JP2007064878A - Device of calibrating cylinder internal pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device of calibrating a cylinder internal pressure sensor calibrated in a state where the cylinder internal pressure is mounted in an engine. <P>SOLUTION: The device of calibrating the cylinder internal pressure sensor comprises the cylinder internal pressure sensor 3 installed in a cylinder 2 of the engine 1, and a vibration (acceleration) sensor 4 attached to the outside of a casing of the engine 1. The device comprises comparing a cylinder internal pressure detection signal for outputting the cylinder internal pressure sensor 3 with an integral value of a vibration acceleration signal output by the vibration sensor 4 and calibrating the cylinder internal pressure detection signal output by the cylinder internal pressure sensor 3 from the ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a calibration apparatus for an in-cylinder pressure sensor that can be calibrated while the in-cylinder pressure sensor is mounted on an engine.

  When an engine is developed and the engine under development is tested, an in-cylinder pressure sensor is installed in the cylinder of the engine to detect the in-cylinder pressure. Since the engine does not have a hole for inserting the in-cylinder pressure sensor, the in-cylinder pressure sensor may be replaced with a glow plug. Of course, a hole for the in-cylinder pressure sensor may be specially provided.

  A pressure pickup using a piezoelectric element is used for the in-cylinder pressure sensor.

  In the future, it is also possible to incorporate in-cylinder pressure sensors into engines that are mass-produced and mounted on vehicles, not under development, and to perform highly accurate combustion control using the detected in-cylinder pressure. .

No. 7-55303 JP-A-5-125991 JP-A-5-71396

  Since the in-cylinder pressure sensor installed in the cylinder of the engine is always exposed to the combustion gas, the deterioration (change over time) is remarkable. For this reason, with the passage of time, the in-cylinder pressure detection signal output from the in-cylinder pressure sensor does not show a correct value.

  Conventionally, the cylinder pressure sensor is removed from the engine at regular intervals, the calibration value is checked with a dedicated calibration device, and the calibration value is applied to the cylinder pressure detection signal after the cylinder pressure sensor is returned to the engine. By doing so, a calibrated signal of the in-cylinder pressure is obtained.

  However, since the work of attaching and detaching the in-cylinder pressure sensor to the engine takes time, it is desirable that calibration can be performed while the in-cylinder pressure sensor is attached to the engine.

  In addition, it is inconvenient to use a dedicated calibration device for checking the calibration value, and it is desirable that conventional in-vehicle devices such as an engine control device check the calibration value and perform the calibration.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and provide a calibration device for an in-cylinder pressure sensor that can be calibrated while the in-cylinder pressure sensor is mounted on an engine.

  In order to achieve the above object, the present invention comprises an in-cylinder pressure sensor installed in an engine cylinder and a vibration (acceleration) sensor attached to the outside of the engine casing. The in-cylinder pressure detection signal and the integrated value of the vibration acceleration signal output from the vibration sensor are compared, and the in-cylinder pressure detection signal output from the in-cylinder pressure sensor is calibrated based on the ratio.

  Calculates the calibration coefficient from the peak ratio calculation unit that calculates the ratio between the peak value of the in-cylinder pressure detection signal and the peak value of the integrated value of the vibration acceleration signal, and the peak ratio obtained at the initial stage and the peak ratio obtained at the time of calibration. A calibration coefficient calculation unit and a calibration unit that applies a calibration coefficient to the in-cylinder pressure detection signal to obtain a signal in which the in-cylinder pressure is calibrated may be provided.

  The present invention exhibits the following excellent effects.

  (1) Calibration can be performed with the in-cylinder pressure sensor mounted on the engine.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an in-cylinder pressure sensor calibration apparatus according to the present invention includes an in-cylinder pressure sensor 3 installed in a combustion chamber (hereinafter referred to as a cylinder) 2 of an engine 1, and a casing of the engine 1. A vibration (acceleration) sensor 4 attached to the outside, and the in-cylinder pressure detection signal output from the in-cylinder pressure sensor 3 is compared with the integrated value of the vibration acceleration signal output from the vibration sensor 4; The in-cylinder pressure detection signal output from the in-cylinder pressure sensor 3 is calibrated.

  Further, the calibration device includes a peak ratio calculation unit 6 that calculates a ratio between the peak value of the in-cylinder pressure detection signal and the peak value of the integrated value of the vibration acceleration signal, and the peak ratio obtained at the initial time and the peak obtained at the time of calibration. A calibration coefficient calculation unit 7 that calculates a calibration coefficient from the ratio, and a calibration unit 8 that multiplies the in-cylinder pressure detection signal by the calibration coefficient to obtain a calibrated signal of the in-cylinder pressure.

  The peak ratio calculation unit 6, the calibration coefficient calculation unit 7, and the calibration unit 8 are built in a conventionally known engine control unit (ECU) 9.

  It is necessary for the engine 1 to determine a common rail 11 that supplies fuel, a fuel injection valve 12 that injects fuel from the common rail 11 into each cylinder 2, a crank angle sensor 13 that detects a crank rotation angle, an injection timing, and the like. As a simple rotation sensor, a cam sensor 14 for detecting a cam signal is conventionally provided.

  The vibration sensor 4 is attached to a cylinder block or a cylinder head in the casing of the engine 1. Thereby, the acceleration which the engine 1 vibrates can be taken out as a vibration acceleration signal.

  The in-cylinder pressure sensor 3 is inserted into the cylinder 2 using a glow plug hole or the like. The use of the glow plug hole is a temporary measure for developing and testing the present invention. In mass production, an integrated glow plug and in-cylinder pressure sensor are used.

  As shown in FIG. 2, the ECU 9 includes an I / O group 21 composed of a plurality of signal input / output interfaces, a CPU 22 that realizes various control contents by software processing, and a drive circuit group 23 composed of a plurality of power drive circuits. It is divided roughly into. The I / O group 21 is connected to various sensors and input / output signal lines from a control circuit other than the ECU 9 that assists the ECU 9. Power lines to various actuators are connected to the drive circuit group 23. FIG. 2 shows, as input signals, an in-cylinder pressure detection signal from the in-cylinder pressure sensor, a vibration acceleration signal from the vibration sensor 4, a cam signal from the cam sensor 14, a crank rotation angle signal from the crank angle sensor 13, and the like. However, there may be other input signals. Similarly, as the actuator, a fuel injection valve 12, an EGR valve, a throttle valve, a supercharger, and the like are shown, but there may be other actuators. The software processing executed by the CPU 22 includes various calculation processes according to the present invention.

  The ECU 9 samples various input signals received by the I / O group 21, stores them in a memory (not shown), and uses them for processing. The manner of sampling will be described with reference to FIG.

  The ECU 9 first determines a period for sampling the in-cylinder pressure detection signal and the vibration acceleration signal. For this determination, the TDC signal a obtained from the crank rotation angle signal and the cam signal is used. The TDC signal a is a signal representing the timing at which the crank is located at the top dead center in each cylinder. For example, in a four-cylinder engine, TDC # 1, # 2, # 3, # 4, # 1,. Repeat in the order.

  The ECU 9 sets a time range corresponding to a crank rotation angle range over 30 degrees before and after each TDC timing # 1, # 2, # 3, and # 4 as a sampling period. During this sampling period, the data sample trigger b rises. When the data sample trigger b rises, A / D conversion c is performed at appropriate time intervals, and the time series of the target signal is taken into the memory.

  When the sampling period ends, the ECU 9 starts the filtering and integration signal processing d. When the signal processing d ends, the calibration processing e of the present invention is performed.

  As shown in the figure, the in-cylinder pressure detection signal f in each cylinder rises slightly before TDC timings # 1, # 2, # 3, and # 4, and substantially at TDC timings # 1, # 2, # 3, and # 4. It reaches the peak and falls with a curve that is almost symmetrical with the rising edge. The vibration acceleration signal g rises slightly before TDC timings # 1, # 2, # 3, and # 4, reaches a positive peak before TDC timings # 1, # 2, # 3, and # 4, and is inverted. After reaching the negative peak after TDC timing # 1, # 2, # 3, # 4, it returns to zero. The integrated value h of the vibration acceleration signal g has a peak at a position slightly delayed from the positive peak of the vibration acceleration signal g.

  The integral value h of the vibration acceleration signal g is proportional to the in-cylinder pressure detection signal f. The deterioration of the in-cylinder pressure sensor 3 is detected and the calibration coefficient is calculated by comparing the peak value of the integral value h and the peak value of the in-cylinder pressure detection signal f in a specified time interval. Can do.

  In FIG. 3, various signals are not divided for each cylinder. Actually, various signals are detected for each cylinder, and signal processing is also performed for each cylinder. That is, in-cylinder pressure sensor 3 is attached to each cylinder, and vibration sensor 4 is also attached to each cylinder. In-cylinder pressure sensor 3 attached to a certain cylinder is attached to the same cylinder for calibration. A vibration sensor 4 is used. However, one vibration sensor 4 may be provided for the entire engine, and the in-cylinder pressure sensor 3 for all cylinders may be calibrated.

  Hereinafter, operations performed by the calibration apparatus for the in-cylinder pressure sensor according to the present invention, specifically, operations performed by the peak ratio calculation unit 6, the calibration coefficient calculation unit 7, and the calibration unit 8 in the ECU 9 will be described.

  As shown in FIG. 4A, the ECU 9 turns the data sampling flag ON if the fuel injection amount = 0, and turns the data sampling flag OFF if the fuel injection amount = 0. This process is called a correction process determination process. As shown in FIG. 4B, the A / D conversion end interrupt is validated if the data sampling flag is ON, otherwise the A / D conversion end interrupt is invalidated. The A / D conversion end interrupt process will be described later.

  In this correction process determination process, data sampling is always enabled when the fuel injection amount = 0 in order to obtain the in-cylinder pressure in a state where fuel is not injected. The fuel injection amount is taken into account because if the peak is obtained during injection, the peak varies depending on the difference in the injection amount at that time. If the fuel injection amount = 0, it is avoided. be able to. This contributes to reducing the memory consumption and CPU load of the ECU 9.

  As shown in FIG. 5, in the A / D conversion end interruption process, the ECU 9 reads the in-cylinder pressure detection signal f and the vibration acceleration signal g, and determines whether or not the data sample trigger b = 0. If the data sample trigger b is not 0, the A / D conversion end interrupt process is ended (returned). If the data sample trigger b = 0, the A / D conversion is invalidated and then signal processing described later is performed. The data sample trigger b = 0 is a case where it deviates 30 degrees or more before and after the TDC timing.

  As shown in FIG. 6, in the signal processing, the ECU 9 first performs low-pass filter processing on the in-cylinder pressure detection signal f and band-pass filter processing on the vibration acceleration signal g. These filtering processes are performed for the purpose of extracting only signals in a specific frequency band that is necessary. The filter processing may be performed by the CPU 22 using software or by the I / O group 21 using an analog filter.

  Further, the ECU 9 performs an integration process on the vibration acceleration signal g to obtain an integral value h, and stores the time series in the memory. Next, the ECU 9 completes (returns) the signal processing after performing in-cylinder pressure calibration processing described later.

As shown in FIG. 7, in the in-cylinder pressure calibration process, the ECU 9 first calculates a peak value (in-cylinder pressure peak value) Vpmax of the in-cylinder pressure detection signal f, and calculates an integrated value h of the vibration acceleration signal g. The peak value (integrated peak value) Vkmax is calculated, and then α = Vpmax / Vkmax (1)
To calculate the ratio (hereinafter referred to as peak ratio) α of both peak values (peak ratio calculation unit 6).

Further, the ECU 9 calculates the following formula (definition of variables and the like will be described later):
Vpc (t) = (α / α ′) × Vp (t) (2)
Thus, the calibration calculation for calculating Vpc (t) is performed, and the in-cylinder pressure calibration process is completed (returned).

  Here, further details of the in-cylinder pressure calibration process will be described. The in-cylinder pressure detection signal as time series data is Vp (t), and the vibration acceleration integral value is Vk (t).

  The ECU 9 performs a test for operating the engine when the vehicle is shipped from the factory. During the test, the in-cylinder pressure peak value and the vibration acceleration integrated value peak value are acquired, and the peak ratio is calculated and learned (stored in the memory).

At that time, the ECU 9 changes the in-cylinder pressure by changing control amounts of actuators such as a supercharger, an EGR valve, and a throttle. When the in-cylinder pressure changes, the ECU 9 acquires the peak ratio α for each in-cylinder pressure according to the equation (1). However, here
α (x) = Vpmax (x) / Vkmax (x) (3)
In this way, the difference in pressure is expressed by x as a function of x.

When the in-cylinder pressure sensor 3 deteriorates with time, the in-cylinder pressure peak value Vpmax (x) decreases to Vpmax (x) ′. That is,
α ′ = Vpmax (x) ′ / Vkmax (x) (4)
Is established. Since Vkmax does not change, from (3) and (4), Vpmax (x) = (α / α ′) × Vpmax (x) ′ (5)
It becomes.

  From this proportional relationship, the calibration value of the in-cylinder pressure waveform can be described as follows.

Vpc (t) = (α / α ′) × Vp (t) (6)
The peak ratio calculation unit 6 calculates the ratio α between the peak value of the in-cylinder pressure detection signal and the peak value of the integral value of the vibration acceleration signal, and the calibration coefficient calculation unit 7 calculates the peak ratio α obtained at the initial time and the calibration value. The calibration coefficient (α / α ′) is calculated from the peak ratio α ′, and the calibration unit 8 calibrates the in-cylinder pressure by multiplying the in-cylinder pressure detection signal Vp (t) by the calibration coefficient (α / α ′). This is the signal Vpc (t).

  FIG. 8 shows detailed waveforms. The in-cylinder pressure waveform has a peak, and the peak value is Vpmax. The vibration acceleration signal waveform gradually increases from zero and becomes maximum, the sign is rapidly reversed, and gradually increases to zero. The integrated value waveform has a peak at substantially the same position as the in-cylinder pressure waveform, and the peak value is Vkmax.

  As described above, the in-cylinder pressure sensor calibration apparatus according to the present invention compares the in-cylinder pressure detection signal output from the in-cylinder pressure sensor 3 with the integrated value of the vibration acceleration signal output from the vibration sensor 4. From the ratio, the cylinder pressure detection signal output from the cylinder pressure sensor 3 can be calibrated.

  The in-cylinder pressure sensor calibration apparatus according to the present invention includes a calibration signal obtained by applying a calibration coefficient obtained from the peak ratio obtained at the initial time and the peak ratio obtained at the time of calibration to the in-cylinder pressure detection signal; As a result, calibration can be performed with the in-cylinder pressure sensor mounted on the engine.

It is a block diagram of the calibration apparatus of the cylinder pressure sensor which shows one Embodiment of this invention. It is an internal block diagram of the calibration apparatus of FIG. 3 is a timing chart of data sampling in the calibration apparatus of FIG. 1. (A) is a flowchart of the correction process determination process in the calibration apparatus of FIG. 1, (b) is a flowchart of a data sampling trigger interruption process. 3 is a flowchart of an A / D conversion end interrupt process in the calibration apparatus of FIG. 1. It is a flowchart of the signal processing in the calibration apparatus of FIG. It is a flowchart of the cylinder pressure calibration process in the calibration apparatus of FIG. FIG. 2 is a waveform diagram of various signals obtained by the calibration apparatus of FIG. 1.

Explanation of symbols

1 Engine 2 Combustion chamber (cylinder, cylinder)
3 In-cylinder pressure sensor 4 Vibration (acceleration) sensor 6 Peak ratio calculation unit 7 Calibration coefficient calculation unit 8 Calibration unit 9 ECU

Claims (2)

  An in-cylinder pressure sensor installed in the cylinder of the engine and a vibration (acceleration) sensor attached to the outside of the engine casing. The in-cylinder pressure detection signal output from the in-cylinder pressure sensor and the vibration sensor An in-cylinder pressure sensor calibration apparatus characterized in that an in-cylinder pressure detection signal output from the in-cylinder pressure sensor is calibrated based on a comparison with an integrated value of a vibration acceleration signal to be output. Calculates the calibration coefficient from the peak ratio calculation unit that calculates the ratio between the peak value of the in-cylinder pressure detection signal and the peak value of the integrated value of the vibration acceleration signal, and the peak ratio obtained at the initial stage and the peak ratio obtained at the time of calibration. The in-cylinder pressure sensor calibration apparatus according to claim 1, further comprising: a calibration coefficient calculation unit; and a calibration unit that multiplies the in-cylinder pressure detection signal by a calibration coefficient to obtain a calibrated signal of the in-cylinder pressure. .

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