JPH033889B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output smoothing device for a Karman vortex flow sensor for an internal combustion engine.

A conventional device of this type is one shown in FIG. 1, for example. This is a Kalman waveform signal from a Kalman vortex flow rate sensor (hereinafter simply referred to as Kalman sensor) which is applied to a period-to-digital converter 1 for digital conversion, and a Kalman period upper and lower cut device 2.
The maximum and minimum of the four consecutive Kalman sensor periods are removed (upper and lower cuts), and the remaining 2
This method calculates the average period of
Publication No. 32047).

However, with this conventional device, when the flow rate output fluctuates greatly due to intake pulsation under operating conditions where the engine has a long intake pulsation cycle, if the detection time (sampling time) is too short, it is difficult to determine which range of output is fluctuating. Since the configuration is such that it is not determined whether or not to take the average, under conditions where intake pulsation is large, such as when the engine is near full throttle or when there is pulsation from the blow-by/breather hose at low load, the influence of output fluctuations remains. For example, if the sample time is lengthened in order to reduce the amount of time, there is a drawback that the responsiveness of the engine will be reduced.

The present invention has been made in view of such conventional problems, and the period of the intake pulsation is predicted from the engine operating conditions, such as the engine rotation speed, the number of engine cylinders, and the engine cycle, and the period of the intake pulsation is calculated by predicting the period of the intake pulsation. It is an object of the present invention to provide an output smoothing device for a Karman vortex flow sensor that solves the above-mentioned problems by using a doubling time as a sample period and calculating the flow rate by averaging the Karman periodic output signals during this period.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 6.

FIG. 2 is a block diagram showing the configuration of one embodiment of the present invention. In this device, a Kalman waveform signal digitized by a period-to-digital converter 1 is supplied to a period adder 31. Period adding device 31
is supplied with the output of a sample time setting device 5 which sets a sample time in response to an engine rotation signal, and outputs the total value of the Kalman period and the number of samples during this set time to a dividing device 32.
The division device 32 divides the total value of the Kalman period by the number of samples and provides the resulting value to the flow rate calculation device 4. Then, the fuel injection amount is determined based on the output of the flow rate calculation device 4.

FIG. 3 is a flowchart showing the case where the arithmetic operation in the embodiment of FIG. 2 is performed by a computer.

This calculation first calculates the average time target value of the Kalman period.
Calculate T _L. This is calculated from the engine rotation speed as T _L = Time required for one engine rotation / Number of intake strokes per engine rotation x n (where n is an integer). , 1 rotation, 1 1/2 rotations, or 2 rotations.

Next, the Kalman periods given one by one are added up one after another, and the average value is calculated. This is done by adding the Kalman periods until the target value is exceeded, and dividing the total number of Kalman periods added by the number of samples of the Kalman periods to be added. This will be explained step by step using a flowchart. After calculating the average time target value T _L (step S ₁ ) and writing continuous Kalman period data to all addresses in the memory, each time new data of Kalman period T is given, the most New data is written to the memory address where the old data is stored, and this address is designated as I.X (step _S2 ). This new data is sent to the accumulator Acc, and the number of samples is counted by the Kalman cycle number counter NCNT (step _S3 ). Next, set the address where the second most recent data is written as a new I/X,
This data is transferred to the accumulator Acc and added to the latest data, and the counter
Count NCNT by +1. Here, when the latest data is written to the first address of the memory, the second newest data is written to the last address, so this address is designated as I.X (step
_S4 , _S5 , _S6 , _S7 ). Then, until the added value of the accumulator Acc exceeds T _L , the flow of steps S ₁ to _{S 8} is repeated to add the Kalman period data in order from the newest one, and the samples of the added period are When the total value of the cycles exceeds the target value _TL , the average value of the Kalman cycles T is obtained by dividing the total value by the count value of the counter NCNT (steps S ₈ and S _{9 )} . ) The air flow rate Qa is calculated from this average value (step _S10 ). This flow is performed at predetermined crank angles or time intervals, and the air flow rate, which changes in response to changes in engine speed, can be determined with good responsiveness. The air flow rate Qa obtained in this way is, for example, approximately equal to exactly two peaks of the intake pulsation, as shown in FIG. 5, and thus has small fluctuations.

Figure 4 shows the Karman period average time target value for one revolution of a 4-cylinder 4-stroke gasoline engine.
T _L was calculated from engine speed 0 to approximately 6000. Better results can be obtained by setting this target value T _L to be somewhat smaller than the time required for one rotation of the engine. This means that the addition result of the Kalman period is always T _L
This is because if T _L is set small, the result of addition of the Karman period will be closer to one rotation of the engine, and in the end, a value closer to the true average value of the Karman period will be obtained.

FIG. 5 shows the relationship between the calculation results shown in the flowchart of FIG. 3, the Kalman sensor waveform, and the intake pulsation. That is, as shown at the top of the figure, when there is intake pulsation, the output waveform of the Kalman sensor corresponds to it (the Kalman period becomes smaller as the flow velocity increases).

In the operating state shown in this example, the number of Kalman cycle samples is 18, which is closer to the true average value with less influence of intake pulsation than the conventional method of calculating the average of two samples regardless of the operating state. It is clear that a value is obtained.

FIG. 6 shows another calculation example of the present invention.
This is a flowchart that averages the Karman period for one engine rotation using the crank angle sensor's signal every 360 degrees. In this case, when the engine's 360° signal is input (step S ₁₁ ), the total sum of the Kalman periods T _T and the value of the cycle number counter NCNT, N _T , which have been input since the last 360° signal was input, are and is stored in memory (step _S12 ). Then, in preparation for inputting the next cycle, all Kalman cycles and NCNT are cleared to zero (step _S13 ).

Calculating the period of the Kalman sensor at every rise of the Kalman pulse from when a 360° signal is applied until the next 360° signal is applied (steps S ₁₄ and S ₁₅ );
If the new Karman period is twice or more than the previous Karman period, it is determined that there is a missing tooth, and the missing tooth is corrected by multiplying the new period by 1/2 (step _S16 ). Thereafter, the obtained Kalman period data are sequentially stored in a memory, and the number of periods is counted by a period number counter NCNT.

The total Kalman period addition value T _T obtained from this
The average value T A is calculated from the Kalman period number N _T and the average value T _A is calculated by the interrupt routine RQ being performed by a timer every 10 milliseconds (steps S ₁₉ and S ₂₀ ). Then, the air flow rate Qa is calculated based on the average value T _A.

In the above example, an example was shown in which the average value for one revolution is calculated for a four-cylinder four-stroke gasoline engine, but this is because 1 to 2 revolutions is appropriate in view of responsiveness, and for a 6-cylinder engine, 2/3 About 2 rotations is best.

As described above, the present invention predicts the period of intake pulsation from the engine rotation, uses an integer multiple period of the period as a sample period, and averages the Karman period output signal during this period to obtain the flow rate. Even under operating conditions such as when a large engine is near full throttle or when a blow-by system is operating at low load, the flow rate calculation value does not fluctuate due to fluctuations in the output of the Kalman sensor, making it possible to form an air flow signal with good responsiveness. A signal suitable for fuel control in the injection device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an output smoothing device for a conventional Karman vortex flow sensor, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
Figure 4 is a flowchart showing the calculation process for output smoothing in the present invention, Figure 4 is a diagram showing the Karman period average time target value versus rotation speed characteristic for one revolution of a 4-cylinder 4-stroke gasoline engine, and Figure 5 is a diagram showing the characteristics of the intake air An explanatory diagram showing a Kalman waveform during pulsation and a waveform after smoothing processing, and FIG. 6 is a flowchart showing another arithmetic processing method in the present invention. 1...Kalman period-digital conversion device, 2
. . . Kalman period upper and lower cut device, 3 . . . Average calculation device, 4 . . . Flow rate calculation device, 5 .

Claims (1)

[Claims] 1. A sample time setting device that sets a sample time based on an internal combustion engine rotation signal, a device that sequentially adds the cycles of the output given from the Karman vortex flow rate sensor during the sample time, and the number of cycles during the sample time. a counter that counts
An output smoothing device for a Karman vortex flow rate sensor for an internal combustion engine, comprising a device for dividing the output of the adding device by the count value of the counter to obtain an average value.