JP5381755B2 - In-cylinder pressure sensor output correction device - Google Patents

Description

  The present invention relates to an output correction device for an in-cylinder pressure sensor. More specifically, the present invention is suitable as an output correction device for correcting the output of an in-cylinder pressure sensor installed in each cylinder of an internal combustion engine.

  Conventionally, a method has been studied in which an in-cylinder pressure sensor is installed in each of a plurality of cylinders of an internal combustion engine and the in-cylinder pressure is detected according to the output of the in-cylinder pressure sensor. However, the output of the in-cylinder pressure sensor may change due to an external factor such as a temperature change or an error in sensitivity due to deterioration over time, and an appropriate output may not be obtained.

  Patent Literature 1 discloses a calibration device for an in-cylinder pressure sensor that corrects the output of the in-cylinder pressure sensor. In the technique of Patent Document 1, the in-cylinder pressure is detected for each cylinder according to the output of the in-cylinder pressure sensor at two different points (predetermined fixed positions) during the compression stroke before combustion. Find the differential pressure in the cylinder. In the technique of Patent Document 1, it is assumed that the calculated differential pressure is essentially the same for all cylinders, and the ratio of the differential pressure of the cylinders other than the reference cylinder to the differential pressure of the reference cylinder is obtained, and this is used as the in-cylinder pressure sensor. It is used as a sensitivity correction value.

JP 2008-025404 A

  When the differential pressure at the same two crank angles is taken for each cylinder as in Patent Document 1, in order for the differential pressure to be the same for all cylinders, the intake air amount for each cylinder must be the same. Is the premise. In other words, when the intake air amount is different for each cylinder, it cannot be said that the differential pressure at two points in the compression stroke is constant among all the cylinders.

  Therefore, in Patent Document 1, if the intake air amount varies when the in-cylinder pressure is detected, the difference between the calculated differential pressures among the cylinders may be attributed to variations in the intake air amount and the sensitivity of the in-cylinder pressure sensor. The thing which originates in is mixed, and these cannot be classified. For this reason, the correction value calculated in Patent Document 1 is influenced by the variation in the intake air amount when detecting the in-cylinder pressure, and may not correct the sensitivity error of the in-cylinder pressure sensor appropriately.

  An object of the present invention is to solve the above-described problems, and an improved output of an in-cylinder pressure sensor that can more accurately correct an error caused by the sensitivity of the in-cylinder pressure sensor even when the intake air amount varies. A correction apparatus is provided.

前記第１補正値と、前記筒内圧センサに感度誤差がない場合に検出されるべき筒内圧の値を用いて設定され、予め記憶された基準補正値との比に基づいて、前記筒内圧センサの出力の感度を補正する第２補正値を算出する第２補正値算出手段と、
前記第２補正値に応じて、前記筒内圧センサの出力を補正する出力補正手段と、
を備える。 In order to achieve the above object, a first invention is an output correction device for correcting an output of an in-cylinder pressure sensor installed in each of a plurality of cylinders of an internal combustion engine,
A first in-cylinder pressure detecting means for detecting a first in-cylinder pressure P1 in response to an output of an in-cylinder pressure sensor of the cylinder at a first crank angle during a compression stroke before combustion in any cylinder of the internal combustion engine; ,
Second in-cylinder pressure detection for detecting a second in-cylinder pressure P2 in response to an output of the in-cylinder pressure sensor at a second crank angle different from the first crank angle during the same compression stroke as the compression stroke. Means,
When the volume at the first crank angle of the combustion chamber of the cylinder is the first volume V1, the volume at the second crank angle is the second volume V2, and the specific heat ratio is κ, First correction value calculating means for calculating a correction value;

The in-cylinder pressure sensor is set based on a ratio between the first correction value and a reference correction value stored in advance , which is set using a value of the in-cylinder pressure to be detected when the in- cylinder pressure sensor has no sensitivity error. Second correction value calculating means for calculating a second correction value for correcting the sensitivity of the output;
Output correction means for correcting the output of the in-cylinder pressure sensor according to the second correction value;
Is provided.

According to a second invention, in the first invention,
Operating state determining means for determining whether or not the internal combustion engine is operating in a fuel cut operating state;
When it is determined that the fuel cut operation state is established, the first in-cylinder pressure detecting unit and the second in-cylinder pressure detecting unit detect the first in-cylinder pressure P1 and the second in-cylinder pressure P2.

According to a third invention, in the first invention,
Offset correcting means for calculating a first corrected in-cylinder pressure P01 and a second corrected in-cylinder pressure P02 obtained by correcting respective output offsets of the first in-cylinder pressure P1 and the second in-cylinder pressure P2.
Specific heat ratio calculating means for calculating the specific heat ratio κ in Equation 1 according to Equation 2 is further provided.

  According to the first aspect of the invention, the second correction value for correcting the output sensitivity of the in-cylinder pressure sensor can be calculated according to the first correction value calculated according to Formula 1. Here, the first correction value obtained according to Equation 1 is a value that varies depending on, for example, temperature drift and sensor output sensitivity, but is not affected by variations in the intake air amount. Accordingly, the sensitivity error of the in-cylinder pressure sensor can be corrected more accurately without being affected by the variation in the intake air amount.

  According to the second invention, the detection of the first and second in-cylinder pressures for calculating the correction value is executed in the fuel cut operation state. Therefore, since the first and second correction values can be calculated according to the in-cylinder pressure under an environment where the specific heat ratio κ is constant, the sensitivity correction of the in-cylinder pressure sensor can be performed more accurately.

  According to the third invention, the specific heat ratio κ in Formula 1 can be calculated. Therefore, for example, the correction value can be calculated without waiting for an environment where the fuel cut operation continues for a relatively long time. Therefore, it is possible to secure a sufficient opportunity for detecting the sensitivity correction value, and to correct the sensitivity error of the in-cylinder pressure sensor more reliably.

It is a schematic diagram for demonstrating the structure of the whole system of Embodiment 1 of this invention. It is a figure for demonstrating correction | amendment of the offset error of the cylinder pressure sensor in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 1 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram for explaining the configuration of the entire system according to the first embodiment of the present invention. In the system shown in FIG. 1, the internal combustion engine is a multi-cylinder internal combustion engine having a plurality of cylinders 2, but only one cylinder 2 is shown in FIG.

  A piston 4 is installed in each cylinder 2. A combustion chamber 6 is formed on the upper surface of the piston 4 in the cylinder 2. For each cylinder 2, a fuel injection valve 8, a spark plug 10, and an in-cylinder pressure sensor 12 are installed in the cylinder head. The in-cylinder pressure sensor 12 generates an output corresponding to the pressure in the combustion chamber 6 (in-cylinder pressure). A crank angle sensor 14 that generates an output corresponding to the crank angle of the internal combustion engine is installed in the vicinity of the crankshaft (not shown).

  This system includes a control device 20. The in-cylinder pressure sensor 12 and the crank angle sensor 14 are electrically connected to the control device 20, and outputs from these sensors are input. The control device 20 calculates the in-cylinder pressure of each cylinder 2, the current position of the piston 4 and the like according to these outputs. On the other hand, the fuel injection valve 8 and the spark plug 10 are electrically connected to the control device 20. The control device 20 controls the fuel injection amount, the ignition timing, and the like by issuing control signals to them.

  FIG. 2 is a diagram for explaining the detected value of the in-cylinder pressure corresponding to the output of the in-cylinder pressure sensor 12 in the compression stroke and the corrected in-cylinder pressure. In FIG. 2, the horizontal axis represents time (or crank angle), and the vertical axis represents in-cylinder pressure. In FIG. 2, the solid line (a) represents the corrected in-cylinder pressure, and the broken line (b) represents the corrected in-cylinder pressure.

The in-cylinder pressure obtained according to the output of the in-cylinder pressure sensor 12 may cause an offset error due to a temperature change of the in-cylinder pressure sensor 12 or a sensitivity error due to output sensitivity (gain). Here, if the uncorrected in-cylinder pressure obtained from the output of the in-cylinder pressure sensor 12 is P, the in-cylinder pressure Pt after correcting these errors can be expressed by the following Equation 3.

In Equation 3, dP is an offset error correction value (first correction value). As a method for correcting this offset error, a method is known in which an in-cylinder pressure sensor 12 adds an offset correction value dP calculated by the following formula 4 (same as formula 1) to the in-cylinder pressure calculated from the output (broken line (b)). It has been.

  In Formula 4, P1 is the in-cylinder pressure before correction (first in-cylinder pressure) obtained from the output of the in-cylinder pressure sensor 12 at the first crank angle during the compression stroke before combustion of a certain cylinder, and P2 is the same. This is the in-cylinder pressure before correction (second in-cylinder pressure) obtained from the output of the in-cylinder pressure sensor 12 at a second crank angle different from the first crank angle during the compression stroke before combustion. V1 and V2 are the volume (first volume) of the combustion chamber 6 at the first crank angle and the volume (second volume) of the combustion chamber 6 at the second crank angle, respectively. κ is a specific heat ratio, which is a fixed value in the first embodiment.

Equation 4 can be obtained using Poisson's law PV ^κ = constant as follows. First, when the first in-cylinder pressure P1 and the second in-cylinder pressure P2 calculated from the output of the in-cylinder pressure sensor 12 are corrected using the offset error correction value dP, the in-cylinder pressures are (P1 + dP) and (P2 + dP), respectively. Become. Here, since the first in-cylinder pressure and the second in-cylinder pressure are respectively the in-cylinder pressures in the compression stroke before the combustion, the relationship of Formula 5 is established from Poisson's law. From Equation 5, a calculation formula (Formula 4) for the correction value dP is obtained.

When it is considered that the cylinder pressure sensor 12 has a sensitivity error that is α times, the correction value dP calculated using the uncorrected cylinder pressures P1 and P2 calculated from the output of the cylinder pressure sensor 12 is expressed by the following formula. As shown in FIG. 6, the correct correction value (hereinafter referred to as “reference correction value”) dP0 calculated using the in-cylinder pressures P01 and P02 when there is no sensitivity error (or is corrected correctly) is α times.

Here, the sensitivity correction coefficient K (second correction value) for correcting the sensor sensitivity error α is an inverse number of the sensitivity error α. Therefore, the sensitivity correction coefficient K can be calculated by Equation 7.

  In the first embodiment, the detection of the in-cylinder pressures P1 and P2 and the calculation of the correction value dP according to Equation 3 are repeated a plurality of times to calculate the average value (average correction value) dPA of the correction value dP. The reference correction value dP0 is a value corresponding to the characteristics of the in-cylinder pressure sensor 12, and is obtained in advance by experiments or the like and stored in the control device 20. In this first embodiment, the sensitivity correction coefficient K is calculated by substituting the calculated average correction value dPA and the reference correction value dP0 into Equation 7, and the sensitivity error of the in-cylinder pressure sensor 12 is corrected using this. .

The detection of the in-cylinder pressures P1 and P2 for calculating the sensitivity correction coefficient K is performed under the following environment.
(1) The internal combustion engine is sufficiently warmed up and the water temperature is stable.
When the internal combustion engine is not warmed up, a temperature change occurs in each part of the in-cylinder pressure sensor 12. When the temperature of each part of the in-cylinder pressure sensor 12 changes, the thermal expansion of each part of the in-cylinder pressure sensor 12 affects, and the stress applied to the in-cylinder pressure detection unit changes. As a result, the offset amount varies. Accordingly, in order to perform detection in a state where the temperature of the in-cylinder pressure sensor 12 is maintained within a certain range, detection is performed in a state where the warm-up of the internal combustion engine is completed and the water temperature is stable.

(2) The internal combustion engine is in a fuel cut operation, and a certain cycle has elapsed after the start of the fuel cut operation.
In the calculation of the correction value dP of Equation 4 above, the specific heat ratio κ is used as a fixed value. However, for example, when the air-fuel ratio is different for each cylinder or when the EGR rate is different, the specific heat ratio κ may be changed. When the specific heat ratio κ is different from the fixed value, an error occurs in the correction value dP calculated using the specific heat ratio κ and the sensitivity correction coefficient K. Accordingly, in order to detect the in-cylinder pressures P1 and P2 in an environment where the air-fuel ratio and the EGR rate are the same and there is no deviation in the specific heat ratio κ, a constant cycle in which the fuel cut operation is being performed and the residual gas is scavenged. The condition is detection after the passage.

  FIG. 3 is a flowchart for illustrating a control routine executed by the control device in the first embodiment of the present invention. In the routine of FIG. 3, it is first determined whether or not the water temperature of the internal combustion engine is stable (S12). When the stable state of the water temperature is not recognized, the current process ends.

  On the other hand, when the water temperature stability is recognized in step S12, it is determined whether or not the fuel cut is currently in operation (S14). If it is not recognized that the vehicle is in the fuel cut operation state, the current process ends.

  On the other hand, if it is determined in step S14 that the vehicle is in the fuel cut operation state, it is determined whether or not a predetermined number of cycles have elapsed since the fuel cut operation state was entered (S16). Here, the predetermined number of cycles is the number of cycles in which the residual gas remaining in the cylinder 2 is considered to be sufficiently scavenged after entering the fuel cut operation state, and is determined in advance by experiments or the like and stored in the control device 20. ing. If the passage of the predetermined number of cycles is not recognized in step S16, the current process ends.

  On the other hand, if the passage of the predetermined number of cycles is recognized in step S16, then the first in-cylinder pressure P1 at the first crank angle is detected (S18). Here, the first crank angle is a predetermined crank angle during the compression stroke before combustion, and is an angle set in advance and stored in the control device 20. The first in-cylinder pressure P1 is calculated in the control device 20 according to the output of the in-cylinder pressure sensor 12.

  Next, the second in-cylinder pressure P2 at the second crank angle is detected (S20). The second crank angle is a crank angle different from the first crank angle before combustion during the same compression stroke as the detection of the first in-cylinder pressure P1, and is an angle set in advance and stored in the control device 20. The first and second crank angles are set so as to increase the difference between the combustion chamber volumes V1 and V2. The second in-cylinder pressure P2 is calculated in the control device 20 in accordance with the output of the in-cylinder pressure sensor 12.

  Next, the current correction value dPi is calculated (S22). Here, the first volume V1 and the second volume V2, which are the volumes of the combustion chamber 6 corresponding to the first crank angle and the second crank angle, and the first in-cylinder pressure P1 and the second volume detected in steps S18 and S20, respectively. The current correction value dPi is calculated from the in-cylinder pressure P2 according to the above mathematical formula 4, and stored in the control device 20.

  Next, 1 is added to the counter i and stored in the control device 20. (S24). The counter i is zero at the initial value, and is a counter for counting the number of times the correction value dP has been calculated.

  Next, it is determined whether or not the counter i is greater than or equal to the reference number (S26). Here, the reference number is the number of times required to obtain the average correction value dPA, and is a fixed value that is preset and stored in the control device 20. In step S26, if the establishment of counter i ≧ reference number is not recognized, the current process ends as it is.

  On the other hand, if it is determined in step S26 that counter i ≧ reference number is established, an average correction value dPA is calculated (S28). The average correction value dPA is calculated by obtaining the average value of the correction values dPi (i = 1 to the reference number) stored in the control device 20.

  Next, a sensitivity correction coefficient K is calculated (S30). The sensitivity correction coefficient K is calculated according to Equation 7 based on the average correction value dPA calculated in step S28 and the reference correction value dP0 stored in advance in the control device 20, and is stored in the control device 20.

  Next, the counter i is set to zero (S32). Thereafter, the value of the correction value dPi (i = 1 to the reference number) is cleared (S34), and the current process ends.

  The corrected in-cylinder pressure Pt is calculated according to Equation 3 above, and the sensitivity correction coefficient K calculated in this routine is used. Although the above-described routine has been described for calculating the sensitivity correction coefficient K of one cylinder, this routine is executed for each cylinder, and the sensitivity correction coefficient K of the in-cylinder pressure sensor 12 for each cylinder is calculated. Accordingly, each output is corrected.

  As described above, according to the system of the first embodiment, the sensitivity correction coefficient K of the in-cylinder pressure sensor 12 can be obtained. Here, the offset correction value dP varies depending on the temperature drift of the in-cylinder pressure sensor 12 and the output sensitivity of the in-cylinder pressure sensor 12, but is not affected by variations in the intake air amount. Therefore, the sensitivity error of the in-cylinder pressure sensor 12 can be corrected with higher accuracy, and the in-cylinder pressure can be accurately grasped.

  Further, in the calculation of the sensitivity correction coefficient K, it is not necessary to change the control amount of the internal combustion engine even when the necessary in-cylinder pressures P1 and P2 are detected. Therefore, it is possible to suppress the influence on the emission and the like when calculating the sensitivity correction coefficient K.

  In the first embodiment, the in-cylinder pressure P1, in a state in which the internal combustion engine is warmed up and the water temperature is stable, in an operation state in the fuel cut, and after a certain cycle has elapsed after the fuel cut starts. The case where P2 is detected has been described. Under such an environment, variations in the output of the in-cylinder sensor due to temperature changes can be suppressed, and influences of variations in the air-fuel ratio and EGR rate can be suppressed, and the sensitivity correction coefficient K can be more accurately detected. This is because it can be calculated. However, the present invention is not limited to such timing, and correction values are calculated at other timings, for example, at two points in the compression stroke during normal operation where the air-fuel ratio and EGR rate are constant to some extent. It may be a thing.

  In the first embodiment, by executing step S18, the “first in-cylinder pressure detecting means” of the present invention is realized, and by executing step S20, the “second in-cylinder pressure detecting means” is realized. Then, the “first correction value calculating unit” is realized by executing step S22, and the “second correction value calculating unit” is realized by executing step S30. Further, the “operating state discriminating means” of the present invention is realized by executing step S14.

Embodiment 2. FIG.
The system of the second embodiment includes an intake pressure sensor and an exhaust pressure sensor (not shown) in addition to the system of FIG. The system of the second embodiment has the same function as the system of the first embodiment except that it has a function of calculating the specific heat ratio κ.

  In the second embodiment, as in the first embodiment, in-cylinder pressures P1 and P2 at different first and second crank angles during the compression stroke are detected. Here, the output offset of the in-cylinder pressure sensor 12 is corrected by matching the output of the in-cylinder pressure sensor during the intake stroke or the exhaust stroke with the output level of the intake pressure sensor or the exhaust pressure sensor at the same timing.

In the second embodiment, the specific heat ratio κ is calculated according to Equation 8 from the in-cylinder pressures Pt1 and Pt2 obtained in the offset-corrected state and the combustion chamber volumes V1 and V2 at that time.

  In the system of the second embodiment, the control device 20 first calculates the specific heat ratio κ according to the above equation 8, and then substitutes the specific heat ratio κ, the in-cylinder pressures P1 and P2, and the volumes V1 and V2 before offset correction into the equation 8. Thus, the correction value dP is calculated. Further, the correction value dP is substituted to calculate the sensitivity correction coefficient K.

By the way, the calculation of the specific heat ratio κ is executed before the calculation of the sensitivity correction coefficient K. Here, for example, in Expression 8, if the in-cylinder pressures P1 and P2 are values in which neither the offset error nor the sensitivity error is corrected, the corrected in-cylinder pressures use Pt01 = a · P1 + b and Pt02 = a · P2 + b. The specific heat ratio κ is expressed by the following formula 9.

However, when the in-cylinder pressures Pt1 and Pt2 in which the offset error is corrected are used, the in-cylinder pressures after the sensitivity error correction are Pt01 = a · Pt1 and Pt02 = a · Pt2. When this is used, the specific heat ratio κ is as shown in Equation 10 below.

  From Equation 10, it can be seen that even if the sensitivity is not corrected, the specific heat ratio κ can be calculated correctly if the offset correction value is corrected.

  Thus, in the system according to the second embodiment, the specific heat ratio κ can be calculated. Therefore, the correction value dP and the sensitivity correction coefficient K can be calculated more accurately even when the specific heat ratio κ is not an operating condition in which the specific heat ratio κ is constant. Therefore, for example, the sensitivity correction coefficient K can be accurately calculated in the normal operation state without waiting for the timing when the fuel cut operation state continues for a long time as in the first embodiment. Therefore, a sufficient opportunity for calculating the sensitivity correction coefficient K is obtained, and the in-cylinder pressure can be grasped more accurately.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 cylinder 4 piston 6 combustion chamber 8 fuel injection valve 10 spark plug 12 cylinder pressure sensor 14 crank angle sensor 20 controller dP correction value dP0 reference correction value K sensitivity correction coefficient P sensor output cylinder pressure Pt estimated cylinder pressure P1, P2 cylinder pressure (Sensor output)
V1, V2 Combustion chamber volume α Sensor sensitivity error κ Specific heat ratio

Claims (3)

An output correction device for correcting the output of an in-cylinder pressure sensor installed in each of a plurality of cylinders of an internal combustion engine,
A first in-cylinder pressure detecting means for detecting a first in-cylinder pressure P1 in response to an output of an in-cylinder pressure sensor of the cylinder at a first crank angle during a compression stroke before combustion in any cylinder of the internal combustion engine; ,
Second in-cylinder pressure detection for detecting a second in-cylinder pressure P2 in response to an output of the in-cylinder pressure sensor at a second crank angle different from the first crank angle during the same compression stroke as the compression stroke. Means,
When the volume at the first crank angle of the combustion chamber of the cylinder is the first volume V1, the volume at the second crank angle is the second volume V2, and the specific heat ratio is κ, First correction value calculating means for calculating a correction value;

The in-cylinder pressure sensor is set based on a ratio between the first correction value and a reference correction value stored in advance , which is set using a value of the in-cylinder pressure to be detected when the in- cylinder pressure sensor has no sensitivity error. Second correction value calculating means for calculating a second correction value for correcting the sensitivity of the output;
Output correction means for correcting the output of the in-cylinder pressure sensor according to the second correction value;
An output correction device for an in-cylinder pressure sensor. Operating state determining means for determining whether or not the internal combustion engine is operating in a fuel cut operating state;
When it is determined that the fuel cut operation state is established, the first in-cylinder pressure detecting means and the second in-cylinder pressure detecting means detect the first in-cylinder pressure P1 and the second in-cylinder pressure P2. The in-cylinder pressure sensor output correction device according to claim 1, wherein Offset correcting means for correcting the respective output offsets of the first in-cylinder pressure P1 and the second in-cylinder pressure P2 to calculate a first corrected in-cylinder pressure P01 and a second corrected in-cylinder pressure P02;
The output correction device for an in-cylinder pressure sensor according to claim 1, further comprising specific heat ratio calculation means for calculating the specific heat ratio κ in Formula 1 according to Formula 2.

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