JP6020061B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle such as an automobile, and more particularly to a control device for an internal combustion engine provided with an in-cylinder pressure sensor.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 11-22541), an internal combustion engine having a function of diagnosing the adhesion state of deposits in a combustion chamber in a system equipped with a direct injection engine A control device is known. In the prior art, the fuel injection timing is forcibly changed to the advance side, and the combustion speed when this change is made and the combustion speed (standard combustion speed) when no deposit is attached to the combustion chamber By comparing, the adhesion state of the deposit is detected.

JP-A-11-22541 Japanese Patent Laid-Open No. 07-139417 JP 08-218933 A JP-A-08-246941

  In the above-described prior art, the deposit adhesion state is detected based on the combustion speed when the fuel injection timing is forcibly changed to the advance side. However, in this case, since the fuel injection timing is forcibly shifted from the timing suitable for the driving state, there is a problem that fuel consumption and drivability are deteriorated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately detect the deposit state without forcibly changing the control parameters of the internal combustion engine. It is an object of the present invention to provide a control device for an internal combustion engine capable of achieving the above.

A first invention is a cylinder pressure sensor that detects a pressure in a cylinder and outputs a signal corresponding to the detection result;
An output drift amount calculating means for calculating a drift amount of an output of the in-cylinder pressure sensor based on the output when a transient operation including a start of a fuel cut or a return from a fuel cut is performed;
A maximum drift amount calculating means for calculating a maximum value of the drift amount in one cycle as a maximum drift amount;
A reference drift amount storage means in which a reference drift amount corresponding to the value of the maximum drift amount obtained when no deposit is attached in the cylinder is stored for each operating condition;
Reference drift amount calculating means for calculating the reference drift amount from the reference drift amount storage means based on the same operating conditions as when the maximum drift amount was obtained;
Drift determining means for determining that deposits are attached in the cylinder when the difference between the maximum drift amount and the reference drift amount is larger than a predetermined determination value;
It is characterized by providing.

A second invention subtracts a component corresponding to a drift correction time constant of a signal output circuit provided in the in-cylinder pressure sensor from the drift amount, and corresponds to a thermal time constant of the in-cylinder pressure sensor in the drift amount. A thermal time constant calculating means for calculating a component;
The maximum drift amount calculating means acquires a maximum value of a component corresponding to the thermal time constant as the maximum drift amount.

According to a third aspect of the present invention, there is provided a drift time constant calculating means for calculating a time constant corresponding to a time required when the drift amount returns from the state at the transient operation toward the state at the steady operation.
A reference time constant storage means in which a reference time constant corresponding to the value of the time constant obtained when no deposit is deposited in the cylinder is stored for each operating condition;
A reference time constant calculating means for calculating the reference time constant from the reference time constant storage means based on the same operating conditions as when the time constant was obtained;
The drift determination means includes
The difference between the maximum drift amount and the reference drift amount is larger than a first determination value set in advance, and the difference between the time constant and the reference time constant is set from a second determination value set in advance. A first determination means for determining that deposits are attached in the cylinder,
When the difference between the maximum drift amount and the reference drift amount is larger than the first determination value and the difference between the time constant and the reference time constant is equal to or less than the second determination value, Second determining means for determining that the in-cylinder pressure sensor is faulty.

4th invention, the deposit removal means which performs control for removing a deposit, when it is judged with the drift judgment means that the deposit has adhered in the cylinder,
A failure determination unit that determines a failure of the in-cylinder pressure sensor based on a difference between the maximum drift amount before the deposit removal unit is activated and the maximum drift amount after the deposit removal unit is activated. .

  According to the first aspect of the present invention, the deposit amount in the cylinder is detected using the drift generated in the output of the in-cylinder pressure sensor without forcibly changing the control parameters such as the fuel injection timing and the ignition timing. Can do. As a result, it is possible to satisfactorily maintain the drivability and fuel consumption of the internal combustion engine while executing appropriate response control according to the deposit adhesion state. Further, since the deposit adhesion state is determined based on the difference between the maximum drift amount and the reference drift amount, errors due to variations in operating conditions and the like can be corrected, and the determination accuracy can be improved.

  According to the second invention, since the maximum drift amount is calculated based only on the component corresponding to the thermal time constant of the sensor in the output drift amount, it is necessary for the processing for calculating the maximum drift amount as compared with the first invention. Can be reduced. That is, since the component corresponding to the thermal time constant of the sensor is held at the maximum value over a long period, the maximum drift amount can be accurately calculated even if the calculation cycle of the output drift amount is lengthened.

  According to the third invention, the first and second determination means individually determine deposit adhesion and sensor failure based on the maximum drift amount of the in-cylinder pressure sensor and the time constant of the output drift. can do. Therefore, each determination result can be appropriately dealt with, and the reliability and maintainability of the system can be improved.

  According to the fourth invention, it is possible to detect whether or not the maximum drift amount has decreased due to the deposit peeling control and the effect of the deposit cleaner. If the reduction amount of the maximum drift amount is not normal, it is determined that the output drift has occurred due to a cause other than the deposit, and the in-cylinder pressure sensor can be determined to be faulty. Thereby, deposit adhesion determination and sensor failure determination can be performed individually, and reliability can be improved.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a characteristic diagram which shows an example of the drift which arises in the output of a cylinder pressure sensor when an engine load changes suddenly. It is a characteristic diagram which shows the time change of the output drift amount produced at the time of transient operation. It is a characteristic diagram which shows typically the state where maximum drift amount (DELTA) P1 changes according to the driving | running conditions of an engine. It is a characteristic diagram which illustrated the relationship between the adhesion amount of a deposit, and the drift amount reduction rate. In Embodiment 1 of this invention, it is a flowchart which shows an example of the control performed by ECU. In Embodiment 2 of this invention, it is a characteristic diagram which shows the time change of the output drift amount which arises at the time of transient operation according to a component. It is a characteristic diagram which shows the time change of the component corresponding to the thermal time constant of a sensor among the output drift amount of a cylinder pressure sensor, and the said output drift amount. In Embodiment 2 of this invention, it is a flowchart which shows an example of the control performed by ECU. In Embodiment 3 of this invention, it is a characteristic diagram which shows the time change of the output drift amount which arises at the time of transient operation, and its time constant. It is a characteristic diagram which shows the change of the output drift amount produced by the adhesion of a deposit and the failure of a sensor. It is a characteristic diagram which shows typically the state from which the time constant of output drift changes according to the driving | running condition of an engine. It is a characteristic diagram which illustrated the relationship between the adhesion amount of deposit and the delay of time constant. In Embodiment 3 of this invention, it is a flowchart which shows an example of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes an engine 10 as, for example, a multi-cylinder internal combustion engine. FIG. 1 shows one cylinder of a plurality of functions mounted on the engine 10. The present invention is applied to an internal combustion engine having an arbitrary number of cylinders including a single cylinder. In each cylinder of the engine 10, a combustion chamber 14 is formed by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine.

  The engine 10 also includes an intake passage 18 that sucks intake air into each cylinder, and an exhaust passage 20 through which exhaust gas is discharged from each cylinder. The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the amount of intake air. A catalyst 24 for purifying exhaust gas is provided in the exhaust passage 20. In each cylinder, a fuel injection valve 26 for injecting fuel into the combustion chamber 14 (in the cylinder), an ignition plug 28 for igniting an air-fuel mixture in the cylinder, and an intake passage 18 are opened and closed with respect to the cylinder. An intake valve 30 and an exhaust valve 32 for opening and closing the exhaust passage 20 with respect to the inside of the cylinder are provided. The present invention is not limited to a direct injection engine that injects fuel into a cylinder, and may be applied to an internal combustion engine that injects fuel into an intake passage 18 (intake port).

  Next, a system control system will be described. The system of the present embodiment includes a sensor system including sensors 40 to 44 and an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. First, the sensor system will be described. The crank angle sensor 40 outputs a signal (crank signal) synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount of the engine. The in-cylinder pressure sensor 44 individually detects the in-cylinder pressure of each cylinder, and is configured by a general pressure sensor or the like. The in-cylinder pressure sensor 44 includes a detection element such as a piezoelectric element that generates a voltage signal corresponding to the pressure in the cylinder, and a signal output circuit (not shown) that outputs the voltage signal to the ECU 50. In addition to the above sensors, the sensor system includes various sensors necessary for engine and vehicle control (for example, a water temperature sensor that detects the temperature of engine cooling water, an air-fuel ratio sensor that detects an exhaust air-fuel ratio, a driver) For example, an accelerator sensor for detecting the amount of accelerator operation.

  The ECU 50 is configured by an arithmetic processing device including a storage circuit such as a ROM and a RAM and an input / output port. Each sensor is connected to the input side of the ECU 50, and various actuators including the throttle valve 22, the fuel injection valve 26, the spark plug 28, and the like are connected to the output side of the ECU 50. Further, the ECU 50 has a function of acquiring the output of the in-cylinder pressure sensor 44, an output drift amount, and the like, and storing the acquired data in the storage circuit as time series data for at least one cycle.

  Then, the ECU 50 controls the operation of the engine by driving each actuator based on the engine operation information detected by the sensor system. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of the crank angle sensor 40, and the load is determined based on the intake air amount detected by the airflow sensor 42 and the engine speed. calculate. Further, the fuel injection amount is calculated based on the engine speed, the load, etc., and the fuel injection timing and the ignition timing are determined based on the crank angle. In each cylinder, the fuel injection valve 26 is driven when the fuel injection timing comes, and the spark plug 28 is driven when the ignition timing comes. Thereby, the air-fuel mixture is combusted in each cylinder, and the engine 10 is operated. Further, the ECU 50 has a function of executing a fuel cut that stops fuel injection when the engine is decelerated and the like, and returning from the fuel cut when the engine shifts from a deceleration state to an acceleration operation.

[Features of Embodiment 1]
There is a tendency for deposits generated by combustion to adhere to the wall surface of the combustion chamber 14, and particularly in a direct injection type engine, deposits become noticeable. For this reason, in the prior art engine control, there is known one that detects the adhesion state of the deposit based on the combustion speed when the fuel injection timing is forcibly changed to the advance side. However, if the fuel injection timing is changed, the fuel consumption and drivability are likely to deteriorate. Therefore, it is preferable to detect the deposit state without implementing such a change. For this reason, in the present embodiment, the adhesion state of the deposit is determined based on the amount of drift generated in the output of the in-cylinder pressure sensor 44. Hereinafter, this deposit adhesion determination control will be described.

(Deposit adhesion judgment control)
FIG. 2 is a characteristic diagram showing an example of a drift that occurs in the output of the in-cylinder pressure sensor when the engine load suddenly changes. As an operation state in which the load changes suddenly, for example, a transient operation including a start of a fuel cut, a return from a fuel cut, and the like can be given. At the time of transient operation, the amount of heat (amount of heat input) input from the cylinder to the in-cylinder pressure sensor 44 changes abruptly, so that the sensor thermally expands. As a result, as shown in FIG. 2, the in-cylinder pressure sensor 44 has a drift in which the output deviates from that during steady operation. In the following description, the amount of drift occurring in the output of the in-cylinder pressure sensor 44 is expressed as “output drift amount”, and the maximum value of the output drift amount in one cycle is expressed as “maximum drift amount”.

  FIG. 3 is a characteristic diagram showing temporal changes in the amount of output drift that occurs during transient operation. As shown in this figure, the output drift amount during the transient operation reaches the maximum drift amount ΔP1 at a certain point in time, and then gradually decreases. The maximum drift amount ΔP1 correlates with the amount of deposit deposited on the tip of the in-cylinder pressure sensor 44 (that is, in the cylinder). Therefore, in the deposit adhesion determination control, when a transient operation is executed, first, the output drift amount is calculated based on the output of the in-cylinder pressure sensor 44 and the engine operating conditions (for example, engine speed, load, etc.). Further, the maximum drift amount ΔP1 in one cycle is calculated. It should be noted that the output of the in-cylinder pressure sensor 44 during steady operation where no drift occurs can be set or measured in advance for each operating condition. For this reason, the output drift amount is calculated based on, for example, the output of the in-cylinder pressure sensor, engine operating conditions, prestored data during steady operation, and the like. Further, the maximum drift amount ΔP1 can be calculated, for example, by obtaining a peak value in the time series data storing the output drift amount for one cycle.

  FIG. 4 is a characteristic diagram schematically showing a state in which the maximum drift amount ΔP1 changes according to the engine operating conditions. The maximum drift amount ΔP1 varies depending not only on the deposit amount but also on the operating conditions. For this reason, as shown in FIG. 4, a reference drift amount map, which is a data map for calculating the reference drift amount ΔPα, is stored in advance in the storage circuit of the ECU 50 as shown in FIG. The reference drift amount ΔPα corresponds to the value of the maximum drift amount obtained when there is no deposit in the cylinder, and the reference drift amount map is set for each operating condition in the reference drift amount map. ing.

  The ECU 50 refers to the standard drift amount map using, for example, the same operating conditions (for example, engine speed, load, etc.) as those obtained when the maximum drift amount ΔP1 is obtained, so that the standard drift amount ΔPα is obtained from the map. calculate. Then, as shown in FIG. 4, by subtracting the maximum drift amount ΔP1 from the reference drift amount ΔPα, a drift amount reduction rate (ΔPα−ΔP1) that is the difference between the two is calculated. The drift amount reduction rate (ΔPα−ΔP1) calculated in this way is a parameter in which an error of the maximum drift amount ΔP1 due to variations in operating conditions or the like is corrected and the deposit amount in the cylinder is reflected.

  FIG. 5 is a characteristic diagram illustrating the relationship between the deposit amount and the drift amount reduction rate. As shown in this figure, the drift amount reduction rate (ΔPα−ΔP1) has a correlation with the deposit adhesion amount, and tends to increase as the deposit adhesion amount increases. Therefore, the ECU 50 determines whether or not the drift amount reduction rate (ΔPα−ΔP1) is greater than a preset first determination value, as shown in the following equation (1). The first determination value is set, for example, as a value corresponding to the allowable limit of the deposit adhesion amount.

ΔPα−ΔP1> first determination value (1)

  When the above equation (1) is established, the ECU 50 determines that the deposit is attached in the cylinder, and calculates the deposit amount based on the calculated value of the drift amount reduction rate (ΔPα−ΔP1). Then, it is recommended to perform deposit peeling control for peeling the deposit from the cylinder or use a deposit cleaner. As deposit peeling control, for example, knocking is intentionally generated and the peeling of the deposit is accelerated by the impact.

(Failure judgment control)
In addition, after performing deposit peeling control, it is good also as a structure which performs failure determination control of the cylinder pressure sensor 44 as follows. In this failure determination control, first, the maximum drift amount ΔP1 ′ is newly calculated after the deposit peeling control is completed. Then, as shown in the following equation (2), a difference (ΔP−ΔP1 ′) between the newly calculated maximum drift amount ΔP1 ′ and the maximum drift amount ΔP calculated before execution of the deposit peeling control is set in advance. It is determined whether it is larger than the auxiliary determination value. This auxiliary determination value is set corresponding to the minimum value of the decrease amount when the deposit adhesion amount decreases due to the effect of deposit peeling control, for example.

ΔP−ΔP1 ′> auxiliary judgment value (2)

  When the above equation (2) is established, it is determined that the deposit adhesion amount has decreased due to the effect of deposit peeling control, and therefore it is determined that the in-cylinder pressure sensor 44 is normal. On the other hand, when the above equation (2) is not established, the deposit adhesion amount is not reduced even by the execution of deposit peeling control or the use of a deposit cleaner. As described above, when the adhesion state of the deposit is not improved, it is determined that the output drift is caused by the failure of the sensor, not the adhesion of the deposit, and the in-cylinder pressure sensor 44 is determined as the failure.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 6 is a flowchart showing an example of control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is executed during the aforementioned transient operation. In the routine shown in FIG. 6, first, in step 100, the output drift amount is calculated based on the output of the in-cylinder pressure sensor 44, and the maximum drift amount ΔP1 is calculated based on the calculation result.

  Next, in step 102, a reference drift amount ΔPα is calculated based on the same operating conditions as when the maximum drift amount ΔP1 was obtained by referring to a map for each operating condition (reference drift amount map). In step 104, it is determined whether or not the drift amount reduction rate (ΔPα−ΔP1) is larger than the first determination value according to the equation (1). If this determination is not established, it is determined that no deposit has adhered to the cylinder, and thus the control of this routine is terminated.

  On the other hand, if the determination in step 104 is established, it is determined in step 106 that a deposit exceeding the allowable limit is attached to the cylinder (temporary determination). Here, the provisional determination means that the determination result includes an increase in the output drift amount due to the failure of the in-cylinder pressure sensor 44. Next, in step 108, the deposit adhesion amount is calculated (estimated) based on the calculated value of the drift amount reduction rate (ΔPα−ΔP1). In step 110, the above-described deposit peeling control, the use of a deposit cleaner, etc. are recommended. Execute.

  Next, in step 112, the same processing as in step 100 is executed again to newly calculate the maximum drift amount ΔP1 ′. In step 114, the change amount of the maximum drift amount ΔP1 due to the execution of the deposit peeling control is calculated as a difference (ΔP1−ΔP1 ′), and it is determined whether or not this difference satisfies the equation (2). If this determination is established, it is determined that the deposit in the cylinder has been removed by execution of deposit peeling control, use of a deposit cleaner, or the like, and this routine is terminated. On the other hand, if the determination in step 114 is not established, the amount of deposit adhesion does not decrease, so the routine proceeds to step 116 where the in-cylinder pressure sensor 44 is determined to be faulty.

  As described in detail above, according to the present embodiment, the drift generated in the output of the in-cylinder pressure sensor 44 can be utilized without changing the control parameters such as the fuel injection timing and the ignition timing forcibly. The amount of deposit can be detected. Accordingly, it is possible to satisfactorily maintain the drivability and fuel consumption of the engine while performing appropriate response control according to the deposit adhesion state. Further, since the deposit adhesion state is determined based on the drift amount reduction rate (ΔPα−ΔP1), errors caused by variations in operating conditions between the maximum drift amount P1 and the reference drift amount ΔPα are corrected (offset). In addition, the determination accuracy can be increased. For example, if the data shown in FIG. 5 is used, the deposit adhesion amount can be accurately calculated based on the drift amount reduction rate (ΔPα−ΔP1), and the strength and execution period of deposit peeling control and the like can be optimized. Can protect the engine.

  Further, according to the failure determination control, it is possible to detect whether or not the maximum drift amount ΔP1 has decreased due to the deposit peeling control or the effect of the deposit cleaner. When the decrease amount of the maximum drift amount ΔP1 is not normal, it is determined that output drift has occurred due to a cause other than deposit, and the in-cylinder pressure sensor 44 can be determined to be faulty. Thereby, deposit adhesion determination and sensor failure determination can be performed individually, and reliability can be improved.

  In the first embodiment, step 100 in FIG. 6 shows a specific example of the output drift amount calculating means and the maximum drift amount calculating means in claim 1. Step 102 shows a specific example of the reference drift amount calculation means, and step 104 shows a specific example of the drift determination means. Step 110 shows a specific example of the deposit removing means in claim 4, and steps 112 to 116 show a specific example of the failure determining means. On the other hand, the storage circuit of the ECU 50 constitutes a specific example of the reference drift amount storage means in claim 1.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, in the same configuration as in the first embodiment (FIG. 1), the maximum drift amount is calculated based only on the component corresponding to the thermal time constant of the sensor in the output drift amount of the in-cylinder pressure sensor. It is characterized by. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
FIG. 7 is a characteristic diagram showing temporal changes in the amount of output drift that occur during transient operation according to components in Embodiment 2 of the present invention. FIG. 8 is a characteristic diagram showing temporal changes in the output drift amount of the in-cylinder pressure sensor and the component of the output drift amount corresponding to the thermal time constant of the sensor. As shown in FIG. 7, the output drift waveform is a combination of the waveform of component A corresponding to the thermal time constant of the in-cylinder pressure sensor and the waveform of component B corresponding to the drift correction time constant of the signal output circuit. It becomes.

  Here, the two components A and B change individually according to the input to the in-cylinder pressure sensor 44 (sensor temperature). The component A corresponding to the thermal time constant of the sensor gradually increases in the negative direction after the transient operation is started, for example, and becomes constant when the maximum value corresponding to the input is reached. On the other hand, the component B corresponding to the drift correction time constant of the signal output circuit gradually increases in the positive direction as opposed to the component A. Therefore, when the waveforms of the components A and B are synthesized, the maximum value (maximum drift amount) appears in the output drift amount as shown in FIG. Matches the value.

  For this reason, in the present embodiment, after calculating the output drift amount by the same method as in the first embodiment, by subtracting the component B corresponding to the drift correction time constant of the signal output circuit from the output drift amount, A component A corresponding to the thermal time constant of the sensor is calculated. Then, the maximum value of the component A is acquired as the maximum drift amount ΔP2. The value of component B is determined based on the design specifications of the signal output circuit and is stored in the ECU 50 in advance. The maximum drift amount ΔP2 obtained in this way is substantially the same value as the maximum drift amount ΔP1 calculated in the first embodiment, as shown in FIG. In the present embodiment, the reference drift amount ΔPα2 and the drift amount reduction rate (ΔPα2-ΔP2) are calculated by the same method as in the first embodiment, and the adhesion state of the deposit is determined based on the calculation result.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 9 is a flowchart showing an example of control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is executed during the aforementioned transient operation. In the routine shown in FIG. 9, first, at step 200, the output drift amount is calculated by the same method as in the first embodiment. Subsequently, a component B corresponding to the drift correction time constant of the signal output circuit is calculated based on data stored in the ECU 50 and the like. Then, the component A corresponding to the thermal time constant of the sensor is calculated by subtracting the component B from the output drift amount. Next, in step 202, the maximum value of component A is acquired as the maximum drift amount ΔP2. That is, the maximum drift amount ΔP2 is calculated based on only the component A.

  Next, in step 204, as in the first embodiment, referring to a map for each operating condition (reference drift amount map), a reference is made based on the same operating condition as when the maximum drift amount ΔP2 was obtained. A drift amount ΔPα is calculated. In step 206, it is determined whether or not the drift amount reduction rate (ΔPα2-ΔP2) is larger than the first determination value. In steps 208 to 218, processing similar to that in steps 106 to 116 in the first embodiment (FIG. 6) is executed. In this case, in steps 214 to 218, the change amount of the maximum drift amount ΔP2 due to the execution of the deposit peeling control is calculated as a difference (ΔP2−ΔP2 ′), and it is determined whether or not this difference is larger than the auxiliary determination value. Thus, failure determination control is executed.

  In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment. In particular, in the present embodiment, since the maximum drift amount ΔP2 is calculated based only on the component A corresponding to the thermal time constant of the sensor among the output drift amounts, the maximum drift amount ΔP2 is compared with the first embodiment. The calculation load required for the calculation process can be reduced. That is, in the calculation process exemplified in the first embodiment, it is necessary to detect the maximum value while calculating the output drift amount in a relatively short calculation cycle. On the other hand, the component A corresponding to the thermal time constant of the sensor is held at the maximum value over a long period as shown in FIG. Therefore, in the present embodiment, the maximum drift amount ΔP2 can be accurately calculated even if the calculation cycle of the output drift amount is lengthened.

  In the second embodiment, step 200 in FIG. 9 shows a specific example of the output drift amount calculating means in claim 1 and the thermal time constant calculating means in claim 2, and step 202 is claimed in claim 2. The specific example of the maximum drift amount calculation means in FIG. Step 204 shows a specific example of the reference drift amount calculation means, and Step 206 shows a specific example of the drift determination means. Step 212 shows a specific example of the deposit removing means in claim 4, and Steps 214 to 218 show a specific example of the failure determining means.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. In the present embodiment, in addition to the control of the first or second embodiment, deposit adhesion and sensor failure are discriminated based on the time constant of the output drift waveform. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
FIG. 10 is a characteristic diagram showing a temporal change in the amount of output drift that occurs during transient operation and its time constant in Embodiment 3 of the present invention. FIG. 11 is a characteristic diagram showing changes in the amount of output drift caused by deposit adhesion and sensor failure. In FIG. 10, the time constant τ1 corresponds to the time required for the output drift amount to return from the transient operation state to the steady operation state. For example, the output drift amount becomes the maximum drift amount. It is defined as the time required to decrease to a certain percentage.

  As shown in FIG. 11, the absolute amount of output drift has a characteristic of decreasing when deposits are attached and when a sensor fails. That is, the formulas (1) and (2) used for deposit adhesion determination in the first and second embodiments are established not only when deposits are deposited but also when sensor sensitivity is reduced due to a failure of the in-cylinder pressure sensor 44. there's a possibility that. On the other hand, the time constant of the waveform of the output drift has a characteristic that it becomes longer as the deposit amount increases. For this reason, in the present embodiment, when the expression (1) or (2) is established, the determination process is further performed based on the time constant τ1, thereby discriminating between deposit adhesion and sensor failure. To do. In the following description, the case where the present embodiment is applied to the first embodiment, that is, the case where the time constant τ1 is used when the expression (1) is established will be described as an example.

  First, the ECU 50 calculates the time constant τ1 of the output drift waveform based on the time series data storing the output drift amount for one cycle. Here, FIG. 12 is a characteristic diagram schematically showing a state in which the time constant of the output drift changes according to the engine operating conditions (for example, engine speed, load, etc.). The time constant τ1 varies depending not only on the deposit amount but also on the operating conditions. Therefore, as shown in FIG. 12, a reference time constant map, which is a data map for calculating the reference time constant τα, is stored in advance in the storage circuit of the ECU 50 as shown in FIG. The reference time constant τα is equivalent to the value of the reference time constant obtained when there is no deposit in the cylinder, and the reference time constant τα is set for each operating condition in the reference time constant map. ing.

  The ECU 50 calculates the reference time constant τα from the map by referring to the reference time constant map using, for example, the same operating conditions (for example, engine speed, load, etc.) as when the time constant τ1 was obtained as a reference parameter. To do. Then, as shown in FIG. 12, by subtracting the time constant τ1 from the reference time constant τα, a time constant delay (τα−τ1) which is the difference between the two is calculated. The time constant delay (τα−τ1) calculated in this way is a parameter in which an error in the time constant τ1 due to variations in operating conditions and the like is corrected and the deposit amount in the cylinder is reflected.

  FIG. 13 is a characteristic diagram illustrating the relationship between the deposit amount and the time constant delay. As shown in this figure, the delay of time constant (τα−τ1) has a correlation with the deposit amount, and tends to increase as the deposit amount increases. Therefore, the ECU 50 executes the determination shown in the following equation (3) when the equation (1) is established, and the delay of the time constant (τα−τ1) is larger than the preset second determination value. It is determined whether or not. The second determination value is set, for example, as a value corresponding to the allowable limit of the deposit adhesion amount.

τα−τ1> second determination value (3)

  Then, the ECU 50 determines that an amount of deposit exceeding the allowable limit is attached to the cylinder when both of the formulas (1) and (3) are established. In addition, when the formula (1) is established but the formula (3) is not established, the sensitivity of the in-cylinder pressure sensor 44 has decreased beyond the allowable limit, and it is determined that the sensor has failed. To do. When the present embodiment is applied to the second embodiment, the equation (2) may be used instead of the equation (1).

[Specific Processing for Realizing Embodiment 3]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 14 is a flowchart showing an example of control executed by the ECU in the third embodiment of the present invention. The routine shown in this figure is executed during the transient operation described above. In addition, this routine exemplifies the case where the present embodiment is applied to the second embodiment (FIG. 9). In the routine shown in FIG. 14, first, in steps 300 to 306, processing similar to that in steps 200 to 206 in FIG. 9 is executed. Then, if the determination in step 306 is established, the process proceeds to step 308, in which the amount of deposit exceeding the allowable limit is adhered in the cylinder, or the sensor sensitivity is lowered due to the breakdown of the in-cylinder pressure sensor 44. It is determined that

  Next, in step 310, a time constant τ1 is calculated based on the output drift waveform. Further, the reference time constant τα is calculated by the method described above. In step 312, it is determined whether or not the time constant delay (τα−τ1) is larger than the second determination value as shown in the equation (3). If the determination in step 312 is established, the process proceeds to step 314, where it is determined that an amount of deposit exceeding the allowable limit is attached to the cylinder. In step 316, the deposit amount is calculated (estimated) based on the calculated value of the time constant delay (τα−τ1). In step 318, the above-described deposit peeling control, the use of a deposit cleaner, and the like are performed. Run. On the other hand, if the determination in step 312 is not satisfied, the routine proceeds to step 320, where the in-cylinder pressure sensor 44 is determined to be faulty.

  In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first and second embodiments. In the present embodiment, deposit adhesion and sensor failure are individually determined based on the maximum drift amount ΔP1 (or ΔP2) of the in-cylinder pressure sensor 44 and the time constant τ1 of the output drift. Can do. Therefore, each determination result can be appropriately dealt with, and the reliability and maintainability of the system can be improved. For example, if the data shown in FIG. 13 is used, the amount of deposit can be accurately calculated based on the time constant delay (τα−τ1). Thereby, the strength and execution period of deposit peeling control and the like can be optimized, and the engine can be protected.

  In the third embodiment, step 300 in FIG. 14 shows a specific example of the output drift amount calculating means in claim 1 and the thermal time constant calculating means in claim 2, and step 302 is claimed in claim 2. The specific example of the maximum drift amount calculation means in FIG. Step 304 shows a specific example of the reference drift amount calculation means, and Step 306 shows a specific example of the drift determination means. Step 310 shows a specific example of the drift time constant calculating means and the reference time constant calculating means in claim 3, steps 306, 312, and 314 show specific examples of the first determining means, and steps 306, 312. 320 indicate specific examples of the second determination means. On the other hand, the storage circuit of the ECU 50 constitutes a specific example of the reference time constant storage means in claim 3.

  In the present invention, also in the third embodiment, based on the difference (ΔP2−ΔP2 ′) between the maximum drift amount ΔP2 before the operation of the deposit removing means and the maximum drift amount ΔP2 ′ after the operation of the deposit removing means. A configuration may be adopted in which failure of the in-cylinder pressure sensor 44 is determined. Specifically, the same processing as in steps 214, 216, and 218 shown in FIG. 9 may be added after step 318 shown in FIG.

  In the above embodiment, the direct injection type engine 10 that injects fuel into the cylinder has been described as an example. However, the present invention is not limited to this, and the port injection type internal combustion engine that injects fuel into the intake port. It may be applied to institutions.

10 Engine (Internal combustion engine)
12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Catalyst 26 Fuel injection valve 28 Spark plug 30 Intake valve 32 Exhaust valve 40 Crank angle sensor 42 Air flow sensor 44 In-cylinder pressure sensor 50 ECU

Claims (4)

An in-cylinder pressure sensor that detects a pressure in the cylinder and outputs a signal corresponding to the detection result;
An output drift amount calculating means for calculating a drift amount of an output of the in-cylinder pressure sensor based on the output when a transient operation including a start of a fuel cut or a return from a fuel cut is performed;
A maximum drift amount calculating means for calculating a maximum value of the drift amount in one cycle as a maximum drift amount;
A reference drift amount storage means in which a reference drift amount corresponding to the value of the maximum drift amount obtained when no deposit is attached in the cylinder is stored for each operating condition;
Reference drift amount calculating means for calculating the reference drift amount from the reference drift amount storage means based on the same operating conditions as when the maximum drift amount was obtained;
Drift determining means for determining that deposits are attached in the cylinder when the difference between the maximum drift amount and the reference drift amount is larger than a predetermined determination value;
A control device for an internal combustion engine, comprising: The component corresponding to the drift correction time constant of the signal output circuit provided in the in-cylinder pressure sensor is subtracted from the drift amount, and the component corresponding to the thermal time constant of the in-cylinder pressure sensor is calculated from the drift amount. A constant calculation means,
2. The control device for an internal combustion engine according to claim 1, wherein the maximum drift amount calculating means acquires a maximum value of a component corresponding to the thermal time constant as the maximum drift amount. Drift time constant calculating means for calculating a time constant corresponding to a time required when the drift amount returns from the state at the time of transient operation toward the state at the time of steady operation;
A reference time constant storage means in which a reference time constant corresponding to the value of the time constant obtained when no deposit is deposited in the cylinder is stored for each operating condition;
A reference time constant calculating means for calculating the reference time constant from the reference time constant storage means based on the same operating conditions as when the time constant was obtained;
The drift determination means includes
The difference between the maximum drift amount and the reference drift amount is larger than a first determination value set in advance, and the difference between the time constant and the reference time constant is set from a second determination value set in advance. A first determination means for determining that deposits are attached in the cylinder,
When the difference between the maximum drift amount and the reference drift amount is larger than the first determination value and the difference between the time constant and the reference time constant is equal to or less than the second determination value, Second determining means for determining that the in-cylinder pressure sensor is faulty;
The control device for an internal combustion engine according to claim 1, comprising: Deposit removal means for performing control for removing deposits when it is determined by the drift determination means that deposits are adhered in the cylinder;
A failure determination unit that determines a failure of the in-cylinder pressure sensor based on a difference between the maximum drift amount before the operation of the deposit removal unit and the maximum drift amount after the operation of the deposit removal unit;
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising:

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