JP2006300012A - Intake flowmeter diagnostic system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and quickly provide a diagnostic result, by diagnosing an intake flowmeter of an internal combustion engine. <P>SOLUTION: An intake system of the internal combustion engine has the intake flowmeter for measuring an intake flow with respective plurality of intake passages by making the upstream side reach cylinders with respective cylinders after merging by a downstream side collector by branching off into a plurality of intake passages, and an intake flow control means for controlling the intake flow by changing the passage cross-sectional area with respective plurality of intake passages; and determines that there is failure in a relative value of intake flows Q1 and Q2 when a frequency Cs exceeds a predetermined frequency CsO when determined as relative value failure of exceeding an allowable determining value of 0.2 on an absolute value of a deviation Qerror of subtracting A1/A2 from the ratio Q1/Q2 of the intake flow Q1 of the first intake passage to the intake flow Q2 of the second intake passage when the ratio A1/A2 of the cross-sectional area A1 of the first intake passage to the cross-sectional area A2 of the second intake passage falls within a predetermined range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an intake flow meter in an internal combustion engine intake system having an intake flow meter for measuring each intake flow rate in a plurality of intake passages and a means for controlling the intake flow rate by changing the cross-sectional area of each passage. The present invention relates to a device for diagnosing a failure.

  Patent Document 1 discloses a technique for diagnosing the presence or absence of a failure of an intake flow meter (air flow meter) by referring to a preset estimated intake flow rate using an engine rotation speed and intake negative pressure.

Patent Document 2 discloses a technique for diagnosing a failure by detecting sticking to an upper limit voltage or a lower limit voltage due to disconnection or short circuit of an intake flow meter (air flow meter).
Japanese Patent Laid-Open No. 5-187304 Japanese Patent Laid-Open No. 11-22536

  In the failure diagnosis method of Patent Document 1, the plurality of intake passages are provided with an intake flow meter for measuring each intake flow rate and a means (throttle valve) for controlling the intake flow rate by changing the cross-sectional area of each passage. If a failure diagnosis of the intake air flow meter in the intake system of the internal combustion engine is attempted, the diagnosis accuracy is significantly deteriorated depending on the combination of the passage cross-sectional area (throttle opening) for each intake passage. In addition, if the reference map is increased for each passage cross-sectional area, enormous experimentation and storage device capacity are required, which is difficult to realize.

  On the other hand, in the failure diagnosis method disclosed in Patent Document 2, failure detection is not possible unless the measurement range of the normal intake flowmeter falls outside, and the response of determination is further delayed by averaging. If it becomes unsatisfactory or worst, it will lead to an engine stall.

  The present invention has been made paying attention to such a conventional problem, and an object thereof is to make it possible to quickly and accurately perform a failure diagnosis of an intake flow meter with a simple diagnosis method.

  In order to solve the above-described problems, the present invention provides an intake system in which an upstream side branches into a plurality of intake passages and merges at a downstream collector, then reaches a cylinder for each cylinder and measures an intake air flow rate for each of the plurality of intake passages. In an intake system of an internal combustion engine comprising a flow meter and an intake flow rate control means for controlling the intake flow rate by changing a passage cross-sectional area for each of the plurality of intake passages, a ratio of the intake flow rate for each intake passage, Compared with the ratio of the cross-sectional area of the passage for each intake passage, there is provided a relative value failure determination means for determining the presence or absence of any failure of each intake flow meter.

  With such a configuration, the intake flow rate in the intake passage is proportional to the cross-sectional area of the passage, so if all intake flow meters are normal, the ratio (relative value) of the intake flow rates measured with these intake flow meters By using the fact that it matches the ratio of the passage cross-sectional area for each intake passage, it is possible to quickly and accurately determine whether one of the intake flow meters has failed by comparing both ratios. Can do.

  FIG. 1 shows an outline of a configuration including an intake system of an internal combustion engine according to the present invention.

  A box-like collector 2 is provided in communication with the intake port of each cylinder of the V-type 6-cylinder engine 1, and two collectors of the first intake passage 3 and the second intake passage 2 are provided for each cylinder block on one end side of the collector 2. An intake passage 4 is connected.

  The first intake passage 3 and the second intake passage 4 are respectively provided with a first air cleaner 31 and a second air cleaner 41 that purify intake air from the upstream side, a first air flow meter 32 that is an intake flow meter that measures an intake flow rate, and a first air flow meter 32. 2 An air flow meter 42 and a first throttle valve 33 and a second throttle valve 43 which are intake flow rate control means for controlling the intake flow rate by changing the passage cross-sectional area are provided. The first throttle valve 33 and the second throttle valve 43 are driven by throttle actuators 34 and 44, respectively.

  Two systems of the first exhaust manifold 5 and the second exhaust manifold 6 are connected to the exhaust port of each cylinder in each cylinder block.

  A fuel injection valve 7 is provided in the intake port of each cylinder, and the fuel injection valve 7 is driven by a control signal from an engine control unit (hereinafter referred to as ECU) 7, thereby controlling the fuel injection amount. The

  Intake flow rates Q1, Q2 detected by the first air flow meter 32 and the second air flow meter 42 are input to the ECU 10.

  Further, a first throttle sensor 35 and a second throttle sensor 45 for detecting the opening degree of the first throttle valve 33 and the second throttle valve 43 are provided, and the throttle opening degrees TVO1 and TVO2 detected by these are also the ECU 10. Is input.

  In addition, a rotation speed sensor 8 for detecting the engine rotation speed Ne and an intake air temperature sensor 9 for detecting the intake air temperature T are provided, and the detected engine rotation speed Ne and the intake air temperature T are also input to the ECU 10.

  The ECU 10 calculates a target torque based on an accelerator opening detected by an accelerator opening sensor (not shown), an engine rotational speed Ne, and the like so as to obtain a target intake air flow corresponding to the target torque. While the first throttle actuator 34 and the second throttle actuator 43 are driven to control the opening degree of the first throttle valve 33 and the second throttle valve 43, the intake flow rates Q1 and Q2 and the engine rotational speed Ne are usually set. Based on this, the fuel injection amount Ti is calculated.

  Further, the ECU 10 compares the ratio Q1 / Q2 of the intake flow rates Q1 and Q2 with the ratio TVO1 / TVO2 of the throttle openings TVO1 and TVO2, and determines which of the first air flow meter 32 and the second air flow meter 42 is. A relative value failure determination for determining whether or not the engine is malfunctioning, and the intake air flow rate estimated based on the throttle opening TVO1, TVO2, the intake pressure, the atmospheric pressure, the engine rotation speed Ne, and the intake flow rates Q1, Q2 Are compared, and absolute value failure determination is performed to determine whether there is a failure in each of the first air flow meter 32 and the second air flow meter 42. Diagnosis is also performed for other sensors, and in particular, the first throttle valve 33 and the second throttle valve 43 are both normal by failure diagnosis, and the failure diagnosis of the first air flow meter 32 and the second air flow meter 42 is performed. It is a condition to do.

  When it is determined that there is a failure in the air flow meter, the fuel injection valve 7 is controlled by calculating the backup fuel injection amount based on the failure state.

  Hereinafter, various controls executed by the ECU 10 will be described.

  FIG. 2 shows a flow of the relative value failure determination.

  In step S1, the intake flow rates Q1, Q2, throttle opening TVO1, TVO2, etc. are read.

In step S2, passage sectional areas A1 and A2 of the first intake passage 3 and the second intake passage 4 are calculated based on the throttle openings TVO1 and TVO2 with reference to a map.

  In step S3, it is determined whether or not the ratio A1 / A2 of the passage cross-sectional areas A1, A2 is within a predetermined range 0.2 <A1 / A2 <5. The flow is terminated without executing the relative value failure determination, and when it is determined to be within the range, the process proceeds to step S4 and subsequent steps to execute the relative value failure determination.

  That is, since the throttle valve of the engine has variations due to factors such as deterioration and individual differences, when the cross-sectional area ratio is extremely smaller or larger than 1, it is easily affected by the variation, and the accuracy is increased. Since it may deteriorate, a limit range is provided to reduce the occurrence of erroneous determination.

  In step S4, the deviation between the ratio Q1 / Q2 of the intake flow rates Q1 and Q2 and the ratio A1 / A2 of the passage cross-sectional areas A1 and A2 is calculated as a relative value error Qerror of the flow rate measurement value as follows.

Qerror = Q1 / Q2-A1 / A2
In step S5, it is determined whether or not the absolute value of the relative value error Qerror exceeds the allowable determination value 0.2.

  That is, in the first intake passage 3 and the second intake passage 4, the front-rear pressures of the first throttle valve 33 and the second throttle valve 43 are the same (upstream is atmospheric pressure, downstream is the intake pressure in the collector). Therefore, theoretically, the flow rate ratio Q1 / Q2 expressed as the relative value of the intake flow rates of each other should match the passage cross-sectional area ratio A1 / A2. Therefore, when the deviation of these ratios exceeds a predetermined value, it can be determined that the relative value is abnormal and the flow rate measurement value of either the first air flow meter 32 or the second air flow meter 42 is abnormal.

  If it is determined that the allowable determination value 0.2 is exceeded, the process proceeds to step S6, where the count value Cs of the relative value failure determination number counter is incremented, and it is determined that the allowable determination value 0.2 or less. If so, the process proceeds to step S7 to reset the count value Cs.

  In step S8, it is determined whether or not the count value Cs has exceeded the determination count Cs0 for determining a relative value failure.

  When it is determined that the determination number Cs0 has been exceeded, the process proceeds to step S9, and the relative value failure determination between the first air flow meter 32 and the second air flow meter 42 is determined and set.

  As described above, when it is determined that the relative value has failed, it is diagnosed that one of the first air flow meter 32 and the second air flow meter 42 has failed.

  Such a relative value failure determination cannot identify which one of the first air flow meter 32 and the second air flow meter 42 is in failure, but it is a simple calculation with a small calculation error. A failure can be detected, and fail-safe processing described later can be performed promptly.

  FIG. 3 shows a flow of the absolute value failure determination.

  In step S11, the intake flow rates Q1 and Q2, the throttle openings TVO1 and TVO2, and the engine speed Ne are read.

  In step S12, passage sectional areas A1 and A2 of the first intake passage 3 and the second intake passage 4 are calculated based on the throttle openings TVO1 and TVO2 with reference to a map.

  In step S13, estimated values Qm1 and Qm2 of the intake air flow rates of the first intake passage 3 and the second intake passage 4 are calculated based on the detected values.

  FIG. 4 shows an arithmetic model system for the estimated values Qm1 and Qm2.

  In brief, the intake air flow rate (hereinafter referred to as the throttle flow rate) passing through the throttle valve is calculated as the mass flow rate based on the atmospheric pressure upstream of the throttle valve, the downstream collector internal pressure, the throttle opening, and the atmospheric temperature, and is calculated based on the engine rotational speed Ne. The volumetric flow rate that flows into the cylinder is converted into a mass flow rate (hereinafter referred to as cylinder flow rate) according to the collector internal pressure and atmospheric temperature, and the collector internal pressure that changes sequentially according to the balance between the throttle flow rate that flows into the collector and the cylinder flow rate that flows out of the collector The throttle flow rate calculated sequentially using the collector internal pressure is calculated as an estimated value of the intake flow rate.

  More specifically, the throttle flow rate (mass flow rate) Qth is calculated by the following equation.

P ₁ : Atmospheric pressure P ₂ : Collector internal pressure A: Passage cross-sectional area (throttle opening area)
R: Gas constant T ₁ : Atmospheric temperature κ: Specific heat ratio Next, the cylinder flow rate is calculated by the flow shown in FIG.

  In step S31, the engine speed Ne is read.

  In step S32, the cylinder suction volume efficiency η is set with reference to the map shown in FIG. 6 based on the engine speed Ne. The cylinder suction volume efficiency η varies depending on the inertia of the intake air according to the engine rotational speed Ne, but data obtained through experiments in advance is assigned to the map.

  In step S33, a cylinder flow rate (volume flow rate) Qcyl is calculated from the following equation based on the engine speed Ne and the cylinder suction volume efficiency η.

Qcyl = V × Ne / 120 × η (2)
V: displacement of the engine Next, the collector internal pressure P ₂ which changes sequentially is calculated by the flow of FIG.

In step S41, the intake air temperature T ₂ (= atmospheric temperature T ₁ ) is read.

In step S42, the throttle flow rate (mass flow rate) G _in (= Qth) is calculated by the above equation (1).

In step S43, a cylinder flow rate (mass flow rate) _Gout is calculated. This converted the (2) cylinder flow (volumetric flow rate) Qcyl calculated by the equation, since the air density in the collector is determined by the collector internal pressure P ₂ and the intake temperature T _2, the mass flow rate G _out as follows Is done.

G _out = P ₂ / (R · T ₂ ) · Qcyl (3)
At step S44, on the basis of the above throttle flow rate _{G in} the cylinder flow rate _{G out,} as follows, and calculates the collector internal pressure _{P 2} which changes sequentially.

  The equation of state of the gas (air) in the collector is given by

P ₂ V _c = G · R · T ₂ (4)
V _c: Collector volume G: air mass collector volume _{V c} of the collector, the intake air temperature _T 2 (= _{T 1)} When a certain amount of change [Delta] P ₂ of the collector internal pressure _{P 2,} as indicated by the following equation, the collector It is determined by the amount of change ΔG of the air mass G inside.

ΔP ₂ = ΔG · R · T ₂ / V _c (5)
Assuming that the calculation time interval is Δt, the amount of change in the internal pressure of the collector between Δt is P ₂ −P _{2 (n−1)} , and the amount of change in the air mass G in the collector is (G _in −G _out ) · Δt. expressed.

  Therefore, the following equation is established.

_{P 2 -P 2 (n-1} ) = (G in -G out) · Δt · R · T 2 / V c
→ P ₂ = P _{2 (n−1)} + (G _in −G _out ) · Δt · R · T ₂ / V _c (6)
P _{2 (n−1)} : Previously calculated value of the collector internal pressure P _{2 In} this way, the throttle flow rate (mass flow rate) G _in is calculated as the estimated value Qm of the intake flow rate while sequentially calculating and updating the collector internal pressure P _2. Can be updated. When calculating the estimated values Qm1 and Qm2 of the intake air flow rates in the first intake passage 3 and the second intake passage 4, A1 and A2 are used as the throttle opening area A in the equation (1). The atmospheric pressure P ₁ can be detected by providing an atmospheric pressure sensor, but for simplicity, standard atmospheric pressure (760 mmHg) may be used.

Incidentally, the throttle valve downstream of the collector internal pressure P ₂ at the time of starting the operation from the engine stop state is equal to the atmospheric pressure P ₁ on the upstream throttle valve, the initial value of the throttle flow rate G _in is 0. That is, initially without the flow of intake air into the collector, the collector internal pressure P ₂ is lower than the atmospheric pressure P ₁ by the cylinder flow G _out from the collector to flow out by the negative pressure producing cylinder is downstream as the negative pressure source The throttle flow rate G _in is generated by the reduced pressure difference between the collector internal pressure P ₂ and the atmospheric pressure P ₁ and starts to flow into the collector.

  Returning to FIG. 3, after calculating the estimated values Qm1 and Qm2 of the intake air flow rates in the first intake passage 3 and the second intake passage 4 in step S12 as described above, the process proceeds to step S13, where the estimated values Qm1, The error rates Q1error and Q2error of Qm2 are calculated as follows:

Q1 error = 1-Q1 / Qm1 (7)
Q2error = 1-Q2 / Qm2 (8)
In step S14, it is determined whether or not the absolute value of the error rate Q1error for the first intake passage 3 exceeds the allowable determination value 0.2.

  When it is determined that the allowable determination value 0.2 is exceeded, the process proceeds to step S15, the count value C1z of the absolute value failure determination number counter for the first air flow meter 32 is incremented, and the allowable determination value 0 is reached. When it is determined that the value is less than or equal to 2, the process proceeds to step S16 to reset the count value C1z.

  In step S17, it is determined whether or not the count value C1z has exceeded the determination count C1z0 that is determined to be an absolute value failure.

  When it is determined that the number of determination times C1z0 has been exceeded, the process proceeds to step S18 to determine and set the absolute value failure determination of the first air flow meter 32.

  The estimated value Qm2 of the intake air flow rate in the second intake passage 4 is also set in step S23 when the same processing is performed in steps S19 to S23 and the absolute value failure determination is confirmed.

  The absolute value failure determination has a larger error in the estimated value calculation than the relative value failure determination, so that the failure detection is likely to be delayed, but the air flow meter in which the failure has occurred can be determined.

  Next, backup processing (fuel injection fail-safe control) performed according to the results of the relative value failure determination and the absolute value failure determination performed as described above will be described.

  FIG. 8 shows the flow of the backup process.

  In step S51, the intake flow rates Q1, Q2 and the throttle openings TVO1, TVO2 are read.

  In step S52, passage sectional areas A1 and A2 of the first intake passage 3 and the second intake passage 4 are calculated with reference to the map based on the throttle openings TVO1 and TVO2.

  In step S53, it is determined whether either the relative value failure or the absolute value failure has been determined. When no failure has been determined, it is normal and the routine proceeds to step S54, where the intake air flow rate Q1 detected by the first air flow meter 32 and the intake air detected by the second air flow meter 42 are expressed as follows. The total intake flow rate Q is calculated by adding the flow rate Q2.

Q = Q1 + Q2 (9)
When it is determined that any failure has been confirmed, the process proceeds to step S55 to determine whether an absolute value failure has been confirmed. When the absolute value failure is not confirmed and only the relative value failure is confirmed, the process proceeds to step S56 and the following backup processing is performed.

  That is, when only the relative value failure is confirmed, either the first air flow meter 32 or the second air flow meter 42 has failed, but it is unknown which one has failed and which is normal. The intake flow rate of the air flow meter cannot be used.

  Therefore, as shown in the following equation, the total intake flow rate Q obtained by summing the intake flow rates of the first intake passage 3 and the second intake passage 4 using the estimated values Qm1 and Qm2 of the intake flow rate calculated in the absolute value failure determination. Is calculated.

Q = Qm1 + Qm2 (10)
On the other hand, when the determination in step S55 is NO, the absolute value failure has been confirmed. In this case, the process proceeds to step S57 to determine whether the relative value failure has also been confirmed, and the relative value failure has been confirmed. When there is no absolute value failure, that is, when only the absolute value failure is confirmed, the process proceeds to step S56, and the total intake flow rate Q is calculated by the above equation (10). Normally, the relative value failure with higher judgment accuracy is determined by detecting the failure first, but if the absolute value failure is determined first, the specific air flow meter is finally considered to have a failure. Without making this determination, the total intake flow rate Q is calculated using the estimated values Qm1 and Qm2 as in the case of only the relative value failure confirmation.

  If the relative value failure is also confirmed in step S57, it is finally determined that the air flow meter has failed.

  In this case, the failure air flow meter and the normal air flow meter can be identified by determining the absolute value failure, and therefore the intake air flow rate on the failure side is estimated using the intake air flow rate of the normal air flow meter.

  FIG. 9 is a control block diagram for estimating the failure-side intake flow rate at the time of the absolute value failure, and FIG. 10 is a control block diagram for calculating the total intake flow rate during normal operation and failure.

  First, in step S58, it is determined whether or not the first air flow meter 32 is malfunctioning. If so, the process proceeds to step S59, where the failure confirmation of the first air flow meter 32 is set, and the first intake air according to the following equation is set. An estimated value Q1 ′ of the intake air flow rate in the passage 3 is calculated.

Q1 '= Q2 / A2 / A1 (11)
That is, as used in the relative value failure determination, when the pressure upstream and downstream of the throttle valve is the same, the intake flow rate is proportional to the passage cross-sectional area, so the normal side intake flow rate is multiplied by the cross-sectional area ratio. Side intake flow rate can be estimated with high accuracy. Further, by setting and notifying the failure confirmation of the first air flow meter 32, the first air flow meter 32 can be repaired or replaced. The same applies to the case where failure confirmation of the second air flow meter 43 described later is set.

  Next, the routine proceeds to step S60, where the estimated value Q1 ′ of the intake air flow rate in the first intake passage 3 on the failure side is detected by the second air flow meter 42 in the second intake passage 4 on the normal side, as shown in the following equation. The total flow rate Q is calculated by adding the intake air flow rate Q2.

Q = Q1 '+ Q2 (12)
If it is determined in step S58 that the first air flow meter 32 is not faulty, the second air flow meter 42 is faulty. In this case, the process proceeds to step S58, and the failure confirmation of the second air flow meter 42 is set. At the same time, the intake air flow rate Q2 ′ of the second intake passage 4 is estimated by the following equation.

Q2 '= Q1 / A1 / A2 (13)
Next, the process proceeds to step S59, and the intake air flow rate Q1 detected by the first air flow meter 32 of the normal-side first intake passage 3 is changed to the intake air flow rate of the second intake passage 4 on the failure side as shown in the following equation. The total intake flow rate Q is calculated by adding the estimated value Q2 ′.

Q = Q1 + Q2 '... (13)
In step S63, the fuel injection amount Ti is calculated as follows based on the total intake flow rate Q, the engine rotational speed Ne, and other water temperature detected by a water temperature sensor (not shown).

Ti = k · Q / Ne · COEF + Ts
k: Constant COEF: Various correction factors set by water temperature, etc. Ts: Invalid injection pulse width set by battery voltage, etc. If only one of relative value failure or absolute value failure is confirmed after performing the above backup processing Because the fuel injection amount can be calculated based on the total intake flow rate obtained by adding the estimated value of the intake flow rate of each intake passage calculated in the absolute value failure determination process, it can be backed up quickly and Resistance is improved.

  On the other hand, when both relative value failure and absolute value failure are confirmed, the airflow meter is identified and confirmed as the final failure, so the diagnostic accuracy is improved. In this case, measurement with a normal air flow meter is also possible. Value is used to calculate the intake flow rate of the fault side intake passage with high accuracy, and the total intake flow rate with high accuracy obtained by adding the intake flow rate measured normally and the intake flow rate calculated with high accuracy Since the fuel injection amount can be calculated based on this, a highly accurate backup can be performed, and the fault tolerance is further improved.

The top view which shows the system configuration | structure of the internal combustion engine intake system which diagnoses the intake flow meter which concerns on this invention. The flowchart which shows a flow meter relative value failure determination routine. The flowchart which shows a flowmeter absolute value failure determination routine. The figure which shows the model of the intake flow rate estimation calculation at the time of the said absolute value failure determination. The flowchart of the cylinder flow calculation at the time of the said absolute value failure determination. The map which shows cylinder suction volume efficiency (eta) used at the time of the said absolute value failure determination. The flowchart which calculates the collector internal pressure at the time of the said absolute value failure determination. The flowchart which shows the backup processing routine at the time of the said flow meter failure. The control block diagram which estimates the failure side intake air flow rate at the time of the said absolute value failure. The control block diagram which calculates the total intake flow at the time of normal and failure.

Explanation of symbols

1 engine,
2 collector 3 first intake passage 4 second intake passage 7 fuel injection valve 8 rotational speed sensor 9 intake air temperature sensor 10 engine control unit (ECU)
32 First air flow meter 33 First throttle valve 34, 44 Throttle actuator 35, 45 Throttle sensor 42 Second air flow meter 43 Second throttle valve

Claims (6)

After the upstream side branches into a plurality of intake passages and merges at the downstream side collector, it reaches the cylinder for each cylinder, and an intake flow meter that measures the intake flow rate for each of the plurality of intake passages, and a passage for each of the plurality of intake passages In an intake system of an internal combustion engine comprising an intake flow rate control means for controlling an intake flow rate by changing a cross-sectional area,
Comparing the ratio of the intake flow rate for each intake passage with the ratio of the cross-sectional area for each intake passage, relative value failure determination means is provided for determining whether there is any failure in each intake flow meter. An intake air flow meter diagnostic apparatus for an internal combustion engine characterized by   Based on the engine rotational speed and the passage sectional area for each intake passage, the intake flow rate for each intake passage is estimated and calculated, and the intake flow rate measured by the intake flow meter for each intake passage is converted into the corresponding intake passage. 2. An intake flow meter for an internal combustion engine according to claim 1, further comprising an absolute value failure determination means for determining whether or not there is a failure in the intake flow meter for each intake passage as compared with the estimated intake flow rate. Diagnostic device.   A failure determination confirmation means for determining that the intake flow meter is broken when both the relative value failure determination means and the absolute value failure determination means determine that there is a failure. An intake flow meter diagnostic apparatus for an internal combustion engine according to claim 1 or 2.   When the failure is determined by the failure determination determination means, the failure-side intake passage is based on the ratio of the intake air flow rate of the normal-side intake passage measured by a normal intake flow meter and the passage cross-sectional area of the plurality of intake passages. The amount of fuel supplied to the engine is calculated based on the total intake flow rate obtained by adding the intake flow rate measurement value of the normal side intake passage and the intake flow rate calculation value of the failure side intake passage. The failure diagnosis device for an internal combustion engine intake flow meter according to claim 3.   When either of the relative value failure determination means and the absolute value failure determination means determines that the intake flow meter has failed, it is obtained by adding the intake flow rate estimated for each intake passage. The intake flow meter diagnostic apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the amount of fuel supplied to the engine is calculated based on the total intake flow rate.   6. The relative value failure determination unit does not perform failure determination when a ratio of passage cross-sectional areas controlled by the plurality of intake flow rate control units is outside a predetermined range. The intake flow meter diagnostic apparatus for an internal combustion engine according to any one of the above.

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