JP2005194966A - Cylinder inner pressure detecting device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder inner pressure detecting device of an internal combustion engine by which a sensor output of a cylinder inner pressure is corrected with a high degree of precision to give a precise cylinder inner pressure detected. <P>SOLUTION: When an engine stops, a sensor output of the cylinder inner pressure when the cylinder inner pressure is near the atmospheric pressure is stored as cylinder inner pressure PCYLSiL at a low-pressure side (i=1 through 4) corresponding to reference pressure PCL at the low-pressure side. When the engine revolution speed NE is within a given value range (NEL, NEH) during engine cranking, the sensor output of the cylinder inner pressure in a compression process is stored as cylinder inner pressure PCYLSiH (S23, S24) at a high-pressure side corresponding to reference pressure PCH at the high-pressure side. According to the cylinder inner pressure PCYLSiL at the low-pressure side, the cylinder inner pressure PCYLSiH at the high-pressure side, the reference pressure PCL at the low-pressure side and the reference pressure PCH at the high-pressure side, corrected cylinder inner pressure PCYLi is calculated (S25). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an in-cylinder pressure detecting device for an internal combustion engine, and more particularly to an apparatus having a function of correcting characteristic variations of an in-cylinder pressure sensor.

  2. Description of the Related Art An in-cylinder pressure sensor that detects an in-cylinder pressure of an internal combustion engine uses a piezoelectric element widely. The pressure sensor using this piezoelectric element has a relatively large variation in output characteristics, and the detected value also changes depending on the tightening torque at the time of attachment. FIG. 7 is a diagram illustrating an example of output characteristics of an in-cylinder pressure sensor provided in four cylinders of a four-cylinder engine. The horizontal axis indicates actual pressure PCYLT, and the vertical axis indicates sensor output PCYLS. As described above, the variation of the detection value by the sensor is considerably large.

  In order to eliminate such variation in the detection value of the in-cylinder pressure sensor, Patent Document 1 discloses a pressure detection device that corrects the output of the in-cylinder pressure sensor. According to this device, when the engine is operating at a low speed and a low load, the deviation between the sensor output value in the intake stroke and the sensor output value in the exhaust stroke is calculated, and the deviation and the cylinder in the intake stroke are calculated. The output characteristic of the in-cylinder pressure sensor is corrected from the ratio with the internal pressure value.

JP-A-4-314951

  In the above-described conventional apparatus, since the sensor output value in the intake stroke and the sensor output value in the exhaust stroke are used, the difference between both output values is relatively small. Therefore, there is a problem that the accuracy of correction is not sufficient.

  The present invention has been made paying attention to this point, and it is an object of the present invention to provide an in-cylinder pressure detecting device for an internal combustion engine that can accurately correct the output of the in-cylinder pressure sensor and obtain an accurate detected in-cylinder pressure. To do.

  In order to achieve the above object, the invention according to claim 1 is a cylinder pressure detection device for an internal combustion engine comprising a cylinder pressure sensor (2) for detecting the cylinder pressure of the internal combustion engine, wherein the cylinder pressure is in the vicinity of atmospheric pressure. A low pressure side cylinder pressure storage means for storing the output of the cylinder pressure sensor as a low pressure side cylinder pressure (PCYLSiL), and the engine speed (NE) during cranking of the engine is within a predetermined range (NEL, NEH), the high pressure side cylinder pressure storage means for storing the output of the cylinder pressure sensor in the compression stroke as the high pressure side cylinder pressure (PCYLSiH), and the low pressure side stored by the low pressure side cylinder pressure storage means A correction method for correcting the output of the in-cylinder pressure sensor (2) according to the in-cylinder pressure (PCYLSiL) and the high-pressure side in-cylinder pressure (PCYLSiH) stored by the high-pressure side in-cylinder pressure storage means. And having a (S25).

  According to the first aspect of the present invention, the low-pressure side cylinder pressure, which is the detected pressure of the cylinder pressure sensor when the cylinder pressure is in the vicinity of atmospheric pressure, and the engine speed is within a predetermined range during cranking of the engine. The output of the in-cylinder pressure sensor is corrected according to the high-pressure side in-cylinder pressure detected and stored in the compression stroke. Since the high pressure side in-cylinder pressure is detected in the compression stroke, the pressure becomes relatively high and the pressure difference from the low pressure side in-cylinder pressure becomes large. Therefore, by performing correction using these detected pressures, the accuracy of correction can be increased.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an in-cylinder pressure detecting device for an internal combustion engine according to an embodiment of the present invention. Each cylinder of a four-cylinder diesel internal combustion engine (hereinafter referred to as “engine”) 1 is provided with an in-cylinder pressure sensor 2 for detecting an in-cylinder pressure PCYL. In the present embodiment, the in-cylinder pressure sensor 2 is configured integrally with a glow plug provided in each cylinder. A detection signal of the in-cylinder pressure sensor 2 is supplied to an electronic control unit (hereinafter referred to as “ECU”) 4. The engine 1 is provided with a crank angle position sensor 3 that detects a rotation angle of a crankshaft (not shown). The crank angle position sensor 3 generates a pulse every crank angle, and the pulse signal is supplied to the ECU 4.

  The ECU 4 supplies a control signal for the fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1 to the drive circuit 5. The drive circuit 5 is connected to the fuel injection valve 6, and supplies a drive signal corresponding to the control signal supplied from the ECU 4 to the fuel injection valve 6. Thus, at the fuel injection timing corresponding to the control signal output from the ECU 4, fuel is injected by the fuel injection amount corresponding to the control signal.

  The ECU 4 includes A / D conversion units 11 and 17, a pulse generation unit 13, a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 15 that stores a program executed by the CPU 14, and a calculation result obtained by the CPU 14. And a RAM (Random Access Memory) 16 for storing the data. The detection signal of the in-cylinder pressure sensor 2 is input to the A / D conversion unit 11, and the pulse signal output from the crank angle position sensor 3 is input to the pulse generation unit 13. Further, an atmospheric pressure sensor 7 for detecting the atmospheric pressure PA is provided, and the detection signal is input to the A / D conversion unit 17. The A / D converter 17 converts the detection signal of the atmospheric pressure PA into a digital value and supplies it to the CPU 14.

  The A / D conversion unit 11 includes a buffer 12, converts the detection signal input from the in-cylinder pressure sensor 2 into a digital value, and stores the digital value in the buffer 12. More specifically, the A / D converter 11 is supplied with a pulse signal PLS1 (hereinafter referred to as “1 degree pulse”) PLS1 having a crank angle of 1 degree from the pulse generator 13, and this 1 degree pulse PLS1. The in-cylinder pressure detection signal is sampled at a period of, converted into a digital value, and stored in the buffer 12.

  On the other hand, the pulse signal PLS6 with a crank angle of 6 degrees is supplied from the pulse generator 13 to the CPU 14, and the CPU 14 performs a process of reading the digital value stored in the buffer 12 with the period of the 6 degrees pulse PLS6. . That is, in this embodiment, the A / D conversion unit 11 does not issue an interrupt request to the CPU 14, but the CPU 14 performs a reading process at a cycle of the 6-degree pulse PLS6.

  FIG. 2 is a functional block diagram showing the fuel injection control device realized by the arithmetic processing of the CPU 14. The fuel injection control device includes a pressure correction unit 20, a digital filter 21, a correction unit 22, a basic injection amount calculation unit 23, a basic injection timing calculation unit 24, and multiplication units 25 and 26.

  As will be described later, the pressure correction unit 20 corrects the in-cylinder pressures (digital values) PCYLS1 to PCYLS4 detected by the in-cylinder pressure sensors 2 of the four cylinders, and outputs corrected in-cylinder pressures PCYL1 to PCYL4. The digital filter 21 performs low-pass filter processing on the corrected detected in-cylinder pressures PCYL1 to PCYL4. The correction unit 22 calculates a correction coefficient KTPC for the fuel injection amount and a correction coefficient KCPC for the fuel injection timing based on the corrected in-cylinder pressures PCYL1 to PCYL4 after the filtering process. The basic injection amount calculation unit 23 calculates a basic injection amount TBASE according to the engine speed NE calculated from the time interval of the 6-degree pulse PLS6 and the accelerator pedal depression amount AP detected by an accelerator sensor (not shown). To do. The basic injection timing calculation unit 24 calculates a basic injection timing CBASE according to the engine speed NE and the accelerator pedal depression amount AP.

  The multiplying unit 25 calculates the fuel injection amount TOUT by multiplying the basic injection amount TBASE by the correction coefficient KTPC. The multiplication unit 26 calculates the fuel injection timing CAINJ by multiplying the basic injection timing CBASE by the correction coefficient KCPC. The fuel injection amount TOUT and the fuel injection timing CAINJ are sequentially calculated corresponding to the four cylinders, and a control signal corresponding to the calculation result is supplied to the drive circuit 5. The fuel injection valve 6 of each cylinder injects fuel of the fuel injection amount TOUT into the combustion chamber at the fuel injection timing CAINJ according to the drive signal from the drive circuit 5.

  In the present embodiment, as shown in FIG. 5, detection pressures by the in-cylinder pressure sensors are acquired at two points of the low pressure side reference pressure PCL and the high pressure side reference pressure PCH, and variations in output characteristics for each sensor are corrected. Specifically, sensor output data (low pressure side in-cylinder pressure and high pressure side in-cylinder pressure) for calculating the corrected in-cylinder pressures PCYL1 to PCYL4 is measured by the processing shown in FIGS. Then, corrected in-cylinder pressures PCYL1 to PCYL4 are calculated using the measured sensor output data, the low pressure side reference pressure PCL, and the high pressure side reference pressure PCH.

FIG. 3 is a flowchart for explaining processing for measuring in-cylinder pressure sensor outputs PCYLS1 to PCYLS4 at the low-pressure side reference pressure PCL shown in FIG. This process is executed by the CPU 14.
In step S11, it is determined whether or not the engine 1 has been started (stopped). If the engine 1 is stopped, the maximum value of the sensor outputs PCYLS1 to PCYLS4 is less than or equal to a predetermined pressure PLMTH (for example, 0.11 MPa). It is determined whether or not (step S12). If the answer to step S11 or S12 is negative (NO), the process immediately ends. If the answer to step S12 is affirmative (YES), the cylinder pressure sensor outputs PCYLS1, PCYLS2, PCYLS3, and PCYLS4 of each cylinder are measured (read) and stored as low-pressure side cylinder pressure PCYLSiL (i = 1 to 4). (Step S13). In step S <b> 14, the atmospheric pressure PA is measured by the atmospheric pressure sensor 7.

  Since the pressure detected by each in-cylinder pressure sensor is equal to the atmospheric pressure PA while the engine is stopped, the atmospheric pressure PA measured here is stored as the low-pressure side reference pressure PCL.

  FIG. 4 is a flowchart for explaining processing for measuring in-cylinder pressure sensor outputs PCYLS1 to PCYLS4 at the high-pressure side reference pressure PCH shown in FIG. This process is executed by the CPU 14.

  In step S21, it is determined whether or not the starter of the engine 1 is turned on. When the starter is turned on, that is, during cranking, the process proceeds to step S22, and fuel injection is stopped. In subsequent steps S23 and S24, high-pressure side cylinder pressures PCYLS1H, PCYLS2H, PCYLS3H, and PCYLS4H (PCYLSiH, i = 1 to 4) are measured.

That is, in step S23, it is determined whether or not the engine speed NE is within a range between a predetermined lower limit value NEL (for example, 100 rpm) and a predetermined upper limit value NEH (for example, 300 rpm). If the answer is affirmative (YES), the in-cylinder pressure sensor output of each cylinder is measured (read) at the compression top dead center of each cylinder (top dead center at which the compression stroke ends) by the in-cylinder pressure sensor 2 of each cylinder. The high pressure side in-cylinder pressure PCYLSiH (i = 1 to 4) is stored (step S24). After measuring the high pressure side cylinder pressure PCYLSiH of all cylinders by the cylinder pressure sensor of each cylinder, the process proceeds to step S25.
In step S25, fuel injection is started.

そして式（１）により算出される補正筒内圧ＰＣＹＬｉが、圧力補正部２０からディジタルフィルタ２１に入力される。 The low pressure side cylinder pressure PCYLSiL, the high pressure side cylinder pressure PCYLSiH, the low pressure side reference pressure PCL, the high pressure side reference pressure PCH, and the cylinder pressure sensor output PCYLSi obtained by the processing of FIGS. The corrected in-cylinder pressure PCYLi is calculated. The high-pressure side reference pressure PCH is, for example, about 1 MPa.

Then, the corrected in-cylinder pressure PCYLi calculated by the equation (1) is input from the pressure correction unit 20 to the digital filter 21.

  As described above, in the present embodiment, the low pressure side cylinder pressure PCYLSiL is measured while the engine 1 is stopped, and the high pressure side cylinder pressure PCYLSiH is measured at the compression top dead center during cranking of the engine 1. Based on the internal pressure PCYLSiL, the high-pressure side cylinder pressure PCYLSiH, the low-pressure side reference pressure PCL, and the high-pressure side reference pressure PCH, the sensor output PCYLSi is corrected, and a corrected cylinder pressure PCYLi is calculated. Since the differential pressure between the low-pressure side reference pressure PCL and the high-pressure side reference pressure PCH becomes relatively large, for example, about 1 MPa, accurate correction can be performed.

  In the present embodiment, the CPU 14 and the RAM 16 constitute a low pressure side in-cylinder pressure storage means and a high pressure side in-cylinder pressure storage means, and the CPU 14 constitutes a correction means. More specifically, the process of FIG. 3 corresponds to the low pressure side in-cylinder pressure storage means, and steps S21 to S24 in FIG. 4 correspond to the high pressure side in-cylinder pressure storage means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the low-pressure side cylinder pressure PCYLSiL is measured while the engine 1 is stopped by the processing of FIG. 3, but the processing shown in FIG. You may make it measure during the deceleration fuel cut operation which interrupts | blocks the fuel supply of this.

  In step S31 of FIG. 6, it is determined whether or not the deceleration fuel cut operation is being performed. If the deceleration fuel cut operation is not being performed, the processing is immediately terminated. If the deceleration fuel cut operation is being performed, the low pressure side in-cylinder pressure PCYLSiL is measured at the timing when the intake valve is opened in each cylinder (step S32). Next, the atmospheric pressure PA is measured and stored as the low-pressure side reference pressure PCL (step S33).

  In an engine having a throttle valve in the intake pipe, the low-pressure side cylinder pressure PCYLSiL may be measured with the throttle valve closed. Thereby, the differential pressure from the high-pressure side in-cylinder pressure PCYLSiH is increased, and the correction accuracy can be further increased.

In the above-described embodiment, an example of a four-cylinder diesel internal combustion engine has been described. However, the present invention is not limited to this, and the present invention can also be applied to a diesel internal combustion engine having a different number of cylinders or a gasoline internal combustion engine. .
The present invention can also be applied to an in-cylinder pressure detection device such as an engine for a marine propulsion device such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the internal combustion engine and cylinder pressure detection apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the fuel-injection control apparatus implement | achieved by the process performed by CPU of FIG. It is a flowchart of the process which measures a low pressure side cylinder pressure (PCYLSiL). It is a flowchart of the process which measures a high voltage | pressure side cylinder pressure (PCYLSiH). It is a figure for demonstrating a low voltage | pressure side reference pressure (PCL) and a high voltage | pressure side reference pressure (PCH). It is a flowchart which shows the modification of the process of FIG. It is a figure for demonstrating the dispersion | variation in a cylinder pressure sensor output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel internal combustion engine 2 Cylinder pressure sensor 4 Electronic control unit 14 CPU (Low pressure side cylinder pressure memory | storage means, High pressure side cylinder pressure memory | storage means, correction | amendment means)
16 RAM (low pressure side cylinder pressure storage means, high pressure side cylinder pressure storage means)

Claims (1)

In the in-cylinder pressure detection apparatus for an internal combustion engine including an in-cylinder pressure sensor for detecting an in-cylinder pressure of the internal combustion engine,
Low pressure side cylinder pressure storage means for storing the output of the cylinder pressure sensor when the cylinder pressure is near atmospheric pressure as low pressure side cylinder pressure;
High-pressure side cylinder pressure storage means for storing the output of the cylinder pressure sensor in the compression stroke as a high-pressure side cylinder pressure when cranking the engine and the engine speed is within a predetermined range;
Correction means for correcting the output of the in-cylinder pressure sensor in accordance with the low-pressure side in-cylinder pressure stored by the low-pressure side in-cylinder pressure storage means and the high-pressure side in-cylinder pressure stored by the high-pressure side in-cylinder pressure storage means. An in-cylinder pressure detecting device for an internal combustion engine.

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