JP2004340094A - Stroke distinction device for single cylinder four cycle internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stroke distinction device capable of determining state of stability of a single cylinder four cycle internal combustion engine and accurately distinguishing a stroke of an engine cycle. <P>SOLUTION: A distinction means distinguishes a stroke of the single cylinder four cycle internal combustion engine based on change of pressure in an intake pipe during engine cycle only when a detection means detect a stable state of engine load. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stroke determination device for a single-cylinder four-cycle internal combustion engine (hereinafter simply referred to as an engine).
[0002]
[Prior art]
As a device for determining the stroke of an engine, a device disclosed in Japanese Patent Application Laid-Open No. 2000-265894 is known. This device has a pulse generating means for generating a crank angle pulse and an intake pipe internal pressure value measuring means for measuring a plurality of times during two rotations of a crankshaft (crankshaft). It is to judge which stroke the top dead center of the crank is in on the basis of the magnitude relation.
[0003]
[Problems to be solved by the invention]
However, in the conventional device, when the operating condition of the engine is in a transient state, that is, when the rate of change of the engine speed is large (for example, during acceleration or deceleration), the intake pipe internal pressure value and the expansion / exhaust stroke in the intake / compression stroke are reduced. May be reversed with the intake pipe internal pressure value. In particular, during acceleration, since the intake pipe internal pressure value in the intake / compression stroke is close to the atmospheric pressure, it may take a larger value closer to the atmospheric pressure than the intake pipe internal pressure value in the immediately preceding expansion / exhaust stroke. is there. Therefore, if the stroke is determined only based on the magnitude relationship between the intake pipe internal pressure values of the preceding and following engine cycles, an erroneous determination may be made.
[0004]
Therefore, an object of the present invention is to provide a stroke determination device capable of determining a stable state of an engine and accurately determining a stroke of an engine cycle.
[0005]
[Means for Solving the Problems]
An engine stroke determination device according to the present invention includes: an intake pipe internal pressure detection unit that sequentially detects an intake pipe internal pressure of the engine as a PM value for each predetermined crank angle position; a detection unit that detects a stable state of the load of the engine; A stroke discriminating means for performing a stroke discrimination of the engine based on the change state of the PM value only when the stable state of the engine load is detected by the detecting means.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a stroke determination device according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the engine and the engine control unit. In the engine 10, an air-fuel mixture of air sucked from the intake pipe 12 and fuel injected from an injector 28 provided in the intake pipe 12 is sucked into the combustion chamber 20, and the sucked air-fuel mixture is burned and the piston 16 Reciprocate, and a crankshaft (crankshaft) 18 rotates. The air-fuel mixture burned in the combustion chamber 20 is discharged to the exhaust pipe 14 as exhaust gas. The intake pipe 12 is provided with a throttle 22 for controlling the amount of air to be taken in and an intake pipe internal pressure sensor 26. The throttle 22 is provided with a throttle opening sensor 24, which detects the opening of the throttle and generates a throttle opening signal St. Further, the intake pipe internal pressure sensor 26 outputs a pressure signal Sp corresponding to the intake pipe internal pressure.
[0007]
The rotating body 30 is provided on the crankshaft 18 so as to interlock with the crankshaft 18. A plurality of magnetic projections (not shown), which are a plurality of pieces to be detected, are provided on an outer peripheral portion of the rotating body 30. A crank angle sensor 32 is provided at a position near the rotation locus of the magnetic projection. The crank angle sensor 32 emits a detection signal Sd indicating that a magnetic protrusion has been detected in accordance with a change in magnetic flux due to the magnetic protrusion at every predetermined crank angle, for example, every 20 degrees of the crank angle.
[0008]
Signals emitted from the throttle opening sensor 24, the intake pipe internal pressure sensor 26, and the crank angle sensor 32 are supplied to an interface 52 of an ECU (electronic control unit) 50. In the interface 52, the throttle opening signal St and the pressure signal Sp are digitized by appropriate means, and the crank angle signal Sd is shaped into a crank angle pulse composed of a pulse train by a waveform shaping circuit (not shown) in the interface 52. Is done. The numerical data signal and the crank angle pulse from the interface 52 are supplied to the CPU 54 via the input / output bus 56. Therefore, the CPU 54 can execute a main routine described later for each predetermined crank angle.
[0009]
The CPU 54 transmits and receives a data signal or an address signal to and from a ROM (read only memory) 58, a RAM (random access memory) 60, an injector driving circuit 62, and a spark plug driving circuit 64 via an input / output bus 56. The injector drive circuit 62 is connected to the injector 28 and supplies a drive current Ij based on an injection command from the CPU 54. Similarly, the ignition plug drive circuit 64 is connected to the ignition plug 34 and supplies a drive current Ig based on an ignition command from the CPU 54. When the drive current Ig is supplied to the spark plug 34, a spark is emitted from the spark plug 34. This spark ignites the air-fuel mixture sucked into the combustion chamber 20, and the combustion of the air-fuel mixture starts an explosion stroke of the engine. The ROM 58 stores programs executed by the CPU 54 and the like, and the RAM 60 stores variable data and flag values used in the programs.
[0010]
FIG. 2 is a flowchart showing an engine stroke discrimination main routine executed each time the CPU 54 detects a crank angle pulse emitted from the crank angle sensor 32. In the engine stroke determination main routine, first, a PM value storage subroutine SS1 for storing the intake pipe internal pressure value (that is, the PM value) for each crank angle of the engine in the buffer RAM 60 of the CPU 54 is executed. The PM value storage subroutine SS1 stores the PM value in the buffer RAM 60, 2PMp indicating the PM value at the same crank angle position two rotations before the current crank angle position used in the subsequent steps of this routine, and the current crank angle. 1PMp indicating the PM value at the same crank angle position one rotation before the position and PMc indicating the current PM value are set. The operation of the PM value storage subroutine SS1 will be described later.
[0011]
In the engine stroke determination main routine, it is first determined whether or not 2PMp is 0 using 2PMp, 1PMp and PMc set in the PM value storage subroutine SS1 (step S1). In the initial state of the operation, since the initial value 0 is set in the memory of the buffer RAM 60, the 2PMp value is 0 until the crank rotates twice. That is, in step S1, it is determined whether PM value data for two rotations of the crank has been stored. Therefore, when 2PMp is 0 in step S1, the main routine is terminated as it is. If 2PMp is not 0 in step S1, an intake pipe pressure difference ΔPM2TDC is calculated using 2PMp and PMc given from the PM value storage subroutine (step S2). Here, ΔPM2TDC is calculated using the following equation.
[0012]
ΔPM2TDC = | PMc-2PMp |
Next, it is determined whether or not the calculated ΔPM2TDC value is larger than a predetermined stability threshold (Step S3). If ΔPM2TDC is smaller than the predetermined stability threshold, the engine operation state is determined to be stable, and the variable STc indicating the stability determination count is incremented by 1 (step S4). On the other hand, if ΔPM2TDC is larger than the predetermined stability threshold, the engine operation state is determined to be unstable, and the variable STc is decremented by 1 (step S5). Subsequently, it is determined whether or not STc is equal to or more than a predetermined number (step S6). If STc is equal to or more than the predetermined number, it is determined that the engine operation state is sufficiently stable, and the subsequent engine stroke confirmation PM value search subroutine SS2 is executed. On the other hand, if STc has not reached the predetermined number, it is determined that the engine operating state is not sufficiently stable, and the routine ends. In the determination in step S6, it is determined whether or not STc is equal to or more than a predetermined number within a certain time, or STc is determined to be a predetermined number during the execution of a predetermined routine by using another counter (not shown). Determining whether or not the above has been reached can be added. After executing the stroke confirmation PM value search subroutine SS2, it is subsequently determined whether or not the current crank position number is a predetermined number (step S7). The predetermined number can take an arbitrary number corresponding to an arbitrary position during one rotation of the crank. If the current crank position number is the predetermined number, the process proceeds to the engine stroke determination subroutine SS3, and after executing the subroutine, returns to the main routine and ends the routine. If the current crank position number is not the predetermined number, the engine stroke determination main routine ends.
[0013]
The stroke confirmation PM value search subroutine SS2 is a routine for setting some variables used in the subsequent engine stroke determination subroutine SS3. The operation of the stroke confirmation PM value search subroutine SS2 will be described later.
FIG. 3 is a flowchart showing the PM value storage subroutine SS1. In the PM value storage subroutine, first, the current intake pipe internal pressure value PM is read (step S31). Next, the PM1Pn value stored in the buffer RAM 60 is overwritten on PM2Pn (step S32). Here, n is an engine stage number represented by a crank angle pulse, and is, for example, an integer in the range of 1 to 16 with an initial value of 1. Subsequently, the PMCn value stored in the buffer RAM 60 is overwritten on PM1Pn (step S33), and the PM value read in step S31 is overwritten on PMCn (step S34). For example, when n = 1, in step S32, the value stored in PM1P1 is overwritten on PM2P1. Subsequently, in step S33, the value stored in PMC1 is overwritten on PM1P1, and in step 34, the read current PM value is overwritten on PMC1. By executing such an operation, the current PM value is stored in PMCn, and the PM value before one rotation of the crank and the PM value before two rotations of the crank are stored in PM1Pn and PM2Pn, respectively.
[0014]
Next, the current PM2Pn value is set to 2PMp (step S35). Subsequently, the current PM1Pn value is set to 1 PMp (step S36), and the current PMCn value is set to PMc (step S37). Next, it is determined whether or not n has reached a predetermined number, that is, 16 (step S38). If n has not reached the predetermined number, n is increased by 1 (step S39), and the subroutine ends. On the other hand, if n has reached the predetermined number, n is returned to 1 (step S40), and the subroutine ends. By using such a subroutine, it is possible to set and store the PM value PMc at the current crank rotation, the PM value 1 PMp before one rotation of the crank, and the PM value 2PMp before two rotations of the crank.
[0015]
FIG. 4 is a flowchart showing a process confirmation PM value search subroutine SS2. In the process confirmation PM value search subroutine SS2, first, it is determined whether or not F_CYC is 1 (step S51). F_CYC is a flag value indicating whether or not the engine stroke has already been determined, and is 1 if the engine stroke has already been determined, and 0 if not. Therefore, if F_CYC is not 1 in step S51, it is determined that the engine stroke has not been determined, and the routine ends. On the other hand, when it is determined in step S51 that F_CYC is 1, it is determined whether or not the crank angle position is the engine stroke reference position (step S52). The engine stroke reference position is a reference position when four strokes (intake, compression, expansion, exhaust) of one engine cycle of a four-cycle engine are defined as one unit, and in this embodiment, is a start position of the intake stroke. .
[0016]
If it is determined in step S52 that the crank angle position is not the engine stroke reference position, it is determined whether or not ENGDTC is 0 (step S53). ENGDTC represents a classification number when the engine stroke is classified into an “intake / compression stroke” and an “expansion / exhaust stroke”, and is 0 for an intake / compression stroke, and 1 for an expansion / exhaust stroke. Become. Therefore, when ENGDTC is determined to be 0 in step S53, it is determined whether or not the current PM value PMc is smaller than PMLOW as the engine is in the intake / compression stroke (step S54). Here, PMLOW is the minimum value of the intake pipe pressure detected during the main routine operation, that is, the minimum value of the intake pipe pressure during the intake / compression stroke. If PMc is smaller than PMLOW, the current PMc value is overwritten and updated with PMLOW (step S55).
[0017]
Subsequently, the current crank position number is overwritten and updated with PMPKSTG (step S56), and the subroutine ends. Here, PMPKSTG is a variable that stores the crank position number at which the above-mentioned PMLOW is detected. If it is determined in step S53 that ENGDTC is not 0, it is determined whether or not the current crank position number matches the PMPKSTG number (step S57). If the current crank position number matches PMPKSTG, the PMc value is overwritten and updated to PMHIGH (step S58), and the subroutine ends. Here, PMHIGH is the maximum value of the intake pipe internal pressure detected so far. If it is determined in step S57 that the current crank position number does not match PMPKSTG, the subroutine ends.
[0018]
On the other hand, if the crank angle position is the engine stroke reference position in step S52, the current PMc value is overwritten and updated to PMLOW (step S59), and similarly, the PMc value is overwritten and updated to PMHIGH (step S60). Subsequently, the current crank position number is overwritten and updated with PMPKSTG (step S61), and the subroutine ends. Through the steps S59 to S61, the reference value of the PM value at the start position of the intake stroke is given.
[0019]
FIG. 5 is a flowchart showing the engine stroke determination subroutine SS3. In the engine stroke determination subroutine SS3, first, it is determined whether or not F_CYC is 1 (step S71). If F_CYC is not 1, it is determined that the engine stroke has not been determined, and it is determined whether or not the current PM value PMc is larger than the PM value 1 PMp one rotation before (step S72). If PMc is greater than 1 PMp, the intake pipe pressure difference ΔPM1TDC is calculated using PMc and 1PMp (step S73). Here, ΔPM1TDC is calculated using the following equation.
[0020]
ΔPM1TDC = PMc-1PMp
Next, it is determined whether the calculated ΔPM1TDC value is larger than a predetermined threshold value TH1 (Step S74). If ΔPM1TDC is larger than TH1, it is determined that the engine stroke is the expansion / exhaust stroke, and the variable ENGDTC is set to 1 (step S75). Subsequently, the flag value F_CYC indicating that the engine stroke has been determined is set to 1 (step S76), and the subroutine is terminated. If it is determined in step S72 that PMc is smaller than 1 PM, and if it is determined in step S74 that .DELTA.PM1TDC is smaller than TH1, it is determined that the engine stroke is unknown or cannot be determined, and the flag value F_CYC is set to 0 (step S77). ), End the subroutine.
[0021]
On the other hand, when it is determined in step S71 that F_CYC is 1, it is determined whether ENGDTC is 1 or not, that is, whether the engine stroke is an expansion / exhaust stroke (step S78). If ENGDTC is not 1, the engine stroke is not confirmed, the current F_CYC value and ENGDTC value are maintained (step S79), and the subroutine ends. In step S78, if ENGDTC is 1, it is determined whether or not the PMHIGH value set in the stroke confirmation PM value search subroutine SS2 is equal to or greater than the PMLOW value (step S80). If PMHIGH is equal to or higher than PMLOW, an intake pipe pressure difference ΔPM1TDC is calculated using PMHIGH and PMLOW (step S81). Here, ΔPM1TDC is calculated using the following equation.
[0022]
ΔPM1TDC = PMHIGH−PMLOW
Next, it is determined whether or not the calculated ΔPM1TDC value is greater than a predetermined threshold value THa (step S82). If ΔPM1TDC is smaller than THa, then it is determined whether ΔPM1TDC is larger than a predetermined threshold THb (step S83). If ΔPM1TDC is smaller than THb, it is determined that the engine stroke is unknown or cannot be determined, the flag value F_CYC is set to 0 (step S84), and the subroutine ends. If it is determined in step S80 that PMHIGH is smaller than PMLOW, and if it is determined in step S83 that ΔPM1TDC is greater than THb, the engine stroke is not confirmed, and the flow proceeds to step S79 to go to the current F_CYC value and ENGDTC. Keep the value and exit the subroutine. If it is determined in step S82 that ΔPM1TDC is larger than THa, it is determined that the engine stroke is the expansion / exhaust stroke, and the variable ENGDTC is set to 1 (step S85). Subsequently, the flag value F_CYC indicating that the engine stroke determination has been performed is set to 1 (step S86), and the subroutine ends.
[0023]
By executing such a subroutine, when the engine stroke is not determined, that is, when F_CYC is 0, the engine stroke is determined to be the expansion / exhaust stroke through steps S71 to S76, and the engine stroke is determined. If the stroke has already been performed, that is, if F_CYC is 1, it is possible to confirm that the engine stroke is the expansion / exhaust stroke through steps S71 to S82 to S86.
[0024]
FIG. 6 shows the timing of the throttle opening, the engine stroke, the intake pipe internal pressure, and the crank angle pulse of the engine in a steady state. The crank angle pulse is detected 32 times in one engine cycle (intake, compression, expansion, exhaust). Therefore, the crank angle pulse is detected 16 times for each rotation of the crank. In the engine in the steady state, the throttle opening is substantially constant, and the intake pipe pressure repeatedly increases and decreases periodically every engine cycle. The engine stroke determination main routine shown in FIG. 2 is executed every time a crank angle pulse is detected, but is performed in step S3 because the difference between the current PM value and the PM value two revolutions before the crank is small. The determination is always in a stable state. For example, if A2 is the current crank angle position, A1 indicates the crank angle position two rotations before the crank and B1 indicates the crank angle position one rotation before the crank. At this time, the absolute value of the difference between the PM value at A1 and the PM value at A2, which is ΔPM2TDC, is almost 0 or a very small value, and is determined to be smaller than the predetermined stability threshold.
[0025]
Assuming that the predetermined position numbers for the determination performed in step S7 are A1, B1, A2, and B2, respectively, as one example, the case where the current crank angle position is A2 and the engine stroke is not determined, that is, F_CYC is 0 In the subroutine SS2 for PM value search for process confirmation, the subroutine is terminated while maintaining the variable data as it is by the determination in step S51. In the engine stroke determination subroutine SS3, the process proceeds from step S71 to step S72. Here, from FIG. 6, since the intake pipe internal pressure at PMc, that is, at A2 is smaller than the intake pipe internal pressure at 1PMp, that is, at B1, the process proceeds to step S77, and the engine stroke is not determined, that is, F_CYC is set to 0, and the routine ends. As another example, when the current crank angle position is B2 and F_CYC is 0, the process proceeds from step S71 to step S72 in the engine stroke determination subroutine SS3. Here, since the intake pipe internal pressure at PMc, ie, B2, is much higher than 1 PMp, ie, the intake pipe internal pressure at A2, the process proceeds to steps S73 to S76, where ENGDTC and F_CYC are set to 1 respectively. That is, it is determined that the current engine stroke is the expansion and exhaust stroke.
[0026]
If the current crank angle position is B2 and both F_CYC and ENGDTC are 1, in the stroke confirmation PM value search subroutine SS2, the process proceeds to steps S51 to S58, and the crank position number of PMPKSTG (for example, this time B2 ) Is set to PMHIGH. Subsequently, in the engine stroke determination subroutine SS3, the process proceeds to steps S71 to S80. At this time, since PMLOW is the minimum value of the intake pipe internal pressure at the previous crank angle position (for example, the intake pipe internal pressure value at A2, see FIG. 6), the process proceeds to steps S80 to S82. Here, ΔPM1TDC calculated in step S81 becomes larger than the predetermined threshold value THa, and the process proceeds to step S85 and thereafter to set ENGDTC and F_CYC to 1 respectively. That is, it is confirmed that the current engine stroke is the expansion and exhaust stroke.
[0027]
FIG. 7 shows, as another example, the throttle opening of the engine, the engine stroke, the intake pipe internal pressure, and the timing of the crank angle pulse when the acceleration, that is, the throttle opening is increased during the expansion stroke. In an engine in an accelerated state, the engine speed increases with an increase in the throttle opening, so that the intake pipe internal pressure increases from the steady state up to that time, and does not show a periodic increase or decrease. At this time, the engine stroke determination main routine SS3 determines a stable countdown, that is, an unstable state in the determination in step S3. For example, if the current crank angle position is A2, PMc becomes the PM value at A2, and 2PMp becomes the PM value at A1. Therefore, ΔPM2TDC becomes a large value and exceeds the stability threshold value in step S3. Further, the PM value at the crank angle position near A2 is also much larger than the PM value two rotations before, so that the main routine determines that the state is unstable even in the interrupt processing before and after A2. In such a case, the engine stroke determination device of the present invention does not execute the stroke determination by decrementing the stability counter STc, and is controlled so that the system does not erroneously determine the engine operation state.
[0028]
By using the device having the above configuration, it is possible to correctly determine the engine stroke of the engine regardless of whether the operating state of the engine is a steady state or a transient state (acceleration / deceleration state).
[0029]
【The invention's effect】
As is clear from the above, the engine stroke determination device according to the present invention can avoid erroneous determination in an unstable state of the engine load.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an engine and an engine control unit.
FIG. 2 is a flowchart illustrating an engine stroke determination main routine.
FIG. 3 is a flowchart showing a PM value storage subroutine executed during an engine stroke determination main routine shown in FIG. 2;
FIG. 4 is a flowchart illustrating a stroke confirmation PM value search subroutine executed during an engine stroke determination main routine shown in FIG. 2;
FIG. 5 is a flowchart showing an engine stroke determination subroutine executed during the engine stroke determination main routine shown in FIG. 2;
FIG. 6 is a time chart showing a relationship among a throttle opening, an engine stroke, an intake pipe internal pressure, and a change in a crank angle pulse when the engine is in a steady state.
FIG. 7 is a time chart showing a relationship between a throttle opening, an engine stroke, an intake pipe internal pressure, and a change in a crank angle pulse when the engine is in a transient state, that is, in an acceleration state during an expansion stroke.
[Explanation of symbols]
10 engine 12 intake pipe 18 crankshaft 26 intake pipe internal pressure sensor 32 crank angle sensor 50 electronic control unit (ECU)
54 Central Processing Unit (CPU)

Claims (4)

A stroke discriminating device for a single cylinder 4 cycle internal combustion engine,
Intake pipe internal pressure detection means for sequentially detecting an intake pipe internal pressure of the four-cycle internal combustion engine as a PM value for each predetermined crank angle position;
Detecting means for detecting a stable state of the load of the four-cycle internal combustion engine;
Stroke discriminating means for performing stroke discrimination of the four-cycle internal combustion engine based on the change state of the PM value only when the stable state of the engine load is detected by the detecting means;
A stroke discriminating device comprising: When the difference between the PM value at the current crank angle position and the PM value at the same crank angle position as the crank angle position in the immediately preceding engine cycle is smaller than a predetermined threshold value, the detecting means stabilizes the engine load. 2. The travel determination device according to claim 1, further comprising a determination unit configured to determine the state. 2. The stroke determination device according to claim 1, wherein the determination unit determines the stroke of the four-cycle internal combustion engine based on a maximum value and a minimum value of a PM value in one engine cycle. 2. The stroke discriminating apparatus according to claim 1, wherein said discriminating means performs stroke discrimination of said four-cycle internal combustion engine only when said judging means has judged the engine load stable state a predetermined number of times or more.

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