JPS6371548A - Crank angle detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To permit the correct control without finely dividing the division angle by calculating the correction quantity of the crank angle detection value according to the pressure difference at the position at which the compression top dead center detected in motoring is interposed. CONSTITUTION:The pressure in a combustion chamber 18 in the motoring such as in fuel cut and cranking is highest at the compression top dead center. However, when the standard signal supplied from the first crank angle sensor 32 does not coincide with the compression top dead center, the peak of the compression pressure shifts from the compression top dead center which the standard signal detects. Therefore, in a control circuit 40, the difference of the compression pressure detected by a pressure sensor 31 is detected at the objective crank angle, keeping the compression top dead center detected by the second crank angle sensor 33 interposed, and the correction quantity of the crank angle detection value is calculated by a crank angle sensor 32. Therefore, the sufficient precision can be obtained, even with a considerably wide pressure detecting interval.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for correcting a detected value of a crank angle sensor that detects the position of a crankshaft in an internal combustion engine.

[Conventional technology]

In internal combustion engines, 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, such as crankshaft,
A permanent magnet piece is provided on the distributor shaft connected to the crankshaft, and a magnetic detection member composed of a Hall element or the like is provided opposite to the permanent magnet piece, so that a pulse signal corresponding to the crankshaft position is obtained by magnetic change. There is.

The crank angle sensor should be installed so that its detected value accurately corresponds to the crank angle.
Some errors will inevitably occur due to installation tolerances, etc. Due to such errors, the crank angle becomes inaccurate,
The engine cannot be controlled ideally.

Therefore, in order to correct the error of the crank angle sensor, JP-A-60-114734 focused on the fact that the compression pressure peak appears at top dead center during motoring such as during deceleration fuel cut, and calculated the pressure peak position and standard A technique for correcting a signal from a crank angle sensor based on a difference from a crank angle signal is disclosed.

[Problem that the invention seeks to solve]

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

An object of the present invention is to provide a rank angle detection device that allows accurate correction without making the division angle finer.

[Means for solving problems]

According to this invention, in an internal combustion engine, a crank angle detector 1 that generates a signal corresponding to a plurality of angular positions of a crankshaft at intervals, a means 2 for detecting compression pressure, and a means 2 for detecting compression pressure, which are arranged on both sides of the piston top dead center. means 3 for calculating the compression pressure difference at a pair of crank angle positions adjacent to this, means 4 for detecting when the internal combustion engine is motoring, and pressure difference calculated by the compression pressure difference calculation means 3 during motoring. Accordingly, a crank angle detecting device is provided which includes means 5 for calculating the amount of deviation of the crank angle detected by the crank angle detector 1.

〔Example〕

FIG. 2 shows an internal combustion engine in an embodiment, in which 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a cylinder head, 18 is a combustion chamber, 2
0 is an intake valve, 21 is an intake boat, 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 boat 21
is connected to a throttle valve 30 via an intake pipe 28 and a surge tank 29. A pressure sensor 31 for detecting combustion pressure is arranged in the combustion chamber 18 . A first crank angle sensor 32 and a second crank angle sensor 33 are installed in the distributor 24.

On the other hand, a first magnet member 36 and a 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 location, and the first crank angle sensor 32 as a Hall element generates a pulse signal every rotation (corresponding to 720° CA) of the distribution shaft. and is particularly configured to generate a reference signal at compression top dead center. The second magnet portion 38 has a plurality of equally spaced magnetized portions on its circumference, and has a plurality of magnetized portions arranged at equal intervals on its circumference, and has a plurality of magnetized portions arranged at equal intervals on its circumference, and has a plurality of magnetized portions arranged at regular intervals on its circumference, and has a plurality of magnetized portions arranged at regular intervals on its circumference, and has a plurality of magnetized portions arranged at regular intervals on its circumference.
') generates a pulse signal.

The control circuit 40 performs crank angle signal deviation detection and engine control (eg, ignition timing control, air-fuel ratio control, etc.) in the present invention, and is configured as a microcomputer system.

The control circuit 40 is a microprocessing unit (MPU).
) 44, memory 44, AD converter 46, input/output port 48, and bidirectional bus 50 connecting these. Sensors that generate analog signals, such as the pressure sensor 31 and the air flow meter 50, are connected to the AD converter 46.

Crank angle sensors 32, 33 and idle switch 5
3. Other sensors that generate digital signals are wired to the input/output port 48. Further, the input/output boat 48 is connected to the igniter 27 and the fuel injector 23.

In FIG. 2, a bypass passage 51 is provided to bypass the throttle valve 30, and a bypass control valve 52 is installed in the bypass passage 51. As will be described later, the bypass control valve 52 is normally closed, but is opened during fuel cut to increase the amount of intake air, thereby increasing the compression pressure detected by the pressure sensor 31, thereby improving the accuracy of pressure difference detection. This is to do so. A bypass control valve does not necessarily need to be installed.

Figure 3 shows the pressure change in the combustion chamber 18 during motoring such as fuel cut or cranking, and shows the compression top dead center T.
It peaks at DC. Curve A is the compression top dead center TD detected by the first crank angle sensor 32 serving as a reference signal.
When the position of C coincides with the actual top dead center position, the crank angle θ1. Compression pressure detected at θ2]'JA and P2A become equal.

However, when the reference signal does not match TDC,
The peak of the compression pressure shifts with respect to the TDC detected by the reference signal. That is, if a sensor that generates a reference signal is installed so that the reference signal deviates in the direction of engine rotation lag, the characteristic will be B, and the pressure PjB at θ1 will be greater than the pressure P2B at θ2. On the other hand, if the sensor that generates the reference signal is installed so as to deviate in the advancing direction of the engine rotation, the characteristic will be C, and the pressure PI at θ1 will be
C becomes smaller than the pressure P2C at θ2.

The pressure difference Δp=p, -P2 at a point symmetrically spaced apart from the reference signal by a small angle θ indicates the deviation angle between the TDC of the reference signal and the actual TDC. That is, if there is no shift, the pressure difference is zero, if there is a shift in the lag direction, the pressure difference is negative, and if there is a shift in the advance direction, the pressure difference is positive. That is,
The pressure difference and the deviation angle θoff have the following relationship: θoff=kXΔP. See Figure 4. The solid line is for high rotational speed, and the broken line is for low rotational speed. That is, in the above equation, the proportionality constant is determined by the engine rotation speed.

Therefore, by knowing the proportionality constant k that changes depending on the pressure difference and the engine speed, it is possible to know the deviation of the crank angle detected by the crank angle sensor from the actual crank angle.

In order to obtain a linear relationship between the pressure difference and the deviation angle θoff, the rate of change in pressure needs to be approximately constant with respect to the rate of change in crank angle. Further, in order to increase the resolution of the deviation angle of the reference signal with respect to the pressure difference ΔP, it is preferable that the rate of change in pressure is large. FIG. 5 shows the ratio of compression pressure change to crank angle change, dP/dθ, near compression top dead center TDC during motoring. From the above: Combustion pressure P1. Crank angle θ1.P2 should be measured. It is preferable that θ2 is within the shaded range in the figure, specifically within ±10 to ±30 from TDC.
range of degrees.

7 to 12 are flowcharts 1 for explaining the crank angle correction operation according to the principle of the present invention. First, FIG. 6 shows a fuel injection routine.

In step 60, it is determined whether the fuel cut flag fcut=1. At the time of non-fuel cut, the process proceeds to the steering knob 61, and the fuel injection amount TAU is calculated by TAυ=TPX (1+α)×β+γ. Here, TP is the basic injection amount, α.

β and γ mean respective correction amounts and correction coefficients. Ste Nobu 6
In step 2, the fuel injection amount TAXI is set to the fuel injector. Fuel injection is performed. At the time of fuel cut, the process proceeds from step 60 to step 63, and since TAU=O, fuel injection is stopped.

FIG. 7 shows the fuel cut flag setting routine.

As will be described later, in the present invention, the reference position detected by the crank angle sensor 32 is corrected at the time of fuel cut. In step 65, it is determined whether the idle switch 53 is ON, that is, whether the throttle valve 30 is in the idle position. When the engine is idling, the process proceeds to step 66, where it is determined whether the fuel cut flag is fcut-1. fcut=o
If so, proceed to step 67, and engine speed N > N
It is determined whether it is a cut or not. When pi>Ncut, the process proceeds to step 68, where fcut=1 is set, and as a result, fuel is cut. Throttle valve fcut at idle position
When = 1, proceed from step 66 to step 69,
Determine whether IJ <NRTN (< Ncut). N
When the answer is O, the process proceeds to step 68, and the fuel cut is maintained; however, when the answer is Yes, the process proceeds to step 70, where fcut=
O, and fuel cut is stopped. As mentioned above, when the throttle valve is in the idle position, the engine speed is Ncu
Execute fuel cut between t and NRTN.

FIG. 8 shows an A/D conversion routine, which is started every time a crank angle pulse signal arrives every 30 degrees from the second crank angle sensor 33. In step 75, the counter m
is incremented.

In step 76, it is determined whether or not a 720 degree pulse signal from the first crank angle sensor 32, which is a reference signal, is being received. Figure 13 (b) shows the first crank angle sensor 3.
720'CA signal from 2, (c) shows the timing of the signal every 30''CA from the second crank angle sensor 33.The 720' signal should be set to fall at compression top dead center, Then after 15° CA the next 30°
The signal is set to fall.

In FIG. 8, if there is a 720° signal, the process proceeds from step 76 to step 77, where the counter m is cleared. 1st
As shown in FIG. 1, the counter m is incremented every 30° CA signal, and is cleared by the arrival of the 720° signal.

In step 78, it is determined whether the fuel cant flag fcut=1, that is, whether deceleration fuel is being cut.

If the fuel is being cut, proceed to step 79 and set the counter m.
The value of is the crank angle m at which the pressure of Pl is sampled
Determine whether it is 1 or not. If Yes, the process proceeds to step 80, where AD conversion of the pressure signal from the pressure sensor 31 is started. In step 81, the flag is set to AD+-1.

If m is not ml in step 79, the process proceeds from step 81 to step 82, where it is determined whether the value of counter m is the crank angle m2 at which the pressure at P2 is sampled. Yes
If s, the process proceeds to step 83, where AD conversion of the pressure signal from the pressure sensor 31 is started. At step 84, the flag is set to AD2-1.

FIG. 9 shows an AD change completion interrupt routine, which is started when the AD converter 46 notifies AD conversion completion. At step 86, the flag A
It is determined whether Di=1 or not.

If Yes, the process advances to step 87 and the AD conversion value is Pl.
can be placed in At step 88, the flag ADl is reset to O.

When flag A and Di=O, the process advances to step 89, where it is determined whether flag AD2=1 or not. If Yes, the process advances to step 90, and the A and D conversion values are entered into P2. In step 91, the flag AD2 is reset to O. In step 92, the deviation angle θoff of the reference position detected by the crank angle sensor is calculated using the combustion pressure difference P1-P2 and a proportionality constant determined according to the engine speed.

When flag A, D2=O, the process proceeds to step 93, where AD conversion processing of an analog signal from another analog sensor, for example, the air flow meter 50, is executed.

FIG. 10 shows a bypass control routine, and this routine is provided to increase the amount of intake air when measuring pressure and improve the accuracy of pressure difference detection. In step 94, it is determined whether the fuel cut flag is fcut-1, and fcut=1.
In this case, the process proceeds to step 95, and the bypass control valve 52 is opened to increase the amount of intake air.

FIG. 11 shows a routine for controlling a lock-up clutch in order to improve pressure difference detection accuracy in a vehicle equipped with an automatic transmission equipped with a direct coupling clutch (lock-up clutch). In step 97, the deceleration fuel (fcu)
t = 1).

If Yes, proceed to step 98, and check the flag f to see if the fuel was cut the last time this routine was executed.
ct+t"-1 or not. If the previous fuel cut was in progress, the process directly bypasses the following process; if the previous fuel cut was not in progress, that is, when transitioning from the fuel supply state to the fuel cut state, the process proceeds to step 99. The contents of the flag Po+ indicating the lock-up state are saved to Fmf, and 1 is set in the flag Fm at step 100. Here, the flag Fm indicates the lock-up state in the automatic transmission, and Fm=1.
When , the lock-up clutch is engaged and F m −
When ○, the lock-up clutch is controlled to be released. If the fuel cut is not in progress, proceed from step 97 to step 101, and set the previous fuel cut flag fcut.
Determine whether “=1 or not.When there was a fuel cut last time,
That is, when returning from the fuel cut state to the fuel supply state, the process proceeds from step 101 to step 102, and the state of the lock-up clutch saved in the memory Fmf is set to the flag F.
Returned to m. As in this embodiment, by engaging the lock-up clutch during deceleration fuel cut, the engine braking effect is weakened, the rate of decrease in the deceleration engine speed is reduced, and the engine speed is increased to the fuel supply return speed N.
The transition to RTN (step 69 in FIG. 7) is delayed. Therefore, the deceleration fuel cut time is extended,
Since the crank angle deviation detection time is extended, accuracy can be improved.

FIG. 12 shows a flowchart for controlling the ignition timing based on the deviation angle θoff of the reference position calculated by the crank angle sensor as described above. Step 10
In step 5, the calculation of the basic injection timing θBASE is performed using a map of the engine rotational speed and the intake air amount to rotational speed ratio, which is the load, as is well known. In step 106, θBAS
The effective advance angle θ is calculated by subtracting the retard angle correction amount Δθ due to knocking etc. from E. In step 107, the igniter energization start time ts is calculated, and in step 108, the energization end time te is calculated. The energization end time te becomes an angular position advanced from the top dead center by θ calculated in step 106 on the advanced angle side. In step 109, the energization start time ts
is corrected based on the deviation amount θoff of the reference position calculated in step 92 of FIG.

In step 100, the energization end time te is corrected based on the deviation amount θoff from the reference position. β is a proportionality constant. In step 111, the energization start time tss and the energization end time te are set in a register (not shown).

Therefore, energization of the igniter starts at ts, and ends at te, and at the end of the energization, a back electromotive force is generated and ignition is executed. See Figure 14. For example, if the reference position detected by the crank angle sensor 32 is shifted in the advance direction, an ignition signal as shown by the broken line in FIG. Accurate ignition operation can be achieved by correcting as follows.

Note that the present invention can be applied not only to ignition timing but also to other controls, such as fuel injection timing control. 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. 6 will be corrected by the deviation angle θoff.

〔Effect of the invention〕

According to this invention, the correction amount θoff of the crank angle detection value by the crank angle sensor is calculated by detecting the pressure difference at the positions across the compression top dead center during motoring such as deceleration fuel cut. Therefore, it is possible to obtain sufficient accuracy even with a wide pressure detection interval such as 30"CA without detecting the peak position as in the conventional method, and it is possible to measure even at high rotation speeds, and the calculation processing is simple. There is no risk of crowding.

Further, as an effect of the embodiment, measurement accuracy can be improved by opening the bypass or engaging the lock-up clutch during deceleration fuel cut.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of this invention. FIG. 2 is a schematic overall configuration diagram of the embodiment. FIG. 3 is a diagram showing the change in cylinder pressure near compression top dead center during motoring. FIG. 4 is a graph showing the deviation angle of the reference signal with respect to the pressure difference. FIG. 5 is a graph showing the relationship between crank angle and pressure change rate. FIGS. 6 to 12 are flowcharts illustrating the operation of the control circuit in this invention. FIG. 13 is a diagram showing compression pressure, pulse signals from the crank angle sensor, and counter operation timing. FIG. 14 is a timing diagram of the ignition signal according to the present invention. 18... Combustion chamber, 22... Ignition plug, 24... Distributor, 26... Ignition coil, 28... Pressure sensor, 32... First crank angle sensor, 33... Second Crank angle sensor, 40...control circuit.

Claims (3)

[Claims] 1. In an internal combustion engine, a crank angle detector that generates signals corresponding to a plurality of angular positions of a crankshaft at intervals, a means for detecting compression pressure, and a pair of cranks adjacent to the crankshaft with the piston top dead center in between. A means for calculating a difference in compression pressure at an angular position, a means for detecting when the internal combustion engine is motoring, and a crank angle detected by a crank angle detector based on the pressure difference calculated by the compression pressure difference calculating means during motoring. A crank angle detection device comprising means for calculating the amount of deviation of the crank angle. 2. Claim 1. The amount of intake air is increased by opening the bypass passage during motoring. crank angle detection device. 3. Claim 1: Extending the fuel cut time by engaging a lock-up clutch during motoring
．． crank angle detection device.