JP2010024928A - Engine controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine controlling device capable of restraining deterioration of emission, fuel economy and drivability while ensuring the safety and avoiding the engine failure even in the case the operation angle is not sensed in an engine comprising a variable valve mechanism for adjusting the operation angle. <P>SOLUTION: An ECU 1A includes a learning control means for learning the output of the O<SB>2</SB>sensor 23 for each operation angle as the sub learning value for correcting the fuel injection amount corrected based on the output of the A/F sensor 22 for an engine 50 having an intake side VVT 70 for having the operation angle adjustable with an A/F sensor 22 and an O<SB>2</SB>sensor 23 provided in an exhaust system 20, a stability determining means for determining whether or not the sub learning value is stable in the case the position of the operation angle is not sensed, and an operation angle estimating means for estimating the operation angle with reference to the sub learning value learned by the learning control means based on the output of the O<SB>2</SB>sensor 23 in the case the sub learning value is determined to be stable by the stability judging means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device for an engine having a variable valve mechanism that varies an operating angle.

  2. Description of the Related Art Conventionally, an engine having a variable valve mechanism that makes the characteristics of intake and exhaust valves variable is known. Specifically, a variable valve mechanism that can change the operating angle (valve opening period) is known as a variable valve mechanism. As a technique relating to such a variable valve mechanism that makes the working angle variable, a technique that is considered to be related to the present invention in that it is related to the exhaust air-fuel ratio is proposed in, for example, Patent Document 1 or 2. Has been. Further, for example, Patent Document 3 proposes a technique that is considered to be related to the present invention in that it is a technique for dealing with a case where the position of the working angle cannot be detected. In addition, for example, Patent Document 4 proposes a technique that is considered to be related to the present invention in that it is a technique related to the position of the operating angle.

JP 2004-132314 A Japanese Patent Laid-Open No. 2004-060455 JP 2005-016456 A JP 2006-013327 A

In engine control, various corrections according to the operating angle are performed by ignition timing control, air-fuel ratio control, control of a variable valve mechanism, and the like. Therefore, when it becomes impossible to detect the position of the operating angle, various corrections corresponding to the operating angle cannot be appropriately performed.
In this regard, as a case where the position of the operating angle can no longer be detected, specifically, for example, a case where an actuator of the variable valve mechanism fails. If the actuator fails, it is desirable to perform control such as shutting off the actuator power from the viewpoint of safety, etc. However, if the actuator power is shut off, the position of the working angle cannot be detected. The position becomes unknown.
When the position of the working angle becomes unknown, the control correction becomes inappropriate. For example, in the control of the variable valve mechanism, if the working angle is inappropriately small, the idle is poor. And engine stall may occur and safety may be impaired. Further, if the operating angle is inappropriately large, a valve stamp may be generated and the engine may be damaged.
For this reason, conventionally, when the position of the operating angle can no longer be detected, the correction value for ignition timing control and variable valve mechanism control is generally set to a fixed value to prevent idling failure, engine stall, valve stamp, etc. However, on the other hand, as a result of not being able to properly correct according to the operating angle, it has been necessary to allow the emission, fuel consumption, and drivability to deteriorate.

  Therefore, the present invention has been made in view of the above problems, and in an engine equipped with a variable valve mechanism that makes a working angle variable, even when the working angle cannot be detected, safety is ensured and the engine It is an object of the present invention to provide an engine control device that can prevent deterioration of emissions, fuel consumption, and drivability while avoiding the failure of the engine.

  The present invention for solving the above-mentioned problems is provided with a variable valve mechanism that makes the working angle variable, and an engine provided with an air-fuel ratio detecting means and a sub air-fuel ratio detecting means for detecting the exhaust air-fuel ratio in the exhaust system. Learning control means for learning the output of the sub air-fuel ratio detection means for each working angle as a sub-learning value for correcting the fuel injection amount corrected based on the output of the air-fuel ratio detection means, and the position of the working angle Stability determination means for determining whether or not the sub-learning value is stable, and when the stability determination means determines that the sub-learning value is stable, the sub-learning value is stable. And operating angle estimating means for estimating an operating angle with reference to the sub-learned value learned by the learning control means based on the output of the air-fuel ratio detecting means.

  In addition, the present invention may further include a promotion control unit that promotes learning of the sub-learning value according to the learning control unit until the sub-learning value is stabilized.

  Further, the present invention may be configured such that, when the operating angle cannot be changed by the variable valve mechanism, the operating angle estimating means estimates the operating angle based on the intake air amount of the engine.

  According to the present invention, in an engine equipped with a variable valve mechanism that makes the operating angle variable, even when the operating angle cannot be detected, the emission and fuel consumption are ensured while ensuring safety and avoiding engine failure. And deterioration of drivability can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing an engine control device according to the present embodiment realized by an ECU (Electronic Control Unit) 1A together with related components such as an engine 50. The intake system 10 includes an air cleaner 11 that filters the intake air, an air flow meter 12 that measures the intake air amount Ga, a throttle valve 13 that adjusts the intake air amount Ga, a surge tank 14 that temporarily stores intake air, an intake air The intake manifold 15 is distributed to each cylinder of the engine 50.

The exhaust system 20 includes an exhaust manifold 21 that merges exhaust from each cylinder, an A / F sensor (corresponding to air-fuel ratio detection means) 22 for linearly detecting an air-fuel ratio based on the oxygen concentration in the exhaust, It has an O ₂ sensor (corresponding to a sub air-fuel ratio detecting means) 23 for detecting whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio based on the oxygen concentration therein. The output of the O ₂ sensor 23 exhibits a so-called Z characteristic that changes relatively rapidly in the vicinity of the theoretical air-fuel ratio.

  The fuel injection system 30 is configured to supply and inject fuel, and includes a fuel injection valve 31, a fuel injection pump 32, a fuel tank 33, and the like. The fuel injection valve 31 is a structure for injecting fuel, and is opened at an appropriate injection timing to inject fuel under the control of the ECU 1A. The fuel injection amount is adjusted by the length of the valve opening period until the fuel injection valve 31 is closed under the control of the ECU 1A. The fuel injection pump 32 is configured to pressurize the fuel and generate an injection pressure, and adjusts the injection pressure to an appropriate injection pressure under the control of the ECU 1A. The fuel injection valve 31 is provided for each cylinder of the engine 50. Specifically, in this embodiment, the fuel injection valve 31 is provided for each cylinder in the intake port 52a. In addition, arrangement | positioning of the fuel injection valve 31 is not restricted to this, For example, the arrangement | positioning which can inject a fuel directly in a cylinder may be sufficient.

  The engine 50 includes a cylinder block 51, a cylinder head 52, a piston 53, a spark plug 54, an intake valve 55, and an exhaust valve 56. The engine 50 shown in the present embodiment is an inline 4-cylinder gasoline engine. However, the engine may have an appropriate cylinder arrangement structure and the number of cylinders, and is not particularly limited as long as the engine can implement the present invention. In FIG. 1, the main part of the cylinder 51a is shown as a representative of each cylinder with respect to the engine 50. However, in this embodiment, the other cylinders have the same structure. The cylinder block 51 is formed with a substantially cylindrical cylinder 51a. A piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber 57 is formed as a space surrounded by the cylinder block 51, the cylinder head 52, and the piston 53.

  In addition to the intake port 52 a for guiding intake air to the combustion chamber 57, the cylinder head 52 is formed with an exhaust port 52 b for exhausting the combusted gas from the combustion chamber 57. The cylinder head 52 is provided with intake and exhaust valves 55 and 56 for opening and closing these intake and exhaust ports 52a and 52b. The spark plug 54 is disposed in the cylinder head 52 with an electrode protruding substantially in the center above the combustion chamber 57. The engine 50 is provided with various sensors such as a crank angle sensor 61 and a water temperature sensor 62 for detecting the cooling water temperature of the engine 50.

  The engine 50 includes an intake side VVT (Variable Valve Timing) 70 (see FIG. 2). The intake side VVT 70 is configured to change the operating angle and valve lift amount of the intake valve 55 and includes a control shaft 71, a connection arm 72, a sliding contact arm 73, and a swing cam 74. Has been. In the intake side VVT 70, the valve lift amount and the operating angle can be made continuously variable by appropriately rotating the control shaft 71 under the control of the ECU 1A. The intake side VVT 70 is provided with a working angle detection sensor (not shown) for detecting a working angle. In the present embodiment, a variable valve mechanism is realized by the intake side VVT 70. The variable valve mechanism may be a variable valve mechanism having an appropriate structure capable of varying at least the working angle.

  The ECU 1A includes a microcomputer (not shown), a microcomputer (corresponding to storage means), a RAM and the like, an input / output circuit, and the like. The ECU 1A is mainly configured to control the engine 50. Specifically, in this embodiment, the ECU 1A controls the fuel injection valve 31, the fuel injection pump 32, an igniter (not shown), the throttle valve 13, the intake side VVT 70, and the like. Is configured to do. These objects to be controlled are electrically connected to the ECU 1A. Various sensors such as an air flow meter 12, a crank angle sensor 61, a water temperature sensor 62, and an operating angle detection sensor are electrically connected to the ECU 1A.

  The ROM is configured to store a program describing various processes executed by the CPU, map data, and the like. The ECU 1A executes various processes based on a program stored in the ROM while using a temporary storage area of the RAM as necessary, so that various control means, determination means, detection means, calculation means, and the like are functional in the ECU 1A. To be realized. In this regard, in the present embodiment, the air-fuel ratio feedback (hereinafter referred to as F / B) control means, sub air-fuel ratio F / B control means, learning control means, stability determination means, working angle estimation means shown below. Are functionally realized by the ECU 1A.

The air-fuel ratio F / B control unit corrects the fuel injection amount based on the output of the A / F sensor 22 so that the exhaust air-fuel ratio becomes a target air-fuel ratio (for example, 14.6). The sub air-fuel ratio F / B control means further corrects the fuel injection amount corrected by the air-fuel ratio F / B control means based on the sub-learning value using the output of the O ₂ sensor 23 as a sub-learning value. At this time, specifically, the sub air-fuel ratio F / B control means further corrects the fuel injection amount corrected by the air-fuel ratio F / B control means so that the output of the O2 sensor 23 becomes 0.5V.

Next, regarding the air-fuel ratio F / B control means and the sub-air-fuel ratio F / B control means, the role of the sub-air-fuel ratio F / B control with respect to the air-fuel ratio F / B control will be specifically described with reference to FIG. Here, there may be some variation in the operating angle of each cylinder due to a manufacturing error of the intake side VVT 70 or the like. If the operating angles of the cylinders vary, the intake air amount varies between the cylinders, and the exhaust air-fuel ratio also varies between the cylinders. In this situation, when the air-fuel ratio F / B control is performed based on the output of the A / F sensor 22, the air-fuel ratio may shift. This is because even if the exhaust gas is stoichiometric as a whole, the gas hitting to the A / F sensor 22 is not uniform, and the mixing of the gas from each cylinder hitting the A / F sensor 22 is insufficient. It depends. In this regard, since the A / F sensor 22 is generally disposed immediately after the gathering portion of the exhaust manifold 21, the air-fuel ratio is likely to shift due to the air-fuel ratio F / B control for the above reason.
On the other hand, the O ₂ sensor 23 disposed at a position considerably away from the exhaust manifold 21 is subjected to a gas that is sufficiently uniformly mixed. For this reason, the air-fuel ratio can be stoichiometrically controlled by the sub air-fuel ratio F / B control based on the output of the O ₂ sensor 23. That is, the sub air-fuel ratio F / B control has a role of correcting the air-fuel ratio F / B control.

  Note that the variation in operating angle between cylinders is unique to the intake-side VVT 70 due to a manufacturing error or the like, and hence the variation in operating angle between cylinders will be expressed as a tolerance. For example, when the working angle is controlled to 200 (deg), the first cylinder is 202 (deg), the second cylinder is 200 (deg), the third cylinder is 198 (deg), and the fourth cylinder is 200 (deg). ), The tolerance is ± 2 (deg).

The learning control means learns the output of the O ₂ sensor 23 for each operating angle as a sub-learning value for correcting the fuel injection amount corrected based on the output of the A / F sensor 22. Specifically, the learning control unit learns the sub-learning value for each operating angle by storing the sub-learning value in the ROM that is the storage unit for each operating angle.
The stability determination unit determines whether or not the sub-learning value is stable when the position of the operating angle cannot be detected.
The action angle estimation means refers to the sub learning value learned by the learning control means based on the output of the O ₂ sensor 23 when the stability determination means determines that the sub learning value is stable. Make an estimate.

  Next, the operation of the ECU 1A will be described using the flowchart shown in FIG. In the ECU 1A, the processing shown in the flowchart of FIG. 4 is repeatedly executed at very short time intervals. The ECU 1A learns the sub-learning value by storing the sub-learning value for each operating angle (step S11). Subsequently, the ECU 1A determines whether or not the working angle can be detected (whether or not the working angle can be monitored) (step S12). If the determination is affirmative, the ECU 1A executes correction according to the operating angle (step S13). On the other hand, if a negative determination is made in step S12, it is determined that the operating angle cannot be detected, and in this case, the ECU 1A determines whether or not the tolerance is equal to or greater than a certain value (step S14).

  Here, the tendency of the sub-learning value with respect to the operating angle will be described with reference to FIG. For example, when there is a tolerance of ± Y with respect to a certain working angle X, Y is a specific value resulting from the intake side VVT 70, and therefore, the smaller the working angle X, the greater the relative influence. That is, there is a correlation that the deviation of the air-fuel ratio becomes larger as the operating angle X is smaller. For this reason, as shown in FIG. 5, the sub-learning value tends to increase as the operating angle decreases, and this tendency appears more prominently in rich tolerance products and lean tolerance products. The same tendency can also be grasped for the X-bar product (average manufactured product) of the intake side VVT 70.

  Therefore, it can be determined from the inclination of the sub-learning value whether the tolerance is equal to or greater than a certain value. If the tolerance is greater than a certain value, the operating angle can be estimated from the tendency based on the sub-learning value. On the other hand, if there is no tolerance or less than a certain value, such a tendency does not appear or it is difficult to grasp. Therefore, if a negative determination is made in step S14, the ECU 1A executes correction when the operating angle is unknown (step S17). As the correction when the operating angle is unknown, specifically, for example, the control value for controlling the intake side VVT 70 can be set to a constant value to prevent the engine stall or the valve stamp. Thereby, safety can be ensured and failure of the engine 50 can be avoided.

On the other hand, if the determination in step S14 is affirmative, the ECU 1A determines whether or not the sub-learning value is stable (step S15). Whether or not the sub-learning value is stable can be determined by whether or not the variation of the sub-learning value is equal to or greater than a predetermined value. If the sub-learning value is not stable, it takes a long time to estimate the operating angle. Therefore, the process proceeds to step S17 as in the case of a negative determination in step S14. Thereby, safety can be ensured and failure of the engine 50 can be avoided. On the other hand, if the determination in step S15 is affirmative, the ECU 1A estimates the operating angle from the stabilized sub-learning value stored in the ROM based on the output of the O ₂ sensor 23 (step S16). In this case, the ECU 1A performs correction according to the estimated operating angle (step S13). Thereby, even when the operating angle cannot be detected, the correction can be appropriately performed as compared with the case where the correction value is set to a constant value.
As described above, the ECU 1A is capable of ensuring the safety and avoiding the failure of the engine 50, even when the operating angle cannot be detected in the engine having the intake side VVT 70 that makes the operating angle variable. Deterioration of fuel consumption and drivability can be suppressed.

  ECU 1B according to the present embodiment includes ECU 1A except that it further includes an acceleration control unit that promotes learning of the sub-learning value (hereinafter simply referred to as sub-learning) according to the learning control unit until the sub-learning value is stabilized. Is substantially the same. In addition, each structure relevant to ECU1B is the same as the case of ECU1A. For this reason, in this embodiment, the ECU 1B and other related components are not shown. The promotion control means can be realized by changing a program stored in the ROM of the ECU 1A.

  Next, the operation of the ECU 1B will be described in detail with reference to the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 4 except that steps S21 and S22 are added as shown. Therefore, in this embodiment, these steps will be described in detail. If the determination in step S15 is negative, the ECU 1B promotes sub-learning (step S21). Here, since sub-learning cannot be performed unless the operation at a certain operating angle continues for a certain time or more, the chance of learning is reduced in transient operation where the operating angle changes frequently. . For this reason, in this step, the ECU 1B specifically stabilizes the sub-learning value by increasing the sub-learning update frequency (increasing the sub-learning speed) or prohibiting fuel cut control that becomes a transient operation. To promote sub-learning, including After step S21, the process proceeds to step S17.

Thereafter, a negative determination is made in step S15 until the sub-learning value becomes stable, and an affirmative determination is made in step S15 when the sub-learning value becomes stable. In this case, the ECU 1B sets the sub-learning speed to a normal speed (step S22). That is, by continuing the process shown in step S21 until the sub-learning value is stabilized, the sub-learning value can be quickly stabilized and the working angle can be estimated quickly. After step S22, the process proceeds to step S16.
As described above, the ECU 1B is capable of ensuring the safety and avoiding the failure of the engine 50 even when the operating angle cannot be detected in the engine having the intake side VVT 70 that makes the operating angle variable. The deterioration of fuel consumption and drivability can be suppressed, and even when the sub-learning value is not stable as compared with the ECU 1A, the sub-learning can be promoted and these effects can be quickly produced.

  The ECU 1C according to the present embodiment is configured such that the working angle estimation means further estimates the working angle based on the intake air amount Ga of the engine 50 when the working angle cannot be changed on the intake side VVT 70. The ECU 1A is substantially the same. In addition, each structure relevant to ECU1C is the same as the case of ECU1A. For this reason, in this embodiment, the ECU 1C and other related components are not shown. Further, the working angle estimation means according to the present embodiment can be realized by changing a program stored in the ROM of the ECU 1A. In this regard, the operating angle estimation means in the ECU 1B can be further configured in the same manner as in this embodiment.

  Next, the operation of the ECU 1C will be described in detail with reference to the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 4 except that steps S31 and S32 are added as shown. Therefore, in this embodiment, these steps will be described in detail. If the determination in step S12 is negative, the ECU 1C determines whether or not the operating angle can be changed (step S31). Whether or not the operating angle can be changed can be determined, for example, based on whether or not the intake side VVT 70 has failed. If it is affirmation determination, it will progress to step S14. On the other hand, if the determination in step S12 is negative, the ECU 1C estimates the operating angle based on the intake air amount Ga (step S32).

FIG. 8 is a diagram schematically showing map data showing the relationship between the intake air amount Ga and the working angle when the working angle cannot be changed, and FIG. 8 shows an example in which the throttle valve 13 is fully opened. . This map data is stored in the ROM in advance. When the operating angle cannot be changed, the opening of the throttle valve 13 is equal to or greater than a certain value, and the intake air amount Ga becomes the operating angle regulation. That is, since the working angle and the intake air amount Ga have a one-to-one relationship, the working angle can be estimated from the intake air amount Ga. Therefore, in step S32, the ECU 1C specifically refers to such map data to estimate the operating angle based on the intake air amount Ga. After step S32, the process proceeds to step S13.
In this way, the ECU 1C can ensure the safety and avoid the engine 50 failure even when the working angle cannot be detected in the engine having the intake side VVT 70 that makes the working angle variable. Deterioration of fuel consumption and drivability can be suppressed, and even when the operating angle cannot be changed as compared with the ECU 1A, these effects can be achieved.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
For example, it is reasonable that the learning control means, the stability determination means, the operating angle estimation means, and the acceleration control means, including the air-fuel ratio F / B control means and the sub air-fuel ratio F / B control means, can be realized by the ECU 1. It may be realized by hardware such as an electronic control device, a dedicated electronic circuit, or a combination thereof. In this regard, the engine control device of the present invention may be realized by, for example, a plurality of electronic control devices or a combination of electronic control devices and hardware such as electronic circuits. That is, the engine control apparatus of the present invention may be realized in a distributed control manner, for example.

It is a figure which shows ECU1A typically with each structure concerned. It is a figure which shows intake side VVT70 typically. It is explanatory drawing which illustrates typically the role of the sub air fuel ratio F / B control with respect to air fuel ratio F / B control. It is a figure which shows operation | movement of ECU1A with a flowchart. It is a figure which shows the tendency of the sub learning value with respect to an action angle with a graph. It is a figure which shows operation | movement of ECU1B with a flowchart. It is a figure which shows operation | movement of ECU1C with a flowchart. It is a figure which shows typically the map data which show the relationship between the intake air amount Ga when a working angle cannot be changed, and a working angle.

Explanation of symbols

1 ECU
12 Air flow meter 13 Throttle valve 22 A / F sensor 23 O ₂ sensor 31 Fuel injection valve 50 Engine 55 Intake valve 70 Intake side VVT

Claims (3)

An engine having a variable valve mechanism that makes the operating angle variable and in which an exhaust air / fuel ratio detecting means and a sub air / fuel ratio detecting means for detecting an exhaust air / fuel ratio are provided in an exhaust system,
Learning control means for learning the output of the sub air-fuel ratio detection means for each operating angle as a sub-learning value for correcting the fuel injection amount corrected based on the output of the air-fuel ratio detection means;
Stability determination means for determining whether or not the sub-learning value is stable when the position of the operating angle cannot be detected;
When the stability determination unit determines that the sub-learning value is stable, the operation angle is determined with reference to the sub-learning value learned by the learning control unit based on the output of the sub-air-fuel ratio detection unit. An engine control device comprising: an operating angle estimating means for performing estimation. The engine control device according to claim 1,
An engine control device further comprising a promotion control unit that promotes learning of the sub-learning value related to the learning control unit until the sub-learning value is stabilized. The engine control device according to claim 1 or 2,
An engine control apparatus characterized in that, when the operating angle cannot be changed by the variable valve mechanism, the operating angle estimation means estimates the operating angle based on the intake air amount of the engine.

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