Control device for internal combustion engines

Abstract

To provide a control device of an internal combustion engine capable of reducing a weight by reducing the number of components, and quickly determining whether a catalyst is deteriorated or not.SOLUTION: A control device of an internal combustion engine applied to a vehicle including a catalyst for clarifying an exhaust gas, an EGR device for recirculating the exhaust gas from the downstream of the catalyst to an intake side of the internal combustion engine, and a knocking sensor for detecting knocking generated in the internal combustion engine includes: an ignition timing control portion for controlling an ignition timing of the internal combustion engine; and a catalyst deterioration diagnosing portion for determining whether the catalyst is deteriorated or not. The ignition timing control portion advances the ignition timing in a case when the knocking is not generated in a situation that an operation region of the internal combustion engine is a prescribed knocking control region, and the catalyst deterioration diagnosing portion determines the deterioration of the catalyst when the advance amount of the ignition timing is a prescribed value or more in a case when EGR is performed, and the operation region of the internal combustion engine is a prescribed knocking control region.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a catalyst diagnosis device for an internal combustion engine including a pre-air-fuel ratio sensor disposed upstream of a catalyst and a post-air-fuel ratio sensor disposed downstream of the catalyst. Based on the relationship between the output signals of the pre-air-fuel ratio sensor and the post-air-fuel ratio sensor, a catalyst diagnosis device for an internal combustion engine that determines the deterioration of the catalyst is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional catalyst diagnosis device for an internal combustion engine, when diagnosing the deterioration of the catalyst, an air-fuel ratio sensor is arranged in each of the exhaust pipes on the upstream side and the downstream side of the catalyst, and it is determined whether the catalyst has deteriorated based on the deviation and ratio using the output signals of these air-fuel ratio sensors. Therefore, when diagnosing the deterioration of the catalyst, at least two air-fuel ratio sensors are required.

[0005] Therefore, in the conventional catalyst diagnosis device for an internal combustion engine, an increase in the calculation time required to determine whether the catalyst has deteriorated and an increase in the number of parts and the engine weight due to the use of two air-fuel ratio sensors have occurred.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for an internal combustion engine that can quickly determine whether a catalyst has deteriorated while reducing the number of parts and achieving weight reduction.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides a control device for an internal combustion engine applicable to a vehicle equipped with a catalyst for purifying exhaust gas discharged from an internal combustion engine, an EGR device for recirculating exhaust gas from downstream of the catalyst to the intake side of the internal combustion engine, and a knock sensor for detecting knocking occurring in the internal combustion engine, comprising: an ignition timing control unit for controlling the ignition timing of the internal combustion engine; and a catalyst deterioration diagnosis unit for determining whether the catalyst is deteriorated, wherein the ignition timing control unit advances the ignition timing when the operating range of the internal combustion engine is in a predetermined knock control range and no knocking has occurred, and the catalyst deterioration diagnosis unit determines that the catalyst is deteriorated when the amount of ignition timing advance is greater than or equal to a predetermined value when the exhaust gas is recirculated by the EGR device and the operating range of the internal combustion engine is in the predetermined knock control range. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a control device for an internal combustion engine that can quickly determine whether or not the catalyst is degraded, while reducing the number of parts and thus reducing weight. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of a vehicle to which a control device for an internal combustion engine according to one embodiment of the present invention is applied. [Figure 2] Figure 2 is a flowchart showing the flow of the catalyst degradation diagnosis process performed by the control device for an internal combustion engine according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] A control device for an internal combustion engine according to one embodiment of the present invention is an internal combustion engine control device applied to a vehicle equipped with a catalyst for purifying exhaust gas discharged from an internal combustion engine, an EGR device for recirculating exhaust gas from downstream of the catalyst to the intake side of the internal combustion engine, and a knock sensor for detecting knocking occurring in the internal combustion engine, and comprises an ignition timing control unit for controlling the ignition timing of the internal combustion engine, and a catalyst deterioration diagnosis unit for determining whether or not the catalyst is deteriorated, wherein the ignition timing control unit advances the ignition timing when the operating range of the internal combustion engine is in a predetermined knock control range and no knocking has occurred, and the catalyst deterioration diagnosis unit determines that the catalyst is deteriorated when exhaust gas is recirculated by the EGR device and the operating range of the internal combustion engine is in a predetermined knock control range and the amount of ignition timing advance is greater than or equal to a predetermined value. As a result, the control device for an internal combustion engine according to one embodiment of the present invention can quickly determine whether or not the catalyst is deteriorated while reducing the number of parts and achieving weight reduction. [Examples]

[0011] Hereinafter, a vehicle to which a control device for an internal combustion engine according to one embodiment of the present invention is applied will be described with reference to the drawings.

[0012] As shown in Figure 1, a vehicle 1 according to one embodiment of the present invention is configured to include an internal combustion engine 2, a catalyst 3, and an EGR device 4.

[0013] Internal combustion engine 2 is, for example, a gasoline engine with three inline cylinders, from cylinder #1 to cylinder #3. Internal combustion engine 2 is a so-called four-stroke gasoline engine in which the piston reciprocates within the cylinders, performing a series of four strokes: intake, compression, expansion, and exhaust. Note that the number of cylinders in internal combustion engine 2 is not limited to three.

[0014] Each cylinder of the internal combustion engine 2 is equipped with an ignition device 21 consisting of a spark plug. The ignition timing of the ignition device 21 is adjusted via an igniter (not shown) based on a signal from the ECM 50, which will be described later.

[0015] The internal combustion engine 2 is provided with a knock sensor 22 for detecting knocking occurring in the internal combustion engine 2. The knock sensor 22 is installed, for example, on the cylinder block of the internal combustion engine 2. The knock sensor 22 detects the shock or vibration caused by knocking and outputs a voltage signal corresponding to the magnitude of the detected shock or vibration to the ECM 50.

[0016] An intake pipe 24 is connected to the intake side of the internal combustion engine 2 via an intake manifold 23. An exhaust pipe 26 is connected to the exhaust side of the internal combustion engine 2 via an exhaust manifold 25.

[0017] The catalyst 3 is provided in the exhaust pipe 26 and is a three-way catalyst for purifying the exhaust gas discharged from the internal combustion engine 2.

[0018] The EGR device 4 includes an EGR pipe 41 connecting the exhaust pipe 26 on the downstream side of the catalyst 3 and the intake pipe 24 on the intake side of the internal combustion engine 2, and an EGR valve and an EGR cooler (not shown). The EGR device 4 is a device for recirculating exhaust gas from the downstream side of the catalyst 3 to the intake side of the internal combustion engine 2.

[0019] The internal combustion engine 2 configured as described above is controlled in its operating state by an ECM (Electronic Control Module) 50 as a control device for the internal combustion engine. The ECM 50 includes, for example, a microcomputer equipped with a CPU, RAM, ROM, input / output interfaces, etc. The CPU uses the temporary storage function of the RAM and performs signal processing according to a program pre-stored in the ROM. Various control constants and various maps are pre-stored in the ROM.

[0020] On the input side of the ECM 50, various sensors including the knock sensor 22 are connected via a communication line conforming to a standard such as CAN.

[0021] On the output side of the ECM50, various devices such as the ignition device 21, an injector not shown, and a throttle valve are connected via a communication line conforming to a standard such as CAN.

[0022] The ECM50 controls the ignition device 21, the injector, and the throttle valve based on operations by the driver and the operating state of the internal combustion engine 2. Specifically, the ECM50 has a function as an ignition timing control unit 51 that controls the ignition timing. Further, the ECM50 adjusts the fuel injection timing and the intake air amount by controlling the injector and the throttle valve.

[0023] When the operating region of the internal combustion engine 2 is in the knock control region, the ECM50 performs knock control to retard or advance the ignition timing according to the occurrence situation of knocking in the internal combustion engine 2. The ECM50 determines that the operating region is in the knock control region when the operating region of the internal combustion engine 2 is in a predetermined engine load region, for example, a high load and low rotation or medium rotation region.

[0024] Specifically, when knocking does not occur in the internal combustion engine 2 in the knock control region, the ECM50 advances the ignition timing. Thereby, the output of the internal combustion engine 2 can be improved.

[0025] On the contrary, when knocking occurs in the internal combustion engine 2 in the knock control region, the ECM50 retards the ignition timing. Thereby, knocking is suppressed.

[0026] When the operating state of the internal combustion engine 2 is in a predetermined EGR operating region, the ECM50 controls the EGR device 4 to reflux exhaust gas from the downstream of the catalyst 3 to the intake side of the internal combustion engine 2.

[0027] The ECM50 functions as a catalyst degradation diagnosis unit 52 that determines whether the catalyst 3 is degraded when exhaust gas is recirculated by the EGR device 4, i.e., when the EGR is operating, and the operating range of the internal combustion engine 2 is within a predetermined knock control range.

[0028] The ECM50 determines that the catalyst 3 is degraded if, while the EGR is operating and within a predetermined knock control range, the ignition timing advance amount is greater than or equal to a predetermined value TH for a predetermined period of time.

[0029] Here, we will explain why the deterioration of catalyst 3 can be determined from the amount of ignition timing advance, as described above.

[0030] When catalyst 3 deteriorates, the reduction of exhaust gas in catalyst 3 becomes insufficient, and the reaction heat decreases. As a result, the exhaust gas temperature downstream of catalyst 3 decreases, increasing the density of EGR gas, and the actual EGR amount increases compared to the estimated EGR amount. This reduces the oxygen concentration in the intake air, making knocking less likely, and thus allowing for advancement of the ignition timing in the knock control region, resulting in an advance of the ignition timing.

[0031] Thus, when catalyst 3 deteriorates, the ignition timing advances. Therefore, if the amount of ignition timing advance exceeds the predetermined value TH during EGR operation, it can be determined that catalyst 3 is deteriorated.

[0032] Therefore, in this embodiment, the ECM50 can determine that the catalyst 3 is degraded when the above-described conditions are met.

[0033] The predetermined value TH is the lower limit of the ignition timing advance that can be determined to be caused by the deterioration of catalyst 3, and is determined experimentally in advance and stored in the ROM of ECM50.

[0034] Next, referring to the flowchart in Figure 2, the process flow for catalyst degradation diagnosis performed by the ECM50 according to this embodiment will be explained.

[0035] As shown in Figure 2, the ECM 50 determines whether or not EGR is operating, that is, whether or not exhaust gas is being recirculated by the EGR device 4 (step S1). The ECM 50 can determine whether or not EGR is operating, for example, by determining whether or not the operating state of the internal combustion engine 2 is in a predetermined EGR operating range.

[0036] If the ECM50 determines in step S1 that the EGR is not operating, it repeats the process in step S1.

[0037] If the ECM50 determines in step S1 that EGR is operating, it determines whether the operating range of the internal combustion engine 2 is within a predetermined knock control range (step S2). If the ECM50 determines in step S2 that the operating range of the internal combustion engine 2 is not within the predetermined knock control range, it returns to step S1.

[0038] If the ECM50 determines in step S2 that the operating range of the internal combustion engine 2 is within a predetermined knock control range, it starts the catalyst degradation diagnosis (step S3).

[0039] Next, the ECM50 determines whether the ignition timing advance amount is equal to or greater than a predetermined value TH (step S4). If the ECM50 determines in step S4 that the ignition timing advance amount is not equal to or greater than the predetermined value TH, it determines that the catalyst 3 is normal (step S7) and terminates the catalyst degradation diagnosis process.

[0040] If the ECM50 determines in step S4 that the advance amount of the ignition timing is equal to or greater than a predetermined value TH, it determines in step S5 whether a predetermined time has elapsed since it was determined in step S4 that the advance amount of the ignition timing is equal to or greater than a predetermined value TH.

[0041] If ECM50 determines in step S5 that the predetermined time has not elapsed, it returns to step S4.

[0042] If the ECM50 determines in step S5 that a predetermined time has elapsed, it determines that the catalyst 3 is degraded (step S6) and terminates the catalyst degradation diagnosis process. If it is determined that the catalyst 3 is degraded, the driver is notified of the degradation, for example, by the illumination of a warning lamp.

[0043] As described above, the control device for the internal combustion engine according to this embodiment is configured to determine that the catalyst is degraded when the amount of ignition timing advance is greater than or equal to a predetermined value TH, while exhaust gas is being recirculated by the EGR device 4 and the operating range of the internal combustion engine 2 is in a predetermined knock control range.

[0044] This configuration allows the control device for the internal combustion engine according to this embodiment to determine whether the catalyst 3 is degraded more quickly than, for example, when determining whether the catalyst is degraded using the detection results of an air-fuel ratio sensor. In other words, it can quickly determine whether the catalyst 3 is degraded.

[0045] Furthermore, since the detection results of the air-fuel ratio sensor are not required for catalyst degradation diagnosis, the air-fuel ratio sensor is not needed, thereby reducing the number of parts. In addition, by reducing the number of parts, the weight of the internal combustion engine 2 can be reduced.

[0046] Furthermore, the control device for the internal combustion engine according to this embodiment determines that the catalyst 3 is degraded if the ignition timing advance amount is greater than or equal to a predetermined value TH for a predetermined period of time, thereby preventing misjudgments.

[0047] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of symbols]

[0048] 1 vehicle 2 Internal Combustion Engine 3 Catalyst 4 EGR device 21 Ignition system 22 Knock Sensor 50 ECM 51 Ignition timing control unit 52 Catalyst Degradation Diagnosis Unit

Claims

1. A control device for an internal combustion engine, applicable to a vehicle equipped with a catalyst for purifying exhaust gas discharged from an internal combustion engine, an EGR device for recirculating exhaust gas from downstream of the catalyst to the intake side of the internal combustion engine, and a knock sensor for detecting knocking occurring in the internal combustion engine, An ignition timing control unit for controlling the ignition timing of the internal combustion engine, The system includes a catalyst degradation diagnostic unit that determines whether or not the catalyst has deteriorated, The ignition timing control unit advances the ignition timing when the operating range of the internal combustion engine is in a predetermined knock control range and knocking does not occur. The catalyst degradation diagnostic unit is characterized in that, when the exhaust gas is recirculated by the EGR device and the operating range of the internal combustion engine is in the predetermined knock control range, the catalyst is determined to be degraded when the advance amount of the ignition timing is greater than or equal to a predetermined value.

2. The control device for an internal combustion engine according to claim 1, characterized in that the catalyst degradation diagnostic unit determines that the catalyst is degraded if the advance amount of the ignition timing is greater than or equal to the predetermined value for a predetermined period of time.

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