Patent Grant
7194898
The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2005-095600, filed on Mar. 29, 2005. The subject matter of these priority documents is incorporated by reference herein.
1. Field of the Invention
The present invention relates to a stroke determination unit, and to a method of measuring stroke in a 4-cycle internal combustion engine. More particularly, the present invention relates to a stroke determination unit and method, suitable for determining stroke in a multiple cylinder 4-cycle engine.
2. Description of the Background Art
In a conventional 4-cycle engine that has adopted an electronic fuel injection unit, stroke determination may be performed based on both the phase of an engine camshaft and the phase of a crankshaft. In Japanese Patent Laid-open no. Hei. 10-227252, a stroke determination unit is proposed that does not detect the phase of a camshaft, but instead, for a particular crankshaft phase, compares intake pressure detected at a current time and intake pressure detected at a prior period, and carries out stroke determination according to a magnitude relationship of the two. In this way, since it is not necessary to provide a sensor for detecting the camshaft phase inside a cylinder head of the engine, it is possible to make the engine smaller and lighter in weight.
However, with the technology disclosed in Japanese Patent Laid-open no. Hei. 10-227252 described above, stroke determination takes a long time to effect, because stroke determination is carried out based on a magnitude relationship of measured intake pressures obtained using an intake pressure sensor, taking a magnitude relationship for all intake pressures into consideration, from a low-speed region of an internal combustion engine to a high-speed region. Also, since the comparison of magnitude values is made for a particular point, it is difficult to improve noise suppression with respect to the influence of interference, such as noise on an electrical system.
The present invention is designed to solve the above described problems of the related art. In an illustrative embodiment hereof, the present invention provides a stroke determination unit and method for a 4-cycle engine in which stroke determination setting is simplified, and which is capable of improving suppression of the effect of electrical noise. The stroke determination unit and method hereof use intake pressure as a parameter, in combination with a reading from a crankshaft sensor.
In a first aspect of the present invention, a stroke determination unit for a multiple cylinder, 4-cycle engine, includes a crank angle detection device for detecting a phase of a crankshaft, and an intake pressure detection device for detecting intake pressures of cylinders provided with an intake pressure variation generating device. The intake pressure variation generating device causes variation so that an intake pressure waveform of at least one cylinder becomes different relative to the intake pressure waveforms of other cylinders.
The stroke determination unit also includes an intake pressure waveform combining device for combining detected intake pressure waveforms, a pattern recognition device for recognizing a pattern of the detected intake pressure waveform, and a stroke determination device for determining a stroke of each cylinder, based on the sensed crankshaft phase and a recognized pattern.
In a second aspect of the present invention, the pattern recognition device recognizes a pattern only in a specified crankshaft phase period.
In a third aspect of the present invention, the specified crankshaft phase period is set so that an inflection point of the combined intake pressure waveform is close to a start time of the specified crankshaft phase period.
In a fourth aspect of the present invention, the multiple cylinder engine is an engine timed to fire at regular intervals and having expansion strokes at equal spacing, and the intake pressure variation generating device does not add an intake pressure waveform for a particular cylinder to a combined intake pressure waveform.
In a fifth aspect of the present invention, detection of the intake pressure for the particular cylinder is not carried out, and fuel injection or ignition timing control is performed based on intake pressure detected for cylinders other than the particular cylinder.
In a sixth aspect of the present invention, the intake pressure variation generating device changes the sensitivity of the intake pressure detection for a particular cylinder in the intake pressure detection device arranged for each cylinder.
In a seventh aspect of the invention, the pattern recognition device identifies fluctuation in the combined intake pressure waveform for every crank pulse generation period as one of increase, decrease or change, and recognizes a pattern of the combined intake pressure waveform using the fluctuation result.
In an eighth aspect of the present invention, the pattern recognition device stores a plurality of intake pressure values including start time and end time of the specified crankshaft phase period, and recognizes a pattern of the combined intake pressure waveform from a relationship between the intake pressure values at the start time and the end time, and other intake pressure values within that range.
According to the first aspect of the invention, setting the same pattern from a low-speed region to a high-speed region is easy because, in contrast to a method where combined intake pressure values for particular phase of the crankshaft are compared, variation of a combined intake pressure waveform is recognized using a waveform pattern having continuity, and it is also possible to accurately determine engine stroke with improved suppression of electrical noise.
According to the second aspect of the invention, since only a pattern of a particular period having a feature is recognized in a combined intake pressure waveform, it is possible to reduce the computing load on a computer, due to the use of pattern recognition, as compared to a method that carries out recognition processing in all periods of the crankshaft.
According to the third aspect of the invention, since no stray curve points of the combined intake pressure waveform appear outside the specified crankshaft phase period, even if by some chance a delay arises at the time of detection of negative intake pressure, in cases such as where the crankshaft is rotating at high speed, there is no erroneous pattern recognition, and it is possible to carry out accurate stroke determination.
According to the fourth aspect of the invention, even with an engine timed to fire at regular intervals, it is possible to cause necessary variation for stroke determination in an intake pressure waveform without using a separate unit, etc.
According to the fifth aspect of the invention, since it is not necessary to provide an intake pressure detection device in a particular cylinder, it is possible to reduce the number of components and manufacturing steps.
According to the sixth aspect of the invention, it is possible to cause variation in the intake pressure waveform without the addition of a significant change to the intake pressure detection device provided for every cylinder.
According to the seventh aspect of the invention, since pattern recognition is carried out using recognition results for three simple fluctuating patterns, it is possible to carry out accurate stroke determination, with improved pattern recognition precision, in all engine operating states.
According to the eighth aspect of the invention, since fluctuation in intake pressure measurement values that are caused to be estimated due to the occurrence of noise etc. are ignored, it is possible to improve suppression of the effect of electrical noise and carry out accurate stroke determination.
Modes for carrying out the present invention are explained below by reference to an embodiment of the present invention shown in the attached drawings. The above-mentioned object, other objects, characteristics and advantages of the present invention will become apparent form the detailed description of the embodiment of the invention presented below in conjunction with the attached drawings.
Selected illustrative embodiments of the invention will now be described in some detail, with reference to the drawings. It should be understood that only structures considered necessary for clarifying the present invention are described herein. Other conventional structures, and those of ancillary and auxiliary components of the system, are assumed to be known and understood by those skilled in the art.
An intake pressure (Pb) sensor 4, corresponding to an intake pressure variation generating device, is constructed so as to detect combined intake pressure Pb. The combined intake pressure Pb is a combination of intake pressures P1, P2 and P3 generated in the first to third intake pipes 11a–11c, obtained by merging the other ends of the first to third capillaries 12a–12c. A second Pb sensor 13 for measuring intake pressure P4 generated in the intake pipe 11d of the fourth cylinder is connected to an end section of the capillary 12d. However, it is possible to omit this structure as long as it is possible to execute stroke determination on the basis of measurement values of the combined intake pressure Pb to carry out control for fuel injection and ignition timing.
The structure described above, in which a combined value of intake pressure is measured in only three of four cylinders, is advantageous for the following reason. If a combined value of intake pressure for all four cylinders generated in intake pipes of an engine timed to fire at regular intervals is measured, then in one full cycle of the engine (that is, two rotations of the crankshaft), an intake pressure waveform will be the same for the first crankshaft rotation and the second crankshaft rotation, and so there is nothing that can be used for stroke determination. This problem is avoided by measuring a combined value of intake pressure in only three of four cylinders.
With the intake pressure variation generating device of this embodiment, since an intake pressure value for the fourth cylinder is excluded, as will be clear from subsequent description, variation is imparted to the combined intake pressure Pb waveform for the first and second rotations of the crankshaft, and stroke determination is possible. In the case of a multiple cylinder engine where combustion intervals are different, since the intake pressure negative pressure waveform for each cycle is not periodic, it can be used as it is, or it is possible to impart variation to some cylinders or to impart new characteristics on the negative pressure waveform.
During engine operation, crank pulses from operation of the phase sensor pair, and an output signal of the Pb sensor 4 are input to an engine control unit (ECU) 5, together with other sensor signals and process signals.
The ECU 5 includes a phase detection section 501, corresponding to a crank angle detection device for detecting phase of the crankshaft based on the crank pulses, and a stage counter allocation section 502 for dividing one rotation of a crankshaft 1 by 13 at the output timing of the crank pulses and allocating stage numbers of “#1” to “#13” to respective phases (stages) of the crankshaft. The ECU 5 also includes a Pb pattern storage section 504, for storing variation patterns of the combined intake pressure Pb detected by the Pb sensor 4. The ECU 5 further includes a Pb pattern recognition section 505, corresponding to a pattern recognition device, for recognizing a Pb pattern by referencing data held in a stored Pb pattern map 506. The ECU 5 also includes a stroke determination section 503, corresponding to a stroke determination device, for determining stroke of the engine 1 based on stage count allocation results and Pb pattern recognition results. The ECU 5 controls an injection 6 of fuel by a fuel injector, and operation of an ignition unit 7, based on output timing of the crank pulses and stroke determination results.
Next, a method of stroke determination processing executed by the ECU 5 will be described, with reference to the flow chart of
In step S1, if a crank pulse is detected, then in step S2 it is determined whether or not a crank reference position is being defined. With respect to the crank reference position, as shown in the timing chart of
Returning to
In step S72, the value Pb0, which corresponds to a previously detected detection value for combined intake pressure Pb, is subtracted from Pb1, which corresponds to the current detection value for combined intake pressure, and then it is determined whether or not the difference between Pb1 and Pb0 is a specified value or greater. The specified value is a threshold value for determining whether or not there is change in the variation pattern, and is set taking into consideration the sensitivity of the Pb sensor.
If it is determined that Pb1−Pb0 is the specified value or greater, then in step S76 the variation pattern is determined to be increasing: upward (+1). Also, if it is determined in step S72 that Pb1−Pb0 is not the specified value or greater, processing advances to step S73, where it is determined whether or not Pb0−Pb1 is a negative specified value or greater. If Pb0−Pb1 is determined to be the negative specified value or greater the variation pattern is determined to be reducing: downward (−1) in step S75. In the event that the determination in steps S72 and S73 are negative, in step S74 the variation pattern is determined to be no change (0).
Continuing on, in step S77, the recognition results, that is, the variation patterns, are accumulated for each stage using a value of +1 to refer to an upward pattern, a value of −1 to refer t a downward pattern, and a value of 0 to refer to no change, and then processing then advances to step S78. In step S78, it is determined whether or not a stage count value is eleven, which is a stage count for terminating Pb pattern recognition. If the stage count is determined to be eleven in step S78, processing advances to step S79. In the event that the stage count is not eleven, processing returns to step S71, and the recognition processing of steps S71 to S78 is repeated until the stage count reaches eleven.
Next, Pb pattern matching processing of steps S79 and later will be described with reference to
Returning to
If the Pb pattern is defined as one of either “rising”, “upward peak” or “undetermined” as a result of the above described Pb pattern recognition processing, pattern recognition processing is terminated in step S84, and processing advances to step S8 of the main flow diagram of
As shown in the timing chart of
Returning to
In
In addition, selection of a start stage count period and a completion stage count period for Pb pattern recognition avoids a non-toothed section of the crank pulser rotor 2 for determining a reference position of the crankshaft, and takes into consideration stage count values which are not erroneously recognized as other Pb patterns, even if there is occurrence of slight delay in Pb detection time at times such as high speed operation of the engine. In
Referring to
Next, from among measurement values for the seven measured points, the initial measured value is designated E point, the final measured value is designated F point, and among the 5 point remaining after removing the E point and F point, the maximum value is defined as G point while the minimum value is defined as H point. At this time, in the event that the “final measured value” is larger than the “initial measured value”, and all “measurement values of the five remaining points” are between the “final measured value” and the “initial measured value”, the Pb pattern is recognized as “rising”. If this recognition condition is represented with an equation, it would become as follows:
if (F>E+10 mV) AND (G and H≧E−10 mV) AND (G and H≦F+10 mV)
The condition equation is stored in the Pb pattern map 506 within the ECU 5. Using the above-described method, with the example shown in
Next, Pb recognition for “upward peak” is carried out in the event that a “maximum value of the five remaining points” is larger than any of the “final measured value” and the “initial measured value”, namely, represented as an equation, (G>E+10 mV) AND (G>F+10 mV). Using the above described method, with the example shown in
As a result of the above described pattern recognition, it becomes possible to prevent erroneous Pb pattern recognition, even if contamination such as leakage due to noise in the electrical system etc. has a slight influence on the Pb sensor output values. In this embodiment, if attention is paid to the waveform using the combined intake pressure shown in
As has been described above, according to the present invention, since variation in a combined intake pressure waveform is recognized using a waveform pattern, suppression of the effect of electrical noise is improved and accurate stroke determination processing is made possible. Also, since only a pattern of a particular period having a feature is recognized in a combined intake pressure waveform, it is possible to reduce the computing load on a computer due to pattern recognition as compared to a method that carries out recognition processing in all periods of the crankshaft.
With the above described embodiments, a description has been given relating to application of the invention to a four-cycle multiple cylinder engine where all cylinders fire at regular intervals, but obviously it is also possible to apply the invention to a four cycle multiple cylinder engine having irregular firing intervals.
While a working example of the present invention has been described above, the present invention is not limited to the working example described above, but various design alterations may be carried out without departing from the present invention as set forth in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-095600 | Mar 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4889094 | Beyer et al. | Dec 1989 | A |
| 5321979 | Mc Kendry et al. | Jun 1994 | A |
| 6170322 | Yamazaki et al. | Jan 2001 | B1 |
| 6340020 | Yamazaki et al. | Jan 2002 | B2 |
| 6378358 | Hirakata et al. | Apr 2002 | B1 |
| 6575136 | Namari | Jun 2003 | B1 |
| 6935168 | Shimoyama | Aug 2005 | B2 |
| 20010010218 | Yamazaki et al. | Aug 2001 | A1 |
| 20020170346 | Shimoyama | Nov 2002 | A1 |
| 20050205057 | Yamashita | Sep 2005 | A1 |
| 20060116813 | Tsuyuguchi et al. | Jun 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 1609975 | Dec 2005 | EP |
| 10-227252 | Aug 1998 | JP |
| WO 2004013476 | Feb 2004 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20060218998 A1 | Oct 2006 | US |
