JPH04252842A - Air quantity detector for engine - Google Patents

Abstract

PURPOSE:To keep off any output variation caused by intake pulsation by controlling a high load condition where this intake pulsation grows larger, so as to make no compensation, in a device which compensates air flow meter output according to a variation in the air flow meter itself. CONSTITUTION:This detector is provided with a calculating means 3 calculating a signal (for example, fundamental fuel pulse width Tp) equivalent to an air quantity per unit rotation from output of an air flow meter 2 generating the output conformed to the air quantity at the upstream of an inlet throttle valve. Then, a weighted means is added to the calculated result hereat by a weighted average means 4, and using a variation per unit time of this weighted mean value, the weighted mean value is preferentially compensated by a preferential compensation means 5. At this time, whether an engine is in a high load condition or not is judged by a high load judging means 6 from a load signal of the engine, and when the high load condition is the case, the weighted mean value is selected and when it is not, the preferential compensation value is selected to be selected each by a selector means 7, respectively, then this value after being selected is outputted as a signal equivalent to a cylinder air quantity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine air amount detection device.

0002

[Prior Art] In a so-called L-jetonic type fuel injection system, in which the amount of air is detected by an air flow meter installed upstream of a throttle valve, the amount of air is caused by the distance between the throttle valve and the air flow meter. There is a delay in detection response and a delay in response until the fuel injected from the injector reaches the cylinder, so it is necessary to correct these.

Considering this point, the throttle valve opening degree TVO is detected by the throttle sensor, and the change amount ΔTVO of this signal is
There are some methods that attempt to eliminate the above response delay by correcting the air flow meter output using (for example, see Japanese Patent Laid-Open No. 60-20103).

0004

By the way, instead of the amount of change ΔTVO in the opening of the throttle valve, the amount of change in the air flow meter output itself can be used to correct the air flow meter output.

[0005] However, since the air flow meter is affected by the intake pulsation and its output fluctuates, it is not possible to make corrections in accordance with the amount of change in the air flow meter itself.
This may amplify output fluctuations and increase air-fuel ratio fluctuations.

Therefore, although the present invention performs correction in accordance with the amount of change in the air flow meter itself, it is not performed under all load conditions, but only under high load conditions where intake pulsation becomes large. It is an object of the present invention to provide a device that prevents output fluctuations due to intake pulsation by not performing this operation.

[0007]

[Means for Solving the Problems] As shown in FIG. 1, the first invention includes an air flow meter 2 that outputs an output according to the amount of air upstream of an intake throttle valve, and an air flow meter 2 that outputs air per unit rotation based on the output of the air flow meter. means 3 for calculating a signal corresponding to the amount of air (for example, basic injection pulse width Tp); means 4 for adding a weighted average to the signal corresponding to the amount of air per unit revolution;
means 5 for proactively correcting the weighted average value using the amount of change per unit time; means 6 for receiving the engine load signal and determining whether the engine is under a high load condition; means 7 for switching to the weighted average value under load conditions and to the preemption correction value under conditions other than high load conditions, and outputting the value after switching as a signal corresponding to the cylinder air amount (for example, cylinder air amount equivalent pulse width Avtp); Equipped with

As shown in FIG. 2, the second invention includes an air flow meter 2 that outputs an output according to the amount of air upstream of the intake throttle valve, and a signal corresponding to the amount of air per unit rotation (for example, means 3 for calculating the basic injection pulse width Tp); means 4 for adding a weighted average to the signal corresponding to the air amount per unit revolution; and a means 4 for calculating the weighted average value (for example, the weighted average pulse width Avtpr) per unit time. Means 5 for proactively correcting the weighted average value using the amount
and a means 6 for receiving an engine load signal and determining whether the engine is under a high load condition, and based on this determination result, the weighted average value is set in the high load condition, and the preemptive correction value is set in the other than the high load condition. The value after this switching is converted into a signal corresponding to the cylinder air amount (for example, a pulse width A corresponding to the cylinder air amount).
means 7 for outputting the weighted average value Av
means 8 for determining whether or not tpr has become larger than the signal Tp corresponding to the amount of air per unit rotation, and based on this determination result, even under the high load condition, until the weighted average value Avtpr becomes larger; and means 9 for delaying switching to the weighted average value.

[0009]

[Effect] Switches to the preemption correction value under conditions other than high load conditions,
When this is output as a signal equivalent to the cylinder air amount,
This signal closely matches the required value even during slow acceleration.

On the other hand, when a high load condition occurs, a switch is made to the weighted average value so that the prefetch correction is not performed. This eliminates the possibility of amplifying output fluctuations that occur in the air flow meter due to the influence of intake pulsation.

Further, in the second invention, even under high load conditions, the switching to the weighted average value is delayed until the weighted average value becomes larger than the signal corresponding to the amount of air per unit revolution. As a result, even during sudden acceleration to full throttle, it is possible to prevent a delay in the weighted average value immediately after a high load condition is reached, and to provide the required air amount signal.

0012

Embodiment FIG. 3 is a system diagram of an embodiment in which the air amount detection device of the present invention is applied to an L-jetronic type fuel injection device. In the figure, air taken into an intake passage 11 from an air cleaner 10 is mixed with fuel injected from an injector 13 provided in an intake port 12, and is guided into a cylinder 14 of the engine. The gas that is combusted in the cylinder with the help of an ignition spark does the work of pushing down the piston, and after doing the work, the combustion gas passes through the exhaust passage 15 to a catalytic converter that purifies the three harmful components (CO, HC, NOx). I am led to 16.

When the accelerator pedal is depressed, the intake throttle valve 17 that is linked to this opens, and the amount of air flowing into the cylinder 14 increases. This change in air amount causes a change in the signal of a hot wire air flow meter (hereinafter abbreviated as AFM) 18 provided upstream of the throttle valve 17.

The AFM 18 consists of a sensor section and a control circuit (not shown). In the sensor section, a hot wire is coiled around a bobbin-shaped ceramic, and the entire sensor section is coated with glass. Covered. In the control circuit, a bridge circuit is constructed between the hot wire and the hot wire. In this case, as the amount of air increases, the hot wire will be cooled, so
When the current supplied to the hot wire is increased so that the temperature of the hot wire becomes constant, the value of the supplied current corresponds to the amount of air. This current value is converted into a voltage value and output.

The control unit 25, which mainly consists of a microcomputer, includes a sensor 19 that detects the throttle valve opening TVO, and a crank angle sensor (built in the distributor 20) that generates a predetermined pulse signal in synchronization with the crankshaft. ) 21, water temperature sensor 22, oxygen sensor 2
The control unit 25 receives the signal from the injector 13 and determines the amount of fuel to be injected from the injector 13 based on the AFM output.

Since the fuel injection pulse width given to the injector needs to be given in proportion to the air amount at the injector position, the basic injection pulse width Tp [ms] calculated from the AFM output and engine rotation speed Ne is calculated from the following formula. A weighted average is performed on the results.

Avtpr=Tp・Fload+old Avtpr
- (1-Fload)...(1) where Avtpr: weighted average pulse width [ms] old Avtpr: previous weighted average pulse width Fload: weighted average coefficient [%].

Since there is a constant air volume between the AFM and the cylinder, even if the air volume at the AFM position increases due to the sudden opening of the throttle valve, the cylinder air volume will not increase in response. The cylinder air amount increases with a certain phase lag. This phase delay is determined by the weighted average coefficient Flood, and if the weighted average of equation (1) is performed for the injection pulse width Tp with respect to the AFM position, the fuel amount can be given in proportion to the cylinder air amount. be.

However, the time from when a pulse is applied to the injector until the injected fuel reaches the cylinder inlet (approximately 7 to 10 ms, depending on the injector position)
), the phase of the weighted average pulse width Avtpr lags behind the cylinder air amount. If we consider this delay, Avtpr
Preemptive correction must be made so that the phase is more advanced than the cylinder air amount.

[0020] To explain this using the waveforms in FIG.
A waveform obtained by advancing the phase of the weighted average pulse width Avtpr is considered as the cylinder air amount equivalent pulse width Avtp. From the figure, the request Avtp is larger than the cylinder air amount by the advance correction amount T.
In order to be ahead by [ms], Avtp=Avtpr+X...(2) X/(T+td)=ΔAvtpr/Δt...(3) must be satisfied.

[0021] However, Δt: calculation interval of prefetch correction [ms] ΔAvt
pr: Avtpr change amount per Δt [ms] td:
These are the response delay of the AFM itself and the delay time [ms] due to the distance between the AFM and the throttle valve.

Eliminate X from both equations.

Avtp=Avtpr+ΔAvtpr・(T+td)/
Δt=Avtpr+(Avtpr-old Avtpr)・(
T+td)/Δt=Avtpr+(Avtpr-old Av
tpr)・GADVTP#…(4)

However, GADVTP# in equation (4) is a gain [anonymous number] for prefetch correction. For example, if the AFM is close to the throttle valve t
It can be considered that d=0, T=10ms, Δt=4m
s, GADVTP#=2.5 times.

[0025] In this way, by adding the correction amount (second term) corresponding to the amount of change in Avtpr itself to Avtpr, it is possible to prevent spray delay and accurately approach the required Avtp even during slow acceleration. can. Note that when preemption correction is performed, a start-up delay and overshoot occur, as shown in the shaded area in Figure 4, but as long as the distance between the AFM and the throttle valve is within 1.5 m, there is little effect even with sudden acceleration. .

Now, since the output of AFM fluctuates under the influence of intake pulsation, the weighted average pulse width Avtpr calculated based on AFM also fluctuates in output. If this signal with fluctuations in output is preemptively corrected using equation (4), the output fluctuation will be amplified under conditions with large intake pulsations, such as when the throttle valve is fully open, so the value after preemptive correction is used for fuel injection. Otherwise, the air-fuel ratio will fluctuate greatly, which in turn will cause torque fluctuations.

Therefore, in this example, the weighted average pulse width A
High load conditions (-50 mmHg to negative suction pressure downstream of the throttle valve) where the output fluctuations occurring in the VTPR are expected to be large.
0 mmHg), the preemption correction of equation (4) is not performed to prevent fluctuations in the air-fuel ratio. FIG. 5 is a routine for calculating the cylinder air amount equivalent pulse width Avtp. This routine runs at regular intervals (for example, every 4ms).
It is done repeatedly. Using this flowchart,
The operation of this example will be explained.

In step 1, the signal from the AFM 18 is
In step 2, a certain process (referred to as linearization process) is performed so that the A/D conversion value Qa is proportional to the air amount, and the linearized value is stored in a memory called Qs. Note that table characteristics for linearization are shown in FIG.

The basic injection pulse width Tp [ms] is calculated from the linearizing air amount Qs [g/s] and the engine rotational speed Ne [rpm] using the following formula (step 3). Tp=(Qs/Ne)・KCONST#…(5)

00
30] Qs/Ne in equation (5) is the amount of air per unit rotation at the AFM position, and Tp is the value obtained by multiplying this value by the air amount-pulse width conversion constant KCONST#, so
Tp is a signal equivalent to the amount of air per unit rotation.

Actually, the basic injection pulse width Tp is determined by the following equation.
Correct. Tpflat=Tp・Ktrm

[0032] Here, Ktrm is a coefficient for correcting air amount and injector errors for each engine condition.
trm means trimming. Trimming coefficient Ktr
To find m, engine speed Ne and α-N flow rate Qh
The 16×16 map allocated with o is referred to with interpolation calculation. Note that Qho is the air flow rate in the steady state of the throttle valve section determined from the throttle valve opening degree TVO and the rotational speed Ne, and is a well-known value.

In step 4, the weighted average coefficient Flood is
One of the following theoretical formulas Flood=1/{(120・Vm)/(
Ve・η・Ne・Δtc)+1} Floa
Calculate by d=(Ve·η·Ne·Δtc)/(120·Vm).

However, the meanings of the symbols are as follows. Δtc: Cylinder air amount calculation interval [s] Vm: Manifold volume [cc] Ve: Displacement [cc] η: Fresh air ratio in cylinder [%] Ne: Engine speed [rpm]

[0035] If the weighted average coefficient Flood is found by referring to a map, it will take a lot of time to create the map, so by finding the Flood using a theoretical formula determined by a physical model of the intake system, it will be possible to adapt it to the actual machine. This is to eliminate the need to do so.

In step 5, the weighted average pulse width Avtpr is calculated by performing a weighted average on the basic injection pulse width Tp using the above-mentioned equation (1).

In step 6, the value of the flag is checked. This flag is a flag that indicates whether to perform the prefetch correction of equation (4) on the weighted average pulse width Avtpr or to prohibit the prefetch correction.When the value of the flag is 0, the prefetch correction is performed, and when it becomes 1, Preemptive correction is prohibited.

Since the flag is 0 under the low load condition, the process proceeds to step 7, where the α-N flow rate (engine load equivalent amount) Qho is compared with the determination level (constant value) AVTQHH#. This is to see if there is a high load condition.
If Qho<AVTQHH#, there is no high load condition, and in step 13, the weighted average pulse width Avtpr is preemptively corrected using equation (4).

On the other hand, if Qho≧AVTQHH#, it is assumed that a high load condition has occurred, and the value of the flag is set to 1 (steps 7, 9), Avtp=Avtpr is set, and no prefetch correction is performed (step 12). . Note that step 8 will be described later. After reaching the high load condition, in step 10, Qho<AV
TQHL# (However, AVTQHL#<AVTQHH#)
Prohibition of preemptive correction continues unless the following occurs (steps 10 and 12). AVTQHL# is also a determination level (fixed value) and is provided separately from AVTQHH# in order to provide hysteresis.

If Qho<AVTQHL# in step 10, it is assumed that the high load condition has been overcome, and the value of the flag is set to 0 (steps 10 and 11), and the process returns to step 13 to perform prefetch correction.

FIG. 7 shows the waveform when the throttle valve is suddenly opened and closed.
Shown below. In the figure, the section where flag = 1 is the section where the value based on the air flow meter output (basic injection pulse width Tp in the figure) fluctuates greatly due to the influence of intake pulsation, and by prohibiting advance correction in this section, , output fluctuations can be prevented from being amplified. When the influence of intake pulsation is removed in this way, fluctuations in the air-fuel ratio can be prevented when fuel control is performed.

However, when the throttle valve is suddenly opened, the weighted average pulse width Avtpr lags much behind the load signal Qho immediately after entering the high load condition, so the rise time will be delayed until Avtpr catches up with Tp (or Qho). In order to eliminate delays, we would particularly like to see advance compensation.

Therefore, under high load conditions (Qho≧AVTQH
H#), the prefetch correction is continued until Avtpr≧Tp (steps 8 and 13 in FIG. 5). In other words, by providing a delay in switching to the anti-preemption correction state in a predetermined section after a high load condition occurs, there is a delay in response immediately after a high load condition occurs, even during sudden acceleration until the throttle valve is fully opened. It is possible to prevent this and provide the required air amount signal.

Furthermore, from the cylinder air amount equivalent pulse width Avtp obtained in steps 12 and 13, the final fuel injection pulse width Ti [ms] is determined by the following equation, and fuel injection is performed. Ti=Avtp×Co×α+Ts…(6)

[0045]
However, in equation (6), Co is the sum of 1 and various correction coefficients, α is the air-fuel ratio feedback correction coefficient calculated based on the oxygen sensor output, and Ts is the invalid pulse width of the injector 13.

Finally, in comparison with FIGS. 1 and 2, step 3 in FIG.
3 is the switching means 7, and steps 7 and 10 are the high load determining means 6.
, step 8 functions as the size determining means 8, and step 13 functions as the prefetching correction means 5.

[0047]

[Effect of the Invention] In the first invention, in a device that detects the amount of air based on AFM output, the weighted average value of the signal equivalent to the amount of air per unit rotation under high load conditions is set to the weighted average value under conditions other than high load conditions. Since each value is switched to a preemptive correction value and the value after this switching is output as a signal corresponding to the cylinder air amount, it is possible to prevent output fluctuations due to intake pulsation under high load conditions such as when the throttle valve is fully open.

[0048] In addition to the first invention, a second invention provides that even under high load conditions, the weighted average value remains unchanged until the weighted average value becomes larger than the signal corresponding to the air amount per unit rotation. Since the switching is delayed, even during sudden acceleration to the point where the throttle valve is fully opened, a response delay immediately after a high load condition is reached can be prevented, and the air amount signal as requested can be provided.

[Brief explanation of the drawing]

FIG. 1 is a claim correspondence diagram of a first invention.

FIG. 2 is a claim correspondence diagram of the second invention.

FIG. 3 is a system diagram of an embodiment in which the air amount detection device of these inventions is applied to an L-jetronic type fuel injection device.

FIG. 4 is a waveform diagram for explaining prefetch correction.

FIG. 5 is a flowchart for explaining the control operation of the embodiment.

FIG. 6 is a table characteristic diagram of the linearization flow rate Qs.

FIG. 7 is a waveform diagram illustrating the effect during a transient period according to the embodiment.

[Explanation of symbols]

2 Air flow meter 3 Air amount calculation means per unit rotation 4 Weighted average means 5 Preemption correction means 6 High load determination means 7 Switching means 8. Size determination means 9 Delay means 11 Intake passage 13 Injector 14 Cylinder 17 Intake throttle valve 18 Hot wire AFM 21 Crank angle sensor 25 Control unit

Claims (2)

[Claims] Claim 1: An air flow meter that outputs an output according to the amount of air upstream of an intake throttle valve; means for calculating a signal equivalent to the amount of air per unit rotation from the output of the air flow meter; means for adding a weighted average to the signal; means for proactively correcting the weighted average value using the amount of change in the weighted average value per unit time; means for determining, and means for switching based on the determination result to the weighted average value under high load conditions and to the preemptive correction value under conditions other than high load conditions, and outputting the value after this switching as a signal corresponding to the cylinder air amount. An engine air amount detection device comprising: 2. An air flow meter that outputs an output according to the amount of air upstream of an intake throttle valve, means for calculating a signal equivalent to the amount of air per unit rotation from the output of the air flow meter, and means for calculating a signal equivalent to the amount of air per unit rotation from the output of the air flow meter. means for adding a weighted average to the signal; means for proactively correcting the weighted average value using the amount of change in the weighted average value per unit time; means for determining, and means for switching based on the determination result to the weighted average value under high load conditions and to the preemptive correction value under conditions other than high load conditions, and outputting the value after this switching as a signal corresponding to the cylinder air amount. and means for determining whether the weighted average value has become larger than the signal corresponding to the air amount per unit rotation, and based on the determination result, the weighted average value is larger even under the high load condition. An air amount detecting device for an engine, comprising: means for delaying switching to the weighted average value.