JP2005180357A - Cylinder internal pressure measuring device and cylinder internal pressure measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder internal pressure measuring device and a cylinder internal pressure measuring method, in which a detection value of a cylinder internal pressure detecting means is suitably processed to measure the actual cylinder internal pressure with higher precision. <P>SOLUTION: An internal combustion engine 1 is provided with a crank angle sensor 14 to detect the number of revolutions, a cylinder internal pressure sensor 15 to detect the cylinder internal pressure, a suction pressure sensor 16 to detect the absolute pressure of the suction air in a surge tank 8, and an ECU 20. The ECU 20 decides reference time when the cylinder internal pressure approximately agrees with the pressure of the suction air in a suction system, based on the number of the revolutions of the internal combustion engine 1, sets the absolute pressure of the suction air detected at the reference time with the suction pressure sensor 16, and obtains the measured value of the cylinder internal pressure based on the reference pressure and the detection value of the cylinder internal pressure sensor 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an in-cylinder pressure measuring device and an in-cylinder pressure measuring method for measuring an in-cylinder pressure of an internal combustion engine.

  Conventionally, in various internal combustion engines, the in-cylinder pressure sensor is used to detect the combustion pressure in the combustion chamber, that is, the in-cylinder pressure, and this in-cylinder pressure is used as a parameter for setting the fuel injection amount, ignition timing, and the like. It is done. In this case, as the in-cylinder pressure sensor for detecting the in-cylinder pressure, a sensor that outputs the in-cylinder pressure as a relative value with respect to the atmospheric pressure is generally used. For this reason, taking into account fluctuations in the atmospheric pressure, the differential pressure between the in-cylinder pressure detected in a predetermined crank angle range in which the in-cylinder pressure is estimated to be close to the atmospheric pressure and the absolute pressure in the intake pipe There is also known a technique for obtaining a final measured value of the in-cylinder pressure by correcting the detected in-cylinder pressure by the differential pressure (see, for example, Patent Document 1).

JP-A-11-193743

  However, even when the measured value of the in-cylinder pressure obtained by the conventional method as described above is used, appropriate control of the internal combustion engine may not be executed depending on the operating conditions. This is considered to be caused by the fact that the in-cylinder pressure does not take a value close to atmospheric pressure in the crank angle region estimated in advance.

  Therefore, an object of the present invention is to provide an in-cylinder pressure measuring apparatus and an in-cylinder pressure measuring method that can appropriately measure the detected value of the in-cylinder pressure detecting means and accurately measure the actual in-cylinder pressure.

  An in-cylinder pressure measuring device according to the present invention is an in-cylinder pressure measuring device for measuring an in-cylinder pressure of an internal combustion engine, an in-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine, and intake air in an intake system of the internal combustion engine. Intake pressure detection means for detecting absolute pressure, rotation speed detection means for detecting the rotation speed of the internal combustion engine, and in-cylinder pressure and pressure of intake air in the intake system based on the rotation speed detected by the rotation speed detection means And a reference pressure setting means for setting the absolute pressure of the intake air detected at the reference time by the intake pressure detection means as a reference pressure, and a reference pressure determined by the reference pressure setting means The measured value of the in-cylinder pressure is obtained based on the detected value of the in-cylinder pressure detecting means.

  This in-cylinder pressure measuring device sets the absolute pressure of the intake air detected at the reference time (near intake bottom dead center) where the in-cylinder pressure and the intake air pressure in the intake system substantially match as the reference pressure. A measured value of the in-cylinder pressure is obtained based on the pressure and the detected value of the in-cylinder pressure detecting means. Here, as a result of intensive studies by the inventor, the reference time, which is the timing at which the in-cylinder pressure and the intake air pressure in the intake system substantially coincide, changes in the rotational speed of the internal combustion engine due to the influence of intake pulsation and the like. It turns out that it fluctuates according to. Here, “substantially coincidence” includes a case where the in-cylinder pressure and the intake air pressure in the intake system do not completely coincide, but the difference between the two is within a predetermined range.

  Based on this, in this in-cylinder pressure measuring device, the reference time is determined based on the rotational speed detected by the rotational speed detection means, and the absolute pressure of the intake air detected at the reference time by the intake pressure detection means is the reference pressure. Will be set as needed. As a result, the reference pressure for obtaining the measured value of the in-cylinder pressure is updated at any time according to the operating state of the internal combustion engine. It is possible to accurately measure the in-cylinder pressure.

  An in-cylinder pressure measuring method according to the present invention is a method for measuring an in-cylinder pressure of an internal combustion engine provided with an in-cylinder pressure detecting means for detecting an in-cylinder pressure. The reference time at which the pressure of the intake air substantially matches is determined, the absolute pressure of the intake air in the intake system detected at the reference time is set as the reference pressure, and based on this reference pressure and the detected value of the in-cylinder pressure detecting means A measured value of in-cylinder pressure is obtained.

  According to the present invention, it is possible to realize an in-cylinder pressure measuring apparatus and an in-cylinder pressure measuring method that can appropriately measure the detected value of the in-cylinder pressure detecting means and accurately measure the actual in-cylinder pressure.

  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 showing an internal combustion engine provided with a crank angle sensor correction device according to the present invention. The internal combustion engine 1 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Is. Although only one cylinder is shown in FIG. 1, the internal combustion engine 1 is preferably configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is configured as a four-cylinder engine, for example.

  The intake port of each combustion chamber 3 is connected to an intake pipe (intake manifold) 5, and the exhaust port of each combustion chamber 3 is connected to an exhaust pipe (exhaust manifold) 6. In addition, an intake valve Vi that opens and closes the intake port and an exhaust valve Ve that opens and closes the exhaust port are disposed in the cylinder head of the internal combustion engine 1 for each combustion chamber 3. Each intake valve Vi and each exhaust valve Ve are opened and closed by, for example, a valve operating mechanism (not shown) having a variable valve timing function. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3.

  The intake pipe 5 (intake manifold) is connected to a surge tank 8 as shown in FIG. An air supply line L1 is connected to the surge tank 8, and the air supply line L1 is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (in this embodiment, an electronic throttle valve) 10 is incorporated in the middle of the air supply line L1 (between the surge tank 8 and the air cleaner 9). These intake pipe 5, surge tank 8, air cleaner 9, throttle valve 10 and air supply line L 1 constitute an air supply system of the internal combustion engine 1. On the other hand, as shown in FIG. 1, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Further, the internal combustion engine 1 has a plurality of injectors 12, and the injectors 12 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3. Each piston 4 of the internal combustion engine 1 is configured as a so-called deep dish top surface type, and a recess 4a is formed on the upper surface thereof. In the internal combustion engine 1, fuel such as gasoline is directly injected from each injector 12 toward the recess 4 a of the piston 4 in each combustion chamber 3 in a state where air is sucked into each combustion chamber 3. As a result, in the internal combustion engine 1, the fuel / air mixture layer is formed (stratified) in the vicinity of the spark plug 7 so as to be separated from the surrounding air layer. And stable stratified combustion can be performed. The internal combustion engine 1 of the present embodiment is described as a so-called direct injection engine, but is not limited to this, and the present invention can be applied to an intake pipe (intake port) injection type internal combustion engine. Not too long.

  Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism and the like described above are electrically connected to an ECU 20 that functions as a control device for the internal combustion engine 1. The ECU 20 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 20, and the ECU 20 uses various maps stored in the storage device and obtains a desired output based on detection values of the various sensors. The spark plug 7, the throttle valve 10, the injector 12, the valve operating mechanism and the like are controlled.

  As shown in FIG. 1, the sensors connected to the ECU 20 include a crank angle sensor (crank angle sensor) 14. The crank angle sensor 14 is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and provides a pulse signal indicating the rotation angle of the crankshaft to the ECU 20. ECU20 calculates | requires the rotation speed of the internal combustion engine 1 (crankshaft) based on the signal from the crank angle sensor 14, and utilizes it for various control.

  Further, the internal combustion engine 1 has in-cylinder pressure sensors (in-cylinder pressure detecting means) 15 including a semiconductor element, a piezoelectric element, an optical fiber sensor, or the like corresponding to the number of cylinders. The cylinder head is disposed so that the pressure-receiving surface faces the combustion chamber 3. Each in-cylinder pressure sensor 15 outputs a pressure (in-cylinder pressure) applied to the pressure receiving surface in the combustion chamber 3 as a relative value with respect to the atmospheric pressure, and a voltage signal (AC signal) corresponding to the in-cylinder pressure is transmitted to the ECU 20. To give.

  Furthermore, the internal combustion engine 1 has an intake pressure sensor 16 that detects the pressure (intake pressure) of intake air in the surge tank 8 as an absolute pressure. The intake pressure sensor 16 is electrically connected to the ECU 20 and gives a signal indicating the detected absolute pressure of the intake air in the surge tank 8 to the ECU 20. The detected values of the crank angle sensor 14, each in-cylinder pressure sensor 15 and the intake pressure sensor 16 are sequentially given to the ECU 20 every minute time, and are stored and held in a predetermined storage area (buffer) of the ECU 20 by a predetermined amount.

  The ECU 20 that has received a signal from each in-cylinder pressure sensor 15 appropriately processes the signal from each in-cylinder pressure sensor 15 to obtain (measure) an accurate in-cylinder pressure in each combustion chamber 3, and obtains the obtained in-cylinder pressure. The pressure is used for controlling the internal combustion engine 1. When measuring the in-cylinder pressure, the ECU 20 generally considers that the in-cylinder pressure in each combustion chamber 3 and the pressure of the intake air in the surge tank 8 (intake pressure) generally coincide in the vicinity of the intake bottom dead center. The absolute pressure of the intake air detected by the intake pressure sensor 16 at the reference time when the internal pressure and the pressure (intake pressure) of the intake air in the surge tank 8 coincide with each other is set as the reference pressure. Then, the ECU 20 corrects and outputs the measured value of the in-cylinder pressure based on the reference pressure and the detected value of each in-cylinder pressure sensor 15. Here, assuming that the actual detected value of the in-cylinder pressure is Pcyc and the reference pressure is Pim, the ECU 20 first obtains the correction value as “correction value = Pcyc−Pim” and then determines the in-cylinder pressure. The measured value (true value) is output as “measured value of in-cylinder pressure = Pcyc + correction value”.

Here, as a result of intensive research conducted by the present inventor, as shown in FIG. 2, the reference time (◯ in FIG. 2) is the timing at which the in-cylinder pressure and the pressure of the intake air in the surge tank 8 substantially coincide. (See the symbol) is delayed as the rotational speed of the internal combustion engine 1 increases due to the influence of intake pulsation or the like, and when the rotational speed of the internal combustion engine 1 is the reference rotational speed N ₀ as shown in FIG. It has been found that the phase lag amount λ from the timing at which the in-cylinder pressure and the intake air pressure substantially coincide increases in proportion to the rotational speed of the internal combustion engine 1. FIG. 2 shows the in-cylinder pressure waveform at each rotation speed (600 to 3600 rpm) side by side so that the fluctuation at the reference time can be easily understood.

  Based on such research results, the internal combustion engine 1 follows the above-described reference time (the crank angle at that time) based on the rotational speed of the internal combustion engine 1 obtained from the detected value of the crank angle sensor 14 in accordance with the procedure shown in FIG. ) Is determined, and the absolute pressure of the intake air detected at the reference time by the intake pressure sensor 16 is set as the reference pressure as needed.

The reference pressure setting process in FIG. 4 is executed by the ECU 20 every predetermined time. In this case, when it is time to set the reference pressure, the ECU 20 first acquires the rotational speed of the internal combustion engine 1 based on the detection value of the crank angle sensor 14 (S10). Thereafter, the ECU 20 sets a phase delay amount λ corresponding to the rotational speed acquired in S10 using a predetermined map or function formula (S12). Map or a function expression used in S12, the phase delay amount of the timing of the rotational speed and the internal combustion engine 1, the cylinder pressure when the rotational speed is the reference rotational speed N ₀ and the pressure of the intake air is almost coincident It is created in advance so as to define the relationship with λ (see FIG. 3), and is stored in the storage device of the ECU 20. In creating the map or function expression used in S12, it is preferable to consider the opening / closing timing and lift amount of the intake valve Vi and the exhaust valve Ve of the internal combustion engine 1, and the back pressure in the internal combustion engine 1.

Further, ECU 20 includes a phase delay λ set at S12, since under the reference rotational speed N ₀ in-cylinder pressure and the pressure of the intake air is almost match timing (crank angle at that time), to S10 At the reference time corresponding to the rotation speed acquired in step S10, that is, the timing at which the cylinder pressure and the pressure of the intake air in the surge tank 8 substantially coincide with each other under the rotation speed acquired in S10 (the crank angle at that time). Is set (S14). When the reference time corresponding to the rotational speed is set in this way, the ECU 20 determines the absolute pressure of the intake air detected by the intake pressure sensor 16 at the reference time closest to the execution of the process of S10 from a predetermined storage area. Reading and setting the value as a reference pressure (S16).

  The processes of S10 to S16 described above are repeatedly executed by the ECU 20 at predetermined time intervals. Thereby, in the internal combustion engine 1, the reference pressure for obtaining the measured value of the in-cylinder pressure is updated as needed according to the operating state of the internal combustion engine 1. Then, the ECU 20 obtains a measured value of the in-cylinder pressure based on the reference pressure sequentially updated in this way and the detected value of each in-cylinder pressure sensor 15. Therefore, in the internal combustion engine 1, the detection value of each in-cylinder pressure sensor 15 is appropriately processed, and the actual in-cylinder pressure is accurately measured.

It is a schematic block diagram of the internal combustion engine provided with the correction apparatus of the crank angle sensor by this invention. 6 is a graph illustrating that the reference time when the in-cylinder pressure and the pressure of intake air in the intake system substantially match varies when the rotational speed of the internal combustion engine is changed. 6 is a graph illustrating the relationship between the rotational speed of an internal combustion engine and the amount of phase delay from the timing at which the in-cylinder pressure and the intake air pressure approximately coincide with each other when the rotational speed is the reference rotational speed. 2 is a flowchart for explaining a reference pressure setting procedure used when measuring an in-cylinder pressure in the internal combustion engine of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Combustion chamber 4 Piston 5 Intake pipe 6 Exhaust pipe 7 Spark plug 8 Surge tank 9 Air cleaner 10 Throttle valve 11a, 11b Catalyst device 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor Ve Exhaust valve Vi Intake valve

Claims (2)

In the cylinder pressure measuring device for measuring the cylinder pressure of the internal combustion engine,
An in-cylinder pressure detecting means for detecting an in-cylinder pressure of the internal combustion engine;
Intake pressure detection means for detecting the absolute pressure of intake air in the intake system of the internal combustion engine;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Based on the rotational speed detected by the rotational speed detection means, a reference time is determined in which the in-cylinder pressure and the intake air pressure in the intake system substantially coincide with each other, and the intake pressure detected by the intake pressure detection means at the reference time is determined. A reference pressure setting means for setting the absolute pressure of air as a reference pressure,
An in-cylinder pressure measuring device that obtains a measured value of in-cylinder pressure based on the reference pressure determined by the reference pressure setting unit and a detected value of the in-cylinder pressure detecting unit. In the in-cylinder pressure measuring method of the internal combustion engine provided with the in-cylinder pressure detecting means for detecting the in-cylinder pressure,
Based on the number of revolutions of the internal combustion engine, a reference time in which the in-cylinder pressure and the intake air pressure in the intake system of the internal combustion engine substantially coincide with each other is determined, and the absolute pressure of the intake air in the intake system detected at the reference time Is set as a reference pressure, and a measured value of the in-cylinder pressure is obtained on the basis of the reference pressure and the detected value of the in-cylinder pressure detecting means.

Images