JP2015194098A - Cylinder internal pressure sensor diagnosis method and vehicle operation control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the reliable failure diagnosis of a cylinder internal pressure sensor degraded by various factors.SOLUTION: A cylinder internal pressure sensor diagnosis method comprises: calculating a calculation value of a cylinder internal pressure using a cylinder internal pressure calculation expression based on thermodynamics (S106); calculating a pressure difference between the calculated calculation value and a cylinder internal pressure detected by a cylinder internal pressure sensor a predetermined number of times in one cylinder cycle (S108, S110); calculating a standard deviation of the pressure differences obtained in one cylinder cycle in a predetermined number of cylinder cycles (S112 to S116); calculating an average value of the standard deviations obtained by executing the calculation in the predetermined number of cylinder cycles (S118); repeatedly executing counting by a counter if the average value deviates from a predetermined pressure difference range (S122, S128); and determining that a failure occurs to the cylinder internal pressure sensor if the count value of the counter exceeds a predetermined alarm reference value (S124, S126).

Description

  The present invention relates to a method for diagnosing an in-cylinder pressure sensor that is provided in a cylinder of an internal combustion engine and detects an in-cylinder pressure, and particularly relates to a method for improving the reliability of diagnosis.

In an internal combustion engine, in order to obtain a stable and reliable combustion state, how to accurately grasp the pressure in a cylinder and reflect this in fuel injection control is an important issue. It is well known that it has been proposed and put to practical use.
Usually, a pressure sensor is used to detect the pressure in the cylinder, but since it is used in a high-pressure and high-temperature environment, ensuring its reliability is also an important issue.

  From such a point of view, for example, Patent Document 1 proposes a calibration method for an in-cylinder pressure sensor integrated with a glow plug that is structurally susceptible to deposits due to combustion. That is, the same document describes the detected pressure in the subsequent use state based on the difference between the pressure detected at the beginning of use before depositing on the pressure sensor and the pressure detected in a predetermined operation state. There has been proposed a calibration method that, by correcting, suppresses and reduces the influence of deposits attached to the in-cylinder pressure sensor integrated with the glow plug, and ensures the reliability of the pressure sensor.

JP 2010-71197 A (page 4-7, FIGS. 1 to 5)

  By the way, the above-mentioned conventional method is based on the viewpoint of reducing the influence on the detection value due to the deposit caused by the structure of the in-cylinder pressure sensor integrated with the glow plug. The factor that causes a decrease in reliability is not necessarily limited to deposit. In particular, the above-described conventional method is suitable for a glow plug-integrated in-cylinder pressure sensor, but in another form, that is, in a cylinder pressure sensor disposed in a cylinder of an internal combustion engine separately from a glow plug. Not necessarily suitable.

  The present invention has been made in view of the above circumstances, and there are provided an in-cylinder pressure sensor diagnosis method and a in-cylinder pressure sensor diagnosis method that enable reliable diagnosis of an in-cylinder pressure sensor deteriorated due to various factors. An applied vehicle motion control device is provided.

In order to achieve the above object of the present invention, the cylinder pressure sensor failure diagnosis method according to the present invention comprises:
A method for diagnosing a cylinder pressure sensor disposed in a cylinder of an internal combustion engine, comprising:
A calculated value of the in-cylinder pressure is calculated using an in-cylinder pressure calculation formula for calculating a pressure in the cylinder set based on thermodynamics, and then detected by the calculated value and the in-cylinder pressure sensor. The pressure difference from the in-cylinder pressure is determined a predetermined number of times during one cylinder cycle, then the standard deviation of the pressure difference obtained during the one cylinder cycle is determined for a predetermined number of cylinder cycles, An average value of standard deviations obtained by executing the predetermined number of cylinder cycles is calculated, and when the average value deviates from a predetermined pressure difference range, it is determined that the in-cylinder pressure sensor has failed. It will be.
In order to achieve the above object of the present invention, a vehicle operation control device according to the present invention includes:
An electronic control unit configured to execute an operation control process of the vehicle, and an output signal of an in-cylinder pressure sensor that is provided in a cylinder of the internal combustion engine and detects an in-cylinder pressure is an operation control process of the vehicle In the vehicle operation control device configured to be provided for,
The electronic control unit is
A calculated value of the in-cylinder pressure is calculated using an in-cylinder pressure calculation formula for calculating a pressure in the cylinder set based on thermodynamics, and then detected by the calculated value and the in-cylinder pressure sensor. The pressure difference from the in-cylinder pressure is determined a predetermined number of times during one cylinder cycle, then the standard deviation of the pressure difference obtained during the one cylinder cycle is determined for a predetermined number of cylinder cycles, An average value of standard deviations obtained by executing the predetermined number of cylinder cycles is calculated, and when the average value deviates from a predetermined pressure difference range, it is determined that the in-cylinder pressure sensor has failed. It will be.

  According to the present invention, the calculated value of the in-cylinder pressure is obtained using the in-cylinder pressure calculation formula based on thermodynamics, and the difference between the calculated value and the actually measured value is diagnosed. Thus, there is an effect that it is possible to make a fault diagnosis with a certain amount of time and to contribute to improving the reliability of the vehicle operation control.

It is a block diagram which shows the structural example of the vehicle operation control apparatus with which the in-cylinder pressure sensor diagnostic method in embodiment of this invention is applied. 2 is a subroutine flowchart showing a procedure of in-cylinder pressure sensor diagnosis processing in an embodiment of the present invention executed in an electronic control unit constituting the vehicle operation control device shown in FIG. 1.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a configuration example of a vehicle operation control device to which the in-cylinder pressure sensor diagnosis process in the embodiment of the present invention is applied will be described with reference to FIG.
FIG. 1 shows an example of the configuration of the main components related to the operation control of the diesel engine 1 provided with the exhaust gas recirculation device 102 in particular.

  In the configuration shown in FIG. 1, the intake manifold 2a of a diesel engine (hereinafter referred to as "engine") 1 has an intake pipe 2 for taking in air necessary for fuel combustion, and an exhaust manifold 4b. Are connected to exhaust pipes 3 for exhausting exhaust gas.

  A communication path 5 that communicates the intake pipe 2 and the exhaust pipe 3 is provided at an appropriate position of the intake pipe 2 and the exhaust pipe 3. 5, an EGR valve 6 for adjusting the exhaust gas recirculation amount and an EGR cooler 7 for cooling the passing exhaust gas are arranged in this order.

Further, a known and well-known configuration in which the variable turbine 9 provided on the downstream side of the communication passage 5 in the exhaust pipe 3 and the compressor 10 provided on the upstream side of the communication passage 5 in the intake pipe 2 are main components. A variable turbo 8 is provided. Then, the compressor 10 is rotated by the rotational force obtained by the variable turbine 9, and the compressed air is sent to the intake manifold 4a as intake air.
Further, the intake pipe 2 is provided with an intercooler 11 that cools intake air at an appropriate position between the communication passage 5 and the variable turbo 8 described above.
An intake throttle valve 12 for adjusting the amount of intake air is provided between the intercooler 11 and the communication path 5.

In the embodiment of the present invention, each cylinder (not shown) in the engine 1 is provided in order to provide fuel injection control based on viewpoints such as stability of the combustion state in the engine 1, reliability, and improvement in fuel efficiency. It is assumed that the pressure (in-cylinder pressure) is configured to be detectable.
That is, when the engine 1 is configured to have n cylinders, in-cylinder pressure sensors 15-1 to 15-n for detecting the in-cylinder pressure are attached to the inside of each cylinder (not shown). The detection signal is input to the electronic control unit 101 described later.

An electronic control unit (indicated as “ECU” in FIG. 1) 101 performs a fuel injection control process and an EGR control process for the engine 1, an in-cylinder pressure sensor diagnosis process in the embodiment of the present invention, and the like, and an intake throttle The operation of the valve 12 is controlled.
The electronic control unit 101 includes, for example, a microcomputer (not shown) having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and an input interface circuit ( And an output interface circuit (not shown) as main components.

The electronic control unit 101 includes an output signal of an air mass sensor 16 provided at an appropriate position of the intake pipe 2 on the upstream side of the variable turbo 8 to detect the intake air amount, and an atmospheric pressure sensor 17 that detects atmospheric pressure. The output signal, the output signal of the intake air temperature sensor 18 that detects the intake air temperature in the vicinity of the intake manifold 4a, the output signal of the engine rotation sensor 27 that detects the engine speed, and the output signal of the crank angle sensor 28 that detects the crank angle. In addition to the input, the output signals of the in-cylinder pressure sensors 15-1 to 15-n are input and used for engine operation control processing, in-cylinder pressure sensor failure diagnosis processing in an embodiment of the present invention described later, and the like. It is like that.
Further, the outputs of the accelerator opening sensor 19, the engine coolant temperature sensor 20, the intake manifold pressure sensor 21, the valve opening sensor 22, the throttle opening sensor 23, the flap sensor 24, the gear position detection sensor 25, and the clutch stroke sensor 26 are output. A signal is input to the electronic control unit 101, and is used for engine operation control processing, in-cylinder pressure sensor failure diagnosis processing in an embodiment of the present invention described later, and the like as described above.

Next, the procedure of the in-cylinder pressure sensor diagnosis process executed in the electronic control unit 101 will be described with reference to the subroutine flowchart shown in FIG.
When the process by the electronic control unit 101 is started, first, it is determined whether or not a predetermined diagnosis start condition for starting a series of subsequent diagnosis processes is satisfied (see step S102 in FIG. 2). ).

  Here, the in-cylinder pressure sensor diagnosis process in the embodiment of the present invention is executed in a state where the accelerator (not shown) is not stepped on and combustion is not generated in the combustion chamber (not shown) of the engine 1. By doing so, a reliable diagnosis can be realized without being affected by combustion or the like. Therefore, first, as an element to be determined whether or not the above-described diagnosis start condition is satisfied, a plurality of diagnosis start determination elements set in advance to determine that the vehicle is in such a driving state Are used, and conditions are set for each.

As the diagnosis start determination element in the embodiment of the present invention, specifically, accelerator opening, fuel injection state, engine speed, engine temperature, intake manifold temperature, intake manifold pressure, EGR valve opening, throttle valve opening, Exhaust flap usage, gear settings, and clutch stroke are selected.
The “accelerator opening” is the opening of an accelerator (not shown) detected by the accelerator opening sensor 19 and input to the electronic control unit 101.
“Fuel injection state” means the state of fuel injection performed on the engine 1 by the fuel injection control executed by the electronic control unit 101 as in the prior art. It is represented by a stroke, a compression stroke, an expansion stroke, a fuel stroke, and the like. These pieces of information are grasped in a fuel injection control process executed in the electronic control unit 101, and it is preferable to use the information.

The “engine temperature” is represented by the coolant temperature of the engine 1 detected by the engine coolant temperature sensor 20.
“Intake manifold temperature” is the intake air temperature in the intake manifold 4 b detected by the intake air temperature sensor 18.
“Intake manifold pressure” is the intake pressure in the intake manifold 4 b detected by the intake manifold pressure sensor 21.
The “EGR valve opening” is the opening of the EGR valve 6 detected by the valve opening sensor 22.

“Throttle valve opening” is the opening of a throttle valve (not shown) detected by the throttle opening sensor 23.
“Exhaust flap use state” indicates whether the exhaust flap (not shown) is opened or closed, and is open / closed corresponding to opening / closing of the exhaust flap (not shown) detected by the flap sensor 24. Signal. The exhaust flap is not an essential element because some exhaust flaps are not provided in some vehicles.
The “gear setting” is a gear setting that is set in a transmission (not shown), and is detected by a gear detection sensor 25 that detects the setting of the gear.
The “clutch stroke” is a clutch depression amount (clutch straw k) (not shown), and is detected by a clutch stroke sensor 26 that detects the clutch stroke.

  In the embodiment of the present invention, as described above, the diagnosis is started in a state where the accelerator (not shown) is not stepped on and no combustion occurs in the cylinder (not shown) of the engine 1. Therefore, among the above-mentioned diagnosis start determination elements, the “accelerator opening” is the diagnosis start condition for the accelerator opening zero, and the “fuel injection state” is in a state in which no combustion occurs. Is the diagnosis start condition. As for other diagnosis start determination elements, on the assumption that the above-described diagnosis start conditions of “accelerator opening” and “fuel injection state” are satisfied, appropriate conditions that do not hinder the start of diagnosis are It is set based on test results and simulation results in consideration of specific specifications.

Therefore, in order to determine that the diagnosis start condition is satisfied in step S102, it is a premise that all of the plurality of diagnosis start elements described above satisfy the respective diagnosis start conditions.
If it is determined in step S102 that the diagnosis start condition is satisfied (in the case of YES), the process proceeds to step S104 described below, while the diagnosis start condition is determined not to be satisfied ( In the case of NO), a series of processing is terminated and it is temporarily returned to a main routine (not shown) because it is not in a state suitable for executing the subsequent processing.

In step S104, 1 is set to the cycle variable Nc that represents the number of repetitions of the pressure model calculation in step S106 described later and the pressure difference calculation in step S108.
The series of in-cylinder pressure sensor diagnosis processes in the embodiment of the present invention are performed for all the in-cylinder pressure sensors 15-1 to 15-n, in other words, for all the cylinders (not shown). It has become. Further, for each in-cylinder pressure sensor 15-1 to 15-n, a pressure model calculation in step S106 and a pressure difference calculation in step S108, which will be described later, are predetermined in one cylinder cycle from the viewpoint of improving the reliability of diagnostic accuracy. And the predetermined number of cylinder cycles Ks are repeatedly executed.
The previous cycle variable Nc is used to determine the number of cylinder cycles in steps S106 and S108, as will be described later.

Next, the pressure model calculation is executed (see step S106 in FIG. 2).
This pressure model calculation is a process of calculating a calculated value of the in-cylinder pressure, in other words, an estimated value. As will be described below, an estimated value of the in-cylinder pressure based on the in-cylinder (in-cylinder) pressure model is calculated. The calculated value of the in-cylinder pressure is calculated by the in-cylinder pressure calculation formula.

  That is, in the embodiment of the present invention, the calculated value Pcyl_mod of the in-cylinder pressure is calculated by the following formula 1.

Pcyl_mod = Pact × (Vc / Vcyl) ^κ Equation 1

  Here, “Pact” is the in-cylinder pressure at the bottom dead center of the piston, and since this pressure is substantially equal to the intake pressure of the intake manifold 4a, basically, the intake manifold pressure detected by the intake manifold pressure sensor 21 is Although used as an actual measurement value of the pressure at the bottom dead center of the piston, in the embodiment of the present invention, as will be described later, it is used after being subjected to a predetermined correction from the viewpoint of improving the accuracy of the Pact value. It is supposed to be

“Vc” is the volume of one cylinder (cylinder) at the bottom dead center of the piston, and for this value, a calculated value based on a specific specification of the engine 1 is used. .
“Vcyl” is the volume of one cylinder (cylinder) at an arbitrary crank angle, and this value is a crank angle at the time of execution of step S106 according to a volume calculation formula set based on a specific specification of the engine 1. The calculated value of the volume of a cylinder (not shown) with respect to is calculated and used.
“Κ” is a specific heat ratio.

  The above formula 1 is a formula derived based on thermodynamics. However, as a result of earnest research, the inventor of the present application has always obtained the formula 1 by the influence of the vertical movement of a piston (not shown) in the cylinder. However, in order to use Equation 1, it came to the conclusion that it is necessary to perform the following correction.

First, since the pressure Pact at the bottom dead center of the piston greatly affects the accuracy of the estimated value obtained by Equation 1, it is not sufficient to use only the actual value of the intake manifold pressure. In the embodiment of the present invention, Pact = Intake manifold pressure + Intake manifold correction term.
In the intake manifold correction term, a correction value corresponding to the engine speed and the intake manifold temperature (hereinafter, referred to as “intake manifold correction value” for convenience of explanation) is determined.
The intake manifold temperature is the intake air temperature in the vicinity of the intake manifold 4 a detected by the intake air temperature sensor 18.

That is, the intake manifold correction values in the embodiment of the present invention are determined for various engine speeds and intake manifold temperatures based on test results and simulation results in consideration of specific specifications of the engine 1 and the like. It has become a thing.
Furthermore, in the embodiment of the present invention, the corresponding intake manifold correction values are mapped so as to be readable using the engine speed and the intake manifold temperature as input parameters (hereinafter, this map is referred to as an “intake manifold correction map” for convenience of explanation). These are stored in advance in an appropriate storage area of the electronic control unit 101.

  Therefore, when the calculated value Pcyl_mod of the in-cylinder pressure is calculated based on the previous equation 1 in step S106, the intake manifold correction value corresponding to the engine speed and intake manifold temperature at the time of calculation is read from the intake manifold correction map. Then, it is added to the intake manifold pressure and used as the value of the pressure Pact at the bottom dead center of the piston.

  Further, the value of the specific heat ratio κ varies depending on the temperature. However, in the cylinder, the value varies depending on the movement of the piston (not shown). Therefore, the calculation of Equation 1 is performed using a normal fixed value. In this case, the value varies greatly depending on the position of the piston, and the calculated value Pcyl_mod of the in-cylinder pressure calculated by Expression 1 also changes greatly. Therefore, the meaning of using Expression 1 as a pressure model is lost.

As a result of earnest research, the inventor of the present application has come to know that the specific heat ratio κ changes greatly from the vicinity of the top dead center, particularly when the piston goes to the top dead center. As a result, the conclusion was reached that the determination of the specific heat ratio with respect to the crank angle and the engine speed based on the test results and simulation results is optimal for improving the accuracy of the calculated value of Equation 1.
In the embodiment of the present invention, paying attention to this point, the specific heat ratio κ is a map configured to be able to read a predetermined value with respect to the crank angle and the engine speed (hereinafter referred to as “ The specific heat ratio determined for the combination of the crank angle and the engine speed at the time of calculation is used for the calculation of Equation 1.

  The specific heat ratio map, like the previous intake manifold correction map, determines specific heat ratios for various crank angles and engine speeds based on test results and simulation results in consideration of specific specifications of the engine 1 and the like. It is preferable that the value is configured so that the crank angle and the engine speed can be read out as input parameters, and stored in an appropriate storage area of the electronic control unit 101.

  Accordingly, in step S106, the calculated value Pcyl_mod of the in-cylinder pressure is calculated based on the equation 1. At this time, the above-described intake manifold correction value is added to the intake manifold pressure as the pressure Pact at the piston bottom dead center. Further, the specific heat ratio κ is a value corresponding to the crank angle and the engine speed.

Next, in step S108, pressure difference calculation is performed.
That is, the calculated value Pcyl_mod of the in-cylinder pressure calculated in step S106 and the cylinder detected by the in-cylinder pressure sensor of the target cylinder (not shown) among the in-cylinder pressure sensors 15-1 to 15-n. A pressure difference ΔP with respect to the internal pressure Pcyl is calculated by the following equation 2, and the calculated pressure difference ΔP is temporarily stored in an appropriate storage area of the electronic control unit 101.

  ΔP = Pcyl−Pcyl_mod Equation 2

Next, in one cylinder cycle, it is determined whether or not predetermined sampling is completed, that is, whether or not a predetermined sampling number of pressure differences ΔP has been obtained (see step S110 in FIG. 2).
That is, in the embodiment of the present invention, the calculation in the previous step S106 and the calculation in step S108 are performed a plurality of times at appropriate intervals in one cylinder cycle to obtain a plurality of pressure differences ΔP. .
Here, the timing for reading (sampling) the in-cylinder pressure Pcyl, which is an actual measurement value, into the electronic control unit 101 is considered in consideration of the fact that the specific heat ratio κ changes relatively near the top dead center as described above. In the vicinity including the top dead center, a relatively short interval is set so that a relatively large sampling value is obtained, and in other regions, the fluctuation of the specific heat ratio κ is considered to be small. It is preferable to set the timing relatively sparse.

  If it is determined in step S110 that the predetermined sampling has been completed (in the case of YES), the process proceeds to step S112 described below, while it is determined that the predetermined sampling has not yet been completed ( In the case of NO), the processing from the previous step S106 is repeated.

In step S112, the required number of pressure differences ΔP acquired during one cylinder cycle is calculated based on a well-known calculation method.
The calculated standard deviation is provisionally stored in an appropriate storage area of the electronic control unit 101.

Next, it is determined whether or not the cycle variable Nc has exceeded a predetermined number of cycles Ks (see step S114 in FIG. 2).
That is, of the in-cylinder pressure sensors 15-1 to 15-n, whether or not the pressure difference ΔP has been acquired over the Ks cylinder cycle for the in-cylinder pressure sensor that is the acquisition target of the pressure difference ΔP at this time. Is determined, and if it is determined that the cycle variable Nc exceeds the predetermined number of cycles Ks (in the case of YES), it is determined that the required number of standard deviations has been obtained, and the process proceeds to step S118 described below. .

  On the other hand, if it is determined in step S114 that the cycle variable Nc has not yet exceeded the predetermined number of cycles Ks (in the case of NO), 1 is added to the cycle variable Nc at this time to obtain a new cycle Nc. (See step S116 in FIG. 2), the processing from the previous step S106 is repeated.

In step S118, the average value is calculated for Nc standard deviations.
In the embodiment of the present invention, as described above, one in-cylinder pressure sensor is sampled a predetermined number of times during one cylinder cycle, and the standard deviation of the pressure difference ΔP is obtained. Since Nc cylinder cycles are repeated, Nc standard deviations are obtained for the pressure difference ΔP of one in-cylinder pressure sensor.

Next, it is determined whether or not the average value calculated as described above is within a predetermined pressure difference range (see step S120 in FIG. 2). At this time, the cylinder to be diagnosed If it is determined that the average value of the pressure difference of the internal pressure sensor (see step S118 in FIG. 2) is within the predetermined pressure difference range (in the case of YES), the in-cylinder pressure sensor to be diagnosed is not malfunctioning and will be described later. On the other hand, if it is determined that the calculated average value of the pressure differences is not within the predetermined pressure difference range (in the case of NO), the cylinder pressure sensor to be diagnosed is temporarily damaged. Therefore, the process proceeds to step S122 described below.
Here, the predetermined pressure difference range is preferably set based on the test results and simulation results in consideration of the specific specifications of the in-cylinder pressure sensors 15-1 to 15-n.

In step S122, the counting operation of the failure counter is executed.
In the embodiment of the present invention, as described above, when the average value of the pressure difference of a certain in-cylinder pressure sensor exceeds a predetermined pressure difference range, the alarm sound is Rather than performing an alarm operation such as a warning display, it is determined that a failure has occurred when the predetermined pressure difference range is exceeded a predetermined number of times (reference number) (step in FIG. 2). (See S126).
Therefore, when it is determined that the average value of the pressure difference of a certain cylinder pressure sensor exceeds the predetermined pressure difference range (see step S120 in FIG. 2), first, the count value of the failure counter is increased by a predetermined number. Yes.
The failure counter is realized by executing this kind of software processing well known in the electronic control unit 101, and one failure counter is provided for each of the in-cylinder pressure sensors 15-1 to 15-n. It has become a thing.

  In step S124, it is determined whether or not the count value of the failure counter has exceeded a predetermined count value (alarm reference value) Cs. If it is determined that the alarm reference value has been exceeded (YES), the diagnosis target It is determined that the in-cylinder pressure sensor is faulty (see step S126 in FIG. 2), and in a main routine (not shown), a required alarm process is executed to generate an alarm sound and an alarm display such as an alarm display by a display element. The operation will be executed.

On the other hand, if it is determined in step S124 that the count value of the failure counter has not yet exceeded the alarm reference value Cs (in the case of NO), it is determined that there is no failure state that still results in an alarm, and the process proceeds to step S128. It will go on.
In step S128, it is determined whether or not diagnosis has been completed for all cylinders, that is, whether or not the above-described processing has been performed for the in-cylinder pressure sensors 15-1 to 15-n in all cylinders. If it is determined that the diagnosis has not been completed (in the case of NO), the process returns to the previous step S104, and the above-described series of processing is executed for the in-cylinder pressure sensor of the next cylinder. .

If it is determined in step S128 that the diagnosis for all cylinders has been completed (in the case of YES), the series of processing is terminated and the process returns to the main routine (not shown).
After returning to the main routine (not shown), the subroutine shown in FIG. 2 is repeatedly executed at the required timing determined by the main routine.

  This is suitable for an internal combustion engine in which reliable failure determination of an in-cylinder pressure sensor deteriorated due to various factors is desired.

DESCRIPTION OF SYMBOLS 1 ... Engine 15-1 to 15-n ... In-cylinder pressure sensor 18 ... Intake temperature sensor 27 ... Engine rotation sensor 28 ... Crank angle sensor 101 ... Electronic control unit

Claims (6)

A method for diagnosing a cylinder pressure sensor disposed in a cylinder of an internal combustion engine, comprising:
A calculated value of the in-cylinder pressure is calculated using an in-cylinder pressure calculation formula for calculating a pressure in the cylinder set based on thermodynamics, and then detected by the calculated value and the in-cylinder pressure sensor. The pressure difference from the in-cylinder pressure is determined a predetermined number of times during one cylinder cycle, then the standard deviation of the pressure difference obtained during the one cylinder cycle is determined for a predetermined number of cylinder cycles, An average value of standard deviations obtained by executing the predetermined number of cylinder cycles is calculated, and when the average value deviates from a predetermined pressure difference range, it is determined that the in-cylinder pressure sensor has failed. In-cylinder pressure sensor failure diagnosis method. The in-cylinder pressure calculation formula is:
The calculated value of in-cylinder pressure is Pcyl_mod, the in-cylinder pressure at the piston bottom dead center is Pact, the volume of one cylinder (cylinder) at the piston bottom dead center is Vc, the volume of one cylinder (cylinder) at an arbitrary crank angle is Vcyl, Let the specific heat ratio be κ,
Pcyl_mod = Pact × (Vc / Vcyl) ^κ ,
The in-cylinder pressure Pact at the bottom dead center of the piston is a value obtained by adding a correction term to the intake pressure in the intake manifold, and the correction term corresponds to various combinations of the engine speed and the intake air temperature in the intake manifold. Pre-set values are used,
The in-cylinder pressure sensor failure diagnosis method according to claim 1, wherein the specific heat ratio κ is a value set in advance for various combinations of a crank angle and an engine speed.   During the one-cylinder cycle, the in-cylinder pressure sampling interval by the in-cylinder pressure sensor in the vicinity of the cylinder top dead center is made smaller than the sampling interval in the region excluding the vicinity of the cylinder top dead center. The in-cylinder pressure sensor failure diagnosis method according to claim 2. An electronic control unit configured to execute an operation control process of the vehicle, and an output signal of an in-cylinder pressure sensor that is provided in a cylinder of the internal combustion engine and detects an in-cylinder pressure is an operation control process of the vehicle In the vehicle operation control device configured to be provided for,
The electronic control unit is
A calculated value of the in-cylinder pressure is calculated using an in-cylinder pressure calculation formula for calculating a pressure in the cylinder set based on thermodynamics, and then detected by the calculated value and the in-cylinder pressure sensor. The pressure difference from the in-cylinder pressure is determined a predetermined number of times during one cylinder cycle, then the standard deviation of the pressure difference obtained during the one cylinder cycle is determined for a predetermined number of cylinder cycles, An average value of standard deviations obtained by executing the predetermined number of cylinder cycles is calculated, and when the average value deviates from a predetermined pressure difference range, it is determined that the in-cylinder pressure sensor has failed. A vehicle operation control device. The in-cylinder pressure calculation formula is:
The calculated value of in-cylinder pressure is Pcyl_mod, the in-cylinder pressure at the piston bottom dead center is Pact, the volume of one cylinder (cylinder) at the piston bottom dead center is Vc, the volume of one cylinder (cylinder) at an arbitrary crank angle is Vcyl, Let the specific heat ratio be κ,
Pcyl_mod = Pact × (Vc / Vcyl) ^κ ,
The in-cylinder pressure Pact at the bottom dead center of the piston is a value obtained by adding a correction term to the intake pressure in the intake manifold, and the correction term corresponds to various combinations of the engine speed and the intake air temperature in the intake manifold. Pre-set values are used,
The vehicle operation control device according to claim 4, wherein the specific heat ratio κ uses a preset value for various combinations of a crank angle and an engine speed.   The electronic control unit is configured such that, during the one cylinder cycle, the in-cylinder pressure sampling interval in the vicinity of the cylinder top dead center is smaller than the sampling interval in the region excluding the vicinity of the cylinder top dead center. The vehicle operation control device according to claim 5, wherein sampling is executed as

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