JP2011202541A - Control device of internal combustion engine - Google Patents

Abstract

An object of the present invention is to ensure the accuracy of misfire detection even when the opening timing of an intake valve is retarded, when intake valve slow opening control and misfire detection control are used together.
An ECU detects misfire of each cylinder based on a rotational fluctuation amount ΔNe of a crankshaft detected in a predetermined misfire detection section. Further, the ECU 50 executes intake valve delay opening control for retarding the valve opening timing (IVO) of the intake valve 34 as necessary. Further, the ECU 50 changes the ignition retard guard aopg of the one cylinder to the advance side when the IVO of the other cylinder is located near the boundary of the misfire detection section of any one cylinder, Correct the timing aop to the advance side. When the ignition timing is advanced, the rotational fluctuation amount ΔNe in the normal combustion state is reduced, and the misfire detection margin is improved. Therefore, even if the IVO of other cylinders varies within and outside the misfire detection section. , Misfire detection can be performed stably.
[Selection] Figure 3

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine configured to use intake valve retarded opening control and misfire detection control in combination.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 5-52707) and Patent Document 2 (Japanese Patent Laid-Open No. 2007-192081), misfire detection control is performed based on the rotational fluctuation of the crankshaft. A control device configured to perform is known. In the misfire detection control, the time required for the crankshaft to rotate from the start point to the end point of a predetermined crank angle range (misfire detection section) is measured, and the rotation fluctuation amount of the crankshaft is detected based on this time.

  Here, the misfire detection section is set as a predetermined crank angle range (for example, a range of TDC to ATDC 30 ° CA) in which rotation fluctuation due to misfire is easily detected. When a misfire occurs in any of the cylinders, the rotational speed of the crankshaft is reduced by that amount, so that misfire detection can be performed based on the rotation fluctuation amount.

  On the other hand, as another conventional technique, for example, as disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2002-242713), the valve opening timing (IVO) of the intake valve is retarded according to the operating state of the internal combustion engine. A control device configured to execute intake valve slow-opening control is also known. According to the intake valve slow opening control, the intake flow velocity can be increased and the combustibility can be improved.

JP-A-5-52707 JP 2007-192081 A JP 2002-242713 A JP 2003-83123 A Japanese Patent Laid-Open No. 11-107838 JP 2008-115804 A JP 2006-114695 A Japanese Patent Laid-Open No. 11-82003

  By the way, in the prior art, the above-described misfire detection control and intake valve slow opening control may be used in combination. However, when these controls are used in combination, there is a problem that the accuracy of misfire detection is lowered depending on the opening timing of the intake valve. Hereinafter, this problem will be described. First, when the intake valve delay opening control is executed, the negative pressure in the combustion chamber increases between the time when the intake top dead center is passed and the time when the intake valve opens, and a relatively large pump loss occurs. This pump loss rapidly decreases when the intake valve opens, and at this time, the engine friction changes suddenly. Therefore, when the intake valve slow opening control is executed, rotation fluctuation is likely to occur at the opening timing of the intake valve.

  On the other hand, since there are mechanical errors and response delays in the valve drive system, even if the target valve opening timing of the intake valve is constant, the actual valve opening timing varies to some extent. For this reason, when the target valve opening timing of another cylinder is set in the vicinity of the boundary (for example, ATDC 30 ° CA) of a certain cylinder, the actual valve opening timing overlaps with the misfire detection interval. There is a possibility that a state that does not overlap and a state that does not overlap appear at random. In this case, the timing of occurrence of rotational fluctuations due to the opening of the intake valve varies across the boundary of the misfire detection section, so that an error occurs in the measured value of rotational fluctuation, and misfire is accurately detected. Cannot be detected.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately detect misfire of each cylinder even when the opening timing of the intake valve is retarded. Another object of the present invention is to provide a control device for an internal combustion engine that can smoothly use intake valve slow opening control and misfire detection control together.

A first aspect of the present invention is a valve timing variable means capable of variably setting the opening timing of the intake valves for the intake valves respectively provided in the plurality of cylinders of the internal combustion engine.
An intake valve delay opening control means for retarding the valve opening timing of the intake valve by the valve timing variable means when the internal combustion engine is in a predetermined operation state;
Misfire detection means for measuring the time required for the crankshaft of the internal combustion engine to rotate from the start point to the end point of the misfire detection section within a predetermined crank angle range, and for detecting misfire in the plurality of cylinders based on the time, ,
In any one of the plurality of cylinders, when the opening timing of the intake valve of another cylinder is positioned near the boundary of the misfire detection section of the one cylinder, the ignition timing of the one cylinder is set. Ignition timing adjusting means for adjusting within a range in which the accuracy of misfire detection is ensured;
It is characterized by providing.

The second invention includes ignition timing retardation limiting means for limiting the amount of retardation of the ignition timing with a retardation limitation value,
The ignition timing adjustment means sets the retard limit value of the one cylinder to a normal limit when the valve opening timing of the intake valve of the other cylinder is located near the boundary of the misfire detection section of the one cylinder. The normal limit value is a delay angle when the valve opening timing of the intake valve of the other cylinder is not located near the boundary of the misfire detection section of the one cylinder. The configuration is a limit value.

According to a third aspect of the invention, there is provided a retard limit value variable means for changing the retard limit value of the one cylinder to the retard side as the retard amount of the opening timing of the intake valve in the one cylinder is larger. ,
The ignition timing delay angle limiting means is configured to reflect the change result by both the ignition timing adjusting means and the retard angle limit value varying means in the delay angle limit value.

A fourth aspect of the invention relates to a warm-up state detecting means for detecting a warm-up state of the internal combustion engine,
When the internal combustion engine is detected to be in an unwarmed state by the warm-up state detecting means, an unwarmed-up advance means for changing the retard limit value to an advance side;
It is set as the structure provided with.

5th invention, the alcohol concentration detection means which detects the alcohol concentration in fuel,
An alcohol fuel retarding means for changing the retard limit value to the retard side as the alcohol concentration is higher;
It is set as the structure provided with.

A sixth aspect of the invention relates to an advance angle request determining means for determining whether or not an advance angle request for ignition timing has occurred,
Intake valve alternative retard control means for retarding the opening timing of the intake valve instead of advancing the ignition timing when it is determined by the advance angle request judging means that an ignition timing advance request has been made When,
It is set as the structure provided with.

  According to the first aspect of the present invention, the ignition timing adjusting means is configured such that, in any one of the cylinders, when the valve opening timing (IVO) of the intake valve of the other cylinder is set in the vicinity of the boundary of the misfire detection section. The ignition timing of each cylinder can be adjusted within a range in which the accuracy of misfire detection is ensured. With this adjustment, for example, when the ignition timing is advanced, the amount of fluctuation in the crankshaft rotation in a normal combustion state is small, so even if the IVO of other cylinders varies outside and outside the misfire detection interval, Misfire detection can be performed stably. Therefore, even when the IVO is retarded by, for example, retarded opening control of the intake valve, misfire of each cylinder can be detected accurately, and both intake valve control and ensuring misfire detection accuracy can be achieved.

  According to the second invention, the ignition timing adjusting means can change the retard limit value of the one cylinder to the advance side than usual. Therefore, it is possible to advance the ignition timing within a range in which the accuracy of misfire detection is ensured by using the retard limit value.

  According to the third invention, the retard limit value varying means delays the ignition timing according to the IVO within a range in which the misfire detection accuracy is sufficiently ensured when the IVO of the other cylinder does not affect the misfire detection accuracy. Therefore, it is possible to achieve both warming-up of the catalyst and ensuring misfire detection accuracy. Further, the ignition timing retardation limiting means can advance the ignition timing and sufficiently ensure the misfire detection accuracy when the IVO of the other cylinder is set near the boundary of the misfire detection section. Therefore, it is possible to smoothly control the intake valve and warm up the catalyst while accurately detecting misfire of each cylinder.

  According to the fourth aspect of the invention, the unwarmed-up advance means can advance the ignition timing using the retard limit value when it is detected that the internal combustion engine is in the unwarmed state. The combustion state can be stabilized. In addition, after the warm-up is completed, the function of the non-warm-up advance means stops, so that the ignition timing can be retarded and the catalyst warm-up efficiency can be increased.

  According to the fifth aspect, the retarding means for alcohol fuel can retard the ignition timing by utilizing the fact that the combustion state becomes better as the alcohol concentration in the fuel is higher. Thereby, improvement of a combustion state and warming up of a catalyst can be made compatible using the characteristic of alcohol fuel with high volatility at high temperature.

  According to the sixth aspect of the present invention, when the IVO is retarded, the intake air flow rate is increased and the combustion state is improved, so that the ignition timing can be retarded by that amount. Therefore, the intake valve alternative retard angle control means can satisfy the advance angle request by retarding the IVO even if the actual ignition timing is not advanced when the advance timing of the ignition timing is generated. It is possible to achieve both improvement of the combustion state and warm-up of the catalyst.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the retard amount of ignition timing, a misfire detection margin, and exhaust temperature. FIG. 6 is a characteristic diagram for determining ignition retard guard based on the opening timing of the intake valve. It is a characteristic diagram for determining a guard reference value based on the IVO of its own cylinder. It is a characteristic diagram for determining an advance correction value based on IVO of other cylinders. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. FIG. 6 is a characteristic diagram for determining a first ignition retard guard based on IVO. FIG. 6 is a characteristic diagram for determining a second ignition retard guard based on an integrated air amount after startup. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 3 of this invention, it is a characteristic diagram for deciding an ignition retard guard and an ignition retard reduction guard based on IVO. In Embodiment 3 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 4 of this invention, it is a characteristic diagram for determining warm-up determination air amount based on the water temperature at the time of starting. FIG. 6 is a characteristic diagram for determining ignition retard guard based on alcohol concentration in fuel and IVO. In Embodiment 4 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes an internal combustion engine 10 composed of a multi-cylinder engine. FIG. 1 illustrates one cylinder among a plurality of cylinders mounted on the internal combustion engine 10. Each cylinder 12 of the internal combustion engine 10 is provided with a combustion chamber 16 that expands and contracts by reciprocating movement of the piston 14. The piston 14 is connected to a crankshaft 18 that is an output shaft of the internal combustion engine 10.

  The internal combustion engine 10 also includes an intake passage 20 that sucks intake air into each cylinder 12 and an exhaust passage 22 that discharges exhaust gas from each cylinder 12. The intake passage 20 is provided with an air flow sensor 24 for detecting the intake air amount and an electronically controlled throttle valve 26. The throttle valve 26 is driven by a throttle motor 28 based on the accelerator opening and the like to increase or decrease the intake air amount. In each cylinder 12, a fuel injection valve 30 for injecting fuel into the intake port, an ignition plug 32 for igniting an air-fuel mixture in the combustion chamber 16, and an intake passage 20 are opened and closed with respect to the combustion chamber 16. An intake valve 34 and an exhaust valve 36 that opens and closes the exhaust passage 22 with respect to the combustion chamber 16 are provided.

  The internal combustion engine 10 also includes a VVT (Variable Valve Timing system) 38 as valve timing variable means for variably setting the phase angle of the intake valve 34. The VVT 38 has a known configuration as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-87769. Specifically, first, a cam pulley (not shown) that drives the intake valve 34 is provided with a timing pulley, and this timing pulley is connected to the crankshaft 18 via a timing chain. Therefore, when the rotation of the crankshaft 18 is transmitted to the camshaft via the timing chain and the timing pulley, the intake valve 34 opens and closes at a predetermined timing corresponding to the rotation angle of the camshaft. On the other hand, the VVT 38 includes an actuator that relatively rotates the camshaft and the timing pulley, and the valve opening timing and the valve closing timing of the intake valve 34 of each cylinder can be variably set according to the relative rotation angle between them. it can. In addition, as a valve timing variable means, it is good also as a structure using variable valve mechanism as described in Unexamined-Japanese-Patent No. 2007-132326, for example instead of the above-mentioned VVT38. In this variable valve mechanism, for example, when the intake valve 34 is driven, the two cams are used properly, so that the valve opening timing can be set variably together with the valve operating angle.

  Furthermore, the system of the present embodiment includes a sensor system including a crank angle sensor 40, a water temperature sensor 42, an alcohol concentration sensor 44, and the like, and an ECU (Electronic Control Unit) 50 for controlling the operating state of the internal combustion engine 10. I have. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 18, and the ECU 50 can detect the engine speed and the crank angle based on this output. The water temperature sensor 42 detects the cooling water temperature of the internal combustion engine. On the other hand, the alcohol concentration sensor 44 detects the alcohol concentration in the fuel when alcohol fuel is used as the fuel for the internal combustion engine 10, and constitutes an alcohol concentration detection means.

  The sensor system includes various sensors necessary for controlling the vehicle and the internal combustion engine (for example, an accelerator opening sensor that detects an accelerator opening, an air-fuel ratio that detects an exhaust air-fuel ratio, in addition to the sensors 24 and 40 to 44 described above. Sensor, a cam angle sensor for detecting the rotation angle of the camshaft, and the like), and these sensors are connected to the input side of the ECU 50. Various actuators including the throttle motor 28, the fuel injection valve 30, the spark plug 32, the actuator of the VVT 38, and the like are connected to the output side of the ECU 50.

  Then, the ECU 50 detects the state of the internal combustion engine using a sensor system, and performs operation control by driving each actuator based on the detection result. Specifically, the engine speed and crank angle are detected based on the output of the crank angle sensor 40, and the load factor of the internal combustion engine is determined based on the intake air amount detected by the air flow sensor 24 and the engine speed. calculate. Further, the fuel injection timing, ignition timing, etc. are determined based on the detected value of the crank angle. Then, the fuel injection amount is calculated based on the intake air amount, the load factor, etc., and the fuel injection valve 30 is driven and the spark plug 32 is driven. Further, the control of the ECU 50 includes intake valve slow opening control and misfire detection control described below.

(Intake valve slow opening control)
This control delays the valve opening timing of the intake valve 34 by the VVT 38 when a predetermined operating state such as a low temperature start, for example, is described in, for example, JP-A-2002-242713. This is a known control. According to this control, the target valve opening timing of the intake valve 34 is set to a crank angle of about TDC to ATDC 30 ° CA, for example, and is delayed from a normal valve opening timing (for example, BTDC 10 ° CA). As a result, the intake valve 34 is opened after the intake top dead center, so that the negative pressure in the combustion chamber 16 is increased and the flow rate of intake air flowing from the intake port into the combustion chamber (intake flow velocity). ) Can be increased. Therefore, a favorable air-fuel mixture can be formed even at low temperatures, and the combustibility can be improved.

(Misfire detection control)
This control detects the misfire of each cylinder by utilizing the rotation fluctuation of the crankshaft 18, and is a known control as described in, for example, Japanese Patent Application Laid-Open No. 2007-192081. The misfire detection control described below is an example used in a four-cylinder engine, for example, and does not limit the present invention. In general, when a misfire occurs in any cylinder during operation of the internal combustion engine, the rotational speed of the crankshaft is reduced, so that the time required for the crankshaft to rotate by a predetermined angle becomes longer. Therefore, in the misfire detection control, the time required for the crankshaft to rotate from the start point to the end point of the misfire detection section is measured in a preset crank angle range (hereinafter referred to as the first and second misfire detection sections). To do. This measurement process is executed using the output of the crank angle sensor 40 and the timer function of the ECU 50.

  Here, the first misfire detection section is based on the TDC (intake top dead center) of each cylinder, for example, in the range of 0 ° to 30 ° crank angle (CA) on the retard side, that is, TDC to ATDC 30 ° CA. Is set in the range. Further, the second misfire detection section is set in a range of, for example, ATDC 90 ° to 120 ° CA. These misfire detection sections correspond to a section in which the rotation speed of the crankshaft is minimized and a section in which the rotation speed of the crankshaft is maximized each time ignition is performed in each cylinder. That is, in the first process, the time T1 required for the crankshaft to rotate from the start point (TDC) of the first misfire detection section to the end point (ATDC 30 ° CA) and the start point (ATDC 90 ° of the second misfire detection section). The time T2 required to rotate from CA) to the end point (ATDC 120 ° CA) is measured.

  The time measurement process described above is also executed in other cylinders whose phases are shifted by 360 ° CA with respect to the cylinders to be measured at times T1 and T2. In these cylinders, times T3 and T4 required to rotate the first and second misfire detection sections are measured. That is, the times T3 and T4 are measured by the same method as the times T1 and T2 in the crank angle range shifted by 360 ° CA from the times T1 and T2. In the next process, based on these times T1 to T4, the rotational fluctuation amount ΔNe is calculated by the following equation (1).

ΔNe = (T4−T3) − (T2−T1) (1)

  When a misfire occurs in any of the cylinders, the rotational speed of the crankshaft decreases, so the time required to rotate the misfire detection section becomes longer. As a result, (T4−T3) in the above equation (1) becomes larger than (T2−T1), and the rotational fluctuation amount ΔNe increases. Therefore, in the next process, it is determined whether or not the rotation fluctuation amount ΔNe is larger than a predetermined misfire detection value. Here, the misfire detection value is set to an appropriate value based on the engine speed or the like so that the presence or absence of misfire can be identified. In the misfire detection control, every time the rotation fluctuation amount ΔNe exceeds the misfire detection value, the misfire counter provided in the ECU 50 is incremented by “1”. For example, when the value of the misfire counter exceeds a reference value while the crankshaft rotates a predetermined number of times, it is determined that an abnormal misfire state has occurred.

[Features of Embodiment 1]
FIG. 2 is an explanatory diagram showing the relationship between the retard amount of the ignition timing, the misfire detection margin and the exhaust temperature. The misfire detection margin is a quantitative representation of the accuracy of misfire detection based on the calculation accuracy of the rotational fluctuation amount ΔNe, the frequency of misdetection of misfire, etc., and the misfire detection margin is large. Thus, misfire detection can be performed accurately and stably. As shown in FIG. 2 (a), the misfire detection margin decreases as the ignition timing retard amount (ignition retard amount) increases, and if the retard amount exceeds the upper limit value a1, misfire detection is impossible. To a certain level. This is because if the ignition timing is retarded, the combustion state in the cylinder becomes slow, and the rotational fluctuation amount ΔNe in the normal combustion state becomes large. As a result, the difference in rotational fluctuation amount ΔNe between normal combustion and misfire occurrence becomes small, and the misfire detection accuracy decreases.

  On the other hand, catalyst warm-up control is performed when the internal combustion engine is started. In this control, as shown in FIG. 2 (b), the ignition retard amount is increased to the lower limit value a2 or more, so that the temperature of the catalyst inflow gas after the start is a temperature necessary for warming up the catalyst (catalyst warming request). ) Raise more. Therefore, at the time of starting the internal combustion engine, it is necessary to control the ignition retard amount in the range of the upper limit value a1 to the lower limit value a2 in order to accurately detect misfire while promoting warming up of the catalyst.

  Therefore, in the present embodiment, the retard amount of the ignition timing aop set by the ignition timing control is limited by the ignition retard guard aopg. That is, if the advance direction of the ignition timing is a positive direction, the ignition retard guard aopg limits the ignition timing aop of each cylinder to an angle greater than the ignition retard guard aogp (aop ≧ aopg). The ignition retard guard aopg is basically a retard limit value for limiting the ignition retard amount to the upper limit value a1 or less, and the value is the intake valve 34 as shown in FIG. Is determined based on the valve opening timing (IVO).

  FIG. 3 is a characteristic diagram for determining the ignition retard guard based on the opening timing of the intake valve. In this figure, the ignition delay guard aopg is set with the advance direction of the ignition timing as the positive direction. For example, changing the ignition delay guard aogg to the retard side is equivalent to reducing the value thereof. is doing. FIG. 3 shows the final value of the ignition retard guard aopg. This final ignition retard guard aopg is expressed by a guard reference value aopgs described later as shown in the following equation (2). And the advance correction value aopadv is added.

aopg = aopgs + aopadv (2)

  Next, the guard reference value aopgs and the advance correction value aopadv will be described. First, FIG. 4 is a characteristic diagram for determining the guard reference value based on the IVO of the own cylinder. Here, the “own cylinder” means a cylinder that is subject to ignition timing control. That is, FIG. 4 shows data for setting a guard reference value aopgs for an arbitrary cylinder based on the IVO of the cylinder. The guard reference value aopgs is a basic component that is changed based on the IVO of the own cylinder in the ignition retard guard aopg.

  When the IVO is retarded, the combustibility of the air-fuel mixture is improved as described above, so that the variation in the rotational fluctuation amount ΔNe in the normal combustion state is reduced. Accordingly, the more the IVO is retarded, the more the misfire detection margin can be increased by suppressing the variation in the rotational fluctuation amount ΔNe. Therefore, the ignition timing aop is retarded by a corresponding amount (the ignition retard guard aogp is retarded). Change to the side). Therefore, in the present embodiment, as shown in FIG. 4, as the retard amount of IVO in the own cylinder (one cylinder) is larger, the guard reference value aopgs of the cylinder is decreased, and the value is set to the retard side. The configuration is changed.

  The characteristic of the above-described guard reference value aopgs is reflected in the ignition retard guard aopg by the above equation (2) as shown in FIG. Therefore, according to the guard reference value aopgs, the ignition timing can be retarded as much as possible in accordance with the IVO within a range in which a sufficient misfire detection margin is ensured. Therefore, at the time of starting the engine or the like, by delaying the IVO and the ignition timing, it is possible to ensure the misfire detection accuracy while promoting the warm-up of the catalyst.

  Next, the advance correction value aopadv will be described. FIG. 5 is a characteristic diagram for determining an advance correction value based on the IVO of another cylinder. Here, the “other cylinder” includes all cylinders other than the own cylinder. That is, FIG. 5 shows data for setting the advance correction value aopadv of any cylinder based on the IVO of any other cylinder. Further, the advance correction value aopadv is a component that is changed based on the IVO of another cylinder in the ignition retard guard aopg.

  When the intake valve delay opening control is executed, the IVO of another cylinder is set in the vicinity of the boundary of the misfire detection section of one cylinder (one cylinder) (for example, in the vicinity of ATDC 30 ° CA that is the end point of the misfire detection section). There is a case. In this case, since the occurrence timing of the rotational fluctuation that occurs when the intake valve opens in the other cylinders is likely to vary outside and outside the misfire detection section, the measured values and rotational fluctuation amounts of the aforementioned times T1 to T4 An error occurs in the calculated value of ΔNe, and the accuracy of misfire detection decreases. In particular, if the ignition timing is retarded in this state, the accuracy of misfire detection is further reduced, and there is a possibility that the level becomes undetectable.

  Therefore, in the present embodiment, in any one cylinder, when the IVO of another cylinder is positioned near the boundary of the misfire detection section of the one cylinder, the misfire detection of the ignition timing aop of the one cylinder is detected. It is set as the structure adjusted within the range with which the precision of this is ensured. Specifically, the retard amount of the ignition timing aop of one cylinder is limited. This configuration is realized by the advance correction value aopadv in the area A as shown in FIG. The area A is an angle range corresponding to the vicinity of the boundary of the misfire detection section of one cylinder. The advance correction value aopadv is set to a positive (advance side) value that changes according to the IVO when the IVO of the other cylinder is set in the region A, and in other cases (normal time) Is set to zero. As shown in FIG. 3, this characteristic is reflected in the ignition delay guard aogp by the equation (2). As a result, the ignition delay guard aogp is set to the normal value (other than the boundary of the misfire detection section of one cylinder) when the IVO of the other cylinder is positioned near the boundary of the misfire detection section of one cylinder. The ignition retard guard value when the IVO of the cylinder is not positioned is changed to an advance side. Accordingly, the ignition timing aop of the own cylinder is corrected to the advance side by the ignition retard guard aopg if the IVO of any of the other cylinders is set within the region A.

  According to the above configuration, misfire detection can be performed stably even when the IVO of another cylinder is set near the boundary of the misfire detection section. That is, when the ignition timing is corrected to the advance side, the rotational fluctuation amount ΔNe in the normal combustion state is reduced and the misfire detection accuracy is improved, so that the IVO of the other cylinders varies within and outside the misfire detection section. Even so, misfire detection can be performed stably. In other words, the influence of the opening operation of the intake valve of the other cylinder on the rotation fluctuation amount ΔNe can be suppressed by the advance of the ignition timing, and misdetection of misfire can be prevented. Therefore, even when the IVO is retarded by the intake valve delay opening control, misfire of each cylinder can be accurately detected, and both the intake valve control and the misfire detection accuracy can be ensured at the same time.

  In the above description, the vicinity of the boundary of the misfire detection section is defined as a predetermined angle range (θ ± α) including the boundary θ ° CA, for example. Therefore, whether or not the IVO (target valve opening timing) of the other cylinder is set near the boundary of the misfire detection section is determined by whether or not θ + α ≧ IVO ≧ θ−α is established. Α is a parameter for setting an angle range in the vicinity of the boundary, and is set based on a deviation amount between the target valve opening timing and the actual valve opening timing. If this deviation amount is large, even if the target valve opening timing is away from the boundary θ, the actual valve opening timing may vary outside and within the misfire detection section across the boundary θ. Is set to a large value, and the angle range near the boundary is preferably widened.

[Specific Processing for Realizing Embodiment 1]
FIG. 6 is a flowchart of control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed during the operation of the internal combustion engine. In the routine shown in FIG. 6, first, the IVOs (target valve opening timings of the own cylinder and other cylinders) set by the intake valve delay opening control are read (step 100). Further, the current ignition timing aop of the own cylinder calculated by the ignition timing control is read (step 102).

  In the next process, by referring to the data of FIGS. 4 and 5 stored in advance in the ECU 50, the ignition retard guard aopg is calculated based on the IVO of the own cylinder and the other cylinders (step 104). Specifically, first, the guard reference value aopgs is calculated from the data of FIG. 4 based on the IVO of the own cylinder, and the advance correction value aopadv is calculated from the data of FIG. 5 based on the IVO of the other cylinder. In the process of calculating the advance angle correction value aopadv, for example, the advance angle correction value aopadv is calculated for each cylinder based on the IVO of each of the other cylinders. Adopt as value aopadv. Then, the ignition retard guard aopg is calculated by adding the guard reference value aopgs and the advance correction value aopadv.

  In the next process, it is determined whether or not the ignition timing aop is equal to or greater than the ignition delay guard aogp (step 106). When this determination is established, it is not necessary to limit the ignition timing aop, so various controls using the ignition timing aop are executed (step 108). On the other hand, when the determination in step 106 is not established, the value of the ignition delay guard aopg is substituted for the ignition timing aop to limit the retard amount of the ignition timing aop (step 110).

  As described above in detail, according to the present embodiment, the guard reference value aopgs is determined according to the IVO within a range in which the misfire detection accuracy is sufficiently ensured when the IVOs of other cylinders do not affect the misfire detection accuracy. The ignition timing can be retarded, and both warming up of the catalyst and ensuring of misfire detection accuracy can be achieved at the same time. Further, when the IVO of the other cylinder is set in the vicinity of the boundary of the misfire detection section, the advance correction value aopadv can correct the ignition timing to the advance side and sufficiently ensure the misfire detection accuracy. Accordingly, it is possible to smoothly perform intake valve slow opening control and warm-up of the catalyst while accurately detecting misfire of each cylinder.

  In the first embodiment, as described above, when the internal combustion engine enters a predetermined operation state (during cold start or the like), the control for delaying the valve opening timing of the intake valve 34 by the VVT 38 is the intake valve delay. A specific example of the opening control means is shown. Further, the rotation fluctuation amount ΔNe is calculated based on the times T1 to T4 required for the crankshaft 18 to rotate from the start point to the end point of the first and second misfire detection sections, and this rotation fluctuation amount ΔNe and the misfire detection value are calculated. The control for performing misfire detection based on the magnitude relationship between and indicates a specific example of the misfire detection means. Further, in the first embodiment, the processing of steps 106 and 110 shown in FIG. 6 and the ignition delay guard aogp shown in FIG. 3 show a specific example of the ignition timing delay limiting means. Further, the processing at step 104 and the advance correction value aopadv shown in FIG. 5 show a specific example of the ignition timing adjusting means, and the processing at step 104 and the guard reference value aopgs shown in FIG. A specific example is shown.

  In the first embodiment, the case where the target valve opening timing is set near the end point of the first misfire detection section has been described as an example. However, the present invention is not limited to this, and when the target valve opening timing is set in the vicinity of the start point of the first misfire detection section, or in the vicinity of the start point or end point of the second misfire detection section Also, the section change control can be applied. Furthermore, in Embodiment 1, the specific crank angle was illustrated as a boundary of a misfire detection area. However, the present invention is not limited to these specific values, and the range and boundary of the misfire detection section can be arbitrarily set as necessary.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. Although the present embodiment employs the same system configuration (FIG. 1) as that of the first embodiment, the configuration differs from the first embodiment in the control contents described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
Immediately after starting the internal combustion engine, the combustion state at low temperature is unstable, so it is difficult to retard the ignition timing greatly. However, when time elapses after starting, the wall temperature of the combustion chamber rises and the combustion state is improved, so that the ignition timing can be retarded. Therefore, in this embodiment, in addition to the configuration of the first embodiment, the ignition timing in the unwarmed state immediately after the start is limited to the advance side with respect to the ignition timing after the completion of warming up. This configuration is realized by the following first ignition retardation guard aogpgivo and second ignition retardation guard aoggga.

  FIG. 7 is a characteristic diagram for determining the first ignition retard guard based on the IVO of the own cylinder. The first ignition delay guard aogpgivo is set based on the guard reference value and the advance correction value in substantially the same manner as the ignition delay guard aogg in the first embodiment. However, in the present embodiment, the second ignition retard guard aopgga that functions in an unwarmed state immediately after starting is used together. For this reason, the first ignition retard guard aopgivo is set on the assumption that it functions after the completion of warm-up, and can be set on the retard side compared to the ignition retard guard aopg of the first embodiment. It has become.

  Next, FIG. 8 is a characteristic diagram for determining the second ignition retardation guard based on the starting water temperature and the integrated air amount after starting. As shown in FIG. 8, the second ignition retard guard aopgga is variably set based on the starting water temperature thws and the post-startup integrated air amount GaT. Here, the post-startup integrated air amount GaT is obtained by integrating the intake air amount Ga detected by the air flow sensor 24 from the start, and corresponds to the total amount of air burned in the cylinder from the start. ing. For this reason, the post-startup integrated air amount GaT increases as the warm-up progresses. However, when the water temperature at the start-up is low, the progress of the warm-up is delayed by that amount. Therefore, by specifically obtaining this characteristic through experiments or the like, it is possible to detect the warm-up state of the internal combustion engine based on the starting water temperature thws and the integrated air amount GaT after starting.

  The second ignition retard guard aopgga has a larger value (advanced value) as the starting water temperature thws is lower, and a smaller value (retarded value) as the accumulated air amount GaT increases after starting. Is set. This is because the combustion state immediately after start-up tends to become unstable as the start-up water temperature is lower. Therefore, when the start-up water temperature is low, it is necessary to advance the ignition timing by a corresponding amount. Further, the warm-up of the engine proceeds from the initial warm-up state according to the start-time water temperature thws as the integrated air amount GaT after the start increases. Accordingly, the advance amount of the ignition timing by the second ignition retard guard aopgga can be made smaller as the post-startup integrated air amount GaT increases.

  The final ignition delay guard aogg is set to a larger value of the first ignition delay guard aoggivo and the second ignition delay guard aoggga. Therefore, as shown in FIGS. 7 and 8, the second ignition retard guard aopgga has a value larger than the first ignition retard guard aopgivo immediately after the start, and the post-start accumulated air amount GaT is at a predetermined level. After the time point (when the warm-up is completed) is exceeded, the value is set to be smaller than the first ignition retard guard aopgivo. That is, in the present embodiment, when it is detected that the engine is not warmed up based on the accumulated air amount GaT after starting, etc., the final ignition delay guard aopg is set by the second ignition delay guard aopgga. The configuration is changed to the advance side. Thus, the second ignition delay guard aopgga can function in the unwarmed state, and the first ignition delay guard aopgivo can function after the warm-up is completed.

[Specific Processing for Realizing Embodiment 2]
FIG. 9 is a flowchart of control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is repeatedly executed during the operation of the internal combustion engine. In the routine shown in FIG. 9, first, IVOs of all cylinders and the current ignition timing aop of the own cylinders are read in substantially the same manner as in Steps 100 to 104 of the first embodiment (FIG. 6). One ignition retard guard aopgivo is calculated (steps 200, 202, 204).

  In the next process, the second ignition delay guard aopgga is calculated based on the starting water temperature thws detected by the water temperature sensor 42 and the aforementioned post-starting integrated air amount GaT by referring to the data of FIG. (Step 206). Then, by comparing the magnitudes of the first ignition retard guard aopgivo and the second ignition retard guard aopgga, the larger one of these is set as the final ignition retard guard aopg (steps 208, 210, 212). When the engine warm-up state is detected by the processing in steps 208 to 212, and the engine is not warmed up, the second ignition retard guard aopgga is selected as the ignition retard guard aopg. In the next process, by performing the same process as steps 106 to 110 in the first embodiment, the ignition timing aop is limited to a value equal to or greater than the ignition delay guard aopg, and various controls using the ignition timing aop are performed. Execute (Steps 214, 216, 218).

  Also in the present embodiment configured as described above, substantially the same operational effects as those of the first embodiment can be obtained by the first ignition delay guard aogpgivo. In the present embodiment, the warm-up state of the internal combustion engine can be detected based on the starting water temperature thws and the post-starting integrated air amount GaT. Thereby, when it is detected that the engine is not warmed up, the ignition timing aop is advanced by the second ignition retard guard aopgga, and the combustion state can be stabilized.

  In addition, after the engine is started, the ignition retard guard can be switched from the second ignition retard guard aopgga to the first ignition retard guard aopgivo as the warm-up progresses. Thereby, the ignition timing can be retarded as much as possible according to the warm-up state, and the warm-up efficiency of the catalyst can be maximized within a range where the combustion state is stable. Moreover, since the second ignition retard guard aopgga is used in an unwarmed state immediately after starting, the first ignition retard guard aopgivo is sufficiently retarded on the assumption that it will be used after the warm-up is completed. Value can be set. As a result, the function of the first ignition retard guard aogpgivo can be maximized.

  In the second embodiment, the processing of steps 214 and 218 shown in FIG. 9 shows a specific example of the ignition timing retardation limiting means. Further, the process of step 204 and the first ignition delay guard aogpgivo shown in FIG. 7 show specific examples of the ignition timing adjusting means and the retard limit value varying means. Step 208 shows a specific example of the warm-up state detecting means, and step 210 and the second ignition retard guard aopgga shown in FIG. 8 show a specific example of the non-warm-up advance means.

  In the second embodiment, the warm-up state of the internal combustion engine is detected based on the starting water temperature thws and the post-startup integrated air amount GaT, and if it is detected that the engine is not warmed up, the second ignition delay is detected. The corner guard aopgga is configured to function. However, the present invention is not limited to this. For example, the warm-up state may be detected based on only the integrated air amount GaT after starting without using the starting water temperature thws. Further, in the present embodiment, the starting water temperature thws is used as an example of the engine temperature, and the present invention is not limited to this. For example, the outside air temperature, the oil temperature of the lubricating oil, and the integrated air amount GaT after starting It is good also as a structure which detects the warm-up state of an internal combustion engine based on this.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. Although the present embodiment employs the same system configuration (FIG. 1) as that of the first embodiment, the configuration differs from the first embodiment in the control contents described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
Depending on the operating state of the internal combustion engine, the ignition timing may be advanced by ignition timing control, or the retard amount of the ignition timing may be suppressed. That is, it is difficult to retard the ignition timing when the generated torque is small due to the poor combustion state, such as at the start, or when the engine friction is large, rather it is necessary to advance the ignition timing. Therefore, there is a problem that the warm-up efficiency of the catalyst is lowered. As a method for coping with this, it is conceivable to increase the intake air amount or enrich the air-fuel ratio. However, when the intake air amount is increased, the fuel consumption is deteriorated, and when the air-fuel ratio is enriched, the exhaust emission is easily deteriorated.

  Therefore, in the present embodiment, it is determined whether or not the ignition timing advance request is generated by the ignition timing control, and if it is determined that the advance angle request is generated, the ignition timing is advanced. The IVO is retarded. When the IVO is retarded, the intake air flow rate is increased and the combustion state is improved, so that the ignition timing can be retarded by that amount. That is, even if the actual ignition timing is not advanced, it is possible to satisfy the advance angle requirement by retarding the IVO, thereby making it possible to improve both the combustion state and the warm-up of the catalyst. This configuration is realized by the following ignition delay decreasing side guard aopg2.

  FIG. 10 is a characteristic diagram for determining the ignition retard guard and the ignition retard reduction guard based on IVO in the third embodiment of the present invention. As shown in FIG. 10, the ignition retard guard aopg1 is set as a retard limit value similar to the ignition retard guard aopg of the first embodiment. Further, the ignition retard decrease side guard aopg2 is a determination value for determining whether or not an advance angle request is generated, and the value thereof is, for example, an ignition timing advanced by an advance angle request of ignition timing control. It is set based on the minimum value. Accordingly, when the ignition timing aop is greater (advanced) than the ignition retard decrease guard aopg2, it can be determined that an advance angle request has occurred. In the example shown in the present embodiment, the value of the ignition retard angle reduction guard aopg2 is set by offsetting the ignition delay guard aopg1 by a fixed value to the advance side.

  If it is determined by the above determination that an advance angle request has occurred, the IVO is retarded within a range limited by the predetermined IOV retardation guard IVO_A shown in FIG. Here, when the IVO is retarded excessively, the pump loss increases due to the delay in the opening operation of the intake valve, and the operating angle (valve opening period) of the intake valve decreases, thereby reducing the interval between the cylinders. The variation in the intake air amount at the time increases. For this reason, the value of the IOV retardation guard IVO_A is set based on, for example, the minimum value (maximum retardation value) of the IVO such that the increase amount of the pump loss and the variation amount of the intake air amount are within the allowable range. According to this configuration, even if the ignition timing needs to be advanced, it can be dealt with by retarding the IVO instead.

[Specific Processing for Realizing Embodiment 3]
FIG. 11 is a flowchart of control executed by the ECU in the third embodiment of the present invention. The routine shown in this figure is repeatedly executed during the operation of the internal combustion engine. In the routine shown in FIG. 11, first, the IVOs of all the cylinders and the current ignition timing aop of the own cylinders are read in substantially the same manner as in steps 100 and 102 of the first embodiment (FIG. 6) (steps 300 and 302). ).

  Then, by referring to the data of FIG. 10, the ignition delay guard aopg1 and the ignition delay decrease guard aopg2 are calculated based on IVO (step 304). In this case, the ignition retard guard aopg1 is calculated based on the guard reference value and the advance correction value, as in the first embodiment. On the other hand, the ignition retard decrease guard aopg2 is set by the same method as the ignition retard guard aopg1, or is calculated by adding a fixed value to the ignition retard guard aopg1.

  In the next process, it is determined whether or not the ignition timing aop is equal to or less than the ignition delay decreasing side guard aopg2 (step 306). When this determination is established, it is considered that the advance angle request is not generated. Therefore, the ignition timing aop is limited to a value equal to or greater than the ignition retard guard aopg1 by performing the same processing as steps 106 to 110 in the first embodiment. Above, various controls using the ignition timing aop are executed (steps 308, 310, 312).

  On the other hand, when the determination in step 306 is not established, it is considered that an advance angle request has occurred. Therefore, in this case, as described above, the IVO retardation control for retarding the IVO is executed (step 314). Then, it is determined whether or not the retarded IVO is equal to or greater than the IOV retard guard IVO_A. When this determination is established, the routine proceeds to step 308 (step 316). If the determination in step 316 is not established, the value of IVO_A is substituted for IVO, and the process proceeds to step 308 (step 318).

  Also in the present embodiment configured as described above, substantially the same operational effects as those of the first embodiment can be obtained by the ignition retard guard aopg1. Further, in the present embodiment, it is possible to determine whether or not an advance angle request is generated using the ignition delay decreasing side guard aogg2. If there is an advance angle request, it can be dealt with by IVO retard angle control instead of this, and it is not necessary to advance the ignition timing as much as possible. Therefore, while maintaining a good combustion state, the catalyst Can improve the warm-up efficiency.

  In the third embodiment, the processing of steps 308 and 312 shown in FIG. 11 shows a specific example of the ignition timing retard limiter. Further, the processing of step 304 and the ignition retard guard aopg1 shown in FIG. 10 show specific examples of the ignition timing adjusting means and the retard limit limiting variable means. Further, step 306 and the ignition delay decreasing side guard aogp2 shown in FIG. 10 show a specific example of the advance angle request determination means, and step 314 shows a specific example of the intake valve alternative delay angle control means.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the same system configuration as that of the first embodiment (FIG. 1) is adopted. However, in the internal combustion engine that can use alcohol fuel, the following control is performed. Therefore, the configuration is different from that of the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 4]
In general, since alcohol fuel has good volatility at high temperatures, the combustion state becomes better as the alcohol concentration in the fuel becomes higher after the warm-up is completed, and the ignition timing can be greatly retarded. On the other hand, since alcohol fuel does not have good volatility at low temperatures, it is preferable to advance the ignition timing as much as possible immediately after startup (until the combustion chamber exceeds a certain temperature). Therefore, in the present embodiment, it is determined whether or not the warm-up is completed based on the integrated air amount GaT after starting, and after the warm-up is completed, the ignition retard guard aopg is retarded as the alcohol concentration in the fuel increases. Change to the corner. Further, in the non-warm-up state, the ignition retard guard aopg is set to the advance side with respect to the value after the warm-up is completed.

  The determination as to whether or not the warm-up has been completed (warm-up determination) is performed based on whether or not the post-startup integrated air amount GaT described in the second embodiment is greater than the warm-up determination air amount gathws. Here, the warm-up determination air amount gathws is a determination value for determining warm-up, and is variably set based on the starting water temperature thws. FIG. 12 is a characteristic diagram for determining the warm-up determination air amount based on the starting water temperature in the fourth embodiment of the present invention. The warm-up of the internal combustion engine proceeds as the accumulated air amount GaT after the start increases, but the amount of air required to complete the warm-up increases as the start-up water temperature thws decreases. For this reason, as shown in FIG. 12, the warm-up determination air amount gathws is set to increase as the starting water temperature thws decreases.

  Next, FIG. 13 is a characteristic diagram for determining the ignition retard guard based on the alcohol concentration in the fuel and the IVO. In the present embodiment, as shown in FIG. 13, a plurality of types (for example, three types) of ignition retard guards aopg that are applied to fuels having different alcohol concentrations are provided. For example, the ignition retard guard aopg0 is applied to non-alcohol fuels such as gasoline whose alcohol concentration in the fuel is 0%, and the ignition retard guard aopg50 and aopg100 have alcohol concentrations of 50% and 100%, respectively. It is applied to alcohol fuel. These ignition retardation guards are calculated based on the guard reference value and the advance correction value, as in the first embodiment. Further, each ignition retard guard aopg0, aopg50, aopg100 is set so that aopg0> aopg50> aopg100 in the same IVO.

  The ECU 50 determines one of these ignition retard guards as a final ignition retard guard aopg based on the result of the warm-up determination described above and the alcohol concentration in the fuel detected by the alcohol concentration sensor 44. Calculate as More specifically, first, when it is determined that the engine is not warmed up, that is, when the post-startup integrated air amount GaT is equal to or less than the warm-up determination air amount gathws, the ignition retard guard aopg0 is set as the ignition retard guard aopg. Selected. Therefore, the ignition retard guard aopg in the unwarmed state is set to an advance side with respect to the value after the warm-up is completed, and is a value comparable to that when using a non-alcohol fuel such as gasoline.

  As a result, when the engine is not warmed up, the ignition timing can be advanced by the ignition retard guard aopg (aopg0), and the combustion state can be stabilized even at a low temperature at which the fuel is difficult to volatilize. Further, in an unwarmed state immediately after start-up, it is necessary to increase the amount of injected fuel by an amount that makes it difficult for the fuel to volatilize. As a result, unburned HC in the exhaust gas increases and exhaust emission tends to deteriorate. However, in the present embodiment, by using the ignition delay guard aogp, the ignition timing can be retarded to some extent as compared with the conventional case, thereby increasing the catalyst warm-up efficiency and reducing the exhaust emission. Can be supplemented.

  On the other hand, if the post-startup cumulative air amount GaT is greater than the warm-up determination air amount gathws and it is determined that the warm-up has been completed, the ignition retard guard aopg0, aopg50, Any one of aopg100 is selected as the final ignition retard guard aopg. Therefore, after completion of warm-up, the higher the alcohol concentration in the fuel, the more the ignition retard guard aopg can be changed to the retard side, and the characteristics of alcohol fuel with high volatility at high temperatures can be used for ignition. The timing can be retarded as much as possible. Thereby, in the internal combustion engine using alcohol fuel, it is possible to achieve both improvement of the combustion state and warm-up of the catalyst.

  In the above description, for example, three types of ignition retard guards aopg0, aopg50, and aopg100 are used corresponding to the case where the alcohol concentration in the fuel is 0%, 50%, and 100%. However, the specific values of the alcohol concentration and the number of types of ignition retard guards described above are merely examples described in the present embodiment, and in the present invention, these specific values and the number of types may be arbitrarily set. It is. Moreover, in this invention, the various alcohol fuel containing alcohol components, such as methanol and ethanol, can be used as alcohol fuel.

[Specific processing for realizing Embodiment 4]
FIG. 14 is a flowchart of control executed by the ECU in the fourth embodiment of the present invention. The routine shown in this figure is repeatedly executed during the operation of the internal combustion engine. In the routine shown in FIG. 14, first, the water temperature sensor thws is taken in by the water temperature sensor 42 (step 400). Then, the warm-up determination air amount gathws is calculated based on the starting water temperature thws by referring to the data in FIG. 12 (step 402). Further, the integrated post-startup air amount GaT integrated from the start, the IVO of all cylinders, and the current ignition timing aop are taken in (steps 404, 406, and 408).

  In the next process, the ignition retard guard aopg0 is set according to the IVO by the method described in the first embodiment (step 410), and the alcohol concentration (for example, ethanol concentration) in the fuel detected by the alcohol concentration sensor 44 is set. (Step 412). In this case, the other ignition retard guards aopg50 and aopg100 may be set in the same manner as the ignition retard guard aopg0. For example, an offset having a magnitude corresponding to the alcohol concentration is set with respect to the ignition retard guard aopg0. You may set by adding (subtracting).

  In the next process, it is determined whether or not the post-startup integrated air amount GaT is equal to or less than the warm-up determination air amount gathws (step 414). When this determination is satisfied, the ignition delay guard is used as the final ignition delay guard aopg. aopg0 is selected (step 416). If the determination in step 414 is not satisfied, one of ignition retard guards aopg0, aopg50, and aopg100 (referred to as aopge) is selected according to the alcohol concentration (step 418), and the selected ignition retard guard aopge is finally selected. The ignition delay angle guard aopg is determined (step 420). Thereby, the final ignition delay guard aopg is calculated. Therefore, in the next process, by performing the same process as Steps 106 to 110 of the first embodiment, the ignition timing aop is limited to a value equal to or greater than the ignition retard guard aopg, and various types using the ignition timing aop are performed. Control is executed (steps 422, 424, 426).

  In the fourth embodiment, the processing of steps 422 and 426 shown in FIG. 14 shows a specific example of the ignition timing retardation limiting means. Further, the processing of steps 410, 418, 420 and the ignition retard guards aopg0, aopg50, aopg100 shown in FIG. 13 show specific examples of the ignition timing adjusting means, the retard limit value varying means, and the alcohol fuel compatible retard means. Yes.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 14 Piston 16 Combustion chamber 18 Crankshaft 20 Intake passage 22 Exhaust passage 24 Air flow sensor 26 Throttle valve 28 Throttle motor 30 Fuel injection valve 32 Spark plug 34 Intake valve 36 Exhaust valve 38 VVT (Valve timing variable means)
40 Crank angle sensor 42 Water temperature sensor 44 Alcohol concentration sensor (alcohol concentration detection means)
50 ECU
aopg, aopg1 ignition retard guard (retard limit value)

Claims (6)

Valve timing variable means capable of variably setting the opening timing of the intake valves for the intake valves respectively provided in the plurality of cylinders of the internal combustion engine;
An intake valve delay opening control means for retarding the valve opening timing of the intake valve by the valve timing variable means when the internal combustion engine is in a predetermined operation state;
Misfire detection means for measuring the time required for the crankshaft of the internal combustion engine to rotate from the start point to the end point of the misfire detection section within a predetermined crank angle range, and for detecting misfire in the plurality of cylinders based on the time, ,
In any one of the plurality of cylinders, when the opening timing of the intake valve of another cylinder is positioned near the boundary of the misfire detection section of the one cylinder, the ignition timing of the one cylinder is set. Ignition timing adjusting means for adjusting within a range in which the accuracy of misfire detection is ensured;
A control device for an internal combustion engine, comprising: Ignition timing retardation limiting means for limiting the amount of retardation of the ignition timing by the retardation limit value,
The ignition timing adjustment means sets the retard limit value of the one cylinder to a normal limit when the valve opening timing of the intake valve of the other cylinder is located near the boundary of the misfire detection section of the one cylinder. The normal limit value is a delay angle when the valve opening timing of the intake valve of the other cylinder is not located near the boundary of the misfire detection section of the one cylinder. 2. The control device for an internal combustion engine according to claim 1, wherein the control value is a limit value. A retard limit value variable means for changing the retard limit value of the one cylinder to the retard side as the retard amount of the opening timing of the intake valve in the one cylinder is larger;
3. The control device for an internal combustion engine according to claim 2, wherein the ignition timing retardation limiting means is configured to reflect a change result by both the ignition timing adjusting means and the retardation limit value varying means in the retardation limit value. . A warm-up state detecting means for detecting a warm-up state of the internal combustion engine;
When the internal combustion engine is detected to be in an unwarmed state by the warm-up state detecting means, an unwarmed-up advance means for changing the retard limit value to an advance side;
The control device for an internal combustion engine according to claim 2 or 3, further comprising: Alcohol concentration detection means for detecting the alcohol concentration in the fuel;
An alcohol fuel retarding means for changing the retard limit value to the retard side as the alcohol concentration is higher;
The control apparatus for an internal combustion engine according to any one of claims 2 to 4, further comprising: Advance angle request determining means for determining whether or not an advance angle request for ignition timing has occurred;
Intake valve alternative retard control means for retarding the opening timing of the intake valve instead of advancing the ignition timing when it is determined by the advance angle request judging means that an ignition timing advance request has been made When,
The control apparatus for an internal combustion engine according to any one of claims 1 to 5, further comprising:

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