JPH0432973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an apparatus 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.

Prior Art and Problems Generally, in an internal combustion engine, the intake air amount is measured, and the fuel injection amount is controlled based on the measurement result so that the air-fuel ratio is constant. Various measurement devices have been proposed to measure the amount of intake air, but one of them is the Karman vortex air flow sensor (hereinafter referred to as the Karman sensor), which has excellent responsiveness.
is 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. The pulse signal is detected by means of the above method and a pulse is generated at a timing related to the generation of the Karman vortex, and the period of the pulse signal of this invention 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 slot valve, the greater the range of variation. Since the Kalman sensor has sufficient responsiveness to follow such fluctuations, for example, as shown in Figure 2,
When the throttle valve opening is large and the flow rate is large, the pulse train includes a pulse train with a very short cycle that occurs during a period when the flow rate is large, and a pulse train that has a relatively short cycle that occurs during a period when the flow rate is small. Therefore, it is necessary to use some method to find the average pulse period.

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 to obtain an average 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, the period p
If the start and end points are set in the middle of a large cycle, as shown by symbol p ₁ in Figure 2, it becomes impossible to measure these large cycles,
The averaging error becomes too large. Therefore, as shown by the symbol p ₂ in Fig. 2, the period p is larger than the period tl.
However, the period of the pulse at the beginning and end of the period p cannot be measured and an error remains, and normally the pulses can be counted after detecting the start point of the period p. Since there is inevitably some delay time, setting the starting point at a place where the pulse period is extremely short will lead to an error in counting the number of pulses, and this error will also be added to the problem.

Purpose of the Invention The present invention has been made to improve these conventional drawbacks.The purpose of the present invention is to accurately detect the average of the Kalman sensor output pulse period for each fluctuation during a large flow rate where the instantaneous air flow rate fluctuates rapidly. It's about trying to get it.

Principle, structure, and operation of the invention In general, in a Kalman sensor, when the fluctuation range is large during a large flow rate, multiple pulses appear and the pulse interval (period) is large, as shown in Fig. 2. It appeared every cycle of flow rate fluctuation. Therefore, if you calculate the average period every time a period larger than a predetermined value (Tmax) appears,
When the flow rate is large and has a large fluctuation range, the average can be calculated for each period of fluctuation. That is, when the flow rate is large, a pulse train as shown in Figure 3a is generated, so
If we calculate the average period every time a large period appears, averaging will be performed at intervals as shown by the symbol Q,
The interval coincides with one fluctuation cycle of the instantaneous air flow rate. However, in reality, as shown in Figure 3b, a relatively long cycle sometimes appears after a large cycle, and when this exceeds a predetermined value (Tmax), averaging is performed as shown by Q' in the figure. is performed, and there are cases where the instantaneous air flow rate is not accurately averaged for each cycle of variation. The present invention takes this point into consideration, and does not necessarily calculate the average period when a period larger than a predetermined value (Tmax) appears, but instead calculates the predetermined number of pulses (Nmin) from the previous average processing end pulse. After the specified value (Tmax)
Averaging processing is performed only when a larger period appears. In this way, even if pulse P2 appears after a relatively long interval after pulse P1, as shown in Figure 3b, it will be ignored since the previous average ending pulse is P1 in this case.
Averaging processing is performed when pulse P3 is detected. Therefore, it is 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, by doing as described above, when the flow rate is small, an average is calculated for every predetermined number (Nmin) of pulses of the Kalman sensor, and averaging can be performed with relatively good responsiveness.

However, at medium flow rates, the pulse period is mostly smaller than an appropriate predetermined value (Tmax). For this reason, it becomes difficult to perform averaging at medium flow rates by simply finding the average period every time a period larger than a predetermined value (Tmax) appears after a predetermined number (Nmin) of pulses are generated.

Therefore, in the present invention, the average is calculated every time a predetermined number (Nmax) of pulses appear, and if a cycle larger than a predetermined value (Tmax) after a predetermined number (Nmin) of pulses is detected,
The average is calculated before the number reaches Nmax. In this way, it is possible to obtain the average period of the output pulses of the Kalman sensor with good responsiveness at both low and high flow rates, and at medium flow rates, the average can be calculated for at least every N pulses even if no period greater than Tmax appears. It will be done.

FIG. 4 is an explanatory diagram of the configuration of the present invention, in which a pulse signal generated from the Karman sensor CS at a timing related to the generation of Karman vortices is input to the average period or average air flow rate calculation means AT. The pulse number counting means CN is for counting the pulses output from the Kalman sensor CS, and is a predetermined number (Nmin).
When a predetermined number (Nmax) has been counted, a calculation command is issued to the calculation means AT. Pulse period detection means
PD measures the period of the output pulse of the Kalman sensor CS and detects a period larger than a predetermined value (Tmax).When detected, it is notified to the predetermined period detection means.
Notify DE. The predetermined period detection means DE detects a predetermined number of pulses (Nmin) by the pulse number counting means CN and then detects a period equal to or greater than a predetermined value (Tmax) by the pulse period detection means PD.
Issue a calculation command to AT. This calculation means AT is
The average period or average air flow rate is calculated every time a calculation command is issued from the pulse number counting means CN or from the predetermined period detecting means DE.

FIG. 5 is an explanatory diagram of the operation of the present invention, in which (a) shows an example of a temporal change in the instantaneous air flow rate, and (b) shows an example of the output pulse of the Kalman sensor at that time. In addition, t1 to t48 are each output pulse of the Kalman sensor,
Q1-Q8 indicate averaged air flow rates. According to the configuration shown in Figure 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). ), at low flow rates, the period of the output pulse of the Kalman sensor CS is longer than the predetermined time (Tmax), but due to the limitation of a predetermined number (Nmin, here 3), averaging is performed every 3 pulses of the Kalman sensor CS. (See Q1, Q2, 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) (see Q3 and Q4).

In FIG. 5, when changing 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, set a predetermined number (Nmax) in relation to the count value of the pulse number counting means CN when calculating the average.
may be increased sequentially within a predetermined range. Also,
For example, the predetermined number (Nmin) is set to 1 when the flow rate is small.
By increasing the value to 3, for example, as the flow rate increases, it becomes possible to average each pulse at a low flow rate. 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 averages Q1 and Q2 at small flow rates in Fig. 5 are
is subdivided into average Q10, Q11, Q12 and Q20, Q21, Q22, respectively, and average Q3 at the time of transition from small flow rate to medium flow rate is subdivided into Q30 and Q31. In this example, the predetermined number (Nmax) is sequentially increased by 3, but the rate of increase is arbitrary.

Furthermore, it is preferable to make the increase rate of the predetermined value (Nmax) a little smaller during acceleration, since the response will be better in transient situations, especially when the flow rate rapidly changes from a small flow rate to a large flow rate.

Furthermore, the period of fluctuation of the air flow rate is determined by the engine rotational 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, also inevitably differs. Therefore, the predetermined period (Tmax) in the pulse period detection means PD
is preferably set to an optimal value according to the engine speed at that time. That is, the higher the engine speed, the smaller the predetermined period (Tmax) is.

Embodiment of the Invention FIG. 7 is a block diagram of essential parts of an embodiment of the present invention, in which 1 is an internal combustion engine, 2 is an air cleaner, and 3 is a karma sensor, which outputs an output signal a every time a Karman vortex is generated. 1”. 4 is the slot chamber, 5 is the 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 microprocessor, 10 is a memory, and 11 is the output of the crank angle sensor 8 and other engine components. Parameters such as cooling water temperature, intake temperature, throttle valve opening, on/off information of various switches such as idle switch, etc. are sent to the microprocessor 9.
12 is a data output section.

Intake air is supplied from an air cleaner 2 to each cylinder through each branch of an intake manifold 5 via a Kalman sensor 3 and a slot chamber 4, and fuel is injected into the internal combustion engine 1 by a fuel injector 6. Further, the intake air amount changes as shown in FIGS. 5 and 6 depending on the state of the internal combustion engine, and the output signal a also changes in accordance with the change. The output signal a of the Kalman sensor 3 is connected 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 S1 to S14 indicate each step.

When the microprocessor 9 receives an interrupt, it first stores the current time as the latest pulse time T1 (S1), and increments the pulse count number N by one (S2). Next, it is determined whether the pulse count number N is greater than or equal to a predetermined number (Nmax), and if it is greater than or equal to the predetermined number (Nmax), the process proceeds to step S6.
If it is less than a predetermined number, it is determined whether it is greater than or equal to a predetermined number (Nmin) (S4). Here, if it is determined that it is less than the predetermined number (Nmin), the latest pulse time
The value of T1 is set as the interrupt time T3 one pulse before (S13), and the process returns to the main routine. Also, if it is determined that the number is greater than a predetermined number (Nmin), the latest pulse time
The current pulse period T2 is obtained by subtracting the interrupt time T3 one pulse before from T1 (S5), and it is determined whether T2 is greater than or equal to a predetermined period (Tmax) (S6). If T2 is greater than or equal to the predetermined period (Tmax), the process proceeds to step 7, and if it is less than the predetermined period (Tmax), the process proceeds to step S14.

In step S7, the inter-pulse time T4 to be averaged is obtained by subtracting the time T5 at the end of the previous averaging from the latest pulse time T1, and the average pulse period T6 is calculated by dividing this T4 by the pulse count number N. S8). Then, the latest pulse time T1 is stored as the time T5 at the end of averaging (S9), and the value of the predetermined number (Nmax) is changed to the value obtained by adding the constant α to the current number of pulses N (S10). Also, in order to limit the maximum value of Nmax, Nmax is compared with a predetermined value β,
If it becomes larger than β, processing is performed to clamp it to the value of β (S11, S12). When the averaging process is completed, the pulse count number N is cleared to zero in preparation for the next process (S13).

Further, as shown in the flowchart of FIG. 8, the microprocessor 9 calculates the average air flow rate Q from the average pulse period T6 from the known relational expression Q=f ₁ (T6) in the main routine (S20), and
According to the relational expression Tmax=f ₂ (engine speed) (a relational expression in which Tmax decreases as the engine speed increases),
Processing to change the value of Tmax is performed (S21). Furthermore, the value of Nmin is changed using the relational expression Nmin=f ₃ (1/T6×engine speed) (a relational expression in which, for example, 1 is used when the flow rate is small, and increases to 3, for example, as the flow rate increases from medium to large). S22), α=f ₄ (1/T6×
The increase value α of the predetermined value (Nmax) is changed according to a relational expression (for example, a relational expression that is small, for example, 1 when the flow rate is small, and becomes large, for example, 4, as the flow rate increases from medium to high) (engine rotation speed) (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 fluctuation period varies at locations where the instantaneous air flow rate has a large fluctuation range. Also,
It is determined whether or not the vehicle is in an accelerated state based on the average cycle or the rate of change in the average air flow rate (S24), and if it is in an accelerated state, α is reduced by 1 (S25).
Steps S26 and S27 are processes for clamping the value of α to 1. Note that 1/T6 x engine speed is equivalent to Q/n (Q is the average amount of incoming air, n is the engine speed), so instead of the former, use the latter as a parameter to determine the size of the flow rate. Also good.

Effects of the Invention As explained above, 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. comprises a pulse number counting means for counting the number of the generated pulse signals, and a pulse period detection means for counting the period of the generated pulse signal, and the pulse number counting means generates a predetermined number (Nmax) of pulses. or after the pulse number counting means has counted a predetermined number (Nmin) smaller than the predetermined number (Nmax), each time a period of a predetermined time (Tmax) or more is detected by the pulse period detection means, the average is calculated. It is designed to calculate the period or average air flow rate, and generally in Kalman sensors, when the fluctuation range is large during large flow rates, the second
As shown in Figure 3, the pulse interval (period)
A state where a large amount of air is generated appears every cycle of fluctuation in the instantaneous air flow rate, and the interval (period) of output pulses of the Kalman sensor is generally large when the flow rate is small.
As in the present invention, the average is calculated every time a predetermined number (Nmax) of pulses appear, and if a cycle larger than a predetermined value (Tmax) is detected after a predetermined number (Nmin) of pulses are generated, the If the average is calculated before the fluctuation range is large, even if there are continuous large cycles as shown in Figure 3b, the average will be calculated for each period of fluctuation, and at small flow rates, the Kalman sensor The average is calculated every several pulses of , and it is possible to obtain the average cycle of the output pulses of the Kalman sensor with good responsiveness both at low flow rates and at high flow rates. Furthermore, even at medium flow rates, the average is calculated at least every Nmax. As described above, according to the present invention, by only processing the output signal of the Kalman sensor,
It becomes possible to calculate the average cycle of the output pulses of the Kalman sensor and the average air flow rate with good responsiveness even at high flow rates.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the throttle valve opening and the instantaneous flow rate of air flowing into the internal combustion engine.
Figure 2 is a diagram showing the instantaneous air flow rate at a large flow rate and the state of the output pulse of the Kalman sensor at that time, Figure 3 is a diagram showing the state of the output pulse of the Kalman sensor at a time of large flow rate, and Figure 4 is a diagram showing the state of the output pulse of the Kalman sensor at the time of a large flow rate. 5 and 6 are explanatory diagrams of the structure of the present invention. FIG. 7 is a block diagram of a main part of an embodiment of the present invention. FIG. 8 is an example of interrupt processing of the microprocessor 9. FIG. 9 is a flowchart showing the main part of the main routine of the microprocessor 9. 1 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 slot valve that controls the flow of intake air, and 8 is a crank An angle sensor, 9 a microprocessor, 10 a memory, 11 a data input section, and 12 a data output section.

Claims (1)

[Scope of Claims] 1. In a device for detecting an average air flow rate flowing into an internal combustion engine based on the cycle 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 generated comprising a pulse number counting means for counting the number of signals and a pulse period detection means for counting the period of the generated pulse signal, and a predetermined number (Nmax) of pulses are counted by the pulse number counting means, or After the pulse number counting means counts a predetermined number (Nmin) smaller than the predetermined number (Nmax), each time the pulse period detection means detects a period longer than a predetermined time (Tmax), the average period or average air flow rate is calculated. An average air flow rate detection device using a Karman vortex type air flow sensor, characterized in that the average air flow rate is calculated by 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 an engine parameter such as engine speed. Average air flow rate detection device using a type air flow sensor. 3. In the average air flow rate detection device using the Karman vortex type air flow sensor according to claim 1, the predetermined number (Nmax) is the number of pulse counts (N) when calculating the average period or the average air flow rate. An average air flow rate detection device using a Karman vortex type air flow sensor, characterized in that the average air flow rate is determined in relation to. 4. In the average air flow rate detection device using a Karman vortex type air flow sensor according to claim 3, the predetermined number (Nmin) 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. An average air flow rate detection device using a Karman vortex type air flow sensor. 5. In the average air flow rate detection device using the Karman vortex type air flow sensor as set forth in claim 4, the predetermined number (Nmin) is calculated based on an excess of the internal combustion engine such as a calculated average period or a rate of change of the average air flow rate. An average air flow rate detection device using a Karman vortex type air flow sensor, which is characterized by correction according to the state.