JP2010190091A - In-cylinder pressure detecting device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect in-cylinder pressures while appropriately eliminating noise influences, using an in-cylinder pressure sensor provided in an internal combustion engine. <P>SOLUTION: An in-cylinder pressure detecting device 1 of an internal combustion engine includes a collection means for collecting data corresponding to output signals from an in-cylinder pressure sensor 56 provided in an internal combustion engine 10, an error determination value calculating means for calculating error determination values on the collected data, an error determination means for determining whether there are noise errors in the data, based on a result of comparison between the calculated error determination values and a predetermined threshold value, and an in-cylinder pressure calculating means, when it is determined that there are no noise error in the data, for calculating in-cylinder pressures based on the data concerned, and on the other hand, when it is determined that there are noise errors in the data, for calculating in-cylinder pressures without being based on the data concerned. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an in-cylinder pressure detection device for an internal combustion engine for detecting the in-cylinder pressure of the internal combustion engine.

  An in-cylinder pressure sensor can be used to detect the pressure in the combustion chamber of the cylinder of the internal combustion engine, that is, the in-cylinder pressure. Patent Document 1 discloses a combustion pressure sensor (corresponding to an in-cylinder pressure sensor) created to provide a high S / N combustion pressure sensor that is less affected by external electrical noise and the like. The combustion pressure sensor includes a load detection device that receives a load generated by the combustion pressure of the internal combustion engine and detects the combustion pressure. The load detection device includes a piezoelectric element that generates a charge corresponding to the load, and the piezoelectric element. And a conversion circuit that converts the generated charge into a voltage signal. Therefore, the electric charge generated by the piezoelectric element is not directly transmitted to the ECU, but is converted into a voltage signal by the conversion circuit mounted in the combustion pressure sensor, and then the voltage signal is transmitted to the ECU.

JP 2005-2909 A

  In general, the in-cylinder pressure sensor is disposed in the cylinder head. Therefore, the output signal from such an in-cylinder pressure sensor is affected by noise due to the seating of the intake / exhaust valve, and can also be affected by noise and electrical noise received by the wiring environment.

  However, in the prior art, since the output signal having a strong influence of noise is also used to obtain the in-cylinder pressure, the detection accuracy of the in-cylinder pressure is not always good.

  Accordingly, the present invention has been made in view of such a point, and an object thereof is to detect the in-cylinder pressure while appropriately eliminating the influence of noise using the in-cylinder pressure sensor provided in the internal combustion engine. is there.

  In order to achieve the above object, the present invention calculates a collecting means for collecting data corresponding to an output signal from an in-cylinder pressure sensor provided in an internal combustion engine, and an error determination value for the data collected by the collecting means. Error determination value calculating means for performing error determination means for determining whether or not there is a noise error in the data based on a comparison result between the error determination value calculated by the error determination value calculation means and a predetermined threshold value; When the error determining means determines that the data has no noise error, the cylinder pressure is calculated based on the data, and on the other hand, the error determining means determines that the data has a noise error. An in-cylinder pressure detecting device for an internal combustion engine comprising: an in-cylinder pressure calculating means for calculating an in-cylinder pressure without being based on the data.

1 is a schematic configuration diagram of an internal combustion engine to which an embodiment according to the present invention is applied. It is the graph showing the example of a change of cylinder pressure with respect to the crank angle. It is a flowchart concerning an embodiment. 3 is a graph conceptually showing voltage data with respect to a crank angle. FIG. 5 is a graph conceptually showing a gain by frequency analysis of the voltage data of FIG. 4 with respect to frequency. 5 is a graph conceptually showing a differential value of voltage data in FIG. 4 with respect to a crank angle.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an internal combustion engine 10 to which an in-cylinder pressure detection device (in-cylinder pressure detection device) 1 for an internal combustion engine according to an embodiment of the present invention is applied. The internal combustion engine 10 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 14 formed in a cylinder block 12 and reciprocating a piston 18 in the cylinder 16. It is. Although only one cylinder is shown in FIG. 1, the internal combustion engine 10 is preferably configured as a multi-cylinder engine, and the internal combustion engine 10 of the present embodiment is configured as a four-cylinder engine.

  An intake port facing each combustion chamber 14 is connected to an intake manifold 20. A surge tank 22 and an intake pipe 24 are sequentially connected to the upstream side of the intake manifold 20. The intake pipe 24 is connected to an air intake (not shown) via an air cleaner 26. A throttle valve (in this embodiment, an electronically controlled throttle valve) 28 is incorporated in the middle of the intake pipe 24 (between the surge tank 22 and the air cleaner 26). For example, each of the intake port, the intake manifold 20, and the intake pipe 24 defines a part of the intake passage 29.

  On the other hand, an exhaust port facing each combustion chamber 14 is connected to an exhaust manifold 30, and an exhaust pipe 32 is connected to the exhaust manifold 30 on the downstream side. Connected to the exhaust pipe 32 are a front-stage catalyst device 34 including a three-way catalyst and a rear-stage catalyst device 36 including a NOx storage reduction catalyst. For example, each of the exhaust port, the exhaust manifold 30, and the exhaust pipe 32 defines a part of the exhaust passage 37.

  In the cylinder head of the internal combustion engine 10, an intake valve Vi that opens and closes an intake port and an exhaust valve Ve that opens and closes an exhaust port are disposed for each combustion chamber 14. Each intake valve Vi and each exhaust valve Ve are opened and closed by a valve operating mechanism (not shown) having a variable valve timing and / or a variable lift function. Further, the internal combustion engine 10 has a number of spark plugs 40 corresponding to the number of cylinders, and the spark plugs 40 are disposed in the cylinder heads so as to face the corresponding combustion chambers 14.

  Further, as shown in FIG. 1, the internal combustion engine 10 includes an injector 42, and the injector 42 is disposed in the cylinder head so as to face the corresponding combustion chamber 14. In the internal combustion engine 10, fuel such as gasoline is directly injected from the injectors 42 toward the recesses 18 a of the pistons 18 in the combustion chambers 14 in a state where air is sucked into the combustion chambers 14. As a result, in the internal combustion engine 10, it is possible to form (stratify) an air-fuel mixture layer of fuel and air in the vicinity of the spark plug 40 in a state separated from the surrounding air layer. Can be used to perform stable stratified combustion.

  The throttle valve 28, each spark plug 40, each injector 42, and the valve mechanism are electrically connected to an ECU 50 that substantially functions as a control device for the internal combustion engine 10. The ECU 50 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. Various sensors are electrically connected to the ECU 50 via an A / D converter or the like, for example, an air flow meter 52 for detecting an intake air amount. The ECU 50 uses the various maps stored in the storage device and the throttle valve 28, the spark plug 40, the injector so that a desired output can be obtained based on detection values obtained using various sensors. 42, controls the valve mechanism and the like.

  As shown in FIG. 1, the sensors connected to the ECU 50 include a crank angle sensor 54. The crank angle sensor 54 is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and the like, and gives a pulse signal indicating the rotation angle of the crankshaft to the ECU 50 every minute time. In addition, the internal combustion engine 10 has in-cylinder pressure sensors 56 including semiconductor elements, piezoelectric elements, optical fiber detection elements, and the like corresponding to the number of cylinders. Each in-cylinder pressure sensor 56 is disposed in the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 14, and is electrically connected to the ECU 50. Each in-cylinder pressure sensor 56 outputs an electric signal corresponding to the pressure in the combustion chamber 14 of the cylinder 16, that is, the in-cylinder pressure. The output signal from each in-cylinder pressure sensor 56 is digitized, associated with the crank angle, and stored and held in a predetermined storage area (buffer) of the ECU 50 by a predetermined amount. Further, an intake pressure sensor 58 is provided for detecting the intake pressure in the intake passage. Here, the intake pressure sensor 58 is provided in the surge tank 22.

  While the internal combustion engine 10 is in operation, the in-cylinder pressure according to the embodiment is detected using the in-cylinder pressure sensor 56, and the detected in-cylinder pressure is used to control the internal combustion engine 10. The detection of the in-cylinder pressure according to the embodiment will be described below.

  Here, the collecting means for collecting the data corresponding to the output signal from the in-cylinder pressure sensor 56 which is the in-cylinder pressure detection unit, here the voltage data, is configured to include a part of the ECU 50. Further, the error determination value calculation means for calculating the error determination value for the collected data includes a part of the ECU 50. Further, the error determination means for determining whether or not there is a noise error in the data based on a comparison result between the error determination value and a predetermined threshold value includes a part of the ECU 50. Further, the in-cylinder pressure calculation means for calculating the in-cylinder pressure based on the determination result by the error determination means includes a part of the ECU 50.

  FIG. 2 shows an example of a change in the in-cylinder pressure obtained by performing general correction, for example, absolute pressure correction, on the signal output from the in-cylinder pressure sensor 56 (in-cylinder pressure signal) with respect to the crank angle. It is the graph which expressed. Since the internal combustion engine 10 has four cylinders and is a four-cycle engine, in the graph of FIG. 2, one scale on the horizontal axis corresponds to 180 ° crank angle, and four cylinders have fourteenths. The line is shown. In the example shown in FIG. 2, misfire occurs in one cylinder 16.

  The in-cylinder pressures A and B in FIG. 2 are pressures at which the in-cylinder pressure changes appropriately and can be regarded as normal values. However, the in-cylinder pressure C is an in-cylinder pressure in the middle of the compression stroke, but is an in-cylinder pressure detected by being strongly affected by noise. The in-cylinder pressure detected by being strongly influenced by such noise does not appropriately reflect the state in the cylinder 16. Therefore, it is not desirable to control the internal combustion engine 10 using such in-cylinder pressure. Therefore, in order not to use such an inappropriate in-cylinder pressure for the control of the internal combustion engine 10, here, it is excluded to detect the in-cylinder pressure based on the in-cylinder pressure signal that is strongly influenced by noise.

  Here, a method (in-cylinder pressure detection method of the internal combustion engine 10) for detecting the in-cylinder pressure without being based on the in-cylinder pressure signal that is strongly influenced by noise, that is, data corresponding to the in-cylinder pressure signal is based on the flowchart of FIG. explain. The routine of FIG. 3 is repeated every predetermined time, here every combustion cycle. However, in the present embodiment, the routine of FIG. 3 is started after the second predetermined time has elapsed since the internal combustion engine 10 was started. The second predetermined time can be arbitrarily determined, but may be zero, for example, but here is a time for which the combustion cycle is repeated 100 times. This is to wait until the combustion state of the internal combustion engine 10 is stabilized to some extent.

  The method described below based on the flowchart of FIG. 3 is a method for detecting the in-cylinder pressure in the in-cylinder pressure detection device 1 according to the embodiment of the present invention, and is an example of the present invention. As will be described in detail below, first, data corresponding to an output signal from the in-cylinder pressure sensor 56 is collected. Next, noise analysis is performed on the collected data based on frequency, voltage change rate, and maximum voltage, and an error determination value for the data is calculated. Then, using the error determination value, it is determined whether or not there is a noise error in the data. As a result of the determination, if it is determined that there is no noise error in the data, the in-cylinder pressure is calculated based on the data. On the other hand, if it is determined that there is a noise error in the data, the in-cylinder pressure is calculated without using the data (not based on the data) (the in-cylinder pressure is calculated based on data other than the data). .

First, in step S301, the ECU 50 receives an output signal (here, a voltage signal) from the in-cylinder pressure sensor 56, and collects data (here, voltage data) V corresponding thereto. This data here is a numerical value of the output signal itself. An example of the collected voltage data V is conceptually shown in FIG. 4 with respect to the crank angle θ. Here, from the time when the intake valve Vi is closed (the crank angle at this time is θ _IVC ) to the time when the exhaust valve Ve is opened (the crank angle at this time is θ _EVO ) in one combustion cycle. Voltage data V (θ) is collected. However, when step S301 is reached for the first time after the internal combustion engine 10 is started, a plurality of voltage data for a plurality of combustion cycles, that is, 101 voltage data V (θ) for 101 combustion cycles are collected. The voltage data V (θ) in the 101st combustion cycle is the target of in-cylinder pressure detection in the routine. Note that the collected in-cylinder pressure data may be data amplified through an amplifier. When an amplifier is provided, the amplifier may be provided in the ECU 50 or may be interposed between the ECU 50 and the in-cylinder pressure sensor 56. An amplifier may not be provided.

Next, in step S303, Fourier transform L is performed on the voltage data V (θ) collected in step S301, and a gain G (f) for each frequency f is calculated. FIG. 5 conceptually shows an example of the gain G (f) (“G” in FIG. 5) obtained by converting the voltage data V (θ) into the frequency domain by Fourier transform with respect to the frequency f. In FIG. 5, not only the gain G (f) but also the curves of the allowable upper limit variation Gu and the average gain Gave (f) (“Gave” in FIG. 5) are represented by dotted lines. The allowable upper limit variation Gu defines an upper limit allowable limit of variation due to the influence of noise of the gain G (f). Specifically, the allowable upper limit variation Gu is a value obtained by adding an allowable amount ε _G to the average gain Gave (f). However, the average gain Gave (f) is calculated with respect to the voltage data V of each of a plurality of the latest combustion cycles here, that is, 100 combustion cycles before the combustion cycle targeted in this routine. The average value of the gain G (f). Therefore, 101 data corresponding to the in-cylinder pressure signal for 101 combustion cycles is collected when the first time is reached after starting the internal combustion engine 10 in step S301 as described above. Thereafter, every time the cycle is repeated, the data of the latest 100 cycles are updated, and the average gain Gave (f) is calculated. Further, the allowable amount ε _G is a standard deviation σg of a plurality of gains G (f) of a plurality of most recent combustion cycles, or twice (2σg), 3 times (3σg) of this standard deviation, and so on. Here, the value is three times the standard deviation σg. The standard deviation σg is specifically calculated for 100 gains G (f) for the 100 most recent combustion cycles. The allowable amount ε _G may be a constant.

Next, in step S305, the voltage data V (θ) collected in step S301 is differentiated by θ, and a differential value V ′ (θ) as a voltage change rate is calculated. An example of the differential value V ′ (θ) thus obtained (“V ′” in FIG. 6) is conceptually shown in FIG. 6 with respect to the crank angle θ. In FIG. 6, not only the differential value V ′ (θ) but also the curves of the allowable upper limit variation V′u and the allowable lower limit variation V′d, and the curve of the average differential value V′ave (θ) are represented by dotted lines. Has been. The allowable upper limit variation V′u defines the upper limit allowable limit of variation due to the influence of noise of the differential value V ′ (θ), and the allowable lower limit variation V′d is the variation of noise due to the effect of noise of the differential value V ′ (θ). Define the lower tolerance limit. Specifically, the allowable upper limit variation V′u is a value obtained by adding the allowable amount ε _v to the average differential value V′ave (θ), while the allowable lower limit variation V′d is the average differential value V′ave. This is a value obtained by subtracting the allowable amount ε _v from (θ). However, the average differential value V′ave (θ) is 100 differential values V ′ (θ) with respect to the most recent, here 100, combustion cycles before the combustion cycle targeted in this routine. Is the average value. Further, the allowable amount ε _v is a standard deviation σv of a plurality of differential values V ′ (θ) of a plurality of latest combustion cycles, or twice (2σv), 3 times (3σv) of this standard deviation,. Here, it is set to 3 times the standard deviation σv. The standard deviation σv is calculated with respect to 100 differential values V ′ (θ) for 100 most recent combustion cycles. The allowable amount ε _v may be a constant.

Next, in step S307, the maximum value (maximum voltage) Vmax is obtained (calculated) from the voltage data V (θ) collected in step S301. The allowable upper limit variation Vmu and the allowable lower limit variation Vmd are also determined for the maximum value Vmax thus determined. The allowable upper limit variation Vmu determines the upper limit allowable limit of variation due to the influence of noise of the maximum value Vmax, and the allowable lower limit variation Vmd determines the lower limit allowable limit of variation due to the influence of noise of the maximum value Vmax. Specifically, the allowable upper limit variation Vmu is a value obtained by adding the allowable amount ε _m to the average maximum value Vmave, and the allowable lower limit variation Vmd is a value obtained by subtracting the allowable amount ε _m from the average maximum value Vmave. is there. However, the average maximum value Vmave is an average value of 100 maximum values Vmax with respect to the most recent, here 100, combustion cycles before the combustion cycle targeted in this routine. Further, the allowable amount ε _m may be a standard deviation σm of a plurality of maximum values Vmax of a plurality of most recent combustion cycles, or twice (2σm) or 3 times (3σm) of the standard deviation. It is set to 3 times σm. The standard deviation σm is calculated with respect to 100 maximum values Vmax for 100 most recent combustion cycles. The allowable amount ε _m may be a constant.

  In step S309, the error determination value Derr is calculated by substituting the various values calculated in the above step of the routine into the following equation (1).

The first term of the equation (1) is for performing noise analysis by frequency on the voltage data V targeted in the routine, and operations are performed on various frequencies f, and the maximum of them is calculated. The value obtained by raising the value to the power n is the solution of the first term. The second term of the equation (1) is for performing noise analysis based on the voltage change rate for the voltage data V targeted in the routine, and operations are performed on various crank angles θ. A value obtained by raising the maximum value of the absolute values to the nth power is taken as the solution of the second term. Further, the third term of the equation (1) is for performing noise analysis with the maximum voltage on the voltage data V targeted in the routine, and the absolute value thereof is the solution of the third term. N is a positive integer, preferably a positive even number, and is a large number such as 20, for example. Here, n is 20. This is because the degree to which each of the gain G (f), the differential value V ′ (θ), and the maximum value Vmax exceeds the above-described various allowable limits is more strictly reflected in the error determination value Derr.

  In step S311, the error determination value Derr calculated in step S309 is compared with a constant “3” as a predetermined threshold value. This “3” is attributed to the fact that there are three terms in the above equation (1).

  If a negative determination is made in step S311 that the error determination value Derr is less than or equal to a predetermined threshold, the process proceeds to step S313. Then, it is assumed that the voltage data V subject to the routine has little or no influence of noise, that is, the voltage data V has no noise error (the influence of noise that can be recognized as an error). Based on V, the actual in-cylinder pressure (actual in-cylinder pressure) is calculated.

  On the other hand, if an affirmative determination is made in step S311 that the error determination value Derr is greater than the predetermined threshold, the process proceeds to step S315. Then, it is assumed that the voltage data V to be subjected to the routine is strongly affected by noise, that is, the voltage data V has a noise error, and the voltage data V is not used (not based). Using the voltage data V in the most recent combustion cycle, the actual in-cylinder pressure is estimated, that is, the estimated in-cylinder pressure is calculated. The estimation of the in-cylinder pressure here is performed using various calculation methods such as extrapolation.

  In this way, the routine is completed through step S313 or step S315. Then, the process proceeds to step S301 of the next routine.

  In this way, the in-cylinder pressure can be appropriately detected using the in-cylinder pressure sensor 56 while appropriately eliminating the influence of noise. Therefore, the detected in-cylinder pressure is a pressure that appropriately reflects the pressure state in the cylinder 16 of the internal combustion engine 10, and is a in-cylinder pressure with high detection accuracy. Therefore, the internal cylinder engine 10 can be appropriately operated by using the detected in-cylinder pressure for various controls of the internal combustion engine 10 such as knock detection control and ignition (timing) control.

  As described above, the present invention has been described based on the above-described embodiment and its modifications. However, the aspect of the above-described embodiment according to the present invention may be partially or entirely as long as no contradiction arises. It is possible to combine them. For example, in the above-described embodiment, the noise analysis of the voltage data V is performed using three of the gain G (f), the differential value V ′ (θ), and the maximum value Vmax. Any one or any two may be used. Further, the voltage data V may be analyzed using values other than these calculated based on the voltage data V. However, the predetermined threshold value can be changed according to the number of calculated values used for the analysis of the voltage data V. For example, when only the gain G (f) and the differential value V ′ (θ) are used for the analysis of the voltage data V, and the above equation (1) is expressed as the sum of the first term and the second term, The threshold is preferably set to “2”. Note that the order of step S303 to step S307 may be different.

  The present invention is also applicable to an internal combustion engine other than a cylinder injection type internal combustion engine, for example, a port injection type internal combustion engine. Furthermore, the present invention can be applied to an internal combustion engine other than a spark ignition type internal combustion engine, for example, a compression ignition type internal combustion engine.

  As mentioned above, although this invention was demonstrated based on embodiment etc., this invention is not limited to these. The present invention includes all modifications, applications, and equivalents included in the spirit 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.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder block 14 Combustion chamber 16 Cylinder 18 Piston 20 Intake manifold 22 Surge tank 24 Intake pipe 26 Air cleaner 28 Throttle valve 30 Exhaust manifold 32 Exhaust pipe 34 Pre-stage catalyst device 36 Rear-stage catalyst device 40 Spark plug 42 Injector 54 Crank angle sensor 56 In-cylinder pressure sensor 58 Intake pressure sensor Vi Intake valve Ve Exhaust valve

Claims (1)

A collecting means for collecting data corresponding to an output signal from an in-cylinder pressure sensor provided in the internal combustion engine;
An error determination value calculating means for calculating an error determination value for the data collected by the collecting means;
Error determination means for determining whether or not there is a noise error in the data based on a comparison result between the error determination value calculated by the error determination value calculation means and a predetermined threshold;
When it is determined that there is no noise error in the data by the error determination means, the in-cylinder pressure is calculated based on the data, while when the error determination means determines that the data has a noise error, An in-cylinder pressure detecting device for an internal combustion engine, comprising: an in-cylinder pressure calculating means for calculating an in-cylinder pressure without being based on the data.

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