JP2013119803A - Failure detecting device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure detecting device of an internal combustion engine capable of accurately detecting a failure of an intake control valve, in the internal combustion engine having the intake control valve for generating an intake flow such as a swirl flow and a tumble flow in a cylinder.SOLUTION: The internal combustion engine includes a TCV 36 in an intake port for communicating with the inside of the cylinder, and controls the tumble flow generated in the cylinder by varying an opening of the TCV 36. A combustion mass rate (MFB) in a combustion stroke is arithmetically operated based on cylinder internal pressure detected by a cylinder internal pressure sensor 34, and the existence of the failure of the TCV 36 is detected based on a change characteristic to a crank angle of the MFB. Desirably, the existence of the failure of the TCV 36 is detected by whether or not the ratio between a combustion first half period up to reaching MFB 50% from a combustion start and a combustion latter half period up to combustion finish after reaching the MFB 50% is significantly changed before and after an operation command to the TCV 36.

Description

  The present invention relates to a failure detection device for an internal combustion engine, and more particularly to a device for detecting a failure of an intake control valve for generating an air flow in a cylinder.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 7-83101, an apparatus for detecting a failure of a swirl control valve (SCV) for generating a swirl flow in a cylinder is known. In this device, by comparing the combustion time from the ignition estimated from the operating state of the internal combustion engine until the in-cylinder pressure reaches the peak value with the actual combustion time detected from the detected value of the in-cylinder pressure sensor, the SCV Whether or not an open failure or a closed failure has occurred is determined.

JP-A-7-83101 JP 2011-117325 A JP 2001-20791 A JP 2006-144695 A JP 2001-20882 A

  In the above conventional technique, the failure of the SCV is determined using the combustion time from the ignition to the peak in-cylinder pressure. However, counting the combustion period from the ignition timing includes an ignition delay period that does not contribute to combustion, which contributes to a decrease in failure detection accuracy. Further, in order to accurately grasp the peak time of the in-cylinder pressure, it is necessary to subdivide sampling by the in-cylinder pressure sensor. As described above, in the conventional technique, there is still room for improvement in terms of accurately detecting a failure of an intake control valve such as SCV.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine having an intake control valve for generating an intake flow such as a swirl flow or a tumble flow in a cylinder, the failure of the intake control valve An object of the present invention is to provide a failure detection device for an internal combustion engine that can accurately detect the engine.

In order to achieve the above object, the first invention includes an air flow control valve in an intake port communicating with a cylinder, and controls an intake flow generated in the cylinder by varying an opening degree of the air flow control valve. In an internal combustion engine
An in-cylinder pressure sensor for detecting the pressure in the cylinder;
MFB calculation means for calculating a combustion mass ratio (hereinafter referred to as MFB) during the combustion stroke based on the cylinder pressure detected by the cylinder pressure sensor;
A failure detection means for detecting whether or not a failure of the airflow control valve has occurred based on a change characteristic of the MFB with respect to the crank angle;
It is characterized by having.

According to a second invention, in the first invention,
The failure detecting means detects whether or not a failure of the airflow control valve has occurred depending on whether or not a significant difference occurs in a change characteristic with respect to a crank angle of the MFB before and after an operation command to the airflow control valve. Yes.

According to a third invention, in the first or second invention,
The failure detection means includes a crank angle period from the start of combustion until reaching a predetermined MFB (hereinafter referred to as the first half period of combustion) and a crank angle period from the time at which the predetermined MFB is reached until the end of combustion (hereinafter referred to as the following). And a ratio acquisition means for acquiring a ratio with respect to the crank angle of the MFB as an index of a change characteristic with respect to the crank angle of the MFB, and detecting whether or not a failure of the airflow control valve has occurred based on the ratio Yes.

According to a fourth invention, in the third invention,
The first half period of combustion is a crank angle period from a predetermined crank angle at which the MFB is 10% or more to the predetermined MFB.

  According to the first invention, in the internal combustion engine provided with the airflow control valve, the combustion mass ratio (MFB) is calculated using the in-cylinder pressure detected by the in-cylinder pressure sensor. Here, when the airflow control valve operates normally, a change occurs in the thickness of the flame zone in the cylinder due to a change in the turbulence of the airflow, thereby changing the speed of combustion. For this reason, according to the present invention, it is possible to accurately detect a failure of the airflow control valve based on the change characteristic of the MFB.

  According to the second invention, it is possible to accurately detect the presence or absence of a failure of the airflow control valve depending on whether or not a significant change is observed in the change characteristics of the MFB before and after the operation command to the airflow control valve.

  According to the third aspect of the present invention, the airflow control valve is controlled based on the ratio between the first half period of combustion from the start of combustion until the predetermined MFB is reached and the second half period of combustion from the predetermined MFB until the end of combustion. The presence or absence of a failure is detected. When the rate of progress of combustion is high, the first half period of combustion is shorter than the second half period of combustion. For this reason, according to the present invention, it is possible to accurately detect the presence or absence of a failure of the airflow control valve based on the ratio between the first half period of combustion and the second half period of combustion.

  According to the fourth aspect of the invention, the crank angle from the crank angle at which the MFB is 10% or more to the predetermined MFB is the first half period of combustion. For this reason, according to the present invention, it is possible to specify the first half period of combustion while avoiding the vicinity of the start of combustion including an error factor such as an ignition delay, so that it is possible to effectively improve failure detection accuracy of the intake control valve. .

It is a schematic block diagram for demonstrating the system configuration | structure as Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the strength of disorder, and the thickness of a flame zone. It is a figure which shows the change characteristic of the in-cylinder pressure with respect to the crank angle in a combustion stroke. It is a figure which shows the change characteristic of heat generation amount PV ( ^{kappa) with} respect to the crank angle in a combustion stroke. It is a figure which shows the change characteristic of MFB with respect to a crank angle. It is a characteristic diagram for demonstrating the change of MFB. It is a schematic diagram for demonstrating the combustion state in the cylinder in each period in FIG. It is a characteristic diagram for demonstrating the change characteristic of MFB by the disturbance of the airflow in a cylinder. It is a schematic diagram for demonstrating the combustion state in the cylinder in each period in FIG. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

  Embodiments of the present invention will be described below 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. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining a system configuration as a first embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 is configured as a spark ignition engine using gasoline as fuel. Although FIG. 1 is a view in which one cylinder of the engine is broken along the central axis, the present invention is applied to an internal combustion engine having an arbitrary number of cylinders including a single cylinder. A piston 12 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. Further, the internal combustion engine 10 includes a cylinder head 14. A combustion chamber 16 is formed between the piston 12 and the cylinder head 14. One end of an intake passage 18 and an exhaust passage 20 communicates with the combustion chamber 16. An intake valve 22 and an exhaust valve 24 are disposed at a communication portion between the intake passage 18 and the exhaust passage 20 and the combustion chamber 16, respectively.

  An air cleaner 26 is attached to the inlet of the intake passage 18. A throttle valve 28 is disposed downstream of the air cleaner 26. The throttle valve 28 is an electronically controlled valve that is driven by a throttle motor based on the accelerator opening.

  A spark plug 30 is attached to the cylinder head 14 so as to protrude into the combustion chamber 16 from the top of the combustion chamber 16. The cylinder head 14 is provided with a fuel injection valve 32 for injecting fuel into the cylinder. Further, the cylinder head 14 incorporates an in-cylinder pressure sensor 34 for detecting the in-cylinder pressure.

  The system of the present embodiment includes a tumble control valve (TCV) 36 at the intake port portion in the intake passage 18. The TCV 36 is a butterfly valve that changes the flow passage area of the intake passage 18, and functions as an intake control valve that generates a longitudinal vortex (tumble flow) in the combustion chamber 16 by forming a drift in the intake air. To do.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 40 as shown in FIG. Various sensors such as a crank angle sensor 42 for detecting the rotational position of the crankshaft and the in-cylinder pressure sensor 34 described above are connected to the input portion of the ECU 40. Further, various actuators such as the throttle valve 28, the spark plug 30, the fuel injection valve 32, and the TCV 36 are connected to the output portion of the ECU 40. The ECU 40 controls the operating state of the internal combustion engine 10 based on various types of input information.

[Operation of Embodiment 1]
(Combustion promotion operation by TCV)
First, with reference to FIG. 2, the combustion promotion operation by the TCV 36 will be described. As described above, the TCV 36 can generate a tumble flow in the cylinder by changing the flow path area of the intake port. The tumble flow generated in the cylinder changes into a small vortex (disturbance) due to space constraints due to the compression of air. The intensity of the turbulence affects the thickness of the reaction region (flame zone) formed in the cylinder. FIG. 2 is a diagram for explaining the relationship between the strength of the disturbance and the thickness of the flame zone. As shown in this figure, when the turbulence is small, the thickness of the flame zone is thin. I understand that. Thus, by increasing the turbulence in the cylinder by operating the TCV 36, it becomes possible to form a thick flame zone and promote combustion. Thereby, for example, combustion improvement can be achieved at the time of start-up at low temperatures or idling, where deterioration of combustion is likely to occur.

(Characteristics of Embodiment 1)
Next, characteristics of the first embodiment of the present invention will be described with reference to FIGS. As described above, the TCV 36 functions as a useful actuator in that it can generate a tumble flow and promote combustion in the cylinder. For this reason, it is preferable that a failure occurring in the TCV 36 is detected early and reliably. However, a useful method for detecting a tumble flow for detecting a failure of the TCV 36 has not yet been established, and at present, an indirect method using a change in intake pipe pressure, a change in air-fuel ratio A / F, or the like is used. I have to rely on it. In this case, there is a problem that it is difficult to narrow down operation conditions for ensuring detection accuracy.

  Therefore, in the system according to the present embodiment, a change in the tumble flow corresponding to a change in the opening degree of the TCV 36 is detected using the combustion mass ratio (MFB). Here, MFB is a mass ratio of the burned fuel out of the fuel flowing into the combustion chamber 16, and is a useful parameter for grasping the combustion state in the combustion chamber 16. The MFB can be calculated by the following procedure using the in-cylinder pressure P detected by the in-cylinder pressure sensor 34.

3 shows the change characteristic of the in-cylinder pressure with respect to the crank angle during the combustion stroke, FIG. 4 shows the change characteristic of the heat generation amount ^{PVκ with} respect to the crank angle during the combustion stroke, and FIG. 5 shows the change characteristic of the MFB with respect to the crank angle. FIG. When calculating the MFB, first, as shown in FIG. 3, the in-cylinder pressure P for each crank angle is detected by the in-cylinder pressure sensor 34. Next, as shown in FIG. 4, PV ^κ that is a heat generation amount is calculated. V represents the in-cylinder volume in the combustion chamber 16, and κ represents the specific heat ratio. The in-cylinder volume V is uniquely determined according to the crank angle, and the relationship between the two is stored in advance in the ECU 40 as map data or a function expression. Further, since the specific heat ratio κ is substantially constant (about 1.32) in the stoichiometric gasoline mixture, it is assumed that this value is also stored in the ECU 40 in advance. Next, the MFB for each crank angle is calculated using the following equation (1). In the following equation (1), PV ^κ _s represents the PV ^κ value at the combustion start point, PV ^κ _e represents the PV ^κ value at the combustion end point, and PV ^κ _θ represents the PV ^κ value at the crank angle θ. Show. As shown in FIG. 5, the MFB calculated by such calculation is 0% at the start point of the combustion stroke of normal combustion and 100% at the end point of the combustion stroke.
^{MFB (%) = (PV κ} θ -PV κ s) / (PV κ e -PV κ s) × 100 ··· (1)

  Here, the combustion state in the combustion chamber 16 changes as the MFB progresses. FIG. 6 is a characteristic diagram for explaining the change in MFB, and FIG. 7 is a schematic diagram for explaining the in-cylinder combustion state in each period in FIG. Combustion in the cylinder originally proceeds in a spherical shape from the ignition part, but in each figure shown in FIG. 7, combustion is linearly performed from the left end ignition part to the right end cylinder inner wall surface. The state of progress will be schematically shown.

  As shown in these figures, first, in the period A from the start of combustion to the middle of the first half period of combustion, a flame zone is formed due to turbulence in the cylinder due to the tumble flow. Thereby, MFB rises gradually. In the period B from the first half period of combustion to the second half period of combustion, the flame zone proceeds in the unburned gas, and the MFB increases linearly. In the period C from the middle of the second half of the combustion period to the end of the combustion, the flame zone reaches the wall surface and gradually disappears. For this reason, the MFB during this period gradually increases gradually and reaches 100%.

  Thus, the change characteristics of the MFB during the combustion stroke are closely related to the state of the flame zone formed in the cylinder. For this reason, when the TCV 36 is operated to change the turbulence of the air flow in the cylinder due to the tumble flow, the MFB exhibits different change characteristics due to the change in the thickness of the flame zone in the cylinder. FIG. 8 is a characteristic diagram for explaining the change characteristics of the MFB due to the turbulence of the airflow in the cylinder, and FIG. 9 is a schematic diagram for explaining the combustion state in the cylinder in each period in FIG. . In addition, in each figure shown in FIG. 8, like the figure shown in FIG. 7 mentioned above, it shall show typically a mode that combustion advances linearly from the ignition part of a left end toward the cylinder inner wall face of a right end. .

  As shown in FIGS. 8 and 9, it can be seen that during the first half of the combustion period from the start of combustion in the cylinder until the MFB reaches 50%, the greater the turbulence in the cylinder, the faster the combustion progresses. On the other hand, in the latter half of the combustion period from when the MFB reaches 50% until the combustion is completed, the flame zone reaches the wall surface first as the turbulence in the cylinder increases, but the MFB rises because the flame zone is thick Will be slower. For this reason, the faster the combustion progress rate, the shorter the first half period of combustion becomes compared to the second half period of combustion. Therefore, if the ratio between the first half period of combustion and the second half period of combustion is compared, whether or not the turbulence of the airflow in the cylinder has changed, in other words, whether the generation degree of the tumble flow has been changed by the operation of the TCV 36. It is possible to determine whether or not.

  Therefore, in the system of the present embodiment, before and after the operation command to the TCV 36, the ratio between the first half period of combustion and the second half period of combustion is calculated, and a failure occurs in the TCV 36 depending on whether or not there is a significant difference between them. It is determined whether or not it has occurred. Thereby, since the change of the tumble flow in the cylinder can be detected effectively, the failure occurring in the TCV 36 can be detected early and accurately.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 10, the specific content of the process performed in this Embodiment is demonstrated. FIG. 10 is a flowchart of a routine in which the ECU 40 detects the presence / absence of a failure in the TCV 36. Note that the routine shown in FIG. 10 is repeatedly executed during operation of the internal combustion engine 10.

  In the routine shown in FIG. 10, it is first determined whether or not the failure detection mode is ON (step 100). Here, specifically, it is determined whether or not a predetermined constant NE condition (for example, during idling) is satisfied. As a result, when the failure detection mode is not ON, it is determined that stable failure detection cannot be performed, and this routine is immediately terminated.

  On the other hand, if the failure detection mode is ON in step 100, the process proceeds to a specific process for detecting the failure of the TCV 36. First, the cylinder pressure is detected using the cylinder pressure sensor 34 ( Step 104). Next, the MFB during the combustion stroke is calculated using the above equation (1) (step 104). Next, the first combustion period a is calculated (step 106). Specifically, the crank angle period from when the MFB starts to increase from 0% to 50% is specified as the “first combustion period a”. Next, the combustion second half period b is calculated (step 108). Here, specifically, the crank angle period from when the MFB exceeds 50% until it reaches 100% is specified as the “combustion second half period b”. Then, the pre-combustion second half ratio (b / a) is calculated using the first combustion period a and the first combustion period b calculated in steps 106 and 108 (step 110).

  Next, the TCV 36 is driven (step 112). Specifically, a command is issued to change the opening of the TCV 36 in order to change the turbulence (tumble flow) generated in the cylinder. Next, the in-cylinder pressure is detected again using the in-cylinder pressure sensor 34 (step 114). Next, the MFB during the combustion stroke is calculated (step 116). Here, specifically, the same processing as in step 104 is executed. Next, the combustion first half period c is calculated (step 118). Specifically, the crank angle period from when the MFB starts to increase from 0% to 50% is specified as the “first combustion period c”. Next, a combustion second half period d is calculated (step 120). Here, specifically, the crank angle period from when the MFB exceeds 50% until it reaches 100% is specified as the “combustion second half period d”. Then, the pre-combustion second half ratio (d / c) is calculated using the first combustion period c and the first combustion period d calculated in steps 118 and 120 (step 122).

  In the routine shown in FIG. 10, it is next determined whether or not the pre-combustion second half ratio (b / a) = the pre-combustion second half ratio (d / c) is satisfied (step 124). As a result, when the establishment of (b / a) = (d / c) is not recognized, it is determined that the turbulence has changed due to the normal driving of the TCV 36, and this routine is immediately terminated. On the other hand, if the establishment of (b / a) = (d / c) is recognized in step 124, it is determined that the TCV 36 is not driven due to a failure, and the process proceeds to the next step. It is notified that a failure has occurred (step 126), and then this routine ends.

  As described above, according to the system of the present embodiment, it is possible to determine whether or not the TCV 36 is normally driven based on the change in the MFB. Thereby, the failure of the TCV 36 can be detected early and accurately.

  By the way, in the system of the embodiment of the present invention described above, the failure of the TCV 36 that generates the tumble flow is detected, but the intake control valve capable of detecting the failure is not limited to this. That is, in the case of a control valve that generates turbulence in the in-cylinder airflow, for example, in an internal combustion engine having a swirl control valve (SCV) that generates a swirl flow, the system of the present invention is used to detect a failure of the SCV. You may apply.

  In the system according to the above-described embodiment of the present invention, the crank angle period from when MFB starts to rise from 0% to 50% is used as the first half period of combustion. For example, the crank angle period from the crank angle at which the MFB is 10% or later to the MFB 50% may be set as the first half period of combustion, avoiding the vicinity at the start of combustion where error factors are likely to be superimposed. Thereby, the failure detection accuracy of the TCV 36 can be effectively improved.

  In the system of the embodiment of the present invention described above, the crank angle at which the MFB is 50% is set as the boundary between the first half period of combustion and the second half period of combustion. It may be a boundary.

  In the system according to the embodiment of the present invention described above, the ratio between the first half period of combustion and the second half period of combustion is used as a judgment value used for failure detection judgment of the TCV 36. However, the change in MFB before and after the drive command of the TCV 36 If it can be determined whether or not a significant change has occurred in the characteristics, for example, it may be determined by comparing the first half period of combustion before and after the drive command of the TCV 36.

  Further, in the system according to the embodiment of the present invention described above, the failure detection of the TCV 36 is performed based on the change in the ratio between the first half period of combustion and the second half period of combustion before and after the TCV 36 is driven. It is not necessary to compare the ratio before and after the command. For example, a normal MFB characteristic under a predetermined operating condition including the opening degree of the TCV 36 is stored, and the failure of the TCV 36 is compared with the characteristic of the detected value of the MFB under the same condition. May be detected.

  In the first embodiment described above, the TSV 36 corresponds to the “intake control valve” in the first invention, and the ECU 40 executes the processes of steps 102 to 104 and 114 to 116 described above. The “MFB calculating means” in the first invention executes the process of step 124, thereby realizing the “failure detecting means” in the first invention.

  Further, in the first embodiment described above, the “failure detection means” in the second aspect of the present invention is realized by the ECU 40 executing the process of step 124.

  In the first embodiment described above, the ECU 40 executes the processes of steps 106 to 110 and 118 to 120, so that the “ratio acquisition means” in the third aspect of the invention performs the process of step 124. By executing this, the “failure detection means” in the third aspect of the present invention is realized.

10 Internal combustion engine
12 Piston 14 Cylinder head 16 Combustion chamber 18 Intake passage 20 Exhaust passage 22 Intake valve 24 Exhaust valve 26 Air cleaner 28 Throttle valve 30 Spark plug 32 Fuel injection valve 34 In-cylinder pressure sensor 36 TCV (tumble control valve)
40 ECU (Electronic Control Unit)
42 Crank angle sensor κ Specific heat ratio

Claims (4)

In an internal combustion engine that includes an airflow control valve in an intake port that communicates with the cylinder, and controls the intake flow generated in the cylinder by varying the opening of the airflow control valve.
An in-cylinder pressure sensor for detecting the pressure in the cylinder;
MFB calculation means for calculating a combustion mass ratio (hereinafter referred to as MFB) during the combustion stroke based on the cylinder pressure detected by the cylinder pressure sensor;
A failure detection means for detecting whether or not a failure of the airflow control valve has occurred based on a change characteristic of the MFB with respect to the crank angle;
A failure detection apparatus for an internal combustion engine, comprising:   The failure detection means detects whether or not a failure of the airflow control valve has occurred depending on whether or not a significant difference occurs in a change characteristic with respect to a crank angle of the MFB before and after an operation command to the airflow control valve. The failure detection device for an internal combustion engine according to claim 1.   The failure detection means includes a crank angle period from the start of combustion until reaching a predetermined MFB (hereinafter referred to as the first half period of combustion) and a crank angle period from the time at which the predetermined MFB is reached until the end of combustion (hereinafter referred to as the following). And a ratio acquisition means for acquiring a ratio with respect to the crank angle of the MFB as an index of change characteristics with respect to the crank angle of the MFB, and detecting whether or not a failure of the airflow control valve has occurred based on the ratio The failure detection apparatus for an internal combustion engine according to claim 1 or 2.   4. The internal combustion engine failure detection apparatus according to claim 3, wherein the first half period of combustion is a crank angle period from a predetermined crank angle at which MFB reaches 10% or more to the predetermined MFB.

Images