JP2008215166A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify applicable man-hours for determining knocking, in a control device for an internal combustion engine. <P>SOLUTION: Actual torque Tc actually developed by the internal combustion engine 10 is acquired based on the output of a torque sensor 36. It is determined that knocking occurs when a torque difference Td between a target torque Tt used for torque demand control and the actual torque Tc is larger than a predetermined determining value Tth. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, for example, Patent Document 1 discloses a knock control device in which a knock sensor for detecting knock is provided on a wall surface of a cylinder block of an internal combustion engine. According to such a knock sensor, the pressure vibration of the combustion gas when the knock occurs can be detected as vibration of the cylinder block surface.

  For example, Patent Document 2 discloses a control device for an internal combustion engine that detects knock using an in-cylinder pressure sensor that detects an in-cylinder pressure of the internal combustion engine. According to such an in-cylinder pressure sensor, knock detection can be performed by directly acquiring the pressure vibration of the combustion gas at the time of occurrence of knock.

Japanese Patent Laid-Open No. 2002-21692 JP 2004-360562 A

  In the method of detecting knock using vibration (cylinder block vibration or pressure vibration) as in the prior art described above, the vibration level (determination value) for determining that a knock has occurred is determined based on the engine speed and load. It is necessary to adapt it by experiment etc. for each operating condition such as rate.

  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 simplify the man-hours required for knock determination.

According to a first aspect of the present invention, there is provided an actual torque acquisition means for acquiring an actual torque actually generated by the internal combustion engine
A knock occurrence detecting means for detecting the occurrence of knock based on a difference between a predetermined reference value and the actual torque;
It is characterized by providing.

Further, the second invention provides an actual torque acquisition means for acquiring an actual torque actually generated by the internal combustion engine,
A knock strength detecting means for detecting a knock strength based on a difference between a predetermined reference value and the actual torque;
It is characterized by providing.

Further, the third invention is an air-fuel ratio estimating means for estimating the air-fuel ratio of the exhaust gas of the internal combustion engine,
Actual torque acquisition means for acquiring the actual torque actually generated by the internal combustion engine;
An error detecting means for detecting an error between the estimated value by the air-fuel ratio estimating means and the actual air-fuel ratio based on a difference between a predetermined reference value and the actual torque;
It is characterized by providing.

Further, a fourth invention further comprises target torque setting means for setting a target torque of the internal combustion engine in any one of the first to third inventions,
The reference value is the target torque.

  According to the first aspect of the present invention, knock detection can be performed without using vibration caused by the occurrence of knock, and knock detection that can simplify the matching man-hours for knock determination can be realized.

  According to the second aspect of the present invention, it is possible to satisfactorily detect the strength of the knock without using the vibration caused by the occurrence of the knock.

  According to the third aspect of the present invention, it is possible to satisfactorily detect the air-fuel ratio estimation error based on the torque information of the internal combustion engine.

  According to the fourth aspect of the invention, it is possible to satisfactorily detect the occurrence of knock, the detection of knock intensity, or the estimation error of the air-fuel ratio based on the difference between the target torque and the actual torque of the internal combustion engine.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. A combustion chamber 12 is formed in the cylinder of the internal combustion engine 10. An intake passage 14 and an exhaust passage 16 communicate with the combustion chamber 12. An air flow meter 18 for detecting the amount of air flowing inside the intake passage 14, that is, the amount of intake air Ga flowing into the internal combustion engine 10 is arranged.

  A throttle valve 20 is disposed downstream of the air flow meter 18. The throttle valve 20 is an electronically controlled valve that is driven by a throttle motor based on the accelerator opening. A throttle position sensor 22 for detecting the throttle opening degree TA is disposed in the vicinity of the throttle valve 20.

  A fuel injection valve 24 for injecting fuel is disposed in the intake port of each cylinder. A spark plug 28 is attached to the cylinder head 26 of the internal combustion engine 10 so as to protrude into the cylinder.

  A catalyst 30 for purifying exhaust gas is disposed in the exhaust passage 16 of the internal combustion engine 10. Further, an air-fuel ratio (A / F) sensor 32 for detecting the exhaust air-fuel ratio at that position is disposed upstream of the catalyst 30.

  A torque sensor 36 for detecting an actual torque Tc actually generated by the internal combustion engine 10 is provided in the vicinity of the crankshaft 34 of the internal combustion engine 10. The torque sensor 36 detects the actual torque Tc by using distortion generated in the crankshaft 34 when torque is applied. A crank angle sensor 38 for detecting the engine speed Ne is provided in the vicinity of the crankshaft 34.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the sensor described above, the ECU 40 is connected to an accelerator opening sensor 42 for detecting the accelerator opening PA, and is also connected to the actuator described above.

  In addition, a model (herein referred to as “air model”) for estimating the in-cylinder charged air amount Mc sucked into the cylinder is constructed in the ECU 40. The air model here is a model for estimating the in-cylinder charged air amount Mc taken into the internal combustion engine 10. In this air model, the in-cylinder charged air amount Mc is calculated from the intake pressure Pe estimated based on the intake air amount Ga detected by the air flow meter 18 and various coefficients adapted according to operating conditions. . Since such an air model is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-263571, the detailed description thereof is omitted here. When the in-cylinder charged air amount Mc is obtained, the load factor (air filling rate) KL can be calculated. That is, according to such an air model, the relationship between the intake air amount Ga (intake pressure Pe) controlled by adjusting the throttle opening degree TA and the load factor KL can be obtained.

[Knock control system in the system of the first embodiment using torque demand control]
FIG. 2 is a block diagram for illustrating a knock control system KCS executed in the system shown in FIG. In the present embodiment, torque demand control for controlling the actual torque Tc of the internal combustion engine 10 is executed so as to obtain the torque actually requested (target torque Tt) based on the driver's accelerator operation or the like. In this torque demand control, the target torque Tt is calculated based on the accelerator opening PA, the engine speed Ne, and the like.

  In the torque demand control, as shown in FIG. 2, the target load factor KL is calculated from the target torque Tt based on the torque map that defines the relationship between the target torque Tt calculated as described above and the target load factor KL. Is done. Next, by calculating the air model in the reverse direction (air reverse model calculation) based on the calculated target load factor KL, the intake pressure Pe required for realizing the target load factor KL is obtained. As a result, the throttle opening degree TA required to control the intake pressure Pe (intake air amount Ga) can be calculated.

  In the torque demand control, the intake air amount Ga (intake pressure Pe) is controlled with the throttle opening TA calculated as described above, and the fuel is obtained so that the target air-fuel ratio for obtaining the target torque Tt can be obtained. The injection amount is controlled. As a result, the actual torque Tc of the internal combustion engine 10 can be controlled to be the target torque Tt.

  In the system of the present embodiment, the presence / absence of knocking is determined using a method described later with reference to FIG. When it is determined that knocking has occurred by the method shown in FIG. 4, as shown in FIG. 2, the torque between the actual torque Tc obtained by the torque sensor 36 and the target torque Tt calculated as described above. The difference ΔTrq (Td) is calculated. The ignition timing correction amount ΔSA is calculated from the torque difference ΔTrq based on the retard map that defines the relationship between the torque difference ΔTrq and the ignition timing correction amount ΔSA. Then, the final ignition timing is calculated by reflecting the ignition timing correction amount ΔSA in the optimal ignition timing MBT under the current operating conditions. In the knock control system KCS of the present embodiment, such a correction of the ignition timing avoids knocking when a knock is detected.

[Knock Determination Method of Embodiment 1]
FIG. 3 is a diagram showing a change in torque at the time of knock occurrence in relation to the ignition timing, and FIG. 4 is a diagram for explaining the knock determination method of the present embodiment. From FIG. 3, the actual torque Tc when knocking occurs (when controlled to the trace knock ignition timing) is lower than the actual torque Tc when knocking does not occur at the same ignition timing. I understand. When torque demand control is used, the actual torque Tc is controlled to coincide with the target torque Tt as described above. Therefore, in this embodiment, as shown in FIG. 4, the presence or absence of knocking is determined based on the torque difference Td between the target torque Tt and the actual torque Tc.

  FIG. 5 is a flowchart of a routine executed by the ECU 40 in the first embodiment in order to realize the above function. In the routine shown in FIG. 5, first, the target torque Tt during execution of torque demand control is referred to (obtained) (step 100). Next, the actual (generated) torque Tc is referred (acquired) based on the output of the torque sensor 36 (step 102).

  Next, a torque difference Td between the target torque Tt and the actual torque Tc each referred to as described above is calculated (step 104). Next, the current operating condition, more specifically, the current engine speed Ne and the load factor KL are referred to (step 106). Next, a determination value Tth corresponding to the current operating condition is calculated (step 108). This determination value Tth is a determination value used for knock determination.

  Next, it is determined whether or not the torque difference Td calculated as described above is larger than the determination value Tth (step 110). As a result, when it is determined that the torque difference Td> the determination value Tth is established, that is, when it can be determined that the deviation of the actual torque Tc from the target torque Tt is a certain level or more, it is determined that knocking has occurred. (Step 112). In this case, as shown in FIG. 2, control for avoiding knocking is separately performed by correcting the ignition timing based on the torque difference Td.

  In the routine shown in FIG. 5, next, the knock magnitude is estimated based on the torque difference Td (step 114). FIG. 6 shows the relationship between knock strength and torque difference Td. The knock strength increases as the torque difference Td increases. The ECU 40 stores the relationship as shown in FIG. 6 as a map based on actual measurement values or a statistical model based on simulation. In this step 114, referring to such a map or statistical model, the knock magnitude corresponding to the magnitude of the current torque difference Td is estimated.

  According to the routine shown in FIG. 5 described above, knock determination is performed using the relationship between the target torque Tt used in torque demand control (the “predetermined reference value” in the present invention) and the actual torque Tc. Can be done. Therefore, such a knock determination method can be used as an alternative or auxiliary method to a knock determination method using an acceleration sensor that detects vibration of a cylinder block or an in-cylinder pressure sensor that detects vibration of in-cylinder pressure.

  In addition, in the method of performing knock determination using the acceleration sensor or the in-cylinder pressure sensor described above, the vibration level (determination value) for determining that knock has occurred is tested for each operating condition such as engine speed and load factor. It is necessary to adapt by. On the other hand, according to the method of the present embodiment using the torque difference Td, such adaptation can be eliminated because the vibration caused by the occurrence of knocking is not used. That is, according to the method of the present embodiment, it is possible to realize knock determination that can simplify the adaptation man-hours for knock determination. In addition, according to the method of the present embodiment, it can be said that it is relatively less susceptible to the influence of sensor noise than the conventional method that uses the vibration detection result for knock determination, and it can avoid erroneous detection due to the noise. You can also

  Further, according to the above routine processing, the knock magnitude corresponding to the magnitude of the torque difference Td can be estimated. Therefore, by executing the correction of the ignition timing according to the estimated knock magnitude, the knock magnitude can be obtained. The corresponding ignition timing control can be realized.

  In the first embodiment described above, the actual torque Tc actually generated by the internal combustion engine 10 is directly obtained using the output of the torque sensor 36. The acquisition method is not limited to this, and the actual torque Tc may be estimated. That is, the actual torque Tc may be estimated from, for example, the rotational speed of the generator (alternator) and the current flowing through the stator coil of the generator.

In the first embodiment described above, the ECU 40 executes the process of step 102, so that the “actual torque acquisition means” in the first or second invention executes the process of steps 106 to 112. Thus, the “knock occurrence detecting means” in the first aspect of the present invention is realized.
Further, the “knock strength detecting means” according to the second aspect of the present invention is realized by the ECU 40 executing the process of step 114.
Further, the “target torque setting means” in the fourth aspect of the present invention is realized by the ECU 40 executing the processing of step 100 described above.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 9 described later instead of the routine shown in FIG. 5 using the hardware configuration shown in FIG.

[A / F estimation model]
FIG. 7 is a schematic diagram showing an A / F estimation model 50 built in the ECU 40 shown in FIG. As shown in FIG. 7, the A / F estimation model 50 can be constructed, for example, as a model using the above-described air model and fuel model. The fuel model here is actually sucked into the cylinder of the internal combustion engine 10 from the fuel amount fi injected by the fuel injection valve 24 in consideration of the existence of the fuel amount fw attached to the inner wall of the intake port. The fuel amount Fc is calculated. Since such a fuel model is described in detail in, for example, Japanese Patent Application Laid-Open No. 2005-9467, detailed description thereof is omitted here.

  According to the A / F estimation model 50 shown in FIG. 7, the air-fuel ratio A / F is calculated by dividing the in-cylinder intake fuel amount fc calculated by the fuel model from the in-cylinder charged air amount Mc calculated by the air model. An estimated value can be calculated.

[Characteristics of Embodiment 2]
The system of the second embodiment is characterized in that the A / F estimation error of the A / F estimation model 50 is detected based on the torque difference Td between the target torque Tt and the actual torque Tc.

  FIG. 8 is a diagram for explaining a method for detecting the A / F estimation error. The torque waveform shown in FIG. 8 represents the torque change when the air-fuel ratio is changed within a certain range under the same operating condition as when the current A / F estimated value was obtained. Is.

  If there is an estimation error in the air-fuel ratio estimated by the A / F estimation model 50, as shown in FIG. 8, the magnitude is the same as the actual torque generated under the control by the current A / F estimation value. The air / fuel ratio at which the torque can be obtained under the same operating conditions is the actual (true) air / fuel ratio. Here, the difference between the actual air-fuel ratio and the current A / F estimated value is referred to as “A / F estimation error”. If an A / F estimation error exists, a torque difference Td is generated between the target torque Tt calculated by torque demand control and the actual torque Tc, as shown in FIG.

  According to the relationship shown in FIG. 8, when the actual torque Tc is lower than the target torque Tt, when it can be determined that the air-fuel ratio has shifted to the lean side, the A / F estimation error increases as the torque difference Td increases. It can be said that it will grow. Therefore, in this embodiment, the A / F estimation error is calculated based on the torque difference Td. Furthermore, in this embodiment, the A / F estimation model 50 is learned based on the calculated A / F estimation error.

  FIG. 9 is a flowchart of a routine executed by the ECU 40 in the second embodiment to realize the above function. In FIG. 9, the same steps as those shown in FIG. 5 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 9, after the current operating condition is referred to in step 200, it is determined whether or not the operating condition is such that learning of the A / F estimation model 50 can be performed (step 202). In the case of a system that uses both the knock determination in the first embodiment described above and the detection of the A / F estimation error in the present embodiment at the same time, whether the cause of the torque difference Td is due to the occurrence of the knock or A / In order to specify whether the error is caused by the F estimation error, it is necessary to separate the operation region in which the knock determination and the A / F estimation error are detected.

  Therefore, in the present embodiment, knock determination is performed in a low-load high-rotation region where knocking is likely to occur, and an A / F estimation error is detected in other operation regions. For this reason, in this step 202, specifically, it is determined whether or not the current operation region is a region where the A / F estimation error is detected. / F estimation model 50 is determined to be an operation condition that can be executed. In the case of a system that does not use detection of A / F estimation error and knock determination at the same time, the A / F estimation model 50 may be learned in all operation regions.

  If it is determined in step 202 that the driving conditions are such that the learning of the A / F estimation model 50 can be executed, then the target torque Tt and the actual generated torque Tc are sequentially referred to (steps 100 and 102). The torque difference Td is calculated using these (step 104).

  Next, an A / F estimation error is calculated using the torque difference Td calculated as described above, and learning of the A / F estimation model 50 is executed (step 204). More specifically, the ECU 40 stores the relationship between the torque difference Td and the A / F estimation error for each operating condition, and the A / F estimation error is acquired according to the relationship. At this time, the output of the air-fuel ratio sensor 32 can be used to determine whether the actual air-fuel ratio is shifted to the rich side or the lean side with respect to the current A / F estimated value.

  In this step 204, learning of the A / F estimation model 50 is performed on the basis of the acquired A / F estimation error, using each coefficient in the air model or fuel model constituting the A / F estimation model 50 as an adjustment parameter. Executed. Note that, by learning the A / F estimation model 50, the subsequent estimated A / F value is corrected, and the fuel injection amount fi is corrected accordingly.

  According to the routine shown in FIG. 9 described above, it is possible to detect the A / F estimation error using the relationship between the target torque Tt used in the torque demand control and the actual torque Tc. Further, when the actual torque is estimated by the method as described above instead of the torque sensor 36, the A / F estimation error can be detected without a sensor.

  In the second embodiment described above, the A / F estimation model 50 corresponds to the “air-fuel ratio estimation means” in the third aspect of the present invention. Further, when the ECU 40 executes the process of step 102, the “actual torque acquisition means” in the third invention executes the processes of steps 104 and 204, thereby detecting “error detection” in the third invention. Each means is realized.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a block diagram for demonstrating the knock control system KCS performed with the system shown in FIG. It is a figure showing the torque change at the time of knock generation by the relation with ignition timing. It is a figure for demonstrating the knock determination method of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the relationship between knock strength and torque difference Td. It is a schematic diagram which shows the A / F estimation model constructed | assembled in ECU shown in FIG. It is a figure for demonstrating the detection method of the A / F estimation error in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Intake passage 16 Exhaust passage 18 Air flow meter 20 Throttle valve 22 Throttle position sensor 24 Fuel injection valve 28 Spark plug 32 Air-fuel ratio sensor 34 Crankshaft 36 Torque sensor 38 Crank angle sensor 40 ECU (Electronic Control Unit)
42 Accelerator position sensor

Claims (4)

Actual torque acquisition means for acquiring the actual torque actually generated by the internal combustion engine;
A knock occurrence detecting means for detecting the occurrence of knock based on a difference between a predetermined reference value and the actual torque;
A control device for an internal combustion engine, comprising: Actual torque acquisition means for acquiring the actual torque actually generated by the internal combustion engine;
A knock strength detecting means for detecting a knock strength based on a difference between a predetermined reference value and the actual torque;
A control device for an internal combustion engine, comprising: Air-fuel ratio estimating means for estimating the air-fuel ratio of the exhaust gas of the internal combustion engine;
Actual torque acquisition means for acquiring the actual torque actually generated by the internal combustion engine;
An error detecting means for detecting an error between the estimated value by the air-fuel ratio estimating means and the actual air-fuel ratio based on a difference between a predetermined reference value and the actual torque;
A control device for an internal combustion engine, comprising: A target torque setting means for setting a target torque of the internal combustion engine;
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the reference value is the target torque.

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