JP2011149365A - Leakage diagnostic device and leakage diagnostic method for reducing agent injection valve, and exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage diagnostic device and a leakage diagnostic method for a reducing agent injection valve and an exhaust emission control device for an internal combustion engine, detecting abnormal leakage from the reducing agent injection valve of a reducing agent injection device. <P>SOLUTION: This leakage diagnostic device detects abnormality of the reducing agent injection valve in the exhaust emission control device including a pump for forcibly feeding a reducing agent regenerating ammonia, the reducing agent injection valve injecting the reducing agent forcibly fed by the pump into the exhaust pipe of the internal combustion eigne, a reducing catalyst converting NO<SB>x</SB>in exhaust gas by the use of the ammonia, and an ammonia sensor provided downstream from the reducing catalyst and detecting the concentration of the ammonia in exhaust gas. The leakage diagnostic device includes: a reducing agent injection valve control means determining the valve opening time of the reducing agent injection valve based on the target injection quantity of the reducing agent and controlling opening/closing of the reducing agent injection valve; and a leakage determination means detecting the abnormal leakage from the reducing agent injection valve when the concentration of the ammonia is equal to or higher than a predetermined concentration and the valve opening time is less than a predetermined time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a leak diagnosis device and a leak for diagnosing the presence or absence of leakage of a reducing agent from a reducing agent injection valve that injects a reducing agent for purifying nitrogen oxides in exhaust gas into an exhaust passage of an internal combustion engine. The present invention relates to a diagnostic method and an exhaust gas purification device for an internal combustion engine provided with such a leakage diagnostic device.

Conventionally, exhaust gas exhausted from an internal combustion engine mounted on a vehicle or the like may contain nitrogen oxides (NO _x ). As one of the exhaust gas purification devices that purify this NO _x , a reducing agent is injected upstream of the reduction catalyst provided in the exhaust passage of the internal combustion engine, and the reduction reaction between the reducing agent and NO _x is promoted by the catalyst, Some are configured to decompose NO _x into nitrogen, water, carbon dioxide, etc. and release it into the atmosphere.

As such an exhaust purification device, there is a urea SCR (Selective Catalyst Reduction) system using urea aqueous solution or ammonia water as a reducing agent. In the urea SCR system, a NO _x selective reduction catalyst having an ammonia adsorption function is used, and ammonia produced by hydrolysis of the catalyst reducing agent is adsorbed by the reduction catalyst, and NO _{x in} exhaust gas flowing into the catalyst is absorbed. Is purified by reacting with ammonia.

In this urea SCR system, the amount of ammonia that can be adsorbed on the reduction catalyst is determined by the catalyst temperature, and when excess reducing agent is injected into the exhaust passage, part of the generated ammonia is adsorbed on the reduction catalyst. It flows out to the downstream side without. Therefore, the injection amount of the reducing agent is calculated in consideration of the amount of NO _x in the exhaust gas discharged from the internal combustion engine and the amount that can be adsorbed by the reduction catalyst.

  However, there is a possibility that some kind of abnormality occurs in the reducing agent injection valve due to deterioration of the seat portion of the valve body with time, attachment of relics, open fixing of the valve body, etc., and leakage of the reducing agent from the reducing agent injection valve into the exhaust passage. When such a leakage of the reducing agent occurs, the reducing agent is supplied into the exhaust passage even during a period other than the reducing agent injection period, and ammonia introduced into the reduction catalyst becomes excessive. Therefore, it is desired that the urea SCR system includes a diagnostic unit that can detect the leakage when the leakage from the reducing agent injection valve occurs.

Here, while the air-fuel ratio of the exhaust gas adsorbs NO _X in the state of fuel-lean, with the _the NO _X storage reduction catalyst air-fuel ratio leaves the NO _X in the state of the fuel-rich, unburned fuel as a reducing agent (HC There is a device for diagnosing a leakage abnormality of the reducing agent injection valve in the exhaust gas purification device that injects the gas. Specifically, the transition state of the air-fuel ratio sensor provided on the downstream side of the reducing agent injection valve and the measured air-fuel ratio detected by the air-fuel ratio sensor when the addition from the reducing agent injection valve is not executed is reduced. A leakage abnormality diagnosing means for diagnosing that the reducing agent injection valve has a leakage abnormality when the air-fuel ratio transition state indicating a reducing agent leakage from the agent injection valve is indicated; An abnormality diagnosis device is disclosed that includes a rich request diagnosis response unit that prohibits a diagnosis process by a leakage abnormality diagnosis unit when a request occurs (see Patent Document 1).

Japanese Patent Laying-Open No. 2005-232991 (full text, full figure)

Abnormality diagnosis apparatus Patent Document 1 described above, comprises the air-fuel ratio of the exhaust gas while adsorbing NO _X in the state of fuel-lean, the _the NO _X storage reduction catalyst air-fuel ratio leaves the NO _X in the state of the fuel rich exhaust Intended for purification equipment. In such an exhaust emission control device, the amount of HC contained in the exhaust gas in addition to the HC added from the reducing agent injection valve increases and decreases, so that leakage abnormality is diagnosed while considering the presence or absence of a rich request for the internal combustion engine. And a means for responding to a rich request diagnosis is provided.

  On the other hand, ammonia is not contained in the exhaust gas, so in the urea SCR system, the amount of ammonia flowing into the reduction catalyst can be estimated from the amount of reducing agent injected from the reducing agent injection valve, There is no need to consider the operating state of the internal combustion engine. In the urea SCR system, the amount of the reducing agent that can be adsorbed on the reducing catalyst varies depending on the catalyst temperature, and the ammonia concentration on the downstream side of the reducing catalyst does not leak even though the reducing agent leaks from the reducing agent injection valve. Since there is a risk of increase, it is not easy to diagnose leakage of the reducing agent injection valve only by the ammonia concentration.

  Accordingly, the inventors of the present invention have made diligent efforts and diagnosed the presence or absence of leakage of the reducing agent from the reducing agent injection valve based on the information on the ammonia concentration downstream of the reduction catalyst and the instructed injection amount of the reducing agent. It has been found that such problems can be solved, and the present invention has been completed. That is, the present invention provides a leakage diagnosis device and leakage diagnosis method for a reducing agent injection valve and an exhaust purification device for an internal combustion engine that can accurately diagnose the presence or absence of leakage of the reducing agent from the reducing agent injection valve. Objective.

According to the present invention, a reduction catalyst for purifying NO _X in the exhaust gas using ammonia, a reducing agent injection valve for injecting the upstream side of the exhaust passage than ammonia capable of producing a reducing agent reducing catalyst, In a reducing agent injection valve leakage diagnosis device for diagnosing the presence or absence of leakage of a reducing agent from a reducing agent injection valve in a reducing agent injection device equipped with a reducing agent injection valve, the opening and closing of the reducing agent injection valve based on an indicated injection amount of the reducing agent Reducing agent injection valve control means for controlling the ammonia, ammonia concentration detecting means for detecting the ammonia concentration in the exhaust gas on the downstream side based on the sensor signal of the sensor provided downstream of the reduction catalyst, and the instruction of the reducing agent A leakage determination device for a reducing agent injection valve, comprising: leakage determination means for determining presence or absence of leakage of the reducing agent from the reducing agent injection valve based on information on an injection amount and ammonia concentration Is, it is possible to solve the problems described above.

  In configuring the leakage diagnosis device for a reducing agent injection valve according to the present invention, the reducing agent injection valve control means corrects the amount of reducing agent injected by the reducing agent injection valve so that the ammonia concentration is kept within an allowable range. The leakage determination means determines that there is a leakage of the reducing agent when the ammonia concentration is equal to or higher than the predetermined concentration and the correction coefficient used for correcting the injection amount is less than the predetermined value. preferable.

  Further, in configuring the reducing agent injection valve leakage diagnosis apparatus of the present invention, the leakage determining means is in a state where the ammonia concentration is equal to or higher than a predetermined concentration, and the indicated injection amount or the correction coefficient of the reducing agent is less than a predetermined value. It is preferable to determine that there is leakage of the reducing agent when is continued for a predetermined time or longer.

  In configuring the leakage diagnosis device for the reducing agent injection valve according to the present invention, it is preferable to stop the operation of the reducing agent injection device when the leakage determination means determines that there is a leakage of the reducing agent.

Another aspect of the present invention is a reduction catalyst that purifies NO _{x in} exhaust gas using ammonia, and a reducing agent that injects a reducing agent capable of generating ammonia into an exhaust passage upstream of the reducing catalyst. In a reducing agent injection valve leakage diagnosis method for diagnosing whether or not a reducing agent leaks from a reducing agent injection valve in a reducing agent injection device having an injection valve, the reduction catalyst is read while reading the indicated injection amount of the reducing agent The reduction is characterized by detecting the ammonia concentration in the exhaust gas on the downstream side, and determining whether or not there is leakage of the reducing agent from the reducing agent injection valve based on the information on the instructed injection amount of the reducing agent and the ammonia concentration This is a method for diagnosing leakage of the agent injection valve.

  Yet another aspect of the present invention is an exhaust emission control device for an internal combustion engine, comprising the leakage diagnosis device for any of the reducing agent injection valves described above.

  According to the leakage diagnosis device and leakage diagnosis method for a reducing agent injection valve and the exhaust gas purification device for an internal combustion engine according to the present invention, the reducing agent injection valve is configured based on the ammonia concentration downstream of the reduction catalyst and the indicated injection amount of the reducing agent. Since the presence or absence of leakage of the reducing agent is diagnosed, it is possible to quickly detect the leakage when the reducing agent leaks from the reducing agent injection valve. Therefore, ammonia can be prevented from being released into the atmosphere until the reducing agent injection valve is replaced by stopping the operation of the reducing agent injection device.

  Further, in the reducing agent injection valve leakage diagnosis apparatus of the present invention, the reducing agent injection valve control means is configured to correct the injection amount of the reducing agent so that the ammonia concentration is suppressed within an allowable range, and the leakage determination means. However, when the ammonia concentration is equal to or higher than the predetermined concentration and the correction coefficient of the injection amount is less than the predetermined value, it is determined that there is a leakage of the reducing agent, so that the injection amount and the ammonia concentration are inconsistent. In addition, leakage of the reducing agent injection valve can be detected.

  Further, in the leakage diagnosis device for a reducing agent injection valve according to the present invention, the state in which the leakage determination means has the ammonia concentration equal to or higher than the predetermined concentration and the indicated injection amount or the correction coefficient is lower than the predetermined value continues for the predetermined time or more. Sometimes it is determined that there is a leakage of the reducing agent, and it is determined that there is a leakage of the reducing agent when the ammonia concentration temporarily increases, regardless of the leakage of the reducing agent from the reducing agent injection valve. Nothing will happen. Therefore, the possibility of erroneous determination of the presence or absence of leakage of the reducing agent from the reducing agent injection valve is reduced.

  Further, in the reducing agent injection valve leakage diagnosis apparatus of the present invention, when it is determined that there is a reducing agent leakage, the operation of the reducing agent injection device is stopped, thereby reducing the reducing agent leakage from the reducing agent injection valve. After detection, the amount of ammonia flowing out downstream of the reduction catalyst can be suppressed.

It is a figure showing an example of composition of an exhaust-air-purification device concerning an embodiment of the invention. It is a block diagram which shows the structural example of the control apparatus (leakage diagnostic apparatus of a reducing agent injection valve) concerning embodiment of this invention. It is a time chart for demonstrating an example of the leakage diagnosis method of the reducing agent injection valve of this embodiment. It is a flowchart for demonstrating an example of the leakage diagnosis method of the reducing agent injection valve of this embodiment.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to a reducing agent injection valve leakage diagnosis apparatus and leakage diagnosis method and an internal combustion engine exhaust gas purification apparatus according to the present invention will be specifically described below with reference to the drawings as appropriate. However, the following embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention. In addition, what attached | subjected the same code | symbol in each figure has shown the same member, and description is abbreviate | omitted suitably.

1. FIG. 1 shows an example of the configuration of an exhaust emission control device 10 for an internal combustion engine according to an embodiment of the present invention. This exhaust purification device 10 is connected to the exhaust passage of the internal combustion engine 5, and includes a reduction catalyst 20, a reducing agent injection device 30, a control device 60, and the like, and in exhaust gas discharged from the internal combustion engine 5. of NO _X, and is configured as a urea SCR system for purifying using aqueous urea solution as a reducing agent. However, the reducing agent that can be used in the present invention is not limited to the urea aqueous solution, and may be any one that generates ammonia, such as ammonia water.

Reduction catalyst 20 used in the exhaust gas purifying apparatus 10 of the present embodiment, the ammonia injected urea solution into the exhaust passage is generated by hydrolyzing adsorbed to promote the reduction reaction of ammonia with NO _X It has a function. A known catalyst is appropriately used as the reduction catalyst 20.

  Further, a sensor 14 for detecting the ammonia concentration in the exhaust gas is provided on the downstream side of the reduction catalyst 20. The sensor signal of the sensor 14 is transmitted to the control device 60, and the control device 60 calculates the ammonia concentration in the exhaust gas based on the sensor signal. In this embodiment, an ammonia sensor is used as the sensor 14, but the type of sensor is not particularly limited as long as the ammonia concentration can be obtained by arithmetic processing.

(2) Reducing agent injection device The reducing agent injection device 30 is mainly configured by a storage tank 31, a reducing agent injection valve 34, a pump 41, and the like. The storage tank 31 and the pump 41 are connected by a first reducing agent supply passage 57, and the pump 41 and the reducing agent injection valve 34 are connected by a second reducing agent supply passage 58. Among these, the pressure sensor 43 is provided in the second reducing agent supply passage 58. The sensor signal of the pressure sensor 43 is transmitted to the control device 60, and the control device 60 calculates the pressure in the second reducing agent supply passage 58 based on this sensor signal.

  Further, a circulation passage 59 that leads to the storage tank 31 is connected to the second reducing agent supply passage 58. The circulation passage 59 is provided with an orifice 45 so as to provide resistance to the flow of the reducing agent returned to the storage tank 31 through the circulation passage 59 and to increase the pressure in the second reducing agent supply passage 58. It has become. As such a reducing agent injection device itself, one having a known configuration can be used.

  The pump 41 is an electric pump that is driven and controlled by the control device 60. In the present embodiment, the pump 41 is configured such that its output is feedback-controlled so that the pressure in the second reducing agent supply passage 58 detected by the pressure sensor 43 is maintained at a predetermined value. .

  The reducing agent injection valve 34 is an electromagnetically driven on / off valve whose opening / closing is controlled by the control device 60, and is fixed to the exhaust pipe 11 upstream of the reduction catalyst 20. The reducing agent injection valve 34 is basically energized and controlled while the pressure in the second reducing agent supply passage 58 is maintained at the target value. Specifically, the amount of reducing agent injected into the exhaust passage is adjusted by setting the valve opening DUTY ratio during a predetermined DUTY cycle in accordance with the instructed injection amount obtained by calculation.

2. Control device (leakage diagnosis device)
FIG. 2 is a functional block of a part relating to control of the reducing agent injection device 30 and a part relating to leakage diagnosis of the reducing agent injection valve 34 in the configuration of the control device 60 provided in the exhaust purification device 10 of the present embodiment. It is a representation.

  The control device 60 includes a pump drive control unit 61, an ammonia concentration detection unit 62, an instruction injection amount calculation unit 63, a reducing agent injection valve control unit 64, and a leak determination unit 65. The control device 60 is mainly configured by a microcomputer having a known configuration, and each means is realized by execution of a program by the microcomputer.

  Further, the control device 60 is provided with storage means (RAM: Random Access Memory) not shown. The storage means stores the calculation results of each means, a data map prepared in advance, and the like.

  The pump drive control means 61 reads the value of the pressure Purea in the second reducing agent passage 58 detected by the pressure sensor 43 and feedback-controls the output of the pump 41 so that the pressure Purea is maintained at a predetermined value. .

  The ammonia concentration detection means 62 continuously reads the sensor signal Sam of the sensor 14 and calculates the ammonia concentration Am in the exhaust gas on the downstream side of the reduction catalyst 20.

  The command injection amount calculation means 63 reads information relating to the operating state such as the exhaust gas temperature Tgas, the catalyst temperature Tcat, the rotational speed Ne of the internal combustion engine 5 and the accelerator operation amount Acc, and calculates the command injection amount Qtgt of the reducing agent. Further, the command injection amount calculation unit 63 of the present embodiment is configured to correct the command injection amount Qtgt based on the ammonia concentration Am detected by the ammonia concentration detection unit 62. Specifically, the command injection amount calculation means 63 obtains a correction coefficient f according to the ammonia concentration Am, and reduces based on the corrected command injection amount Qtgt ′ obtained by multiplying the command injection amount Qtgt by the correction coefficient f. The energization control of the agent injection valve 34 is performed.

  For example, a correction coefficient f of less than 1 is set according to the detected ammonia concentration Am, and the corrected command injection amount Qtgt ′ is set to a value smaller than the calculated command injection amount Qtgt. In the present embodiment, map information indicating the relationship between the ammonia concentration Am and the correction coefficient f is stored in the storage means, and the correction coefficient f that decreases as the ammonia concentration Am increases is selected.

  The correction coefficient f may be multiplied by the valve opening DUTY ratio used for energization control of the reducing agent injection valve 34 instead of being multiplied by the command injection amount Qtgt. The correction coefficient f can be updated every predetermined time or can be constantly updated.

  The reducing agent injection valve control means 64 determines the energization amount and energization timing supplied to the reducing agent injection valve 34 based on the calculated command injection amount Qtgt (Qtgt ′), and DUTY control of energization of the reducing agent injection valve 34. I do. In the present embodiment, the reducing agent injection valve 34 injects the reducing agent for each predetermined cycle while changing the valve opening DUTY ratio during a predetermined DUTY cycle according to the command injection amount Qtgt.

  The leakage determination means 65 determines whether or not there is a leakage of the reducing agent from the reducing agent injection valve 34 based on the detected ammonia concentration Am and information on the reducing agent instruction injection amount Qtgt (Qtgt ′). The leakage determination means 65 has an ammonia concentration Am equal to or higher than the threshold Am0, and the correction coefficient f for correcting the injection amount of the reducing agent is less than the threshold f0, or the indicated injection amount Qtgt (Qtgt ′) When the state of zero continues for a predetermined time tw or more, it is determined that there is a leakage of the reducing agent from the reducing agent injection valve 34.

  That is, in the leak determination means 65, when the reducing agent injection amount from the reducing agent injection valve 34 is small, there is a contradictory state in which a relatively high concentration of ammonia is detected. It is determined that the reducing agent has leaked from the agent injection valve 34.

  In the present embodiment, the leakage determination means 65 detects that the reducing agent leaks from the reducing agent injection valve 34 when the detected ammonia concentration Am is relatively high and the injection amount is low for a predetermined time tw or more. It comes to detect that there is. Therefore, it is avoided that it is determined that the reducing agent leaks from the reducing agent injection valve 34 until the condition is temporarily satisfied regardless of the reducing agent leakage. The predetermined time tw can be set as appropriate. For example, the predetermined time tw is set to a time at which 3 to 5 injection cycles are performed.

A method for determining the presence or absence of leakage of the reducing agent by the leakage determination means 65 of the control device 60 of the present embodiment will be specifically described with reference to the time chart of FIG.
In FIG. 3, the ammonia concentration Am on the downstream side of the reduction catalyst 20 detected by the sensor 14 remains below the threshold value Am0 until time t1 when the reducing agent leakage from the reducing agent injection valve 34 occurs. Further, during this period, since the ammonia concentration Am shows a small value, the correction coefficient f for correcting the command injection amount Qtgt is a value close to 1.0.

  Here, when leakage of the reducing agent from the reducing agent injection valve 34 occurs at time t1, the ammonia concentration Am on the downstream side of the reducing catalyst 20 starts to increase. As the ammonia concentration Am increases, the correction coefficient f for correcting the command injection amount Qtgt decreases. If the increase in the ammonia concentration Am is not due to leakage of the reducing agent from the reducing agent injection valve 34 but is temporary, the ammonia concentration Am does not increase due to the change of the correction coefficient f.

  On the other hand, when the reducing agent leaks from the reducing agent injection valve 34 and the amount of leakage is large, as shown in FIG. The concentration Am continues to rise. Therefore, when the ammonia concentration Am reaches the threshold Am0 and the same state continues from the time t2 when the correction coefficient f becomes less than the threshold f0 until the time t3 after a predetermined time tw has elapsed, the leak determination It is determined by means 65 that there is leakage of the reducing agent from the reducing agent injection valve 34.

  The threshold value Am0 of the ammonia concentration Am can be set as appropriate. For example, the range of the ammonia concentration Am on the downstream side of the reduction catalyst 20 that can be detected in advance when there is no leakage from the reducing agent injection valve 34 is tested. A value larger than the upper limit value of the obtained range can be set as the threshold value Am0. With such a threshold value Am0, when ammonia flows out downstream of the reduction catalyst due to a change in the catalyst temperature Tcat or the like, it may be determined that there is a leakage of the reducing agent from the reducing agent injection valve 34. Is prevented.

  The threshold f0 of the correction coefficient f can be set as appropriate. For example, a value that makes the corrected command injection amount Qtgt 'extremely small can be set as the threshold f0. Specifically, the minimum value among the settable correction coefficients f can be set as the threshold value f0. With such a threshold value f0, when the ammonia concentration Am detected is high despite the fact that the correction coefficient f is set so that the injection amount is minimized at the present time, the leakage of the reducing agent clearly occurs. It can be determined that

  However, the information for determining the state where the injection amount is small can be selected in addition to the correction coefficient f and the command injection amount Qtgt (Qtgt ′). For example, when the valve opening DUTY ratio is less than a predetermined value Also, it is possible to determine a state where the injection amount is small.

  When it is determined that the reducing agent has leaked from the reducing agent injection valve 34, the leakage determination means 65 turns on a warning lamp or transmits a warning sound to give an abnormality to the driver or the like. It is to inform you. At the same time, when it is determined that the reducing agent has leaked, the leakage determination means 65 stops the operation of the reducing agent injection device 30 so that the ammonia flows out downstream of the reduction catalyst 20. It is supposed to stop.

  The control device 60 of the present embodiment is configured so that the command injection amount Qtgt of the reducing agent is corrected based on the ammonia concentration Am detected on the downstream side of the reduction catalyst 20, but the ammonia concentration Am is adjusted to the ammonia concentration Am. Even if the command injection amount Qtgt of the reducing agent is not corrected based on this, the present invention can be applied. Even in this case, the detected ammonia concentration Am is not less than the threshold value Am0 and the command injection amount Qtgt or the valve opening DUTY ratio is less than the threshold value or the command injection amount Qtgt is zero for a predetermined time. When continuing for more than tw, it can be determined that there is leakage of the reducing agent from the reducing agent injection valve 34.

3. Next, an example of a leakage diagnosis method for the reducing agent injection valve 34 performed by the control device 60 of the present embodiment will be described in detail with reference to the flowchart of FIG.

  First, after the ammonia concentration Am is read in Step S1 after the start, a correction coefficient f for correcting the command injection amount Qtgt of the reducing agent is obtained in Step S2. Next, in step S3, information on the operating state such as the exhaust gas temperature Tgas, the catalyst temperature Tcat, the rotational speed Ne of the internal combustion engine 5 and the accelerator operation amount Acc is read. In step S4, the information read in step S3 and in step S2 are read. Based on the obtained correction coefficient f, a command injection amount Qtgt (Qtgt ′) of the reducing agent is calculated. In step S5, reducing agent injection control is executed in accordance with the command injection amount Qtgt (Qtgt ').

  Next, in step S6, it is determined whether or not the ammonia concentration Am read in step S1 is greater than or equal to a threshold value Am0. If the ammonia concentration Am is less than the threshold value Am0, the process proceeds to step S13, where it is determined that there is no leakage of the reducing agent from the reducing agent injection valve 34. In step S14, the timer is stopped if the timer is operating. Later, this routine is terminated and the process returns to the start. On the other hand, if the ammonia concentration Am is greater than or equal to the threshold value Am0, the process proceeds to step S7, and it is determined whether or not the correction coefficient f obtained in step S2 is less than the threshold value f0.

  If the correction coefficient f is equal to or greater than the threshold value f0, the process proceeds to step S13, where it is determined that there is no leakage of the reducing agent from the reducing agent injection valve 34, and if the timer is operating in step S14, the timer After stopping, this routine is finished and the process returns to the start. On the other hand, if the correction coefficient f is less than the threshold value f0, the process proceeds to step S8 to determine whether or not the timer is operating. If the timer is not operating, the process proceeds to step S9. After the timer is operated, this routine is terminated and the process returns to the start.

  On the other hand, if the timer is operating, the process proceeds to step S10, and it is determined whether or not the timer value has passed a predetermined time tw. If the timer value has not passed the predetermined time tw, this routine is terminated and the process returns to the start. On the other hand, if the timer value has passed the predetermined time tw, the process proceeds to step S11 and the reducing agent injection valve 34 is started. It is determined that there is leakage of the reducing agent from

  If it is determined that there is a leakage of the reducing agent, in step S12, the operation of the reducing agent injection device 30 is stopped and the warning means is operated to notify the driver and the like, and then the diagnosis flow is finished. To do.

  As described above, according to the reducing agent injection valve leakage diagnosis apparatus of the present embodiment, the comparison is made on the downstream side of the reducing catalyst 20 even though the reducing agent injection amount from the reducing agent injection valve 34 is small. When the state is such that a high concentration of ammonia is detected, it is determined that the reducing agent has leaked from the reducing agent injection valve 34. Therefore, ammonia is prevented from being released into the atmosphere until the reducing agent injection valve 34 is replaced, for example, by stopping the operation of the reducing agent injection device 30.

5: Internal combustion engine, 10: Exhaust gas purification device, 11: Exhaust pipe, 14: Sensor, 20: Reduction catalyst, 30: Reducing agent injection device, 31: Storage tank, 34: Reducing agent injection valve, 41: Pump, 43: Pressure sensor, 57: first reducing agent supply passage, 58: second reducing agent supply passage, 59: circulation passage, 60: control device (reducing agent injection valve leakage diagnosis device), 61: pump drive control means, 62: Ammonia concentration detection means, 63: Instruction injection amount calculation means, 64: Reducing agent injection valve control means, 65: Leak determination means

Claims (6)

A reduction catalyst comprising: a reduction catalyst that purifies NO _{x in} exhaust gas using ammonia; and a reducing agent injection valve that injects a reducing agent capable of generating ammonia into an exhaust passage upstream of the reduction catalyst. In the reducing agent injection valve leakage diagnosis device for diagnosing the presence or absence of leakage of the reducing agent from the reducing agent injection valve in the agent injection device,
Reducing agent injection valve control means for controlling opening and closing of the reducing agent injection valve based on an instruction injection amount of the reducing agent;
Ammonia concentration detection means for detecting the ammonia concentration in the exhaust gas on the downstream side based on a sensor signal of a sensor provided on the downstream side of the reduction catalyst;
Leak determination means for determining the presence or absence of leakage of the reducing agent from the reducing agent injection valve based on the information on the instructed injection amount of the reducing agent and the ammonia concentration;
A leakage diagnosis apparatus for a reducing agent injection valve, comprising: The reducing agent injection valve control means is configured to correct the amount of injection of the reducing agent by the reducing agent injection valve so that the ammonia concentration is suppressed within an allowable range,
The leakage determination means determines that there is leakage of the reducing agent when the ammonia concentration is equal to or higher than a predetermined concentration and a correction coefficient used for correcting the injection amount is less than a predetermined value. The leakage diagnosis apparatus for a reducing agent injection valve according to claim 1.   The leakage determination means detects the leakage of the reducing agent when the ammonia concentration is equal to or higher than a predetermined concentration and the indicated injection amount of the reducing agent or the correction coefficient is less than a predetermined value for a predetermined time or longer. The leakage diagnosis device for a reducing agent injection valve according to claim 1 or 2, wherein the leakage diagnosis device for a reducing agent injection valve according to claim 1 or 2 is determined.   4. The reducing agent injection valve according to claim 1, wherein when the leakage determining unit determines that the reducing agent leaks, the operation of the reducing agent injection device is stopped. 5. Leakage diagnostic device. A reduction catalyst comprising: a reduction catalyst that purifies NO _{x in} exhaust gas using ammonia; and a reducing agent injection valve that injects a reducing agent capable of generating ammonia into an exhaust passage upstream of the reduction catalyst. In the reducing agent injection valve leakage diagnosis method for diagnosing the presence or absence of leakage of the reducing agent from the reducing agent injection valve in the agent injection device,
The instruction injection amount of the reducing agent is read, the ammonia concentration in the exhaust gas downstream from the reduction catalyst is detected, and from the reducing agent injection valve based on the information on the instruction injection amount of the reducing agent and the ammonia concentration. A method for diagnosing leakage of a reducing agent injection valve, wherein the presence or absence of leakage of the reducing agent is determined.   An exhaust emission control device for an internal combustion engine, comprising the leakage diagnosis device for a reducing agent injection valve according to any one of claims 1 to 4.

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