is increased when the injection valve 31 is stuck open, while the output of the pump 41 is increased even when the injection amount instruction value is large. The accuracy is reduced.

  Specifically, FIGS. 4 and 5 show changes in the output of the pump 41 due to cancellation of the open sticking of the injection valve 31 when the indication value of the injection amount of the urea aqueous solution is small and large, respectively. . As shown in FIG. 4, when the indicated value of the injection amount of the urea aqueous solution is small, the actual injection amount is large and the output of the pump 41 is relatively large when the injection valve 31 is stuck open. . On the other hand, since the injection amount becomes smaller as the open sticking of the injection valve 31 is eliminated, the output of the pump 41 is reduced to a relatively small value. For this reason, since the change amount ΔP of the output of the pump 41 becomes relatively large, it is easy to determine the cancellation of the open fixation based on the output of the pump 41.

  On the other hand, as shown in FIG. 5, when the indication value of the injection amount of the urea aqueous solution is large, the actual injection amount is large in both cases before and after the open sticking of the injection valve 31 is eliminated, and therefore the pump 41 The change amount ΔP of the output becomes smaller. For this reason, it is likely that it is difficult to determine the cancellation of the open sticking based on the output of the pump 41. Therefore, in the present embodiment, the return determination unit 118 determines whether or not the open sticking has been eliminated based on the output of the pump 41 in a state where the indication value of the injection amount of the urea aqueous solution from the injection valve 31 is set to a small value or zero. Determine.

  FIG. 6 shows changes in the output of the pump 41 according to the present embodiment. The return determination unit 118 sets the instruction value of the injection amount to a small value or zero even if the instruction value of the injection amount of the urea aqueous solution when it is determined that the injection valve 31 is stuck open is large. Then, it is determined whether or not the open sticking has been eliminated. For this reason, the change amount ΔP of the output of the pump 41 when the open sticking of the injection valve 31 is eliminated becomes relatively large, and the cancellation of the open sticking can be easily determined based on the output of the pump 41.

<4. Flow chart>
Next, an example of an abnormality diagnosis method for the reducing agent injection device 30 executed by the control device (abnormality diagnosis device) 100 according to the present embodiment will be described with reference to FIG. In addition, the following flowchart demonstrates the process which determines whether the said open sticking was eliminated when the open sticking has arisen in the injection valve 31. FIG. Further, the following flowchart may be executed at a preset time interval after activation of the control device 100, or may be executed repeatedly at all times.

  First, the sticking determination unit 114 of the control unit 110 performs a determination process as to whether or not the open sticking of the injection valve 31 has occurred (step S11). The method for determining whether or not the injection valve 31 is stuck open is not particularly limited. For example, the sticking determination unit 114 can determine whether or not the injection valve 31 is stuck open using the output of the pump 41. Hereinafter, an example of a method by which the sticking determination unit 114 determines whether either the open sticking or the closed sticking of the injection valve 31 has occurred will be described.

  For example, the sticking determination unit 114 determines whether or not the injection valve 31 is stuck based on the current waveform energized in the injection valve 31 and the output of the pump 41 after the urea aqueous solution injection control is started. Specifically, the sticking determination unit 114 acquires a current waveform energized to the injection valve 31 and an output of the pump 41 in a state where the urea aqueous solution injection control is being executed. The sticking determination unit 114 determines whether or not the valve body is stuck by judging whether or not the valve body is moving based on the acquired current waveform. Further, when the sticking determination unit 114 determines that the valve body is sticking, the sticking determination unit 114 determines whether the sticking is open sticking or closed sticking based on the output of the pump 41.

  FIG. 8 shows the difference in the current waveform of the injection valve 31 depending on whether or not the valve body is stuck. As the amount of current supplied to the electromagnetic coil of the injection valve 31 increases, the magnetic force attracting the valve element increases, and the valve element moves. If the valve body is not fixed (solid line), increasing the energization amount will cause the current value to decrease once when the valve body starts to move or when the valve body reaches the maximum lift position. A change point appears in the waveform. On the other hand, when the valve body is firmly attached (broken line), the valve body does not move even if the energization amount is increased, and therefore no change point appears in the current waveform.

  When the change point does not appear in the current waveform of the injection valve 31, that is, when the valve body is fixed, the fixing determination unit 114 determines whether the fixing is open fixing or closed fixing based on the output of the pump 41. FIG. 9 shows the output of the pump 41 in a state where the injection valve 31 is fixed in an open state or in a closed state. As described above, the output of the pump 41 is large when the injection valve 31 is firmly fixed, and the output of the pump 41 is small when the injection valve 31 is firmly closed. The output of the pump 41 is constant regardless of whether the injection valve 31 is fixed open or closed, but the output when the injection valve 31 is fixed open is larger than the output when the injection valve 31 is fixed closed. Therefore, the sticking determination unit 114 can determine whether the injection valve 31 is open or closed based on the output of the pump 41.

  Next, the sticking determination unit 114 determines whether or not the injection valve 31 is stuck open (step S13), and when the injection valve 31 is not stuck firmly (S13: No), the control device 100 performs the main control. End the routine. On the other hand, when the open sticking of the injection valve 31 has occurred (S13: Yes), the return determination unit 118 sets the instruction value for the injection amount of the urea aqueous solution from the injection valve 31 to a reference value or less (step S15). The reference value that can be said to be the upper limit of the instruction value of the injection amount of the aqueous urea solution can be a value corresponding to an injection amount at which the duty ratio in the drive control of the injection valve 31 is 30%, for example. The reference value may be a value that ensures that the output of the pump 41 after setting the injection amount instruction value is surely lower than the output of the pump 41 in a state where the injection valve 31 is in the open fixing state.

  For example, in the next step S <b> 17, the return determination unit 118 uses the output of the pump 41 to determine whether or not the open sticking of the injection valve 31 has been eliminated, the injection amount of the urea aqueous solution from the injection valve 31 is determined. In setting the command value to be equal to or less than the reference value, the command value for the injection amount may be set to zero. The instruction value of the injection amount of the injection valve 31 may be a value that is surely smaller than the injection amount when the injection valve 31 is stuck open.

  In the next step S17, the return determination unit 118 determines whether or not the open sticking of the injection valve 31 has been eliminated based on the output of the pump 41 and the current waveform of the injection valve 31. The indication value of the injection amount of the urea aqueous solution by 31 is set to a value that is below the reference value and exceeds zero. When the injection determination value is set to a value exceeding zero, the return determination unit 118 is equal to or greater than the injection amount when the valve body of the injection valve 31 moves to the extent that the change point appears in the current waveform of the injection valve 31. Set to injection amount.

  In addition, when the return determination unit 118 sets the instruction value for the injection amount of the urea aqueous solution to be equal to or less than the reference value, not only the instruction value for the injection amount decreases but also the instruction value for the injection amount may increase. For example, even if the target injection amount calculated by the injection valve control unit 120 when the return determination unit 118 sets the instruction value for the injection amount of the urea aqueous solution is zero, the return determination unit 118 The instruction value for the injection amount may be set to a value equal to or less than the reference value and greater than zero.

  At this time, the return control unit 116 may execute control for eliminating the open sticking of the injection valve 31. For example, the return control unit 116 attempts to eliminate the sticking of the valve body by causing a liquid urea aqueous solution to reach the injection valve 31. When the valve body is fixed by crystallization of the urea aqueous solution, the crystal is melted by the liquid urea aqueous solution, and the sticking of the valve body is eliminated. However, the method of canceling the open sticking of the injection valve 31 is not limited to the above example. Moreover, since the open sticking of the injection valve 31 may be canceled naturally, in the present invention, the control for canceling the open sticking by the return control unit 116 is not an essential element.

  Next, the return determination unit 118 determines whether or not the open sticking of the injection valve 31 has been eliminated based on the output of the pump 41 (step S17). For example, the return determination unit 118 may determine the decrease in the output of the pump 41 based on the duty ratio in the drive control of the pump 41. For example, the return determination unit 118 may determine whether or not the duty ratio of the pump 41 is less than a predetermined determination threshold value. In this case, the determination threshold value is smaller than the duty ratio of the pump 41 that is assumed when the injection valve 31 is stuck open, and when the instruction value for the injection amount of the urea aqueous solution is set to a small value. It is set to a value larger than the duty ratio of the pump 41 assumed in the above.

  Further, when determining the decrease in the output of the pump 41, the return determination unit 118 may determine based on a comparison of the output of the pump 41 before and after the instruction value of the injection amount of the urea aqueous solution is set to a reference value or less. At this time, the return determination unit 118 may compare the average output (kW) of the pump 41 at the reference time before and after the instruction value of the injection amount is set to the reference value or less. In this case, the return determination unit 118 determines whether or not a value obtained by subtracting the output of the pump 41 after the decrease of the injection amount instruction value from the output of the pump 41 before the decrease of the injection amount instruction value exceeds a preset threshold value. It may be determined. Alternatively, the return determination unit 118 determines whether or not the rate of decrease in the output of the pump 41 after the decrease in the instruction value of the injection amount with respect to the output of the pump 41 before the decrease in the instruction value of the injection amount exceeds a preset threshold value. May be.

  Further, when the instruction value for the injection amount is set to a value exceeding zero in step S15, the return determination unit 118 adheres the valve body based on the current waveform of the injection valve 31 together with the determination process based on the output of the pump 41. It may be determined whether it is not. In this case, as in the case of the sticking determination described above, the valve body sticks depending on whether or not the change point of the current waveform that appears when the valve body starts moving or when the valve body reaches the maximum lift position. Can be determined. Thereby, it can be determined with higher accuracy that the open sticking of the injection valve 31 has been eliminated.

  Next, the return determination unit 118 determines whether or not the open sticking of the injection valve 31 has been eliminated (step S19). If it is determined that the open sticking has been eliminated (S19: Yes), the control device 100 performs this routine. Exit. On the other hand, when it is determined that the open fixation has not been resolved (S19: No), the return determination unit 118 adds 1 to the value of the counter that counts the determination process (step S21). Next, the return determination unit 118 determines whether or not the counter value has reached a preset threshold value (step S23). When the value of the counter has not reached the threshold value (S23: No), the return determination unit 118 returns to step S17 and repeats the processing of each step along the above-described procedure.

  On the other hand, when the value of the counter reaches the threshold value (S23: Yes), after the open sticking of the injection valve 31 is detected, the open sticking is not canceled even after a certain time has passed, so the return is restored. The determination unit 118 determines that an error has occurred in the injection valve 31 (step S25), and ends this routine. The return determination unit 118 determines whether or not the open sticking has been eliminated before the preset time elapses, in addition to determining whether or not the open sticking has been eliminated while the preset number of judgments has elapsed. You may judge.

  As described above, the control device (abnormality diagnosis device) 100 of the reducing agent injection device 30 according to this embodiment determines whether or not the open sticking has been eliminated after it is determined that the sticking of the injection valve 31 has occurred. When this is determined, the instruction value of the injection amount of the urea aqueous solution from the injection valve 31 is set to a reference value or less. For this reason, the change amount ΔP of the output of the pump 41 before and after the open sticking of the injection valve 31 is eliminated can be increased. Thereby, based on the output of the pump 41, it is possible to easily determine whether or not the open sticking of the injection valve 31 is eliminated.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, it is determined whether the open sticking of the injection valve 31 has been eliminated based on the output of the pump 41 when the indication value of the injection amount of the injection valve 31 is reduced. It can also be determined whether or not the open sticking 31 has been eliminated. The return determination unit 118 reduces the output value of the pump 41 while interrupting feedback control of the pressure Pu of the aqueous urea solution supplied to the injection valve 31 after reducing the instruction value of the injection amount of the injection valve 31. It may be determined whether or not the open sticking of the injection valve 31 has been eliminated based on the rate of decrease of the pressure Pu. When the open sticking of the injection valve 31 is not eliminated, the pressure Pu is reduced at a relatively high speed, whereas when the open sticking of the injection valve 31 is eliminated, the rate of reduction of the pressure Pu is reduced. In this way, it is also possible to determine whether or not the open sticking has been eliminated based on the decreasing speed of the pressure Pu of the urea aqueous solution.

DESCRIPTION OF SYMBOLS 5 Internal combustion engine 10 Urea SCR system 11 Exhaust pipe 13 Selective reduction catalyst 30 Reducing agent injection apparatus 31 Injection valve 41 Pump 100 Control apparatus (abnormality diagnosis apparatus)
110 Control Unit 114 Adherence Determination Unit 118 Return Determination Unit 120 Injection Valve Control Unit 122 Pump Control Unit

Claims (6)

In the abnormality diagnosis device for diagnosing abnormality of the reducing agent injection device that injects the reducing agent pumped by the pump into the exhaust passage by an injection valve provided in the exhaust passage of the internal combustion engine,
A pump controller that controls the output of the pump so that the supply pressure of the reducing agent to the injection valve is maintained at a target value;
A sticking determination unit that determines whether or not the injection valve is stuck in an open state;
When it is determined that the injection valve is stuck in the open state, the indication value of the reducing agent injection amount is set to a reference value or less, and the output of the pump in the open state is determined based on the output of the pump. A return determination unit for determining whether or not the sticking has been eliminated;
An abnormality diagnosis device for a reducing agent injection device.   The return determination unit determines whether or not the sticking in the valve-opened state has been eliminated based on a comparison of output of the pump before and after setting an instruction value of the injection amount to a reference value or less. An abnormality diagnosis device for a reducing agent injection device according to claim 1.   The abnormality diagnosis device for a reducing agent injection device according to claim 1, wherein the return determination unit uses an average value of the pump output over a predetermined time as the output of the pump. The pump is a pump of a type in which the output is controlled by controlling the duty ratio, which is the ratio of the energization time to the total time of a certain processing cycle,
The return determination unit determines whether or not the sticking in the valve-open state has been eliminated based on a comparison between a duty ratio of the pump and a determination threshold value in a state where the instruction value of the injection amount is set to a reference value or less. The abnormality diagnosis device for a reducing agent injection device according to claim 1, wherein the abnormality diagnosis device determines. The injection valve is a valve of a type in which the injection amount is controlled by controlling the duty ratio, which is the ratio of the energization time to the total time of a fixed injection cycle,
The return determination unit fixes an instruction value of the injection amount of the reducing agent so that a change point of the current waveform due to movement of the valve body of the injection valve appears, and based on the current waveform together with the output of the pump The abnormality diagnosis device for a reducing agent injection device according to any one of claims 1 to 4, wherein it is determined whether or not the sticking in the valve open state has been eliminated. In an abnormality diagnosis method for diagnosing abnormality of a reducing agent injection device that injects reducing agent pumped by a pump into the exhaust passage by an injection valve provided in an exhaust passage of an internal combustion engine,
Controlling the output of the pump so that the supply pressure of the reducing agent to the injection valve is maintained at a target value;
Determining whether the injection valve is stuck in an open state; and
When it is determined that the injection valve is stuck in the open state, the indication value of the reducing agent injection amount is set to a reference value or less, and the output of the pump in the open state is determined based on the output of the pump. Determining whether the sticking has been resolved;
An abnormality diagnosis method for a reducing agent injection device, comprising:

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