JP2008190500A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid knocking without causing torque fluctuation during the occurrence of knocking. <P>SOLUTION: Knocking is detected by a knocking detection means such as a knock sensor. When knocking occurs, ignition timing of an internal combustion engine is changed to a retard side for eliminating knocking. Here, the ignition timing is determined so that torque of the internal combustion engine after retard of the ignition timing is equal to torque of the internal combustion engine during the occurrence of knocking. Thereby, fluctuation of output torque of the internal combustion engine is prevented before and after ignition timing retard control for eliminating knocking. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for preventing knocking of an internal combustion engine.

  It is known that abnormal combustion called knocking occurs in an internal combustion engine. In general, when knocking occurs, control is performed to retard knocking by retarding the ignition timing of the internal combustion engine. An example of such control is described in Patent Document 1.

  Patent Document 2 describes a technique for reducing engine torque when knocking occurs in a hybrid vehicle.

Japanese Patent Laid-Open No. 5-164032 Japanese Patent Laid-Open No. 10-23609

  In the method of Patent Document 1, the output torque of the internal combustion engine is reduced by retarding the ignition timing when knocking occurs. Therefore, since the torque changes before and after the occurrence of knocking, the driver may feel uncomfortable.

  On the other hand, according to the method of Patent Document 2, the engine torque can be reduced when knocking occurs, and the insufficient torque can be compensated by the motor output. However, the method of Patent Document 2 requires a device that generates torque in addition to the engine, such as a hybrid vehicle.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can avoid knocking without causing torque fluctuation when knocking occurs. .

  In one aspect of the present invention, a control device for an internal combustion engine includes a knocking detection unit that detects knocking in the internal combustion engine, and an ignition timing control unit that retards the ignition timing of the internal combustion engine when knocking is detected. The ignition timing control means controls the ignition timing so that the torque of the internal combustion engine after retarding the ignition timing becomes equal to the torque of the internal combustion engine when knocking occurs.

  In the control apparatus for an internal combustion engine described above, knocking is detected by knocking detection means such as a knock sensor. When knocking occurs, the ignition timing of the internal combustion engine is changed to the retard side in order to eliminate knocking. The ignition timing to be changed here is determined so that the torque of the internal combustion engine after retarding the ignition timing becomes equal to the torque of the internal combustion engine at the time of occurrence of knocking. This prevents the output torque of the internal combustion engine from fluctuating before and after the ignition timing is retarded to eliminate knocking, so that knocking can be eliminated without causing the driver to feel uncomfortable.

  In one aspect of the control device for the internal combustion period, the ignition timing control means advances the ignition timing when knocking is not detected after the ignition timing is retarded. In this aspect, after the knocking is eliminated by the retard control of the ignition timing, the ignition timing is returned to the normal advance side position, and the internal combustion engine is operated in a state with good original combustion efficiency.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 1 shows a schematic configuration of a control device for an internal combustion engine according to the present embodiment. In FIG. 1, solid arrows indicate intake / exhaust flow, and broken arrows indicate signal flow.

  The internal combustion engine control device 1 includes an internal combustion engine (engine) 5, an intake passage 2 and an exhaust passage 6 connected to the engine 5, an ECU 10, and an accelerator opening sensor 11.

  The accelerator opening sensor 11 detects an accelerator opening corresponding to the amount of depression of an accelerator pedal (not shown) and supplies a detection signal S11 to the ECU 10.

  An air flow meter 3 and a throttle valve 4 are provided in the intake passage 2. The air flow meter 3 measures the intake air amount Q flowing through the intake passage and supplies a detection signal S3 indicating the intake air amount Q to the ECU 10. The throttle valve 4 is opened / closed according to the accelerator opening degree or the like by a control signal S4 supplied from the ECU 10 to control the intake air amount Q supplied to the engine 5.

  The engine 5 is provided with a fuel injection valve 7, an ignition device 8, a crank angle sensor 9, and a knock sensor 12. The fuel injection valve 7 injects fuel in response to a control signal S7 supplied from the ECU 10, and the ignition device 8 changes to the air-fuel mixture sealed in the cylinder at the ignition timing indicated by the control signal S8 supplied from the ECU 10. Ignite. The crank angle sensor 9 supplies the ECU 10 with a detection signal S9 indicating the engine speed NE and the like by detecting the rotation of the crankshaft.

  Knock sensor 12 detects the occurrence of knocking in engine 5 and supplies detection signal S12 to ECU 10. The ECU 10 determines the presence or absence of knocking based on the detection signal S12. For example, the ECU 10 compares the level of the detection signal output from the knock sensor 12 with a predetermined level, and determines that knocking has occurred when the number exceeding the predetermined level exceeds the predetermined number. For the knocking determination, a known method other than the above may be applied.

  The ECU 10 is an electronic control unit that includes a CPU, a ROM, and a RAM (not shown) and controls the entire operation of the control device 1 for the internal combustion engine. In the above configuration, the knocking detection means in the present invention is configured by the knock sensor 12 and the ECU 10, and the ignition timing control means in the present invention is configured by the ECU 10.

  Next, ignition timing control when knocking occurs according to the present invention will be described.

  Generally, when knocking occurs, the output torque of the engine 5 (hereinafter simply referred to as “torque”) decreases. FIG. 2 shows the relationship between the knocking amount and the torque ratio when knocking occurs. In FIG. 2, the horizontal axis indicates the knocking amount, and the vertical axis indicates the torque ratio. The torque ratio indicates the ratio of torque in each knocking amount when knocking occurs when the torque of the engine 5 when knocking does not occur is “1”. As shown in the figure, basically, when the knocking amount increases, the torque decreases and the torque ratio also decreases.

  Normally, the torque of the engine 5 is controlled to be a target torque determined according to the operating state of the engine (this is referred to as “normal torque control”). Specifically, the ECU 10 determines a target torque based on, for example, the accelerator opening, the engine speed NE, the intake air amount Q, and controls the throttle opening and the ignition timing so that the target torque can be obtained.

  FIG. 3 shows the relationship between ignition timing and torque at a certain throttle opening. In FIG. 3, a graph C1 shows torque characteristics when knocking has not occurred, and a graph C2 shows torque characteristics when knocking has occurred. MBT in the figure is a point where the graph C1 takes the maximum value, and indicates the ignition timing at which the maximum torque is generated. Normally, the engine 5 is controlled to ignite in MBT. As shown in the graph C1, when knocking has not occurred, basically the torque increases when the ignition timing is advanced, and the torque decreases when the ignition timing is retarded.

  If knocking occurs when the torque is controlled with respect to the target torque by the normal torque control, the torque decreases as shown in FIG. 2, and the required torque cannot be obtained. In this case, a torque increase request by air amount control or the like is made according to a request from the driver or the like, but at the same time, the ECU 10 executes control to retard the ignition timing in order to eliminate knocking.

  In the state where knocking does not occur, the torque decreases when the ignition timing is retarded as shown in the graph C1, but in the state where knocking occurs, the torque characteristic with respect to the ignition timing as shown in the graph C2. There is a region A where is reversed. That is, when the ignition timing is MBT, the operating point is P0 on the graph C1 when knocking does not occur. However, when knocking occurs, the torque decreases from Tn to Tx, and the operating point becomes P1 on the graph C2. Here, if the ignition timing is retarded to eliminate knocking, the operating point P1 enters the region A. Region A is a region where the torque increases as a result because knocking is reduced by the retard of the ignition timing. For this reason, the torque value is Tx at the operating point P1 when knocking occurs, but if the ignition timing is subsequently retarded to prevent knocking, the torque temporarily increases according to the graph C2. . Therefore, the engine 5 outputs a torque different from that at the time of occurrence of knocking, that is, a torque larger than that at the time of occurrence of knocking, and the driver may feel uncomfortable.

  Therefore, in the present invention, when the ignition timing is retarded when knocking occurs, the ignition timing is retarded until the ignition timing at which the same torque as when knocking occurs is obtained. In the example of FIG. 3, when knocking occurs at the ignition timing MBT, the operating point at that time is P1, and the torque is Tx. Therefore, on the torque characteristic C2 at the time of occurrence of knocking, an operating point P2 at which a torque Tx equal to that at the time of occurrence of knocking is found is found, and the ignition timing is retarded to the ignition timing ITx corresponding thereto. As a result, even when the retard angle control for eliminating knocking is performed, the torque output by the engine 5 is equal to that at the time of occurrence of knocking, so that the driver does not feel uncomfortable.

  Next, specific processing in this case will be described. First, the knocking amount-torque ratio relationship illustrated in FIG. 2 is prepared in advance in the form of a map or the like. Further, the relationship between the ignition timing and the torque illustrated in FIG. 3, that is, the torque characteristics at the time of no knocking and the occurrence of knocking are prepared in the form of a map or the like.

  In the normal state, normal torque control is executed so as to follow the target torque determined according to the driving state of the vehicle as described above. Therefore, in a state where torque control is correctly executed, the torque of the engine 5 matches the target torque, and the ECU 10 holds the value of the target torque. In the example of FIG. 3, the ignition timing is MBT, the operating point is P0, and the torque is Tn in a state where normal torque control is being executed.

  Here, when knocking occurs, the torque of the engine 5 decreases. The ECU 10 can calculate the reduced torque due to knocking according to the relationship of knocking amount-torque ratio illustrated in FIG. Specifically, the torque at the time of knocking is calculated by multiplying the current torque by the torque ratio corresponding to the detected knocking amount. In the example of FIG. 3, the torque when this knocking occurs is Tx.

  Next, the ECU 10 refers to a torque characteristic C2 at the time of occurrence of knocking illustrated in FIG. 3, and determines an ignition timing at which a torque equivalent to the torque Tx at the time of occurrence of knocking is obtained. That is, the ignition timing is retarded to the ignition timing ITx corresponding to the operating point P2. Thereby, knocking can be eliminated by retarding the ignition timing without causing a torque difference from the time of occurrence of knocking.

  In this state, the ignition timing is greatly retarded and the combustion efficiency is poor. Therefore, if knocking is eliminated by this retard angle control, the ECU 10 promptly controls the throttle to close and advances the ignition timing, and performs control to shift to the original engine operating state with good combustion efficiency.

  FIG. 4 is a flowchart of the ignition timing control when the above-described knocking occurs. This process is executed under the initiative of the ECU 10 based on the output of the knock sensor 12 or the like.

  First, the ECU 10 determines whether or not knocking has occurred based on the detection signal S12 from the knock sensor 12 (step S101). When knocking has not occurred (step S101: No), the ECU 10 executes normal torque control (step S105).

  On the other hand, if knocking has occurred (step S101; Yes), the ECU 10 estimates the torque Tx at the time of knocking. Specifically, as described above, the ECU 10 estimates the torque at the time of occurrence of knocking based on the target torque at the time of occurrence of knocking and the relationship between the knocking amount and the torque illustrated in FIG.

  Next, the ECU 10 determines a retard side ignition timing ITx that provides a torque equal to the torque Tx at the time of occurrence of knocking based on the torque characteristic C2 at the time of occurrence of knocking illustrated in FIG. 3 (step S103). Then, the ECU 10 retards the ignition timing until the determined ignition timing ITx (step S104). Knocking is eliminated by this retarded ignition timing. Further, at the ignition timing ITx, the engine 5 outputs a torque equal to the torque Tx at the time of knocking occurrence, so that the driver does not feel discomfort due to the torque difference.

  Since the process shown in FIG. 4 is periodically executed, if knocking is eliminated due to the retard of the ignition timing in step S104, the determination result in step S101 is No in the next process, and the normal torque Control is executed. That is, when knocking is eliminated by the process of FIG. 4, the ignition timing is changed to the normal advance side position, and the engine 5 is operated in an operating state with good combustion efficiency.

1 shows a configuration of a control device for an internal combustion engine according to an embodiment of the present invention. It is a graph which shows the relationship between a knocking amount and a torque ratio. It is a graph which shows the relationship between ignition timing and engine output torque. It is a flowchart of ignition timing control at the time of occurrence of knocking.

Explanation of symbols

3 Air flow meter 4 Throttle valve 5 Engine (internal combustion engine)
7 Fuel Injection Valve 8 Ignition System 9 Crank Angle Sensor 10 ECU
12 Knock sensor

Claims (2)

A control device for an internal combustion engine,
Knocking detection means for detecting knocking in the internal combustion engine;
Ignition timing control means for retarding the ignition timing of the internal combustion engine when knocking is detected, and
The ignition timing control means controls the ignition timing so that the torque of the internal combustion engine after retarding the ignition timing becomes equal to the torque of the internal combustion engine at the time of occurrence of knocking. apparatus.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition timing control means advances the ignition timing when knocking is not detected after the ignition timing is retarded.

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