JP2005201163A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable appropriate compensation of a deviation of an output of a cylinder inner pressure sensor from a proper value, thereby attaining appropriate control of an internal combustion engine. <P>SOLUTION: The control device 1 comprises ECU 2, and the ECU 2 controls the internal combustion engine 3 in accordance with an output P of a cylinder inner pressure sensor 11 which detects the inner pressure in a cylinder (steps 1 to 3), and corrects the output P of the cylinder inner pressure sensor 11 in accordance with an intake air amount parameter PBA indicating an intake air amount detected and an air/ fuel ratio AFR of an air fuel mixture (steps 12 and 14 to 22). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine control device that controls an internal combustion engine in accordance with an output of an in-cylinder pressure sensor that detects an in-cylinder pressure.

  Conventionally, what was disclosed by patent document 1, for example is known as this kind of control apparatus. This control device is applied to a diesel engine, and an in-cylinder pressure sensor configured by a piezoelectric element, a fuel injection nozzle that injects fuel into the cylinder, and a fuel injection nozzle according to the output of the in-cylinder pressure sensor. And a control unit for controlling the fuel injection amount. The in-cylinder pressure sensor is provided in the glow plug, and detects the in-cylinder pressure acting on the glow plug. The control unit calculates the required torque required for the internal combustion engine and calculates the actual torque of the engine according to the output of the in-cylinder pressure sensor. Further, the calculated actual torque is compared with the required torque, and the fuel injection amount is controlled so that the actual torque matches the required torque according to the comparison result.

  However, the conventional control device has a problem that the fuel injection amount cannot be appropriately controlled. That is, since a high in-cylinder pressure always acts on the in-cylinder pressure sensor used as described above during the operation of the engine, the in-cylinder pressure sensor deteriorates over time and its detection accuracy decreases. Unavoidable. In addition, a piezoelectric element type in-cylinder pressure sensor generally has a characteristic that its output changes according to the temperature due to the pyroelectric property of the piezoelectric element even if the acting pressure is constant. On the other hand, the in-cylinder pressure sensor is provided in the glow plug and is directly affected by the temperature of the engine, so that an appropriate output may not be obtained. Furthermore, the output of the in-cylinder pressure sensor may slightly deviate from the actual in-cylinder pressure due to individual differences due to mass production of the in-cylinder pressure sensor. On the other hand, in the above control device, the fuel injection amount is controlled in accordance with the output of the in-cylinder pressure sensor including the deviation from the appropriate value as described above, so that there is a possibility that it cannot be controlled appropriately.

  The present invention has been made in order to solve the above-described problems, and can appropriately compensate for a deviation from an appropriate value of the output of the in-cylinder pressure sensor, thereby appropriately controlling the internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine.

JP-A-9-68082

  In order to achieve the above object, a control device 1 for an internal combustion engine according to a first aspect of the present invention includes an in-cylinder pressure sensor 11 that detects an in-cylinder pressure that is a pressure in a cylinder C, and an output P of the in-cylinder pressure sensor 11. Accordingly, the control means (the ECU 2 in the embodiment (hereinafter the same in this section), steps 1 to 3 in FIG. 2) for controlling the internal combustion engine 3 and the intake air amount parameter (intake air) representing the intake air amount sucked into the cylinder C Intake air amount parameter detecting means (intake pipe absolute pressure sensor 12) for detecting the in-pipe absolute pressure PBA) and an air-fuel ratio sensor (LAF sensor) for detecting the air-fuel ratio (detected air-fuel ratio AFR) of the air-fuel mixture supplied to the cylinder C 13) and correction means (ECU 2, steps 12, 14 to 22 in FIG. 3) for correcting the output P of the in-cylinder pressure sensor 11 in accordance with the detected intake air amount parameter and the air-fuel ratio. And it features.

  According to this control device for an internal combustion engine, the internal combustion engine is controlled by the control means in accordance with the output of the in-cylinder pressure sensor. Further, the output of the in-cylinder pressure sensor is corrected by the correction means according to the detected intake air amount parameter and the air-fuel ratio. In general, the larger the intake air amount and the smaller the air / fuel ratio, the greater the pressure generated in the cylinder by the combustion of the air / fuel mixture. Therefore, the intake air amount and the air / fuel ratio have a close correlation with the in-cylinder pressure. In contrast, according to the present invention, the output of the in-cylinder pressure sensor is set according to the intake air amount parameter representing the intake air amount and the air-fuel ratio, that is, according to a parameter closely correlated with the in-cylinder pressure. Since the correction is performed, it is possible to appropriately compensate for the deviation from the appropriate value of the output of the in-cylinder pressure sensor. Therefore, it is possible to appropriately control the internal combustion engine.

According to a second aspect of the present invention, in the control apparatus 1 for an internal combustion engine according to the first aspect, the correction means provides a correction term (correction coefficient K _i ) for correcting the output P of the in-cylinder pressure sensor 11. , A correction term setting means (ECU 2, steps 14 to 22 in FIG. 3) that is set according to the intake air amount parameter and the air-fuel ratio, and prohibition of prohibiting updating of the correction term when the air-fuel ratio is not within a predetermined range Means (ECU2, step 13 in FIG. 3).

  According to this configuration, the correction term for correcting the output of the in-cylinder pressure sensor is set by the correction term setting means in accordance with the detected intake air amount parameter and the air-fuel ratio. Further, when the detected air-fuel ratio is not within a predetermined range, the update of the correction term is prohibited by the prohibiting means. In general, the detection accuracy of a sensor that detects the air-fuel ratio tends to be high when the air-fuel ratio is within a certain range and decreases outside that range. Therefore, for example, the correction term is updated using the detected air-fuel ratio only in a situation where high detection accuracy of the air-fuel ratio sensor can be obtained by setting the predetermined range to the specific range. Correction by this correction term can be performed more appropriately.

1 is a diagram illustrating a schematic configuration of a control device according to an embodiment of the present invention and an internal combustion engine to which the control device is applied. It is a flowchart which shows the main routine of a fuel-injection control process. It is a flowchart which shows the subroutine of the illustration average effective pressure calculation process of FIG. Is a diagram illustrating an example of a IMEP_AFR _i table used in the processing of FIG.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the control device 1 includes an ECU 2, and the engine 3 includes four cylinders C (1st to 4th cylinders C # 1 to C # 4) (only one is illustrated). This is an inline 4-cylinder type diesel engine, which is mounted on a vehicle (not shown).

  A fuel injection valve (hereinafter referred to as “injector”) 4 (only one is shown) is attached to the cylinder head of each cylinder C of the engine 3 so as to face the combustion chamber. Each injector 4 is connected to a high pressure pump (both not shown) via a common rail. The high-pressure pump boosts the fuel in a fuel tank (not shown) to a high pressure under the control of the ECU 2 and then sends the fuel to the injector 4 through the common rail. The injector 4 injects this fuel into the combustion chamber. The fuel injection time TOUT that is the valve opening time of the injector 4 is controlled by a drive signal from the ECU 2. This fuel injection is performed in the order of C # 1, C # 3, C # 4, and C # 2.

  An in-cylinder pressure sensor 11 is integrally attached to the injector 4. The in-cylinder pressure sensor 11 is constituted by a piezoelectric element, detects the pressure in the corresponding cylinder C (hereinafter referred to as “in-cylinder pressure”), and sends an output P representing the in-cylinder pressure to the ECU 2.

  An intake pipe absolute pressure sensor 12 (intake air amount parameter detection means) is provided in the intake pipe 5 of the engine 3. The intake pipe absolute pressure sensor 12 detects an intake pipe absolute pressure PBA (intake air amount parameter) in the intake pipe 5 and sends a detection signal to the ECU 2.

  The exhaust pipe 6 of the engine 3 is provided with a LAF sensor 13 (air-fuel ratio sensor) in the vicinity of the exhaust manifold assembly. The LAF sensor 13 is composed of zirconia and a platinum electrode, and detects the oxygen concentration in the exhaust gas linearly, and converts the detected oxygen concentration into the air-fuel ratio of the air-fuel mixture supplied to the engine 3. A detection signal representing the obtained detected air-fuel ratio AFR (air-fuel ratio) is sent to the ECU 2. In general, as the actual air-fuel ratio increases, the actual oxygen concentration change degree in the exhaust gas obtained by the combustion of the air-fuel ratio mixture tends to decrease, so the air-fuel ratio with respect to the oxygen concentration change amount The ratio of the amount of change is larger as the air-fuel ratio is larger, and is particularly large at a predetermined air-fuel ratio (for example, value 30) or more. For this reason, the detection accuracy of the LAF sensor 13 that detects the air-fuel ratio by the above-described method is high when the air-fuel ratio is smaller than the predetermined air-fuel ratio, and decreases when the air-fuel ratio exceeds the predetermined air-fuel ratio. Tend to.

  A magnet rotor 14 a is attached to the crankshaft 3 a of the engine 3. The magnet rotor 14a and the MRE pickup 14b constitute a crank angle sensor 14. The crank angle sensor 14 sends a CRK signal and a TDC signal, both of which are pulse signals, to the ECU 2 as the crankshaft 3a rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b (only one is shown) of each cylinder C is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the 4-cylinder type. , Output at every 180 ° crank angle. Further, the engine 3 is provided with a cylinder discrimination sensor (not shown). This cylinder discrimination sensor outputs a pulse signal for discriminating the first to fourth cylinders C # 1 to C # 4 as a cylinder discrimination signal. To the ECU 2. The ECU 2 determines the crank angle position for each cylinder C based on the cylinder determination signal, the CRK signal, and the TDC signal.

  The ECU 2 (control means, correction means, correction term setting means and prohibition means) is composed of a microcomputer comprising a CPU, RAM, ROM and the like. The ECU 2 determines the operating state of the engine 3 based on the control program stored in the ROM in accordance with the detection signals of the various sensors 11 to 14 described above, and the fuel injection of the injector 4 based on the determination result. The control process of the engine 3 is executed such as controlling the time TOUT for each cylinder C.

Next, a fuel injection control process for controlling the fuel injection time for each cylinder C will be described with reference to FIGS. FIG. 2 shows a main routine of this fuel injection control process, and this process is executed for each cylinder in synchronization with the input of the TDC signal. First, in step 1 (shown as “S1”, the same applies hereinafter), the indicated mean effective pressure IMEP _i is calculated for each cylinder C. Details of this calculation process will be described later. Note that “i” in the indicated mean effective pressure IMEP _i is a cylinder number i that is discriminated by the above-described cylinder discriminating signal or the like, and this also applies to parameters to be described later.

Next, the fuel injection time TOUT _i for each cylinder is calculated in accordance with the engine speed NE and the indicated mean effective pressure IMEP _i calculated in step 1 (step 2). Next, a drive signal based on the calculated fuel injection time TOUT _i is output to the injector 4 of the corresponding cylinder C (step 3), and this process is terminated. The calculation of the fuel injection time TOUT _{i in} step 2 is performed by searching a map (not shown) according to the engine speed NE and the indicated mean effective pressure IMEP _i . In this map, the fuel injection time TOUT _i is set to be longer as the indicated mean effective pressure IMEP _i is larger. This is because the larger the IMEP _i is, the larger the load of the engine 3 is, so that the output of the engine 3 is increased by increasing the fuel injection amount accordingly.

Next, the calculation process of the indicated mean effective pressure IMEP _i executed in step 1 will be described with reference to the flowchart shown in FIG. First, in step 11, the provisional value IMEP_PS _i of the indicated mean effective pressure is calculated. The provisional value IMEP_PS _i is the indicated mean effective pressure calculated during the previous combustion cycle of the i-th cylinder C # i, and is calculated based on the output P of the in-cylinder pressure sensor 11 of the corresponding cylinder C. Specifically, first, the energy generated per combustion cycle is calculated by integrating the output P of the in-cylinder pressure sensor 11 over one combustion cycle with respect to the stroke volume. Then, the provisional value IMEP_PS _i of the indicated mean effective pressure is calculated by dividing the calculated energy per combustion cycle by the stroke volume.

Next, the final indicated mean effective pressure IMEP _i is calculated by multiplying the calculated provisional value IMEP_PS _i by a correction coefficient K _i (correction term) described later (step 12). This indicated mean effective pressure IMEP _i is used in the calculation of the fuel injection time TOUT _{i in} Step 2 above. The initial value of the correction coefficient K _i is set to the value 1.

Next, the correction coefficient _Ki is set in the processing after step 13. First, it is determined whether or not the detected air-fuel ratio AFR is smaller than a predetermined determination value AFR_PSC (step 13). This determination value AFR_PSC is set to the same value 30 as the predetermined air-fuel ratio described above. Therefore, if the answer to step 13 is YES and the detected air-fuel ratio AFR is smaller than the determination value AFR_PSC, it is assumed that the detection accuracy of the LAF sensor 13 is high. In this case, the correction coefficient K in steps 14 to 22 Perform _i setting processing. On the other hand, when the answer to step 13 is NO and AFR ≧ AFR_PSC, it is determined that the detection accuracy of the LAF sensor 13 is low, and this process is terminated.

  In step 14, the actual intake air amount MAIR is calculated. This actual intake air amount MAIR is an intake air amount that is estimated to have been actually taken into the i-th cylinder C # i in the previous combustion cycle, and is the intake pipe absolute pressure PBA and engine speed NE detected before 4 TDC. Is calculated according to

Next, the detected air-fuel ratio AFR _i for each cylinder is calculated (step 15). The detected air-fuel ratio AFR _i for each cylinder is an estimate of the actual air-fuel ratio of the air-fuel mixture supplied to the i-th cylinder C # i in the previous combustion cycle, and is calculated according to the detected air-fuel ratio AFR. . Although the content of this calculation process is not shown, it is the same as that described in Japanese Patent No. 2717744, and a description thereof will be omitted.

Next, at step 16, the actual intake air amount MAIR calculated at step 14 is divided by the detected air-fuel ratio AFR _i for each cylinder calculated at step 15 to calculate the combustion fuel amount MFUEL _i . This combustion fuel amount MFUEL _i is a fuel amount estimated to be actually burned in the i-th cylinder C # i in the previous combustion cycle, as is apparent from the calculation method.

Next, in step 17, the IMEP_AFR _i table shown in FIG. 4 is searched based on the calculated combustion fuel amount MFUEL _i to obtain the indicated mean effective pressure determination value IMEP_AFR _i . This determination value IMEP_AFR _i corresponds to the indicated mean effective pressure estimated to be obtained when the combustion fuel amount MFUEL _i is combusted. Therefore, in this table, the determination value IMEP_AFR _i is set to a value proportional to the combustion fuel amount MFUEL _i .

Next, in step 18, the judgment value IMEP_AFR _i of the indicated mean effective pressure obtained by subtracting the interim value IMEP_PS _i of the indicated mean effective pressure calculated in step 11, calculates the deviation ERR _i. Next, it is determined whether or not the calculated deviation ERR _i is larger than 0 (step 19).

When this answer is YES and IMEP_PS _i <IMEP_AFR _i , that is, the provisional value IMEP_PS _i obtained based on the output P of the in-cylinder pressure sensor 11 corresponds to the actual intake air amount MAIR and the detected air-fuel ratio AFR _i for each cylinder. when Te is smaller than the determination value IMEP_AFR _i obtained as the output P of the in-cylinder pressure sensor 11 is deviated to a lower side, a predetermined amount of correction coefficient K _i (e.g. 0.01), and increased (step 20), the The process ends.

On the other hand, if the answer to step 19 is NO, it is determined whether or not the deviation ERR _i is smaller than 0 (step 21). If the answer is YES and IMEP_PS _i > IMEP_AFR _i , the output P of the in-cylinder pressure sensor 11 is deviated to the higher side, and the correction coefficient K _i is decreased by a predetermined amount (for example, 0.01) (step 22). This process is terminated.

On the other hand, when the answer to step 21 is NO, that is, when ERR _i = 0 and the provisional value IMEP_PS _i is equal to the determination value IMEP_AFR _i , the correction coefficient K _i is maintained without being increased or decreased, and the present process ends.

As described above, according to the present embodiment, the indicated mean effective pressure IMEP _i for obtaining the fuel injection time TOUT _i is calculated based on the output P of the in-cylinder pressure sensor 11 and the provisional value IMEP_PS of the indicated mean effective pressure. It is calculated by multiplying _i by a correction coefficient K _i . Further, the indicated mean effective pressure determination value IMEP_AFR _i is obtained in accordance with the actual intake air amount MAIR and the detected air-fuel ratio AFR _i for each cylinder. If IMEP_PS _i <IMEP_AFR _i , the output P of the in-cylinder pressure sensor 11 is deviated to the lower side, and the correction coefficient K _i is increased. In the opposite case (IMEP_PS _i > IMEP_AFR _i ) The correction coefficient _Ki is reduced by assuming that the output P of the in-cylinder pressure sensor 11 is shifted to the higher side. Accordingly, the indicated mean effective pressure IMEP _i can be appropriately calculated while appropriately compensating for the deviation of the output P of the in-cylinder pressure sensor 11 from the appropriate value, and the fuel injection control based on the indicated mean effective pressure IMEP _i is appropriately performed. Can be done.

Further, the detected air-fuel ratio AFR is prohibits updating of the correction coefficient K _i when greater than the determination value AFR_PSC, the detected air-fuel ratio AFR is smaller than the determination value AFR_PSC, only the detection accuracy is high the LAF sensor 13, The correction coefficient K _i is updated using the indicated mean effective pressure determination value IMEP_AFR _i . Therefore, it is possible to appropriately correct the provisional value IMEP_PS _i of the indicated mean effective pressure by the correction coefficient K _i .

In the embodiment, when the deviation ERR _i is larger or smaller than the value 0, the correction coefficient K _i is increased or decreased by a certain amount. However, the present invention is not limited to this, and the increase and decrease amounts of the correction coefficient K _i are not limited. Each may be set to a larger value as the absolute value of the deviation ERR _i is larger. Further, the embodiment is an example in which the indicated mean effective pressure determination value IMEP_AFR _i is obtained according to the combustion fuel amount MFUEL _i , but instead of this, the actual intake air amount is not passed through the combustion fuel amount MFUEL _i. it may be determined directly from the detected air-fuel ratio AFR _i per MAIR and cylinders. For example, the relationship between the actual intake air amount MAIR, the detected air-fuel ratio AFR _i for each cylinder, and the indicated mean effective pressure is obtained in advance by experiments, a map representing this relationship is created, and the indicated mean obtained by searching this map The effective pressure may be set as the indicated mean effective pressure determination value IMEP_AFR _i .

  Further, the embodiment is an example in which the actual intake air amount MAIR is calculated according to the intake pipe absolute pressure PBA and the engine speed NE, but instead, an air flow sensor is provided in the intake pipe, thereby directly It may be detected. When a throttle valve is provided in the intake pipe, an air flow sensor and an intake pipe absolute pressure sensor are provided on the upstream side and the downstream side of the throttle valve of the intake pipe, respectively, and the actual intake air amount is determined according to these detection results. MAIR may be obtained.

  Further, the embodiment is an example in which the air-fuel ratio of each cylinder C is calculated according to the detected air-fuel ratio AFR detected by a single LAF sensor 13 provided in the collection portion of the exhaust manifold. Alternatively, it may be detected directly by a LAF sensor provided at each branch portion of the exhaust manifold. Furthermore, in the embodiment, the LAF sensor 13 is used as the air-fuel ratio sensor. Instead, a sensor of a type that is provided in the combustion chamber and directly detects the air-fuel ratio supplied to the cylinder is used. May be.

In the embodiment, the provisional value IMEP_PS _i of the indicated mean effective pressure calculated based on the output P of the in-cylinder pressure sensor 11 is corrected by the correction coefficient K _i , but instead, the output P of the in-cylinder pressure sensor 11 is corrected. May be corrected directly. Furthermore, in the embodiment, the fuel injection amount is controlled according to the output P of the in-cylinder pressure sensor 11, but the control target may be other engine control parameters, for example, ignition timing. Further, the control device 1 of the present invention can be applied to various industrial engines including a marine vessel propulsion engine such as an outboard motor having a crankshaft arranged in a vertical direction. In addition, it is possible to appropriately change the detailed configuration within the scope of the present invention.

Explanation of symbols

1 control device 2 ECU (control means, correction means, correction term setting means, prohibition means)
3 Engine C Cylinder 11 In-cylinder pressure sensor 12 Intake pipe absolute pressure sensor (intake air amount parameter detection means)
13 LAF sensor (air-fuel ratio sensor)
P In-cylinder pressure sensor output PBA Intake pipe absolute pressure (intake air volume parameter)
AFR detection air-fuel ratio (air-fuel ratio)
_Ki correction factor (correction term)

Claims (2)

An in-cylinder pressure sensor that detects an in-cylinder pressure that is a pressure in the cylinder;
Control means for controlling the internal combustion engine in accordance with the output of the in-cylinder pressure sensor;
An intake air amount parameter detecting means for detecting an intake air amount parameter representing an intake air amount sucked into the cylinder;
An air-fuel ratio sensor for detecting an air-fuel ratio of an air-fuel mixture supplied to the cylinder;
Correction means for correcting the output of the in-cylinder pressure sensor in accordance with the detected intake air amount parameter and the air-fuel ratio;
A control device for an internal combustion engine, comprising: The correction means includes
Correction term setting means for setting a correction term for correcting the output of the in-cylinder pressure sensor in accordance with the intake air amount parameter and the air-fuel ratio;
2. The control device for an internal combustion engine according to claim 1, further comprising prohibiting means for prohibiting the update of the correction term when the air-fuel ratio is not within a predetermined range.

Images