WO2014136387A1

WO2014136387A1 - Abnormality diagnosis device for internal combustion engine

Info

Publication number: WO2014136387A1
Application number: PCT/JP2014/000821
Authority: WO
Inventors: 福田　圭佑; 若原　啓二; 和賢野々山; 向井　弥寿夫; 和田　実; 優一竹村
Original assignee: 株式会社デンソー
Priority date: 2013-03-05
Filing date: 2014-02-18
Publication date: 2014-09-12
Also published as: JP2014196734A

Abstract

A control unit (80) executes a first determination process for determining whether the combustion state of an engine (10) is normal or abnormal during a period in which the engine (10) is operated on the basis of one fuel, said determination being made on the basis of the combustion parameters for that period. After the combustion state has been determined by the first determination process the fuel being used is switched from the one fuel to another fuel, and a second determination process is executed for determining whether the combustion state of the engine (10) is normal or abnormal during a period in which the engine (10) is operated on the basis of the other fuel, said determination being made on the basis of the combustion parameters for that period. When it is determined by the first determination process and/or the second determination process that the operating state of the engine is abnormal, the abnormal part is identified on the basis of the determination result from the first determination process and the determination result from the second determination process.

Description

Abnormality diagnosis device for internal combustion engine

Cross-reference of related applications

The present invention is based on Japanese Application No. 2013-43373 filed on March 5, 2013 and Japanese Application No. 2013-261006 filed on December 18, 2013. Is used.

The present invention relates to an abnormality diagnosis device for an internal combustion engine, and more particularly to an abnormality diagnosis device for a combustion system of an internal combustion engine having two fuel supply units for gas fuel and liquid fuel.

An internal combustion engine that is driven by burning gaseous fuel such as compressed natural gas (CNG) has been put into practical use. In such an internal combustion engine, a fuel supply unit that supplies gaseous fuel into a cylinder of the internal combustion engine connects a gas tank that stores the gaseous fuel in a high pressure state, a fuel injection valve that injects the gaseous fuel, and the gas tank and the fuel injection valve. A pressure adjustment valve that is provided in the middle of the fuel pipe and that depressurizes the pressure of the gaseous fuel supplied from the gas tank, and a shutoff valve that is provided upstream of the pressure adjustment valve and blocks the flow of the gaseous fuel to the pressure adjustment valve And comprising. Also known is a combustion system for an internal combustion engine that includes a fuel supply unit for gaseous fuel and a fuel supply unit for liquid fuel, and switches between gaseous fuel and liquid fuel according to the operating state of the internal combustion engine, the remaining amount of fuel, and the like. It has been.

Conventionally, in a system for correcting the fuel injection amount by air-fuel ratio feedback control in which the air-fuel ratio is the target air-fuel ratio, by detecting that the correction amount (air-fuel ratio feedback correction amount) has deviated from the normal range, It has been proposed to detect such abnormalities (see, for example, Patent Document 1).

JP, 2012-172603, A As a case where the air-fuel ratio feedback correction amount is out of the normal range, there may be an abnormality in the ignition system in addition to an abnormality in the fuel system. Specifically, for example, when a part of the fuel supplied to the internal combustion engine is discharged as unburned fuel due to a shortage of ignition energy, the air-fuel ratio feedback correction is performed in accordance with the determination that the air-fuel ratio is rich. The amount is changed to the fuel reduction side. However, the technique described in Patent Document 1 only considers abnormality in the fuel system, and there is a concern that the diagnostic accuracy is lowered.

The present invention has been made to solve the above-described problem, and an abnormality has occurred in the combustion state of the internal combustion engine in the combustion system of the internal combustion engine having two fuel supply portions for gas fuel and liquid fuel. It is a main object of the present invention to provide an abnormality diagnosis device for an internal combustion engine that can identify an abnormal part.

The present invention includes a gaseous fuel supply unit that supplies gaseous fuel into a cylinder of an internal combustion engine, a liquid fuel supply unit that supplies liquid fuel into the cylinder, a combustion time of the gaseous fuel, and a combustion time of the liquid fuel. The present invention relates to an abnormality diagnosis device applied to a combustion system of an internal combustion engine, which includes an ignition device that is used in common and ignites fuel supplied into the cylinder. The abnormality diagnosis device of the present invention is based on a combustion parameter related to combustion of the internal combustion engine during the period in which the operation of the internal combustion engine is performed by combustion of one of the gaseous fuel and the liquid fuel. First determination means for determining whether the combustion state of the internal combustion engine is normal or abnormal, and fuel switching means for switching the used fuel from the one fuel to the other fuel after the determination of the combustion state by the first determination means And whether the combustion state is normal or abnormal based on the combustion parameters during the period in which the internal combustion engine is operated by combustion of the other fuel after the fuel is switched by the fuel switching means. And when the combustion state is determined to be abnormal by at least one of the second determination means, the first determination means, and the second determination means. And a abnormality identifying means for identifying the abnormal region based on the determination result by the determination result and the second determination means according to the first determination means.

In the above-described configuration, the combustion parameters acquired in each period are set in each of the period in which the operation of the internal combustion engine is performed by combustion of gaseous fuel and the period in which the operation of the internal combustion engine is performed by combustion of liquid fuel. Based on this, abnormality diagnosis for the combustion system (injection supply system and ignition system) is performed. In addition, when it is determined that there is an abnormality in the abnormality diagnosis at the time of combustion of any fuel, based on the determination result of the abnormality diagnosis when using the gaseous fuel and the determination result of the abnormality diagnosis when using the liquid fuel To identify the abnormal part. Only one of the diagnosis results cannot identify whether the currently occurring combustion abnormality is caused by a fuel supply system abnormality or an ignition system abnormality. According to the above configuration, since the diagnosis results for the two fuels are used, it is possible to identify an abnormal region that causes the combustion abnormality according to the combination of the diagnosis results.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings.
1 is an overall schematic configuration diagram of an engine combustion system. The flowchart which shows the process sequence of an abnormality diagnosis process. The flowchart which shows the process sequence of an abnormality specific process. The time chart showing the embodiment of the abnormality diagnosis at the time of abnormality of a liquid fuel supply part. The time chart showing the embodiment of the abnormality diagnosis at the time of generation | occurrence | production of ignition system abnormality. The flowchart which shows the process sequence of the abnormality specific process in 2nd Embodiment.

(First embodiment)
The first embodiment will be described below with reference to the drawings. The present embodiment is applied to a so-called bi-fuel type on-vehicle multi-cylinder engine (multi-cylinder internal combustion engine) that uses compressed natural gas (CNG) that is gaseous fuel and gasoline that is liquid fuel as combustion fuel. It is embodied as a combustion system. An overall schematic diagram of this system is shown in FIG.

An engine 10 shown in FIG. 1 is a multi-cylinder (for example, in-line three-cylinder) spark ignition engine, and an intake pipe 11 is connected to an intake port via an intake manifold 12, and an exhaust manifold is connected to an exhaust port. An exhaust pipe 14 is connected via 13. The intake pipe 11 is provided with a throttle valve 15 as air amount adjusting means. The throttle valve 15 is configured as an electronically controlled throttle valve whose opening degree is adjusted by an actuator 15a such as a DC motor. The opening (throttle opening) of the throttle valve 15 is detected by a throttle opening sensor 15b built in the actuator 15a.

The exhaust pipe 14 is provided with an exhaust sensor for detecting exhaust components and a catalyst 19 for purifying the exhaust. As the exhaust sensors, oxygen sensors 18 a and 18 b that output detection signals corresponding to the oxygen concentration in the exhaust are provided on the upstream side and the downstream side of the catalyst 19, respectively.

The intake port and the exhaust port of the engine 10 are respectively provided with an intake valve 25 and an exhaust valve 26 as engine valves for adjusting the amount of air introduced into the cylinder 16. The air-fuel mixture is introduced into the cylinder 16 by the opening operation of the intake valve 25, and the exhaust gas after combustion is discharged into the exhaust passage by the opening operation of the exhaust valve 26.

A spark plug 20 is provided in each cylinder 16 of the engine 10. A high voltage is applied to the ignition plug 20 at a desired ignition timing through an ignition circuit unit 20a including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 20, and the fuel supplied into the cylinder 16 is ignited and used for combustion. The ignition plug 20 and the ignition circuit unit 20a constitute an ignition device, and the ignition device is a common component for the combustion of gaseous fuel and the combustion of liquid fuel.

In this system, as a fuel supply unit that supplies fuel to each cylinder 16 of the engine 10, a gas fuel supply unit 40 that supplies gaseous fuel (CNG fuel) and a liquid fuel supply that supplies liquid fuel (gasoline). Part 70 is provided.

The gaseous fuel supply unit 40 includes a first injection valve 21 that injects gaseous fuel, and the gaseous fuel is supplied to the intake port of each cylinder 16 by the injection of the first injection valve 21. A gas tank 42 is connected to the first injection valve 21 via a gas pipe 41, and a pressure adjustment function for adjusting the pressure of the gaseous fuel supplied to the first injection valve 21 is reduced in the middle of the gas pipe 41. A regulator 43 is provided. The regulator 43 adjusts the pressure of a gaseous fuel in a high pressure state (for example, a maximum of 20 MPa) stored in the gas tank 42 to a mechanically determined pressure value (for example, 0.3 to 0.4 MPa). The gaseous fuel after the decompression adjustment is supplied to the first injection valve 21 through the gas pipe 41.

The fuel passage formed by the gas pipe 41 and the like further includes a tank main stop valve 44 disposed in the vicinity of the fuel outlet of the gas tank 42 and a fuel inlet of the regulator 43 that is downstream of the tank main stop valve 44. A shut-off valve 45 disposed in the vicinity is provided. These

valves

44 and 45 allow and block the flow of gaseous fuel in the gas pipe 41. Both the tank main stop valve 44 and the shutoff valve 45 are electromagnetic on-off valves, and are normally closed types that shut off the flow of gaseous fuel when not energized and allow the flow of gaseous fuel when energized.

The regulator 43 is integrally provided with a pressure sensor 46 that detects a fuel pressure before pressure reduction adjustment. A gas pipe 41 on the downstream side of the regulator 43 includes a pressure sensor 47 that detects an injection pressure, and a gas pipe 41. A temperature sensor 48 for detecting the temperature of the gaseous fuel is provided. A gaseous fuel supply unit 40 is configured by the first injection valve 21, the gas pipe 41, the gas tank 42, and the like.

The liquid fuel supply unit 70 includes a second injection valve 22 that injects liquid fuel, and the liquid fuel is supplied to the intake port of each cylinder 16 by the injection of the second injection valve 22. A fuel tank 72 is connected to the second injection valve 22 via a fuel pipe 71. The fuel pipe 71 is provided with a fuel pump 73 that feeds the liquid fuel in the fuel tank 72 to the second injection valve 22.

The control unit 80 includes a CPU, a ROM, a RAM, a backup RAM, and the like, and executes various control programs stored in the ROM, thereby performing various controls of the engine 10 according to each engine operating state. . Specifically, the control unit 80 is electrically connected to the various sensors described above and other sensors (crank angle sensor 81, intake pipe pressure sensor 82, cooling water temperature sensor 83, vehicle speed sensor, etc.) provided in the system. The outputs (detection signals) from these sensors are input. Further, the control unit 80 is electrically connected to driving units such as the ignition circuit unit 20a and the

injection valves

21 and 22, and drives each driving unit by outputting a driving signal to each driving unit. Control.

A drive signal is input from the control unit 80 to the drive unit such as the ignition circuit unit 20a and each of the

injection valves

21 and 22, and each drive unit is driven according to the input drive signal. Specifically, the ignition circuit unit 20a outputs a high voltage according to the ignition signal from the control unit 80, and causes the spark plug 20 to generate an ignition spark. The first injection valve 21 injects an amount of gaseous fuel according to the injection signal from the control unit 80 into the intake port, and the second injection valve 22 outputs an amount of liquid fuel according to the injection signal from the control unit 80. Inject into the intake port.

The control unit 80 selectively switches the fuel to be used according to the engine operating state, the fuel remaining amount in the tank, an input signal from a fuel changeover switch (not shown) operated by the driver, and the like. Specifically, when the remaining amount of gaseous fuel in the gas tank 42 falls below a predetermined value or when the use of the liquid fuel is selected by the fuel changeover switch, the liquid fuel is preferentially used. When the remaining amount of liquid fuel in the fuel tank 72 falls below a predetermined value, or when the use of gaseous fuel is selected by the fuel changeover switch, the gaseous fuel is preferentially used.

In the air-fuel ratio control of the present embodiment, feedback control based on the deviation between the actual value (actual air-fuel ratio) of the air-fuel ratio and the target value (target air-fuel ratio) is performed. Specifically, the target air-fuel ratio is calculated based on the engine operating state (for example, engine speed and engine load), and the actual air-fuel ratio is calculated based on the detection value of the oxygen sensor 18a provided on the upstream side of the catalyst 19. calculate. Then, an air-fuel ratio feedback correction amount (hereinafter also referred to as “air-fuel ratio FB amount”) is calculated according to the deviation between the actual air-fuel ratio and the target air-fuel ratio, and the basic injection amount is corrected based on the calculated air-fuel ratio FB amount. By doing so, the actual air-fuel ratio is made to coincide with the target air-fuel ratio. Here, the basic injection amount is a fuel amount necessary for obtaining the target air-fuel ratio, and is calculated based on the intake air amount detected by the intake pipe pressure sensor 82 and the target air-fuel ratio, for example. The air-fuel ratio FB amount is decreased by a predetermined amount when the air-fuel ratio detected by the oxygen sensor 18a is rich, while it is increased by a predetermined amount when it is lean. Further, when the air-fuel ratio detected by the oxygen sensor 18a is switched from rich to lean or from lean to rich, the air-fuel ratio FB amount is increased or decreased stepwise. In the air-fuel ratio feedback control of this system, the controllability of the air-fuel ratio control is enhanced by adding a correction based on the detection value of the oxygen sensor 18b on the downstream side of the catalyst.

Further, the control unit 80 performs an abnormality diagnosis as to whether or not an abnormality has occurred in the fuel supply system and the ignition system of the engine 10 based on the combustion state of the engine 10 during the period in which the engine 10 is being operated. is doing. In particular, in the present embodiment, a period during which the engine 10 is operated by the gaseous fuel injection by the first injection valve 21 and a period during which the engine 10 is operated by the liquid fuel injection by the second injection valve 22. The abnormality diagnosis based on the engine combustion state is carried out in each of the above. Then, the abnormal part is specified based on the determination results of two different fuels.

More specifically, the control unit 80 is a combustion parameter that is a parameter related to combustion of the engine 10 during a period in which the operation of the engine 10 is performed by combustion of one of the gaseous fuel and liquid fuel (fuel before switching). Get parameters. Further, it is determined whether the combustion state of the engine 10 is normal or abnormal based on the acquired combustion parameter (first determination process). After the execution of the first determination process, this time, the used fuel is switched to the other fuel (switched fuel), and the combustion parameters in a state where the operation of the engine 10 is being performed by burning the other fuel are acquired. Further, it is determined whether the combustion state of the engine 10 is normal or abnormal based on the acquired combustion parameter (second determination process). Based on the determination result of the first determination process and the result of the second determination process, whether or not there is an abnormality in the fuel supply system and the ignition system of the engine 10 is determined. It is going to be specified.

Next, the abnormality diagnosis process of the present embodiment will be described using the flowchart of FIG. This process is executed by the control unit 80 at predetermined intervals.

In step S101, it is determined whether or not the engine 10 is being operated by burning one of the gaseous fuel and the liquid fuel. When the engine operation is being performed, the process proceeds to step S102, and it is determined whether or not the use fuel has been switched. If a negative determination is made, that is, before fuel switching, the process proceeds to step S103.

In step S103, a parameter (combustion parameter) related to the combustion state of the engine 10 is acquired, and it is determined whether the combustion state of the engine 10 is normal or abnormal based on the acquired combustion parameter (first determination process). In this embodiment, the air-fuel ratio FB amount calculated by an air-fuel ratio feedback routine (not shown) is acquired as a combustion parameter, and the combustion state of the engine 10 is determined based on whether or not the acquired air-fuel ratio FB amount is within the control range. .

If the air-fuel ratio FB amount is within the control range, the process proceeds to step S104, and the first abnormality determination flag indicating the determination result of the first determination process is turned off. On the other hand, when the air-fuel ratio FB amount is out of the control range, the process proceeds to step S105, and the first abnormality determination flag is turned on. After the determination by the first determination process, the process proceeds to step S106, in which it is determined whether or not the fuel switch has been turned on (whether or not there has been a fuel switching request). If the fuel switch is ON, the process proceeds to step S107, and the fuel used for combustion of the engine 10 is switched from the pre-switching fuel that is currently in use to the post-switching fuel that is the other fuel (fuel switching means). .

If a positive determination is made in step S102, the process proceeds to step S108. In step S108, a combustion parameter under the condition where the operation of the engine 10 is performed by combustion of the fuel after switching is acquired, and it is determined whether the combustion state of the engine 10 is normal or abnormal based on the acquired combustion parameter. (Second determination process). In the second determination process, similarly to the first determination process, the air-fuel ratio FB amount is acquired as a combustion parameter, and the engine combustion state is determined based on whether or not the acquired air-fuel ratio FB amount is within the control range.

In the second determination process, when the air-fuel ratio FB amount is within the control range, the process proceeds to step S109, and the second abnormality determination flag indicating the determination result of the second determination process is turned off. On the other hand, when the air-fuel ratio FB amount is out of the control range, the process proceeds to step S110, and the second abnormality determination flag is turned on. In step S111, after a predetermined time has elapsed since the use of fuel was switched, the determination results of the first determination process and the second determination process, that is, the abnormality shown in FIG. 3 using the first abnormality determination flag and the second abnormality determination flag. Execute specific processing.

In FIG. 3, in step S201, it is determined whether or not the first abnormality determination flag is on. If it is off, the process proceeds to step S202. In step S202, it is determined whether or not the second abnormality determination flag is on. If it is off, the process proceeds to step S203, and it is determined that the fuel supply system and the ignition system of the engine 10 are normal. On the other hand, if the second abnormality determination flag is ON, the process proceeds to step S204, and the fuel supply part of the pre-switching fuel is identified as an abnormal part. For example, when the pre-switching fuel is gaseous fuel and the post-switching fuel is liquid fuel, if the normal determination is made in the first determination process and the abnormal determination is made in the second determination process, the liquid fuel supply unit 70 is identified as the abnormal part. To do. Examples of the abnormality of the liquid fuel supply unit 70 include an injection abnormality of the second injection valve 22 and a malfunction of the fuel pump 73.

On the other hand, if the first abnormality determination flag is on, the process proceeds to step S205 to determine whether or not the second abnormality determination flag is on. When the second abnormality determination flag is off, the process proceeds to step S206, and the fuel supply part of the pre-switching fuel is identified as an abnormal part. For example, when the pre-switching fuel is gaseous fuel and the post-switching fuel is liquid fuel, and abnormal determination is made in the first determination process and normal determination is made in the second determination process, the gaseous fuel supply unit 40 is identified as an abnormal part. To do. As an abnormality of the gaseous fuel supply unit 40, for example, an injection abnormality of the first injection valve 21, a failure in which the opening of the tank main stop valve 44 or the shutoff valve 45 is restricted, and the closing of these

valves

44 and 45 are restricted. A failure, a malfunction of the regulator 43, etc. are mentioned. If the second abnormality determination flag is ON in step S205, the process proceeds to step S207, and the ignition system part including the ignition circuit unit 20a and the ignition plug 20 of the engine 10 is specified as an abnormal part.

The reason for specifying an ignition system abnormality when both the first abnormality determination flag and the second abnormality determination flag are “on” is as follows. Combustion using gas fuel and liquid fuel are used when combustion abnormality is detected during combustion of one fuel and the combustion abnormality continues after switching to the other fuel. It can be determined that the combustion is not performed properly. Also, the fact that both combustion using gaseous fuel and combustion using liquid fuel are not appropriate means that there is an abnormality in the ignition system parts that are commonly used in the combustion, and the combustion of the fuel is properly performed due to the ignition system abnormality. There is a high possibility that it has not been implemented. Therefore, in the present embodiment, when both the first abnormality determination flag and the second abnormality determination flag are “on”, it is specified that the ignition system is abnormal. Note that the ignition system abnormality includes, for example, intermittent ignition, lack of ignition energy, and the like, and the cause thereof may be an energization failure of the ignition circuit unit 20a, a discharge failure of the spark plug 20, and the like.

When the determination of the presence / absence of abnormality of the fuel system and the identification of the abnormal part are completed, the process proceeds to step S208 to notify the driver that an abnormality has occurred in the engine combustion system by a lamp display or a message display. In addition to the above notification, the output of the engine 10 may be limited, the fuel supply unit may be switched to a normal fuel, and the like.

Next, a specific aspect of the abnormality diagnosis process of the present embodiment will be described using the time charts of FIGS. 4 shows a case where an abnormality has occurred in the liquid fuel supply unit 70, and FIG. 5 shows a case where an abnormality has occurred in the ignition system.

First, during the operation of the engine 10 using liquid fuel, for example, a clogging abnormality due to deposit or the like occurs in the second injection valve 22, and the amount of liquid fuel injected by the second injection valve 22 is continuously limited. Assuming that In this case, due to the amount of fuel supplied into the cylinder 16 being smaller than the command value (air-fuel ratio leaning), the air-fuel ratio FB amount is corrected to increase the fuel injection amount as shown in FIG. It is gradually changed to the increasing side (to the increasing side). Eventually, the air-fuel ratio FB amount becomes the upper limit guard value, and at time t11 after the state continues for a predetermined time, the first abnormality determination flag is switched from OFF to ON.

Thereafter, when a fuel switching command is input in accordance with the operation of the fuel switch, the liquid fuel injection by the second injection valve 22 is switched to the gaseous fuel injection by the first injection valve 21 (t12). Further, the air-fuel ratio FB amount is reset along with the fuel switching. At this time, if the gaseous fuel supply unit 40 is normal, an appropriate amount of gaseous fuel based on the command value is injected into the cylinder 16 from the first injection valve 21, and the air-fuel ratio FB amount becomes an appropriate value within the control range. The second abnormality determination flag is kept off. Further, the first abnormality determination flag and the second abnormality determination flag at the diagnosis timing t13 after a predetermined time has elapsed from the fuel switching are referred to. Then, based on the fact that the first abnormality determination flag = on and the second abnormality determination flag = off, it is specified that there is an abnormality in the combustion system, and the liquid fuel supply unit 70 is specified as an abnormal part.

Next, let us consider a case where an abnormality in the ignition system continuously occurs during the period of operation of the engine 10 using liquid fuel (for example, insufficient ignition energy). In this case, a part of the fuel supplied into the cylinder 16 is discharged into the exhaust passage without being used for combustion, so that the air-fuel ratio FB amount decreases the fuel injection amount as shown in FIG. It is gradually changed to the correcting side (decreasing side). Eventually, the air-fuel ratio FB amount becomes the lower limit guard value, and at time t21 after the state continues for a predetermined time, the first abnormality determination flag is switched from OFF to ON.

Thereafter, when a fuel switching command is input in accordance with the operation of the fuel switch, the liquid fuel injection by the second injection valve 22 is switched to the gaseous fuel injection by the first injection valve 21 (t22). Further, the air-fuel ratio FB amount is reset along with the fuel switching. If an ignition system abnormality has occurred, the abnormality is not resolved even after the injected fuel is switched, and a part of the fuel is discharged to the exhaust passage without being burned. It will stick to the value. Therefore, the second abnormality determination flag is switched from off to on. Further, at the diagnosis timing t23, the first abnormality determination flag and the second abnormality determination flag are referred to. Then, based on the fact that the first abnormality determination flag = on and the second abnormality determination flag = on, it is specified that there is an abnormality in the combustion system, and the ignition device is specified as an abnormal part.

According to the embodiment described above in detail, the following effects can be obtained.

In each of the period in which the operation of the engine 10 is performed by the combustion of the gaseous fuel and the period in which the operation of the engine 10 is performed by the combustion of the liquid fuel, the engine 10 is based on the combustion parameters acquired within each period. In addition to performing abnormality diagnosis on the injection supply system and ignition system, if it is determined that there is an abnormality in the abnormality diagnosis at the time of combustion of any fuel, the determination result of abnormality diagnosis when using gaseous fuel, The configuration is such that the abnormal part is specified based on the determination result of the abnormality diagnosis when using the fuel. According to this configuration, since the diagnosis results for the two fuels are used, the abnormal part that causes the combustion abnormality can be specified according to the combination of the diagnosis results.

Specifically, for example, when the first abnormality determination flag is on and the second abnormality determination flag is on, it can be specified that the ignition system is abnormal. Further, when the first abnormality determination flag is on and the second abnormality determination flag is off, it can be specified that there is an abnormality in the fuel supply portion of the fuel before switching. Further, when the first abnormality determination flag is off and the second abnormality determination flag is on, it can be specified that there is an abnormality in the fuel supply portion of the fuel after switching.

The combustion parameter used in the abnormality diagnosis is the air-fuel ratio FB amount, and it is configured to determine whether the combustion state of the engine 10 is normal or abnormal based on the air-fuel ratio FB amount. By adopting a configuration that diagnoses whether there is an abnormality in the combustion system based on the air-fuel ratio FB amount, it is possible to grasp the abnormality before the engine 10 becomes inoperable due to an abnormality in the fuel supply unit or the ignition system. it can.

(Second Embodiment)
Hereinafter, the second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, when it is determined that there is an abnormality in both the first determination process and the second determination process, the ignition system part including the ignition circuit unit 20a and the ignition plug 20 of the engine 10 is specified as an abnormal part. . On the other hand, in this embodiment, when it is determined that there is an abnormality in both the first determination process and the second determination process, either the ignition system part or the intake system part of the engine 10 is specified as an abnormal part. . The intake system of the engine 10 is also a component that is commonly used in engine combustion, and that both combustion using gaseous fuel and combustion using liquid fuel are not appropriate means that the intake system component that is commonly used in those combustions This is because there is an abnormality in the intake system, and it is considered that fuel combustion is not properly performed due to the abnormality in the intake system.

Here, as the intake system abnormality, for example, various components provided in the engine intake system such as the throttle valve 15, the actuator 15a, the throttle opening sensor 15b, the intake pipe pressure sensor 82, and an intake air temperature sensor (not shown) are normal. Includes abnormalities that operate in different modes.

Next, the processing procedure of the abnormality diagnosis processing of this embodiment will be described. The present embodiment is the same as the first embodiment described above in that the abnormality diagnosis process is performed according to the flowchart of FIG. The flowchart of FIG. 6 is used as the abnormality specifying process in step S111 of FIG. Below, the abnormality identification process of this embodiment is demonstrated using FIG.

In FIG. 6, in steps S301 to S305, the same processing as in steps S201 to S205 in FIG. 3 is performed. If the second abnormality determination flag is off in step S305, the process proceeds to step S306, and the fuel supply part of the pre-switching fuel is identified as an abnormal part. On the other hand, if the second abnormality determination flag is on, the process proceeds to step S307, and the common part of each fuel in the engine combustion is specified as an abnormal part. Here, an abnormality occurs in the ignition system part including the ignition circuit portion 20a and the ignition plug 20 of the engine 10 or the intake system part including the throttle valve 15, the actuator 15a, the throttle opening sensor 15b, and the intake pipe pressure sensor 82. Judge that there is. Then, this routine ends.

In the second embodiment, when it is determined that there is an abnormality in both the first determination process and the second determination process, it is determined that either an ignition system abnormality or an intake system abnormality of the engine 10 has occurred. It was. The fact that the combustion using gaseous fuel and the combustion using liquid fuel are both inappropriate is presumed to be an abnormality of the common parts used in common in the combustion. In addition to the ignition system parts, the common parts include intake system parts. Therefore, when the abnormality of the combustion state continues even when the fuel used is switched, the abnormal part is set to either the ignition system component or the intake system component.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

In the above-described embodiment, when the fuel changeover switch is operated, the fuel is switched from one fuel to the other fuel, and the second determination process is performed when the fuel is changed. Regardless of whether or not there is a configuration, the fuel used may be switched to the other fuel after the first determination process is completed, and the second determination process may be performed after the switching. In this case, before the fuel changeover switch is operated, it can be confirmed in advance whether or not there is an abnormality in the fuel supply portion of the fuel after the changeover.

In the first embodiment, when it is determined that there is a combustion abnormality of the engine 10 in both the first determination process and the second determination process, the ignition device including the ignition plug 20 and the ignition circuit unit 20a is specified as the abnormal part. . On the other hand, in this embodiment, when it is determined that there is a combustion abnormality of the engine 10 in both the first determination process and the second determination process, the ignition device has failed or the gaseous fuel supply unit 40 and the liquid fuel supply It is determined that the simultaneous failure of the unit 70 has occurred. Failures in the gas fuel supply unit 40 and the liquid fuel supply unit 70 rarely occur, and even if the gas fuel supply unit 40 and the liquid fuel supply unit 70 fail simultaneously, it can be said that it is extremely rare. In this embodiment, such a rare case is taken into consideration to prevent a diagnosis failure.

When it is determined in both the first determination process and the second determination process that there is a combustion abnormality of the engine 10, a mode of change of the combustion parameter before fuel switching and a mode of change of the combustion parameter after fuel switching are further provided. Compare. It is set as the structure which identifies an abnormal site | part based on the comparison result. When the cause of the combustion abnormality is an ignition system abnormality, the mode of change of the combustion parameter before and after the fuel switching is the same. Specifically, for example, when the air-fuel ratio FB amount is reached, the lower limit guard value is maintained during combustion of one fuel, and when the fuel is switched thereafter, the air-fuel ratio is also maintained during combustion of the other fuel. The FB amount is held at the lower limit guard value. Considering this point and adopting the above-described configuration, it is possible to further improve the accuracy of identifying an abnormal site.

In the above embodiment, the first determination process and the second determination process are each performed once, and the abnormality diagnosis is performed based on the determination results. The first determination process and the second determination process may be alternately performed a plurality of times, and an abnormality diagnosis may be performed based on the results of the plurality of times.

In the above-described embodiment, the air-fuel ratio FB amount is used as the combustion parameter, and it is configured to determine whether the combustion state of the engine 10 is normal or abnormal based on the air-fuel ratio FB amount. It is not limited to. For example, when the actual air-fuel ratio is controlled at the target air-fuel ratio by adjusting the intake air amount of the engine 10, it is determined whether the combustion state of the engine 10 is normal or abnormal based on the correction amount of the intake air amount. Also good.

In the second embodiment, when it is determined by the abnormality specifying process in FIG. 6 that an abnormality has occurred in either the ignition system component or the intake system component, an abnormality has occurred in either the ignition system component or the intake system component. You may implement the process which specifies whether it is.

As a process for specifying which of the ignition system component and the intake system component is abnormal, for example, during fuel injection of gaseous fuel or liquid fuel, the relationship between the throttle opening and the intake air amount is stored in advance. There is a method that is performed by determining whether or not it matches a certain relationship. Specifically, it is determined whether or not the intake pipe pressure detected by the intake pipe pressure sensor 82 matches the current throttle opening control amount. If the relationship between the throttle opening and the intake pipe pressure matches the relationship stored in advance, the intake system components are normal. Therefore, among the ignition system components and intake system components, the ignition system components are identified as abnormal parts. To do. On the other hand, if the relationship between the throttle opening and the intake pipe pressure does not match the relationship stored in advance, the intake system component is determined as an abnormal part.

The process of identifying which of the ignition system parts and the intake system parts is abnormal can be performed during the fuel cut. Here, the gaseous fuel has a larger volume per unit mass than the liquid fuel. Therefore, in the intake pipe pressure sensor 82, it is considered that not only the air in the intake pipe but also the gaseous fuel injected from the first injection valve 21 causes a detection error due to the influence of the injected fuel. Therefore, in the present embodiment, abnormality determination of intake system components is performed based on each sensor value during fuel cut that is not affected by gaseous fuel. Specifically, for example, the sensor value of the throttle opening and the sensor value of the intake air amount are acquired during the fuel cut, and the relationship between the throttle opening and the intake air amount matches the relationship stored in advance. A process of determining whether or not is performed. By adopting such a configuration, it is possible to identify an abnormal site with higher accuracy.

It is good also as a structure which implements the process which pinpoints which abnormality has arisen in an ignition system component or an intake system component during the injection period of a liquid fuel. In this case, it is possible to specify whether or not the abnormal part is an intake system component under a situation where the detection error of the intake pipe pressure sensor 82 is small.

In the second embodiment, when both the first determination process and the second determination process are determined to be abnormal, the abnormal part is either the ignition system part or the intake system part. Simultaneous failure may be considered. Although it can be said that an ignition system component and an intake system component fail at the same time in the engine 10 is an extremely rare case, it is possible to prevent a diagnosis omission by considering such a rare case.

In some cases, an existing gasoline engine having only a fuel injection valve for gasoline injection as a fuel injection means may be changed to a system capable of injecting two types of fuel by installing a fuel supply unit for gaseous fuel. The present invention can also be applied to such a system. Specifically, an injection pipe is connected to the tip of the first injection valve 21, and this injection pipe is provided in the intake pipe. The gaseous fuel ejected from the first injection valve 21 is injected into the intake port of the engine 10 through the injection pipe.

In the above embodiment, the gaseous fuel is CNG fuel, but other gaseous fuels that are gaseous in the standard state can also be used. For example, a configuration using a fuel mainly composed of methane, ethane, propane, butane, hydrogen, dimethyl ether, or the like. It is good. Further, liquid fuel is not limited to gasoline fuel. For example, the present invention may be applied to a configuration in which a fuel injection system for gaseous fuel is mounted on a diesel engine using light oil as a liquid fuel for combustion.

Claims

A gaseous fuel supply unit (40) for supplying gaseous fuel into the cylinder (16) of the internal combustion engine (10), a liquid fuel supply unit (70) for supplying liquid fuel into the cylinder, and at the time of combustion of the gaseous fuel And an ignition device (20a, 20) that is used in common when the liquid fuel is burned and ignites the fuel supplied into the cylinder, and is applied to a combustion system of an internal combustion engine,
In a period in which the operation of the internal combustion engine is performed by combustion of one of the gaseous fuel and the liquid fuel, the combustion state of the internal combustion engine is determined based on a combustion parameter related to combustion of the internal combustion engine in the period. First determination means for determining whether normal or abnormal;
Fuel switching means for switching the used fuel from the one fuel to the other fuel after the determination of the combustion state by the first determination means;
After the fuel is switched by the fuel switching means, it is determined whether the combustion state is normal or abnormal based on the combustion parameter during the period in which the internal combustion engine is operated by burning the other fuel. Second determining means for
Based on the determination result by the first determination means and the determination result by the second determination means when the combustion state is determined to be abnormal by at least one of the first determination means and the second determination means. An abnormality identifying means for identifying an abnormal part
An abnormality diagnosis device for an internal combustion engine, comprising:
The abnormality specifying unit determines that the ignition device is abnormal when the first determination unit determines that the combustion state is abnormal and the second determination unit determines that the combustion state is abnormal. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the abnormality diagnosis device identifies the part.
The combustion system includes an intake system device (11, 15, 15a, 15b, 82) that is commonly used during combustion of the gaseous fuel and combustion of the liquid fuel and supplies air into the cylinder.
The abnormality specifying means determines that the ignition device and the intake air when the first determination means determines that the combustion state is abnormal and the second determination means determines that the combustion state is abnormal. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein at least one of the system devices is specified as the abnormal portion.
Air amount detecting means (82) for detecting the amount of intake air of the internal combustion engine;
The intake air amount detected by the air amount detecting means during the fuel cut of the internal combustion engine when at least one of the ignition device and the intake system of the internal combustion engine is specified as the abnormal portion by the abnormality specifying means The abnormality diagnosis device for an internal combustion engine according to claim 3, wherein an abnormality is determined in the intake system of the internal combustion engine based on
The abnormality specifying unit switches the fuel switching unit when the combustion state is determined to be abnormal by the first determination unit and the combustion state is determined to be normal by the second determination unit. The abnormality diagnosis apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein a fuel supply unit of a previous fuel is specified as the abnormal part.
The abnormality specifying means switches the fuel switching means when the first determination means determines that the combustion state is normal and the second determination means determines that the combustion state is abnormal. The abnormality diagnosis device for an internal combustion engine according to any one of claims 1 to 5, wherein a fuel supply unit for a subsequent fuel is identified as the abnormal portion.