JPH06100150B2 - Engine intake air amount detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intake air amount detection device for detecting an intake air amount supplied to an engine.

(Prior Art) Conventionally, when the intake air amount supplied to the engine is detected by a heat ray provided upstream of the throttle valve or an intake air amount sensor such as a negative pressure sensor provided downstream of the throttle valve,
In order to remove the pulsation component and the like from the detection signal, the output of the intake air amount sensor is sampled for a predetermined period, the sampled output values are averaged, and a technique for obtaining the intake air amount from the average value is, for example, JP 58-1605
It is known as can be seen in No. 18.

Then, in the sampling in the averaging of the output values, for example, sampling is started for each top dead center and the average value is obtained, but the detection accuracy may be low in relation to pulsation. . That is, in the case where the pulsation cycle deviates from the engine rotation cycle due to the fluctuation of the engine rotation speed, and the sampling start or end timing and the peak or trough of the fluctuation of the pulsation match. , The sampling first value or the final value is large. Further, due to the relationship between the unit time of sampling and the pulsation cycle, sampling cannot be detected only during the period corresponding to one cycle of pulsation, and extra sampling or insufficient sampling occurs at the time of ending the sampling. However, since the sampling values of the excess and deficiency are large, the average value deviates from the true average value due to the influence, and the detection accuracy decreases.

(Object of the Invention) In view of the above circumstances, the present invention improves the accuracy of detecting the intake air amount by performing a highly accurate averaging process for averaging the sampling of the output values of the intake air amount sensor to detect the intake air amount. It is an object of the present invention to provide an intake air amount detection device for an engine.

(Structure of the Invention) The intake air amount detection device of the present invention detects the intake air amount by sampling the output of the intake air amount sensor for a predetermined period and averaging the sampled output values, and starts the predetermined period of the sampling. The time is set to a time when the output value of the intake air amount sensor is close to the average value.

(Effect of the Invention) According to the present invention, the sampling start time of the intake air amount sensor output is set to a time when the intake air amount sensor output is close to the average value. Even if there is an excess or deficiency of sampling, the effect on the average value is small and accurate averaging processing can be performed, and the intake air amount can be detected with high accuracy and various engine controls can be executed well. Is something that can be done.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an engine equipped with the intake air amount detection device of the present invention.

The intake air amount detection device 1 includes an intake air amount sensor 5 based on a heat ray that is provided upstream of the throttle valve 4 in the intake passage 3 that supplies intake air to the engine body 2. This intake air amount sensor 5
The detection output of is input to the control unit 9 together with the output of the throttle opening sensor 6 that detects the throttle opening and the detection output of the crank angle sensor 8 that detects the rotation of the crankshaft 7.
The amount of intake air is calculated at, and the fuel injection pulse is output to the injector 10 based on the amount of intake air to control the fuel supply.

The control unit 9 starts the sampling of the output of the intake air amount sensor 5 from the vicinity of the average value of the output, and after sampling for a predetermined period, averages the sampled output values to obtain the intake air amount. Further, at the sampling start time, since the intake pulsation varies according to the engine speed, the sampling start time is adjusted according to the engine speed, and
Since the influence of pulsation is small when the throttle opening is small, the sampling start timing is fixed when the throttle opening is a predetermined opening or less.

That is, as shown in FIG. 2, the output of the intake air amount sensor 5 is affected by pulsation and fluctuates in a wave shape, and the phase of the average value position deviates from TDC by a predetermined time T in response to the engine speed. The control unit 9 delays the sampling start time from the time when the TDC signal is input from the crank angle sensor 8 by a predetermined delay time T experimentally obtained in advance corresponding to the engine speed at that time and outputs it. Sampling is started at a time when the value is close to the average value Es, sampling is performed at a predetermined sampling time t, and the sampled output values are averaged to obtain an average intake air amount.

FIG. 3 shows the internal structure of the control unit 9, which includes CPU 12, ROM 13, RAM 1.
4, the detection output of the intake air amount sensor 5 and the throttle opening sensor 6 is input via the input circuit 15, the multiplexer 16 and the A / D converter 17, and further,
The signal from the crank angle sensor 8 is input to the CPU 12 as a TDC interrupt signal via the input circuit 18, the interrupt signal is input from the free running counter 19 every 1 msec, and the signal from the subtraction counter 20 is input. To be done. As a control result output, a fuel / fuel injection control signal is output to the injector 10 via the timer 21 and the drive circuit 22.

The operation of the control unit 9 will be described based on the flowchart of FIG. FIG. 4A is a main routine. After the start, the initial value is set in step S1 to set an initial value, and the fuel injection amount P is calculated from the average intake flow rate Vs and the rotational speed, which will be described later, in step S2.

FIG. 4B is a TDC interrupt processing routine, and step S3
Calculate the engine speed from the interrupt cycle in step S4
Read the throttle opening from the throttle opening sensor 6. Next, in step S5, the sampling delay time T in the average calculation of the intake air amount is calculated from the throttle opening and the engine speed. In the calculation of the delay time T, since the pulsation cycle is delayed with the increase of the engine speed, the reference delay time T ₀ is increased with respect to the increase of the engine speed as shown in FIG. 5A. It is set. Further, since the influence of the output of the intake air amount sensor 5 due to the pulsation does not become a problem unless the throttle opening is larger than a certain degree, the delay coefficient K is set at a predetermined throttle opening or more as shown in FIG. 5B. The delay time T is obtained by multiplying the reference delay time T ₀ obtained from the rotational speed according to FIG. 5A by the delay coefficient K obtained from the throttle opening.

After the delay time T obtained in step S5 is set in the subtraction counter 20 in step S6 as described above, the subtraction counter set flag F is set in step S7, and the fuel injection amount P calculated in step S2 is set in step S8. The fuel injection is set based on The subtraction counter 20 subtracts the set value to 0 at regular intervals to
Stop when it becomes.

FIG. 4C shows a 1 msec interrupt processing routine, and step S
The output value of the intake air amount sensor 5 is read in 9 and the output value of the intake air amount sensor 5 is converted into the intake air flow rate Vo in step S10 based on the relationship between the intake air amount sensor output and the flow rate characteristic which are obtained in advance. In step S11, calculate the total SUM of this flow rate Vo,
In step S12, the sampling data number N is updated.
A step S13 decides whether or not the subtraction counter set flag R is set, and when the flag F is being set during the subtraction, the subtraction count value is read in the step S14, and the subtraction count value is read in the step S15. It is determined whether or not it has become 0. When the subtraction count value becomes 0, the flow rate total SUM and the number of sampling data N are calculated in step S16.
After calculating the average air flow rate Vs from the above, the register of the total flow rate SUM and the number of data N is cleared for the next flow rate calculation in step S17, and the subtraction counter set flag R is reset in step S18.

That is, when the subtraction counter reaches 0, sampling is started and the intake air amount sensor output is accumulated every 1 msec.
Until the DC signal is input and the flag F is set, the above sampling is repeated based on the NO determination in step S13. After the predetermined delay time T is set in the subtraction counter 20 and the flag F is set according to the input of the TDC signal, the same sampling as above is performed until the subtraction counter 20 becomes 0 based on the NO determination in step S15. Accumulate data. Then, when the value of the subtraction counter 20 becomes 0 and a predetermined delay time T has elapsed, the accumulation of sampling is finished and the average value Vs is obtained.

With the above configuration, the time point for averaging the sampling of the intake air amount sensor 5 can be set in the vicinity of the average value, and the error of the average value due to the variation of the sampling number in the vicinity of the time of obtaining the average value can be reduced. You can

In the above embodiment, an example of a sensor that uses a hot wire as the intake air amount sensor is shown, but a negative pressure sensor or the like may be used as the intake air amount sensor. Is applicable when the sensor output is affected by intake pulsation and requires averaging processing, and the accuracy of the averaging is improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine equipped with an intake air amount detection device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of sampling and averaging intake air amount sensor outputs, and FIG. 3 is a control unit. Fig. 4A, B, C are flow charts for explaining the operation of the control unit. Fig. 5A, B are for engine speed and throttle opening for determining the delay time. It is a characteristic view which shows a relationship. 1 ... Intake amount detection device, 2 ... Engine body 3 ... Intake passage, 4 ... Throttle valve 5 ... Intake amount sensor 9 ... Control unit

Claims (1)

[Claims] Claims: 1. By sampling the output of an intake air amount sensor such as a heat ray provided upstream of the throttle valve of the engine or a negative pressure sensor provided downstream of the throttle valve for a predetermined period, and averaging the sampled output values. In the intake air amount detection device of the engine that detects the intake air amount,
An intake air amount detection device for an engine, wherein a start timing of a predetermined period of the sampling is set to a timing when an output value of the intake air amount sensor is close to an average value.