JP2011185779A - Operation state measuring method of positive displacement machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for measuring the operation state of a positive displacement machine having no error even if the number of data is reduced by removing noise from a signal introduced into a computing unit. <P>SOLUTION: In the operation state measuring method of the positive displacement machine for determining components of signals related to a stroke cycle in the positive displacement machine in the operation state, and determining a signal showing the operation state by synthesizing them by the computing unit 17, the signal related to the stroke cycle is a signal subjected to two processing, namely, filtering processing by an LPF (low-pass filter) 14, and sampling processing for sampling in the gate width based on the TDC of combustion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for measuring the operating state of a positive displacement machine, and more particularly to a technique for simply measuring an in-cylinder pressure.

  With the rapid development of semiconductor technology, computer control of automobile engines has been widely performed. One purpose of such computer control is to improve fuel efficiency, and in order to do so, it is necessary to operate the engine as close as possible to the lean limit.

  However, when performing such engine control, there is a problem that the control is difficult because the lean limit itself, which is the control target, is greatly affected by the rotational speed, load, atmospheric conditions, and the like. In addition, when the dilution limit is exceeded, it is also a big problem that drivability and exhaust characteristics change suddenly due to increased combustion fluctuations and misfires. Therefore, in conventional engine control that focuses only on the air-fuel ratio, the control target is set to a richer side than the lean limit, and ideal control is often not performed.

  For this reason, in order to improve the control accuracy in the lean region while maintaining drivability and exhaust characteristics at a certain level, the indicated mean effective pressure IMEP that directly indicates the combustion state of the engine can be used as the engine control information. It would be beneficial and desirable.

The indicated mean effective pressure IMEP is defined as follows, where P is the in-cylinder pressure of the cylinder, V is the volume thereof, and Vs is the stroke volume.
IMEP = (1 / Vs) ∫Pdv (1)
Conventionally, in order to measure the in-cylinder pressure P, it is common to perform measurement by attaching a pressure sensor in the cylinder, and accuracy cannot be obtained. This pressure sensor is attached to a cylinder head of a cylinder structure (an assembly of a cylinder block and a cylinder head; the same applies in this specification), is inserted into the cylinder, and is placed in contact with the combustion gas.

  Further, IMEP is calculated by Expression (2) obtained by discretizing Expression (1).

ここに、Ｐ（ｊ）、Ｖ（ｊ）は１サイクル間で等間隔にｎ個サンプリングされた、基準としたクランク角から数えてｊ番目の圧力と容積をそれぞれ表わす。

Here, P (j) and V (j) represent the jth pressure and volume, respectively, counted from the reference crank angle, sampled n at equal intervals during one cycle.

  As described above, the conventional in-cylinder pressure is detected by a pressure sensor, but the cylinder head to which the pressure sensor is attached has a complicated structure with a number of intake valves, exhaust valves, plugs, etc. attached to each cylinder. Therefore, it is difficult to attach the pressure sensor to the cylinder head from the viewpoint of space coupling.

Japanese Patent Publication No. 8-20339 JP 2005-133694 A

  Therefore, a technology has been developed in which a sensor such as a force sensor or a strain gauge for detecting the behavior of the cylinder structure is attached to the outside of the cylinder structure, and an instantaneous pressure value of the in-cylinder pressure is obtained using a behavior signal from the sensor. (See Patent Documents 1 and 2).

  With this technology, a pressure sensor that contacts the combustion gas in the cylinder is not used, and a force sensor, gap sensor, and acceleration sensor that are not in contact with the combustion gas are externally attached to the cylinder structure, and are correlated with the in-cylinder pressure. Since the in-cylinder pressure is obtained on the basis of the behavior signal relating to the behavior of the cylinder structure, it is not necessary to attach a pressure sensor to the cylinder head, and the in-cylinder pressure and thus the indicated mean effective pressure are easily derived.

  However, the signal of the behavior of the cylinder structure detected by the external sensor is a signal in which many noises are superimposed in addition to the signal based on the in-cylinder pressure.

  Attempts have been made to reduce the number of data in order to speed up the derivation of the indicated average pressure, but when reducing the number of data, the influence of noise is particularly large, which causes errors, so the signal is calculated. It is desirable to remove as much noise as possible before putting it into the vessel, but no effective technology has been developed to date.

  The present invention has been made in view of the above circumstances, and is capable of measuring the operating state of a positive displacement machine with less error even when noise is removed from the signal introduced into the arithmetic unit and the number of data is reduced. It is intended to provide a method.

  The method of measuring the operating state of a positive displacement machine according to the present invention is a positive displacement type in which components of a signal related to a stroke cycle in a positive displacement machine in an operating state are obtained and a signal representing the operational state of a cylinder is obtained by synthesizing these components A method for measuring an operating state of a machine, wherein the signal related to the stroke cycle is a filtering process in a range including a gate width by an LPF (low pass filter) and a TDC (top dead center) of combustion. The signal is characterized by being a signal that has undergone two processes of sampling processing and sampling processing.

  According to the present invention, the signal related to the stroke cycle of the positive displacement machine in the operating state is reduced in noise by the filtering process by the low-pass filter, and in the gate width based on the TDC of combustion, Since a signal that is less affected by noise is sampled and input to the arithmetic unit after the sampling process is performed, an operation with less error can be achieved even if the number of signals is reduced when deriving a signal representing the operating state of the machine, such as IMEP. Enable.

  Further, if the sampling process is further performed on the signal whose noise has been reduced by the low-pass filter, the noise can be removed and the operation with less error can be performed even if the configuration of the apparatus is simplified. That is, since the signal processed by the low-pass filter is simplified by cutting the high frequency region, and part of the signal is further extracted by the gate and processed, the amount of calculation processing can be reduced.

  In addition, if a signal that is less influenced by noise is cut out by sampling processing and then further filtered, even if the signal amplitude decreases or the phase shifts due to low-pass filtering, the calculation of the arithmetic unit is corrected. Therefore, it is possible to derive a signal representing an operating state with less error. In other words, it is possible to reduce the processing amount by passing only the waveform cut and extracted by the gate through the low-pass filter, and further reduce the calculation amount of the arithmetic unit by processing only the waveform simplified by the low-pass filter. In addition, since the LPF frequency correction can be performed on the IMEP calculation result, a signal having a higher correlation with the actual operation state can be obtained.

  Further, if the basic waveform and its harmonic components are used as signal components related to the stroke cycle, it is possible to calculate and derive an operating state with less error.

  Further, if the signal representing IMEP is used as the signal representing the operating state, IMEP with a small error is directly calculated, so that a signal representing a desired operating state for ideal control of the positive displacement machine can be obtained. .

  Further, if the signal subjected to the two processes of the sampling process and the filtering process is A / D converted and then subjected to a synthesis operation, the burden on the arithmetic device can be reduced.

  Furthermore, if the correction of the filtering process is performed in the synthesis process, after extracting a signal with a small influence of the noise sampled by the sampling device, the signal is further filtered to remove the noise. Even when the amplitude of the signal is reduced or the phase is shifted due to the filtering of the pal filter, the calculation of the calculation device is always corrected, and the signal representing the operation state with less error can be derived. That is, it is possible to reduce the amount of processing by the low-pass filter by passing only the waveform cut and extracted by the gate through the low-pass filter, and further processing only the waveform simplified by the low-pass filter, thereby reducing the amount of computation of the arithmetic unit. Further, since the LPF frequency correction can be performed on the IMEP calculation result, a higher correlation can be obtained.

The longitudinal section explanatory view showing the sensor device on a structure. Plane explanatory drawing which shows the sensor apparatus on a cylinder structure. The graph which shows the relationship between Equivalent (IMEP) _force and (IMEP) ₀ . The block diagram which shows a signal processing arithmetic unit. The graph which shows the signal processed with the signal processing arithmetic unit. The block diagram which shows a signal processing arithmetic unit. The graph which shows the signal processed with the signal processing arithmetic unit. (IMEP) A graph showing the relationship between _force and (IMEP) ₀ . (IMEP) A graph showing the relationship between _force and (IMEP) ₀ . (IMEP) A graph showing the relationship between _force and (IMEP) ₀ .

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

  First, the case where the present invention is applied to a single cylinder engine will be described. 1 and 2 showing the position of the sensor on the cylinder structure, the sensor device 1 is used when the engine operating state measuring method of the present invention is carried out, and is a behavior sensor attached to the cylinder structure 2 by an external attachment. 3 is provided. The cylinder structure 2 is a combination of a cylinder block 4 and a cylinder head 5, and the cylinder block 4 and the cylinder head 5 are fixed with bolts 7 with a gasket 6 interposed therebetween.

  The behavior sensor 3 is a sensor that detects the behavior of the cylinder structure 2. The types of behavior that occur in the cylinder structure 2 that is the object of detection include, for example, a change in force, a change in the gap (gap) between the cylinder block 4 and the cylinder head 5, and a gap between the cylinder block 4 and the cylinder head 5. The force sensor 3a for detecting the force corresponding to each detection target is provided with the cylinder block 4 or the gasket gap. 8, a gap sensor 3b for detecting a gasket gap 8 is particularly preferably attached to a bolt for fastening the cylinder block and the cylinder head, and a gap sensor for detecting a gap between the cylinder block 4 and the cylinder head 5 is attached. Is installed in the gasket gap 8 or an acceleration sensor for detecting acceleration. 3c is attached to the cylinder block 4, a gap sensor 3b is attached to the cylinder block to detect deformation of the cylinder block, and an acceleration sensor 3c is attached to the cylinder head to detect acceleration acting on the cylinder head. ing. Each sensor 3a, 3b, 3c is used alone or in combination with other sensors, and is selected and used as necessary. In addition, the attachment position of the behavior sensor 3 is not restricted to what is shown in FIG. 1, FIG.

The behavior of the cylinder structure 2, that is, the force, gap, acceleration, or deformation of the cylinder structure 2 acting on the cylinder structure 2 is detected. In the four strokes of intake, compression, explosion, and exhaust in one cycle of the engine, the force, gap, acceleration and deformation in the cylinder structure have a correlation with the in-cylinder pressure. Therefore, the signal processor 11 uses the signals of the sensors as original signals. , 11b to obtain a signal related to the stroke cycle, which is further computed by the computing device 17 to derive an in-cylinder pressure instantaneous value or an indicated mean effective pressure, which is a signal representing the operating state of the cylinder.
For example, the signal processing arithmetic device 11 shown in FIG. 4 can be used.

First embodiment

The signal processing arithmetic device 11 according to the first embodiment includes a low-pass filter 14, an analog switch 15, and an A / D converter 16 in order between the input unit 12 and the output unit 13, and further downstream of the signal processing device 11. Is provided with an arithmetic unit 17.

  A cutoff controller 18 that controls the cutoff of the low-pass filter 14 is connected to the low-pass filter 14, and an F / V converter 21 is connected to the cutoff controller 18.

  The F / V converter 21 determines a cutoff of the low-pass filter 14 based on a clock (ECU) signal and inputs the cut-off to the low-pass filter 14. The cut-off of the low-pass filter 14 can be determined according to the engine speed.

A gate set (Gate Set) controller 22 is connected to the analog switch 15. A gate set controller 22 receives a TDC signal and a clock (ECU) signal, determines a gate width in the analog switch 15, and inputs the gate width to the analog switch 15. The gate width is determined by, for example, a predetermined angle (gate angle) before and after TDC. The A / D converter 16 performs A / D conversion on the output signal of the analog switch 15 based on a TDC signal or a clock (ECU) signal and outputs the result. The arithmetic unit 17 calculates the output of the A / D converter 16 and derives and outputs the instantaneous value of the in-cylinder pressure and the IMEP of the engine cylinder. Regarding the indicated mean effective pressure, in the present invention, the fundamental wave (amplitude C ₁ , phase φ ₁ ), second harmonic in the above-mentioned instantaneous value of the in-cylinder pressure of the signal related to the stroke cycle sampled at an angle related to the stroke cycle. The wave ((amplitude C ₂ , phase φ ₂ ) is taken out and calculated by the arithmetic unit 17 using the equation (3) or the equation (4).

ここに、Ｋ、ｈはエンジン諸元より定まる定数、ｎを１サイクル間のサンプルデータ数としてｍ＝ｎ／２である。またＰ（３６０ｊ／ｎｈ）、Ｐ（−３６０ｊ／ｎｈ）は、燃焼のＴＤＣを基準として前後３６０ｊ／ｎｈ度における上述の筒内圧瞬時値を表わす。

Here, K and h are constants determined from engine specifications, and m = n / 2 where n is the number of sample data in one cycle. P (360j / nh) and P (-360j / nh) represent the above-described instantaneous values of the in-cylinder pressure at 360 j / nh degrees before and after the combustion TDC.

FIG. 3 shows an equivalent calculated from the equation (3) from the indicated mean effective pressure (IMEP) ₀ obtained by the equation (2) based on the signal from the in-cylinder pressure sensor currently performed and the above-mentioned instantaneous value of the in-cylinder pressure (force sensor). (IMEP) The relationship with _force (subscript _force represents a force sensor) is shown. It can be seen that the two are in a proportional relationship.

  The IMEP derivation operation by the signal processing arithmetic unit 11 configured as described above is as follows. The original signal detected by the external behavior sensor 3 (3a, 3b, 3c, etc.) enters the signal processing device 11 from the input unit 12, and is first removed from the noise by the low-pass filter 14, and then the noise is removed. The signal is sampled by the analog switch 15 only at a predetermined gate angle and taken in, and this signal is A / D converted by the A / D converter 16 to obtain a signal related to the stroke cycle. A signal indicating the operating state of the cylinder, for example, IMEP is derived.

The change of the signal processed by the signal processing arithmetic unit 11 is shown in FIG.
FIG. 5 shows an in-cylinder pressure signal (PC00015.DAT) detected by the pressure sensor and a force sensor source signal of the behavior of the cylinder structure detected by the force sensor. Although both signals have a correlation, it can be seen that noise is superimposed on the signal detected by the force sensor. In order to derive the instantaneous value and IMEP of the in-cylinder pressure from the force sensor original signal, the original signal is first input to the signal processing arithmetic unit 11 and passed through the low-pass filter 14. This obtains a filtered signal (force sensor (LPF2-3)) with reduced noise.

Next, the filtered signal (force sensor (LPF2-3)) is input to the analog switch 15, and only the gate width signal (force sensor (LPF2-3) Gate ± 120 deg) based on TDC is cut out and sampled. . Since this cut-out signal (force sensor (LPF2-3) Gate ± 120 deg) (signal related to the stroke cycle) is only the signal portion before and after the TDC, the influence of noise is a very small portion.
This gate width is ± 120 deg before and after the TDC in the illustrated embodiment. This signal ((force sensor (LPF2-3) Gate ± 120 deg)) is input to the A / D converter 16 for A / D conversion, and is calculated by the arithmetic unit 17 to indicate the operating state of the cylinder, for example, cylinder The internal pressure instantaneous value and IMEP are calculated and derived.

In the case of the first embodiment, 1) the correlation coefficient is slightly lower than that in the case of Gate Set (no LPF) at N = 720. However, N = 720 to 12 and the correlation coefficients are almost the same (ρ = 0.972 to 0.9761).
2) The slope (with cutting edge) tends to increase as N decreases to 0.5095 at N = 720, 0.5944 at N = 12, and N decreases.

  In the case of the first embodiment, since the signal processed by the low-pass filter is simplified by cutting the high-frequency region and a part of the signal is further extracted to the gate, the amount of calculation processing is reduced. Can be reduced.

Second embodiment

  FIG. 6 shows a signal processing arithmetic device 11b according to the second embodiment of the present invention. The signal processing arithmetic unit 11b includes an analog switch 15, a low-pass filter 14, and an A / D converter 16 between the input unit 12 and the output unit 13, and further includes an arithmetic unit 17 downstream of the signal processing arithmetic unit 11b. Although the same as the signal processing arithmetic unit 11 of the first embodiment, an analog switch 15 for sampling the original signal within a predetermined gate width is provided upstream of the low-pass filter 14 that performs signal filtering. It differs from the signal processing arithmetic unit 11 of the first embodiment. In connection with this, the calculation of the calculation device 17 may include a low-pass filter (LPF) correction, and an LPF correction value calculation means 19 for calculating an LPF correction value for this may be provided.

  A gate set (Gate Set) controller 22 is connected to the analog switch 15. A gate set controller 22 receives a TDC signal and a clock (ECU) signal, determines a gate width in the analog switch 15, and inputs the gate width to the analog switch 15. The gate width is determined by, for example, a predetermined angle (gate angle) before and after TDC.

  A cutoff controller 18 that controls the cutoff of the low-pass filter 14 is connected to the low-pass filter 14, and an F / V converter 21 is connected to the cutoff controller 18.

  The F / V converter 21 determines a cutoff of the low-pass filter 14 based on a clock (ECU) signal and inputs the cut-off to the low-pass filter 14. The cut-off of the low-pass filter 14 can be determined according to the engine speed.

  The A / D converter 16 performs A / D conversion on the output signal of the analog switch 15 based on a TDC signal or a clock (ECU) signal and outputs the result. The arithmetic unit 17 calculates the output of the A / D converter 16 and derives and outputs the instantaneous value of the in-cylinder pressure and the IMEP of the engine cylinder.

  The IMEP derivation operation in the signal processing arithmetic device 11b configured as described above is as follows. The original signal detected by the external behavior sensor (3a, 3b, 3c, etc.) enters the signal processing arithmetic unit 11b from the input unit 12, samples the signal by the analog switch 15 only at a predetermined gate angle, and then takes it in. Noise is reduced through a low-pass filter 14, and this signal is A / D converted by an A / D converter 16 to obtain a signal related to a stroke cycle, which is then calculated by an arithmetic unit 17 to determine the operating state of the cylinder. A representative signal, for example IMEP, is derived.

  The change of the signal processed by the signal processing arithmetic unit 11b is shown in FIG. FIG. 7 shows an in-cylinder pressure signal (PC00015.DAT) detected by the pressure sensor and a cylinder structure behavior signal (force sensor) detected by the force sensor. Although both signals have a correlation, it can be seen that noise is superimposed on the signal detected by the force sensor. In order to derive the in-cylinder pressure instantaneous value and IMEP from the signal (force sensor) (original signal), first, the original data is input to the signal processing arithmetic unit 11b and input to the analog switch 15, and the gate width with respect to TDC is set as a reference. Only the signal (force sensor (Gate ± 120 deg)) is cut out and sampled. Since this cut out signal (force sensor (Gate ± 120 deg)) is only the signal portion before and after the TDC, it is a portion where the influence of noise is extremely small. This gate width is ± 120 deg before and after the TDC in the illustrated embodiment.

  Next, the sampled signal (force sensor (Gate ± 120 deg)) is passed through the low-pass filter 14. As a result, a signal (force sensor (Gate ± 120 degLPF2-3)) with further reduced noise is obtained. This signal ((force sensor (Gate ± 120 degLPF2-3))) is input to the A / D converter 16 and A / D converted to obtain a signal related to the stroke cycle. A signal representing the operating state of the engine, for example, an instantaneous value of the in-cylinder pressure and IMEP is calculated and derived.

In the case of the second embodiment, it is possible to reduce the processing amount by passing only the waveform cut and extracted by the gate through the low-pass filter, and further processing only the waveform simplified by the low-pass filter. The calculation amount of the arithmetic unit can be reduced, and furthermore, since the LPF frequency correction can be performed on the IMEP calculation result, a higher correlation can be obtained.
1) Even if N decreases due to LPF correction, N = 720, the same level as the correlation coefficient without Gate Set and LPF.
2) Correlation coefficients are N = 720, Gate ± 120 deg, no LPF ρ = 0.9971, N = 720-12, ρ = 0.9917-0.9919 (N = 18), 0.9732 (N = 12), even if N decreases, the level is the same as N = 720.
3) The slope (with a cutting edge) is approximately the same at 0.4144 when N = 720, 0.4068 when N = 18, and 0.4004 when N = 12.

(Influence of the number of samples N on the IMEP calculation result)
The influence of the number of samples N on the IMEP calculation result is shown in FIGS. 8 to 10 in comparison with the method using the signal processing operation devices 11 and 11b (this operation method) and the method not using them (conventional method).

  FIG. 8 shows the influence of the number of samples N (conventional method: N = 720 to 18, continuous 300 cycles). When the data of FIG. 8 is processed by the conventional method, the effect of the arithmetic gate is recognized at N = 720, but when N is reduced, the variation becomes large and the degree of correlation is extremely deteriorated. Therefore, when the number of samples is limited, such as an on-board engine control system, it is difficult to cope with the conventional method.

FIG. 9 shows IMEP (this calculation method) derived by the signal processing arithmetic unit 11 using the signal detected by the force sensor externally attached to the cylinder structure according to the first embodiment of the present invention and the detection signal by the pressure sensor. The relationship of IMPF ₀ (conventional method) derived using is shown. It can be seen that even when the number of data N decreases, both are in a good proportional relationship.

  FIG. 10 shows the influence of the number of samples N (conventional method N: 720 to 18, continuous 300 cycles). In the case of this calculation method, since the frequency component related to IMEP is clear, it is possible to take countermeasures by combining gate calculation, noise removal by a smoothing circuit, and correction of frequency characteristics of the circuit. As a result, the degree of correlation can be maintained at the same level as N = 720 even if it is reduced to N = 18 (sampling every 40 deg). Such signal processing is difficult with the conventional method, and can be said to be a feature of this calculation method. In FIG. 10, since 300 data per condition are plotted, symbols are difficult to distinguish.

  In the first and second embodiments, the A / D converter 16 is used to perform A / D conversion on the signal 23 that has undergone both the filtering process and the sampling process and then input the signal to the IMEP arithmetic unit. However, as another embodiment, the signal subjected to both processes can be calculated as an analog signal, and in this case, the A / D converter 16 is not used.

  According to the present invention, it is possible to obtain a method and apparatus for measuring the operating state of a positive displacement machine with less error even if the number of samples is reduced, and therefore it can be used for an on-board engine control system and the like.

DESCRIPTION OF SYMBOLS 1 Sensor apparatus 2 Cylinder structure 3 Behavior sensor 4 Cylinder block 5 Cylinder head 6 Gasket 7 Bolt 11, 11b Signal processing arithmetic unit 12 Input part 13 Output part 14 Low-pass filter 15 Analog switch 16 A / D converter 17 Calculation apparatus 18 Cut Off controller 19 LPF correction value calculation means 21 F / V converter 22 Gate set controller

Claims (7)

  A method for measuring an operating state of a positive displacement machine that obtains components of a signal related to a stroke cycle in a positive displacement machine in an operating state and obtains a signal representing an operational state of a cylinder by synthesizing these components, wherein the stroke cycle The signal related to is a signal that has been subjected to two processes, a filtering process including a gate width by LPF (low pass filter) and a sampling process for sampling within the gate width based on the TDC of combustion. A method for measuring the operating state of a positive displacement machine.   2. The method for measuring an operating state of a positive displacement machine according to claim 1, wherein the signal related to the stroke cycle is filtered and then the sampling is performed.   2. The method for measuring an operating state of a positive displacement machine according to claim 1, wherein the sampling process is performed on a signal related to the stroke cycle, and then the filtering process by the low-pass filter is performed.   4. The operating state measurement of the positive displacement machine according to claim 1, wherein the component of the signal related to the stroke cycle is a fundamental wave component and a harmonic component of the fundamental wave component of the signal related to the stroke cycle. Method.   5. The method for measuring an operating state of a positive displacement machine according to claim 1, wherein the signal representing the operating state is a signal representing IMEP (indicated mean effective pressure).   6. The method for measuring the operating state of a positive displacement machine according to claim 1, wherein the synthesis processing is performed by A / D converting the signals subjected to the two processes.   The method of measuring an operating state of a positive displacement machine according to claim 1, wherein the filtering process is corrected in the synthesis process.

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