JPH10318031A - Intake amount detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the erroneous detection of the amount of intake air by calculating the amount of intake air flowing in an air intake passage based on, among detected outputs by a heating coil air flow meter, a detected output from a negative peak value to a positive peak value. SOLUTION: For calculating the amount of intake air, an output V as the analog value of an air flow meter 3 is read, sampled for each specified cycle and stored in a RAM 105. Then, among the stored past sampled values, a positive peak value Vmax as a top value in an intake pulsation cycle and a negative peak value Vmin as a bottom value are retrieved and whether the sampling time of Vmax is after the sampling time of Vmin or not is detected. Then, if data from a negative peak value to a positive peak value in one cycle are not continuos, intake amounts until the previous time are outputted and, if continuity is determined, the newest sampled value of the output of the air flow meter 3 stored in the RAM 105 is read and then an intake amount is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount detection apparatus for an internal combustion engine, and more particularly to an intake air amount detection apparatus for an internal combustion engine capable of preventing erroneous detection of an intake air amount when a thermal air flow meter is used for measuring an air flow rate. The present invention relates to an amount detection device.

[0002]

2. Description of the Related Art In an electronically controlled internal combustion engine, a fuel-air mixture is produced by injecting fuel corresponding to the amount of intake air from a fuel injection valve. Therefore, it is very important to measure the amount of intake air to the engine. is there. And the amount of air that the internal combustion engine takes in is
This is a very important parameter for detecting the operating state of the engine, and is generally measured by the air flow rate or air pressure in the intake passage to the engine. this house,
There are a movable vane method, a hot wire method, a Karman vortex method and the like as an air flow meter for measuring an intake air amount by an air flow rate.

[0003] Among the above-mentioned air flow meters, a hot wire air flow meter measures an intake air amount of an engine by utilizing a property that heat corresponding to a flow rate is lost when a hot wire (mainly a platinum wire) is placed in an air flow. It is installed in the intake passage on the upstream side of the throttle valve of the engine. In the measurement of the air flow rate using a hot wire air flow meter, if a platinum hot wire heated by current is placed in a flow, the hot wire temperature changes according to the air flow rate, so the current is controlled to keep this temperature constant. The air flow is measured by extracting the current as a voltage. The measurement circuit in such a hot-wire type air flow meter forms a bridge circuit with platinum hot-wire resistance, resistance for temperature compensation, etc., and controls the power supply voltage so that the equilibrium voltage is always zero so as to keep the temperature constant. It is configured.

When the intake air amount to the internal combustion engine is measured using such a hot-wire air flow meter, the actual intake air amount including intake pulsation can be detected from the air flow rate measured by the hot-wire air flow meter. Thus, it is necessary to take the average value of the measured intake air amount. Japanese Patent Laying-Open No. 57-120817 discloses a technique for averaging the output values of a hot-wire flow meter (hot-wire air flow meter) and detecting the actual intake air amount based on the average value.

[0005]

However, the pulsation of the intake air generated in the intake passage of the internal combustion engine includes a backflow component of the intake air from the internal combustion engine side. According to the technique disclosed in Japanese Patent Application Laid-Open Publication No. H11-107, this backflow component is also measured, and the intake air flow rate of the engine is excessively measured. Then, the fuel metering is performed based on the excessively measured flow rate, and the fuel supply amount becomes excessive with respect to the actual air amount, and the air-fuel ratio becomes over-rich. As a result,
Engine stalls, poor drivability, black smoke emissions,
Problems such as smoldering of the spark plug may occur.

The backflow component of the intake air is disclosed in
According to the technology disclosed in Japanese Patent No. 0817, even if the outputs of the hot-wire type air flow meters are averaged, the backflow component is included in the average value. The injection amount increases, and the air-fuel ratio becomes rich. Therefore, the present invention solves the problem of the intake air amount detection device of the internal combustion engine that measures the air flow rate using the conventional hot-wire air flow meter, without being affected by the backflow component of the intake air in the intake passage. It is another object of the present invention to provide an intake air amount detection device for an internal combustion engine that can calculate an actual intake air amount using an output value of a hot wire air flow meter.

[0007]

The features of the present invention to achieve the above object are shown below as first to fifth inventions. According to a first aspect of the invention, in an intake air amount detection device for an internal combustion engine having a hot-wire airflow meter in an intake passage, a detection output from the hot-wire airflow meter is sampled every predetermined time, and a sampling value is set to a predetermined value. Detection value storage means for storing a period, a peak value detection means for detecting a positive peak value and a negative peak value of a detection output by comparing the stored sampling value, and a negative peak stored in the detection value storage means. And an intake air amount calculating means for calculating an intake air amount flowing through the intake passage based on only the sampling value from the value to the positive peak value.

A second aspect of the invention is characterized in that, in the first aspect, the detection output of the hot wire air flow meter is
A time storage means for calculating and storing a first time from a negative peak value to a positive peak value and a second time from a positive peak value to a negative peak value; The first of the detection output from the negative peak value to the positive peak value
And dynamic range storage means for calculating and storing a dynamic range of a positive peak value to a second dynamic range from a positive peak value to a negative peak value, and a negative peak value to a positive peak value stored in the detected value storage means. The sampled values up to the value are read in the reverse order of the storage order, and the read sampled values are read out for the first and second times, the first and second times.
A substitute sampling value is created while enlarging or reducing based on the dynamic range ratio, and the output characteristic from a positive peak value to a negative peak value based on the substitute sampling value is expressed as a positive peak value from a hot-wire airflow meter.検 出 代 と し て の と し て 、 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 記憶 補 間 記憶 記憶 記憶Means is further provided,
The intake air amount calculation means includes a sampling value from a negative peak value to a positive peak value stored in the detection value storage means, and a sampling value from a positive peak value to a negative peak value stored in the substitute sampling value storage means. It is to calculate the amount of intake air flowing through the intake passage based on the sampling value.

According to a third aspect of the present invention, in the first or second aspect, there is further provided an engine speed determining means for determining whether or not the engine speed is equal to or less than a predetermined speed. Is to calculate the intake air amount of the engine based on the output from the detection value selection output means only when the engine speed is equal to or lower than a predetermined speed. According to a fourth aspect of the present invention, in an intake air amount detection device for an internal combustion engine having a hot wire air flow meter in an intake passage, a detection output from the hot wire air flow meter is sampled every predetermined time, and a sampling value is set to a predetermined value. A detection value storage means for storing a period, a peak value detection means for detecting a positive peak value and a negative peak value of the detection output by comparing the stored sampling values, and a negative value stored in the detection value storage means. Based on the sum of all the sampling values from the peak value to the positive peak value and the sampling values except the predetermined sampling period among the sampling values from the positive peak value to the negative peak value, the inside of the intake passage Intake air amount calculating means for calculating the amount of intake air flowing through,
Has been established.

According to a fifth aspect of the present invention, in a device for detecting an intake air amount of an internal combustion engine having a hot wire air flow meter in an intake passage, the hot wire air flow meter is provided upstream of an air cleaner provided in the intake passage. It has been arranged. In the first invention, the amount of intake air flowing through the intake passage is calculated based on the sampling values from the negative peak value to the positive peak value among the sampling values of the detection output by the hot-wire type air flow meter, and the intake backflow component is calculated. Since the detection output from the affected positive peak value to the negative peak value is not reflected in the calculation of the intake air amount, erroneous detection of the intake air amount can be prevented.

In the second invention, as in the first invention, the stored sampling values are used from the negative peak value to the positive peak value, but the stored sampling values are used from the positive peak value to the negative peak value. Since the sampled value from the negative peak value to the positive peak value is corrected and used instead, an output waveform for one cycle of the hot wire air flow meter is obtained, and this is averaged. This improves the detection accuracy of the intake air amount.

In the third invention, the calculation of the intake air amount in the first or second invention is performed only when the engine is at a low speed where the influence of the intake backflow component is large, thereby reducing the cost of the intake air amount detection device for the internal combustion engine. Can be lowered. In the fourth invention, among the detection outputs of the hot-wire airflow meter, all the detection outputs from the negative peak value to the positive peak value,
Calculates the amount of intake air flowing through the intake passage based on the sum of the detection output from the positive peak value to the negative peak value and the detection output excluding the predetermined sampling period, and detects the influence of the intake backflow component Since the output is not reflected in the calculation of the intake air amount, erroneous detection of the intake air amount can be prevented.

According to the fifth aspect of the present invention, since the hot-wire type air flow meter is disposed upstream of the air cleaner provided in the intake passage, the intake backflow component is attenuated by the volume in the air cleaner, thereby further preventing erroneous detection. be able to.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an intake air amount detecting apparatus for an internal combustion engine according to an embodiment of the present invention; FIG. 1 schematically shows an electronically controlled fuel injection type internal combustion engine provided with an embodiment of an intake air amount detection device for an internal combustion engine according to the present invention. In this figure, a hot-wire air flow meter 3 is provided in an intake passage 2 of an engine 1. The air flow meter 3 has an analog output, and has a bridge circuit formed by platinum (Pt) hot wire resistance, temperature compensation resistance, and the like. The current is controlled so as to keep the temperature of the hot wire, which varies with the air flow rate, constant, and this current is taken out as a voltage. The output of the hot wire air flow meter 3 is output from the A / D converter of the control circuit 10. The input is input to the battery 101 via an ignition switch (IG) 15.

A throttle opening sensor 19 for detecting the opening of the throttle valve 18 is provided on a shaft of the throttle valve 18 provided in the intake passage 2 of the engine 1. In the intake passage 2 downstream of the throttle opening sensor 19, a fuel injection valve 7 for supplying pressurized fuel from a fuel supply system to an intake port is provided for each cylinder. Further, a temperature sensor 17 for measuring the intake air temperature or the outside air temperature is provided in the intake passage 2 on the upstream side of the air flow meter 3 or somewhere in the engine 1. The output of the temperature sensor 17 is input to the A / D converter 101 of the control circuit 10.

The distributor 4 has a crank angle sensor 5 and 30 ° CA whose axis generates a pulse signal for detecting a reference position every 720 ° CA in terms of, for example, a crank angle (CA).
A crank angle sensor 6 for generating a pulse signal for detecting a reference position is provided every time. These crank angle sensors 5,
The pulse signal 6 functions as an interrupt request signal for fuel injection timing, a reference timing signal for ignition timing, an interrupt request signal for fuel injection amount calculation control, and the like. These signals are supplied to the input / output interface 102 of the control circuit 10, and the output of the crank angle sensor 6 is
Is supplied to the interrupt terminal of

The cooling of the cylinder block of the engine 1
The recirculating water passage 8 has a water temperature sensor for detecting the temperature of the cooling water.
A sensor 9 is provided. Water temperature sensor 9 is the temperature of cooling water
Generates analog voltage electric signal according to THW. this
The output is also supplied to the A / D converter 101. Exhaust manifold
The exhaust system downstream from Hold 11 has three exhaust gas components.
Three-way catalyst core that simultaneously purifies harmful components HC, CO, and NOx
An inverter 12 is provided. Also, exhaust manifold
11 and on the upstream side of the catalytic converter 12
The exhaust pipe 14 has an O-fuel ratio sensor O_TwoC
The sensor 13 is provided. O _TwoSensor 13 is exhaust gas
It generates an electric signal according to the oxygen component concentration in the
You. That is, O_TwoFrom the sensor 13, the air-fuel ratio is stoichiometric
Different output depending on whether the ratio is rich or lean
The voltage is A / A via the signal processing circuit 111 of the control circuit 10.
It is supplied to the D converter 101. In addition, the input / output interface
The face 102 is supplied with an IG15 on / off signal.
It is supposed to be.

In the above configuration, when the IG 15 is turned on, the electric power from the battery 16 is supplied to the air flow meter 3 and the control circuit 10 to be activated, and the air flow meter 3 starts to output. And the control circuit 1
When the program 0 is started, outputs from the air flow meter 3 and other sensors are taken into the control circuit 10, and the injector 7 and other actuators are controlled.

The control circuit 10 is constructed using, for example, a microcomputer, and includes a ROM in addition to the A / D converter 101, the input / output interface 102, and the CPU 103.
A backup RAM (B-RAM) 106 for holding information even after the 104, the RAM 105, and the IG 15 are turned off is provided, and these are connected by a bus 113.

In the control circuit 10, a down counter 108, a flip-flop 109, and a drive circuit 11
0 is for controlling the fuel injection valve 7. That is,
Basic injection amount T calculated from intake air amount and engine speed
When the fuel injection amount TAU obtained by correcting p in the operating state of the engine is calculated, the fuel injection amount TAU is reduced by the down counter 10.
8 and the flip-flop 109 is also set. As a result, the drive circuit 110 starts energizing the fuel injection valve 7. On the other hand, the down counter 10
8 counts a clock signal (not shown), and when its carry-out terminal finally becomes "1" level, the flip-flop 109 is reset, and the drive circuit 110 stops energizing the fuel injection valve 7. You. That is, the fuel injection valve 7 is energized by the above-described fuel injection amount TAU, so that an amount of fuel corresponding to the fuel injection amount TAU is sent to the combustion chamber of the engine 1.

Note that the CPU 103 generates an interrupt at A / D
After the A / D conversion of the converter 101, when the input / output interface 102 receives the pulse signal of the crank angle sensor 6, when it receives the interrupt signal from the clock generation circuit 107, and the like. By the way, the intake air flowing through the intake passage 2 is pulsating, and the pulsation is large in a low rotation region of the engine, and the pulsation includes a backflow component from the cylinder side. In the engine in which the intake air amount is measured using the hot wire air flow meter 3, when the opening of the throttle valve 18 is large when the engine is running at a low speed (at about 2000 rpm or less), the air-fuel ratio is shifted to the rich side. It is known to shift. This is due to the hot wire air flow meter 3
This is for measuring the backflow component of intake air from the cylinder side due to intake pulsation.

FIG. 2 (a) shows a hot-wire type air flow meter 3 in the engine intake air amount detecting device constructed as described above.
FIG. As can be seen from this figure, the output waveform of the hot wire air flow meter 3 is normal from the negative peak value to the positive peak value from time t1 to time t2, but is normal from time t2 to time t3. From the positive peak value to the negative peak value, the backflow component of the intake air is superimposed on the output waveform. As a result, the average value of the output waveform of the hot wire air flow meter 3 is
From the correct average value shown by the solid line, it is calculated as an average value including the backflow component shown by the broken line, and is calculated as an intake air amount larger than the actual intake air amount. As a result, the fuel amount corresponding to the large intake amount is injected, and the air-fuel ratio shifts to the rich side.

With respect to such a problem, in the present invention,
The intake backflow component from the engine side in the intake passage 2 is
Utilizing the fact that the output value of the detection result of the intake air amount of the hot-wire type air flow meter 3 appears only in the portion from the positive peak value to the negative peak value, the output waveform from the hot-wire type air flow meter 3 including this backflow component Is not used for calculating the intake air amount, and the intake air amount is calculated.

An embodiment of the procedure for calculating the intake air amount will be described below with reference to a flowchart. The calculation of the intake air amount in the present invention is executed by the control circuit 10 in FIG. FIG. 3 shows a routine for calculating the pulsation cycle of intake air. This routine is executed every predetermined time. In step 301, first, the engine speed NE is read, and in the following step 302, the engine speed NE is set to a low speed range below a predetermined speed, for example, 360
It is determined whether it is less than 0 rpm. As described above, it is known that the air-fuel ratio shifts to the rich side when the engine is running at a low speed of about 2000 rpm or less.
Since the air-fuel ratio tends to shift to the rich side even at 00 rpm or more, the engine speed in the embodiment of the procedure for calculating the intake air amount according to the present invention is increased to the high rotation side to about 3600 rpm.
pm.

When NE <3600 rpm in step 302, the routine proceeds to step 303, where the flag AFMF for executing the procedure for calculating the intake air amount according to the present invention is set to "1". on the other hand,
When NE ≧ 3600 rpm, the routine proceeds to step 304, where the flag AFMF for executing the procedure for calculating the intake air amount according to the present invention is set to “0”. AFMF = "0" indicates that the procedure for calculating the intake air amount according to the present invention is not executed.

In step 303 or step 304, a flag AF for executing the procedure for calculating the intake air amount according to the present invention.
After setting the MF, the process proceeds to step 305. In step 305, the intake pulsation cycle CY is calculated using the "engine speed-intake pulsation cycle map" obtained in advance and stored in the ROM 104, and the routine ends. The intake pulsation cycle CY is necessary for calculating the intake air amount in the present invention.

FIG. 4 shows a first example of the calculation of the intake air amount according to the present invention.
9 is a flowchart illustrating a routine of the embodiment. This routine is executed in a cycle shorter than the above-described calculation cycle of the pulsation cycle. In step 401, the output VGA of the air flow meter 3 is read and stored in the RAM 105.
That is, the output VGA of the air flow meter 3 is as shown in FIG.
As shown in (b), the analog value is sampled and taken in every cycle in which the present routine is executed in the first embodiment.
It is stored in the AM 105.

In the following step 402, the current intake pulsation cycle CY calculated in step 305 is read, and in step 403, it is determined whether or not the value of the flag AFMF for executing the procedure for calculating the intake amount of the present invention is "1". Is determined. First, the case where the value of the flag AFMF is “1” and the procedure for calculating the intake air amount according to the present invention is executed will be described. In this case, the process proceeds from step 403 to step 404. In step 404, a positive peak value Vmax which is a top value and a negative peak value Vmin which is a bottom value in the intake pulsation cycle CY are retrieved from the past sampling values stored in step 401.

In the following step 405, it is detected whether the sampling time of the positive peak value Vmax obtained by the search is later than the sampling time of the negative peak value Vmin. That is, it is detected whether or not data from a negative peak value to a positive peak value within one cycle is continuous. 1
If the data from the negative peak value to the positive peak value in the cycle is not continuous, all the latest sampling values for calculating the intake air amount are not stored in the RAM 105, and the process proceeds to step 414. Is output.

If it is determined in step 405 that the data from the negative peak value to the positive peak value in one cycle is continuous, the process proceeds to step 406 and the RAM 10
5, the output VGA sampling values of all the air flow meters 3 from the latest negative peak value Vmin to the positive peak value Vmax are read out. Then, in the subsequent step 407, all the output V
The average value Vav of the GA sampling values is calculated, and in the next step 408, the intake air amount Qp is calculated from the calculated average value Vav.

In step 409, it is determined whether or not the current intake air amount Qp calculated in step 408 is equal to the previous intake air amount Q. If Qp = Q, the routine proceeds to step 414, where the previous intake air amount Q is output. On the other hand, if Qp ≠ Q, the routine proceeds to step 410, in which the intake air amount Q up to the previous time is replaced by Qp calculated in step 408, and in subsequent step 414, this intake air amount Q is output.

On the other hand, if the value of the flag AFMF is not "1" in step 403, the flow advances to step 411. In this case, since the engine speed is high, the influence of the backflow of the intake gas is not much, and the cycle of the intake pulsation is short,
The interval at which the output value of the air flow meter 3 is sampled must also be shortened, and a high-speed arithmetic circuit is required. Therefore, in this embodiment, the engine speed is 36
When the rotation speed is equal to or greater than 00 rpm, the intake air amount Q is obtained by using all the sampling values for one cycle of the output VGA from the air flow meter 3.

Therefore, in step 411, the RAM 105
Of all the sampling values stored in the intake pulsation cycle CY are read out. Then, in the following step 412, the average value Vav of the sampling values of all the read output VGAs is calculated,
In the following step 413, the intake air amount Q is calculated from the average value Vav. The calculated intake air amount Q is used in step 414.
Is output.

FIG. 5 shows the intake air amount Q from step 404 to step 410 in the flowchart described above.
This is to explain the portion of the output VGA from the air flow meter 3 used in the calculation method. As can be seen from this figure, in the first embodiment, the air flow meter 3
The average value Vav is calculated by using the sampling value obtained by sampling the portion from the negative peak value to the positive peak value in the output VGA from. On the other hand, of the output VGA from the air flow meter 3, the portion from the positive peak value to the negative peak value indicated by the broken line that includes the intake backflow is not used for the calculation of the intake air amount Q. As the average value Vav, the average value Vav calculated from a sampling value obtained by sampling a portion from the negative peak value to the positive peak value is used as it is.

In the procedure for calculating the intake air amount Q described with reference to FIG.
Is calculated, but when the sampled value read in step 406 is not different from the previous value, the intake air amount Qp
May be advanced to step 414 without calculating. When the intake air amount Q is calculated as described above, the basic injection amount Tp is obtained by the procedure shown in FIG. That is, in step 601, the value of the intake air amount Q is read, in step 602, the engine speed NE is read, and in step 603, the basic injection is obtained from the two-dimensional map of the intake air amount Q and the engine speed NE stored in the ROM 104. The quantity Tp is calculated.

As described above, in the first embodiment, the output of the latter half from the positive peak value to the negative peak value of the output VGA of the air flow meter 3 affected by the intake backflow component is calculated as the intake air amount. Since it is not reflected in the calculation, erroneous detection of the intake air amount can be prevented. In addition, the procedure for detecting the intake air amount, which does not reflect the output of the latter half from the positive peak value to the negative peak value in the calculation of the intake air amount, is performed only in the low rotation speed portion of the engine where the influence of the intake air backflow is large. Since it is not performed in the rotating part, there is no need to prepare expensive high-speed calculation means.

Next, the second calculation of the intake air amount according to the present invention will be described.
Will be described with reference to a flowchart shown in FIG. The calculation procedure of the intake air amount Q in the second embodiment is shown in FIG.
This is a modification of the procedure from step 405 to step 410 in the flowchart of the first embodiment of the present invention described in FIG. Therefore, FIG. 7 shows only the changed part in the flowchart of FIG. The description of the other parts is the same as that of the first embodiment, and the description is omitted here.

In step 404, step 401
The positive peak value Vmax which is the top value in the intake pulsation cycle CY among the past sampling values stored in
When the negative peak value Vmin, which is the bottom value, is retrieved, the output VGA of the air flow meter 3 is inverted from the negative peak value Vmin to the positive peak value Vmax in step 701 in the second embodiment. Is determined. If the output VGA is not inverted from the negative peak value Vmin in step 701, the routine ends because it is not time to calculate the intake air amount Q.

On the other hand, if it is determined in step 701 that the output VGA has been inverted from the negative peak value Vmin, the process proceeds to step 702. In step 702, the sampling value stored in the RAM 105 is searched to find the time Tup from the latest negative peak value Vmin to the positive peak value Vmax, and the subsequent time Tup from the positive peak value Vmax to the negative peak value Vmax. The time Tdn up to the value Vmin is calculated.
In the next step 703, the potential difference Vup from the most recent negative peak value Vmin to the positive peak value Vmax is obtained by searching the sampling values stored in the RAM 105,
Subsequent positive peak value Vmax to negative peak value Vmin
Is calculated.

Next, at step 704, the RAM 105
Are read from the most recently stored negative peak value Vmin to the positive peak value Vmax, in reverse to the order of storage, and the read values of The sampling value is determined by the ratio between the time Tup and the time Tdn and the ratio between the potential difference Vup and the potential difference Vdn.
The sampling time and the size are corrected for enlargement or reduction, and are stored in the RAM 105 again in the order of the correction processing. By this correction processing, the latest positive peak value Vma
The output VGA of the air flow meter 3 from x to the negative peak value Vmin is the output VGA of the air flow meter 3 from the latest negative peak value Vmin to the positive peak value Vmax.
Is replaced by the property of

In the subsequent step 705, the RAM 10
The data at the normal sampling interval in the replacement characteristic from the latest positive peak value Vmax to the latest negative peak value Vmin of the air flow meter 3 stored in 5 is read. The value of the part without data is created by interpolating the stored values before and after that. Then, the value obtained by reading the replacement characteristics at regular sampling intervals is used as the air flow meter 3
From the most recent positive peak value Vmax to the negative peak value Vmax
RAM 104 again as a substitute sampling value up to min
Are sequentially stored.

In the following step 706, all the sampled values from the latest negative peak value Vmin to the positive peak value Vmax stored in the RAM 105 and all the substitute sampled values stored in step 705 are read. The average value Vav of the sampled value and the substitute sampled value which is output and read in step 707 is calculated. Then, in step 708, step 70
The intake air amount Q is calculated from the average value Vav calculated in step 7, and is output from step 414.

FIGS. 8A and 8B show the control procedure as described above.
This will be described with reference to the characteristic diagram of FIG. In order to make the explanation easy to understand, the negative peak value Vmi
The detection of n1 is performed at time t1, the detection of the positive peak value Vmax is performed at time t2, and the most recent negative peak value Vmin2.
Is detected at time t3, and only three samplings are performed at times ta, tb, and tc between time t1 and time t2. The state of FIG. 8A shows a state immediately after it is determined in step 701 that the output VGA has inverted from the negative peak value Vmin.

In step 702, the negative peak value Vmin1
Is calculated from the time Tup to the positive peak value Vmax and the time Tdn from the positive peak value Vmax to the negative peak value Vmin2. In step 703,
A potential difference Vup from the negative peak value Vmin1 to the positive peak value Vmax and a potential difference Vdn from the subsequent positive peak value Vmax to the negative peak value Vmin2 are calculated.

In step 704, the negative peak value Vmin1
To the positive peak value Vmax.
B, C are read out in the order of C, B, A, which is opposite to the storage order, and the read sampled values C, B, A are
Ratio of time Tup to time Tdn, and potential difference Vup and potential difference Vdn
, The sampling time and size are expanded,
Alternatively, the RAM 1 is re-corrected in the order of the correction processing and the correction processing.
05 is stored.

For example, as for the sampling value C when Tup <Tdn and Vup <Vdn, as shown in FIG. 8B, the time d from time tc to time t2 is equal to the time T.
Time D is expanded by the ratio Tup / Tdn between the up and time Tdn, and the potential difference e from the negative peak value Vmin1 of the sampling value C is expanded by the ratio Vup / Vdn of the potential difference Vup and the potential difference Vdn to become the potential difference E. . And the sampling value C is
The sampling value C 'is stored in the RAM 105 as a sampling value C' at a position separated from the time t2 by the time D and located at a position larger than the negative peak value Vmin2 by the potential difference E.

With the sampling values C ', B', and A 'corrected in this manner, the true output V of the air flow meter 3 from the positive peak value Vmax to the negative peak value Vmin2 is obtained.
The characteristics of the GA (shown by a broken line G) are replaced by the characteristics that are the same as the characteristics of the output VGA of the air flow meter 3 (shown by a solid line F) from the negative peak value Vmin1 to the positive peak value Vmax, but turned over. , And the characteristics shown by the solid line H.

At step 705, the replacement characteristic H from the positive peak value Vmax to the negative peak value Vmin2 of the air flow meter 3 stored in the RAM 105 is changed to the negative peak value V
It is read out at the same sampling interval as from min1 to the positive peak value Vmax. That is, data on the normal sampling interval in the replacement characteristic H is calculated. The value of the part without data is created by interpolating the stored values before and after that. For example, data at point M corresponding to time tm is:
It is calculated by interpolating the positive peak value Vmax and the sampling value C '. Similarly, data at point N corresponding to time tn, data at point O corresponding to time to, data at point P corresponding to time tp, and data Q at a point corresponding to time tq are calculated. Then, the values M, N,
O, P and Q are positive peak values V of the air flow meter 3.
The sampling values are alternately stored in the RAM 105 again as substitute sampling values from max to the negative peak value Vmin1.

In the following step 706, all the sampling values Vmin1, A, B, C, V from the negative peak value Vmin1 to the positive peak value Vmax stored in the RAM 105 are stored.
max and all substitute sampling values M, N, O, P, Q
And the negative peak value Vmin2 is read out,
In step 7, an average value Vav is calculated from these values. Then, in step 708, the intake air amount Q is calculated from the average value Vav and output from step 414.

As described above, in the second embodiment, the detection output from the positive peak value to the negative peak value is changed to the sampling value from the negative peak value to the positive peak value in the first embodiment. Since the corrected waveform is used instead, an output waveform for one cycle of the hot-wire air flow meter is obtained. By averaging the output waveform, the detection accuracy of the intake air amount is improved.

FIG. 9 shows a third example of the calculation of the intake air amount according to the present invention.
FIG. In the first embodiment described above,
As described with reference to FIG. 5, of the output VGA from the air flow meter 3, only the sampled value obtained by sampling the portion from the negative peak value to the positive peak value between time t1 and time t2 is used and the average value is used. Vav was calculated, and the average value Vav calculated from time t1 to time t2 was used as it is between time t2 and time t3.

On the other hand, between the positive peak value and the negative peak value, the occurrence time tr of the portion indicated by the broken line in the output VGA from the air flow meter 3 that includes the intake backflow component
And the end time ts may be known in advance according to the engine speed. In such a case, time tr and time t
Only the actual sampling value obtained in the sampling period during s need not be used for calculating the intake air amount Q.

That is, the method of calculating the average value Vav in the third embodiment will be briefly described. First, a time tr when the sampling value detected according to the engine speed is not used is used.
And a time ts at which use is resumed. Next, of the sampling values for one cycle obtained from the time t1 to the time t3, the sampling values excluding only the sampling values obtained in the sampling period between the time tr and the time ts are read. Time tr and time t
The sampling value in the sampling period during s is
For example, the output VGA from the air flow meter 3 during this time
However, as shown by the two-dot chain line in FIG. 9, the sampling value Vtr at time tr and the sampling value V at time ts
As a value that changes linearly between ts, a value calculated and calculated for each sampling period is used as a substitute value.

Then, the actual sampling value obtained in the sampling period from time t1 to time tr and the sampling period from time ts to time t3 is combined with the substitute sampling value from time tr to time ts obtained by calculation. In the third embodiment, the average value Vav from time t1 to time t3 is calculated. As described above, in the third embodiment, the substitute value is used only for the portion of the output VGA from the air flow meter 3 that includes the intake backflow component.
The substitute portion of the output waveform for one cycle of the hot wire air flow meter is reduced, and by averaging this, the detection accuracy of the intake air amount is improved.

FIG. 10 shows a fourth embodiment of the calculation of the intake air amount according to the present invention. The fourth embodiment is the first,
Unlike the second embodiment, the arrangement of the hot wire type air flow meter 3 in the intake passage 2 is changed. The arrangement of the air flow meter 3 in the intake passage 2 in the fourth embodiment can be applied to any of the first and second embodiments. Further, the effect can be obtained only by disposing the air flow meter 3 of the fourth embodiment in the intake passage 2.

As shown in FIG. 1, in the first and second embodiments, the air flow meter 3 is provided between the air cleaner (not shown) in the intake passage 2 and the throttle valve 18. In addition, a surge tongue may be provided in the intake passage 2 upstream of the intake manifold of the engine 1, but the surge tank has no capacity to absorb large intake pulsations. As a result, the output characteristics from the air flow meter 3 were as shown in FIG. 2A, and the air flow meter 3 detected the backflow component of the intake air in the characteristics from the positive peak value to the negative peak value.

Therefore, in the fourth embodiment, as shown in FIG.
Is provided on the upstream side. Along with the transfer of the air flow meter 3, a temperature sensor 17 for measuring the outside air temperature is also transferred near the air flow meter 3. The arrangement of the other members in FIG. 10 is exactly the same as that in FIG.
The same components are denoted by the same reference numerals, and description thereof is omitted.

In the fourth embodiment, the intake air flowing backward in the intake passage 2 due to the intake pulsation is attenuated by the volume of the air cleaner 20, so that the reverse flow component of the intake air hardly propagates upstream of the air cleaner 20. This state is shown in FIG. In FIG. 11, the characteristics indicated by broken lines are the first and second characteristics.
This is the output characteristic from the air flow meter 3 in the third embodiment, and the characteristic indicated by the solid line is the output characteristic from the air flow meter 3 in the third embodiment.

As can be seen from the characteristics shown in FIG. 11, the output waveform from the air flow meter 3 disposed on the upstream side of the air cleaner 20 has a waveform having a regular peak value, and the influence of the backflow component of the intake air is hardly observed. The average value shown by the dashed line is also stable. Further, when the hot-wire type air flow meter 3 is arranged on the upstream side of the air cleaner 20, the combustion gas flows back to the intake manifold side when the engine valve overlaps, and the combustion gas, fuel, oil mist from the blow-by gas reduction device and water vapor, etc. The phenomenon in which the measurement accuracy is gradually reduced due to the attachment to the heat wire of the air flow meter 3 can be prevented by the air cleaner 20. As a result, the hot wire air flow meter 3 can maintain high measurement accuracy for a long period of time.

[0060]

As described above, the apparatus for detecting the amount of intake air for an internal combustion engine according to the present invention has the following effects.
In the first invention, the amount of intake air flowing through the intake passage is calculated based on the detection output from the negative peak value to the positive peak value among the detection outputs of the hot-wire type air flow meter, and is affected by the intake backflow component. Since the detection output from the positive peak value to the negative peak value is not reflected in the calculation of the intake air amount, erroneous detection of the intake air amount can be prevented.

According to a second aspect, in the first aspect, the detection output from the negative peak value to the positive peak value uses a sampling value of the detection output, and the detection output from the positive peak value to the negative peak value is used. The output will be replaced with the sampled value from the negative peak value to the positive peak value with correction.
An output waveform for one cycle of the hot wire air flow meter is obtained, and by averaging the output waveform, the detection accuracy of the intake air amount is improved.

In the third invention, the calculation of the intake air amount in the first or second invention is executed only when the engine is at a low speed where the influence of the intake backflow component is large, so that the cost of the intake air amount detection device for the internal combustion engine is reduced. Can be lowered. In the fourth invention, among the detection outputs of the hot-wire airflow meter, all the detection outputs from the negative peak value to the positive peak value,
Calculates the amount of intake air flowing through the intake passage based on the sum of the detection output from the positive peak value to the negative peak value and the detection output excluding the predetermined sampling period, and detects the influence of the intake backflow component Since the output is not reflected in the calculation of the intake air amount, erroneous detection of the intake air amount can be prevented.

In the fifth aspect, the hot-wire type air flow meter is disposed upstream of the air cleaner provided in the intake passage, so that the intake backflow component is attenuated by the volume in the air cleaner, thereby further preventing erroneous detection. be able to.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electronically controlled internal combustion engine provided with an intake air amount detection device of the present invention.

2A is a waveform diagram showing output characteristics of a hot-wire air flow meter in the intake passage of FIG. 1, and FIG. 2B is a diagram for explaining sampling of the output characteristics of FIG.

FIG. 3 is a flowchart showing a procedure for calculating a pulsation cycle of intake air according to the present invention.

FIG. 4 is a flowchart showing a procedure for calculating an intake air amount according to the first embodiment of the present invention.

FIG. 5 is a waveform diagram illustrating a procedure for detecting intake air in FIG.

FIG. 6 is a flowchart showing a basic injection amount calculation procedure.

FIG. 7 is a partial flowchart showing a procedure for calculating an intake air amount according to a second embodiment of the present invention.

8 (a) and 8 (b) are waveform diagrams specifically explaining the control procedure of the flowchart of FIG. 7;

FIG. 9 is a waveform diagram illustrating the operation of the intake air amount detection device according to the third embodiment of the present invention.

FIG. 10 is an overall configuration diagram of an electronically controlled internal combustion engine including an intake air amount detection device according to a fourth embodiment of the present invention.

FIG. 11 is a waveform diagram illustrating the effect of the embodiment of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Intake passage 3 ... Hot wire type air flow meter 7 ... Fuel injection valve 10 ... Control circuit 20 ... Air cleaner

Claims (5)

[Claims] 1. An intake air amount detection apparatus for an internal combustion engine having a hot-wire air flow meter in an intake passage, wherein a detection output from the hot-wire air flow meter is sampled at predetermined time intervals, and the detected value is stored for a predetermined time period. A storage unit, a peak value detection unit that detects a positive peak value and a negative peak value of the detection output by comparing the stored sampling values, and a positive value from the negative peak value stored in the detection value storage unit. An intake air amount detection device for an internal combustion engine, comprising: intake air amount calculation means for calculating an amount of intake air flowing through the intake passage based only on the sampling value up to a peak value. 2. The intake air amount detection device for an internal combustion engine according to claim 1, wherein a first time from a negative peak value to a positive peak value of a detection output from the hot wire air flow meter is determined. Time storage means for calculating and storing a second time from a peak value to a negative peak value, and a first time from a negative peak value to a positive peak value of a detection output from the hot wire air flow meter. Dynamic range storage means for calculating and storing a dynamic range and a second dynamic range from a positive peak value to a negative peak value; and a negative peak value to a positive peak value stored in the detected value storage means. Reading the sampled values up to a value in the reverse order of their storage order, and expanding the read sampled values based on the ratio between the first and second times and the first and second dynamic ranges, or Alternatively, a substitute sampling value is created while reducing, and the output characteristic from the positive peak value to the negative peak value by this substitute sampling value is substituted for the positive peak value to the negative peak value from the hot wire air flow meter. And a substitute sampling value storage unit for calculating and storing a substitute sampling value from a new positive peak value to a negative peak value using interpolation at the same sampling time as the detection output, further comprising: The amount calculating means includes a sampling value from a negative peak value to a positive peak value stored in the detection value storing means, and a negative peak value from a positive peak value stored in the substitute sampling value storing means. An intake air amount detection device for an internal combustion engine, wherein the intake air amount flowing through the intake passage is calculated based on the sampling values up to. 3. The intake air amount detection device for an internal combustion engine according to claim 1, further comprising an engine speed determination unit configured to determine whether an engine speed is equal to or lower than a predetermined speed, wherein the air amount calculation unit. Comprises: calculating an intake air amount of the engine based on an output from the detection value selection output means only when the engine rotational speed is equal to or less than a predetermined rotational speed. 4. An intake air amount detection device for an internal combustion engine having a hot-wire air flow meter in an intake passage, wherein a detection output from the hot-wire air flow meter is sampled at predetermined time intervals, and the detected value is stored for a predetermined time period. A storage unit, a peak value detection unit that detects a positive peak value and a negative peak value of a detection output by comparing the stored sampling values, and a positive value from a negative peak value stored in the detection value storage unit. And flows through the intake passage based on the sum of all the sampling values up to the peak value and the sampling value of the sampling values from the positive peak value to the negative peak value excluding a predetermined sampling period. An intake air amount detection device for an internal combustion engine, comprising: intake air amount calculation means for calculating an intake air amount. 5. An intake air amount detection device for an internal combustion engine having a hot wire air flow meter in an intake passage, wherein the hot wire air flow meter is disposed upstream of an air cleaner provided in the intake passage. An intake air amount detection device for an internal combustion engine.