JP5071808B2 - In-cylinder pressure sensor abnormality diagnosis device - Google Patents

Description

  The present invention relates to an in-cylinder pressure sensor abnormality diagnosis apparatus, and more particularly to an apparatus for diagnosing whether or not a sensitivity abnormality has occurred in an in-cylinder pressure sensor that detects an in-cylinder pressure of an internal combustion engine.

  2. Description of the Related Art In recent years, control devices for internal combustion engines have been developed that detect in-cylinder combustion states using in-cylinder pressure detected by an in-cylinder pressure sensor and control various control amounts such as ignition timing based on the results. Yes. In the case of a multi-cylinder internal combustion engine, an in-cylinder pressure sensor is provided for each cylinder, and control based on the detected in-cylinder pressure is performed for each cylinder.

  By the way, if an abnormality occurs in the in-cylinder pressure sensor, accurate in-cylinder information cannot be obtained, and accurate engine control cannot be performed. Therefore, in particular, in the field of automobiles, it is necessary to diagnose an abnormality of the in-cylinder pressure sensor (OBD; OnBoard Diagnosis) in an on-vehicle state, and therefore an abnormality diagnosis device for the in-cylinder pressure sensor has been developed.

  In the apparatus described in Patent Document 1, a correction parameter that minimizes the deviation between the pressure detected by the in-cylinder pressure sensor and the motoring pressure in the compression stroke of the internal combustion engine is identified, and the correction parameter is outside the predetermined range when the fuel is cut. When this happens, the cylinder pressure sensor is abnormal.

JP 2006-284533 A

  It may be possible to diagnose the abnormality of the in-cylinder pressure sensor itself with this conventional apparatus. However, depending on the conventional apparatus, it is not possible to identify and diagnose even an abnormality in sensor sensitivity due to deterioration with time.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an abnormality diagnosis device for an in-cylinder pressure sensor that can accurately diagnose an abnormality in sensitivity of the in-cylinder pressure sensor.

According to one aspect of the invention,
An apparatus for diagnosing an abnormality of an in-cylinder pressure sensor for detecting an in-cylinder pressure of an internal combustion engine,
By normalizing the total heat generation parameter ΔPV ^κ correlated with the total heat generation amount generated by one combustion of the internal combustion engine by the fuel amount τ used for the one combustion, low heat generation of the fuel Combustion parameter calculation means for calculating a combustion parameter H corresponding to the quantity q _fuel ;
In-cylinder pressure, comprising: a determination unit that determines whether the in-cylinder pressure sensor is normal or abnormal based on the combustion parameter H calculated by the combustion parameter calculation unit and the lower heating value q _{fuel of the fuel.} A sensor abnormality diagnosis device is provided.

However, [Delta] PV [ ^kappa] = P ([theta] ₂ ) V ([theta] ₂ ) [ ^kappa] -P ([theta] ₁ ) V ([theta] ₁ ) [ ^kappa] , P ([theta] ₁ ), P ([theta] ₂ ) are predetermined values before and after the start of combustion. In-cylinder pressure detected by the in-cylinder pressure sensor at crank angles θ ₁ and θ ₂ , V (θ ₁ ) and V (θ ₂ ) are in-cylinder volumes at the crank angles θ ₁ and θ ₂ , and κ is a predetermined specific heat. Is the ratio.

When the sensitivity of the in-cylinder pressure sensor is normal, the value of the combustion parameter H calculated based on the detected in-cylinder pressure is a value corresponding to the lower heating value q _fuel of the _fuel , more specifically, the lower heating value q of the fuel. _The value is almost equal to _fuel . In other words, when the sensitivity of the in-cylinder pressure sensor is abnormal, the value of the combustion parameter H calculated based on the detected in-cylinder pressure is not substantially equal to the lower heating value q _{fuel of the fuel} . Therefore, using this characteristic, in one embodiment of the present invention, the abnormality of the in-cylinder pressure sensor is diagnosed based on the combustion parameter H and the lower heating value q _{fuel of the fuel} . An in-cylinder pressure sensor sensitivity abnormality can be identified and diagnosed with high accuracy.

Preferably, the combustion parameter H is calculated by dividing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ.

Preferably, the determination unit calculates an abnormality determination parameter α by dividing the combustion parameter H by the lower heating value q _fuel and determines whether the abnormality determination parameter α is within a predetermined range near 1. Then, it is determined whether the in-cylinder pressure sensor is normal or abnormal.

  When the sensitivity of the in-cylinder pressure sensor is normal, the value of the abnormality determination parameter α calculated based on the detected in-cylinder pressure is approximately 1. Conversely, when the sensitivity of the in-cylinder pressure sensor is abnormal, the value of the abnormality determination parameter α is not substantially 1. Therefore, using this characteristic, in the preferred embodiment, the abnormality of the in-cylinder pressure sensor is diagnosed based on whether or not the actual value of the abnormality determination parameter α is within a predetermined range near 1. This also makes it possible to identify an abnormality in the sensitivity of the in-cylinder pressure sensor and accurately diagnose this.

  Preferably, when the determination means determines that the in-cylinder pressure sensor is abnormal, a correction amount for correcting the value of the in-cylinder pressure obtained from the output of the in-cylinder pressure sensor is calculated based on the abnormality determination parameter α. Correction amount calculation means is further provided.

  According to this, even when the sensitivity of the in-cylinder pressure sensor is abnormal, the value of the detected in-cylinder pressure can be corrected to an accurate value using the correction amount, and the control using the detected in-cylinder pressure is continuously performed. become able to.

Preferably, the abnormality diagnosis device for the in-cylinder pressure sensor detects an alcohol concentration of the _fuel, and a low level that sets the low heating value q _fuel based on the alcohol concentration detected by the alcohol concentration detection unit. And a calorific value setting means.

In the case of a so-called bi-fuel engine that can use a fuel containing alcohol, the value of the lower calorific value q _fuel changes according to the alcohol concentration of the _fuel . In this preferred embodiment, since the lower calorific value q _fuel is set based on the alcohol concentration, abnormality diagnosis can be performed without trouble even in the case of a bi-fuel engine.

  Preferably, the abnormality diagnosis device for the in-cylinder pressure sensor prohibits abnormality diagnosis of the in-cylinder pressure sensor for a predetermined time when a change amount of the alcohol concentration detected by the alcohol concentration detection unit per predetermined time is larger than a predetermined value. A diagnosis prohibition unit is further provided.

Immediately after the fuel alcohol concentration changes, such as immediately after fuel supply, the alcohol concentration value detected by the alcohol concentration detection means differs from the alcohol concentration value of the fuel actually supplied to the internal combustion engine. There is a time difference based on the delay. During this time difference, the lower heating value q _Fuel that has been set based on the detected alcohol concentration, actually is different from the lower heating value q _Fuel of the injected fuel, possible erroneous diagnosis when abnormality diagnosis by using a former There is sex. Therefore, in this preferred embodiment, abnormality diagnosis is prohibited during the time difference. Specifically, when the amount of change in the detected alcohol concentration per predetermined time is greater than a predetermined value, it is considered that the alcohol concentration of the fuel has changed greatly, and a predetermined time that can eliminate the time difference based on transport delay, Abnormal diagnosis of in-cylinder pressure sensor is prohibited. Thereby, misdiagnosis can be prevented and diagnostic accuracy can be improved.

  Preferably, the diagnosis prohibiting unit sets the predetermined time based on a fuel passage volume in a predetermined section and a fuel consumption per unit time.

  The time difference is a value related to the fuel passage volume in the predetermined section and the fuel consumption per unit time. Therefore, by setting the predetermined time based on the fuel passage volume and the fuel consumption, it is possible to reliably prevent erroneous diagnosis while minimizing the diagnosis prohibition time and the decrease in diagnosis frequency.

  According to the present invention, an excellent effect that an abnormality in sensitivity of the in-cylinder pressure sensor can be accurately diagnosed is exhibited.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an internal combustion engine (engine) according to the present embodiment. As shown in the figure, the internal combustion engine 1 generates power by burning a mixture of fuel and air in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston in the combustion chamber 3. . The internal combustion engine 1 of the present embodiment is a multi-cylinder internal combustion engine for automobiles, more specifically, a parallel three-cylinder spark ignition internal combustion engine, that is, a gasoline engine. However, the internal combustion engine to which the present invention can be applied is not limited to this, and the number of cylinders, the type, the use, etc. are not particularly limited as long as it is a multi-cylinder internal combustion engine.

  Although not shown, the cylinder head of the internal combustion engine 1 is provided with an intake valve for opening and closing the intake port and an exhaust valve for opening and closing the exhaust port for each cylinder. Each intake valve and each exhaust valve is provided by a camshaft. Can be opened and closed. A spark plug 7 for igniting the air-fuel mixture in the combustion chamber 3 is attached to the top of the cylinder head for each cylinder.

  The intake port of each cylinder is connected to a surge tank 8 which is an intake air collecting chamber via a branch pipe 4 for each cylinder. An intake pipe 13 is connected to the upstream side of the surge tank 8, and an air cleaner 9 is provided at the upstream end of the intake pipe 13. An air flow meter 5 for detecting the intake air amount and an electronically controlled throttle valve 10 are incorporated in the intake pipe 13 in order from the upstream side. An intake passage is formed by the intake port, the branch pipe 4, the surge tank 8 and the intake pipe 13.

  An injector (fuel injection valve) 12 that injects fuel into the intake passage, particularly into the intake port, is provided for each cylinder. The fuel injected from the injector 12 is mixed with intake air to form an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 3 when the intake valve is opened, compressed by the piston, and ignited and burned by the spark plug 7. The injector 12 of each cylinder is connected to a common delivery pipe 22, and a fuel pipe 23 is connected to the delivery pipe 22. Fuel in a fuel tank (not shown) is supplied to a delivery pipe 22 through a fuel pipe 23 by a feed pump (not shown), and is injected from the injector 12 when the injector 12 is energized.

  On the other hand, the exhaust port of each cylinder is connected to the exhaust manifold 14. An exhaust pipe 6 is connected to the exhaust manifold 14. An exhaust passage is formed by the exhaust port, the exhaust manifold 14 and the exhaust pipe 6. A catalyst 11 made of a three-way catalyst is attached to the exhaust pipe 6. Air-fuel ratio sensors for detecting the air-fuel ratio of exhaust gas, that is, a pre-catalyst sensor 17 and a post-catalyst sensor 18 are installed on the upstream side and the downstream side of the catalyst 11, respectively.

  The spark plug 7, the throttle valve 10, the injector 12, and the like described above are electrically connected to an electronic control unit (hereinafter referred to as ECU) 20 as control means. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. In addition to the air flow meter 5, the pre-catalyst sensor 17, and the post-catalyst sensor 18, the ECU 20 includes a crank angle sensor 16 that detects the crank angle of the internal combustion engine 1 and an accelerator that detects the accelerator opening, as shown in the figure. The opening sensor 15 and other various sensors are electrically connected via an A / D converter or the like (not shown). The ECU 20 controls the ignition plug 7, the throttle valve 10, the injector 12, etc. so as to obtain a desired output based on the detection values of various sensors, etc., and the ignition timing, fuel injection amount, fuel injection timing, throttle opening. Control the degree etc. The throttle opening is controlled to an opening corresponding to the accelerator opening, and the throttle opening increases as the accelerator opening increases. The ECU 20 calculates the engine speed of the internal combustion engine 1 based on the detection value of the crank angle sensor 16.

  In addition, an in-cylinder pressure sensor 21 including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like is provided for each cylinder. The in-cylinder pressure sensor 21 is disposed on the cylinder head so that the pressure receiving surface faces the combustion chamber 3, and is electrically connected to the ECU 20 via an A / D converter (not shown). The in-cylinder pressure sensor 21 provides the ECU 20 with a voltage signal proportional to the pressure in the combustion chamber 3, that is, in the cylinder.

  Next, abnormality diagnosis of the in-cylinder pressure sensor will be described.

  FIG. 2 shows the output characteristics of the in-cylinder pressure sensor 21, where the horizontal axis indicates the output voltage E (V) of the in-cylinder pressure sensor, and the vertical axis indicates the in-cylinder pressure P (MPa) as an input. As shown in the figure, the in-cylinder pressure P and the output voltage E are in a proportional relationship, and these relationships are represented by ΔP = G · ΔE. G is a conversion coefficient for converting the output voltage E into the in-cylinder pressure P, that is, a sensor sensitivity, and is a specific constant value inherently possessed by the in-cylinder pressure sensor. The output characteristic of the in-cylinder pressure sensor is generally expressed as ΔP = G · ΔE ± α (%), and includes a manufacturing error of α (%) (usually a value of 2 to 3%). Is normal. The present embodiment relates to an apparatus for diagnosing whether or not the sensor sensitivity G is out of the normal range due to deterioration over time or the like.

  In FIG. 2, the output characteristic of the in-cylinder pressure sensor as an intermediate product with a manufacturing error of 0% is indicated by I. In this case, the output voltage change amount ΔE becomes the in-cylinder pressure change amount ΔP. On the other hand, in the case of the in-cylinder pressure sensor indicated by II, the output voltage change amount ΔE + e1 with respect to the in-cylinder pressure change amount ΔP, and an output voltage change amount larger than the intermediate product is obtained. On the contrary, in the case of the in-cylinder pressure sensor indicated by III, the output voltage change amount ΔE-e2 with respect to the in-cylinder pressure change amount ΔP, and an output voltage change amount smaller than the intermediate product is obtained. Thus, in the case of a sensor that can obtain an output voltage change amount that is excessively larger or smaller than the intermediate output voltage change amount ΔE with respect to a constant in-cylinder pressure change amount ΔP, it is diagnosed as a sensitivity abnormality and a warning is given to the user. However, it is preferable to prompt replacement of the sensor.

In the case of abnormality diagnosis of the in-cylinder pressure sensor, in this embodiment, an in-cylinder pressure parameter PV ^κ that is a parameter correlated with the amount of heat generation Q in the cylinder is used. Here, P is the in-cylinder pressure P (θ) at a certain crank angle θ, V is the in-cylinder volume V (θ) at the crank angle θ, κ is the specific heat ratio, and PV ^κ = P (θ) V (θ) ^κ .

FIG. 3 shows the relationship among the in-cylinder pressure P, the heat generation amount Q, and the in-cylinder pressure parameter ^PVκ during one combustion in the specific cylinder. The heat generation amount is indicated by Q / 100 for convenience. The heat generation amount Q is based on the following formula (1):

As calculated and plotted. θ = 0 ° CA means compression top dead center. The specific heat ratio κ is a constant value and κ = 1.32.
dQ / dθ = {dP / dθ · V + κ · P · dV / dθ} / {κ-1} (1)

As can be seen from the figure, the change pattern of the heat generation amount Q and the in-cylinder pressure parameter PV ^κ before and after the start of combustion (ignition or ignition) in the cylinder, particularly in the range from about −180 ° C. to about 135 ° C. It is clear that the change pattern of the above is almost the same, and the heat generation amount Q and the in-cylinder pressure parameter ^PVκ have a good correlation.

The total amount of heat generated in one combustion correlates with the difference between the in-cylinder pressure parameter ^PVκ before and after the start of combustion. Therefore, the difference is obtained and used as a parameter representing the total heat generation amount, that is, a total heat generation amount parameter ΔPV ^κ . This total heat generation amount parameter ΔPV ^κ is expressed by the following equation (2).
_{^{ΔPV κ = {P (θ 2}} ) V (θ 2) κ -P (θ 1) V (θ 1) κ} ··· (2)

Here, P (θ ₁ ) and P (θ ₂ ) are in-cylinder pressures at predetermined crank angles θ ₁ and θ ₂ before and after the start of combustion, and V (θ ₁ ) and V (θ ₂ ) are the cranks. This is the in-cylinder volume at the angles θ ₁ and θ ₂ . In this embodiment, θ ₁ = −60 ° CA (60 ° before compression top dead center) and θ ₂ = 60 ° CA (60 ° after compression top dead center), but these values can be changed as appropriate.

By the way, a value obtained by normalizing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ used for one combustion becomes a value corresponding to the lower heating value q _fuel . More specifically, a value obtained by dividing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ used for one combustion becomes a value substantially equal to the lower heating value q _fuel . Here, the lower heating value q _fuel refers to the amount of heat energy that can be extracted per unit mass of fuel. When the fuel is gasoline, the lower heating value q _fuel is substantially constant (42 MJ / kg) regardless of whether it is heavy, light, or octane.

Therefore, in this embodiment, a value obtained by normalizing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ, more specifically, a value obtained by dividing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ, The parameter H = ΔPV ^κ / τ is defined, and abnormality diagnosis of the in-cylinder pressure sensor 21 is performed based on the combustion parameter H and the lower heating value q _fuel . That is, if the combustion parameter H calculated based on the actual detection value of the in-cylinder pressure sensor 21 is significantly different from the lower heating value q _fuel , it can be considered that an insensitivity abnormality has occurred in the in-cylinder pressure sensor 21. In this embodiment, abnormality diagnosis of the in-cylinder pressure sensor 21 is performed.

  Next, a first example of the abnormality diagnosis process of the present embodiment will be described based on the flowchart shown in FIG. The illustrated routine is repeatedly executed by the ECU 20 for each predetermined calculation cycle (for example, 16 msec) and for each cylinder.

  In the first step S101, engine warm-up determination is performed. That is, the water temperature Tw detected by a water temperature sensor (not shown) is compared with a predetermined value Tws (for example, 70 ° C.), and when Tw> Tws, it is regarded that the engine has been warmed up and the process proceeds to step S102. On the other hand, when Tw ≦ Tws, it is regarded that the engine is not warmed up, and this routine is terminated.

In step S102, the crank angle detected by the crank angle sensor 16 theta is whether reaches the first crank angle theta ₁ given before the start of combustion is determined. If the detected crank angle theta has not reached the first crank angle theta _1, and ends the current routine. On the other hand, when the detected crank angle θ reaches the first crank angle θ ₁ , the process proceeds to step S103, and the in-cylinder pressure P (θ ₁ ) detected by the in-cylinder pressure sensor 21 at the first crank angle θ ₁ is acquired. The cylinder volume V (θ ₁ ) at the first crank angle θ ₁ is acquired, and the process proceeds to step S104. Here, the ECU 20 calculates and acquires the in-cylinder volume V (θ ₁ ) corresponding to the first crank angle θ ₁ using a known arithmetic expression or map stored in advance.

In step S104, the crank angle detected by the crank angle sensor 16 theta is whether reaches a _second predetermined second crank angle theta after combustion starts is determined. If the detected crank angle theta has not reached the second crank angle theta _2, the present routine is ended. On the other hand, when the detected crank angle θ reaches the second crank angle θ ₂ , the process proceeds to step S105, and the in-cylinder pressure P (θ ₂ ) detected by the in-cylinder pressure sensor 21 at the second crank angle θ ₂ is acquired. Then, the in-cylinder volume V (θ ₂ ) at the second crank angle θ ₂ is acquired, and the process proceeds to step S106. The method for obtaining the in-cylinder volume V (θ ₂ ) from the second crank angle θ ₂ is the same as described above.

  In step S106, the fuel amount τ used for the previous combustion, specifically, the fuel injection amount τ is acquired. Since the ECU 20 sets the fuel injection amount τ by itself and injects an amount of fuel equal to the fuel injection amount from the injector 12, the fuel injection amount τ is an internal value of the ECU 20.

Next, in step S107, the combustion parameter H is calculated. Specifically, first, the value of the total heat generation amount parameter ΔPV ^κ is P (θ ₁ ), V (θ ₁ ), P (θ ₂ ), V (θ ₂ ) acquired in steps S103, S105, and S106. Is calculated according to the previous equation (2). Here, the specific heat ratio κ is a predetermined constant (eg, 1.32), but may be a variable according to the type of fuel, the air-fuel ratio, or the like. Next, the calculated total heat generation amount parameter ΔPV ^κ is divided by the fuel injection amount τ acquired in step S106, and the combustion parameter H is calculated.

Next, in step S108, the abnormality determination parameter α is calculated. Specifically, the combustion parameter H calculated in step S107 is divided by the lower heating value q _fuel to calculate the abnormality determination parameter α = H / q _fuel . Here, the value of the lower heating value q _fuel is stored in advance in the ECU 20 as a constant (42 MJ / kg corresponding to gasoline in this embodiment).

If the sensitivity of the in-cylinder pressure sensor 21 is normal, the calculated value of the combustion parameter H should be substantially equal to the lower heating value q _fuel as described above, and therefore the value of the combustion parameter H is set to the lower heating value. The calculated value of the abnormality determination parameter α obtained by dividing by q _fuel should be approximately 1. On the other hand, if the sensitivity of the in-cylinder pressure sensor 21 is abnormal, the values of the in-cylinder pressures P (θ ₁ ) and P (θ ₂ ) detected by the in-cylinder pressure sensor 21 deviate from the true values relatively greatly. The calculated value of the combustion parameter H is not substantially equal to the lower heating value q _fuel, and the calculated value of the abnormality determination parameter α is not substantially 1. Here, when the sensitivity of the in-cylinder pressure sensor 21 becomes excessive, the calculated value of the combustion parameter H becomes significantly larger than the lower heating value q _{fuel and} the calculated value of the abnormality determination parameter α becomes significantly larger than 1. Conversely, if the sensitivity of the in-cylinder pressure sensor 21 is too low, the calculated value of the combustion parameter H becomes significantly smaller than the lower heating value q _{fuel and} the calculated value of the abnormality determination parameter α becomes significantly smaller than 1.

Therefore, using this fact, in step S109, it is determined whether or not the calculated abnormality determination parameter α is within a predetermined range near 1. Specifically, it is determined whether or not the calculated abnormality determination parameter α is within a predetermined range that satisfies β ₁ <α <β ₂ . β ₁ is a predetermined value smaller than ₁ (eg, 0.07), β ₂ is a predetermined value larger than 1 (eg, 1.03), and the values of β ₁ and β ₂ take into account the required accuracy of in-cylinder pressure detection. Predetermined.

If the abnormality determination parameter α is within a predetermined range satisfying β ₁ <α <β ₂ , the in-cylinder pressure sensor 21 is substantially determined to be normal (particularly its sensitivity is normal), and the current routine ends. On the other hand, if the abnormality determination parameter α does not fall within a predetermined range satisfying β ₁ <α <β ₂ , the in-cylinder pressure sensor 21 is determined to be abnormal (particularly, its sensitivity is abnormal) in step S110, and a warning device (not shown) is illustrated in step S111. (Check lamp etc.) is activated, and this routine is completed.

  Next, a second example of the abnormality diagnosis process of the present embodiment will be described based on the flowchart shown in FIG. The illustrated routine is also repeatedly executed by the ECU 20 for each predetermined calculation cycle (for example, 16 msec) and for each cylinder.

In the second embodiment, when the sensitivity of the in-cylinder pressure sensor 21 is normal, paying attention to the fact that the combustion parameter H is substantially equal to the lower heating value q _fuel , the abnormality determination parameter α is calculated and abnormality diagnosis is performed without using it. Do.

Steps S201 to S207 are the same as steps S101 to S107. In step S208, it is determined whether or not the combustion parameter H calculated in step S207 is within a predetermined range that satisfies β ₁ q _fuel <H <β ₂ q _fuel . β ₁ , β ₂ , and q _fuel are the same values as described above.

If the combustion parameter H is within a predetermined range that satisfies β ₁ q _fuel <H <β ₂ q _fuel , the in-cylinder pressure sensor 21 is substantially determined to be normal (especially its sensitivity is normal), and this routine ends. . On the other hand, if the combustion parameter H is not within a predetermined range satisfying β ₁ q _fuel <H <β ₂ q _{fuel, it} is determined in step S209 that the in-cylinder pressure sensor 21 is abnormal (particularly, its sensitivity is abnormal), and a warning is issued in step S210. The device is activated and the current routine ends.

  Next, a third example of the abnormality diagnosis process of the present embodiment will be described based on the flowchart shown in FIG. The illustrated routine is also repeatedly executed by the ECU 20 for each predetermined calculation cycle (for example, 16 msec) and for each cylinder.

  In the third embodiment, when it is determined that the sensitivity of the in-cylinder pressure sensor 21 is abnormal, the value of the in-cylinder pressure P obtained from the output of the in-cylinder pressure sensor 21 is corrected based on the calculated abnormality determination parameter α. A correction amount is calculated. Since the calculated value of the abnormality determination parameter α is an index value indicating the sensitivity deviation amount of the in-cylinder pressure sensor 21, a correction amount can be set based on the value of the abnormality determination parameter α. By correcting the in-cylinder pressure using this correction amount, an accurate in-cylinder pressure can be detected even in the case of an abnormal in-cylinder pressure sensor 21, and various controls such as ignition timing control based on the in-cylinder pressure can be performed. It will be possible to execute and continue without problems.

  Steps S301 to S310 are the same as steps S101 to S110 of the first embodiment shown in FIG. After it is determined in step S310 that the in-cylinder pressure sensor 21 is abnormal, in step S311, the correction coefficient K as the correction amount is calculated. Specifically, the reciprocal of the abnormality determination parameter α is obtained and used as the correction coefficient K. That is, K = 1 / α. This terminates the current routine.

  When the correction coefficient K is calculated in this way, in the following various controls, the in-cylinder pressure P ′ converted from the output voltage E of the in-cylinder pressure sensor 21 is multiplied by the correction coefficient K to obtain a corrected in-cylinder pressure P ′ (P ′ = KP), various controls are performed using the corrected cylinder pressure P ′. As a result, the final output of the in-cylinder pressure sensor 21 is corrected in sensitivity to indicate an accurate in-cylinder pressure, and control based on the in-cylinder pressure can be performed without any trouble.

  Next, another embodiment will be described.

  FIG. 7 shows a schematic view of an internal combustion engine according to another embodiment. As shown in the figure, the configuration of the internal combustion engine 1 is substantially the same as the configuration shown in FIG. 1, and the same components are denoted by the same reference numerals. The main difference is that the internal combustion engine 1 is a so-called bi-fuel engine that can be operated even with a fuel containing alcohol fuel (for example, ethanol), and an alcohol concentration sensor 24 for detecting the alcohol concentration of the fuel is provided. That is.

  The internal combustion engine 1 can be operated with only gasoline fuel, only alcohol fuel, or a mixed fuel of gasoline fuel and alcohol fuel. An alcohol concentration sensor 24 is provided to execute optimal ignition timing control and fuel injection control according to the alcohol concentration of the fuel. The alcohol concentration sensor 24 is provided in the fuel pipe 23 immediately before the delivery pipe 22 in this embodiment, but the installation position is arbitrary.

By the way, when the fuel includes alcohol fuel, the lower heating value q _fuel changes according to the alcohol concentration of the _fuel . Therefore, in the present embodiment, the ECU 20 sets the lower heating value q _fuel based on the alcohol concentration detected by the alcohol concentration sensor 24 using a predetermined map or function stored in advance. By doing so, the abnormality diagnosis process of the embodiment can be performed without any trouble even in the bi-fuel engine.

Specifically, when the abnormality diagnosis process shown in FIG. 4, FIG. 5 or FIG. 6 is executed, a value set based on the detected alcohol concentration is used as the lower heating value q _fuel . Here, the lower the lower calorific value q _fuel is set as the detected alcohol concentration is higher.

By the way, immediately after the fuel alcohol concentration is changed, such as immediately after fuel supply, the alcohol concentration value detected by the alcohol concentration sensor 24 and the alcohol concentration value of the fuel actually injected from the injector 12 are different. There is a time difference based on transport delay. During this time difference, the lower heating value q _Fuel that has been set based on the detected alcohol concentration, actually is different from the lower heating value q _Fuel of the injected fuel, possible erroneous diagnosis when abnormality diagnosis by using a former There is sex.

  Therefore, in this embodiment, abnormality diagnosis is prohibited during this time difference. As a result, erroneous diagnosis can be prevented and diagnostic accuracy can be improved.

  FIG. 8 shows a procedure of abnormality diagnosis prohibition processing executed by the ECU 20. First, in step S401, it is determined whether or not the change amount ΔC of the alcohol concentration C detected by the alcohol concentration sensor 24 per predetermined time Δt, that is, ΔC / Δt is larger than a predetermined value γ. In the case of ΔC / Δt ≦ γ, it is considered that the alcohol concentration C has not substantially changed, and a standby state is entered. On the other hand, if ΔC / Δt> γ, it is considered that the alcohol concentration C has substantially changed, and the process proceeds to step S402.

  In step S402, the values of the fuel passage volume ν, the engine speed Ne, and the fuel injection amount integrated value Στ in the predetermined section are acquired. As shown in FIG. 7, the fuel passage volume ν in the predetermined section is a total value of the volume of the fuel pipe 23 between the alcohol concentration sensor 24 and the delivery pipe 22 and the volume of the delivery pipe 22. The value is stored in the ECU 20. The engine rotational speed Ne is a value calculated by the ECU 20 based on the value detected by the crank angle sensor 16. The fuel injection amount integrated value Στ is an integrated value of the fuel injection amount τ injected during a predetermined unit time, and is calculated by the ECU 20. Specifically, the ECU 20 integrates the fuel injection amount τ from the start of execution of step S402 to the unit time before to obtain a fuel injection amount integrated value Στ.

  Next, in step S403, a fuel transportation delay time T is calculated. The fuel transport delay time T is a time corresponding to a time difference until the fuel detected by the alcohol concentration sensor 24 reaches the injectors 12 of all cylinders evenly. The ECU 20 first multiplies the engine rotational speed Ne acquired in step S402 and the fuel injection amount integrated value Στ to calculate the fuel consumption amount S = Ne · Στ per unit time. Based on the fuel consumption amount S per unit time and the fuel passage volume ν in the predetermined section acquired in step S402, the fuel transport delay time T is calculated according to a predetermined map or function.

  The time difference based on the transport delay is a value related to the fuel passage volume ν in the predetermined section and the fuel consumption S per unit time. Therefore, by setting the fuel transport delay time T as a predetermined time based on the fuel passage volume ν and the fuel consumption S, erroneous diagnosis can be reliably prevented while minimizing the diagnosis prohibition time and the diagnosis frequency reduction.

  Next, in step S404, it is determined whether or not the fuel transport delay time T has elapsed since ΔC / Δt> γ was established in step S401. When the fuel transportation delay time T has not elapsed, the process proceeds to step S405, and abnormality diagnosis of the in-cylinder pressure sensor is prohibited. On the other hand, if the fuel transportation delay time T has elapsed, the process proceeds to step S406, where abnormality diagnosis of the in-cylinder pressure sensor is permitted.

  Thus, when the change amount ΔC / Δt of the detected alcohol concentration per predetermined time is larger than the predetermined value γ, the abnormality diagnosis of the in-cylinder pressure sensor is prohibited for the predetermined time T, thereby preventing the erroneous diagnosis immediately after the change in the alcohol concentration of the fuel. can do.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable. For example, the internal combustion engine 1 described above is a spark ignition type internal combustion engine (gasoline engine), but is not limited thereto, and the present invention can also be applied to a compression ignition type internal combustion engine (diesel engine). Further, the alcohol concentration detection means is not limited to the alcohol concentration sensor, but may be one that indirectly detects or estimates the alcohol concentration based on other information.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 is a schematic view of an internal combustion engine according to an embodiment of the present invention. It is a graph which shows the output characteristic of a cylinder pressure sensor. It is a graph which shows the relationship between the cylinder pressure P at the time of one combustion in a specific cylinder, the heat generation amount Q, and the cylinder pressure parameter ^PVκ . It is a flowchart which shows 1st Example of an abnormality diagnosis process. It is a flowchart which shows 2nd Example of abnormality diagnosis processing. It is a flowchart which shows 3rd Example of an abnormality diagnosis process. It is the schematic of the internal combustion engine which concerns on other embodiment of this invention. It is a flowchart which shows the procedure of the abnormality diagnosis prohibition process which concerns on other embodiment.

Explanation of symbols

1 Internal combustion engine 3 Combustion chamber 5 Air flow meter 6 Exhaust pipe 10 Throttle valve 11 Catalyst 12 Injector 14 Exhaust manifold 17 Pre-catalyst sensor 20 Electronic control unit (ECU)
21 In-cylinder pressure sensor 22 Delivery pipe 23 Fuel pipe K Correction factor C Alcohol concentration

Claims (7)

An apparatus for diagnosing an abnormality of an in-cylinder pressure sensor for detecting an in-cylinder pressure of an internal combustion engine,
By normalizing the total heat generation parameter ΔPV ^κ correlated with the total heat generation amount generated by one combustion of the internal combustion engine by the fuel amount τ used for the one combustion, low heat generation of the fuel Combustion parameter calculation means for calculating a combustion parameter H corresponding to the quantity q _fuel ;
In-cylinder pressure, comprising: a determination unit that determines whether the in-cylinder pressure sensor is normal or abnormal based on the combustion parameter H calculated by the combustion parameter calculation unit and the lower heating value q _{fuel of the fuel.} Sensor abnormality diagnosis device.
However, [Delta] PV [ ^kappa] = P ([theta] ₂ ) V ([theta] ₂ ) [ ^kappa] -P ([theta] ₁ ) V ([theta] ₁ ) [ ^kappa] , P ([theta] ₁ ), P ([theta] ₂ ) are predetermined values before and after the start of combustion. In-cylinder pressure detected by the in-cylinder pressure sensor at crank angles θ ₁ and θ ₂ , V (θ ₁ ) and V (θ ₂ ) are in-cylinder volumes at the crank angles θ ₁ and θ ₂ , and κ is a predetermined specific heat. ratio. The in-cylinder pressure sensor abnormality diagnosis apparatus according to claim 1, wherein the combustion parameter H is calculated by dividing the total heat generation amount parameter ΔPV ^κ by the fuel amount τ. The determination means calculates the abnormality determination parameter α by dividing the combustion parameter H by the lower heating value q _fuel and determines whether the abnormality determination parameter α is within a predetermined range near 1. The in-cylinder pressure sensor abnormality diagnosis device according to claim 1, wherein the in-cylinder pressure sensor determines whether the in-cylinder pressure sensor is normal or abnormal. Correction amount calculation for calculating a correction amount for correcting the value of the in-cylinder pressure obtained from the output of the in-cylinder pressure sensor based on the abnormality determination parameter α when the in-cylinder pressure sensor is determined to be abnormal by the determination unit. The in-cylinder pressure sensor abnormality diagnosis device according to any one of claims 1 to 3, further comprising means. It further comprises alcohol concentration detection means for detecting the alcohol concentration of the _fuel, and low heat value setting means for setting the low heat value q _fuel based on the alcohol concentration detected by the alcohol concentration detection means. The abnormality diagnosis device for an in-cylinder pressure sensor according to any one of claims 1 to 4.   2. The apparatus according to claim 1, further comprising diagnosis prohibiting means for prohibiting abnormality diagnosis of the in-cylinder pressure sensor for a predetermined time when a change amount of the alcohol concentration detected by the alcohol concentration detecting means per predetermined time is larger than a predetermined value. 5. The abnormality diagnosis device for an in-cylinder pressure sensor according to 5. The abnormality diagnosis device for an in-cylinder pressure sensor according to claim 6, wherein the diagnosis prohibition unit sets the predetermined time based on a fuel passage volume in a predetermined section and a fuel consumption per unit time.

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