JP5459240B2 - Fault diagnosis device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine failure diagnosis device, and more particularly to an internal combustion engine failure diagnosis device for diagnosing a fuel injection valve failure.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-180171), an internal combustion engine in which two fuel injection valves are arranged for each cylinder is known. Further, Patent Document 1 discloses that the output ratio of the fluctuating air-fuel ratio sensor is changed by changing the injection ratio of the two fuel injection valves in a state where the sum of the commanded injection amounts of the two fuel injection valves is constant during steady operation or idle. A failure diagnosis device for detecting an abnormality of a fuel injection valve from a behavior is disclosed. According to such a method, it is possible to detect a failure of the fuel injection valve during steady operation or idling.

JP 2009-180171 A JP 2009-185740 A JP 2010-196556 A JP-A-2005-207407

  However, the output behavior of the air-fuel ratio sensor has low responsiveness, and the failure diagnosis device cannot maintain the accuracy of failure detection during transient operation. Further, in the failure diagnosis apparatus, as shown in FIG. 7, the injection ratios of the two fuel injection valves are changed, and it is determined which of the two injection valves is in failure by changing the output of the air-fuel ratio sensor. However, when both of the two fuel injection valves fail, the inclination is between the two solid lines as shown by the broken line in FIG. 7, and therefore only one of the failures can be determined. That is, the failure diagnosis device performs the failure detection of the fuel injection valve on the assumption that only one of the two fuel injection valves fails, and when both the fuel injection valves are in failure, There is a risk that it cannot be accurately identified.

  The present invention has been made to solve the above-described problems. In an internal combustion engine in which two fuel injection valves are arranged for each cylinder, failure detection is performed for each fuel injection valve without fixing the operating state. An object of the present invention is to provide a failure diagnosis device for an internal combustion engine capable of performing the above.

In order to achieve the above object, a first invention is a failure diagnosis apparatus for an internal combustion engine,
A first injection valve and a second injection valve for supplying fuel into the cylinder;
An in-cylinder pressure sensor for detecting a combustion pressure in the cylinder;
Total calorific value calculation means for calculating the total calorific value of the cylinder based on the combustion pressure;
An operating condition changing means capable of changing from the first operating condition to a second operating condition in which the blowing ratio of the first and second injection valves is different from the first operating condition;
The command injection amount to the first injection valve, the command injection amount to the second injection valve, the total heat generation amount calculated by the total heat generation amount calculation means, and the first injection valve in the first operating condition A variable that correlates to the actual injection amount from the second injection valve (hereinafter referred to as the first variable) and a variable that correlates to the actual injection amount from the second injection valve (hereinafter referred to as the second variable). First relational expression setting means for setting one relational expression;
The command injection amount to the first injection valve, the command injection amount to the second injection valve, the total heat generation amount calculated by the total heat generation amount calculation unit, the first variable, , Second relational expression setting means for setting a second relational expression that defines a relationship with the second variable;
Computing means for solving the first relational expression and the second relational expression simultaneously and calculating the value of the first variable and the value of the second variable;
First injection valve failure determination means for determining that the first injection valve has failed when the value of the first variable does not match a reference value in a normal cylinder;
And a second injection valve failure determination means for determining that the second injection valve has failed when the value of the second variable does not match the reference value.

The second invention is the first invention, wherein
The first injection valve is a direct injection valve that directly injects fuel into the cylinder,
The second injection valve is a port injection valve for injecting fuel into an intake port connected to the cylinder.

The third invention is the first invention, wherein
Further comprising two intake ports connected to the cylinder;
The first injection valve is a port injection valve that injects fuel into one of the two intake ports.
The second injection valve is a port injection valve that injects fuel into the other intake port of the two intake ports.

  According to the 1st thru | or 3rd invention, the failure of the 1st and 2nd injection valve can be determined separately. Therefore, even when both of the two injection valves are malfunctioning, those malfunctions can be detected. Moreover, since it is only necessary to change to two operating conditions with different blowing ratios, it is possible to detect a failure of each fuel injection valve even during transient operation without fixing the operating state.

It is a schematic block diagram for demonstrating the system configuration | structure of embodiment of this invention. It is a figure for demonstrating failure detection when the 1st injection valve of # 1 cylinder fails. It is a figure for demonstrating failure detection when both the 1st and 2nd injection valves of # 4 cylinder have failed. It is a figure for demonstrating the failure detection when the 1st injection valve of # 2 cylinder and the 2nd injection valve of # 3 cylinder fail. It is the first half flowchart of the processing routine which ECU50 performs in embodiment of this invention. It is a second half flowchart of the process routine which ECU50 performs in embodiment of this invention. In a prior art, it is a figure which shows the change of A / F by the injection ratio change in case leans abnormality has arisen.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment.
[System configuration]
FIG. 1 is a schematic configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. The engine 10 includes four cylinders, # 1 cylinder to # 4 cylinder, and one cylinder is illustrated in FIG. In the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  An ignition plug 12, a direct injection valve 14 for directly injecting fuel into the cylinder, and an in-cylinder pressure sensor (CPS) 16 for detecting the in-cylinder pressure (combustion pressure) are attached to each cylinder of the engine 10. ing. The engine 10 is also provided with a crank angle sensor 18 for detecting the rotation angle of the crankshaft (hereinafter referred to as crank angle θ) and a knock sensor 19 for detecting knocking.

  An intake passage 20 connected to each cylinder is provided in the intake system of the engine 10. An air cleaner 22 is provided at the inlet of the intake passage 20. An air flow meter 24 for detecting a flow rate of air taken into the intake passage 20 (hereinafter referred to as intake air amount GA) is attached downstream of the air cleaner 22. An electronically controlled throttle valve 26 is provided downstream of the air flow meter 24. Near the throttle valve 26, a throttle opening sensor 28 for detecting the opening of the throttle valve 26 (hereinafter referred to as the throttle opening TA) is attached. An intake pressure sensor 30 for detecting the intake pressure Pim is attached downstream of the throttle valve 26. A port injection valve 32 that injects fuel into an intake port formed at the downstream end of the intake passage 20 is attached downstream of the intake pressure sensor 30.

  The exhaust system of the engine 10 is provided with an exhaust passage 34 connected to each cylinder. A catalyst 36 is provided in the exhaust passage 34. As the catalyst 36, for example, a three-way catalyst or the like is used. The exhaust passage 34 is provided with an EGR passage 38 connected to the intake passage 20. An EGR cooler 40 is provided in the EGR passage 38. A temperature sensor 42 is provided in the vicinity of the EGR cooler 40. An EGR valve 44 is provided downstream of the EGR cooler 40.

  An ECU (Electronic Control Unit) 50 is provided in the control system of the engine 10. In the input part of the ECU 50, the in-cylinder pressure sensor 16, the crank angle sensor 18, the knock sensor 19, the air flow meter 24, the throttle opening sensor 28, the intake pressure sensor 30, the temperature sensor 42, etc. are detected. Various sensors are connected. Various actuators for controlling the operation state of the ignition plug 12, the direct injection valve 14, the throttle valve 26, the port injection valve 32, the EGR valve 44, and the like are connected to the output portion of the ECU 50.

  The ECU 50 controls the operating state of the engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above. For example, the ECU 50 sets an operation condition (target heat generation amount) based on outputs from various sensors. Then, the total of the commanded injection amounts to the direct injection valve 14 and the port injection valve 32 per stroke and the blowing ratio are set so as to satisfy this target heat generation amount. The command injection amount to each fuel injection valve is determined according to this blowing ratio. Note that the blowing ratio can be arbitrarily changed. Further, the ECU 50 can calculate the in-cylinder volume V determined by the engine speed NE and the position of the piston from the crank angle θ.

[Fault diagnosis process (process overview)]
In the above-described system, when one or both of the two fuel injection valves 14 and 32 fail, it is required that the failed fuel injection valve can be identified. Conventionally, a method for detecting a failure of one fuel injection valve during steady operation or idling has been proposed. However, it is desirable that the failure can be detected even during transient operation without fixing the operation state. It is.

  An overview of the processing of this embodiment that solves such problems will be described. In the following description, the direct injection valve 14 is referred to as a first injection valve, and the port injection valve 32 is referred to as a second injection valve. This is for convenience of explanation, and may be a reverse combination.

In order to solve the above-described problem, in the system of the present embodiment, first, in-cylinder pressures of predetermined cylinders are respectively detected in the first operating condition and the second operating condition having different blowing ratios. Total calorific values (actual calorific values) Q ₁ and Q ₂ per cycle of the cylinder under the first and second operating conditions are calculated, respectively.

In the first operating condition, the instructed injection amount to the first injector ^{_{q 1_1 [mm 3 / stroke]}} , instructed injection amount _q 1_2 of the second injection valve ^[mm 3 / stroke], the total calorific value to _{Q 1} the cylinder The relationship of Formula (1) is established between [J]. Here, the variable X is a value [J / mm ³ ] obtained by dividing the actual heat generation amount generated by the actual injection amount actually injected from the first injection valve by the command injection amount q _{1_1} to the first injection valve, The variable Y is a value [J / mm ³ ] obtained by dividing the actual heat generation amount generated by the actual injection amount injected from the second injection valve by the command injection amount q _{1_2} to the second injection valve.
q _{1 — 1} × X + Q ₁ — ₂ × Y = Q ₁ (1)

Similarly, in the second operating condition is different from winnowing ratio from the first operating condition, the instructed injection amount to the first injector q _{2_1,} instructed injection amount q _{2_2} of the second _injector, the total heat generation of the cylinder relationship of equation (2) is satisfied between the amount Q _2.
q _{2_1} × X + Q _{2_2} × Y = Q ₂ (2)

Then, equations (1) and (2) are solved as simultaneous equations to calculate X and Y. If X deviates the normal value X ₀ can be determined that the fault occurs in the first injector, if the solution Y deviates the normal value X ₀ is a fault has occurred in the second injection valve It can be judged. In the present embodiment, such a method can detect a failure of each fuel injection valve of each cylinder even during transient operation without fixing the operation state.

[Failure diagnosis processing (specific example)]
Next, a specific example of failure diagnosis processing in the present embodiment will be described. 2-4 is a figure which shows three examples from which a failure state differs. In addition, the numerical value described in FIGS. 2-4 is a value assumed for description, and is not limited to this.

(Example 1: When the first injection valve of # 1 cylinder fails)
First, a specific example of failure detection when one fuel injection valve of a certain cylinder fails will be described. FIG. 2 is a diagram for explaining failure detection when the first injection valve of the # 1 cylinder has failed. In Example 1, first, the target heat generation amount is set to 100 [J] as the first operating condition. In order to satisfy this, the total of the commanded injection amounts to the first and second injection valves per stroke is 10 [mm ³ ], the blowing ratio is 80 [%] from the first injection valve, and the second injection valve To 20%. In Example 1, since the total heat generation amount of the # 1 cylinder in the first operating condition is different from the total heat generation amount of the other cylinders, it can be determined that an abnormality has occurred in the # 1 cylinder.

Here, for the # 1 cylinder, the relational expression of 8X ₁ + 2Y ₁ = 92 is established based on the above-described equation (1). Similarly, under the second operating condition, the target heat generation amount is set to 80 [J], and the total of the commanded injection amounts to the first and second fuel injection valves is 8 [mm ³ ] to satisfy this. The dividing ratio is set to 50 [%] from the first injection valve and 50 [%] from the second injection valve. Therefore, with respect to the # 1 cylinder, the relational expression 4X ₁ + 4Y ₁ = 76 is established based on the above-described equation (2).

Then, these two relational expressions are solved simultaneously to calculate X ₁ = 9 [J / mm ³ ] and Y ₁ = 10 [J / mm ³ ]. Here, the total heat generation amount in the normal cylinders # 2 to # 4 is 100 [J], and in the normal cylinder, the command injection amount = actual injection amount, so the actual heat generation amount relative to the command injection amount in the normal cylinder. X ₀ is 10 [J / mm ³ ]. By comparing the X ₁ and X _0, the first injection valve of the first cylinder, it can be determined that only 0.9 times the instructed injection quantity not be injected. On the other hand, by comparing Y ₁ and X ₀ , it can be determined that the second injection valve of the # 1 cylinder can inject fuel according to the commanded injection amount. Therefore, the failure of the first injection valve of the # 1 cylinder can be detected. Thus, according to the present invention, it is possible to detect that one fuel injection valve of a certain cylinder has failed.

(Example 2: When the first injection valve and the second injection valve of # 4 cylinder fail)
Next, a specific example of failure detection when both fuel injection valves fail in a certain cylinder will be described. FIG. 3 is a diagram for explaining failure detection when both the first and second injection valves of the # 4 cylinder have failed. The first operating condition in Example 2, the second operating condition, X _0, the description thereof is the same as Example 1 is omitted. In Example 2, since the total heat generation amount of the # 4 cylinder in the first operating condition is different from the total heat generation amount of the other cylinders, it can be determined that an abnormality has occurred in the # 4 cylinder.

Here, regarding the # 4 cylinder, under the first operating condition, a relational expression of 8X ₄ + 2Y ₄ = 58 is established based on the above-described expression (1). Similarly, in the second operating condition, a relational expression of 4X ₄ + 4Y ₄ = 44 is established based on the above-described formula (2).

Then, these two relational expressions are solved simultaneously to calculate X ₄ = 6 [J / mm ³ ] and Y ₄ = 5 [J / mm ³ ]. By comparing the X ₄ and X _0, the first injection valve of the fourth cylinder, it can be determined that only 0.6 times the instructed injection quantity not be injected. Further, by comparing Y ₄ and X ₀ , it can be determined that the second injection valve of the # 4 cylinder can inject only 0.5 times the indicated injection amount. Therefore, the failure of both the first and second injection valves of the # 4 cylinder can be detected. Thus, according to the present invention, it is possible to detect that both fuel injection valves of a certain cylinder have failed.

(Example 3: When the first injection valve of # 2 cylinder and the second injection valve of # 3 cylinder fail)
Next, a specific example of failure detection when a fuel injection valve fails in two cylinders will be described. FIG. 4 is a diagram for explaining failure detection when the first injection valve of the # 2 cylinder and the second injection valve of the # 3 cylinder fail. The first operating condition in Example 3, the second operating condition, X _0, the description thereof is the same as Example 1 is omitted. In Example 3, the # 2 and # 3 cylinders are abnormal because the total heat value of the # 2 cylinder and the total heat value of the # 3 cylinder in the first operating condition are different from the total heat value of the other cylinders. It can be determined that it has occurred.

Here, with respect to the # 2 cylinder, under the first operating condition, the relational expression of 8X ₂ + 2Y ₂ = 60 is established based on the above-described expression (1). Similarly, in the second operating condition, a relational expression of 4X ₂ + 4Y ₂ = 60 is established based on the above-described formula (2).

These two relational expressions are solved simultaneously to calculate X ₂ = 5 [J / mm ³ ] and Y ₂ = 10 [J / mm ³ ]. By comparing the X ₂ and X _0, the first injection valve # 2 cylinder, it can be determined that only 0.5 times the instructed injection quantity not be injected. On the other hand, by comparing Y ₂ and X ₀ , it can be determined that the second injection valve of the # 2 cylinder can inject fuel according to the commanded injection amount.

Regarding # 3 cylinder, under the first operating condition, a relational expression of 8X ₃ + 2Y ₃ = 90 is established based on the above-described expression (1). Similarly, in the second operating condition, a relational expression of 4X ₃ + 4Y ₃ = 60 is established based on the above-described formula (2).

These two relational expressions are solved simultaneously to calculate X ₃ = 10 [J / mm ³ ] and Y ₃ = 5 [J / mm ³ ]. By comparing X ₃ and X ₀ , it can be determined that the first injection valve of the # 3 cylinder is injecting fuel according to the commanded injection amount. On the other hand, by comparing the Y ₃ and X _0, the second injection valve # 3 cylinder, it can be determined that only 0.5 times the instructed injection quantity not be injected.

  Therefore, a failure of the # 2 cylinder first injection valve and a failure of the # 3 cylinder second injection valve can be detected. Thus, according to the present invention, it is possible to individually detect that each fuel injection valve of each cylinder has failed by solving simultaneous equations based on the equations (1) and (2) for each cylinder. it can.

[Failure diagnosis processing (processing routine)]
Next, a processing routine for realizing the above-described failure detection will be described with reference to FIGS. FIG. 5 is a first half flowchart of a processing routine executed by the ECU 50 in order to realize the above-described failure detection. FIG. 6 is a second half flowchart of a processing routine executed by the ECU 50 in order to realize the above-described failure detection. In the routine shown in FIG. 5, first, in step S100, the total heat generation amount (actual heat generation amount) [J] per cycle is calculated for each cylinder based on the output value of the in-cylinder pressure sensor 16 provided in each cylinder. The The total heat generation amount can be calculated based on, for example, the in-cylinder pressure P (θ) and the in-cylinder volume V (θ) at the crank angle θ, an experimentally determined constant α, a specific heat ratio κ, and the like. Since the calculation method of the total calorific value is not a main part in the present invention but a known technique, the description thereof is omitted here.

  Next, in step S110, it is determined whether or not there is a variation in the total heat generation amount [J] for each cylinder. If the total calorific value for each cylinder calculated in step 100 matches, the process of this routine is terminated.

  On the other hand, if the total calorific value for each cylinder calculated in step S100 does not match, then whether or not the variation in the total calorific value for each cylinder is within the criteria of the A / F imbalance is determined. Determination is made (step S120). Specifically, the ECU 50 stores in advance a reference width of the heat generation amount related to the A / F imbalance, and the ECU 50 determines whether or not the total heat generation amount between the cylinders is larger than the reference width. To do. When the difference is equal to or smaller than the reference width, the routine is terminated.

On the other hand, if there is a difference larger than the reference width in step S120, next, an abnormal cylinder in which the heat generation amount is abnormal is specified. Further, the actual heat generation amount X ₀ [J / mm ³ ] with respect to the command injection amount of the normal cylinder is calculated (step S130). Specifically, the ECU 50 has a relationship map that defines the relationship between the sum of the commanded injection amounts to the first and second injection valves and the in-cylinder pressure (normal in-cylinder pressure) to be detected by the in-cylinder pressure sensor 16. Stored in advance. The ECU 50 acquires a normal in-cylinder pressure corresponding to the total of the commanded injection amounts under the current operating conditions from the relationship map. If the normal in-cylinder pressure and the actual in-cylinder pressure detected by the in-cylinder pressure sensor 16 are different from each other by a predetermined value or more, the cylinder is determined to be an abnormal cylinder. The actual heat generation amount X ₀ [J / mm ³ ] can be calculated by dividing the total heat generation amount (or target heat generation amount) calculated in step S100 for the normal cylinder by the sum of the commanded injection amounts. .

Next, the ECU 50 sets the operation condition as the first operation condition (for example, the current operation condition), and instructs the injection quantity q _{1_1} to the first injection valve and the instruction injection quantity q to the second injection valve in the first operation condition. and _{1_2,} calculates the gross calorific value to _{Q 1} the abnormal cylinder (step S140). As described above, the ECU 50 sets operating conditions (target heat generation amount) based on outputs from various sensors, and instructs injection to the first and second injection valves per stroke so as to satisfy the target heat generation amount. Set the total amount and blowing ratio. Instructed injection amounts q _{1_1 and} q _{1_2} under the first operating condition are determined according to the blowing ratio. The total calorific value to Q ₁ the abnormal cylinder is calculated in the same manner as step S100.

Thereafter, the ECU 50 changes the operating condition from the first operating condition to the second operating condition. The second operating condition is an operating condition having a different blowing ratio from the first operating condition. ECU50 as in step S140, the instructed injection amount _{q 2_1} of the first injection valve in the second operating condition, the instructed injection amount _{q 2_2} of the second injector, the total calorific value _{Q 2} of the abnormal cylinder Is calculated (step S150).

In step S160, the ECU 50 establishes the relational expression of the expression (1) in the first operating condition and the relational expression of the expression (2) in the second operating condition, respectively, and solves them by simultaneous. Specifically, the value [J / mm ³ ] obtained by dividing the actual heat generation amount generated by the actual injection amount actually injected from the first injection valve by the command injection amount q _{1_1} to the first injection valve is the variable X, The value [J / mm ³ ] obtained by dividing the actual heat generation amount generated by the actual injection amount actually injected from the two injection valves by the instruction injection amount q _{1 —} 2 to the second injection valve is set as the variable Y, and the instruction in the first operating condition A relational expression (1) is established between the injection amounts q _{1_1 and} q _{1_2} and the total heat generation amount Q ₁ . Similarly, a relational expression (2) is established that is established between the command injection amounts q _{2_1 and} q _{2_2} and the total heat generation amount Q ₂ in the second operating condition. X and Y are calculated by solving these relational equations as simultaneous equations. When there are a plurality of abnormal cylinders, X and Y are calculated by establishing simultaneous equations for each abnormal cylinder.

Thereafter, ECU 50, at step S170, determines whether the X and _{X 0} are consistent. If X and X ₀ are different, in particular, if there is a difference larger than a predetermined value, ECU 50 determines that the first injection valve of the cylinder is faulty (Step S180). In addition, it is determined that the higher failure level is large difference between X and X _0.

Subsequently, ECU 50, at step S190, determines whether the Y and _{X 0} are consistent. If Y and X ₀ are different, in particular, if there is a difference larger than a predetermined value, ECU 50 determines that the first injection valve of the cylinder is faulty (Step S200). In addition, it is determined that the higher failure level is large difference between the Y and X _0. Thereafter, the processing of this routine is terminated.

  As described above, according to the routines shown in FIG. 5 to FIG. 6, by solving simultaneous equations based on information on two operating conditions having different blowing ratios, each fuel injection valve of each cylinder is individually failed. Can be detected. Therefore, even when both of the two fuel injection valves 14 and 32 arranged for each cylinder are in failure, the failure diagnosis can be performed correctly. Further, since it is only necessary to have two operating conditions with different blowing ratios, it is not necessary to fix the operation state to steady operation or idle, and it is possible to diagnose a failure of the fuel injection valve even during transient operation.

By the way, in the system of Embodiment 1 described above, after specifying an abnormal cylinder, a simultaneous equation is set for the abnormal cylinder, but the present invention is not limited to this. A simultaneous equation may be established for each cylinder without specifying an abnormal cylinder. In this case, a value obtained by dividing the target heating value by the sum of the instructed injection amount and X _0.

  Moreover, in the system of Embodiment 1 mentioned above, although it is supposed that each cylinder is provided with the direct injection valve 14 and the port injection valve 32, it is good also as using two port injection valves. For example, one port injection valve may be arranged for each of two intake ports connected to a cylinder.

  Moreover, in the system of Embodiment 1 mentioned above, although it is supposed that each cylinder is provided with two fuel injection valves, it is not limited to this. For example, in the case where each cylinder is provided with three fuel injection valves, a simultaneous equation having three variables X, Y, and Z may be established under three operating conditions having different blowing ratios.

  In the first embodiment described above, the direct injection valve 14 is the “first injection valve” in the first invention, and the port injection valve 32 is the “second injection valve” in the first invention. Each corresponds.

  In addition, here, the ECU 50 executes the processes of Steps S140 to S160, whereby “total calorific value calculation means”, “operating condition change means”, and “first relational expression setting means” in the first invention. The "second relational expression setting means" and the "calculation means" execute the processing of the above steps S170 to S180, so that the "first injection valve failure determination means" in the first invention becomes the above steps S190 to S190. By executing the process of step S200, the “second injection valve failure determination means” in the first aspect of the present invention is realized.

  Further, in the first embodiment, the variable X calculated in step 160 is the “first variable” in the first invention, and the variable Y calculated in step 160 is the “first variable” in the first invention. It corresponds to “2 variables”.

DESCRIPTION OF SYMBOLS 10 Engine 12 Spark plug 14 Direct injection valve 16 In-cylinder pressure sensor 18 Crank angle sensor 20 Intake passage 22 Air cleaner 24 Air flow meter 26 Throttle valve 28 Throttle opening sensor 30 Intake pressure sensor 32 Port injection valve 34 Exhaust passage 36 Catalyst

Claims (3)

A first injection valve and a second injection valve for supplying fuel into the cylinder;
An in-cylinder pressure sensor for detecting a combustion pressure in the cylinder;
Total calorific value calculation means for calculating the total calorific value of the cylinder based on the combustion pressure;
An operating condition changing means capable of changing from the first operating condition to a second operating condition in which the blowing ratio of the first and second injection valves is different from the first operating condition;
The command injection amount to the first injection valve, the command injection amount to the second injection valve, the total heat generation amount calculated by the total heat generation amount calculation means, and the first injection valve in the first operating condition A variable that correlates to the actual injection amount from the second injection valve (hereinafter referred to as the first variable) and a variable that correlates to the actual injection amount from the second injection valve (hereinafter referred to as the second variable). First relational expression setting means for setting one relational expression;
The command injection amount to the first injection valve, the command injection amount to the second injection valve, the total heat generation amount calculated by the total heat generation amount calculation unit, the first variable, , Second relational expression setting means for setting a second relational expression that defines a relationship with the second variable;
Computing means for solving the first relational expression and the second relational expression simultaneously and calculating the value of the first variable and the value of the second variable;
First injection valve failure determination means for determining that the first injection valve has failed when the value of the first variable does not match a reference value in a normal cylinder;
Second injection valve failure determination means for determining that the second injection valve has failed when the value of the second variable does not match the reference value;
A failure diagnosis apparatus for an internal combustion engine, comprising: The first injection valve is a direct injection valve that directly injects fuel into the cylinder,
The second injection valve is a port injection valve that injects fuel into an intake port connected to the cylinder;
The failure diagnosis apparatus for an internal combustion engine according to claim 1. Further comprising two intake ports connected to the cylinder;
The first injection valve is a port injection valve that injects fuel into one of the two intake ports.
The second injection valve is a port injection valve that injects fuel into the other intake port of the two intake ports;
The failure diagnosis apparatus for an internal combustion engine according to claim 1.

Images