JP2012241608A - Diagnostic apparatus for deterioration in catalyst in fuel-reforming system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose deterioration in a fuel-reforming catalyst while satisfying a cost reduction request, in a system including a function for reforming fuel to be supplied to an engine.SOLUTION: A diagnostic apparatus for deterioration in a catalyst in a fuel reforming system includes: an inlet-side temperature sensor 30 for detecting a temperature at an inlet side of a fuel reforming catalyst 28; and an outlet-side temperature sensor 31 for detecting a temperature at an outlet side of the fuel-reforming catalyst 28. In a reforming driving mode, an ECU 34 opens an EGR valve 25 to recirculate a part of exhaust gas into an intake side as EGR gas, and a reforming-fuel injection valve 26 injects a reforming fuel into the EGR gas. The fuel-reforming catalyst 28 executes reforming control to reform the fuel into a fuel having high-combustibility. A differential temperature between the catalyst outlet-side temperature detected by the outlet-side temperature sensor 31 and the catalyst inlet-side temperature detected by the inlet-side temperature sensor 30 is calculated during the execution of the reforming control and compared with a deterioration-determination threshold, whereby deterioration diagnosis can be performed to determine whether the fuel-reforming catalyst 28 is deteriorated.

Description

  The present invention relates to a catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine having a function of reforming fuel supplied to the internal combustion engine.

  As a technique for supplying reformed fuel to an internal combustion engine, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2004-218548), fuel supply for supplying fuel in a fuel tank to a fuel injection valve In some cases, a reformer provided with a heater or reforming catalyst for reforming fuel is disposed in the middle of the passage.

  In a system equipped with such a reformer, if the reformer becomes abnormal (for example, deterioration of the reforming catalyst) and the fuel cannot be reformed normally, the combustion state of the internal combustion engine may deteriorate. For this reason, when an abnormality occurs in the reformer, it is preferable to detect the abnormality early.

  Therefore, in Patent Document 1, paying attention to the fact that the physical properties (specific gravity and vapor pressure) of the fuel change when the reforming state of the fuel (for example, the content ratio of the high boiling point component) changes due to the abnormality of the reformer, A storage tank for storing the fuel sent from the reformer is provided on the downstream side of the reformer, and a sensor for detecting the physical properties (specific gravity or vapor pressure) of the fuel in the storage tank is provided. By comparing the physical properties of the fuel with the reference value, it is determined whether there is an abnormality in the reformer (reforming catalyst or the like).

JP 2004-218548 A

  However, in the abnormality diagnosis technique disclosed in Patent Document 1, it is necessary to provide a storage tank that stores the fuel sent from the reformer, and a special sensor that detects physical properties (for example, specific gravity) of the fuel in the storage tank. Therefore, there is a drawback that it is not possible to meet the demand for cost reduction which is an important technical problem in recent years.

  Therefore, the problem to be solved by the present invention is to provide a catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine, which can perform deterioration diagnosis of a fuel reforming catalyst while satisfying the demand for cost reduction. is there.

  In order to solve the above problems, the invention according to claim 1 is directed to reforming fuel injection means for injecting reforming fuel into a medium gas supplied to an intake system of an internal combustion engine, and fuel in the medium gas. In the catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine provided with a fuel reforming catalyst for reforming the fuel, reaction heat quantity information detecting means for detecting information of the reaction heat quantity in the fuel reforming catalyst, and the reaction heat quantity information The apparatus includes a catalyst deterioration diagnosis unit that performs a deterioration diagnosis of the fuel reforming catalyst based on information on the amount of reaction heat detected by the detection unit.

  When the fuel reforming catalyst deteriorates, the amount of reaction heat (heat generation amount or endothermic amount) at the fuel reforming catalyst decreases compared to when it is normal (when there is no deterioration). If used, it is possible to perform a deterioration diagnosis for determining whether or not the fuel reforming catalyst has deteriorated. Moreover, since there is no need to provide a storage tank for storing fuel or a special sensor for detecting the physical properties of the fuel as in the prior art, it can satisfy the demand for cost reduction, which is an important technical issue in recent years. it can.

  In this case, as in claim 2, as the reaction heat quantity information detecting means, the inlet side temperature detecting means for detecting the temperature on the inlet side of the fuel reforming catalyst (hereinafter referred to as “catalyst inlet side temperature”), and the fuel reforming catalyst An outlet side temperature detecting means for detecting the temperature of the outlet side of the catalyst (hereinafter referred to as “catalyst outlet side temperature”), and the catalyst deterioration diagnosing means during the reforming control for reforming the fuel with the fuel reforming catalyst. The deterioration diagnosis of the fuel reforming catalyst may be performed based on the catalyst inlet side temperature detected by the inlet side temperature detecting means and the catalyst outlet side temperature detected by the outlet side temperature detecting means.

  When the fuel reforming catalyst deteriorates, the amount of reaction heat at the fuel reforming catalyst decreases compared with the normal state (when there is no deterioration), and the catalyst inlet side temperature and the catalyst outlet side temperature during the reforming control are reduced. Since the relationship is different from the normal state, the presence or absence of deterioration of the fuel reforming catalyst can be accurately determined by using the catalyst inlet side temperature and the catalyst outlet side temperature detected during the reforming control. .

  Alternatively, as the reaction heat quantity information detecting means, the temperature of the fuel reforming catalyst (hereinafter referred to as “catalyst temperature”) or the temperature on the outlet side of the fuel reforming catalyst (hereinafter referred to as “catalyst outlet side temperature”). ), And the catalyst deterioration diagnosis means detects the catalyst temperature detected by the temperature detection means or the catalyst outlet side temperature and the reforming control before starting the reforming control for reforming the fuel by the fuel reforming catalyst. The deterioration diagnosis of the fuel reforming catalyst may be performed based on the catalyst temperature detected by the temperature detecting means or the catalyst outlet side temperature after the start of the operation.

  When the fuel reforming catalyst deteriorates, the amount of reaction heat at the fuel reforming catalyst decreases compared to when it is normal (when there is no deterioration), and the catalyst temperature before the start of reforming control or the catalyst outlet side temperature and reforming control. Since the relationship between the catalyst temperature after the start of the catalyst or the catalyst outlet side temperature is different from the normal time, the catalyst temperature detected before the start of the reform control or the catalyst outlet side temperature and the catalyst detected after the start of the reform control If the temperature or the catalyst outlet side temperature is used, the presence or absence of deterioration of the fuel reforming catalyst can be accurately determined.

  However, in the present invention, the deterioration diagnosis of the fuel reforming catalyst is performed based on the catalyst temperature detected by the temperature detecting means or the catalyst outlet side temperature after the start of the reforming control (that is, during the execution of the reforming control). Also good.

  According to a fourth aspect of the present invention, combustion state information detecting means for detecting information on the combustion state of the internal combustion engine, and deterioration diagnosis of the fuel reforming catalyst are performed based on the combustion state information detected by the combustion state information detecting means. It is good also as a structure provided with the catalyst deterioration diagnostic means to perform. When the fuel reforming catalyst deteriorates, the degree of fuel reforming by the fuel reforming catalyst decreases and the combustion state of the internal combustion engine changes compared to the normal state (when there is no deterioration). For example, it is possible to perform a deterioration diagnosis for determining whether or not the fuel reforming catalyst has deteriorated.

  In this case, as in claim 5, the catalyst deterioration diagnosis means includes the combustion state information detected by the combustion state information detection means and the reforming control information before the start of reforming control for reforming the fuel by the fuel reforming catalyst. The deterioration diagnosis of the fuel reforming catalyst may be performed based on the combustion state information detected by the combustion state information detecting means after the start. When the fuel reforming catalyst deteriorates, the degree of reforming of the fuel by the fuel reforming catalyst decreases compared with the normal state (when there is no deterioration), and the combustion state before starting reforming control and after starting reforming control. Therefore, if the information on the combustion state detected before the start of reforming control and the information on the combustion state detected after the start of reforming control are used, the fuel reforming The presence or absence of catalyst deterioration can be accurately determined.

  However, in the present invention, the deterioration diagnosis of the fuel reforming catalyst is performed based on the combustion state information detected by the combustion state information detecting means after the start of the reforming control (that is, during the execution of the reforming control). good.

  Further, as in claim 6, the combustion state information detecting means includes, as the combustion state information, a combustion stability index, an ignition delay period, a main combustion period, a combustion center of gravity, an in-cylinder pressure maximum value, an EGR limit, and a combustion speed. It is better to detect at least one of them. These parameters are information that accurately reflects the combustion state of the internal combustion engine.

  Further, as in claim 7, a reforming degree detecting means for detecting the reforming degree of the fuel on the outlet side of the fuel reforming catalyst, and a fuel based on the reforming degree of the fuel detected by the reforming degree detecting means. It is good also as a structure provided with the catalyst deterioration diagnostic means which performs the deterioration diagnosis of a reforming catalyst. When the fuel reforming catalyst deteriorates, the degree of reforming of the fuel by the fuel reforming catalyst is lower than when it is normal (when no deterioration occurs). A deterioration diagnosis for determining the presence or absence can be performed.

  In this case, as in claim 8, the catalyst deterioration diagnosis means detects the reforming degree of fuel and the reforming control detected by the reforming degree detection means before the start of reforming control for reforming the fuel with the fuel reforming catalyst. The deterioration diagnosis of the fuel reforming catalyst may be performed based on the degree of reforming of the fuel detected by the reforming degree detection means after the start of the operation. When the fuel reforming catalyst deteriorates, the degree of fuel reforming by the fuel reforming catalyst is lower than when it is normal (when there is no deterioration), and the degree of fuel reforming and reforming control before the start of reforming control are reduced. Since the relationship with the degree of reforming of fuel after the start of fuel is different from normal, the degree of reforming of fuel detected before the start of reforming control and the degree of reforming of fuel detected after starting reforming control Can be used to accurately determine whether the fuel reforming catalyst has deteriorated.

  However, in the present invention, the deterioration diagnosis of the fuel reforming catalyst is performed based on the reforming degree of the fuel detected by the reforming degree detecting means after the start of the reforming control (that is, during the execution of the reforming control). Also good.

  Further, in the case of a system for reforming a fuel to a high hydrogen concentration state using a fuel reforming catalyst, the reforming degree detection means includes a hydrogen sensor that detects the hydrogen concentration as the reforming degree of the fuel. It may be used. In this way, the reforming degree (hydrogen concentration) of the fuel can be detected with high accuracy.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in Embodiment 1 of the present invention. FIG. 2 is a time chart for explaining the deterioration diagnosis method of Example 1 (in the case of an exothermic reaction catalyst). FIG. 3 is a time chart for explaining the deterioration diagnosis method of Example 1 (in the case of an endothermic reaction catalyst). FIG. 4 is a flowchart showing the flow of processing of the catalyst deterioration diagnosis routine of the first embodiment (in the case of an exothermic reaction catalyst). FIG. 5 is a diagram for explaining the relationship between the reforming fuel injection amount and the deterioration determination threshold value. FIG. 6 is a diagram for explaining the relationship between the EGR gas flow rate and the deterioration determination threshold value. FIG. 7 is a flowchart showing the flow of processing of the catalyst deterioration diagnosis routine of Example 1 (in the case of an endothermic reaction catalyst). FIG. 8 is a time chart for explaining an execution example of catalyst deterioration diagnosis in Example 1 (in the case of an exothermic reaction catalyst). FIG. 9 is a time chart for explaining an execution example of the catalyst deterioration diagnosis of Example 1 (in the case of an endothermic reaction catalyst). FIG. 10 is a diagram illustrating a schematic configuration of an engine control system according to the second embodiment. FIG. 11 is a time chart for explaining the deterioration diagnosis method according to the second embodiment. FIG. 12 is a flowchart showing the flow of processing of the catalyst deterioration diagnosis routine of the second embodiment. FIG. 13 is a time chart for explaining an execution example of the catalyst deterioration diagnosis of the second embodiment. FIG. 14 is a diagram illustrating a schematic configuration of an engine control system according to the third embodiment. FIG. 15 is a time chart for explaining the deterioration diagnosis method of the third embodiment. FIG. 16 is a flowchart showing the flow of processing of the catalyst deterioration diagnosis routine of the third embodiment. FIG. 17 is a time chart illustrating an execution example of catalyst deterioration diagnosis according to the third embodiment.

  Hereinafter, some embodiments embodying the mode for carrying out the present invention will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.

  An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and a throttle valve 14 whose opening degree is adjusted by a motor or the like is provided downstream of the air cleaner 13.

  Further, a surge tank 15 is provided on the downstream side of the throttle valve 14. The surge tank 15 is provided with an intake manifold 16 for introducing air into each cylinder of the engine 11, and an intake port (not shown) connected to the intake manifold 16 of each cylinder or the vicinity thereof is connected to each intake port. A fuel injection valve 17 for injecting fuel is attached. A spark plug 18 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 18.

  On the other hand, the exhaust pipe 19 of the engine 11 is provided with a catalyst 20 such as a three-way catalyst for purifying exhaust gas, and the exhaust gas air-fuel ratio or rich / lean is set on the upstream side and downstream side of the catalyst 20, respectively. Exhaust gas sensors 21 and 22 (air-fuel ratio sensor, oxygen sensor, etc.) to be detected are provided.

  The engine 11 is equipped with an EGR device 23 that recirculates a part of the exhaust gas to the intake side as EGR gas. In the EGR device 23, an EGR pipe 24 is connected between the upstream side of the catalyst 20 in the exhaust pipe 19 and the downstream side of the throttle valve 14 in the intake pipe 12, and the exhaust gas return is connected to the EGR pipe 24. An EGR valve 25 for adjusting the flow rate (external EGR amount) is provided.

  Further, the EGR pipe 24 includes a fuel injection device 27 provided with a reforming fuel injection valve 26 (reforming fuel injection means) for injecting reforming fuel into EGR gas (medium gas), and EGR gas. A fuel reformer 29 including a fuel reforming catalyst 28 for reforming the fuel therein is provided. As reaction heat quantity information detecting means for detecting information of reaction heat quantity in the fuel reforming catalyst 28, an inlet side for detecting the temperature of EGR gas on the inlet side of the fuel reforming catalyst 28 (hereinafter referred to as "catalyst inlet side temperature"). A temperature sensor 30 (inlet side temperature detecting means) and an outlet side temperature sensor 31 (outlet side temperature detecting means) for detecting the temperature of the EGR gas on the outlet side of the fuel reforming catalyst 28 (hereinafter referred to as “catalyst outlet side temperature”). And are provided. Fuel is supplied from a common fuel tank (not shown) to the fuel injection valve 17 and the reforming fuel injection valve 26 of each cylinder.

  The engine 11 is provided with an air flow meter 32 for detecting the intake air amount, a crank angle sensor 33 for outputting a pulse signal each time a crankshaft (not shown) rotates a predetermined crank angle, and the like. Based on the output signal of the sensor 33, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 34. The ECU 34 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount and the ignition timing according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  Further, the ECU 34 switches from the normal operation mode to the reforming operation mode when the operating state of the engine 11 is in a predetermined reforming operation region (for example, a low rotation / low load operation region). In this reforming operation mode, the reforming fuel injection valve 26 injects reforming fuel into the EGR gas while the EGR valve 25 is opened and a part of the exhaust gas is recirculated to the intake side as EGR gas. The reformed fuel is then vaporized, and reforming control is performed to reform the fuel in the EGR gas to a highly combustible state (for example, a state having a high hydrogen concentration) by the fuel reforming catalyst 28. 11 to the intake pipe 12.

  When the fuel reforming catalyst 28 is an exothermic reaction catalyst, the ECU 34 executes a catalyst deterioration diagnosis routine of FIG. 4 to be described later, whereby the catalyst outlet side temperature detected by the outlet side temperature sensor 31 during the reforming control is detected. A deterioration diagnosis for determining whether or not the fuel reforming catalyst 28 has deteriorated is performed by comparing a temperature difference with the catalyst inlet side temperature detected by the inlet side temperature sensor 30 with a predetermined deterioration determination threshold value.

  As shown in FIG. 2, when the fuel reforming catalyst 28 is an exothermic reaction catalyst, when the fuel reforming catalyst 28 deteriorates, the amount of heat generated by the fuel reforming catalyst 28 decreases compared to when it is normal (without deterioration). Thus, since the degree of increase in the catalyst outlet side temperature with respect to the catalyst inlet side temperature during the reforming control is different from that during normal operation, the catalyst outlet side temperature and the catalyst inlet side temperature detected during the reforming control are different. Is compared with the deterioration determination threshold value, the presence or absence of deterioration of the fuel reforming catalyst 28 can be accurately determined.

  The processing contents of the catalyst deterioration diagnosis routine of FIG. 4 executed by the ECU 34 when the fuel reforming catalyst 28 is an exothermic reaction catalyst will be described below.

  The catalyst deterioration diagnosis routine shown in FIG. 4 is repeatedly executed at a predetermined period during the power-on period of the ECU 34 (while the ignition switch is on), and serves as catalyst deterioration diagnosis means in the claims. When this routine is started, first, in step 101, it is determined whether or not it is the reforming operation mode, and if it is determined that it is not the reforming operation mode (that is, the normal operation mode), step This routine is terminated without performing the processing after 102.

  On the other hand, if it is determined in step 101 that the reforming operation mode is set, the processing after step 102 is executed as follows. First, in step 102, the EGR valve 25 is opened so that a part of the exhaust gas is recirculated to the intake side as EGR gas, and then the process proceeds to step 103, where the reforming fuel injection valve 26 enters the EGR gas. The reforming control is performed in which the fuel in the EGR gas is reformed to a highly combustible state by the fuel reforming catalyst 28 by injecting and vaporizing the reforming fuel. At this time, the injection amount of the reforming fuel and the EGR gas flow rate (for example, the opening degree of the EGR valve 25) are calculated by a map or the like according to the engine operating state (for example, the engine speed, the engine load, etc.).

  Thereafter, the process proceeds to step 104, and after the catalyst inlet side temperature detected by the inlet side temperature sensor 30 and the catalyst outlet side temperature detected by the outlet side temperature sensor 31 are read, the process proceeds to step 105 and the injection amount of reforming fuel is injected. And a deterioration determination threshold value corresponding to the EGR gas flow rate are calculated using a map or the like. When the fuel reforming catalyst 28 is an exothermic reaction catalyst, for example, the deterioration determination threshold map increases as the fuel injection amount for reforming increases (see FIG. 5), and as the EGR gas flow rate increases. The deterioration determination threshold is set to be large (see FIG. 6). Furthermore, the deterioration determination threshold value may be corrected according to the catalyst inlet side temperature.

  Thereafter, the process proceeds to step 106, where it is determined whether or not the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is equal to or greater than the deterioration determination threshold value. If it is determined in step 106 that the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is greater than or equal to the deterioration determination threshold value, the process proceeds to step 107, where the fuel reforming catalyst 28 is not deteriorated (normal). Determination is made and this routine is terminated.

  On the other hand, when it is determined in step 106 that the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is smaller than the deterioration determination threshold value, the process proceeds to step 108 and the fuel reforming catalyst 28 is deteriorated. It is determined that there is an abnormality (abnormal), and the process proceeds to step 109 to execute fail-safe processing. In this fail-safe process, the opening degree of the EGR valve 25 is decreased to reduce the EGR gas flow rate, and the reforming fuel injection by the reforming fuel injection valve 26 is stopped to prohibit the reforming of the fuel. .

  On the other hand, when the fuel reforming catalyst 28 is an endothermic reaction catalyst, the ECU 34 executes a catalyst deterioration diagnosis routine of FIG. 7 to be described later, thereby detecting the catalyst outlet side detected by the outlet side temperature sensor 31 during the reforming control. A deterioration diagnosis for determining the presence or absence of deterioration of the fuel reforming catalyst 28 is performed by comparing the temperature difference between the temperature and the catalyst inlet side temperature detected by the inlet side temperature sensor 30 with a predetermined deterioration determination threshold value.

  As shown in FIG. 3, when the fuel reforming catalyst 28 is an endothermic reaction catalyst, when the fuel reforming catalyst 28 deteriorates, the endothermic amount at the fuel reforming catalyst 28 decreases as compared with the normal time (when there is no deterioration). Thus, the catalyst outlet side temperature and the catalyst inlet side temperature detected during the reforming control are different because the degree of decrease in the catalyst outlet side temperature with respect to the catalyst inlet side temperature during the reforming control is different from the normal state. Is compared with the deterioration determination threshold value, the presence or absence of deterioration of the fuel reforming catalyst 28 can be accurately determined.

  The processing contents of the catalyst deterioration diagnosis routine of FIG. 7 executed by the ECU 34 when the fuel reforming catalyst 28 is an endothermic reaction catalyst will be described below. The routine of FIG. 7 is obtained by changing the process of step 106 of the routine of FIG. 4 to the process of step 106a.

  In this routine, if it is determined in step 101 that the reforming operation mode is selected, the process proceeds to step 102, the EGR valve 25 is opened, then the process proceeds to step 103, and the reforming fuel injection valve 26 reforms. Fuel reforming control is performed in which fuel for fuel is injected and fuel in the EGR gas is reformed by the fuel reforming catalyst 28.

  Thereafter, the process proceeds to step 104, and the catalyst inlet side temperature and the catalyst outlet side temperature are read. Then, the process proceeds to step 105, and a deterioration determination threshold value corresponding to the injection amount of the reforming fuel and the EGR gas flow rate is calculated using a map or the like. . When the fuel reforming catalyst 28 is an endothermic reaction catalyst, for example, the deterioration determination threshold map is such that the deterioration determination threshold decreases as the injection amount of the reforming fuel increases, and the deterioration determination threshold decreases as the EGR gas flow rate increases. It is set to be. Furthermore, the deterioration determination threshold value may be corrected according to the catalyst inlet side temperature.

  Thereafter, the process proceeds to step 106a, and it is determined whether or not the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is equal to or less than the deterioration determination threshold value. If it is determined in step 106a that the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is equal to or less than the deterioration determination threshold value, the process proceeds to step 107, where the fuel reforming catalyst 28 is not deteriorated (normal). Determination is made and this routine is terminated.

  On the other hand, when it is determined in step 106a that the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature is larger than the deterioration determination threshold value, the process proceeds to step 108 and the fuel reforming catalyst 28 is deteriorated. It is determined that the engine is present (abnormal), and the process proceeds to step 109 to execute a fail-safe process (a process for reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel).

An execution example of the catalyst deterioration diagnosis according to the first embodiment will be described with reference to FIGS. 8 and 9.
As shown in FIGS. 8 and 9, when the normal operation mode is switched to the reforming operation mode, the EGR valve 25 is opened and a part of the exhaust gas is recirculated to the intake side as EGR gas. The quality control fuel injection valve 26 injects reforming fuel into the EGR gas and the fuel reforming catalyst 28 reforms the fuel in the EGR gas into a highly combustible state.

  In the first embodiment, the temperature difference between the catalyst outlet side temperature detected by the outlet side temperature sensor 31 and the catalyst inlet side temperature detected by the inlet side temperature sensor 30 during the execution of the reforming control is calculated, and this temperature difference is calculated. Is compared with the deterioration determination threshold value to perform the deterioration diagnosis for determining whether or not the fuel reforming catalyst 28 has deteriorated. Therefore, it is possible to accurately determine whether or not the fuel reforming catalyst 28 has deteriorated. Moreover, since there is no need to provide a storage tank for storing fuel or a special sensor for detecting the physical properties of the fuel as in the prior art, it can satisfy the demand for cost reduction, which is an important technical issue in recent years. it can.

  Further, as shown by broken lines in FIGS. 8 and 9, in a system that does not have a function for diagnosing the deterioration of the fuel reforming catalyst 28, even if the fuel reforming catalyst 28 is deteriorated, it cannot be detected, and the fuel Since fail-safe processing cannot be performed when deterioration of the reforming catalyst 28 occurs, the combustion state of the engine 11 deteriorates, torque fluctuations may occur, and drivability may deteriorate.

  In contrast, in the first embodiment, the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature detected during the execution of the reforming control is compared with the deterioration determination threshold value to determine whether or not the fuel reforming catalyst 28 has deteriorated. If it is determined that the fuel reforming catalyst 28 is deteriorated, a fail-safe process (a process of reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel) Therefore, the deterioration of the combustion state of the engine 11 can be suppressed to suppress the occurrence of torque fluctuation, and the drivability can be prevented from being deteriorated.

  In the first embodiment, the temperature difference between the catalyst outlet side temperature and the catalyst inlet side temperature detected during the reforming control is compared with the deterioration determination threshold value to determine whether the fuel reforming catalyst 28 has deteriorated. However, the deterioration diagnosis method is not limited to this, and may be changed as appropriate. For example, the deterioration determination is performed based on the temperature ratio between the catalyst outlet side temperature and the catalyst inlet side temperature detected during the execution of the reforming control. The presence or absence of deterioration of the fuel reforming catalyst 28 may be determined by comparison with a threshold value.

  Further, the deterioration of the fuel reforming catalyst 28 is compared by comparing the temperature difference or temperature ratio between the catalyst outlet side temperature detected before the start of the reforming control and the catalyst outlet side temperature detected after the start of the reforming control with the deterioration determination threshold value. It may be determined whether or not there is. Alternatively, a catalyst temperature sensor for detecting the temperature of the fuel reforming catalyst 28 (catalyst temperature) is provided, and the temperature difference between the catalyst temperature detected before the start of reforming control and the catalyst temperature detected after the start of reforming control or The presence or absence of deterioration of the fuel reforming catalyst 28 may be determined by comparing the temperature ratio with a deterioration determination threshold value.

  When the fuel reforming catalyst 28 deteriorates, the amount of heat of reaction at the fuel reforming catalyst 28 decreases compared with the normal time (when there is no deterioration), and the catalyst temperature before the start of reforming control or the catalyst outlet side temperature is improved. Since the relationship between the catalyst temperature after the start of quality control or the catalyst outlet side temperature is different from the normal state, the catalyst temperature detected before the start of reforming control or the catalyst outlet side temperature and the detection after the start of reforming control are detected. By using the catalyst temperature or the catalyst outlet side temperature, it is possible to accurately determine whether the fuel reforming catalyst 28 has deteriorated.

  However, the present invention determines whether or not the fuel reforming catalyst 28 has deteriorated by comparing the catalyst temperature or the catalyst outlet side temperature detected after the start of reforming control (that is, during execution of reforming control) with the deterioration determination value. You may make it do.

  Next, a second embodiment of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, as shown in FIG. 10, the cylinder head of the engine 11 has a cylinder head of the engine 11 as a combustion state detection sensor that detects a combustion state for each cylinder (or only a specific cylinder). An in-cylinder pressure sensor 35 for detecting the in-cylinder pressure is provided in the cylinder only). The in-cylinder pressure sensor 35 may be of a type integrated with the spark plug 18 or may be of a type attached separately from the spark plug 18. Note that the temperature sensors 30 and 31 may be omitted.

  Further, in the second embodiment, the ECU 34 executes a catalyst deterioration diagnosis routine shown in FIG. 12 to be described later, so that information on the combustion state of the engine 11 is obtained based on the output of the in-cylinder pressure sensor 35 during the reforming control. A certain combustion parameter is calculated (detected), and this combustion parameter is compared with a predetermined deterioration determination threshold value to perform deterioration diagnosis for determining whether or not the fuel reforming catalyst 28 has deteriorated. Here, as the combustion parameter, for example, one of a combustion stability index COV (for example, a fluctuation rate of the indicated mean effective pressure), an ignition delay period, a main combustion period, a combustion center of gravity, a maximum in-cylinder pressure value, and the like is calculated. To do.

  As shown in FIG. 11, when the fuel reforming catalyst 28 deteriorates, the degree of fuel reforming by the fuel reforming catalyst 28 decreases and the combustion state of the engine 11 changes as compared with the normal time (without deterioration). Since the combustion parameter changes, the presence or absence of deterioration of the fuel reforming catalyst 28 can be accurately determined by comparing the combustion parameter detected during the execution of the reforming control with the deterioration determination threshold value.

  Hereinafter, the processing content of the catalyst deterioration diagnosis routine of FIG. 12 executed by the ECU 34 in the second embodiment will be described.

  The catalyst deterioration diagnosis routine shown in FIG. 12 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 34. When this routine is started, first, at step 201, it is determined whether or not it is the reforming operation mode. When it is determined that it is the reforming operation mode, the routine proceeds to step 202 and the EGR valve 25 is turned on. After the valve is opened, the routine proceeds to step 203, where reforming fuel is injected by the reforming fuel injection valve 26, and reforming control for reforming the fuel in the EGR gas by the fuel reforming catalyst 28 is executed.

  Thereafter, the routine proceeds to step 204, where one of the combustion parameters (eg, combustion stability index COV, ignition delay period, main combustion period, combustion center of gravity, in-cylinder pressure maximum value, etc.) is determined based on the output of the in-cylinder pressure sensor 35. One). The processing in step 204 serves as a combustion state information detecting means in the claims.

  Thereafter, the process proceeds to step 205, and a deterioration determination threshold corresponding to the injection amount of the reforming fuel and the EGR gas flow rate is calculated using a map or the like. Furthermore, the deterioration determination threshold value may be corrected according to the combustion parameter detected before the start of reforming control.

  Thereafter, the process proceeds to step 206, where the combustion parameter is compared with a deterioration determination threshold value to determine whether the combustion parameter is within a normal range. At this time, when the combustion stability index COV, the ignition delay period, and the main combustion period are used as the combustion parameters, the combustion parameters (the combustion stability index COV, the ignition delay period, and the main combustion period) are equal to or less than the deterioration determination threshold value. Whether or not the combustion parameter is within the normal range is determined. On the other hand, when the combustion center of gravity and the maximum in-cylinder pressure are used as the combustion parameter, the combustion parameter is within the normal range depending on whether or not the combustion parameter (combustion center of gravity and maximum in-cylinder pressure) is equal to or greater than the deterioration determination threshold. It is determined whether or not.

  If it is determined in step 206 that the combustion parameter is within the normal range, the process proceeds to step 207, where it is determined that the fuel reforming catalyst 28 has not deteriorated (normal), and this routine ends.

  On the other hand, if it is determined in step 206 that the combustion parameter is not within the normal range, the process proceeds to step 208, where it is determined that the fuel reforming catalyst 28 has deteriorated (abnormal), and the process proceeds to step 209. Advancing and performing a fail-safe process (a process of reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel).

An execution example of the catalyst deterioration diagnosis according to the second embodiment will be described with reference to FIG.
As shown in FIG. 13, when the normal operation mode is switched to the reforming operation mode, the EGR valve 25 is opened and a part of the exhaust gas is recirculated to the intake side as EGR gas, and the reforming fuel The reforming control is performed in which the fuel for reforming is injected into the EGR gas by the injection valve 26, and the fuel in the EGR gas is reformed to a highly combustible state by the fuel reforming catalyst 28.

  In the second embodiment, during execution of the reforming control, a combustion parameter that is information on the combustion state of the engine 11 is calculated (detected) based on the output of the in-cylinder pressure sensor 35, and this combustion parameter is used as a deterioration determination threshold value. In comparison, since the deterioration diagnosis for determining whether or not the fuel reforming catalyst 28 has deteriorated is performed, the presence or absence of deterioration of the fuel reforming catalyst 28 can be accurately determined.

  Further, as shown by a broken line in FIG. 13, in a system that does not have a function for diagnosing the deterioration of the fuel reforming catalyst 28, even if the fuel reforming catalyst 28 is deteriorated, it cannot be detected. Since the fail-safe process cannot be performed when the deterioration 28 occurs, there is a possibility that the combustion state of the engine 11 deteriorates and torque fluctuations occur and drivability deteriorates.

  On the other hand, in the second embodiment, the combustion parameter detected during the execution of the reforming control is compared with the degradation determination threshold value to determine whether or not the fuel reforming catalyst 28 is degraded, and the degradation of the fuel reforming catalyst 28 is determined. When it is determined that there is, the fail safe process (the process of reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel) is executed. It is possible to suppress the deterioration of the combustion state and suppress the occurrence of torque fluctuation, and to prevent the deterioration of drivability.

  In the second embodiment, the combustion parameter detected during the execution of the reforming control is compared with the deterioration determination threshold value to determine whether or not the fuel reforming catalyst 28 has deteriorated. For example, the difference or ratio between the combustion parameter detected before the start of the reforming control and the combustion parameter detected after the start of the reforming control is compared with the deterioration determination threshold value. The presence or absence of deterioration of the reforming catalyst 28 may be determined.

  When the fuel reforming catalyst 28 deteriorates, the degree of reforming of the fuel by the fuel reforming catalyst 28 is reduced as compared with the normal state (when there is no deterioration), and the combustion state and the reforming control before the start of the reforming control are reduced. Since the relationship with the combustion state after the start is different from the normal state, the fuel reforming catalyst 28 can be obtained by using the combustion parameter detected before the start of the reforming control and the combustion parameter detected after the start of the reforming control. The presence or absence of deterioration can be determined with high accuracy.

  In the second embodiment, the combustion stability index COV, the ignition delay period, the main combustion period, the combustion center of gravity, the in-cylinder pressure maximum value, and the like are detected as the combustion parameters (combustion state information). For example, EGR limit, combustion speed, engine rotation fluctuation, torque fluctuation, etc. may be detected as the combustion parameter (combustion state information).

  In the second embodiment, the in-cylinder pressure sensor 35 is used as a sensor for detecting the combustion state. However, the present invention is not limited to this. For example, a sensor for detecting an ionic current flowing through the ignition plug 18 is an ignition plug. 18 may be provided integrally or separately.

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those of the first and second embodiments will be omitted or simplified, and different parts from the first and second embodiments will be mainly described.

  In the third embodiment, as shown in FIG. 14, a reforming degree sensor 36 (reforming degree detecting means) for detecting the reforming degree of fuel is provided on the outlet side of the fuel reforming catalyst 28 in the EGR pipe 24. Is provided. The reforming degree sensor 36 uses, for example, a hydrogen sensor that detects the hydrogen concentration as the degree of reforming of the fuel. Note that the temperature sensors 30 and 31 may be omitted.

  Further, in the third embodiment, the ECU 34 executes a catalyst deterioration diagnosis routine shown in FIG. 16 to be described later, so that the fuel reforming degree (for example, hydrogen concentration) detected by the reforming degree sensor 36 during the execution of reforming control. Is compared with a predetermined deterioration determination threshold value to perform deterioration diagnosis for determining whether or not the fuel reforming catalyst 28 has deteriorated.

  As shown in FIG. 15, when the fuel reforming catalyst 28 deteriorates, the degree of fuel reforming by the fuel reforming catalyst 28 decreases compared with the normal time (when no deterioration occurs). By comparing the detected degree of reforming with the deterioration determination threshold value, it is possible to accurately determine whether the fuel reforming catalyst 28 has deteriorated.

  Hereinafter, the processing content of the catalyst deterioration diagnosis routine of FIG. 16 executed by the ECU 34 in the third embodiment will be described.

  The catalyst deterioration diagnosis routine shown in FIG. 16 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 34. When this routine is started, first, at step 301, it is determined whether or not it is the reforming operation mode. When it is determined that it is the reforming operation mode, the routine proceeds to step 302 and the EGR valve 25 is turned on. After the valve is opened, the routine proceeds to step 303, where reforming fuel is injected by the reforming fuel injection valve 26, and reforming control for reforming the fuel in the EGR gas by the fuel reforming catalyst 28 is executed.

  Thereafter, the process proceeds to step 304, and after reading the reforming degree (for example, hydrogen concentration) of the fuel detected by the reforming degree sensor 36, the process proceeds to step 305, in accordance with the injection amount of the reforming fuel and the EGR gas flow rate. A deterioration determination threshold value is calculated using a map or the like. Furthermore, the deterioration determination threshold value may be corrected according to the degree of reform detected before the start of reform control.

  Thereafter, the process proceeds to step 306, where it is determined whether or not the reforming degree is equal to or greater than a deterioration determination threshold value. If it is determined in step 306 that the reforming degree is equal to or greater than the deterioration determination threshold value, the process proceeds to step 307, where it is determined that the fuel reforming catalyst 28 has not deteriorated (normal), and this routine ends.

  On the other hand, if it is determined in step 306 that the reforming degree is smaller than the deterioration determination threshold, the process proceeds to step 308, where it is determined that the fuel reforming catalyst 28 has deteriorated (abnormal), and step Proceeding to 309, a fail-safe process (a process of reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel) is executed.

An execution example of the catalyst deterioration diagnosis according to the third embodiment will be described with reference to FIG.
As shown in FIG. 17, when the normal operation mode is switched to the reforming operation mode, the EGR valve 25 is opened and a part of the exhaust gas is recirculated to the intake side as EGR gas, and the reforming fuel The reforming control is performed in which the fuel for reforming is injected into the EGR gas by the injection valve 26, and the fuel in the EGR gas is reformed to a highly combustible state by the fuel reforming catalyst 28.

  In the third embodiment, the reforming degree sensor 36 detects the reforming degree (for example, hydrogen concentration) of the fuel during execution of the reforming control, and compares the reforming degree with the deterioration determination threshold value, thereby the fuel reforming catalyst 28. Since the deterioration diagnosis for determining the presence or absence of the deterioration is performed, the presence or absence of the deterioration of the fuel reforming catalyst 28 can be accurately determined.

  Further, as shown by a broken line in FIG. 17, in a system that does not have a function for diagnosing the deterioration of the fuel reforming catalyst 28, even if the fuel reforming catalyst 28 is deteriorated, it cannot be detected. Since the fail-safe process cannot be performed when the deterioration 28 occurs, there is a possibility that the combustion state of the engine 11 deteriorates and torque fluctuations occur and drivability deteriorates.

  On the other hand, in the third embodiment, the reforming degree detected during the execution of the reforming control is compared with the degradation determination threshold value to determine whether or not the fuel reforming catalyst 28 has deteriorated. When it is determined that there is deterioration, a fail-safe process (a process of reducing the EGR gas flow rate and stopping the reforming fuel injection to prohibit the reforming of the fuel) is executed. The deterioration of the combustion state can be suppressed to suppress the occurrence of torque fluctuation, and the drivability can be prevented from deteriorating.

  In the third embodiment, the degree of deterioration of the fuel reforming catalyst 28 is determined by comparing the degree of reforming detected during the execution of the reforming control with the deterioration determination threshold value. For example, the difference or ratio between the reforming degree detected before the start of the reforming control and the reforming degree detected after the start of the reforming control is compared with the deterioration determination threshold value. Thus, the presence or absence of deterioration of the fuel reforming catalyst 28 may be determined.

  When the fuel reforming catalyst 28 deteriorates, the degree of fuel reforming by the fuel reforming catalyst 28 is lower than when normal (when there is no deterioration), and the degree of fuel reforming before the start of reforming control is improved. The relationship between the reforming degree of the fuel after the start of the quality control differs from the normal time, so the reforming degree detected before starting the reforming control and the reforming degree detected after starting the reforming control are If used, the presence or absence of deterioration of the fuel reforming catalyst 28 can be accurately determined.

  In the first to third embodiments, the present invention is applied to a system in which a reforming fuel injection valve and a fuel reforming catalyst are arranged in an EGR pipe. However, the present invention is not limited to this. The present invention may be applied to a system in which a supercharger for supercharging is provided and a reforming fuel injection valve and a fuel reforming catalyst are arranged downstream of the supercharger in the intake pipe.

  In addition, the present invention is not limited to the intake port injection type engine, but is an in-cylinder injection type engine or a dual injection type engine having both a fuel injection valve for intake port injection and a fuel injection valve for in-cylinder injection. It can also be applied to.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Throttle valve, 17 ... Fuel injection valve, 18 ... Spark plug, 19 ... Exhaust pipe, 23 ... EGR device, 24 ... EGR piping, 25 ... EGR valve, 26 ... reforming fuel injection valve (reforming fuel injection means), 27 ... fuel injection device, 28 ... fuel reforming catalyst, 29 ... fuel reformer, 30 ... inlet side temperature sensor (inlet side temperature detecting means), 31... Outlet side temperature sensor (outlet side temperature detection means) 34... ECU (catalyst deterioration diagnosis means, combustion state information detection means) 35 .. cylinder pressure sensor 36 .. reforming degree sensor (reforming degree detection means)

Claims (9)

An internal combustion engine comprising: a reforming fuel injection means for injecting a reforming fuel into a medium gas supplied to an intake system of the internal combustion engine; and a fuel reforming catalyst for reforming the fuel in the medium gas. In the catalyst deterioration diagnosis device of the fuel reforming system,
Reaction heat quantity information detecting means for detecting information of the reaction heat quantity in the fuel reforming catalyst;
A catalyst deterioration diagnosis unit for diagnosing deterioration of the fuel reforming catalyst based on information of the reaction heat amount detected by the reaction heat amount information detection unit; Diagnostic device. As the reaction heat quantity information detecting means, an inlet side temperature detecting means for detecting an inlet side temperature of the fuel reforming catalyst (hereinafter referred to as “catalyst inlet side temperature”), and an outlet side temperature of the fuel reforming catalyst (hereinafter referred to as “catalyst inlet side temperature”). An outlet side temperature detecting means for detecting "catalyst outlet side temperature"),
The catalyst deterioration diagnosing means includes a catalyst inlet side temperature detected by the inlet side temperature detecting means and a catalyst outlet detected by the outlet side temperature detecting means during execution of reforming control for reforming fuel by the fuel reforming catalyst. 2. The catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine according to claim 1, wherein the deterioration diagnosis of the fuel reforming catalyst is performed based on a side temperature. Temperature detecting means for detecting the temperature of the fuel reforming catalyst (hereinafter referred to as “catalyst temperature”) or the temperature on the outlet side of the fuel reforming catalyst (hereinafter referred to as “catalyst outlet side temperature”) as the reaction heat quantity information detecting means. With
The catalyst deterioration diagnosing means detects the temperature of the catalyst or the catalyst outlet side detected by the temperature detecting means before the start of reforming control for reforming the fuel with the fuel reforming catalyst and the temperature after starting the reforming control. The catalyst deterioration diagnosis apparatus for a fuel reforming system of an internal combustion engine according to claim 1, wherein the deterioration diagnosis of the fuel reforming catalyst is performed based on the catalyst temperature detected by the means or the catalyst outlet side temperature. An internal combustion engine comprising: a reforming fuel injection means for injecting a reforming fuel into a medium gas supplied to an intake system of the internal combustion engine; and a fuel reforming catalyst for reforming the fuel in the medium gas. In the catalyst deterioration diagnosis device of the fuel reforming system,
Combustion state information detecting means for detecting information on the combustion state of the internal combustion engine;
Catalyst deterioration diagnosis means for diagnosing deterioration of the fuel reforming catalyst based on information on the combustion state detected by the combustion state information detection means. Diagnostic device.   The catalyst deterioration diagnosing means includes information on the combustion state detected by the combustion state information detecting means before the start of reforming control for reforming fuel with the fuel reforming catalyst and the combustion state information after starting the reforming control. 5. The catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine according to claim 4, wherein the deterioration diagnosis of the fuel reforming catalyst is performed based on information on a combustion state detected by a detecting means.   The combustion state information detection means detects at least one of a combustion stability index, an ignition delay period, a main combustion period, a combustion center of gravity, an in-cylinder pressure maximum value, an EGR limit, and a combustion speed as the combustion state information. The catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine according to claim 4 or 5, wherein An internal combustion engine comprising: a reforming fuel injection means for injecting a reforming fuel into a medium gas supplied to an intake system of the internal combustion engine; and a fuel reforming catalyst for reforming the fuel in the medium gas. In the catalyst deterioration diagnosis device of the fuel reforming system,
A reforming degree detecting means for detecting the reforming degree of the fuel on the outlet side of the fuel reforming catalyst;
A catalyst for diagnosing deterioration of the fuel reforming catalyst based on the degree of reforming of the fuel detected by the reforming degree detecting means; Deterioration diagnostic device.   The catalyst deterioration diagnosing means includes a fuel reforming degree detected by the reforming degree detecting means before starting reforming control for reforming fuel by the fuel reforming catalyst and the reforming after starting reforming control. 8. The catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine according to claim 7, wherein deterioration diagnosis of the fuel reforming catalyst is performed based on a fuel reforming degree detected by a degree detecting means.   The catalyst deterioration diagnosis device for a fuel reforming system of an internal combustion engine according to claim 7 or 8, wherein the reforming degree detection means is a hydrogen sensor that detects a hydrogen concentration as the reforming degree of the fuel.

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