JPS6397856A - Suction pipe internal air pressure detecting method for internal combustion engine - Google Patents

Abstract

PURPOSE:To make the accurate detection of suction pipe pressure attainable, by setting a sampling period to another specified value at a time when a pulsation period is less than the specified value, in case of a device, sampling the suction pipe pressure at each one a half of the pulsation period and detecting the suction pipe pressure. CONSTITUTION:A pressure sensor 13, detecting suction pipe pressure in common to each cylinder, is installed in the surge tank 4 installed in the point midway in a suction pipe 2, and the output signal is inputted into a control unit 15 together with an output signal of another sensor. At this control unit 15, suction pipe pressure PM is subjected to sampling at each 1/2 of a pulsation period t{t=h(m.n), where h: constant, m: engine speed, n: cylinder number} of air pressure inside the suction pipe 2. And, the suction pressure is detected by the arithmetical mean with at least the last sampling value. And, at this time, when the pulsation period t is less than the specified value, a sampling interval is set to (1/2+k).t (where k=1,2,...), the suction pressure is detected likewise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for measuring air pressure in an intake pipe of an internal combustion engine.

BACKGROUND ART One parameter for determining the optimal fuel injection amount, ignition timing, etc. depending on the state of the internal combustion engine is the air pressure in the intake pipe of the internal combustion engine (hereinafter referred to as intake pipe pressure).

By the way, even if the throttle opening is constant, the intake pipe pressure constantly pulsates due to the pumping action of the internal combustion engine, so it is necessary to measure the intake pipe pressure so as not to be affected by the pulsations.

Conventionally, a method for measuring intake pipe pressure without being affected by pulsation has been to use a method between a pressure sensor that directly detects the pressure in the intake pipe and an analog/digital (hereinafter referred to as A/D) converter. It is known that a filter is provided to remove the pulsation component, and the signal passed through the filter is used as the intake pipe pressure, but this method is designed to sufficiently remove the pulsation component when the engine speed is low. If the time constant of the filter is increased, it will not be possible to detect changes in intake pipe pressure with a good response when the throttle opening changes suddenly.On the other hand, if the time constant of the filter is made small in order to improve the response when the throttle opening changes suddenly, the change in intake pipe pressure will not be detected with good response. The pulsation component cannot be removed sufficiently.

Therefore, the present applicant previously proposed a solution to this problem in a patent application filed in 1983.
The application was filed as 0-251642. The outline of the invention is as follows:
The intake pipe pressure is sampled at an interval of 1/2 the pulsation period t, A/D conversion is performed, and the arithmetic average of the previous sampling value and the current sampling value is taken as the average pressure value of the intake pipe. be.

Problems to be Solved by the Invention However, according to Japanese Patent Application No. 60-251642, when the period of pulsation of the intake pipe pressure becomes short, such as when the engine speed increases, the A/D conversion process and the converted value Since the processing for calculating the arithmetic mean of , etc. increases, it places a heavy burden on the central processing unit for control (hereinafter referred to as CPU).

The present invention aims to solve these problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has the following configuration. In other words, the air pressure in the intake pipe of an internal combustion engine is calculated as 1/1 of the pulsation period of the pressure t=h (m-n) (where h: constant, m: engine speed, n: number of cylinders).
In the method of detecting the air pressure in the intake pipe by sampling every 2 times and using an arithmetic average of at least the previous sampling value, the sampling interval is set to 1 when the pulsation period t of the pressure is less than or equal to a predetermined value. It is something to do.

Effect According to the above method, when the pulsation period of the intake pipe pressure is long or the engine speed is low, sampling is performed at a period of 1/2 of the pressure pulsation, and at least the arithmetic average of the previous sampling value is calculated. Obtain the intake pipe pressure, and if the intake pipe pressure pulsates rapidly or the engine speed is high, perform sampling at a period of (1/2 + k) times the pressure pulsation (k = 1.2...), An average value of the intake pipe pressure is obtained by an arithmetic mean of at least the previous sampling value.

Therefore, when the engine speed is low, the pressure pulsation period is long, so the sampling period is also long, and a pressure value with ripples removed can be obtained without placing a burden on the control CPU.

In addition, it is possible to follow and measure sudden changes in pressure with almost no delay, so the appropriate amount of fuel injection can be determined.
Ignition timing etc. can be calculated.

On the other hand, even when the engine speed is high, the sampling period becomes longer and the time for A/D conversion processing and processing for calculating the arithmetic mean of the converted values is reduced, so ripples can be generated without putting a burden on the CPU. can be removed. At this time, since the engine is stable, there is no problem even if the measured value of the intake pipe pressure lags slightly behind the actual pressure.

Examples of the invention Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Combustion air from an air cleaner (not shown) passes through a pipe 2 to a cylinder 1 of a 4-cycle, 6-cylinder spark-ignition internal combustion engine, and then from a throttle valve 3 to a surge tank 4 for absorbing surge, and to each cylinder. The air is supplied through a branched intake manifold 5. The cylinder 1 is provided with an intake valve 6 .

Fuel is injected from the fuel injection valve 7. Electric power from the ignition coil 8 is supplied to a spark plug 10 via a distributor 9. Combustion exhaust gas from the cylinder 1 is discharged from the exhaust gas purification device 12 via an exhaust valve (not shown) and an exhaust pipe 11 . surge tank 12
A pressure sensor 13 is provided to detect the intake pipe pressure common to each cylinder. The output from the pressure sensor 13 is transmitted via a line 14 to a human-powered ink face 16 of a control device 15.
given to. In the control device 15, input ink face 1
The analog signal from 6 is converted into a digital value by an A/D converter 18 and provided to a CPU 19. The CPU 19 controls the fuel injection valve 7 and the ignition coil 8 via the output interface 20. CPU1
A memory 21 is provided in connection with 9.

A first embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2(1) shows the intake pipe pressure PM detected by the pressure sensor 13. This pressure PM is 1/2 of the pulsation period t.
PM, PMz, PM3 is sampled every cycle.
,...) By taking the arithmetic mean with the previous sampling value, a pressure value with ripples removed can be obtained.

The period t corresponds to a crank angle of 720° CA/n, where n is the number of cylinders. In this example, since there are six cylinders (n=6), the pulsation period t corresponds to 120'CA.

FIG. 2(2) shows a signal waveform representing the crank angle derived from the crank angle sensor provided in the distributor 9 to the line 17. A pulse is derived every 30" CA based on the output of the crank angle sensor. Therefore, a pressure value (P M+ , P Mz
, P Mx ,...), t/
This means that sampling can be performed every 2.

However, when the pulsation period of the intake pipe pressure becomes shorter as the engine speed increases, processing for starting sampling, calculation processing for the arithmetic mean, etc. increases, which places a negative burden on the CPU 19.

Therefore, if a predetermined time (for example, 3 m5) has not elapsed from the previous sampling time to the current sampling time, the 30° CA signal will be received six times (3/2
) ・Pressure value (P M
s, P Mb, P M? , ...)
to sample.

FIG. 3 is a flowchart showing the operation of the CPU 19 in this first embodiment. CPU19 sends the output signal of the crank angle sensor in distributor 9 to line 1.
7 and moves from step S1 to step S2,
The CADS value, which is a counter for counting the crank angle 30° CA signal, is subtracted by 1 and the process moves to step S3. In step S3, it is determined whether the counter CADS is 0, and if so, the process moves to step S4. In step S4, it is determined whether the difference between ZADS, which is the time when sampling was performed last time, and the current time is a predetermined value, for example, 3 ms or more, and if so, the process moves to step S5. In step S5, 2 is substituted into the counter CADS, and the process moves to step S6.

In step S6, in order to convert the detection output from the pressure sensor 13 into a digital value, the CPU 19 gives a signal to the A/D converter 18 via the line 22 to start an A/D conversion operation, and moves to step S7. . As a result, the A/D converter 18 samples the detection output of the pressure sensor, and
/D conversion operation is started. In step S7, ZADS is updated by substituting the current time into ZADS, and the process moves to step S9.

In step S9, processing is performed to calculate engine rotational speed and the like based on the 30° CA signal.

Here, in step S4, if the difference between the current time and the previous sampling time ZADSO is less than a predetermined value, the process moves to step S8, where 4 is substituted into the counter CADS, and the process moves to step S9.

In this way, the intake pipe pressure is normally sampled at a cycle that is l/2 times the pulsation period of the intake pipe pressure, for example, PM at time 1° in Fig. 2, PMt at time t2, etc. If the pulsation period is less than a predetermined time, PM at an interval of, for example, time t in FIG.

The intake pipe pressure is sampled as follows: , PM at time t, and so on.

When the A/D converter 18 completes the A/D conversion operation, it supplies a signal representing the end operation to the CPU 19 via a line 23. As a result, the operation shown in FIG. 4 is performed.

Moving from step r1 to step r2, the CPU 19
The digital value from the /D converter 18 is taken in. step r
3, the sampling value PM is as shown in Table 1.
= (i=1.2, 3. . . .)
The arithmetic operations shown in the table are performed to obtain the arithmetic mean value Mi.

In step r4 of Table 1, the currently sampled digital value from the A/D converter 18 is stored in the memory 21 as PMIz-n for use in the next arithmetic mean calculation.

Next, a second embodiment of the present invention will be described using FIGS. 5 and 6.

FIG. 5 is a time chart illustrating a second embodiment of the present invention. FIG. 5(1) shows the intake pipe pressure PM detected by the pressure sensor 13 similarly to FIG. 2(1). Similar to the first method, this pressure PM is sampled every 1/2 period of the pulsation period t, and the arithmetic average with the previous sampling value is taken, thereby obtaining a pressure value with rift pull removed.

FIG. 5(2) is a 30'CA signal, similar to FIG. 2(2). Therefore, pressure values (PMI, pMz, PMi, ...) are calculated every 60"CA based on the 30°CA signal.
By sampling , it is possible to sample every t/2.

FIG. 5(3) shows the engine rotation speed. As the engine speed increases in this manner, the pulsation period becomes shorter. However, as the pulsation period of the intake pipe pressure becomes shorter, the processing for starting sampling and calculating the arithmetic mean increases, so C
This places a burden on PU19.

Therefore, the engine speed is set to a predetermined value (for example, 3500
rpm) or more, the pressure value (PM,, PMh, PM?,
...) is sampled.

FIG. 6 is a flowchart showing the operation of the CPU 19 in the embodiment shown in FIG. The CPU 19 receives the output signal of the crank angle sensor in the distributor 9 from the line 17, moves from step Q1 to Q2, and calculates the crank angle 3.
CADS, a counter for counting 0°CA signals
The value of is subtracted by 1 and the process moves to step Q3. Step Q3
Then, it is determined whether the counter CADS is O or not, and if so, the process moves to step Q4. In step Q4, the current engine rotation speed is compared with a predetermined rotation speed, for example, 3500 rpm, and the current engine rotation speed is determined to be the predetermined value 3500 rpm.
If it is lower than m, the process moves to step Q5, and if it is higher, the process moves to step Q6. In step Q5, the counter CADS is set to 2.
In step Q6, 6 is assigned to the counter CADS, and the process moves to step Q7. In step Q7, the first
Sampling and A/D conversion start processing are performed in the same manner as in the embodiment described above, and processing for calculating engine rotational speed and the like based on the 30'' CA flaw signal is performed in the same manner as in step S9.

The operation of the A/D converter and the processing of converted values are the same as in the first method, so their description will be omitted.

Also, here, the engine speed is set to a second predetermined value (for example, 1
0. OOOrpm) or more, 5/2 of the pressure pulsation
It is also possible to perform sampling at twice the period.

In this way, normally 1/2 of the pulsation period of the intake pipe pressure
For example, in Fig. 5, the intake pipe pressure is sampled at twice the frequency, such as PM at time 1°, PM at t2, 2M3 at time t, etc., and the engine speed reaches a predetermined value. For example, in FIG. 2, PM6 at time t,
PM at time t7? The intake pipe pressure is sampled as follows.

Effects of the Invention As described above, according to the present invention, it is possible to accurately determine the intake pipe pressure over a wide range of internal combustion engine speeds from low to high speeds without being affected by the pulsation component due to the pumping action of the cylinder. In addition, since transient response to sudden changes in intake pipe pressure can be improved, appropriate fuel injection amount, ignition timing, etc. can be calculated, and engine performance can be improved.

Furthermore, the CPU for control due to the increase in A/D conversion processing and processing to calculate the arithmetic mean of converted values during high rotations.
Since the engine is stable at high rotation speeds and there is no problem even if the measured value of intake pipe pressure deviates slightly from the actual pressure, A/D conversion processing and conversion can be performed without affecting the condition of the engine. Since the calculation process of the arithmetic mean of values can be reduced, the load placed on the control CPU can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a time chart illustrating the first method of the present invention.
3 and 4 are flowcharts showing the operation of FIG. 1 according to the first method, FIG. 5 is a time chart explaining the second method, and FIG. 6 is a flowchart showing the operation of FIG. 1 according to the second method. 3 is a flowchart showing the operation of FIG. 1 cylinder, 3 throttle valve, 4: surge tank, 5
:Intake manifold, 9:Distributor, lO:
Spark plug, 11: Exhaust pipe, 13: Pressure sensor, 15;
Control device, 16: Input interface, 18: Analog/digital converter, 19: Central processing circuit, 2o: Output interface, 21: Memory

Claims (1)

[Claims] The air pressure in the intake pipe of an internal combustion engine is determined by the pulsation period t=h of the pressure.
/(m・n) (where h: constant, m: engine speed, n: number of cylinders) is sampled every 1/2, and the air pressure in the intake pipe is determined by the arithmetic average of at least the previous sampling value. The internal combustion detection method is characterized in that when the pressure pulsation period t is below a predetermined value, the sampling interval is set to (1/2+k)·t (k=1, 2,...). A method for detecting air pressure in an engine's intake pipe.