JPS60183524A - Average air flow rate detecting apparatus by karman's vortex street type air flow rate sensor - Google Patents

Abstract

PURPOSE:To detect the average of pulse cycles with high precision during large flow rate by calculating the average cycle or the average air flow rate at every detection of a pulse cycle more than a prescribed time after counting a prescribed number or the smaller number than that of pulse by Karman's vortex street. CONSTITUTION:The pulse output of a Karman's sensor 3 in which an output signal (a) becomes 1 at every generation of Karman's vortex is counted by microprocessor 9. Whether the prescribed cycle is exceeded or not is discriminated in case >= the prescribed number Nmax, and the average pulse cycle is calculated in case >= said cycle. The prescribed number Nmin in exceeded or not is discriminated in case <= the number Nmax, the average air flow rate is obtained in case <=Nmin, whether the prescribed cycle is exceeded or not is discriminated in case >=Nmin. The average pulse cycle is calculated in case >= said cycle, and the average air flow rate is calculated switchedly in case <= said cycle. Further, in calculation of the average pulse cycle, a constant in prescribed limit is added to Nmax, the averaging processing is performed to prepare next processing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the average flow rate of air flowing into an automobile engine or the like by processing output pulses of a Karman vortex type air flow sensor.

Conventional technology and problems In general, in internal combustion engines, the amount of intake air is measured,
Based on the measurement results, the fuel injection amount is controlled to keep the air-fuel ratio constant. Various types of measuring devices for measuring the amount of intake air have been proposed in the past, and among them, a Karman vortex air flow sensor (hereinafter referred to as a Karman sensor), which has excellent responsiveness, has been attracting attention. This Karman sensor utilizes the fact that when a vortex generator is placed on the intake side of an internal combustion engine, air vortices (Karman vortices) are generated in the vicinity at a frequency proportional to the air flow rate. A pulse is generated at a timing related to the generation of the Karman vortex, and the period of the generated pulse signal is inversely proportional to the amount of inflowing air at that time.

Incidentally, the air flow rate of an internal combustion engine fluctuates periodically during processes such as intake and exhaust, and as shown in FIG. 1, the greater the opening of the throat, the greater the range of fluctuation. Since the Kalman sensor has sufficient responsiveness to follow such fluctuations, for example, the second
As shown in the figure, when the throttle valve opening is large and the flow rate is large, the pulse train includes a pulse train with an extremely short period that occurs during the period when the flow rate is large, and a pulse train with a relatively short period that occurs during the period when the flow rate is small. becomes. Therefore, it is necessary to average the pulse period by some method.

As a general technique for this purpose, it is conceivable to divide the pulse signal at intervals of time corresponding to a predetermined angle of the engine crank angle and calculate the average thereof. This is averaged for each period corresponding to one variation period p of the instantaneous air flow rate, and the timing of the start point and end point of the period is given by the output of a predetermined angle from the crank angle sensor. In this method, if the period p is set so that its start and end points are in the middle of a large period, as shown by symbol p1 in Figure 2, it becomes impossible to measure these large periods Lp, and the averaging error becomes too large. also becomes larger. Therefore, 1 in Figure 2. i-no.p
As shown in Figure 2, the period p is set to include a large period 12, but even so, the pulse periods at the beginning and end of period l) cannot be measured and errors remain, and the starting point of period p is usually Since there is some delay time between when the pulse is detected and when the pulse can be counted, setting the starting point at a place where the pulse period is extremely short will result in an error in counting the number of pulses. This has the disadvantage of adding errors.

OBJECT OF THE INVENTION The present invention improves the drawbacks of the prior art, such as:
The purpose of this is to make it possible to accurately detect the average of the Kalman sensor output pulse periods for each fluctuation during a large flow rate when the instantaneous air flow rate fluctuates rapidly.

Principle, Structure, and Function of the Invention In general, in a Kalman sensor, when the fluctuation range is large during a large flow rate, a plurality of pulses appear and the pulse interval (period!IJI) is large, as shown in Fig. 2. The fluctuation of instantaneous air flow rate appeared every cycle. Every time a cycle larger than a predetermined value (T max ) appears, the average value is 1.
By setting 7.1 period, it is possible to calculate the average for each cycle of fluctuation when the flow rate is large and the range of fluctuation is large. In other words, when the flow rate is large, a pulse train as shown in Fig. 3(a) occurs, so if we add the average period each time a large period appears, we can average it at intervals as shown by the symbol Q. The interval will match one variation period of the instantaneous air flow rate. In reality, however, as shown in Figure 3(b), sometimes after a short cycle, a longer cycle appears, which is longer than a predetermined value (1"maχ). As a result, averaging is performed as shown by reference numeral Q' in the same figure, and a case may occur in which the instantaneous air meteor is not averaged to a stop when the instantaneous air meteor changes. The present invention takes this point into account, and does not always adjust the average period when a period larger than a predetermined value (Tmax) appears, but instead calculates a predetermined number of pulses (Nmin) from the previous average processing end pulse. Averaging processing is performed only when a cycle larger than a predetermined value (Tmax) appears after Tmax. As shown in Fig. 3(b), even if pulse P2 appears after a relatively long interval after pulse l)1, it is ignored because it is the previous average ending pulse or in this case PI. , the averaging process is performed when pulse P3 is detected. One addition makes it possible to perform averaging processing for each period of fluctuation of the instantaneous air flow rate.

Furthermore, the intervals (periods) of the output pulses of the Kalman sensor when the flow rate is small are sparse and generally large.

Therefore, if -1 is used twice, the average is calculated every predetermined number (Nmin) of pulses of the Kalman sensor when the flow rate is small, and averaging can be performed with relatively good responsiveness.

However, at medium flow rates, the pulse period is set to an appropriate predetermined value (T
max) is smaller or almost the same. For this reason, a predetermined value (T max
) If the average period is increased every time a larger period appears, it is difficult to average the medium flow rate.

For this reason, in the present invention, calculating the average every time a predetermined number (N max) of pulses appear is defined as "h", and a predetermined value ("l" may) after a predetermined number (N min) of pulses occur.
If a larger cycle is detected and shifted by 1-11, the average is calculated before the number N max is reached. This deviation makes it possible to adjust the average cycle of the output pulses of the Kalman sensor with good responsiveness at both low and high flow rates, and at medium flow rates, it is possible to average every N pulses at least even if the cycle is greater than or equal to T max. You will be bitten.

FIG. 4 is an explanatory diagram of the configuration of the present invention, in which the Kalman sensor C
3, the pulse signal generated at a timing related to the generation of Karman vortices is inputted to the alZ equalization cycle generation means for calculating the average air flow rate. The pulse number counting means CN counts the pulses output from the Kalman sensor C3,
When a predetermined number (Nmin) has been counted, this fact is notified to the predetermined period detection means DE, and when a predetermined number (Nmax) has been counted, a calculation command is issued to the calculation means. The pulse period detection means PD measures the period of the output pulse of the Kalman sensor C3 and detects a period larger than a predetermined value ('l'max), and when detected, notifies the predetermined period detection means 1]U of this fact. .

The predetermined period detection means DE detects a predetermined number of pulses (Nn+in) by the pulse number counting means CN, and when the pulse period detection means PD detects a period less than or equal to a predetermined value (Tmax), the calculation means function. A calculation command is issued. This calculation means calculates the average air flow rate each time a calculation command is issued from the pulse number counting means CN or from the predetermined period detection means.

FIG. 5 is an explanatory diagram of the operation of the present invention, and (a) is 11f.
1 shows a temporal change in the air flow rate, and (b) shows an example of the output pulse of the Kalman sensor at that time. In addition,
L1~t48 are each output pulse of the Kalman sensor, Q1~
Q8 indicates the averaged air flow rate. According to the configuration shown in Fig. 4, by setting the predetermined time (Tmax) slightly smaller than the maximum period that appears during large flow rates, the average is calculated for each cycle of fluctuation during large flow rates (see Q5 to Q7). ), when the flow rate is low, the period of the output pulse of the Kalman sensor O3 is longer than the predetermined time (Tmax), or the period of the output pulse of the Kalman sensor O3 is longer than the predetermined number (
Due to the limitation of Nmin (here, 3), averaging is performed every three pulses of the Kalman sensor C3 (see Ql, Q2, and Q8). Furthermore, at medium flow rates, an average is calculated every time the pulse number counting means CN counts a predetermined number of pulses (Nmax, here 9) (Q3.
4 #sho).

In addition, in Fig. 5, when transitioning from a small flow rate to a medium flow rate,
The average every 3 pulses detected is suddenly switched to the average every 9 pulses detected. This is because the predetermined number (Nmax) is fixed, and it cannot be denied that the responsiveness is somewhat impaired in this part. To improve this, the predetermined number (Nmax) may be gradually deviated within a predetermined range in relation to the count value of the pulse number counting means CN when calculating the average.

Further, if the predetermined number (Nmin) is set to 1, for example, when the flow rate is small, and is changed to 1]J, and to 3, for example, when the flow rate is large, it becomes possible to average every pulse when the flow rate is small. FIG. 6 is an explanatory diagram of the operation of the present invention when such measures are taken, and the difference from FIG. 5 is that the average Ql, Q2 at the small flow rate in FIG. 5 is the average QIO, Ql'1
．． Q12 and Q20. Q21. Each is subdivided into Q22, and the average Q when transitioning from small flow rate to medium flow rate.
3 is Q30. This point is subdivided into Q31. In this example, the predetermined number (Nmax) is increased by 3 (however, the rate at which the number is increased is arbitrary).

Furthermore, it is preferable to shift the increase rate of the predetermined value (Nmax) so that it becomes a little smaller during acceleration, since the response will be better during transient situations and when there is a sudden change from a small flow rate to a large flow rate.

Furthermore, the fluctuation period of the air flow rate is determined by the engine speed, and therefore, the state in which the pulse interval (period) is large, which appears when the instantaneous air flow rate has a large fluctuation range and a large flow rate, inevitably differs. Therefore, it is desirable that the predetermined period (TmaX) in the pulse period detecting means PD be set to an optimal value according to the engine rotation speed at that time. In other words, the higher the engine speed, the smaller the predetermined period (TmaX).

Embodiment of the Invention FIG. 7 is a block diagram of the main parts of an embodiment of the present invention, where ■ is an internal combustion engine, 2 is an air cleaner, and 3 is a Karman sensor. Every time a Karman vortex is generated, its output signal a is °l
゛. 4 is a throttle chamber, 5 is an intake manifold, 6 is an electromagnetic fuel injector, 7 is a throttle valve that controls the flow of intake air, 8 is a crank angle sensor, 9 is a microbe sensor, 10 is a memory, 11 is a crank angle A data input section 12 is a data output section for inputting the output of the sensor 8 and other engine parameters such as cooling water temperature, intake temperature, throttle valve opening, on/off information of various switches such as an idle switch, etc. to the microprocessor 9. .

Intake air is supplied from the air cleaner 2 to the Karman sensor 3. Fuel is supplied to each cylinder from each branch of an intake manifold 5 via a throttle chamber 4, and is injected into the internal combustion engine l by a fuel injector 6. In addition, the amount of intake air is determined according to the state of the internal combustion engine as shown in Fig. 5.
The output signal a changes as shown in FIG. 6, and the output signal a also changes in accordance with the change. The output signal a of the Kalman sensor 3 is input to the interrupt terminal INT of the microprocessor 9, and an interrupt is generated when the output signal a rises, for example.

FIG. 8 is a flowchart showing an example of this interrupt processing, and 81 to S14 indicate each step.

When the microprocessor 9 receives an interrupt, it first memorizes the time at that time as the latest pulse time '■゛1.
), pulse count]・Amplify the number N by +1 count (
S2). Next, the pulse count number N is set to a predetermined number (Nmax
) or more, and if it is more than a predetermined number (Nmax, ), proceed to step S6. If it is determined that it is less than a predetermined number (Nmin), the value of the latest pulse time 'r1 is set to the interrupt of one pulse before. At time T3 (513), the process returns to the main routine. If it is determined that the number is greater than the predetermined number (Nmin), the latest pulse time 1 is subtracted from the interrupt time of 1 pulse riij by 3 to obtain the current pulse period of 2 (S5
), 72 is less than or equal to the predetermined period (1'max') -! 1- (S6), and if 'f゛2 is greater than or equal to the predetermined period (Tma,
Move to i4.

In step S7, the inter-pulse time T5 is averaged by subtracting the time T5 at the end of the previous averaging from the latest pulse time TI.
4, and calculate the average pulse period '■゛6 by dividing this '4 by the pulse count number N (S8).Then, the latest pulse time T1 is set as the time 1゛5 at the end of averaging.
(S9), and changes the value of the predetermined number (Nmax) to the value obtained by adding the prime number α to the current number of pulses N (SIO
). Also, in order to limit the maximum value of Nmax, Nmax
is compared with a predetermined value β, and if it is thicker than β, a process is performed to clamp it to the value of β (Sll, 312). When the averaging process is completed, the pulse count number N is cleared to zero and the next (S13).

Further, as shown in the flowchart of FIG. 8, the microprocessor 9 performs ""f + (
From the known relational expression 1-6), the average air flow rate Q is determined from the average pulse period T6 (S 20 ), and Tmax =
Processing is performed to change the value of 'J''may according to the engine speed using the relational expression f 2 (engine speed) (a relational expression such that Tmax decreases as the engine speed increases) (S 21 ). .

Furthermore, by the relational expression Nm1n = f 3 (1/T6X engine rotation speed) (a relational expression in which the value is 1 for example at a small flow rate and increases to 3 for example as the flow rate increases from medium to large), N
Change the value of m4 (522), α-f4 (1/T6X
The increase value α of the predetermined value (Nmax) is changed according to a relational expression (a relational expression that is small, for example, 1 when the flow rate is small, and increases to 4, for example, as the flow rate increases from medium to high) (S23). The reason why the value of α is increased when the flow rate is large is because the number of output pulses of the Kalman sensor generated per cycle of fluctuation becomes large at locations where the fluctuation range of the instantaneous air flow rate is large. In addition, the average circle period formation determines whether or not it is in an accelerated state based on the rate of change of the average air flow rate, etc. (524), and if it is in an accelerated state, a process is performed to reduce α by 1 (S25).
Step S26. S27 is a process for clamping the value of α to 1. 4B. Since 1/T6x engine rotation speed is Q/n (Q: average inflow air fl, n is engine rotation speed), the latter is used as a parameter to determine the magnitude of the flow rate. May be used for

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention provides an apparatus for detecting the average air flow rate flowing into an internal combustion engine based on the period of a pulse signal generated from a Karman vortex air flow sensor at a timing related to the generation of a Karman vortex. The pulse number counting means counts the number of the generated pulse signals, and the pulse period detection means counts the period of the generated pulse signals, and the pulse number counting means calculates a predetermined number (N ma
x) pulses are counted or the pulse number counting means counts a predetermined number (Nmin) smaller than a predetermined number (Nmax).
) is counted, and each time a period longer than a predetermined time (Tmax) is detected by the pulse period detecting means, the average circular period is calculated to calculate the average air flow rate. When the fluctuation in flow rate 'IQ is large, the pulse interval (
Since a state with a large number of pulses (period) appears every cycle of fluctuation in the instantaneous air flow rate, and the interval (period) of the output pulses of the Kalman sensor at the time of a small flow rate is generally large, as in the present invention, a state in which the pulses are Basically, the average is calculated every time a predetermined number (Nmin) (II
If a cycle larger than a predetermined value (Tmax) is detected after ordering pulses, the average is calculated before the number reaches N, then during large flow rates with large fluctuation range, large cycles will continue as shown in Figure 3 (b). Even if the flow rate is low, the average is calculated for each cycle of fluctuation, and at low flow rates, the average is calculated for each pulse due to the Kalman sensor. It becomes possible to increase the average period of Further, even when the flow rate is medium, an average is calculated for at least every Nmaχ. As described above, according to the present invention, it is possible to calculate the average cycle of the output pulses of the Kalman sensor and the average air flow rate with good responsiveness both at low and high flow rates by simply processing the output signal of the Kalman sensor. becomes.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the throttle valve opening and fluctuations in the instantaneous air flow rate flowing into the internal combustion engine, and Figure 2 shows the instantaneous air flow rate at a large flow rate and the state of the output pulse of the Kalman sensor at that time. FIG. 3 is a diagram showing the state of the output pulse of the Kalman sensor at the time of a large flow rate, FIG. 4 is an explanatory diagram of the configuration of the present invention, and FIGS. 7 is a block diagram of a main part of an embodiment of the present invention, FIG. 8 is a flowchart showing an example of interrupt processing of the microprocessor 9, and FIG. 9 is a flowchart showing a main part of the main routine of the microprocessor 9. 2 is an internal combustion engine, 2 is an air cleaner, 3 is a Kalman sensor, 4 is a throttle chamber, 5 is an intake manifold, 6 is an electromagnetic fuel injector, 7 is a throttle valve that controls the flow of intake air, 8 is a crank angle sensor, 9 is a microbe I sensor, 10 is a memory, 11 is a data input section, and 12 is a data output section. Patent Applicant Fujitsu Ten Ltd. Representative Patent Attorney Tamamushiku Go 1 person outside the department 1 Fig. 2 Fig. 3 Fig. 4 Fig. 7 Fig. 8 Fig. 9

Claims (1)

[Claims] (1) In a device for detecting the average flow rate of air flowing into an internal combustion engine based on the period of a pulse signal generated from a Karman vortex air flow sensor at a timing related to the generation of a Karman vortex, A pulse number counting means for counting the number of the pulse signals, and a pulse period detection means for counting the period of the generated pulse signal, and a predetermined number (Nma) of pulses are counted by the pulse number counting means. Alternatively, the pulse number counting means calculates a predetermined number (Nn+ax
) The average period generator calculates the average air flow rate every time a period longer than a predetermined time (Tmax) is detected by the pulse period detection means after a predetermined number (Nmin) smaller than ) has been counted. An average air flow rate detection device using a Karman vortex type air flow sensor. (2. In the average air flow rate detection device using a Karman vortex type air flow sensor as set forth in claim 1, the predetermined time (Tmax) is determined by engine variables such as engine rotation speed. An average air flow rate detection device using a Karman vortex type air flow sensor. (3) In the average air flow rate detection device using a Karman vortex type air flow rate sensor according to claim 1, the predetermined number (Nmax) is an average period component. An average air flow rate detection device using a Karman vortex air flow sensor, characterized in that is determined in relation to the number of pulse counts (N) when calculating the average air flow rate. (4) Claim 3 In the average air flow rate detection device using the Karman vortex type air flow sensor described above, the predetermined number (Nmtn) is a value that is small at a small flow rate and increases as the flow rate increases from a medium flow rate to a large flow rate. (5) In the average air flow rate detection device using a Karman vortex type air flow sensor according to claim 4, the predetermined number (Nmin) is calculated as the average circular period. Karman is characterized in that the change rate of the average air flow rate, etc., is corrected according to the transient state of the engine.