JP2020084912A - Controller for internal combustion engine - Google Patents

Abstract

To detect failure of a combustion pressure sensor even in a case where a combustion pressure sensor is not installed in each of a plurality of cylinder in an internal combustion engine or a case where a plurality of combustion pressure sensors is broken simultaneously.SOLUTION: A crank angle sensor that detects a rotation angle of a crankshaft that is rotationally driven by an internal combustion engine, and a combustion pressure sensor that detects combustion pressure P in at least one of a plurality of cylinders are attached to the internal combustion engine. A controller for an internal combustion engine calculates indicated mean effective pressure IMEP based on the combustion pressure P detected by the combustion pressure sensor, and calculates an amplitude C of a primary component of a crank angular velocity N based on the rotation angle detected by the crank angle sensor. Then, the controller calculates an approximate expression based on the history of the indicated mean effective pressure IMEP and the amplitude C, and detects failure of the combustion pressure sensor based on the approximate expression.SELECTED DRAWING: Figure 8

Description

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

In recent years, in order to improve the fuel efficiency of vehicles, internal combustion engines that incorporate the technology of operating an internal combustion engine with an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio and the technology of taking in part of the exhaust gas after combustion and letting it into the internal combustion engine again Control devices have been developed.

In an internal combustion engine that is controlled using this type of control device, the amount of fuel and air in the combustion chamber deviates from the theoretical value, and combustion in the combustion chamber becomes unstable. As a result, in the vehicle, vibrations due to increased fluctuations in the combustion torque of the internal combustion engine (engine torque) increase, and the ride comfort of the driver deteriorates. Therefore, it is important to accurately detect the combustion state and control the internal combustion engine according to the detection result.

A combustion pressure sensor is a means for accurately detecting the combustion state of an internal combustion engine. By installing the combustion pressure sensor in the combustion chamber, it is possible to accurately detect the combustion state. However, since the combustion pressure sensor installed in the combustion chamber is in contact with high pressure and high temperature due to combustion, the probability of failure increases. If the internal combustion engine is controlled based on the combustion pressure that is erroneously detected when the combustion pressure sensor has failed, combustion in the combustion chamber may become more unstable.

Patent Document 1 is known for detecting a failure of a combustion pressure sensor. Patent Document 1 discloses a technique of comparing detected values of combustion pressure sensors (in-cylinder pressure sensors) attached to each cylinder of a multi-cylinder engine and detecting a failure of the in-cylinder pressure sensor from the difference.

JP, 2016-98754, A

The technique disclosed in Patent Document 1 is based on the premise that the combustion pressure sensor is attached to at least two or more cylinders. Therefore, when the combustion pressure sensor is mounted on only one cylinder, the failure of the combustion pressure sensor cannot be detected. Further, even when a plurality of combustion pressure sensors are simultaneously broken down due to deterioration over time or engine overheating, the failure of the combustion pressure sensors cannot be detected.

Therefore, the present invention has been made in view of the above problems, in the case where the combustion pressure sensor is not installed in each of the plurality of cylinders of the internal combustion engine, or when the plurality of combustion pressure sensors simultaneously fail. Also aims to detect a failure of the combustion pressure sensor.

An internal combustion engine control device according to the present invention is a control device for an internal combustion engine having a plurality of cylinders, wherein the internal combustion engine includes a crank angle sensor that detects a rotation angle of a crankshaft that is rotationally driven by the internal combustion engine. , A combustion pressure sensor that detects a combustion pressure in at least one of the plurality of cylinders, and the control device calculates an indicated mean effective pressure based on the combustion pressure detected by the combustion pressure sensor. Then, the amplitude of the first-order component of the crank angular velocity based on the rotation angle detected by the crank angle sensor is calculated, an approximate expression is calculated from the indicated mean effective pressure and the history of the amplitude, and the combustion based on the approximate expression is performed. Detect pressure sensor failure.

According to the present invention, it is possible to detect the failure of the combustion pressure sensor even when the combustion pressure sensor is not installed in each of the plurality of cylinders of the internal combustion engine, or even when the plurality of combustion pressure sensors simultaneously fail. it can.

FIG. 1 is a diagram illustrating a main part configuration of an internal combustion engine and a control device for an internal combustion engine according to an embodiment. It is a functional block diagram explaining the functional composition of the control device concerning an embodiment. It is a schematic diagram explaining the principal part structure of the internal combustion engine to which the control device is applied. It is a top view explaining the arrangement of a cylinder. It is a figure which shows an example of the combustion pressure in each of the misfire state and the combustion state, the indicated mean effective pressure, the crank angular velocity, and the amplitude of the primary component of the crank angular velocity. It is a figure which shows an example of the amplitude of the crank angular velocity for every frequency component in a combustion state and a misfire state. It is a figure which shows an example of the correlation of the amplitude of the primary component of crank angular velocity at the time of predetermined mode driving|running, and the indicated mean effective pressure. 5 is a flowchart showing a procedure of failure detection processing of the combustion pressure sensor according to the embodiment.

Hereinafter, the control device 1 which is one mode of the control device for an internal combustion engine according to the embodiment of the present invention will be described. In this embodiment, the case where the control device 1 controls the four-cylinder internal combustion engine 100 will be described as an example.
Hereinafter, in the embodiment, a combination of a part or all of the internal combustion engine 100 and a part or all of the control device 1 is referred to as a control device 1 of the internal combustion engine 100.

[Internal combustion engine]
FIG. 1 is a diagram illustrating a main part configuration of an internal combustion engine 100 and a control device 1 that controls the internal combustion engine 100.

In the internal combustion engine 100, the air sucked from the outside flows through the air cleaner 110, the intake pipe 111, and the intake manifold 112, and then flows into each cylinder 150. The amount of air flowing into each cylinder 150 is adjusted by the throttle valve 113, and the amount of air adjusted by the throttle valve 113 is measured by the flow rate sensor 114. The pressure of the air flowing into each cylinder 150 is measured by the intake pressure sensor 116 (see FIG. 3) provided in the intake manifold 112.

The throttle valve 113 is provided with a throttle opening sensor 113a that detects the opening of the throttle. The opening information of the throttle valve 113 detected by the throttle opening sensor 113a is output to a control device (Electronic Control Unit: ECU) 1.

An electronic throttle valve driven by an electric motor is used as the throttle valve 113, but any other system may be used as long as the flow rate of air can be appropriately adjusted.

The temperature of the gas flowing into each cylinder 150 is detected by the intake air temperature sensor 115.

A crank angle sensor 121 is provided outside the ring gear 120 attached to the crankshaft 123 in the radial direction. The crank angle sensor 121 detects the rotation angle of the crankshaft 123. In the embodiment, the crank angle sensor 121 detects, for example, the rotation angle of the crankshaft 123 every 10° and each combustion cycle.

A water temperature sensor 122 is provided on a water jacket (not shown) of the internal combustion engine 100. The water temperature sensor 122 detects the temperature of the cooling water of the internal combustion engine 100.

Further, the vehicle is provided with an accelerator position sensor (APS) 126 that detects a displacement amount (depression amount) of the accelerator pedal 125. The accelerator position sensor 126 detects the torque required by the driver. The driver's required torque detected by the accelerator position sensor 126 is output to the control device 1 described later. The control device 1 controls the throttle valve 113 based on this required torque.

The fuel stored in the fuel tank 130 is sucked by the feed pump 131, then flows through the fuel pipe 133, and is guided to the pressurizing pump 132. The pressurizing pump 132 pressurizes the fuel supplied from the feed pump 131 to adjust it to a predetermined fuel pressure, and sends it to a fuel injection valve (injector) 134 installed in each cylinder 150 via a fuel pipe 133. .. As a result of the pressure adjustment by the pressurizing pump 132, excess fuel is returned to the fuel tank 130 via a return pipe (not shown).

The fuel injection valve 134 injects the fuel pressurized by the pressure pump 132 into each cylinder 150. Although the fuel injection valve 134 is attached to the intake manifold 112 in FIG. 1, it is actually attached to the cylinder head 180 of the internal combustion engine 100 so that fuel can be injected into the cylinder 150.

Inside each cylinder 150 of the internal combustion engine 100, a combustion pressure sensor (Cylinder Pressure Sensor: CPS, also called an in-cylinder pressure sensor) 140 is provided. The combustion pressure sensor 140 detects the pressure (combustion pressure) in the cylinder 150.

The combustion pressure sensor 140 is a vibration detection type sensor that detects the combustion pressure by measuring the mechanical vibration of the internal combustion engine 100. In the embodiment, the combustion pressure sensor 140 is a non-resonance type vibration detection sensor, and can detect the vibration of the internal combustion engine 100 over a wide frequency band.

An exhaust manifold 160 that discharges the gas (exhaust gas) after combustion to the outside of the cylinder 150 is attached to each cylinder 150. A three-way catalyst 161 is provided on the exhaust side of the exhaust manifold 160, and exhaust gas is discharged from the cylinder 150 to the exhaust manifold 160. The exhaust gas passes through the exhaust manifold 160, is purified by the three-way catalyst 161, and is then discharged to the atmosphere.

An upstream air-fuel ratio sensor 162 and an exhaust temperature sensor 164 are provided on the upstream side of the three-way catalyst 161. The upstream air-fuel ratio sensor 162 continuously detects the air-fuel ratio of the exhaust gas discharged from each cylinder 150. The exhaust temperature sensor 164 measures the temperature of the exhaust gas discharged from the cylinder 150.

A downstream air-fuel ratio sensor 163 is provided downstream of the three-way catalyst 161. The downstream air-fuel ratio sensor 163 outputs a switch-like detection signal in the vicinity of the theoretical air-fuel ratio. In the embodiment, the downstream air-fuel ratio sensor 163 is, for example, an O2 sensor.

In addition, an ignition plug 200 is provided above each cylinder 150. Due to the discharge (ignition) of the spark plug 200, a spark is ignited in the mixture of air and fuel in the cylinder 150, an explosion occurs in the cylinder 150, and the piston 170 is pushed down. When the piston 170 is pushed down, the crankshaft 123 rotates.

An ignition coil 300 that generates electric energy (voltage) supplied to the spark plug 200 is connected to the spark plug 200. The voltage generated in the ignition coil 300 causes discharge between the center electrode and the outer electrode of the spark plug 200.

Output signals from various sensors such as the throttle opening sensor 113a, the flow rate sensor 114, the crank angle sensor 121, the accelerator position sensor 126, the water temperature sensor 122, and the combustion pressure sensor 140 described above are output to the control device 1. In the control device 1, the operating state of the internal combustion engine 100 is detected based on the output signals from these various sensors, and the air amount (target air amount) to be sent into the cylinder 150, the fuel injection amount, the ignition timing of the spark plug 200. Etc. are controlled.

The target air amount calculated by the control device 1 is converted from a throttle opening (target throttle opening) into an electronic throttle drive signal and output to an electric motor (not shown) that drives the throttle valve 113. Further, the ignition timing calculated by the control device 1 is output to the ignition coil 300 as an ignition signal converted into the energization start angle and the energization angle, and the spark plug 200 is discharged (ignited) based on the ignition signal. ..

[Hardware configuration of control device]
Next, the overall hardware configuration of the control device 1 will be described.

As shown in FIG. 1, the control device 1 includes an analog input unit 10, a digital input unit 20, an A/D (Analog/Digital) conversion unit 30, a RAM (Random Access Memory) 40, and an MPU (Micro-). A processing unit 50, a ROM (Read Only Memory) 60, an I/O (Input/Output) port 70, and an output circuit 80.

The analog input unit 10 includes various sensors such as a throttle opening sensor 113a, a flow rate sensor 114, an accelerator position sensor 126, an upstream side air-fuel ratio sensor 162, a downstream side air-fuel ratio sensor 163, a combustion pressure sensor 140, and a water temperature sensor 122. An analog output signal is input.

An A/D conversion unit 30 is connected to the analog input unit 10. The analog output signals from the various sensors input to the analog input unit 10 are subjected to signal processing such as noise removal, converted into digital signals by the A/D conversion unit 30, and stored in the RAM 40.

A digital output signal from the crank angle sensor 121 is input to the digital input unit 20.

An I/O port 70 is connected to the digital input section 20, and the digital output signal input to the digital input section 20 is stored in the RAM 40 via the I/O port 70.

The output signals stored in the RAM 40 are processed by the MPU 50.

The MPU 50 executes a control program (not shown) stored in the ROM 60 to arithmetically process the output signal stored in the RAM 40 according to the control program. The MPU 50 calculates a control value that defines the operation amount of each actuator (for example, the throttle valve 113, the spark plug 200, etc.) that drives the internal combustion engine 100 according to the control program, and temporarily stores it in the RAM 40.

The control value that defines the operation amount of the actuator stored in the RAM 40 is output to the output circuit 80 via the I/O port 70.

The output circuit 80 is provided with the functions of a fuel injection control unit 82 (see FIG. 2) that controls the fuel injection valve 134 and an ignition control unit 83 (see FIG. 2) that controls the voltage applied to the spark plug 200. ing.

[Function block of control device]
Next, a functional configuration of the control device 1 according to the embodiment will be described.

FIG. 2 is a functional block diagram illustrating a functional configuration of the control device 1 according to the embodiment. Each function of the control device 1 is realized by the output circuit 80, for example, when the MPU 50 executes the control program stored in the ROM 60.

As shown in FIG. 2, the output circuit 80 of the control device 1 according to the embodiment includes an overall control unit 81, a fuel injection control unit 82, and an ignition control unit 83.

The overall control unit 81 is connected to the accelerator position sensor 126, the combustion pressure sensor 140 (CPS), and the angle information generation unit 85 that measures the crank angle of the crankshaft 123, and requests from the accelerator position sensor 126. The torque (acceleration signal S1), the output signal S2 from the combustion pressure sensor 140, and the crank angle information S4 from the angle information generation unit 85 are received.

The overall control unit 81 controls the fuel injection control unit 82 and the ignition control unit 83 as a whole based on the required torque (acceleration signal S1) from the accelerator position sensor 126 and the output signal S2 from the combustion pressure sensor 140. I do. Further, the failure of the combustion pressure sensor 140 is detected based on the output signal S2 from the combustion pressure sensor 140 and the crank angle information S4 from the angle information generator 85.

In the embodiment, at least the combustion pressure (vibration: output signal S2) information from the combustion pressure sensor 140 is input to the overall control unit 81, and the overall control unit 81 detects the combustion pressure based on this information. And the occurrence of knocking are detected. When the combustion pressure sensor 140 fails, this is detected as an abnormality of the combustion pressure sensor 140.

The fuel injection control unit 82 includes a cylinder determination unit 84 that determines each cylinder 150 of the internal combustion engine 100, an angle information generation unit 85 that measures the crank angle of the crankshaft 123, and a rotation speed information generation unit that measures the engine speed. 86, and the cylinder discrimination information S3 from the cylinder discrimination unit 84, the crank angle information S4 from the angle information generation unit 85, and the engine rotation speed information S5 from the rotation speed information generation unit 86. Accept.

The fuel injection control unit 82 also measures an intake amount measurement unit 87 that measures the intake amount of the air taken into the cylinder 150, a load information generation unit 88 that measures the engine load, and the temperature of the engine cooling water. The intake air amount information S6 from the intake air amount measuring unit 87, the engine load information S7 from the load information generating unit 88, and the cooling water temperature information S8 from the water temperature measuring unit 89 are connected to the water temperature measuring unit 89. , Is accepted.

The fuel injection control unit 82 calculates the injection amount and the injection time of the fuel injected from the fuel injection valve 134 based on the received information, and the fuel injection is performed based on the calculated fuel injection amount and the injection time. The valve opening control signal S9 for controlling the valve 134 is output.

The ignition control unit 83 is connected to the cylinder control unit 84, the angle information generation unit 85, the rotation speed information generation unit 86, the load information generation unit 88, and the water temperature measurement unit 89 in addition to the overall control unit 81. And accepts each information from these.

Based on the received information, the ignition control unit 83 supplies the amount of current (energization angle) for energizing the primary coil (not shown) of the ignition coil 300, the energization start time, and energizing the primary coil. Calculate the time to cut off the current (ignition time).

The ignition control unit 83 outputs an ignition signal SA to the primary coil of the ignition coil 300 based on the calculated energization angle, energization start time, and ignition time, so that the spark plug 200 controls discharge (ignition). Control).

Furthermore, combustion pressure (cylinder pressure) information and knocking information from the overall control unit 81 are input to the ignition control unit 83.

The ignition control unit 83 calculates an ignition timing correction value based on the MBT control based on the combustion pressure information, and calculates a retard angle correction value based on the knocking information. The ignition control unit 83 executes an MBT (Minimum advance for the Best Torque) control or a retard control when knocking occurs, based on these calculation results.

[Structure of main parts of internal combustion engine]
Next, a main part configuration of the internal combustion engine 100 to which the control device 1 according to the embodiment is applied will be described. The internal combustion engine 100 is, for example, a cylinder injection type gasoline engine for a vehicle.

FIG. 3 is a schematic diagram illustrating the configuration of a main part of an internal combustion engine 100 to which the control device 1 is applied. FIG. 4 is a plan view illustrating the arrangement of the cylinders 150.

As shown in FIG. 3, the internal combustion engine 100 of the embodiment will be described by exemplifying a case of an in-line four-cylinder gasoline engine for a vehicle that performs spark ignition combustion.

As shown in FIGS. 3 and 4, in this internal combustion engine 100, a first cylinder 151, a second cylinder 152, a third cylinder 153, and a fourth cylinder 154 are provided in series in a cylinder block (not shown). There is. Hereinafter, unless otherwise distinguished, the first cylinder 151 to the fourth cylinder 154 are simply referred to as the cylinder 150.

As shown in FIGS. 3 and 4, a spark plug 200 and a combustion pressure sensor 140 are mounted in the combustion chamber 150a of each cylinder 150. In the combustion chamber 150a of each cylinder 150, the crankshaft 123 rotates at a rotation angle of 180 degrees, and ignition and combustion are performed by the spark plug 200. When the internal combustion engine 100 has four in-line cylinders, combustion in each cylinder 150 is performed in the order of the first cylinder 151, the third cylinder 153, the fourth cylinder 154, and the second cylinder 152.

As shown in FIG. 3, a cylinder head 180 is provided above each cylinder 150. In the cylinder head 180, an intake camshaft 5a that operates an intake valve 6a that adjusts the intake of an air-fuel mixture (air-fuel mixture) into the cylinder 150, and the exhaust gas exhaust from the cylinder 150 are adjusted. The exhaust camshaft 5b for operating the exhaust valve 6b is provided.

As shown in FIG. 3, the high-pressure fuel pressurized by the pressurizing pump 132 is supplied to the fuel injection valve 134 attached to each cylinder 150 through the fuel pipe 133, and the fuel injection valve 134 causes each cylinder to operate. It is injected into 150.

[Failure detection method for combustion pressure sensor]
Next, a method of detecting a failure of the combustion pressure sensor 140 according to the embodiment will be described.

FIG. 5 is a diagram showing an example of the combustion pressure, the indicated mean effective pressure, the crank angular velocity, and the amplitude of the primary component of the crank angular velocity in each of the misfire state and the combustion state.

FIG. 5A is an example of a waveform of the combustion pressure P detected by the combustion pressure sensor 140 in the misfire state. In the misfire state, ignition of the air-fuel mixture due to ignition does not occur, so that the combustion pressure P does not rise in the cylinder 150 due to the explosion of the air-fuel mixture. Therefore, as shown in FIG. 5A, the combustion pressure P rises only in the adiabatic compression portion.

FIG. 5B is an example of a waveform of the combustion pressure P detected by the combustion pressure sensor 140 in the combustion state. In the combustion state, ignition of the air-fuel mixture due to ignition causes the combustion pressure P to rise in the cylinder 150 due to the explosion of the air-fuel mixture. Therefore, as shown in FIG. 5(b), the combustion pressure P greatly increases after ignition.

FIG. 5C is an example of the indicated mean effective pressure IMEP in the misfire state. In the misfire state, ignition of the air-fuel mixture due to ignition does not occur, so the indicated mean effective pressure IMEP becomes zero as shown in FIG. 5(c).

FIG. 5D is an example of the indicated mean effective pressure IMEP in the combustion state. In the combustion state, ignition of the air-fuel mixture due to ignition causes the combustion pressure P to rise in the cylinder 150 due to the explosion of the air-fuel mixture. Therefore, as shown in FIG. 5D, the indicated mean effective pressure IMEP becomes a positive value.

From FIGS. 5A to 5D, it can be seen that the presence or absence of combustion is reflected in the indicated mean effective pressure IMEP.

FIG. 5E is an example of a waveform of the crank angular velocity N obtained from the rotation angle of the crankshaft 123 detected by the crank angle sensor 121 in the misfire state. Although the amplitude of the crank angular velocity N increases as the combustion pressure P increases, as shown in FIG. 5A, the combustion pressure P increases only in the adiabatic compression state in the misfire state. Therefore, as shown in FIG. 5E, the amplitude of the crank angular velocity N does not become so large even near the top dead center. Further, the waveform of the crank angular velocity N shown in FIG. 5(e) is symmetrical with the apex coincident with the top dead center.

FIG. 5F is an example of a waveform of the crank angular velocity N obtained from the rotation angle of the crankshaft 123 detected by the crank angle sensor 121 in the combustion state. The amplitude of the crank angular velocity N increases as the combustion pressure P increases, but as shown in FIG. 5B, the combustion pressure P increases significantly after ignition in the combustion state. Therefore, as shown in FIG. 5(f), the amplitude of the crank angular velocity N becomes large near the top dead center. Further, in the waveform of the crank angular velocity N shown in FIG. 5(f), the apex deviates from the top dead center, and the waveform is bilaterally asymmetric.

FIG. 5G is an example of the amplitude C of the first-order component of the crank angular velocity N in the misfire state. In the misfire state, the waveform of the crank angular velocity N is symmetrical as shown in FIG. Therefore, the frequency component of the waveform of the crank angular velocity N has many primary components, and as shown in FIG. 5G, the amplitude C of the primary component of the crank angular velocity N increases.

FIG. 5H is an example of the amplitude C of the first-order component of the crank angular velocity N in the combustion state. In the combustion state, as shown in FIG. 5(f), the waveform of the crank angular velocity N becomes bilaterally asymmetric and the phase also changes. Therefore, the first-order component of the frequency component of the waveform of the crank angular velocity N decreases, and the amplitude C of the first-order component of the crank angular velocity N decreases, as shown in FIG.

It is understood from FIGS. 5E to 5H that the presence or absence of combustion is reflected on the amplitude C of the primary component of the crank angular velocity N.

Therefore, it is understood from FIGS. 5A to 5H that there is a correlation between the indicated mean effective pressure IMEP and the amplitude C of the primary component of the crank angular velocity N.

FIG. 6 is a diagram showing an example of the amplitude C of the crank angular velocity N for each frequency component in the combustion state and the misfire state. In FIG. 6, when the frequency order is the first-order component, the difference in the amplitude C of the crank angular velocity N between the misfire state and the combustion state is large. Therefore, regarding the frequency order, it can be seen that the highest correlation is obtained for the first-order component.

FIG. 7 is a diagram showing an example of the correlation between the amplitude C of the primary component of the crank angular velocity N and the indicated average effective pressure IMEP during traveling in a predetermined mode. As shown in FIG. 7, even when the combustion state of the internal combustion engine 100 changes variously due to the mode running, the indicated average effective pressure IMEP and the amplitude C of the primary component of the crank angular velocity N are substantially linearly correlated. It turns out that there is.

From this, when there is a change in the correlation between the amplitude C of the primary component of the crank angular velocity N and the indicated mean effective pressure IMEP, at least either the combustion pressure sensor 140 or the crank angle sensor 121 may be abnormal. It can be judged that there is. Here, with respect to the crank angle sensor 121, failure diagnosis can be performed using information from other devices such as a cam angle sensor (not shown) that detects the angle of the intake camshaft 5a or the exhaust camshaft 5b. .. Therefore, when there is a change in the correlation between the amplitude C of the primary component of the crank angular velocity N and the indicated mean effective pressure IMEP while the crank angle sensor 121 is normal, it is determined that the combustion pressure sensor 140 is normal. it can.

FIG. 8 is a flowchart showing a procedure of failure detection processing of the combustion pressure sensor 140 according to the embodiment. The flowchart of FIG. 8 is executed by the control device 1 at a predetermined timing when the internal combustion engine 100 is powered on.

<<Step S101>>
In step S101, the control device 1 starts the failure detection process of the combustion pressure sensor 140, and starts the processes of step S111 and step S121 in parallel.

<<Step S111>>
In step S111, the combustion pressure sensor 140 detects the combustion pressure P, and the overall control unit 81 acquires the combustion pressure P detected by the combustion pressure sensor 140 based on the output signal S2 from the combustion pressure sensor 140.

<<Step S112>>
In step S112, the overall control unit 81 calculates the indicated mean effective pressure IMEP based on the combustion pressure P acquired in step S111. After calculating the indicated mean effective pressure IMEP, the process proceeds to step S131.

≪Step S121≫
In step S121, the crank angle sensor 121 detects the rotation angle of the crankshaft 123 in a predetermined cycle to detect the crank angular velocity N, and the overall control unit 81 acquires the detected crank angular velocity N.

<<Step S122>>
In step S122, the overall control unit 81 determines whether the crank angular velocity N acquired in step S121 is used for a predetermined period (for example, a rotation angle of the crankshaft 123 of 180° around the top dead center). The change in the angular velocity N is extracted.

<<Step S123>>
In step S123, the overall controller 81 calculates the amplitude C of the primary component of the crank angular velocity N based on the change in the crank angular velocity N extracted in step S122. After calculating the amplitude C, the process proceeds to step S131.

<<Step S131>>
In step S131, the overall control unit 81 correlates the indicated average effective pressure IMEP and the amplitude C from the history (for example, 300 cycles) of the indicated average effective pressure IMEP calculated in step S112 and the amplitude C calculated in step S123. An approximate expression expressing is calculated. Here, for example, a linear approximation expression representing a linear expression as shown in FIG. 7 is calculated as an approximation expression representing the correlation between the indicated mean effective pressure IMEP and the amplitude C.

<<Step S132>>
In step S132, the overall control unit 81 calculates the slope A and the intercept B of the linear approximation formula calculated in step S131.

<<Step S141>>
In step S141, the overall control unit 81 compares the slope A and the intercept B calculated in step S132 with predetermined normal ranges for the respective values, thereby determining the correlation between the indicated mean effective pressure IMEP and the amplitude C. It is determined whether or not the slope A and the intercept B of the linear approximation formula shown are within predetermined normal ranges. As a result, if both the slope A and the intercept B are within the normal range, the process proceeds to step S142, and if at least one of them is not within the normal range, the process proceeds to step S143.

<<Step S142>>
In step S142, the overall control unit 81 makes a normal determination with respect to the combustion pressure sensor 140, and determines that the combustion pressure sensor 140 has not failed.

<<Step S143>>
In step S143, the overall control unit 81 makes an abnormality determination on the combustion pressure sensor 140, and determines that the combustion pressure sensor 140 is out of order.

<<Step S151>>
When the normality determination is performed in step S142 or the abnormality determination is performed in step S143, the process proceeds to step S151, and the failure detection process of the combustion pressure sensor 140 ends.

According to the embodiment of the present invention described above, the following operational effects are exhibited.

(1) The control device 1 for the internal combustion engine is a control device for the internal combustion engine 100 having a plurality of cylinders 150. The internal combustion engine 100 includes a crank angle sensor 121 that detects a rotation angle of a crankshaft 123 that is rotationally driven by the internal combustion engine 100, and a combustion pressure sensor 140 that detects a combustion pressure P in at least one of a plurality of cylinders 150. Is attached. The control device 1 calculates the indicated mean effective pressure IMEP based on the combustion pressure P detected by the combustion pressure sensor 140 (step S112), and the amplitude of the primary component of the crank angular velocity N based on the rotation angle detected by the crank angle sensor 121. C is calculated (step S123). Then, an approximate expression is calculated from the history of the indicated mean effective pressure IMEP and the amplitude C (step S131), and a failure of the combustion pressure sensor 140 is detected based on this approximate expression (steps S141, S143). Thus, even if the combustion pressure sensor 140 is not installed in each of the plurality of cylinders 150 of the internal combustion engine 100, or even if the plurality of combustion pressure sensors 140 simultaneously fail, the failure of the combustion pressure sensor 140 occurs. Can be detected.

(2) The approximate expression calculated in step S131 is a linear approximate expression. When the slope A and the intercept B of the linear approximation formula are within predetermined normal ranges (step S141: Yes), the controller 1 determines that the combustion pressure sensor 140 is normal (step S142), and the slope When at least one of A and intercept B is outside the normal range (step S141: No), it is determined that the combustion pressure sensor 140 has failed (step S143). Since this is done, the failure of the combustion pressure sensor 140 can be reliably detected from the correlation between the indicated mean effective pressure IMEP and the amplitude C.

(3) The combustion pressure sensor 140 is attached to each of the plurality of cylinders 150 (first cylinder 151 to fourth cylinder 154). Since this is done, the combustion pressure of each cylinder 150 can be reliably detected, and when the combustion pressure sensor 140 fails, it can be reliably detected.

In the above embodiment, as shown in FIG. 4, an example in which the combustion pressure sensor 140 is attached to each cylinder 150 has been described, but the combustion pressure sensor 140 does not have to be attached to all the cylinders 150. Absent. The present invention is applicable to the internal combustion engine 100 in which the combustion pressure sensor 140 is attached to at least one cylinder 150. Even when the combustion pressure sensor 140 is attached only to one cylinder 150, it is possible to detect the failure of the combustion pressure sensor 140 by the procedure described in FIG.

Further, in step S112 of FIG. 8, instead of calculating the indicated mean effective pressure IMEP from the combustion pressure P, for example, the pressure integrated value, the maximum pressure, the maximum pressure timing, etc. may be calculated. Even if these are used instead of the indicated mean effective pressure IMEP, it is possible to detect the failure of the combustion pressure sensor 140 by the same procedure as described in the above embodiment.

Further, in step S131 of FIG. 8, the approximation formula calculated from the history of the indicated mean effective pressure IMEP and the amplitude C may not be a linear approximation formula. For example, even if polynomial approximation, exponential approximation, logarithmic approximation, cumulative approximation, moving average, or the like is used instead, it is possible to determine whether the combustion pressure sensor 140 is normal or abnormal by comparing these calculation results with a predetermined normal range. It is possible to determine if there is.

In the embodiment described above, each functional configuration of the control device 1 described with reference to FIG. 2 may be realized by software executed by the MPU 50 as described above, or an FPGA (Field-Programmable Gate Array) or the like. It may be realized by hardware. Also, these may be used in combination.

Although one example of the embodiment of the present invention has been described above, the present invention may be a combination of all the above-described embodiments, or any two or more embodiments may be arbitrarily combined.
Further, the present invention is not limited to the one including all the configurations of the above-described embodiment, and a part of the configuration of the above-described embodiment may be replaced with the configuration of another embodiment. The configuration of the above-described embodiment may be replaced with the configuration of another embodiment.
Moreover, you may add, delete, and replace a part of structure of embodiment mentioned above with the structure of other embodiment.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents unless the characteristics of the invention are impaired. Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other modes considered within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1: control device, 5a: intake camshaft, 5b: exhaust camshaft, 6a: intake valve, 6b: exhaust valve, 10: analog input unit, 20: digital input unit, 30: A/D conversion unit, 40: RAM , 50: MPU, 60: ROM, 70: I/O port, 80, 80a: output circuit, 81: overall control unit, 82: fuel injection control unit, 83: ignition control unit, 84: cylinder determination unit, 85: Angle information generation unit, 86: rotation speed information generation unit, 87: intake air amount measurement unit, 88: load information generation unit, 89: water temperature measurement unit, 100: internal combustion engine, 110: air cleaner, 111: intake pipe, 112: intake air Manifold, 113: Throttle valve, 113a: Throttle opening sensor, 114: Flow rate sensor, 115: Intake temperature sensor, 116: Intake pressure sensor, 120: Ring gear, 121: Crank angle sensor, 122: Water temperature sensor, 123: Crank Shaft, 125: accelerator pedal, 126: accelerator position sensor, 130: fuel tank, 131: feed pump, 132: pressurizing pump, 133: fuel pipe, 134: fuel injection valve, 140: combustion pressure sensor, 150: cylinder, 160: exhaust manifold, 161: three-way catalyst, 162: upstream air-fuel ratio sensor, 163: downstream air-fuel ratio sensor, 164: exhaust temperature sensor, 170: piston, 180: cylinder head, 200: spark plug, 300: ignition coil

Claims (4)

A control device for an internal combustion engine having a plurality of cylinders,
A crank angle sensor that detects a rotation angle of a crankshaft that is rotationally driven by the internal combustion engine, and a combustion pressure sensor that detects a combustion pressure in at least one of the plurality of cylinders are attached to the internal combustion engine. Cage,
The control device is
Calculate the indicated mean effective pressure based on the combustion pressure detected by the combustion pressure sensor,
Calculating the amplitude of the primary component of the crank angular velocity based on the rotation angle detected by the crank angle sensor,
An approximate expression is calculated from the indicated average effective pressure and the history of the amplitude,
A control device for an internal combustion engine, which detects a failure of the combustion pressure sensor based on the approximate expression. The internal combustion engine controller according to claim 1,
The approximation formula is a linear approximation formula,
The control device is
When the slope and the intercept of the linear approximation formula are within predetermined normal ranges, it is determined that the combustion pressure sensor is normal,
An internal combustion engine control device that determines that the combustion pressure sensor has failed if at least one of the inclination and the intercept is outside the normal range. The control device for an internal combustion engine according to claim 1 or 2,
The control device for an internal combustion engine, wherein the combustion pressure sensor is attached to each of the plurality of cylinders. The control device for an internal combustion engine according to claim 1 or 2,
The control device for an internal combustion engine, wherein the combustion pressure sensor is attached to only one cylinder of the plurality of cylinders.