JP5071341B2 - Engine exhaust purification system - Google Patents

Description

  The present invention belongs to a technical field related to an engine exhaust purification device that reduces and removes NOx contained in exhaust gas by injecting a liquid NOx reducing agent into the exhaust gas of the engine.

  Generally, in this type of engine exhaust purification device, urea water is used as a NOx reducing agent injected into the exhaust gas, and ammonia generated by hydrolysis of the urea water by exhaust heat is converted to NOx on the selective reduction catalyst. NOx is reduced and removed by the reduction reaction. The urea water is normally stored in a urea water tank, and is supplied to an injection actuator such as an injection nozzle or an injection valve by a supply pump provided in the tank.

  For example, in the exhaust gas purification device disclosed in Patent Document 1, an injection nozzle is employed as an injection actuator, and the amount of urea water injected from the injection nozzle is controlled to an appropriate amount according to the amount of NOx in the exhaust gas. The driving pressure of the supply pump and the injection air pressure are controlled. In this exhaust purification device, when an abnormality occurs in the urea water injection system including the pump, the air assist device, etc., the urea water injection is stopped to prevent wasteful consumption of the urea water. Yes.

  Moreover, in the exhaust gas purification apparatus shown in Patent Document 2, an electromagnetic injection valve is employed as an injection actuator. In this exhaust purification apparatus, a cooling chamber for circulating a cooling medium is provided around the injection valve in order to improve the heat resistance of the injection valve, which is inferior to that of the injection nozzle.

In addition to the above-described exhaust purification device for removing NOx in the exhaust, an exhaust purification device that removes exhaust particulates contained in the exhaust of a diesel engine or the like is also known. In order to collect exhaust particulates in the exhaust by a filter disposed in the exhaust passage of the engine, and to prevent clogging of the filter when the collected exhaust particulates exceed a threshold amount, The filter is regenerated by removing the filter. Specifically, in this exhaust emission control device, unburned fuel is additionally injected into a cylinder that is in the expansion stroke during filter regeneration, whereby the unburned fuel is supplied to an oxidation catalyst disposed upstream of the filter and oxidized. By reacting and raising the filter temperature to the ignition temperature of the exhaust particulate by this reaction heat, the exhaust particulate is burned and removed.
JP-A-2005-113708 JP 2007-321647 A JP 2006-214311 A

  By the way, in order to improve the NOx removal performance in the exhaust of the engine, the injection capable of controlling the injection amount of urea water (NOx reducing agent) with higher accuracy than the injection nozzle method (the method shown in Patent Document 1). It is preferable to employ a valve method (the method shown in Patent Document 2 above). If the exhaust particulate removal technology shown in Patent Document 3 is applied to the NOx purification device that employs this injection valve system, exhaust particulate can be removed in addition to NOx in the exhaust. Performance can be improved.

  However, in this case, the following heat damage problem of the injection valve (reducing agent injection valve) occurs. That is, the urea water supplied to the injection valve has an action of cooling the injection valve and protecting it from the exhaust heat, but an abnormality occurs in the supply pump that supplies the urea water to the injection valve, or the urea water tank If the urea water in the inside is insufficient or the urea water is not sufficiently supplied to the injection valve, the injection valve will be exposed to a thermally severe condition. When filter regeneration is executed in this state, the exhaust temperature rises as the filter temperature rises, resulting in a problem that the temperature of the injection valve exceeds its heat resistance limit.

  In order to solve this problem, it is conceivable to provide a cooling chamber around the injection valve as shown in Patent Document 2 above, but in this case, components for forming the cooling chamber and refrigerant are supplied to the cooling chamber. Therefore, there is a problem in that a refrigerant supply device for this is separately required, resulting in a complicated device configuration and an increase in cost.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a filter for collecting exhaust particulates, filter regeneration means for raising the temperature of the filter and regenerating the exhaust, exhaust gas In an exhaust emission control device for an engine, comprising a reducing agent injection valve that injects a liquid NOx reducing agent into exhaust gas to remove NOx therein, and a reducing agent supply device that supplies the NOx reducing agent to the injection valve. This is to reliably protect the reducing agent injection valve from exhaust heat when the NOx reducing agent having a cooling action is not sufficiently supplied to the agent injection valve, particularly during filter regeneration by the filter regeneration means. This is to reliably prevent the temperature of the reducing agent injection valve from exceeding the heat resistance temperature due to the rise in the exhaust gas temperature.

  In order to achieve the above object, according to the present invention, in the case where the NOx reducing agent is not sufficiently supplied to the reducing agent injection valve due to the abnormality of the reducing agent supply device or the lack of urea water, the filter by the filter regeneration means is used. Even if regeneration is not executed or filter regeneration is executed, the subsequent rise in exhaust temperature is suppressed as much as possible.

  Specifically, in the first aspect of the invention, a reducing agent injection valve that is provided in the exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust, and the NOx reducing agent is supplied to the reducing agent injection valve. A reducing agent supply device, a filter disposed upstream of the reducing agent injection valve and collecting exhaust particulates contained in the exhaust, and an amount of exhaust particulates collected in the filter is a predetermined threshold. And a filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature and removing the exhaust particulates by combustion when the amount exceeds the target. .

  And an abnormality detecting means for detecting an abnormality of the reducing agent supply device, and when an abnormality of the reducing agent supply device is detected by the abnormality detecting means, the NOx reducing agent is introduced into the exhaust gas by the reducing agent injection valve. When the abnormality of the reducing agent supply device is detected by the injection prohibiting means for prohibiting the injection and the abnormality detecting means, the target filter at the time of the filter regeneration by the filter regeneration means is compared with the case where the abnormality is not detected. It further includes target filter temperature changing means for lowering the temperature.

According to this configuration, when an abnormality of the reducing agent supply device is detected by the abnormality detection means,
The injection prohibiting means prohibits the injection of the NOx reducing agent into the exhaust gas by the reducing agent injection valve, the target filter temperature setting means changes the target filter temperature setting, and the abnormality detecting means detects the abnormality of the reducing agent supply device. The target filter temperature is set lower than when no is detected.

  Therefore, in a situation where the supply of the NOx reducing agent having a cooling action to the reducing agent injection valve is insufficient due to an abnormality occurring in the reducing agent supply device (that is, the situation where the cooling of the reducing agent injection valve is insufficient), the reducing agent. The filter temperature at the time of filter regeneration can be lowered as compared with the case where no abnormality has occurred in the supply device, and the exhaust temperature rise due to the temperature rise of the filter can be suppressed as much as possible. Therefore, it is possible to reliably protect the reducing agent injection valve from exhaust heat in a situation where the reducing agent injection valve is not sufficiently cooled by the reducing agent (that is, to ensure that the temperature of the reducing agent injection valve exceeds its heat resistance temperature). Can be prevented).

  In addition, when an abnormality occurs in the reducing agent supply device, the injection of the reducing agent by the injection valve is prohibited, so that the abnormal operation of the reducing agent injection valve and the leakage of the reducing agent from the injection port are ensured. Can be prevented.

  According to a second aspect of the present invention, a reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust, and a reducing agent supply device that supplies the NOx reducing agent to the reducing agent injection valve, The exhaust gas is disposed upstream of the reducing agent injection valve and collects exhaust particulates contained in the exhaust, and the amount of exhaust particulates collected in the filter exceeds a predetermined threshold amount. An engine exhaust purification device including a filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature and removing the exhaust particulates by combustion.

  And an abnormality detecting means for detecting an abnormality of the reducing agent supply device, and when an abnormality of the reducing agent supply device is detected by the abnormality detecting means, the NOx reducing agent is introduced into the exhaust gas by the reducing agent injection valve. An injection prohibiting unit that prohibits injection, and a predetermined threshold amount changing unit that lowers the predetermined threshold amount when an abnormality of the reducing agent supply device is detected by the abnormality detecting unit as compared with a case where the abnormality is not detected. And are further provided.

According to this configuration, when an abnormality of the reducing agent supply device is detected by the abnormality detection means,
The injection prohibiting means prohibits the injection of the NOx reducing agent into the exhaust gas by the reducing agent injection valve, the threshold amount setting is changed by the predetermined threshold amount changing means, and the abnormality detecting means detects an abnormality of the reducing agent supply device. The predetermined threshold amount is set lower than in the case where no detection is made.

  Therefore, in a situation where the supply of the NOx reducing agent having a cooling action to the reducing agent injection valve is insufficient due to an abnormality occurring in the reducing agent supply device, the filter is less than when no abnormality occurs in the reducing agent supply device. The amount of exhaust particulates (predetermined threshold amount) burned and removed during regeneration can be reduced, and the rise in exhaust temperature can be suppressed as much as possible. Therefore, the reducing agent injection valve can be reliably protected from the exhaust heat in a situation where the cooling of the reducing agent injection valve by the reducing agent is insufficient. In addition, since the injection of the reducing agent by the reducing agent injection valve is also prohibited, it is possible to prevent abnormal operation of the reducing agent injection valve and leakage of the reducing agent. Thus, the same effect as that attained by the 1st aspect can be attained.

  According to a third aspect of the present invention, a reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust, and a reducing agent supply device that supplies the NOx reducing agent to the reducing agent injection valve; The exhaust gas is disposed upstream of the reducing agent injection valve and collects exhaust particulates contained in the exhaust, and the amount of exhaust particulates collected in the filter exceeds a predetermined threshold amount. An engine exhaust purification device including a filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature and removing the exhaust particulates by combustion.

  And an abnormality detecting means for detecting an abnormality of the reducing agent supply device, and when an abnormality of the reducing agent supply device is detected by the abnormality detecting means, the NOx reducing agent is introduced into the exhaust gas by the reducing agent injection valve. Injection prohibiting means for prohibiting injection, and filter regeneration prohibiting means for prohibiting regeneration of the filter by the filter regeneration means when an abnormality of the reducing agent supply device is detected by the abnormality detecting means. It shall be.

According to this configuration, when an abnormality of the reducing agent supply device is detected by the abnormality detection means,
The injection prohibiting means prohibits the injection of the NOx reducing agent into the exhaust gas by the reducing agent injection valve, and the filter regeneration prohibiting means prohibits the filter regeneration by the filter regeneration means.

  Therefore, in the situation where the supply of the NOx reducing agent having a cooling action to the reducing agent injection valve is insufficient due to an abnormality in the reducing agent supply device, the filter regeneration that causes the exhaust temperature to rise is not executed. . In addition, since the injection of the reducing agent by the reducing agent injection valve is also prohibited, it is possible to prevent abnormal operation of the reducing agent injection valve and leakage of the reducing agent. Therefore, the same effect as that of the invention of claim 1 can be obtained.

  According to a fourth aspect of the present invention, there is provided a reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust, and a tank that stores the NOx reducing agent. A reducing agent supply device for supplying NOx reducing agent to the reducing agent injection valve; a filter disposed upstream of the reducing agent injection valve for collecting exhaust particulates contained in the exhaust; and the filter Filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature when the amount of exhaust particulate collected in the exhaust gas exceeds a predetermined threshold amount and removing the exhaust particulate by combustion; An exhaust emission control device for an engine equipped with

  A remaining amount detecting means for detecting a state in which the remaining amount of the NOx reducing agent in the tank is below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve; A target filter temperature changing means for lowering the target filter temperature when the state in which the remaining amount of the NOx reducing agent is below the predetermined level is detected by the remaining amount detecting unit as compared with a case in which the state is not detected; Are further provided.

  According to this configuration, the remaining amount detection means detects that the remaining amount of the NOx reducing agent in the tank is below a predetermined level at which the NOx reducing agent can be supplied to the reducing agent injection valve by the reducing agent supply device. In this case, the target filter temperature setting is changed by the target filter temperature changing means, and the target filter temperature is set lower than when the remaining amount detecting means does not detect that the remaining amount of the reducing agent is below the predetermined level. The

  Therefore, in a situation where the remaining amount of NOx reducing agent in the tank is insufficient and therefore the reducing agent cannot be sufficiently supplied to the reducing agent injection valve (that is, in a situation where cooling of the reducing agent injection valve by the reducing agent is insufficient). Can suppress as much as possible an increase in exhaust gas temperature due to an increase in filter temperature during filter regeneration. Therefore, the same effect as that of the invention of claim 1 can be obtained.

  According to a fifth aspect of the present invention, there is provided a reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust, and a tank that stores the NOx reducing agent. A reducing agent supply device for supplying NOx reducing agent to the reducing agent injection valve; a filter disposed upstream of the reducing agent injection valve for collecting exhaust particulates contained in the exhaust; and the filter Filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature when the amount of exhaust particulate collected in the exhaust gas exceeds a predetermined threshold amount and removing the exhaust particulate by combustion; An exhaust emission control device for an engine equipped with

  A remaining amount detecting means for detecting a state in which the remaining amount of the NOx reducing agent in the tank is below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve; A predetermined threshold amount changing means for lowering the predetermined threshold amount as compared with a case where the remaining amount of the NOx reducing agent is detected to be lower than the predetermined level by the remaining amount detecting means as compared with a case where the state is not detected; Are further provided.

  According to this configuration, the remaining amount detection means detects that the remaining amount of the NOx reducing agent in the tank is below a predetermined level at which the NOx reducing agent can be supplied to the reducing agent injection valve by the reducing agent supply device. In this case, the predetermined threshold amount is changed by the predetermined threshold amount changing means, and the predetermined threshold amount is set lower than when the remaining amount detecting means does not detect that the remaining amount of the reducing agent is below the predetermined level. The

  Therefore, in the situation where the amount of NOx reducing agent remaining in the tank is insufficient and the reducing agent injection valve is not sufficiently cooled by the reducing agent, the amount of exhaust particulates burned and removed during filter regeneration is reduced to reduce the exhaust temperature. Can be suppressed as much as possible. Therefore, the same effect as that of the invention of claim 1 can be obtained.

  In the invention of claim 6, it has a reducing agent injection valve that is provided in the exhaust passage of the engine and injects the liquid NOx reducing agent into the exhaust, and a tank that stores the NOx reducing agent. A reducing agent supply device for supplying NOx reducing agent to the reducing agent injection valve; a filter disposed upstream of the reducing agent injection valve for collecting exhaust particulates contained in the exhaust; and the filter Filter regeneration means for regenerating the filter by raising the temperature of the filter to a target filter temperature when the amount of exhaust particulate collected in the exhaust gas exceeds a predetermined threshold amount and removing the exhaust particulate by combustion; An exhaust emission control device for an engine equipped with

  A remaining amount detecting means for detecting a state in which the remaining amount of the NOx reducing agent in the tank is below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve; And a filter regeneration prohibiting means for prohibiting filter regeneration by the filter regeneration means when the remaining amount detecting means detects that the remaining amount of the NOx reducing agent is below the predetermined level. And

  According to this configuration, the remaining amount detecting means detects that the remaining amount of the NOx reducing agent in the tank is not at a level at which the NOx reducing agent can be supplied to the reducing agent injection valve by the reducing agent supply device. In such a case, the filter regeneration by the filter regeneration means is prohibited by the filter regeneration prohibiting means.

  Therefore, in a situation where the remaining amount of NOx reducing agent in the tank is insufficient and cooling of the reducing agent injection valve by the reducing agent is insufficient, filter regeneration that causes the exhaust temperature to rise is not executed. . Therefore, the same effect as that of the invention of claim 1 can be obtained.

  According to a seventh aspect of the invention, in the invention according to any one of the fourth to sixth aspects, when the remaining amount detecting means detects that the remaining amount of the NOx reducing agent is lower than the predetermined level, It is assumed that there is further provided an injection prohibiting means for prohibiting the injection of the NOx reducing agent into the exhaust gas by the reducing agent injection valve.

  According to this configuration, when the remaining amount of the NOx reducing agent in the tank is insufficient, the injection inhibiting means prohibits the injection of the NOx reducing agent into the exhaust by the reducing agent injection valve. Therefore, for example, the reducing agent remaining in the supply pipe connected to the reducing agent injection valve can be reliably prevented from leaking from the injection port of the injection valve.

  As described above, according to the engine exhaust gas purification apparatus of the present invention, when the reducing agent supply device is not sufficiently supplied with NOx reducing agent due to an abnormality of the reducing agent supply device or a shortage of remaining urea water. The regenerator injection valve can be reliably protected from the exhaust heat by suppressing the filter regeneration by the filter regeneration means or suppressing the subsequent increase in the exhaust temperature as much as possible even if the filter regeneration is performed. It becomes possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an engine exhaust purification device 1 according to an embodiment of the present invention. In the present embodiment, the exhaust purification device 1 is applied to exhaust purification processing of a diesel engine (not shown).
This engine is an in-line four-cylinder engine, and reference numeral 2 is an exhaust passage that guides fuel gas (exhaust gas) discharged from each cylinder of the engine to the atmosphere. An upstream end portion of the exhaust passage 2 is It is branched into a plurality and communicates with the combustion chamber of each cylinder via an exhaust port.

  The exhaust purification device 1 is included in the exhaust, and an oxidation catalyst unit 3 that oxidizes and purifies harmful substances such as HC and CO contained in the combustion gas (exhaust gas) discharged from each cylinder (combustion chamber) of the engine. A filter 4 that collects exhaust particulates such as soot, a NOx catalyst part 5 (SCR: Selective Catalytic Reduction) that reduces and purifies NOx in the exhaust, and an ECU 6 that controls the operation of the engine and the exhaust purification device 1 The oxidation catalyst part 3, the filter 4, and the NOx catalyst part 5 are arranged in order from the upstream side to the downstream side of the exhaust passage 2.

The oxidation catalyst part 3 has an oxidation catalyst 3a in which a noble metal such as Pt (platinum) is supported on a cell surface of a porous ceramic honeycomb carrier and a catalyst layer is coated. It promotes an oxidation reaction that generates CO ₂ and H ₂ O by oxidation.

  The filter 4 is a porous ceramic diesel particulate filter, and the cell surface is coated with a catalyst layer supporting a noble metal such as Pt. The heat of reaction of the catalytic metal is used to improve the temperature rise performance during filter regeneration, which will be described later.

  The upstream side and the downstream side of the filter 4 in the exhaust passage 2 communicate with each other via a differential pressure detection channel 7, and the differential pressure detection channel 7 has a differential pressure ΔP between the upstream side and the downstream side of the filter. A differential pressure detection sensor 8 is provided to detect the above. The filter 4 is provided with a filter temperature detection sensor 9 for detecting the filter temperature Tf, and detection signals from the sensors 8 and 9 are output to the ECU 6 via an electric connection line (not shown). The ECU 6 calculates the amount of exhaust particulates collected (deposited) on the filter 4 based on the differential pressure ΔP detected by the differential pressure detection sensor 8. Here, the ECU 6 calculates the exhaust particulate amount on the assumption that the detected differential pressure ΔP is proportional to the exhaust particulate amount (assuming that the larger the differential pressure ΔP, the larger the exhaust particulate amount). When the calculated exhaust particulate amount exceeds a predetermined threshold amount, the ECU 6 executes filter regeneration control (to be described later) to burn the exhaust particulate. In the present embodiment, the differential pressure detection flow path 7 is provided in order to detect the differential pressure ΔP between the upstream side and the downstream side of the filter 4, but the present invention is not limited to this. 4, pressure sensors may be provided on the upstream side and the downstream side, respectively, and the difference value between the detected pressures of the two pressure sensors may be calculated as the differential pressure ΔP.

  The NOx catalyst unit 5 has a selective reduction type NO catalyst 5a, and the selective reduction type NO catalyst 5a is made of a base material surface such as zeolite or alumina carrying a noble metal such as Pt.

A reducing agent injection valve 15 for supplying urea water as a NOx reducing agent to the NOx catalyst 5a is provided on the upstream side of the NOx catalyst unit 5. The reducing agent injection valve 15 is composed of a high performance electromagnetic valve whose operation is controlled by the ECU 6, and is arranged with its injection port facing the exhaust passage 2. When urea water (urea aqueous solution) is injected from the reducing agent injection valve 15, the injected urea water is hydrolyzed by exhaust heat to generate ammonia. The generated ammonia is adsorbed by the NOx catalyst 5a and promotes a reduction reaction (denitration reaction) with NOx, thereby decomposing NOx into H ₂ O and harmless nitrogen N ₂ . This reaction is represented by the following chemical formulas (1) to (3).

(NH ₂ ) ₂ CO + H ₂ O → 2NH ₃ + CO (1)
4NH ₃ + 4NO + O ₂ → 4N ₂ + 6H ₂ O (2)
4NH ₃ + 2NO ₂ + O ₂ → 3N ₂ + 6H ₂ O (3)
An ammonia purification catalyst (not shown) is provided on the downstream side of the NOx catalyst unit 5, and this ammonia purification catalyst stimulates the slip ammonia that has passed through the NOx catalyst without reacting with the NOx. It prevents odorous ammonia from being released into the atmosphere without purification.

  The NOx catalyst unit 5 is provided with a NOx catalyst temperature sensor 11 for detecting the temperature Ts of the NOx catalyst 5a. The NOx catalyst unit 5 is supplied to the NOx catalyst unit 5 on the upstream side and the downstream side, respectively. An upstream NOx sensor 12 for detecting the NOx concentration Dn1 in the exhaust gas to be detected and a downstream NOx sensor 13 for detecting the NOx concentration Dn2 in the exhaust gas after passing through the NOx catalyst unit 5 are provided. The detection signals of 13 to 13 are output to the ECU 6 through an electric connection line (not shown), and the ECU 6 operates the reducing agent injection valve 15 based on the detection signals from the sensors 11 to 13 as will be described later. To control.

  The reducing agent injection valve 15 is connected to a reducing agent supply device 20 for supplying urea water to the injection valve 15. The reducing agent supply device 20 is provided in the urea water tank 21 that stores urea water, the supply pipe 22 that extends from the urea water tank 21 to the reducing agent injection valve 15, and the supply pipe 22. And a supply pump 23 that sucks the stored urea water and supplies the urea water to the reducing agent injection valve 15. In FIG. 1, reference numeral 26 denotes a filtration filter disposed on the upstream side of the supply pump 23.

  A pressure control valve 24 is provided on the downstream side of the supply pump 23, and the pressure control valve 24 is configured so that the urea water pressure Pr supplied from the pump 23 to the reducing agent injection valve 15 does not exceed a predetermined value. The surplus urea water is returned to the urea water tank 21 through the return pipe 25.

  Between the pressure control valve 24 and the reducing agent injection valve 15 in the supply pipe 22, a pressure sensor 10 for detecting the supply pressure Pr of urea water supplied to the injection valve 15 is provided. In the urea water tank 21, the remaining amount for detecting that the remaining amount of urea water Mr is below a predetermined amount (the lower limit value of the remaining amount of urea water that can be supplied to the reducing agent injection valve 15 by the supply pump 23). A sensor 14 is provided. As the remaining amount sensor 14, for example, a float type sensor or a thermistor can be used. Detection signals from the sensors 10 and 14 are output to the ECU 6 via an electric connection line (not shown). As will be described in detail later, the ECU 6 performs a urea water supply shortage state (urea water) in which the amount of urea water supplied to the reducing agent injection valve 15 is insufficient based on the detection information from the pressure sensor 10 and the remaining amount sensor 14. And the exhaust temperature suppression control described later to prevent the temperature of the injection valve 15 from exceeding its heat resistant temperature. Execute.

  The ECU 6 is composed of a well-known microcomputer comprising a CPU, ROM, RAM, and the like. Based on detection signals from the sensors 8 to 14 and various sensors (not shown) attached to the engine, the ECU 6 The operation of the agent injection valve 15 and the supply pump 23 is controlled.

  Engine operation control in the ECU 6 is performed by controlling the operation of an injector (fuel injection valve) (not shown) that injects fuel into each cylinder (fuel chamber) of the engine and an intake throttle valve provided in the intake passage. . The fuel injection control using the injector by the ECU 6 follows the main injection control for injecting fuel near the compression top dead center of each cylinder in order to generate engine output and the main injection control for filter regeneration. Additional injection control for injecting fuel in the expansion stroke of each cylinder.

  When the ECU 6 performs additional injection control, that is, filter regeneration control, filter regeneration is performed as follows. That is, the fuel injected into the combustion chamber of each cylinder by the execution of the additional injection control is supplied to the oxidation catalyst unit 3 through the exhaust passage 2 in an unburned state. The unburned HC in the fuel is oxidized on the oxidation catalyst 3a, and the temperature of the exhaust gas flowing through the exhaust passage 2 is raised by the reaction heat during the oxidation. Thus, the heated exhaust gas flows into the filter 4 and heats the filter 4. As a result, the temperature of the exhaust particulates collected by the filter 4 rises and reaches the ignition temperature, so that the exhaust particulates burn and the filter 4 is regenerated.

  The ECU 6 controls the filter temperature Tf to a preset target filter temperature so that the exhaust particulates reliably reach the ignition temperature during filter regeneration. Specifically, the ECU 6 controls the fuel injection amount (additional injection amount) of the injector and the fuel injection timing at the time of executing the additional injection control based on the temperature detected by the filter temperature detection sensor 9, thereby the filter temperature Tf. To the target filter temperature.

  Further, when the ECU 6 determines whether or not the detected pressure of the pressure sensor 10 (that is, the supply pressure Pr to the reducing agent injection valve 15 of urea water) is equal to or lower than a predetermined pressure, In this case, the exhaust gas temperature suppression control is executed on the assumption that the reducing agent supply device 20 is in an abnormal state and the urea water supply is insufficient. More specifically, when it is determined that an abnormality has occurred in the reducing agent supply device 20, the ECU 6 determines that no abnormality has occurred (when the detected pressure of the pressure sensor 10 exceeds a predetermined pressure). In comparison, the target filter temperature during filter regeneration is set low. When the ECU 6 determines that an abnormality has occurred in the reducing agent supply device 20, the ECU 6 prohibits the operation of the reducing agent injection valve 15 and the supply pump 23. Here, the abnormality of the reducing agent supply device 20 may be a failure of the supply pump 23 or the pressure control valve 24, a connection failure of the supply pipe 22, a clogging of the supply pipe 22, and the like.

  Further, even when the ECU 6 determines that the urea water supply pressure Pr exceeds the predetermined pressure, that is, when it is determined that there is no abnormality in the reducing agent supply device 20, the urea water tank is detected by the remaining amount sensor 14. When it is detected that the urea water remaining amount Mr in the fuel tank 21 is less than the predetermined amount, it is assumed that the urea water supply is insufficient due to the urea water shortage in the tank 21, and the exhaust temperature suppression control described above is executed. At the same time, the operation of the reducing agent injection valve 15 and the supply pump 23 is prohibited.

  Next, exhaust temperature suppression control and reducing agent injection valve control in the ECU 6 will be described based on the flowchart of FIG.

  In the first step SA1, the detection signals from the sensors 8 to 14 are read, the supply pressure Pr of the urea water supplied to the reducing agent injection valve 15, the urea water remaining amount Mr in the urea water tank 21, the NOx catalyst. Information on the temperature Ts, the upstream NOx concentration Dn1, and the downstream NOx concentration Dn2 is acquired.

  In step SA2, it is determined whether the urea water supply pressure Pr calculated in step SA1 is equal to or lower than a predetermined pressure. If this determination is YES, the process proceeds to step SA7, and if NO, the process proceeds to step SA3.

  In step SA3, it is determined by the remaining amount sensor 14 whether or not the urea water remaining amount Mr in the urea water tank 21 is detected to be less than a predetermined amount. If this determination is YES, the process proceeds to step SA7. If NO, the process proceeds to step SA4.

  In step SA4, the target injection amount Q of the urea water by the reducing agent injection valve 15 is calculated based on the NOx catalyst temperature Ts, the upstream NOx concentration Dn1, and the downstream NOx concentration Dn2 calculated in step SA1. Here, if the amount of urea water injected by the reducing agent injection valve 15 is too large, ammonia produced by hydrolysis of the urea water is not completely purified by the ammonia purification catalyst but is released into the atmosphere, while the urea water is If the injection amount is too small, NOx in the exhaust cannot be completely reduced and removed. For this reason, the target injection amount Q of urea water is calculated as an injection amount that can sufficiently remove NOx in the exhaust gas and that does not cause an excessive amount of ammonia to be generated during hydrolysis.

  In step SA5, a necessary control signal is output to the reducing agent injection valve 15 so that the injection amount of urea water from the reducing agent injection valve 15 becomes the target injection amount Q calculated in step SA4.

  In Step SA6, the set value of the target filter temperature at the time of filter regeneration is set to the first set temperature U (for example, 650 ° C.), and then the process returns.

  In step SA7 that proceeds when the determination in step SA2 or SA3 is YES, output of the drive signal to the injection valve 15 is stopped in order to stop (prohibit) the operation of the reducing agent injection valve 15.

  In step SA8, the set value of the target filter temperature at the time of filter regeneration is set to the second set temperature V (<U) lower than the first set temperature U, and then the process returns.

  As described above, in the first embodiment, the ECU 6 determines whether or not the urea water supply is insufficient based on the detection information from the pressure sensor 10 and the remaining amount sensor 14 (in steps SA2 and SA3). When it is determined that the current state is determined (when the determination at step SA2 or SA3 is YES), when it is determined that the current state is not present (when both the determinations at steps SA2 and SA3 are NO) ), The target filter temperature at the time of filter regeneration is set lower (the process of step SA8 is executed).

  According to this, when the filter regeneration control is executed by the ECU 6 in a situation where the reducing agent injection valve 15 cannot be sufficiently cooled by the urea water because the urea water supply is insufficient, the filter temperature is reduced. Tf only rises to a second set temperature V lower than the first set temperature U, and the filter temperature Tf at the time of filter regeneration is higher than when the reducing agent injection valve 15 is sufficiently supplied with urea water. The temperature can be lowered, and an increase in the exhaust temperature can be suppressed. Therefore, it is possible to reliably prevent the reducing agent injection valve 15 from being heated by the exhaust heat and the injection valve temperature from exceeding the heat resistance temperature.

  Further, when the ECU 6 determines that the urea water supply is insufficient (when the determination at step SA2 or SA3 is YES), the ECU 6 stops the operation of the reducing agent injection valve 15 (executes the process at step SA7). It is configured as follows.

  As a result, it is possible to reliably prevent the urea water from leaking from the injection port of the reducing agent injection valve 15, and to suppress the generation of drive heat of the reducing agent injection valve 15, so that the temperature of the injection valve 15 is reduced. It is possible to more reliably prevent the heat resistant temperature from being exceeded.

(Embodiment 2)
FIG. 3 shows a second embodiment of the present invention, in which the exhaust gas temperature suppression control in the ECU 6 is different from that in the first embodiment. That is, in the present embodiment, the exhaust gas temperature suppression control in the ECU 6 is performed by changing the exhaust particulate accumulation amount (that is, the predetermined threshold amount) of the filter 4 that is a threshold value when starting filter regeneration. The hardware configuration of the filter 4, the catalyst units 3 and 5, the reducing agent supply device 20, and the like is assumed to be the same as that of the first embodiment in the following embodiments.

  Exhaust temperature suppression control and reducing agent injection valve control in the ECU 6 according to Embodiment 3 of the present invention will be described based on the flowchart of FIG.

  In steps SB1 to SB5, processing similar to that in steps SA1 to SA5 in the first embodiment is performed.

  In step SB6, the process returns with the predetermined threshold amount set as the first set amount X.

  In step SB7, processing similar to that in step SA7 in the first embodiment is performed.

  In step SB8, the process returns with the predetermined threshold amount set as a second set amount Y (<X) smaller than the first set threshold amount X.

  As described above, in the second embodiment, the ECU 6 determines whether or not the urea water supply is insufficient based on the detection information from the pressure sensor 10 and the remaining amount sensor 14 (steps SB2 and SB3). When it is determined that the current state is determined (when the determination is made in step SB2 or SB3 is YES), when it is determined that the current state is not present (when both the determinations in steps SB2 and SB3 are NO) ), The predetermined threshold amount is set low (the process of step SB8 is executed).

  According to this, in a situation where the reducing agent injection valve 15 cannot be sufficiently cooled by the urea water because the urea water supply is insufficient, the amount of accumulated exhaust particulate on the filter 4 is reduced to the first set amount X. When the second set amount Y is reached, the filter regeneration control by the ECU 6 is executed. For this reason, compared with the case where urea water is sufficiently supplied to the reducing agent injection valve 15, it is possible to reduce the amount of exhaust particulates to be combusted at the time of filter regeneration and to reduce the combustion amount per unit time. An increase in temperature can be reliably suppressed. In this way, the same effects as those of the first embodiment can be obtained.

(Embodiment 3)
FIG. 4 shows a third embodiment of the present invention, in which the exhaust gas temperature suppression control in the ECU 6 is different from those in the first and second embodiments. That is, in this embodiment, the exhaust gas temperature suppression control in the ECU 6 is performed by prohibiting filter regeneration by the filter regeneration means.

  Exhaust temperature suppression control and reducing agent injection valve control in the ECU 6 according to Embodiment 3 of the present invention will be described based on the flowchart of FIG.

  In steps SC1 to SC5, processing similar to that in steps SA1 to SA5 in the first embodiment is performed.

  In step SC6, the filter regeneration prohibition flag is set to zero.

  In step SC7, the same process as step SA7 in the first embodiment is performed.

  In step SC8, the filter regeneration prohibition flag is set to 1.

  As described above, in the third embodiment, the ECU 6 determines whether or not the urea water supply is insufficient based on the detection information from the pressure sensor 10 and the remaining amount sensor 14 (in steps SC2 and SC3). When it is determined that the current state is present (when the determination at step SC2 or SC3 is YES), the filter regeneration prohibition flag is set to 1 (the process at step SC8 is performed), and then the filter is filtered. Even if the regeneration condition is satisfied (even if the amount of exhaust particulate collected by the filter 4 exceeds a predetermined threshold amount), the execution of the filter regeneration control is prohibited, but it is determined that the state is not in this state (step SC2). And the determination of SC3 are both NO), the filter regeneration prohibition flag is set to 0 (by executing the process of step SC6), and then the filter If the raw condition is satisfied is configured to allow execution of the filter regeneration control.

  According to this, in a situation where the reducing agent injection valve 15 cannot be sufficiently cooled by the urea water because the urea water supply is insufficient, the filter regeneration control that is the cause of the exhaust temperature increase is executed. It is possible to suppress the rise in the exhaust temperature as much as possible. Therefore, it is possible to obtain the same effect as that of the first embodiment.

(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in each said embodiment, although the example which applied the exhaust gas purification apparatus 1 to the diesel engine was shown, you may make it apply to a spark ignition type gasoline engine, for example, without restricting to this.

  In each of the above embodiments, the temperature of the filter 4 during the filter regeneration is increased by additional fuel injection in the expansion stroke of each cylinder of the engine. However, the present invention is not limited to this. For example, the filter 4 An electric heater may be provided in the vicinity of and the filter 4 may be heated by the electric heater.

  In each of the above embodiments, the oxidation catalyst 3a is provided on the upstream side separately from the filter 4. However, the present invention is not limited to this. For example, the filter 4 has an oxidation catalyst function without providing the oxidation catalyst 3a. You may make it let. Moreover, you may make it provide the oxidation catalyst 3a and the filter 4 which has an oxidation catalyst function.

  Further, the exhaust gas temperature suppression control in the first and second embodiments may be combined. Specifically, when the ECU 6 determines that the urea water supply is insufficient, the target filter temperature and the predetermined threshold amount are both set lower than when it is determined that the urea water supply is not in this state. That's fine. By doing so, the same effects as those of the first embodiment can be obtained more reliably.

  INDUSTRIAL APPLICABILITY The present invention is useful for an engine exhaust gas purification device that reduces and removes NOx contained in exhaust gas by injecting liquid NOx reducing agent into the exhaust gas of the engine, and in particular, collects exhaust particulates in the exhaust gas. Therefore, the present invention is useful for an exhaust gas purification apparatus including a filter for regenerating and a filter regeneration means for regenerating the filter by raising the temperature.

1 is a schematic configuration diagram illustrating an engine exhaust gas purification apparatus according to an embodiment of the present invention. It is a flowchart which shows exhaust temperature suppression control and reducing agent injection valve control in ECU. FIG. 3 is a view corresponding to FIG. FIG. 9 is a view corresponding to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust purification apparatus 2 Exhaust passage 4 Filter 6 ECU (Filter regeneration means, abnormality detection means, injection prohibition means, target filter temperature change means, predetermined threshold amount change means, filter regeneration prohibition means, remaining amount detection means)
14 Remaining amount sensor (remaining amount detecting means)
15 Reducing agent injection valve 20 Reducing agent supply device 24 Pressure control valve (abnormality detecting means)

Claims (7)

A reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust; a reducing agent supply device that supplies the NOx reducing agent to the reducing agent injection valve; and a reducing agent injection valve Is disposed upstream of the exhaust, and collects exhaust particulates contained in the exhaust, and when the amount of exhaust particulates collected by the filter exceeds a predetermined threshold amount, the filter is used as a target filter. An engine exhaust purification device comprising: a filter regeneration means for regenerating the filter by raising the temperature to a temperature and removing the exhaust particulates by combustion;
An abnormality detecting means for detecting an abnormality of the reducing agent supply device;
Injection prohibiting means for prohibiting the injection of NOx reducing agent into the exhaust by the reducing agent injection valve when the abnormality of the reducing agent supply device is detected by the abnormality detecting means;
A target filter temperature changing means for lowering the target filter temperature when an abnormality of the reducing agent supply device is detected by the abnormality detection means, compared to a case where the abnormality is not detected. An exhaust gas purification device for an engine. A reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust; a reducing agent supply device that supplies the NOx reducing agent to the reducing agent injection valve; and a reducing agent injection valve Is disposed upstream of the exhaust, and collects exhaust particulates contained in the exhaust, and when the amount of exhaust particulates collected by the filter exceeds a predetermined threshold amount, the filter is used as a target filter. An engine exhaust purification device comprising: a filter regeneration means for regenerating the filter by raising the temperature to a temperature and removing the exhaust particulates by combustion;
An abnormality detecting means for detecting an abnormality of the reducing agent supply device;
Injection prohibiting means for prohibiting the injection of NOx reducing agent into the exhaust by the reducing agent injection valve when the abnormality of the reducing agent supply device is detected by the abnormality detecting means;
A predetermined threshold amount changing means for lowering the predetermined threshold amount when the abnormality is detected by the abnormality detecting means, compared to a case where the abnormality is not detected. An exhaust gas purification device for an engine. A reducing agent injection valve that is provided in an exhaust passage of the engine and injects a liquid NOx reducing agent into the exhaust; a reducing agent supply device that supplies the NOx reducing agent to the reducing agent injection valve; and a reducing agent injection valve Is disposed upstream of the exhaust, and collects exhaust particulates contained in the exhaust, and when the amount of exhaust particulates collected by the filter exceeds a predetermined threshold amount, the filter is used as a target filter. An engine exhaust purification device comprising: a filter regeneration means for regenerating the filter by raising the temperature to a temperature and removing the exhaust particulates by combustion;
An abnormality detecting means for detecting an abnormality of the reducing agent supply device;
Injection prohibiting means for prohibiting the injection of NOx reducing agent into the exhaust by the reducing agent injection valve when the abnormality of the reducing agent supply device is detected by the abnormality detecting means;
Engine exhaust further comprising: filter regeneration prohibiting means for prohibiting regeneration of the filter by the filter regeneration means when an abnormality of the reducing agent supply device is detected by the abnormality detection means. Purification equipment. A reducing agent injection valve provided in an exhaust passage of the engine for injecting a liquid NOx reducing agent into the exhaust; a tank for storing the NOx reducing agent; and the NOx reducing agent in the tank A reducing agent supply device that supplies the injection valve; a filter that is disposed on the exhaust upstream side of the reducing agent injection valve and that collects exhaust particulates contained in the exhaust; and the exhaust particulates collected by the filter Engine exhaust purification comprising: filter regeneration means for regenerating the filter by heating the filter to a target filter temperature and burning and removing the exhaust particulates when the amount exceeds a predetermined threshold amount A device,
A remaining amount detecting means for detecting a state in which the remaining amount of NOx reducing agent in the tank falls below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve;
When the state in which the remaining amount of the NOx reducing agent is below the predetermined level is detected by the remaining amount detecting unit, the target filter temperature changing unit lowers the target filter temperature compared to the case where the state is not detected. And an exhaust emission control device for an engine. A reducing agent injection valve provided in an exhaust passage of the engine for injecting a liquid NOx reducing agent into the exhaust; a tank for storing the NOx reducing agent; and the NOx reducing agent in the tank A reducing agent supply device that supplies the injection valve; a filter that is disposed on the exhaust upstream side of the reducing agent injection valve and that collects exhaust particulates contained in the exhaust; and the exhaust particulates collected by the filter Engine exhaust purification comprising: filter regeneration means for regenerating the filter by heating the filter to a target filter temperature and burning and removing the exhaust particulates when the amount exceeds a predetermined threshold amount A device,
A remaining amount detecting means for detecting a state in which the remaining amount of NOx reducing agent in the tank falls below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve;
When the state in which the remaining amount of the NOx reducing agent is below the predetermined level is detected by the remaining amount detecting unit, the predetermined threshold amount changing unit that lowers the predetermined threshold amount compared to the case where the state is not detected. And an exhaust emission control device for an engine. A reducing agent injection valve provided in an exhaust passage of the engine for injecting a liquid NOx reducing agent into the exhaust; a tank for storing the NOx reducing agent; and the NOx reducing agent in the tank A reducing agent supply device that supplies the injection valve; a filter that is disposed on the exhaust upstream side of the reducing agent injection valve and that collects exhaust particulates contained in the exhaust; and the exhaust particulates collected by the filter Engine exhaust purification comprising: filter regeneration means for regenerating the filter by heating the filter to a target filter temperature and burning and removing the exhaust particulates when the amount exceeds a predetermined threshold amount A device,
A remaining amount detecting means for detecting a state in which the remaining amount of NOx reducing agent in the tank falls below a predetermined level at which the reducing agent supply device can supply the NOx reducing agent to the reducing agent injection valve;
And a filter regeneration prohibiting unit for prohibiting filter regeneration by the filter regeneration unit when the remaining amount detecting unit detects that the remaining amount of the NOx reducing agent is below the predetermined level. An exhaust emission control device for an engine. The engine exhaust gas purification apparatus according to any one of claims 4 to 6,
Injection prohibiting means for prohibiting injection of NOx reducing agent into the exhaust gas by the reducing agent injection valve when the remaining amount detecting means detects that the remaining amount of the NOx reducing agent is below the predetermined level. An exhaust emission control device for an engine, further comprising:

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