JP2020101160A - Abnormality diagnostic device for cylinder internal pressure sensor - Google Patents

Abstract

To enhance accuracy of a failure diagnosis of a cylinder internal pressure sensor.SOLUTION: An abnormality diagnostic device 100 for a cylinder internal pressure sensor includes a cylinder internal pressure sensor SW6 and a control section (ECU 10). The control section determines whether an abnormality condition related to the cylinder internal pressure sensor is satisfied on the basis of at least a signal of the cylinder internal pressure sensor on the timing delay side of a compression top dead center. The control section diagnoses the cylinder internal pressure sensor as being broken down in the case where the abnormality condition is satisfied when fuel supply to an engine 1 is being stopped, and does not diagnose the cylinder internal pressure sensor as being broken down in the case where the abnormality condition is satisfied when fuel is being supplied to the engine.SELECTED DRAWING: Figure 12

Description

The technology disclosed herein relates to an in-cylinder pressure sensor abnormality diagnosis device.

Patent Literature 1 describes an abnormality diagnosis device for an in-cylinder pressure sensor that detects the pressure in the combustion chamber of an internal combustion engine. This device diagnoses whether the internal combustion engine has an abnormality or the in-cylinder pressure sensor has an abnormality, based on the inclination of the change in the output value of the in-cylinder pressure sensor and the time lag of the output value of the in-cylinder pressure sensor. ..

JP, 2010-144670, A

The inventors of the present application have noticed that when the engine mounted on the vehicle is in a specific operating state, the cylinder pressure sensor may output an abnormal value although it is not a malfunction of the cylinder pressure sensor. .. When the in-cylinder pressure sensor outputs an abnormal value, it is preferable to avoid erroneous diagnosis that the in-cylinder pressure sensor is out of order.

The technique disclosed herein enhances the accuracy of failure diagnosis of the in-cylinder pressure sensor.

The inventors of the present application have noticed that the in-cylinder pressure sensor outputs an abnormal value at the time of abrupt recovery from, for example, fuel cut while the automobile is running. In other words, when the driver cuts the accelerator pedal abruptly during fuel cut to stop the supply of fuel to the engine, a relatively large amount of fuel is supplied to the low temperature combustion chamber and combustion is started. Then, the value of the signal of the in-cylinder pressure sensor may be lower than the actual pressure in the combustion chamber. The decrease in the value of the signal from the in-cylinder pressure sensor becomes remarkable especially in the expansion stroke.

According to the study by the inventors of the present application, this phenomenon is considered to have two causes related to the configuration of the in-cylinder pressure sensor.

Here, briefly explaining the configuration of the in-cylinder pressure sensor, the in-cylinder pressure sensor is generally a diaphragm disposed facing the combustion chamber, a piezoelectric element that outputs a weak current according to the deformation amount, A charge amplifier for accumulating charges from the piezoelectric element and outputting a signal corresponding to the amount of the charges as a signal of the in-cylinder pressure sensor is provided. A pedestal for transmitting the deflection of the diaphragm to the piezoelectric element is interposed between the diaphragm and the piezoelectric element. The piezoelectric element and the charge amplifier are connected by a conductive portion. The electrode of the piezoelectric element and the conductive portion are electrically connected by a compression spring. A preload is applied to the piezoelectric element, and when the diaphragm bends in response to the pressure in the combustion chamber, the piezoelectric element is pushed and crushed by the preload and the pressure in the combustion chamber.

When a relatively large amount of fuel is supplied to the engine during fuel cut and combustion with a large amount of heat suddenly starts, air column vibration (knocking) may occur in the combustion chamber.

The first reason why the in-cylinder pressure sensor outputs an abnormal value is that the diaphragm and the piezoelectric element vibrate due to air column vibration in the combustion chamber, and the contact state between the electrode of the piezoelectric element and the compression spring deteriorates. That is. The deterioration of the contact state between the electrodes of the piezoelectric element and the compression spring reduces the amount of electric charge supplied from the piezoelectric element to the charge amplifier. As a result, the value of the signal of the in-cylinder pressure sensor becomes lower than the actual pressure in the combustion chamber.

The second cause of the abnormal value output from the in-cylinder pressure sensor is that the diaphragm and the piezoelectric element vibrate due to air column vibration in the combustion chamber, and the relative position between the piezoelectric element and the pedestal is slightly deviated. That is, the preload applied to the element is reduced. When the preload applied to the piezoelectric element decreases, the amount of deformation of the piezoelectric element with respect to the amount of deflection of the diaphragm decreases. As a result, the value of the signal of the in-cylinder pressure sensor becomes lower than the actual pressure in the combustion chamber.

According to the study by the inventors of the present application, the in-cylinder pressure sensor outputs an abnormal value only temporarily when air column vibration occurs in the combustion chamber. Even if the in-cylinder pressure sensor outputs an abnormal value, the in-cylinder pressure sensor then outputs a normal value.

Further, according to a study by the inventors of the present application, when the insulating portion provided around the piezoelectric element of the in-cylinder pressure sensor and around the electrodes connected to the piezoelectric element is damaged by heat or the like, resulting in poor insulation. Although the reason is not clear, it was found that the value of the signal from the in-cylinder pressure sensor during the expansion stroke was reduced. The insulation failure is a failure of the in-cylinder pressure sensor. When the insulation failure occurs, the in-cylinder pressure sensor will not output a normal value thereafter.

Both the abnormal value output by the in-cylinder pressure sensor due to air column vibration and the abnormal value output by the in-cylinder pressure sensor due to insulation failure are common in that the value of the signal of the in-cylinder pressure sensor decreases. However, while it is temporary that the in-cylinder pressure sensor outputs an abnormal value due to air column vibration, it is temporary that the in-cylinder pressure sensor outputs an abnormal value due to insulation failure. No, continue. Therefore, when the in-cylinder pressure sensor outputs an abnormal value, it is necessary to determine whether it is due to air column vibration or insulation failure.

If the in-cylinder pressure sensor is out of order, the in-cylinder pressure sensor outputs an abnormal value regardless of whether the air-fuel mixture is burning in the combustion chamber or not. On the other hand, the in-cylinder pressure sensor outputting an abnormal value due to the air column vibration is limited to the case where the air-fuel mixture is burning in the combustion chamber.

Therefore, in the technology disclosed herein, when the in-cylinder pressure sensor outputs an abnormal value, the in-cylinder pressure sensor is temporarily caused by air column vibration depending on whether combustion is performed in the combustion chamber. It was decided to determine whether an abnormal value is being output or whether the in-cylinder pressure sensor is continuously outputting an abnormal value because the in-cylinder pressure sensor is out of order.

Specifically, the technology disclosed herein relates to an abnormality diagnosis device for a cylinder pressure sensor. The abnormality diagnosis device has a piezoelectric element to which a preload is applied, and a cylinder that outputs a signal corresponding to the pressure when the piezoelectric element is deformed by the pressure in the combustion chamber of an engine mounted on an automobile. An internal pressure sensor and a control unit that receives a signal from the in-cylinder pressure sensor and that operates the engine using at least the signal from the in-cylinder pressure sensor are provided.

Then, the control unit determines whether or not an abnormal condition related to the in-cylinder pressure sensor is satisfied based on at least a signal from the in-cylinder pressure sensor on the retard side of the compression top dead center, and the control unit Is diagnosing that the in-cylinder pressure sensor is out of order when the abnormal condition is satisfied while the supply of fuel to the engine is stopped, and the control unit is supplying fuel to the engine. When the abnormal condition is met at the time, the cylinder pressure sensor is not diagnosed as a failure.

According to this configuration, the control unit determines whether or not the abnormal condition related to the in-cylinder pressure sensor is satisfied, based on at least the signal of the in-cylinder pressure sensor on the retard side of the compression top dead center. The abnormal condition may be established due to a failure of the in-cylinder pressure sensor. Although the in-cylinder pressure sensor has not failed, the in-cylinder pressure sensor may output an abnormal value under a specific condition in the combustion chamber, whereby the abnormal condition may be satisfied.

The control unit diagnoses that the in-cylinder pressure sensor has a failure if an abnormal condition is satisfied while the fuel supply to the engine is stopped. When the in-cylinder pressure sensor is out of order, the in-cylinder pressure sensor outputs an abnormal value regardless of the state in the combustion chamber, for example, even when the air-fuel mixture is not burning in the combustion chamber. Therefore, when the abnormal condition is satisfied while the fuel supply to the engine is stopped, it is possible to diagnose that the in-cylinder pressure sensor is out of order. The "fault" is a state in which the in-cylinder pressure sensor continuously outputs an abnormal value, and is a state in which the in-cylinder pressure sensor is unlikely to recover so as to output a normal value.

The control unit does not diagnose that the in-cylinder pressure sensor is out of order if the abnormal condition is satisfied while fuel is being supplied to the engine. This is because, as described above, the in-cylinder pressure sensor may temporarily output an abnormal value when the combustion chamber is in a specific state. By not diagnosing that the in-cylinder pressure sensor is out of order, the control unit can suppress erroneous diagnosis. The abnormality diagnosis device for an in-cylinder pressure sensor having the above configuration can improve the accuracy of failure diagnosis of the in-cylinder pressure sensor.

The control unit may limit operation of the engine using a signal from the in-cylinder pressure sensor when the abnormal condition is satisfied while fuel is being supplied to the engine.

Since the in-cylinder pressure sensor outputs an abnormal value, the reliability of the signal output by the in-cylinder pressure sensor is low. According to the above configuration, the control unit limits the operation of the engine using the signal from the in-cylinder pressure sensor. It is possible to suppress the operation of the engine using the signal of the cylinder pressure sensor having low reliability. The "limitation" includes prohibiting the operation of the engine by using the signal from the cylinder pressure sensor. Further, the “limitation” also includes prohibiting the operation of the engine by using a part of the parameter calculated based on the signal of the in-cylinder pressure sensor.

If the abnormal condition is satisfied while fuel is being supplied to the engine, the control unit operates the engine using a signal from the in-cylinder pressure sensor. It may be temporarily restricted in.

As described above, it is temporary that the in-cylinder pressure sensor outputs an abnormal value while fuel is being supplied to the engine. The control unit temporarily limits the operation of the engine using the signal from the in-cylinder pressure sensor in the next cycle after the abnormal condition is satisfied. The control unit releases the restriction when the abnormal condition is no longer satisfied. As a result, the control unit can stably operate the engine.

When the control unit diagnoses that the in-cylinder pressure sensor is out of order, the operation of the engine by using the signal of the in-cylinder pressure sensor may be continuously limited after the diagnosis. Good.

When the in-cylinder pressure sensor is out of order, the in-cylinder pressure sensor continuously outputs an abnormal value. The control unit continuously limits the operation of the engine using the signal from the in-cylinder pressure sensor after determining that the in-cylinder pressure sensor is out of order. This allows the control unit to properly operate the engine.

When the control unit diagnoses that the in-cylinder pressure sensor is out of order, the control unit may notify through the notification unit.

Thereby, it is possible to inform the user that the in-cylinder pressure sensor is out of order. The user can eliminate the breakdown of the in-cylinder pressure sensor, for example, by loading the vehicle in a repair shop. When the failure of the in-cylinder pressure sensor is resolved, the control unit releases the above restriction.

The abnormal condition includes the value of the signal of the in-cylinder pressure sensor at the timing advanced by a specific crank angle with respect to the compression top dead center and the value at the timing delayed by the specific crank angle with respect to the compression top dead center. It may be that the difference from the value of the signal of the in-cylinder pressure sensor is larger than a predetermined threshold value.

When the supply of fuel to the combustion chamber is stopped, the change in pressure inside the combustion chamber is symmetrical or substantially symmetrical with respect to the compression top dead center. If the insulation failure of the in-cylinder pressure sensor occurs, as described above, the value of the signal of the in-cylinder pressure sensor in the expansion stroke decreases, and as a result, the symmetry of the change in the signal of the in-cylinder pressure sensor centered on the compression top dead center is broken. Will end up. In other words, if insulation failure occurs in the cylinder pressure sensor, the signal value of the cylinder pressure sensor at the timing advanced by a specific crank angle with respect to the compression top dead center and the same specific crank angle with respect to the compression top dead center are delayed. The difference from the value of the signal from the in-cylinder pressure sensor at the angled timing becomes large. The control unit diagnoses a failure of the in-cylinder pressure sensor based on the difference, so that the failure of the in-cylinder pressure sensor can be accurately diagnosed.

Further, even when the in-cylinder pressure sensor outputs an abnormal value due to air column vibration in the combustion chamber, the value of the signal of the in-cylinder pressure sensor in the expansion stroke decreases. As in the case where insulation failure occurs in the cylinder pressure sensor, the signal value of the cylinder pressure sensor at the timing advanced by a specific crank angle with respect to the compression top dead center and the same specific crank angle with respect to the compression top dead center The difference from the value of the signal from the in-cylinder pressure sensor at the timing that is delayed by a large amount increases. Based on the difference, the control unit can also accurately determine that the in-cylinder pressure sensor outputs an abnormal value due to air column vibration in the combustion chamber.

As described above, according to the abnormality diagnosis device for the in-cylinder pressure sensor, the accuracy of failure diagnosis of the in-cylinder pressure sensor can be improved.

FIG. 1 is a diagram illustrating the configuration of the engine. FIG. 2 is a diagram illustrating the configuration of the combustion chamber, in which the upper diagram is a plan view equivalent view of the combustion chamber and the lower diagram is a sectional view taken along line II-II. FIG. 3 is a block diagram illustrating the configuration of an engine control device. FIG. 4 is a cross-sectional explanatory view illustrating the configuration of the in-cylinder pressure sensor. FIG. 5: is a figure which illustrates the waveform of SPCCI combustion. FIG. 6 is a block diagram illustrating the functional configuration of the control unit of the engine. FIG. 7 is a block diagram illustrating the functional configuration of the abnormality diagnosing device for the in-cylinder pressure sensor. FIG. 8: is a figure which illustrates the waveform of the signal which a cylinder pressure sensor outputs at the time of normality, and the waveform of the signal which outputs at the time of failure. FIG. 9 is a diagram exemplifying a waveform of a signal output by the in-cylinder pressure sensor in a normal state and a waveform of a signal output in an abnormal state. FIG. 10 is an explanatory view showing in simplified form one of the causes of the abnormal value output from the in-cylinder pressure sensor. FIG. 11 is a diagram comparing changes in the indicated mean effective pressure value calculated based on the normal value of the in-cylinder pressure sensor and changes in the indicated mean effective pressure value calculated based on the abnormal value of the in-cylinder pressure sensor. Is. FIG. 12 is a flowchart exemplifying a procedure of failure diagnosis of the in-cylinder pressure sensor.

Hereinafter, an embodiment of an abnormality diagnosis device for an in-cylinder pressure sensor will be described in detail with reference to the drawings. The following description is an example of an abnormality diagnosis device for an in-cylinder pressure sensor.

FIG. 1 is a diagram illustrating a configuration of a compression ignition type engine system including an abnormality diagnosis device for an in-cylinder pressure sensor. FIG. 2 is a diagram illustrating the configuration of the combustion chamber of the engine. The intake side in FIG. 1 is the left side of the paper surface, and the exhaust side is the right side of the paper surface. The intake side in FIG. 2 is the right side of the page, and the exhaust side is the left side of the page. FIG. 3 is a block diagram illustrating the configuration of an engine control device.

The engine 1 is a four-stroke reciprocating engine that operates by the combustion chamber 17 repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The engine 1 is mounted on a four-wheeled vehicle. The vehicle runs as the engine 1 drives. The fuel of the engine 1 is gasoline in this configuration example. The fuel may be a liquid fuel containing at least gasoline. The fuel may be, for example, gasoline containing bioethanol or the like.

(Engine configuration)
The engine 1 includes a cylinder block 12 and a cylinder head 13 mounted on the cylinder block 12. A plurality of cylinders 11 are formed inside the cylinder block 12. 1 and 2, only one cylinder 11 is shown. The engine 1 is a multi-cylinder engine.

A piston 3 is slidably inserted in each cylinder 11. The piston 3 is connected to the crankshaft 15 via a connecting rod 14. The piston 3 defines a combustion chamber 17 together with the cylinder 11 and the cylinder head 13. The term "combustion chamber" may be used in a broad sense. That is, the “combustion chamber” may mean a space formed by the piston 3, the cylinder 11, and the cylinder head 13 regardless of the position of the piston 3. Further, in the following description, the term “in-cylinder” may be used as a word having substantially the same meaning as the combustion chamber.

The lower surface of the cylinder head 13, that is, the ceiling surface of the combustion chamber 17 is composed of an inclined surface 1311 and an inclined surface 1312, as shown in the lower diagram of FIG. The inclined surface 1311 has an upward slope from the intake side toward the axis X2 of the injector 6 described later. The inclined surface 1312 has an upward slope from the exhaust side toward the axis X2 of the injector 6. The ceiling surface of the combustion chamber 17 has a so-called pent roof shape.

The upper surface of the piston 3 is raised toward the ceiling surface of the combustion chamber 17. A cavity 31 is formed on the upper surface of the piston 3. The cavity 31 is recessed from the upper surface of the piston 3. The cavity 31 has a shallow dish shape in this configuration example. The center of the cavity 31 is displaced toward the exhaust side from the central axis X1 of the cylinder 11.

The geometric compression ratio of the engine 1 is set to 10 or more and 30 or less. As will be described later, the engine 1 performs SPCCI combustion that is a combination of SI combustion and CI combustion. SPCCI combustion controls CI combustion by utilizing heat generation and pressure increase due to SI combustion. The engine 1 is a compression ignition type engine. However, in this engine 1, it is not necessary to raise the temperature of the combustion chamber 17 when the piston 3 reaches the compression top dead center. The engine 1 can set the geometric compression ratio relatively low. A low geometric compression ratio is advantageous for reducing cooling loss and mechanical loss. The geometric compression ratio of the engine 1 is 14 to 17 in the regular specification (low octane fuel with a fuel octane value of about 91), and is 15 in the high octane specification (high octane fuel with a fuel octane value of about 96). It may be -18.

An intake port 18 is formed in the cylinder head 13 for each cylinder 11. Although illustration is omitted, the intake port 18 has two intake ports 18, a first intake port and a second intake port. The intake port 18 communicates with the combustion chamber 17. The intake port 18 is a so-called tumble port. That is, the intake port 18 has a shape such that a tumble flow is formed in the combustion chamber 17.

An intake valve 21 is arranged in the intake port 18. The intake valve 21 opens and closes between the combustion chamber 17 and the intake port 18. The intake valve 21 is opened and closed at a predetermined timing by a valve mechanism. The valve operating mechanism may be a variable valve operating mechanism that makes valve timing and/or valve lift variable. In this configuration example, as shown in FIG. 3, the variable valve mechanism has an intake electric S-VT (Sequential-Valve Timing) 23. The intake electric S-VT 23 continuously changes the phase of the intake camshaft within a predetermined range. The valve opening timing and valve closing timing of the intake valve 21 continuously change. The intake valve operating mechanism may have a hydraulic S-VT instead of the electric S-VT.

An exhaust port 19 is also formed in the cylinder head 13 for each cylinder 11. The exhaust port 19 also has two exhaust ports 19, a first exhaust port and a second exhaust port. The exhaust port 19 communicates with the combustion chamber 17.

An exhaust valve 22 is arranged in the exhaust port 19. The exhaust valve 22 opens and closes between the combustion chamber 17 and the exhaust port 19. The exhaust valve 22 is opened and closed at a predetermined timing by a valve mechanism. The valve operating mechanism may be a variable valve operating mechanism that makes valve timing and/or valve lift variable. In this configuration example, as shown in FIG. 3, the variable valve mechanism has an exhaust electric S-VT 24. The exhaust electric S-VT 24 continuously changes the phase of the exhaust camshaft within a predetermined range. The valve opening timing and the valve closing timing of the exhaust valve 22 continuously change. The exhaust valve mechanism may have a hydraulic S-VT instead of the electric S-VT.

The intake electric S-VT 23 and the exhaust electric S-VT 24 adjust the length of the overlap period in which both the intake valve 21 and the exhaust valve 22 open. By increasing the length of the overlap period, the residual gas in the combustion chamber 17 can be scavenged. Further, the internal EGR (Exhaust Gas Recirculation) gas can be introduced into the combustion chamber 17 by adjusting the length of the overlap period. The intake electric S-VT 23 and the exhaust electric S-VT 24 form an internal EGR system. Note that the internal EGR system is not always configured by S-VT.

An injector 6 is attached to the cylinder head 13 for each cylinder 11. The injector 6 directly injects fuel into the combustion chamber 17. The injector 6 is an example of a fuel injection unit. The injector 6 is arranged at the intersection of the inclined surface 1311 and the inclined surface 1312. As shown in FIG. 2, the axis X2 of the injector 6 is located closer to the exhaust side than the central axis X1 of the cylinder 11. The axis X2 of the injector 6 is parallel to the central axis X1. The axis X2 of the injector 6 and the center of the cavity 31 coincide. The injector 6 faces the cavity 31. The axis X2 of the injector 6 may coincide with the central axis X1 of the cylinder 11. In that case, the axis X2 of the injector 6 and the center of the cavity 31 may coincide with each other.

Although not shown in detail, the injector 6 is composed of a multi-injection type fuel injection valve having a plurality of injection ports. The injector 6 injects the fuel so that the fuel spray spreads radially from the center of the combustion chamber 17, as shown by the chain double-dashed line in FIG. In this configuration example, the injector 6 has ten injection holes, and the injection holes are arranged at equal angles in the circumferential direction.

A fuel supply system 61 is connected to the injector 6. The fuel supply system 61 includes a fuel tank 63 and a fuel supply passage 62 that connects the fuel tank 63 and the injector 6 to each other. The fuel tank 63 stores fuel. A fuel pump 65 and a common rail 64 are provided in the fuel supply path 62. The fuel pump 65 pumps fuel to the common rail 64. The fuel pump 65 is a plunger type pump driven by the crankshaft 15 in this configuration example. The common rail 64 stores the fuel pumped from the fuel pump 65 at a high fuel pressure. When the injector 6 opens, the fuel stored in the common rail 64 is injected into the combustion chamber 17 from the injection port of the injector 6. The fuel supply system 61 is capable of supplying fuel with a high pressure of 30 MPa or higher to the injector 6. The pressure of the fuel supplied to the injector 6 may be changed according to the operating state of the engine 1. The configuration of the fuel supply system 61 is not limited to the above configuration.

An ignition plug 25 is attached to the cylinder head 13 for each cylinder 11. The spark plug 25 compulsorily ignites the air-fuel mixture in the combustion chamber 17. The spark plug 25 is an example of an ignition unit. In this configuration example, the spark plug 25 is arranged closer to the intake side than the central axis X1 of the cylinder 11. The spark plug 25 is located between the two intake ports 18. The spark plug 25 is attached to the cylinder head 13 while inclining in a direction approaching the center of the combustion chamber 17 from above to below. As shown in FIG. 2, the electrode of the spark plug 25 faces the inside of the combustion chamber 17 and is located near the ceiling surface of the combustion chamber 17. The spark plug 25 may be arranged on the exhaust side of the central axis X1 of the cylinder 11. Further, the spark plug 25 may be arranged on the central axis X1 of the cylinder 11.

An intake passage 40 is connected to one side surface of the engine 1. The intake passage 40 communicates with the intake port 18 of each cylinder 11. The gas that enters the combustion chamber 17 flows through the intake passage 40. An air cleaner 41 is arranged at the upstream end of the intake passage 40. The air cleaner 41 filters fresh air. A surge tank 42 is arranged near the downstream end of the intake passage 40. The intake passage 40 downstream of the surge tank 42 constitutes an independent passage branched for each cylinder 11. The downstream end of the independent passage is connected to the intake port 18 of each cylinder 11.

A throttle valve 43 is arranged between the air cleaner 41 and the surge tank 42 in the intake passage 40. The throttle valve 43 adjusts the amount of fresh air introduced into the combustion chamber 17 by adjusting the opening of the valve.

A supercharger 44 is arranged in the intake passage 40 downstream of the throttle valve 43. The supercharger 44 supercharges the gas that enters the combustion chamber 17. In this configuration example, the supercharger 44 is a mechanical supercharger driven by the engine 1. The mechanical supercharger 44 may be a roots type, a Risholm type, a vane type, or a centrifugal type.

An electromagnetic clutch 45 is provided between the supercharger 44 and the engine 1. The electromagnetic clutch 45 transmits the driving force from the engine 1 to the supercharger 44 or interrupts the transmission of the driving force between the supercharger 44 and the engine 1. As will be described later, the ECU 10 switches connection and disconnection of the electromagnetic clutch 45 to switch the supercharger 44 between on and off.

An intercooler 46 is arranged downstream of the supercharger 44 in the intake passage 40. The intercooler 46 cools the gas compressed by the supercharger 44. The intercooler 46 may be, for example, a water-cooled type or an oil-cooled type.

A bypass passage 47 is connected to the intake passage 40. The bypass passage 47 connects the upstream portion of the supercharger 44 and the downstream portion of the intercooler 46 in the intake passage 40 to each other. The bypass passage 47 bypasses the supercharger 44 and the intercooler 46. An air bypass valve 48 is arranged in the bypass passage 47. The air bypass valve 48 regulates the flow rate of gas flowing through the bypass passage 47.

The ECU 10 fully opens the air bypass valve 48 when the supercharger 44 is turned off (that is, when the electromagnetic clutch 45 is disengaged). The gas flowing through the intake passage 40 bypasses the supercharger 44 and enters the combustion chamber 17 of the engine 1. The engine 1 operates in a non-supercharged state, that is, in a state of natural intake.

When the supercharger 44 is turned on, the engine 1 operates in the supercharged state. The ECU 10 adjusts the opening degree of the air bypass valve 48 when the supercharger 44 is turned on (that is, when the electromagnetic clutch 45 is connected). A part of the gas that has passed through the supercharger 44 flows back to the upstream side of the supercharger 44 through the bypass passage 47. When the ECU 10 adjusts the opening degree of the air bypass valve 48, the pressure of the gas entering the combustion chamber 17 changes. That is, the boost pressure changes. It should be noted that supercharging is defined as a time when the pressure inside the surge tank 42 exceeds atmospheric pressure, and non-supercharging is a time when the pressure inside the surge tank 42 becomes equal to or lower than atmospheric pressure. Good.

In this configuration example, the supercharger 44, the bypass passage 47, and the air bypass valve 48 form a supercharge system 49.

The engine 1 has a swirl generating unit that generates a swirl flow in the combustion chamber 17. The swirl flow flows as shown by an outline arrow in FIG. The swirl generator has a swirl control valve 56 attached to the intake passage 40. Although not shown in detail, the swirl control valve 56 is provided in a secondary passage of a primary passage connected to one of the two intake ports 18 and a secondary passage connected to the other intake port 18. It is arranged. The swirl control valve 56 is an opening control valve capable of narrowing the cross section of the secondary passage. When the opening degree of the swirl control valve 56 is small, the intake flow rate entering the combustion chamber 17 from one intake port 18 is relatively large and the intake flow rate entering the combustion chamber 17 from the other intake port 18 is relatively small. The swirl flow in the combustion chamber 17 becomes stronger. If the opening degree of the swirl control valve 56 is large, the intake flow rates entering the combustion chamber 17 from the two intake ports 18 become substantially equal, so the swirl flow in the combustion chamber 17 becomes weak. When the swirl control valve 56 is fully opened, the swirl flow does not occur.

An exhaust passage 50 is connected to the other side surface of the engine 1. The exhaust passage 50 communicates with the exhaust port 19 of each cylinder 11. The exhaust passage 50 is a passage through which the exhaust gas discharged from the combustion chamber 17 flows. Although not shown in detail, the upstream portion of the exhaust passage 50 constitutes an independent passage branched for each cylinder 11. The upstream end of the independent passage is connected to the exhaust port 19 of each cylinder 11.

An exhaust gas purification system having a plurality of catalytic converters is arranged in the exhaust passage 50. Although not shown, the upstream catalytic converter is arranged in the engine room. The upstream catalytic converter has a three-way catalyst 511 and a GPF (Gasoline Particulate Filter) 512. The downstream catalytic converter is arranged outside the engine room. The downstream catalytic converter has a three-way catalyst 513. The exhaust gas purification system is not limited to the configuration shown in the figure. For example, the GPF may be omitted. Further, the catalytic converter is not limited to one having a three-way catalyst. Furthermore, the arrangement order of the three-way catalyst and the GPF may be changed appropriately.

An EGR passage 52 is connected between the intake passage 40 and the exhaust passage 50. The EGR passage 52 is a passage for returning a part of the exhaust gas to the intake passage 40. The EGR passage 52 constitutes an external EGR system. The upstream end of the EGR passage 52 is connected between the upstream catalytic converter and the downstream catalytic converter in the exhaust passage 50. The downstream end of the EGR passage 52 is connected to the upstream portion of the supercharger 44 in the intake passage 40. The EGR gas flowing through the EGR passage 52 enters the upstream portion of the supercharger 44 in the intake passage 40 without passing through the air bypass valve 48 in the bypass passage 47.

A water-cooled EGR cooler 53 is arranged in the EGR passage 52. The EGR cooler 53 cools the exhaust gas. An EGR valve 54 is also arranged in the EGR passage 52. The EGR valve 54 regulates the flow rate of exhaust gas flowing through the EGR passage 52. By adjusting the opening degree of the EGR valve 54, it is possible to adjust the recirculation amount of the cooled exhaust gas, that is, the external EGR gas.

The engine 1 has an external EGR system and an internal EGR system as the EGR system 55. The external EGR system can supply exhaust gas having a temperature lower than that of the internal EGR system to the combustion chamber 17.

The compression ignition engine control device includes an ECU (Engine Control Unit) 10 for operating the engine 1. The ECU 10 is a known microcomputer-based control unit, and as shown in FIG. 3, a microcomputer 101 including a central processing unit (CPU) that executes a program, and a RAM (Random), for example. The memory 102 includes an access memory) and a ROM (Read Only Memory) and stores programs and data, and an I/F circuit 103 that inputs and outputs electric signals.

As shown in FIGS. 1 and 3, various sensors SW1 to SW17 are connected to the ECU 10. The sensors SW1 to SW17 output signals to the ECU 10. The sensor includes the following sensors.

Air flow sensor SW1: A first intake air temperature sensor SW2 arranged downstream of the air cleaner 41 in the intake passage 40 and outputting a signal corresponding to the flow rate of fresh air flowing in the intake passage 40, downstream of the air cleaner 41 in the intake passage 40. And outputs a signal corresponding to the temperature of the fresh air flowing through the intake passage 40, downstream of the connection position of the EGR passage 52 in the intake passage 40 and upstream of the supercharger 44. A second intake air temperature sensor SW4 that is arranged and outputs a signal corresponding to the pressure of the gas that enters the supercharger 44: downstream of the supercharger 44 in the intake passage 40 and upstream of the connection position of the bypass passage 47. The intake pressure sensor SW5, which is arranged and outputs a signal corresponding to the temperature of the gas flowing out from the supercharger 44, is attached to the surge tank 42 and outputs a signal corresponding to the pressure of the gas downstream of the supercharger 44. In-cylinder pressure sensor SW6: attached to the cylinder head 13 corresponding to each cylinder 11 and outputting a signal corresponding to the pressure in each combustion chamber 17 Exhaust temperature sensor SW7: disposed in the exhaust passage 50 and combustion chamber Outputs a signal corresponding to the temperature of the exhaust gas discharged from 17. Linear O ₂ sensor SW8: is arranged upstream of the upstream catalytic converter in the exhaust passage 50 and outputs a signal corresponding to the oxygen concentration in the exhaust gas Lambda O ₂ sensor SW9: a water temperature sensor SW10 arranged downstream of the three-way catalyst 511 in the upstream catalytic converter and outputting a signal corresponding to the oxygen concentration in the exhaust gas, and attached to the engine 1 and the temperature of the cooling water. Crank angle sensor SW11 attached to the engine 1 and outputting a signal corresponding to the rotation angle of the crankshaft 15 accelerator opening sensor SW12 attached to the accelerator pedal mechanism and operating the accelerator pedal Intake cam angle sensor SW13, which outputs a signal corresponding to the accelerator opening proportional to the amount, is attached to the engine 1, and outputs a signal corresponding to the rotation angle of the intake camshaft Exhaust cam angle sensor SW14: Attached to the engine 1. EGR differential pressure sensor SW15 that outputs a signal corresponding to the rotation angle of the exhaust camshaft: a fuel pressure sensor SW16 that is arranged in the EGR passage 52 and that outputs a signal corresponding to the differential pressure upstream and downstream of the EGR valve 54 : Attached to the common rail 64 of the fuel supply system 61 and Third intake air temperature sensor SW17 that outputs a signal corresponding to the pressure of the fuel supplied to the ejector 6: the temperature of the gas in the surge tank 42 and the temperature of the intake air entering the combustion chamber 17, in other words, Output the corresponding signal.

The ECU 10 determines the operating state of the engine 1 based on the signals from these sensors SW1 to SW17, and calculates the control amount of each device according to a predetermined control logic. The control logic is stored in the memory 102. The control logic includes calculating a target amount and/or a control amount using the map stored in the memory 102.

The ECU 10 sends an electric signal relating to the calculated control amount to the injector 6, the spark plug 25, the intake electric S-VT 23, the exhaust electric S-VT 24, the fuel supply system 61, the throttle valve 43, the EGR valve 54, and the supercharger 44. To the electromagnetic clutch 45, the air bypass valve 48, and the swirl control valve 56.

For example, the ECU 10 sets the target torque of the engine 1 and determines the target boost pressure based on the signal from the accelerator opening sensor SW12 and the map. Then, the ECU 10 feeds back the opening degree of the air bypass valve 48 based on the target supercharging pressure and the differential pressure across the supercharger 44 obtained from the signals of the first pressure sensor SW3 and the intake pressure sensor SW5. Take control. By this feedback control, the boost pressure becomes the target boost pressure.

Further, the ECU 10 sets the target EGR rate (that is, the ratio of EGR gas to all the gas in the combustion chamber 17) based on the operating state of the engine 1 and the map. Then, the ECU 10 determines the target EGR gas amount based on the target EGR rate and the intake air amount based on the signal from the accelerator opening sensor SW12, and the differential pressure across the EGR valve 54 obtained from the signal from the EGR differential pressure sensor SW15. Feedback control for adjusting the opening degree of the EGR valve 54 is performed based on By this feedback control, the amount of external EGR gas that enters the combustion chamber 17 becomes the target EGR gas amount.

Further, the ECU 10 executes the air-fuel ratio feedback control when the predetermined control condition is satisfied. Specifically, the ECU 10 controls the injector 6 so that the air-fuel ratio of the mixture becomes a desired value based on the oxygen concentration in the exhaust gas obtained from the signals of the linear O ₂ sensor SW8 and the lambda O ₂ sensor SW9. Adjust the fuel injection amount.

Details of other control of the engine 1 by the ECU 10 will be described later.

A notification unit 57 is also connected to the ECU 10. The notification unit is composed of, for example, a warning lamp provided on the instrument panel. As described later, when the abnormality diagnosing device 100 for the in-cylinder pressure sensor SW6 diagnoses a failure in the in-cylinder pressure sensor SW6, the notification unit 57 notifies the user.

(Structure of in-cylinder pressure sensor)
FIG. 4 illustrates the configuration of the in-cylinder pressure sensor SW6. The in-cylinder pressure sensor SW6 has a diaphragm 71 that is disposed so as to face the inside of the combustion chamber 17. The diaphragm 71 is made of a flexible material. The diaphragm 71 is arranged at the tip of the in-cylinder pressure sensor SW6. The peripheral portion of the diaphragm 71 is supported by the housing. The housing has an outer housing 72 and an inner housing 73. When the pressure in the combustion chamber 17 increases, the outer surface of the diaphragm 71 is pushed, and the central portion of the diaphragm 71 not supported by the outer housing 72 and the inner housing 73 bends. A thin portion 712 is provided around the center of the diaphragm 71.

Although not shown, the outer housing 72 is fixed to the cylinder head 13 of the engine 1. The outer housing 72 has a tubular shape with an open end. The diaphragm 71 is attached to the tip surface of the outer housing 72. The peripheral portion of the diaphragm 71 is fixed to the outer housing 72 by welding.

The inner housing 73 is inserted in the outer housing 72. The inner housing 73 is located at the tip of the outer housing 72. The inner housing 73 is configured by combining a plurality of parts. The inner housing 73 is also tubular. The peripheral edge of the diaphragm 71 is also fixed to the inner housing 73 by welding.

The inner housing 73 is biased by the biasing member 74 toward the tip of the in-cylinder pressure sensor SW6. The urging member 74 is disposed inside the outer housing 72, closer to the base end side of the in-cylinder pressure sensor SW6 than the inner housing 73 (that is, the upper side in FIG. 4).

A piezoelectric element 75 is arranged inside the inner housing 73. The piezoelectric element 75 deforms as the diaphragm 71 bends, and outputs a weak current according to the amount of deformation. The piezoelectric element 75 is preloaded by the biasing member 74.

A pedestal 76 is attached to the tip of the piezoelectric element 75. The pedestal 76 has a protrusion 761 at the center thereof that protrudes toward the tip of the in-cylinder pressure sensor SW6. The protruding portion 761 is located in a through hole 731 provided in the tip portion of the inner housing 73.

A central protrusion 711 that projects toward the base end of the in-cylinder pressure sensor SW6 is provided integrally with the diaphragm 71 at the center of the inner surface of the diaphragm 71. The central protrusion 711 of the diaphragm 71 and the protrusion 761 of the pedestal 76 are in contact with each other. When the central portion of the diaphragm 71 bends, the pedestal 76 is pushed toward the base end of the in-cylinder pressure sensor SW6 by the central protrusion 711. The piezoelectric element 75 to which the preload is applied is pushed by the pedestal 76 and crushed.

An electrode 77 is attached to the base end of the piezoelectric element 75. The weak current of the piezoelectric element 75 is output through the electrode 77.

The base end portion of the electrode 77 is supported by the electrode support portion 78. The electrode support portion 78 is also configured by combining a plurality of members. The electrode support portion 78 is welded to the inner housing 73. A conductive portion 79 is arranged inside the electrode support portion 78. The conductive portion 79 extends toward the base end of the in-cylinder pressure sensor SW6. The base end of the conductive portion 79 is connected to the charge amplifier 710 of the in-cylinder pressure sensor SW6. The charge amplifier 710 stores the charge from the piezoelectric element 75 and outputs a signal corresponding to the amount of the charge to the ECU 10 as a signal of the in-cylinder pressure sensor SW6.

A compression spring 791 is arranged between the electrode 77 and the conductive portion 79. The compression spring 791 electrically connects the electrode 77 and the conductive portion 79.

An annular insulating portion 713 is provided between the integrated pedestal 76, the piezoelectric element 75, the electrode 77, and the inner housing 73. The insulating portion 713 is a portion colored in black in FIG.

(SPCCI combustion concept)
The engine 1 performs combustion by compression self-ignition when in a predetermined operating state mainly for the purpose of improving fuel efficiency and exhaust gas performance. In the combustion due to self-ignition, the timing of self-ignition greatly changes when the temperature in the combustion chamber 17 before the start of compression varies. Therefore, the engine 1 performs SPCCI combustion that is a combination of SI combustion and CI combustion.

In SPCCI combustion, the spark plug 25 compulsorily ignites the air-fuel mixture in the combustion chamber 17, so that the air-fuel mixture undergoes SI combustion due to flame propagation, and the heat generated by the SI combustion causes heat in the combustion chamber 17 to rise. In this mode, the temperature rises and the pressure in the combustion chamber 17 rises due to flame propagation, so that the unburned air-fuel mixture undergoes CI combustion by self-ignition.

By adjusting the calorific value of SI combustion, it is possible to absorb the variation in temperature in the combustion chamber 17 before the start of compression. By the ECU 10 adjusting the ignition timing, the air-fuel mixture can be self-ignited at the target timing.

In SPCCI combustion, heat generation during SI combustion is milder than that during CI combustion. In the waveform of the heat release rate (dQ/dθ) in SPCCI combustion, the rising slope is smaller than the rising slope in the CI combustion waveform, as illustrated in FIG. Further, the pressure fluctuation rate (dp/dθ) in the combustion chamber 17 is also gentler during SI combustion than during CI combustion.

When the unburned air-fuel mixture self-ignites after the start of SI combustion, the slope of the heat generation rate waveform may change from small to large at the timing of self-ignition. The heat release rate waveform may have an inflection point X at the timing when CI combustion starts.

After the start of CI combustion, SI combustion and CI combustion are performed in parallel. Since CI combustion generates more heat than SI combustion, the heat generation rate is relatively large. However, since the CI combustion is performed after the compression top dead center, it is possible to avoid the slope of the heat generation rate waveform from becoming too large. The pressure fluctuation rate (dp/dθ) during CI combustion also becomes relatively gentle.

The pressure fluctuation rate (dp/dθ) can be used as an index representing combustion noise. As described above, since the SPCCI combustion can reduce the pressure fluctuation rate (dp/dθ), it becomes possible to avoid excessive combustion noise. The combustion noise of the engine 1 is suppressed below the allowable level.

When the CI combustion ends, the SPCCI combustion ends. CI combustion has a shorter combustion period than SI combustion. SCCCI combustion has an earlier combustion end timing than SI combustion.

The waveform of the heat generation rate in SPCCI combustion, a first heat generation rate portion Q _SI formed by SI combustion, and the second heat generating section Q _CI formed by CI combustion, but so as to be continuous in this order Has been formed.

Here, the SI rate is defined as a parameter indicating the characteristics of SPCCI combustion. The applicant of the present application defines the SI rate as an index related to the ratio of the amount of heat generated by SI combustion to the total amount of heat generated by SPCCI combustion. The SI rate is a heat quantity ratio generated by two combustions having different combustion modes. When the SI rate is high, the SI combustion rate is high, and when the SI rate is low, the CI combustion rate is high. A high proportion of SI combustion in SPCCI combustion is advantageous for suppressing combustion noise. A high ratio of CI combustion in SPCCI combustion is advantageous for improving the fuel efficiency of the engine 1.

The SI rate may be defined as the ratio of the amount of heat generated by SI combustion to the amount of heat generated by CI combustion. That is, in SPCCI combustion, the crank angle at which the CI combustion starts as CI combustion start time Shitaci, in the waveform 801 shown in FIG. 5, the area _{Q SI} the SI combustion also advance side than Shitaci, slow including Shitaci angle from the area _{Q CI} of CI combustion is a side, it may be SI index ₌ Q SI _{/ Q CI.}

(Engine control logic)
FIG. 6 is a block diagram illustrating a functional configuration of the ECU 10 that executes the control logic of the engine 1. The ECU 10 operates the engine 1 according to the control logic stored in the memory 102. Specifically, the ECU 10 determines the operating state of the engine 1 based on the signals of the respective sensors SW1 to SW17, and burns the combustion in the combustion chamber 17 so that the combustion has an SI rate according to the operating state. The calculation for adjusting the state quantity in the chamber 17, adjusting the injection quantity, adjusting the injection timing, and adjusting the ignition timing is performed.

The ECU 10 controls SPCCI combustion by using two parameters, SI rate and θci. Specifically, the ECU 10 sets a target SI rate and a target θci corresponding to the operating state of the engine 1, and sets the combustion chamber 17 so that the actual SI rate matches the target SI rate and the actual θci becomes the target θci. The internal temperature is adjusted and the ignition timing is adjusted. The temperature in the combustion chamber 17 is adjusted by adjusting the temperature and/or the amount of exhaust gas entering the combustion chamber 17.

The ECU 10 first reads the signals of the sensors SW1 to SW17 through the I/F circuit 103. Next, the target SI rate/target θci setting unit 101a in the microcomputer 101 of the ECU 10 determines the operating state of the engine 1 based on the signals of the sensors SW1 to SW17, and at the same time, the target SI rate (that is, the target calorific value ratio). And the target CI combustion start timing θci are set. The target SI rate is set according to the operating state of the engine 1. The target SI rate is stored in the target SI rate storage unit 1021 of the memory 102. The target SI rate/target θci setting unit 101a sets the target SI rate low when the load of the engine 1 is low, and sets the target SI rate high when the load of the engine 1 is high. When the load of the engine 1 is low, the ratio of CI combustion in SPCCI combustion is increased to achieve both suppression of combustion noise and improvement of fuel efficiency. When the load on the engine 1 is high, increasing the proportion of SI combustion in SPCCI combustion is advantageous for suppressing combustion noise.

As described above, θci means the crank angle timing at which CI combustion starts in SPCCI combustion (see FIG. 5). The target θci is also set according to the operating state of the engine 1. The target θci is stored in the target θci storage unit 1022 of the memory 102. When θci is on the retard side, combustion noise is reduced. When θci is on the advance side, the fuel efficiency performance of the engine 1 is improved. The target θci is set to the advance side as much as possible within the range where the combustion noise can be suppressed to the allowable level or less.

The target in-cylinder state amount setting unit 101b sets a target in-cylinder state amount for realizing the set target SI rate and target θci based on the model stored in the memory 102. Specifically, the target in-cylinder state quantity setting unit 101b sets a target temperature, a target pressure, and a target state quantity in the combustion chamber 17.

The in-cylinder state quantity control unit 101c opens the EGR valve 54, the throttle valve 43, the air bypass valve 48, and the swirl control valve 56 to achieve the target in-cylinder state quantity. Degree, the phase angle of the intake electric S-VT 23 (that is, the valve timing of the intake valve 21), and the phase angle of the exhaust electric S-VT 24 (that is, the valve timing of the exhaust valve 22) are set. The in-cylinder state amount control unit 101c sets the control amounts of these devices based on the map stored in the memory 102. The in-cylinder state amount control unit 101c, based on the set control amount, the EGR valve 54, the throttle valve 43, the air bypass valve 48, the swirl control valve (SCV) 56, the intake electric S-VT23, and the exhaust electric S-. The control signal is output to the VT 24. By operating each device based on the signal from the ECU 10, the state quantity in the combustion chamber 17 becomes the target state quantity.

The in-cylinder state quantity control unit 101c further calculates a predicted value of the state quantity in the combustion chamber 17 and an estimated value of the state quantity based on the set control amounts of the respective devices. The state quantity predicted value is a value that predicts the state quantity in the combustion chamber 17 before the intake valve 21 is closed. The state quantity predicted value is used to set the fuel injection quantity in the intake stroke, as will be described later. The state quantity estimated value is a value obtained by estimating the state quantity in the combustion chamber 17 after the intake valve 21 is closed. The state quantity estimated value is used to set the fuel injection amount and the ignition timing in the compression stroke, as will be described later.

The first injection amount setting unit 101d sets the fuel injection amount during the intake stroke based on the state amount predicted value. When performing split injection during the intake stroke, the injection amount of each injection is set. When the fuel is not injected during the intake stroke, the first injection amount setting unit 101d sets the fuel injection amount to zero. The first injection control unit 101e outputs a control signal to the injector 6 so that the injector 6 injects fuel into the combustion chamber 17 at a predetermined injection timing. The first injection control unit 101e also outputs the fuel injection result during the intake stroke.

The second injection amount setting unit 101f sets the fuel injection amount during the compression stroke based on the state quantity estimation value and the fuel injection result during the intake stroke. When the fuel is not injected during the compression stroke, the second injection amount setting unit 101f sets the fuel injection amount to zero. The second injection control unit 101g outputs a control signal to the injector 6 so that the injector 6 injects fuel into the combustion chamber 17 at an injection timing based on a preset map. The second injection control unit 101g also outputs the fuel injection result during the compression stroke.

The ignition timing setting unit 101h sets the ignition timing based on the state quantity estimated value and the fuel injection result during the compression stroke. The ignition control unit 101i outputs a control signal to the ignition plug 25 so that the ignition plug 25 ignites the air-fuel mixture in the combustion chamber 17 at the set ignition timing.

Here, the control logic of the engine 1 adjusts the SI rate and θci by adjusting the ignition timing. More specifically, the ECU 10 calculates an index related to the combustion waveform based on the signal from the in-cylinder pressure sensor SW6. The indexes related to the combustion waveform include the combustion center of gravity and the indicated mean effective pressure in addition to the above-mentioned θci. The ECU 10 adjusts the ignition timing of the next cycle based on the index related to the combustion waveform (that is, feedback control). Feedback control using an index related to the combustion waveform finely adjusts the self-ignition timing of SPCCI combustion.

When the spark plug 25 ignites the air-fuel mixture, SI combustion or SPCCI combustion is performed in the combustion chamber 17. The in-cylinder pressure sensor SW6 measures a change in pressure inside the combustion chamber 17.

The measurement signal of the in-cylinder pressure sensor SW6 is input to the θci deviation calculation unit 101k. The θci deviation calculation unit 101k estimates the CI combustion start timing θci based on the measurement signal of the in-cylinder pressure sensor SW6, and calculates the deviation between the estimated CI combustion start timing θci and the target θci. The θci deviation calculation unit 101k outputs the calculated θci deviation to the target in-cylinder state amount setting unit 101b. The target in-cylinder state amount setting unit 101b corrects the model based on the θci shift. The target in-cylinder state amount setting unit 101b sets the target in-cylinder state amount using the corrected model in the subsequent cycles.

The engine 1 is operated by the ECU 10 performing the SI rate adjustment in two stages, that is, the SI rate is roughly adjusted by adjusting the state quantity, and the ignition timing feedback control is performed using an index related to the combustion waveform. A target SPCCI combustion corresponding to the state can be accurately realized.

(Combustion noise suppression control)
Since SPCCI combustion is a combustion mode that combines SI combustion and CI combustion, knocking due to SI combustion and knocking due to CI combustion may occur. When knocking caused by SI combustion is SI knocking and knocking caused by CI combustion is CI knocking, SI knocking means that unburned gas outside the region where the air-fuel mixture burns SI in the combustion chamber 17 is abnormally localized. It is a phenomenon of rapid combustion due to self-ignition (local self-ignition that is clearly different from normal CI combustion), and CI knock is a main component (cylinder block/head of the engine 1 due to pressure fluctuation due to CI combustion). , Piston, crank journal, etc.) resonating phenomenon. SI knock appears as a large noise having a frequency of about 6.3 kHz due to air column vibration occurring in the combustion chamber 17 due to local self-ignition. On the other hand, the CI knock appears as a large noise having a frequency of about 1 to 4 kHz (more strictly, a plurality of frequencies included in the range) due to resonance of main components of the engine 1. Thus, SI knock and CI knock appear as noises of different frequencies due to different causes.

The ECU 10 controls SPCCI combustion so that both SI knocking and CI knocking do not occur. Specifically, the ECU 10 calculates the SI knock index associated with the SI knock and the CI knock index associated with the CI knock by Fourier transforming the detection signal of the in-cylinder pressure sensor SW6. The SI knock index is an in-cylinder pressure spectrum around 6.3 kHz which increases with the occurrence of SI knock, and the CI knock index is an in-cylinder pressure spectrum around 1 to 4 kHz which increases with the occurrence of CI knock. is there.

Then, the ECU 10 determines the θci limit such that each of the SI knock index and the CI knock index does not exceed the permissible limit according to a predetermined map, and also determines the θci limit determined from the operating state of the engine 1 and the θci limit. By comparison, if the θci limit is the same as θci or on the advance side, θci is set to the target θci, while if the θci limit is on the retard side from θci, the θci limit is set to the target θci. By this control, both SI knock and CI knock are suppressed.

That is, the ECU 10 performs the feedback control of the ignition timing by using the index related to the combustion waveform, and also determines the ignition timing by using the SI knock index and the CI knock index calculated based on the signal of the in-cylinder pressure sensor SW6. The engine 1 is being operated by adjusting. As a result, the engine 1 operates stably. Hereinafter, the SI knock index and the CI knock index will be collectively referred to as an index related to combustion noise.

(Cylinder pressure sensor failure diagnosis)
As described above, the engine 1 that performs SPCCI combustion uses the detection signal of the in-cylinder pressure sensor SW6 to perform ignition control and combustion noise suppression control. In the engine 1, the detection signal of the cylinder pressure sensor SW6 is important. If a wrong detection signal is output due to a failure of the in-cylinder pressure sensor SW6, the operation of the engine 1 may be hindered. Therefore, the engine system includes an abnormality diagnosis device 100 for the in-cylinder pressure sensor SW6.

FIG. 7 illustrates the configuration of the abnormality diagnosing device 100 for the in-cylinder pressure sensor SW6. The abnormality diagnosis device 100 includes a calculation unit 111, a driving unit 112, and a diagnosis unit 113. The calculation unit 111, the driving unit 112, and the diagnosis unit 113 are functional blocks configured in the ECU 10, respectively.

As described above, the calculation unit 111 calculates the index related to the combustion waveform and the index related to the combustion noise based on the signal from the in-cylinder pressure sensor SW6. The calculation unit 111 constantly calculates an index related to the combustion waveform and an index related to combustion noise, and outputs the index to the operation unit 112. The index related to the combustion waveform and the index related to the combustion noise are used for controlling the engine 1.

In FIG. 7, the operating unit 112 operates the engine 1 by outputting signals to the injector 6 and the spark plug 25. As described above, the operating unit 112 adjusts the ignition timing of the spark plug 25 using the index related to the combustion waveform and the index related to the combustion noise.

The control of the engine 1 executed by the driving unit 112 also includes fuel cut control of the engine 1. Specifically, the driving unit 112 stops the fuel supply to the engine 1 through the injector 6 when the deceleration fuel cut condition is satisfied while the vehicle is traveling. The driving unit 112 determines that the deceleration fuel cut condition is satisfied based on the detection signal of the accelerator opening sensor SW12. When the fuel supply is stopped, the engine 1 performs the fuel cut operation. The spark plug 25 also does not ignite during the fuel cut operation.

The diagnosis unit 113 diagnoses a failure of the in-cylinder pressure sensor SW6. The diagnosis unit 113 performs a failure diagnosis of the in-cylinder pressure sensor SW6 while the engine 1 is in the fuel cut operation. By doing so, the diagnosis unit 113 can diagnose the failure of the in-cylinder pressure sensor SW6 based on the pressure change in the combustion chamber 17 that is not affected by the combustion of the air-fuel mixture. Further, since the ignition plug 25 does not ignite while the engine 1 is in the fuel cut operation, there is an advantage that the detection signal of the in-cylinder pressure sensor SW6 is not affected by the noise of the ignition plug 25.

Here, an example of failure of the in-cylinder pressure sensor SW6 will be described. FIG. 8 shows an example of the detection signal output when the in-cylinder pressure sensor SW6 is normal and the detection signal output when the in-cylinder pressure sensor SW6 is out of order. The horizontal axis of FIG. 8 is the crank angle, and the vertical axis of FIG. 8 is the pressure in the combustion chamber 17. The vertical axis of FIG. 8 corresponds to the detection signal of the in-cylinder pressure sensor SW6.

When the engine 1 is in the fuel cut operation, combustion is not performed in the combustion chamber 17, so the pressure in the combustion chamber 17 changes as the volume of the combustion chamber 17 changes. The pressure in the combustion chamber 17 becomes maximum (Pmax) near the compression top dead center. If the in-cylinder pressure sensor SW6 is normal, the detection signal of the in-cylinder pressure sensor SW6 becomes maximum near the compression top dead center so as to correspond to the pressure change in the combustion chamber 17. The pressure in the combustion chamber 17 is also symmetrical or substantially symmetrical with the crank angle at which the maximum pressure Pmax is the center.

If the in-cylinder pressure sensor SW6 is normal, the detection signal of the in-cylinder pressure sensor SW6 is symmetrical or substantially symmetrical with the vicinity of the compression top dead center as the center so as to correspond to the pressure change in the combustion chamber 17. On the other hand, according to the study by the inventors of the present application, it was newly found that the value of the signal of the in-cylinder pressure sensor SW6 during the expansion stroke becomes small when the insulation failure occurs in the insulating portion 713. When the in-cylinder pressure sensor SW6 is out of order, the detection signal of the in-cylinder pressure sensor SW6 has a smaller signal value after the compression top dead center than the signal value before the compression top dead center.

Therefore, the diagnosis unit 113, based on the detection signal of the in-cylinder pressure sensor SW6, the value of the detection signal of the in-cylinder pressure sensor SW6 at the timing (−α° CA) advanced by a specific crank angle with respect to the compression top dead center ( That is, the signal value before the top) and the signal value of the in-cylinder pressure sensor SW6 (that is, the signal value after the top) at the timing (+α° CA) delayed by the same specific crank angle with respect to the compression top dead center. Calculate the difference. The specific crank angle may be set near 60° CA, for example. The diagnostic unit 113 diagnoses that the in-cylinder pressure sensor SW6 is out of order when an abnormal condition that the signal value difference is larger than a predetermined threshold is satisfied during the fuel cut operation of the engine 1. By doing so, the accuracy of failure diagnosis can be improved.

The diagnosis unit 113 may not perform the failure diagnosis of the in-cylinder pressure sensor SW6 until the set time elapses after the supply of the fuel to the engine 1 is stopped. Immediately after stopping the supply of fuel to the engine 1, the environment inside the combustion chamber 17 is not stable. For example, immediately after the supply of the fuel to the engine 1 is stopped, the EGR gas remaining in the EGR passage 52 enters the combustion chamber 17, so that the specific heat ratio of the gas in the combustion chamber 17 may not be constant. is there. Immediately after the supply of fuel to the engine 1 is stopped, the temperature of the wall surface of the combustion chamber 17 may fluctuate greatly. As a result, even if the in-cylinder pressure sensor SW6 has not failed, the output of the in-cylinder pressure sensor SW6 varies, and the accuracy of the failure diagnosis of the in-cylinder pressure sensor SW6 deteriorates.

Therefore, the diagnosis unit 113 may limit the determination of the failure of the in-cylinder pressure sensor SW6 from the time when the supply of the fuel to the engine 1 is stopped until the set time elapses. By doing so, the diagnosis unit 113 can accurately diagnose the failure of the in-cylinder pressure sensor SW6.

When the diagnosis unit 113 determines a failure of the in-cylinder pressure sensor SW6, it sends a failure flag to the operation unit 112. When receiving the failure flag, the operating unit 112 limits the control of the engine 1 using the index related to the combustion waveform and the index related to the combustion noise. The control of the engine 1 based on the signal of the in-cylinder pressure sensor SW6 that has failed is because the operation of the engine 1 may be hindered. After receiving the failure flag, the operating unit 112 uses the index related to the combustion waveform and the index related to the combustion noise unless a signal indicating that the failure of the in-cylinder pressure sensor SW6 is resolved is received. The control of the engine 1 that has been used is continuously limited.

The diagnosis unit 113 also gives a notification through the notification unit 57 when it determines that the in-cylinder pressure sensor SW6 has failed. The user is informed that the in-cylinder pressure sensor SW6 is out of order. When the user stores the vehicle in a repair shop or the like, the failure of the in-cylinder pressure sensor SW6 is resolved.

If the failure of the in-cylinder pressure sensor SW6 is resolved, the driving unit 112 receives a signal indicating that as the predetermined operation is performed. The operation unit 112 controls the engine 1 using the index related to the combustion waveform calculated by the calculation unit 111 and the index related to the combustion noise. In addition, the notification unit 57 stops the notification.

(Cylinder pressure sensor abnormality judgment)
The diagnosis unit 113 of the abnormality diagnosing device 100 performs the fuel diagnosis operation during the fuel cut operation as well as when the engine 1 is not in the fuel cut operation (that is, when combustion is performed in the combustion chamber 17). First, it is determined whether or not the in-cylinder pressure sensor SW6 outputs an abnormal value.

FIG. 9 shows an example of the detection signal that the in-cylinder pressure sensor SW6 outputs when it is normal and the detection signal that the in-cylinder pressure sensor SW6 outputs when it is abnormal. The horizontal axis of FIG. 9 is the crank angle, and the vertical axis of FIG. 9 is the pressure in the combustion chamber 17. The vertical axis in FIG. 9 also corresponds to the detection signal of the in-cylinder pressure sensor SW6.

According to the study by the inventors of the present application, it has been found that the in-cylinder pressure sensor SW6 may output an abnormal value, for example, at the time of rapid recovery from fuel cut. That is, when the driver suddenly depresses the accelerator pedal during fuel cut, a relatively large amount of fuel is supplied into the low temperature combustion chamber and combustion is started, as illustrated in FIG. In particular, the value of the signal of the in-cylinder pressure sensor SW6 during the expansion stroke may become lower than the actual pressure in the combustion chamber 17.

When a relatively large amount of fuel is supplied to the engine 1 during fuel cut, air column vibration (knocking) may occur in the combustion chamber 17 as combustion with a large amount of heat rapidly starts. According to a study by the inventors of the present application, it is considered that the in-cylinder pressure sensor SW6 outputs an abnormal value due to two causes caused by air column vibration.

The first reason why the in-cylinder pressure sensor SW6 outputs an abnormal value is that the diaphragm 71 and the piezoelectric element 75 vibrate due to the vibration of the air column in the combustion chamber 17, causing the electrode 77 of the piezoelectric element 75 and the compression spring 791 to move. That is, the contact state is deteriorated (see FIG. 4). When the contact state between the electrode 77 and the compression spring 791 is deteriorated, the charge is not smoothly supplied from the piezoelectric element 75 to the charge amplifier 710, and the charge supply amount to the charge amplifier 710 is reduced. As a result, the value of the signal from the in-cylinder pressure sensor SW6, particularly during the expansion stroke, becomes lower than the actual pressure in the combustion chamber 17.

The second cause of the in-cylinder pressure sensor SW6 outputting an abnormal value is that the diaphragm 71 and the piezoelectric element 75 vibrate due to the vibration of the air column in the combustion chamber 17, so that the pre-assignment to the piezoelectric element 75 is expected. The load is reduced. As schematically shown in FIG. 10, the position of the piezoelectric element 75 and the pedestal 76 are slightly deviated by the vibration of the air column in the combustion chamber 17, so that the clearance existing between the piezoelectric element 75 and the pedestal 76 is released. It is considered that the preload applied to the piezoelectric element 75 is reduced due to the elimination of the above. When the preload applied to the piezoelectric element 75 decreases, the deformation amount of the piezoelectric element 75 with respect to the bending amount of the diaphragm 71 becomes small. As a result, the value of the signal from the in-cylinder pressure sensor SW6 becomes lower than the actual pressure in the combustion chamber 17.

As shown in FIG. 9, the diagnosis unit 113 detects the in-cylinder pressure sensor SW6 based on the detection signal of the in-cylinder pressure sensor SW6 at a timing (−α° CA) advanced by a specific crank angle with respect to the compression top dead center. The value of the detection signal (that is, the signal value before the top) and the value of the signal of the in-cylinder pressure sensor SW6 at the timing (+α°CA) delayed by the same specific crank angle with respect to the compression top dead center (that is, after the top) Signal value), and when the abnormal condition that the calculated difference is larger than a predetermined threshold value is satisfied, it is determined that the in-cylinder pressure sensor SW6 outputs an abnormal value. This abnormal condition is the same as the abnormal condition used for diagnosing the failure of the in-cylinder pressure sensor SW6 described above. By using this abnormal condition, the diagnosis unit 113 can also accurately detect that the in-cylinder pressure sensor SW6 outputs an abnormal value.

Here, FIG. 11 shows the indicated mean effective pressure calculated based on the signal of the in-cylinder pressure sensor SW6 that outputs a normal value after the engine 1 returns from the fuel cut operation (F/C) at time t. An example is compared with an example of the indicated mean effective pressure calculated based on the signal of the in-cylinder pressure sensor SW6 that outputs an abnormal value. The horizontal axis of FIG. 11 is time, and the vertical axis is the indicated mean effective pressure. The target indicated mean effective pressure (target IMEP: Indicated Mean Effective Pressure) after returning from the fuel cut operation is the same in the two examples. As illustrated in FIG. 11, the indicated mean effective pressure calculated on the basis of the signal of the in-cylinder pressure sensor SW6 that outputs a normal value substantially matches the target indicated mean effective pressure. On the other hand, the indicated mean effective pressure calculated based on the signal of the in-cylinder pressure sensor SW6 that outputs an abnormal value is low because the signal value of the in-cylinder pressure sensor SW6 during the expansion stroke is low. The pressure value is temporarily greatly reduced. It is temporary that the in-cylinder pressure sensor SW6 outputs an abnormal value, and even if the in-cylinder pressure sensor SW6 outputs an abnormal value, it then outputs a normal value. The value of the indicated mean effective pressure is almost the same as the normal value.

While the in-cylinder pressure sensor SW6 temporarily outputs an abnormal value due to air column vibration, when the in-cylinder pressure sensor SW6 fails due to the above-described insulation failure, the in-cylinder pressure sensor SW6 is detected. Does not output a normal value.

Therefore, it is possible to determine that the in-cylinder pressure sensor SW6 is out of order and that the in-cylinder pressure sensor SW6 outputs an abnormal value, using the same abnormal condition, but if both are not distinguished. It doesn't happen.

Therefore, if the diagnosis unit 113 determines that the difference between the signal value before the top and the signal value after the top is larger than the threshold value during the fuel cut operation of the engine 1, the cylinder pressure sensor SW6 is out of order. To diagnose. If the diagnosis unit 113 determines that the difference between the front top signal value and the rear top signal value is larger than the threshold value when the engine 1 is not in the fuel cut operation, the in-cylinder pressure sensor SW6 detects an abnormal value. Judge that it is outputting. That is, if the abnormal condition is satisfied when the engine 1 is not in the fuel cut operation, the diagnosis unit 113 does not diagnose that the in-cylinder pressure sensor SW6 is out of order. As a result, the ECU 10 can prevent erroneous diagnosis of a failure of the in-cylinder pressure sensor SW6. Further, the ECU 10 can accurately determine that the in-cylinder pressure sensor SW6 outputs an abnormal value.

When the diagnosis unit 113 determines that the in-cylinder pressure sensor SW6 is temporarily outputting an abnormal value, the notification unit 57 does not notify. As a result, it is possible to suppress erroneous notification to the user.

When the engine 1 is controlled using the signal from the cylinder pressure sensor SW6 when the cylinder pressure sensor SW6 outputs an abnormal value, the cylinder pressure sensor SW6 may cause trouble in the operation of the engine 1. It is the same as when there is a failure. Therefore, the operation unit 112 partially restricts the operation of the engine 1 using the in-cylinder pressure sensor SW6.

Here, as illustrated in FIG. 9, even when the in-cylinder pressure sensor SW6 outputs an abnormal value due to air column vibration, the sensor signal near the compression top dead center and the compression top dead center The sensor signal before that is almost the same as the signal of the in-cylinder pressure sensor SW6 at the normal time. The index related to the combustion waveform (θci, the center of gravity of combustion, and the indicated mean effective pressure) and the index related to the combustion noise are calculated based on the signal from the in-cylinder pressure sensor SW6. Of the indexes related to the combustion waveform and the indexes related to the combustion noise, the indexes related to the combustion waveform are calculated by also using the signal value of the in-cylinder pressure sensor SW6 during the expansion stroke. Therefore, the index related to the combustion waveform calculated when the in-cylinder pressure sensor SW6 outputs an abnormal value has low reliability. On the other hand, the index related to combustion noise is less affected by the signal value of the in-cylinder pressure sensor SW6 during the expansion stroke. Therefore, the index related to the combustion noise calculated when the in-cylinder pressure sensor SW6 outputs an abnormal value can ensure high reliability.

When the diagnosis unit 113 determines that the in-cylinder pressure sensor SW6 outputs an abnormal value, the diagnosis unit 113 transmits the reliability flag to the operation unit 112.

When receiving the reliability flag, the operation unit 112 limits the control of the engine 1 using the index related to the combustion waveform having low reliability. Specifically, the operation unit 112 does not perform the feedback control related to the adjustment of the ignition timing using the index related to the combustion waveform. By restricting the control of the engine 1 using an index with low reliability, it is possible to prevent the operation of the engine 1 from being disturbed. On the other hand, the operating unit 112 controls the engine 1 using a highly reliable index related to combustion noise. The operating unit 112 can appropriately operate the engine 1 by controlling the engine 1 using a highly reliable index. Specifically, deterioration of the NVH performance of the engine 1 is suppressed.

When limiting the control of the engine 1 using the index related to the combustion waveform, the operation unit 112 may perform the feedback control of the ignition timing using the previous value of the index related to the combustion waveform, or may perform the feedback control. The feedforward control of the ignition timing may be performed by stopping the control.

The driving unit 112 also limits the control of the engine 1 using the index with low reliability only in the next cycle after receiving the reliability flag. As described above, the in-cylinder pressure sensor SW6 temporarily outputs an abnormal value, and the in-cylinder pressure sensor SW6 then outputs a normal value. When the diagnosis unit 113 does not transmit the reliability flag and the operation unit 112 does not receive the reliability flag, the operation unit 112 controls the engine 1 using the index related to the combustion waveform and the index related to the combustion noise. To resume. As a result, the engine 1 operates stably.

(Procedure for failure diagnosis and abnormality determination of in-cylinder pressure sensor)
FIG. 12 is a flowchart showing a procedure of failure diagnosis and abnormality determination of the in-cylinder pressure sensor SW6 executed by the abnormality diagnosis device 100. In step S1 after the start, the abnormality diagnosis device 100 reads the detection signals of the sensors SW1 to SW17. In the following step S2, the calculation unit 111 calculates an index related to the combustion waveform and an index related to combustion noise based on the signal from the in-cylinder pressure sensor SW6.

In step S3, the operation unit 112 determines whether the engine 1 is performing the deceleration fuel cut operation. If the engine 1 is not in the fuel cut operation, the process proceeds to step S4, and if the engine 1 is in the fuel cut operation, the process proceeds to step S12.

In step S4, the diagnosis unit 113 calculates the difference between the pre-top signal value and the post-top signal value, as described above. In subsequent step S5, diagnostic unit 113 determines whether or not the signal value difference calculated in step S4 exceeds a preset threshold value. If the signal value difference does not exceed the threshold value, the process proceeds to step S6. If the signal value difference exceeds the threshold, the process proceeds to step S9.

In step S6, diagnostic unit 113 determines that cylinder pressure sensor SW6 is not abnormal, and in subsequent step S7, diagnostic unit 113 sets the reliability flag to zero.

In step S8, since the reliability flag is zero (that is, there is reliability), the operating unit 112 controls the engine 1 using the index related to the combustion waveform and the index related to the combustion noise.

On the other hand, in step S9, the diagnosis unit 113 determines that the in-cylinder pressure sensor SW6 is temporarily abnormal, and in subsequent step S10, the diagnosis unit 113 sets the reliability flag to 1.

In step S11, the operating unit 112 temporarily limits the control of the engine 1 using the index related to the combustion waveform because the reliability flag is 1 (that is, there is no reliability). The operating unit 112 permits control of the engine 1 using an index related to combustion noise.

After that, if the determination in step S5 is NO, the driving unit 112 releases the restriction. The operating unit 112 controls the engine 1 using an index related to the combustion waveform and an index related to combustion noise.

In step S12 when the engine 1 is under fuel cut, the diagnosis unit 113 calculates the difference between the pre-top signal value and the post-top signal value, as in step S4. In subsequent step S13, diagnostic unit 113 determines whether the signal value difference calculated in step S12 exceeds a preset threshold value. If the signal value difference does not exceed the threshold value, the process proceeds to step S14. If the signal value difference exceeds the threshold value, the process proceeds to step S16.

In step S14, the diagnosis unit 113 determines that the in-cylinder pressure sensor SW6 is not in failure, and in subsequent step S15, the diagnosis unit 113 sets the failure flag to zero. The process then returns.

On the other hand, in step S16, the diagnosis unit 113 determines that the in-cylinder pressure sensor SW6 has a failure due to defective insulation, and in the subsequent step S17, the diagnosis unit 113 sets the failure flag to 1.

In step S18, the operating unit 112 restricts the control of the engine 1 using the in-cylinder pressure sensor SW6 because the failure flag is 1 (that is, the in-cylinder pressure sensor SW6 is in failure). Although the flow of FIG. 12 does not include steps, when the control of the engine 1 using the in-cylinder pressure sensor SW6 is restricted, as described above, when the failure is resolved, the operating unit 112 restricts the restriction. To release.

(Other embodiments)
The technique disclosed herein is not limited to being applied to the engine 1 having the above-described configuration. Various configurations can be adopted as the configuration of the engine 1.

1 engine 10 ECU (control unit)
17 Combustion chamber 100 Abnormality diagnosis device 111 Calculation unit 112 Driving unit 113 Diagnostic unit 57 Notification unit 75 Piezoelectric element SW6 Cylinder pressure sensor

Claims (6)

An in-cylinder pressure sensor that has a piezoelectric element to which a preload is applied and that outputs a signal corresponding to the pressure when the piezoelectric element is deformed by the pressure in the combustion chamber of an engine mounted on an automobile,
A signal is input from the in-cylinder pressure sensor, and at least a control unit that operates the engine using the signal from the in-cylinder pressure sensor is provided,
The control unit determines whether or not an abnormal condition related to the in-cylinder pressure sensor is satisfied, based on at least the signal of the in-cylinder pressure sensor on the retard side of the compression top dead center,
The control unit diagnoses that the in-cylinder pressure sensor has a failure when the abnormal condition is satisfied while the supply of fuel to the engine is stopped,
An abnormality diagnosis device for an in-cylinder pressure sensor, wherein the control section does not diagnose that the in-cylinder pressure sensor is in failure when the abnormal condition is satisfied while fuel is being supplied to the engine. The in-cylinder pressure sensor abnormality diagnosis device according to claim 1,
An abnormality diagnosis device for an in-cylinder pressure sensor that limits the operation of the engine using a signal from the in-cylinder pressure sensor when the abnormal condition is satisfied while fuel is being supplied to the engine. The in-cylinder pressure sensor abnormality diagnosis device according to claim 2,
If the abnormal condition is satisfied while fuel is being supplied to the engine, the control unit operates the engine using a signal from the in-cylinder pressure sensor. In-cylinder pressure sensor abnormality diagnosis device for temporarily restricting in. The abnormality diagnostic device for a cylinder pressure sensor according to any one of claims 1 to 3,
When the control unit diagnoses that the in-cylinder pressure sensor is out of order, the in-cylinder pressure sensor continuously limits the operation of the engine using the signal of the in-cylinder pressure sensor after the diagnosis. Abnormality diagnosis device. The abnormality diagnosis device for a cylinder pressure sensor according to any one of claims 1 to 4,
The in-cylinder pressure sensor abnormality diagnosing device, wherein the control section gives a notification through an informing section when the in-cylinder pressure sensor is diagnosed as having a failure. The abnormality diagnostic device for a cylinder pressure sensor according to any one of claims 1 to 5,
The abnormal condition includes the value of the signal of the in-cylinder pressure sensor at the timing advanced by a specific crank angle with respect to the compression top dead center and the value at the timing delayed by the specific crank angle with respect to the compression top dead center. An in-cylinder pressure sensor abnormality diagnosing device, wherein a difference from a signal value of the in-cylinder pressure sensor is larger than a predetermined threshold value.

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