JPH0735751B2 - Crank angle detector for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction device for a detected value of a crank angle sensor that detects the position of a crankshaft in an internal combustion engine.

[Conventional technology]

In an internal combustion engine, it is necessary to know the crank angle for air-fuel ratio control and ignition timing control. Therefore, a crank angle sensor is provided. Various types of crank angle sensors are known, for example, a crankshaft,
Distributor shaft connected to the crankshaft is provided with a permanent magnet piece, and a magnetism detecting member composed of a Hall element or the like is provided so as to face the permanent magnet piece, and a pulse signal corresponding to the crankshaft position is obtained by a magnetic change. There is.

The crank angle sensor should be mounted so that its detected value corresponds exactly to the crank angle.
Some errors due to mounting tolerances will inevitably occur. Such an error makes the crank angle inaccurate,
The engine cannot be controlled ideally.

Therefore, in order to correct the error of the crank angle sensor, in JP-A-60-114734, attention is paid to the fact that the compression pressure peak appears at the top dead center during motoring when decelerating fuel is cut, and the pressure peak position and the reference A technique for correcting the signal from the crank angle sensor based on the difference from the crank angle signal is disclosed.

[Problems to be solved by the invention]

In the prior art, in order to detect the peak of the compression pressure, it is necessary to detect the pressure for each minutely divided angle (for example, 1 °). Therefore, it is difficult to read the pressure on the high rotation side, and even if the pressure can be read, there is a problem that the calculation process is complicated or the calculation is difficult.

An object of the present invention is to provide a crank angle detecting device capable of performing accurate correction without making the division angle fine.

[Means for solving problems]

According to the invention, as shown in FIG. 1, in an internal combustion engine, a crank angle detector 1 for generating a signal according to angular positions of a crankshaft at a plurality of intervals and a means 2 for detecting a compression pressure. A means 3 for calculating a difference in compression pressure between a pair of crank angle positions close to the piston top dead center, a means 4 for detecting the motoring time of the internal combustion engine, and the pressure for the motoring time. Means 5 for calculating the deviation amount of the crank angle corresponding to the pressure difference calculated by the compression pressure difference calculating means 3 based on the relationship between the difference and the deviation angle of the detection signal from the crank angle detector 1, and the compression pressure for the crank angle. Means 6 for detecting an engine operating condition that influences asymmetry across the top dead center of the curve, and the operating condition detection based on a predetermined relationship between the operating condition and the correction amount of the deviation amount. A means 7 for calculating a correction amount in the detected operating conditions by stages, a crank angle detecting device is provided comprised of means 8 which corrects the shift amounts based on the calculated correction amount.

[Action]

The crank angle detector 1 generates a signal corresponding to the angular positions of the crankshaft of the internal combustion engine at a plurality of intervals, the compression pressure detecting means 2 detects the compression pressure of the internal combustion engine, and the motoring detecting means 4 detects internal combustion. When the engine enters the motoring state, the operating condition detecting means 6 detects the engine operating condition that affects the asymmetry across the top dead center of the compression pressure curve with respect to the crank angle.

The compression pressure difference calculation means 3 calculates the difference in compression pressure between a pair of crank angle positions that are close to the piston top dead center and are close to the piston top dead center.

When the motoring detection means 4 detects that the internal combustion engine has entered the motoring state, the deviation amount calculation means 5
Based on the relationship between the pressure difference calculated by the compression pressure difference calculation means 3 and the deviation angle of the detection signal from the crank angle detector, the deviation amount of the crank angle corresponding to the pressure difference calculated by the compression pressure difference calculation means 3 is calculated. To do.

The correction amount calculating means 7 calculates the correction amount under the detected operating condition based on a predetermined relationship between the operating condition detected by the operating condition detecting means 6 and the correction amount of the deviation amount.

The correcting means 8 corrects the shift amount calculated by the shift amount calculating means 5 based on the correction amount calculated by the correction amount calculating means 7. [Example] FIG. 2 shows an internal combustion engine in the embodiment. Is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a cylinder head, 18 is a combustion chamber, 20 is an intake valve,
21 is an intake port, 22 is a spark plug, 23 is a fuel injector,
24 is a distributor, 26 is an ignition coil, and 27 is an igniter. Intake port 21, intake pipe 28, surge tank
It is connected to the throttle valve 30 via 29. In the combustion chamber 18,
A pressure sensor 31 for detecting the combustion pressure is arranged.
First crank angle sensor 32, second crank angle sensor 33
Is installed in the distributor 24. On the other hand, the first magnet member 36 and the second magnet member 38 are provided on the distribution shaft 34 of the distributor. The first magnet member 36 has a magnetized portion at one position on its circumference, and the first crank angle sensor 32 as a Hall element outputs a pulse signal for each rotation of the distribution shaft (corresponding to 720 ° CA). And is configured to generate a reference signal, particularly at compression top dead center. The second magnet unit 38 has a plurality of magnetized portions at equal intervals on its circumference and generates a pulse signal for each small crank angle (for example, every 30 °).

The control circuit 40 performs shift detection of the crank angle signal and engine control (for example, ignition timing control, air-fuel ratio control, etc.) according to the present invention, and is configured as a microcomputer system. The control circuit 40 includes a micro processing unit (MPU) 44, a memory 44, and an AD converter 46.
I / O port 48 and bidirectional bus 50 connecting them
Composed of and. Pressure sensor 31 and air flow meter
Sensors that generate analog signals, such as 50, engine water temperature sensor 51, engine oil temperature sensor 52, atmospheric temperature sensor 54, and intake pipe pressure sensor 56, are connected to the AD converter 46. The crank angle sensors 32 and 33, the idle switch 53, and other sensors that generate digital signals are connected to the input / output port 48. The input / output port 48 is connected to the igniter 27 and the fuel injector 23.

FIG. 3 shows the pressure change in the combustion chamber 18 during motoring, such as during fuel cut or cranking.
Peaks at. The curve A indicates that the position of the compression top dead center TDC detected by the first crank angle sensor 32, which serves as a reference signal, matches the actual top dead center position, and is detected by the second crank angle sensor 33. The compression pressures P ₁ A and P ₂ A detected at symmetrical crank angles θ ₁ and θ ₂ across the top dead center TDC become equal. However, when the reference signal does not match TDC, the peak of the compression pressure is deviated from the TDC detected by the reference signal. That is, when the sensor 32 that the reference signal for generating a reference signal so as to shift in the delay direction of the engine rotation is attached becomes the characteristics of B, from the pressure P ₂ B at pressure P ₁ B is theta ₂ at theta ₁ growing. On the other hand, when a sensor that generates a reference signal is attached so as to be displaced in the forward direction of engine rotation, the characteristic of C becomes
The pressure P ₁ C at theta ₁ is smaller than the pressure P ₂ C at theta _2. The pressure difference ΔP = P ₁ -P ₂ at a point symmetrically separated from the reference signal by a small angle θ indicates a deviation angle between the TDC of the reference signal and the actual TDC. That is, if there is no deviation, the pressure difference is zero, if there is a deviation in the delay direction, the pressure difference is negative, and if there is a deviation in the advance direction, the pressure difference is positive. That is, the pressure difference and the deviation angle θoff have a relationship of θoff = k × ΔP. See FIG. The solid line is for high rpm and the broken line is for low rpm. That is, in the above equation, the proportional constant k is determined by the engine speed. Therefore, if we know the proportional constant k that changes depending on the pressure difference and the engine speed,
The deviation θoff of the crank angle detected by the crank angle sensor from the actual crank angle can be known.

By the way, when the reference position coincides with the actual crank angle, it has been described that it becomes symmetrical as shown by A in FIG.
Obtained under operating conditions without compression leakage. Then, under operating conditions such as low temperature with compression leakage, even if the reference position matches the actual crank angle, the left-right symmetric position symmetry is broken and there is an offset. Therefore, it is necessary to add compensation based on this offset. For example, when the engine is cold, the gap between the piston and the cylinder bore tends to expand, so that the compression leakage is large. At this time, the pressure P _{1 at the} crank angle in the compression stroke, which is −θ away from the top dead center, and
With the pressure P ₂ in the expansion stroke separated by θ, P ₁ > P ₂ . That is, the pressure difference P ₁ −P ₂ = 0 at θoff = 0 is not satisfied, but P ₁ −P ₂ = β, and β is a factor representative of the compression leakage and the heat transfer amount in the cylinder, for example, the engine water temperature. , Engine oil temperature, ambient temperature, engine speed, engine load, etc. That is, θof due to each of these factors
The contributions to the pressure difference at f = 0 are β ₁ , β ₂ , β ₃ , β ₄ , β ₅
Then, there is a relationship as schematically shown in FIGS. The total offset amount β is represented as β = β ₁ + β ₂ + β ₃ + β ₄ + β ₅ . Then, the value obtained by adding β becomes the deviation angle θoff after compensating the compression leakage factor.

10 to 12 are flowcharts for explaining the crank angle correction operation according to the principle of the present invention. First,
Figure 10 shows the fuel injection routine. At step 60, it is judged if the fuel cut flag fcut = 1. When the fuel is not cut, the routine proceeds to step 61, where the fuel injection amount TAU is calculated by TAU = TP × (1 + α) × β + γ. Where TP is the basic injection amount, α, β,
γ means each correction amount and correction coefficient. In step 62, the fuel injection amount TAU is set in the fuel injector. Fuel injection is executed. At the time of fuel cut, the routine proceeds from step 60 to step 63, and since TAU = 0, fuel injection is stopped.

FIG. 11 shows a fuel cut flag setting routine. As will be described later, in the present invention, the crank angle sensor is used when the fuel is cut.
The reference position detected by 32 is corrected. In step 65, whether the idle switch 53 is ON, that is, the throttle valve 30
It is determined whether is in the idle position. When idling, the routine proceeds to step 66, where the fuel cut flag fcut = 1
It is determined whether or not. When fcut = 0, go to step 67,
It is determined whether the engine speed N> Ncut. When N> Ncut, the routine proceeds to step 68, where fcut = 1 and the fuel is cut as a result. When the throttle valve is in the idle position, fcut = 1
If so, proceed from step 66 to step 69 where N <NRTN
It is determined whether or not (<Ncut). If No, go to Step 68 to maintain fuel cut, but if Yes, go to Step 7
The process proceeds to 0 and fcut = 0 is set, and the fuel cut is stopped. As described above, when the throttle valve is in the idle position and the engine speed is between Ncut and NRTN, fuel cut is executed.

FIG. 12 shows an A / D conversion routine, which is started every 30 degrees from the second crank angle sensor 33 at every arrival of the crank angle pulse signal. At step 75, the counter m is incremented. At step 76, it is judged if the 720-degree pulse signal from the first crank angle sensor 32, which is the reference signal, is received. FIG. 15B shows the 720 ° CA signal from the first crank angle sensor 32, and FIG. 15C shows the timing of the signal from the second crank angle sensor 33 every 30 ° CA.
The 720 ° signal should be set so as to fall to the compression top dead center, and 15 ° CA after that, the next 30 ° signal should be set to fall.

In FIG. 12, when there is a 720 ° signal, the process proceeds from step 76 to step 77, and the counter m is cleared. As shown in FIG. 15D, the counter m is incremented every 30 ° CA signal and cleared by the arrival of the 720 ° signal.

At step 78, it is judged if the fuel cut flag fcut = 1 or not, that is, if the deceleration fuel cut is in progress. When the fuel is being cut, the routine proceeds to step 79, where it is judged if the value of the counter m is the crank angle m ₁ for sampling the pressure of P ₁ . Yes
If so, the process proceeds to step 80, and AD conversion of the pressure signal from the pressure sensor 31 is started. In step 81 flag AD ₁
= 1.

When m is not m ₁ at step 79, the routine proceeds from step 81 to step 82, and it is judged if the value of the counter m is the crank angle m ₂ for sampling the pressure of P ₂ . If Yes, the routine proceeds to step 83, where AD conversion of the pressure signal from the pressure sensor 31 is started. In step 84, the flag AD ₂ = 1 is set.

Figure 13 shows the AD change completion interrupt routine, and the AD converter
This is an interrupt routine that is started by the notification of AD conversion completion from 46. At step 86, it is judged if the flag AD ₁ = 1. If Yes, the routine proceeds to step 87, where the AD conversion value is put into P ₁ . In step 88, the flag AD ₁ = 0 is reset.

When the flag AD ₁ = 0, the routine proceeds from step 86 to step 89, where it is judged if the flag AD ₂ = 1. If Yes, the routine proceeds to step 90, where the AD conversion value is put into P ₂ . Step 91
Then, the flag AD ₂ = 0 is reset. In step 92, the water temperature THW, the oil temperature THO, the ambient temperature TA, the engine speed NE, and the intake pipe negative pressure PM as the engine load β ₁ to ₅
Is calculated from the maps shown in FIGS. 5 to 9, and the sum is β. In step 92, the combustion pressure difference P ₁ −P
₂ and proportional constant k determined according to the engine speed
Then, the deviation angle θoff of the reference position detected by the crank angle sensor is calculated from β calculated in step 92.

When the flag AD ₂ 90 proceeds to step 93 from step 89, other analog sensors, for example, AD conversion processing of the analog signal from the air flow meter 50 is performed.

FIG. 14 shows a flowchart for controlling the ignition timing based on the deviation angle θoff of the reference position by the crank angle sensor calculated as described above. In step 105, the calculation of the reference injection timing θBASE is executed by a map of the engine speed and the intake air amount-rotation speed ratio, which is the load, as is well known. In step 106, the execution advance angle θ is calculated by subtracting the retard angle correction amount Δθ due to knocking or the like from θBASE. In step 107, the energization start time ts of the igniter is calculated, and in step 108 the energization end time te is calculated. The energization end time te moves from top dead center to the advance side step 106
The angle position is advanced by θ calculated in. Step 10
In 9, the energization start time ts is corrected from the deviation amount θoff of the reference position calculated in step 93 of FIG. In step 100, the energization end time te is corrected from the deviation amount θoff of the reference position. k'is a proportional constant. In step 111, the energization start time ts and the energization end time te are set in a register (not shown). Therefore, energization of the igniter is started at ts, and energization is ended at te. At the end of energization, a counter electromotive force is generated and ignition is executed. See FIG. If the reference position detected by the crank angle sensor 32 is deviated in the advance direction, for example, the 16th position is assumed if correction is not made as in the conventional case.
Although the ignition signal as shown by the broken line in the figure is obtained, the correction as shown by the solid line can realize an accurate ignition operation in the present invention. It should be noted that the present invention can be applied not only to the ignition timing but also to other control such as control of fuel injection timing. In this case, the valve opening time and valve closing time of the injector in the fuel injection signal set in step 62 of FIG.
It will be modified by f.

〔The invention's effect〕

When calculating the deviation amount of the crank angle detected by the crank angle detector from the difference in the compression pressure at a pair of crank angle positions close to the piston top dead center, the engine water temperature, oil temperature, atmospheric temperature, etc. The degree of asymmetry across the top dead center of the compression pressure curve with respect to the crank angle was grasped from the operating conditions that affect the compression leak, and the compression pressure difference was used to calculate based on this grasped degree of asymmetry. Since the shift amount of the crank angle is corrected, it is possible to detect the accurate crank angle after compensating for the asymmetry due to the change in the compression leakage amount.Therefore, without detecting the peak position as in the conventional case, Even if the pressure detection interval is as wide as 30 ° CA, sufficient accuracy can be obtained, measurement can be performed even at the high rotation side, and there is no fear that the calculation processing will be complicated.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention. FIG. 2 is a schematic overall configuration diagram of the embodiment. FIG. 3 is a diagram showing a change in cylinder pressure near the compression top dead center during motoring. FIG. 4 is a graph showing the deviation angle of the reference signal against the pressure difference. FIG. 5 to FIG. 9 are graphs schematically explaining the influence of various asymmetric factors of pressure at the angular positions sandwiching the compression top dead center on the offset amount. 10 to 14 are flowcharts for explaining the operation of the control circuit according to the present invention. FIG. 15 is a timing chart showing the compression pressure, the pulse signal from the crank angle sensor, and the counter operation timing. FIG. 16 is a timing diagram of an ignition signal according to the present invention. 18 ... Combustion chamber, 22 ... Spark plug, 24 ... Distributor, 26 ... Ignition coil, 28 ... Pressure sensor, 32 ... First crank angle sensor, 33 ... Second crank angle sensor, 40 ... Control circuit, 51 …… Engine water temperature sensor, 52 …… Engine oil temperature sensor, 55 …… Atmospheric temperature sensor, 56 …… Intake pipe pressure sensor.

Claims (1)

[Claims] 1. In an internal combustion engine, a crank angle detector for generating a signal according to angular positions of a plurality of crankshafts spaced apart from each other, a means for detecting compression pressure, and a piston top dead center sandwiched between them. Means for calculating the difference in compression pressure between a pair of adjacent crank angle positions, means for detecting the motoring time of the internal combustion engine, deviation angle between the pressure difference and the detection signal from the crank angle detector during motoring Means for calculating the deviation amount of the crank angle corresponding to the pressure difference calculated by the compression pressure difference calculating means based on the relationship A means for detecting an operating condition and a correction amount under the operating condition detected by the detecting means are calculated based on a predetermined relationship between the operating condition and the correction amount of the deviation amount. A crank angle detecting device comprising: means, and means for correcting the deviation amount based on the calculated correction amount.