Control device for internal combustion engine

Abstract

To avoid occurrence of deviation of a knock control system (KCS) learning value in KCS learning control when over temperature protection (OT) amount increase control is performed.SOLUTION: A control device for an internal combustion engine includes: an ignition timing learning control section that detects presence / absence of knocking in the internal combustion engine, corrects ignition timing to eliminate the knocking and performs learning of the corrected ignition timing; and a fuel injection amount increase control section for increasing fuel injection amount to lower a temperature of a catalyst on the basis of the temperature of the catalyst provided in an exhaust system or the like of the internal combustion engine. The ignition timing learning control section stops the learning when the fuel injection amount increase control section increases the fuel injection amount.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine.

Background Art

[0002] In an internal combustion engine, when a catalyst for exhaust gas purification is overheated by, for example, high-temperature exhaust gas, the exhaust gas purification ability may decrease, or the catalyst itself may be melted. Conventionally, in order to avoid these phenomena, a technique is known in which the fuel injection amount is increased to lower the temperature of the exhaust gas by the heat of vaporization of the fuel and cool the catalyst (see, for example, Patent Document 1). Such an increase in the fuel injection amount is called OT (Over Temperature Protection) increase control. Further, conventionally, KCS (Knock Control System) learning control is known in which vibrations generated in the internal combustion engine when appropriate combustion does not occur are detected and the ignition timing is corrected (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in KCS learning control, ignition timing correction is performed when the vibration of the internal combustion engine is detected by a knock sensor. On the other hand, when OT increase control is performed, although the temperature of the catalyst can be decreased, output torque fluctuations of the internal combustion engine due to an increase in the fuel injection amount may occur. The knock sensor may detect the output torque fluctuations caused by OT increase control. However, since the output torque fluctuations caused by OT increase control are not due to knocking, the detection by the knock sensor is a false detection. When KCS learning control is performed based on the falsely detected information, a deviation in the KCS learning value occurs.

[0005] Patent Document 1 and Patent Document 2 do not consider at all the mutual influence between OT increase control and KCS learning control.

[0006] Therefore, the invention disclosed in this specification aims to avoid the occurrence of a deviation in the KCS learning value in KCS learning control when OT increase control is performed.

Means for Solving the Problems

[0007] The above problems are solved by a control device for an internal combustion engine, which includes a ignition timing learning control unit that detects the presence or absence of knocking in the internal combustion engine, corrects the ignition timing so that the knocking is eliminated, and performs learning of the corrected ignition timing, and a fuel injection amount increase control unit that increases the fuel injection amount to lower the temperature of a catalyst provided in an exhaust system or the like of the internal combustion engine based on the temperature of the catalyst. When the fuel injection amount increase control unit is increasing the fuel injection amount, the ignition timing learning control unit stops the learning.

Effects of the Invention

[0008] The invention disclosed in this specification can avoid the occurrence of a deviation in the KCS learning value in KCS learning control when OT increase control is performed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] (Embodiment) Referring to FIG. 1, the schematic configuration of the internal combustion engine 100 according to the embodiment will be described. Various controls of the internal combustion engine 100 are executed by an ECU (Electronic Control Unit) 50 which is a control device. The internal combustion engine 100 includes a plurality of cylinders 2 in a cylinder block (only one cylinder 2 is shown in FIG. 1). A piston 3 is slidably accommodated in each cylinder 2. The piston 3 forms a combustion chamber 2a between itself and a cylinder head disposed above the cylinder block. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. An injector 6 for injecting fuel into the cylinder and a spark plug 7 are provided in the combustion chamber 2a. The fuel injected from the injector 6 is mixed in the combustion chamber 2a and ignited by the spark plug 7. When the ignited air-fuel mixture burns and explodes, the piston 3 is pushed down. The pushed-down piston 3 transmits the explosive force to the crankshaft 5 via the connecting rod 4, rotating the crankshaft 5. A knock sensor 14 for detecting vibration of the internal combustion engine 100 is provided in the cylinder block. Further, a crank angle sensor 15 for detecting the crank angle is provided in the internal combustion engine 100.

[0012] An intake port 8 and an exhaust port 9 are provided in the internal combustion engine 100 so as to face the combustion chamber 2a. An intake pipe 10 forming an intake passage is connected to the intake port 8. An exhaust pipe 11 forming an exhaust passage is connected to the exhaust port 9.

[0013] The intake pipe 10 is provided with an air cleaner 12, an air flow meter 13, a throttle valve 17, and an intake manifold 18 in order from the upstream side of the intake air flow. The air flow meter 13 detects the amount of air flowing in the intake pipe 10. The throttle valve 17 adjusts the amount of air sent into the combustion chamber 2a. The intake pipe 10 branches off at the intake manifold 18 and is connected to the intake ports 8 of each cylinder.

[0014] The exhaust pipe 11 included in the exhaust system is provided with an exhaust manifold 20 and a catalyst 21 in order from the upstream side of the exhaust flow. The catalyst 21 performs exhaust purification.

[0015] The internal combustion engine 100 includes an intake valve 23 that opens and closes the intake port 8 and an exhaust valve 24 that opens and closes the exhaust port 9. The intake valve 23 and the exhaust valve 24 open and close in accordance with the rotation of an intake camshaft and an exhaust camshaft (not shown) that are drivingly connected to the crankshaft 5. Thereby, the intake valve 23 and the exhaust valve 24 are synchronized with the rotation of the crankshaft 5 and are driven to open and close at a predetermined timing corresponding to the reciprocating movement of each piston 3. The internal combustion engine 100 includes an intake VVT mechanism 25, which is a variable valve mechanism that variably sets the valve timing, which is the opening and closing timing of the intake valve 23, and an exhaust VVT mechanism 26, which is a variable valve mechanism that variably sets the valve timing, which is the opening and closing timing of the exhaust valve 24.

[0016] The ECU 50 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a storage device, and the like. The ECU 50 controls the internal combustion engine 100 by executing programs stored in the ROM and the storage device. The ECU 50 is electrically connected to the air flow meter 13, the knock sensor 14, and the crank angle sensor 15, and receives signals from these sensors. Programs and maps used for control are stored in the storage device.

[0017] By executing a program, the ECU 50 functions as a KCS learning control unit 51 as an ignition timing learning control unit and an OT increment control unit 52 as a fuel injection amount increment control unit. Also, by executing a program, the ECU 50 functions as a catalyst temperature acquisition unit 53 and a timing unit 54.

[0018] When the knocking sensor 14 detects vibrations exceeding the threshold value for determining the presence or absence of knocking, the KCS learning control unit 51 determines that knocking has occurred. Then, it corrects the ignition timing so that the knocking is eliminated. Specifically, the KCS learning control unit 51 gradually retards the ignition timing. And the KCS learning control unit 51 stores the ignition timing in the state where the knocking has been eliminated as the KCS learning value. The ECU 50 executes an ignition instruction for the ignition plug 7 based on the KCS learning value in the subsequent control of the internal combustion engine 100.

[0019] When the temperature of the catalyst 21 estimated by the catalyst temperature acquisition unit 53 becomes higher than a preset threshold value, the OT increment control unit 52 implements an increment in the fuel injection amount. The OT increment control unit 52 gives an injection instruction to the injector 6 to inject the incremented fuel injection amount. Thereby, deterioration and melting damage of the catalyst 21 are suppressed. The catalyst temperature acquisition unit 53 estimates the temperature of the catalyst 21 based on the intake air amount acquired by the air flow meter 13 and the rotational speed of the internal combustion engine 100 calculated based on the detection value of the crank angle sensor 15. The temperature of the catalyst 21 is estimated by referring to a map including the intake air amount and the rotational speed of the internal combustion engine 100 as parameters. Since the method for estimating the temperature of the catalyst 21 is conventionally well-known, the detailed description thereof is omitted here. The timing unit 54 measures the elapsed time since the end of the OT increment.

[0020] Next, an example of the control executed by the ECU 50 will be described with reference to FIG. 2. In step S1, the ECU 50 determines whether or not the OT increment control is being executed. When the ECU 50 makes an affirmative determination (Yes determination) in step S1, it proceeds to step S2, and when it makes a negative determination (No determination) in step S1, it proceeds to step S3.

[0021] In step S2, the ECU 50 stops the KCS learning. This is because when the OT increase control is being carried out, the knock sensor 14 may detect the output torque fluctuation of the internal combustion engine 100 caused by the OT increase control. Since the output torque fluctuation caused by the OT increase control is not caused by knocking, the detection by the knock sensor 14 is a false detection. If the KCS learning control is carried out based on the falsely detected information, a deviation in the KCS learning value will occur. Therefore, in the present embodiment, when the OT increase control is being carried out, the KCS learning is stopped. Thereby, the occurrence of the deviation in the KCS learning value can be avoided.

[0022] In step S3, the ECU 50 determines whether or not a predetermined time or more has elapsed since the end of the previous OT increase control. When the OT increase control unit 52 finishes the OT increase control, it causes the timing unit 54 to start timing. In step S3, it is determined whether or not the time measured by the timing unit 54 is a predetermined time or more.

[0023] In step S3, when the ECU 50 makes a negative determination, it returns the process via step S2. That is, the ECU 50 continues to stop the KCS learning and repeats the process from step S1. On the other hand, when the ECU 50 makes an affirmative determination in step S3, it proceeds to step S4. In step S4, the ECU 50 resumes the KCS learning.

[0024] Here, the predetermined time in step S3 will be described. The predetermined time can be set to a time when it can be determined that the vibration caused by the OT increase has decayed and the influence of the OT increase has decreased. This predetermined time can be set for each actual machine of the internal combustion engine 100 through experiments. By resuming the KCS learning in a state where the influence of the OT increase has decreased, the KCS learning accuracy can be maintained. Note that the predetermined time may be set to 0 ms, for example. In this case, the KCS learning control unit 51 can resume the KCS learning earlier.

[0025] When OT increment control is implemented, KCS learning control is stopped. As a result, the KCS learning value is not set due to the detection of vibrations in the internal combustion engine 100 caused by OT increment control, and the occurrence of a deviation in the KCS learning value can be avoided.

[0026] The above embodiments are merely examples for implementing the present invention, and the present invention is not limited thereto. It is obvious from the above description that various modifications of these examples are within the scope of the present invention, and various other embodiments are possible within the scope of the present invention.

Explanation of Reference Numerals

[0027] 50…ECU, 51…KCS learning control unit, 52…OT increment control unit, 53…catalyst temperature acquisition unit, 54…timer unit.

Claims

Claim 1 An ignition timing learning control unit that detects the presence or absence of knocking in an internal combustion engine, corrects the ignition timing so that the knocking is eliminated, and performs learning of the corrected ignition timing; A fuel injection amount increase control unit that increases the fuel injection amount to lower the temperature of a catalyst provided in an exhaust system or the like of the internal combustion engine based on the temperature of the catalyst; Comprising: When the fuel injection amount increase control unit is increasing the fuel injection amount, the ignition timing learning control unit stops the learning; A control device for an internal combustion engine.

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