JPH07122417B2 - Method for detecting air pressure in intake pipe of internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring an air pressure in an intake pipe of an internal combustion engine.

2. Description of the Related Art As one parameter for determining the optimum fuel injection amount, ignition timing, etc. according to the state of the internal combustion engine, there is an intake pipe air pressure of the internal combustion engine (hereinafter referred to as intake pipe pressure).
By the way, since the intake pipe pressure constantly pulsates due to the pumping action of the internal combustion engine even if the throttle opening is constant, it is necessary to measure the intake pipe pressure so as not to be affected by the pulsation.

Conventionally, as a method of measuring the intake pipe pressure without being affected by pulsation, a pressure sensor that directly detects the pressure in the intake pipe and an analog / digital (hereinafter referred to as A / D)
By providing a filter to remove the pulsating component between the converter,
A method is known in which the signal that passes through the filter is used as the intake pipe pressure.In this method, if the time constant of the filter is increased to sufficiently remove the pulsating component when the engine speed is low, the throttle opening The change of the intake pipe pressure at the time of sudden change in the degree cannot be detected with good response, and conversely, if the time constant of the filter is made small in order to improve the response at the time of sudden change, the pulsating component in the low rotation range cannot be sufficiently removed.

Therefore, the applicant has previously filed a patent application for solving this problem.
Filed as -251642. The outline of the invention is that the intake pipe pressure is sampled at intervals of 1/2 times the pulsation period t
/ D conversion is performed, and the arithmetic mean of the previous sampling value and this sampling value is used as the average pressure value of the intake pipe.

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

The present invention is intended to solve such a problem.

Means for Solving Problems In order to solve the above problems, the present invention has the following configuration. That is, the air pressure in the intake pipe of the internal combustion engine is determined by the pulsation cycle t = h / (m · n) (where h:
Constant, m: engine speed, n: number of cylinders), and sampling the air pressure in the intake pipe by an arithmetic mean with at least the previous sampling value. When is less than a predetermined value, the sampling interval is set to (1/2 + k) · t (where k = 1, 2, ...).

Action According to the above method, when the pulsation cycle of the intake pipe pressure is long or when the engine speed is low, sampling is performed at half the cycle of the pressure pulsation, and the intake is performed by at least the arithmetic average of the previous sampling value. When the pipe pressure is obtained and the pulsation of the intake pipe pressure is fast or the engine speed is high, sampling is performed at a cycle of (1/2 + k) times (k = 1,2, ...) of the pressure pulsation, and at least The average value of the intake pipe pressure is obtained by the arithmetic mean with the previous sampling value.

Therefore, when the engine speed is low, the pressure pulsation cycle is long, so the sampling cycle is also long, and the ripple-removed pressure value can be obtained without burdening the control CPU. Further, since it is possible to measure the rapid change in pressure with little delay, it is possible to calculate an appropriate fuel injection amount, ignition timing, and the like. On the other hand, even when the engine speed is high, the sampling cycle becomes long, and the time for performing the A / D conversion process and the process of calculating the arithmetic mean of the converted values decreases,
Ripple can be removed without burdening the CPU.
At that time, since the engine is stable, there is no problem even if the measured value of the intake pipe pressure is slightly behind the actual pressure.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In a cylinder 1 of a 4-cycle 6-cylinder spark ignition internal combustion engine, combustion air from an air cleaner (not shown) passes through a pipe line 2 and further from a throttle valve 3 to a surge tank 4 for absorbing surge, and to each cylinder. It is supplied through the branched intake manifold 5. The cylinder 1 is provided with an intake valve 6. Fuel is injected from the fuel injection valve 7. The power from the ignition coil 8 is supplied to the distributor 9
Is supplied to the spark plug 10 via. Combustion exhaust gas from the cylinder 1 is exhausted from an exhaust gas purifying device 12 via an exhaust valve (not shown) through an exhaust pipe 11. The surge tank 12 is provided with a pressure sensor 13, and detects the intake pipe pressure common to each cylinder. The output from the pressure sensor 13 is provided via line 14 to the input interface 16 of the controller 15. In the controller 15, the analog signal from the input interface 16 is converted into a digital value by the A / D converter 18, and the CPU
Give to 19. The CPU 19 controls the fuel injection valve 7 via the output interface 20 and the ignition coil 8
To control. A memory 21 is provided in association with the CPU 19.

The 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 sampled every 1/2 cycle of the pulsation period t (PM ₁ , PM ₂ , PM ₃ , ...) And the arithmetic value with the previous sampling value is taken to obtain the pressure value from which the ripple has been removed. Can be asked.

The cycle t corresponds to a crank angle of 720 ° CA / n, where n is the number of cylinders. In this embodiment, since there are 6 cylinders (n =
6) The pulsation cycle 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 on the line 17. Based on the output of the crank angle sensor
A pulse is derived every 30 ° CA. Therefore, if the pressure value (PM ₁ , PM ₂ , PM ₃ , ...) is sampled every 60 ° CA when the 30 ° CA signal is received twice based on the output of the crank angle sensor, sampling can be performed every t / 2. become.

However, if the pulsation cycle of the intake pipe pressure becomes shorter as the engine speed increases, the processing for starting sampling, the processing for calculating the arithmetic mean, and the like increase, so that the CPU 19 is burdened.

Therefore, if the time from the previous sampling to the current sampling has not passed the predetermined time (for example, 3 ms), the 30 ° CA signal is received 6 times (3/2) · t corresponding to 180 Pressure value for each ° CA (PM ₅ , PM ₆ , PM ₇ , ...)
To sample.

FIG. 3 is a flow chart showing the operation of the CPU 19 in this first embodiment. The CPU 19 receives the output signal of the crank angle sensor in the distributor 9 from the line 17, moves from step S1 to step S2, and the crank angle is 30 °.
The CADS value, which is a counter for counting CA signals, is decremented by 1, and the process proceeds to step S2. Counter CADS in step S3
Is 0, and if so, the process proceeds to step S4. In step S4, it is determined whether the difference between the ZADS, which is the time at which the previous sampling was performed, and the current time is a predetermined value, for example, 3 ms or more, and if so, the process proceeds to step S5. In step S5, 2 is substituted into the counter CADS and the process proceeds to step S6. In step S6, the CPU 19 converts the detection output from the pressure sensor 13 into a digital value via the line 22 and the A / D
A signal to start the A / D conversion operation is given to the converter 18, and the process proceeds to step S7. As a result, the A / D converter 18 samples the detection output of the pressure sensor and starts the operation of performing A / D conversion. In step S7, ZADS is updated by substituting the current time into ZADS, and the process proceeds to step S9. Step S9
Then, the process of calculating the engine speed etc. is performed based on the 30 ° CA signal.

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

Thus normally the pulse period half the period of the intake pipe pressure in the PM ₁ at time t ₁ in FIG. 2 eg, P at time t ₂
When the intake pipe pressure is sampled as M ₂ and so on, and the pulsation period is less than the specified time, the interval of (1/2 + k) ・ t (where k = 1, 2, ...) the PM ₆ in at time t ₆ in FIG. 2 for example, the time t ₇
Sampling of the intake pipe pressure is performed with PM ₇ and so on.

When the A / D converter 18 finishes the A / D conversion operation, it gives a signal indicating the termination operation to the CPU 19 from the line 23. As a result, the operation shown in FIG. 4 is performed. The process moves from step r ₁ to step r ₂ and the CPU 19 takes in the digital value from the A / D converter 18. In step r ₃ , as shown in Table 1, the arithmetic operation shown in Table 1 is performed based on the sampling value PM _i (i = 1,2,3, ...), and the arithmetic mean Mi is calculated. Ask.

In step r ₄ , the digital value sampled this time from the A / D converter 18 is stored in the memory 21 as PM _(i−1) for use in the arithmetic operation of the next arithmetic operation.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a time chart explaining the second embodiment of the present invention. FIG. 5 (1) shows the intake pipe pressure PM detected by the pressure sensor 13 as in FIG. 2 (1). Similar to the first method, this pressure PM is sampled every 1/2 cycle of the pulsation cycle t, and the arithmetic mean with the previous sampling value is taken to obtain the pressure value from which the ripple has been removed. Similar to FIG. 2 (2), FIG. 5 (2) shows a 30 ° CA signal. Therefore, if the pressure values (PM ₁ , PM ₂ , PM ₃ , ...) Are sampled every 60 ° CA based on the 30 ° CA signal, sampling can be performed every t / 2.

FIG. 5 (3) shows the engine speed. As the engine speed increases, the pulsation cycle becomes shorter. However, when the pulsation cycle of the intake pipe pressure is shortened, the processing to start sampling and the arithmetic mean calculation processing increase, so CP
U19 is burdened.

Therefore, the engine speed is set to a predetermined value (for example, 3500rp
If m or more, the pressure values (PM ₅ , PM ₆ , PM ₇ , ...) Are sampled at every 180 ° CA corresponding to (3/2) · t.

FIG. 6 is a flow chart showing the operation of the CPU 19 in the embodiment of 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, subtracts 1 from the value of CADS, which is a counter for counting the crank angle 30 ° C A signal, and proceeds to step Q3. Move on to. In step Q3, it is determined whether the counter CADS is 0, and if so, the process proceeds to step Q4. At step Q4, the current engine speed and a predetermined engine speed, for example 35
Compared with 00 rpm, the current engine speed is a predetermined value 3500r
If it is lower than pm, go to step Q5, if it is higher than step Q6
Move to. In step Q5, substitute 2 for the counter CADS,
In step Q6, 6 is substituted into the counter CADS, and the process proceeds to step Q7 together. In step Q7, the sampling and A / D conversion start processing is performed as in the first embodiment, and the processing for calculating the engine speed and the like based on the 30 ° CA signal is performed as in step S9. Since the operation of the A / D converter and the processing of the converted value are the same as those in the first method, description thereof will be omitted.

Further, here, the engine speed is the second predetermined value (for example, 1
It is also possible to perform sampling at a cycle of 5/2 times the pressure pulsation as long as it is at least 0,000 rpm.

In this way, normally, PM ₁ is set to the time t ₂ at the time t ₁ in FIG. 5 at a cycle half the pulsation cycle of the intake pipe pressure.
The intake pipe pressure is sampled as follows: PM ₂ at time t ₃ , PM ₃ at time t ₃ , and so on, and (1/2 + k) ・ t (where k = 1 , 2, ...), for example, PM ₆ at time t ₆ in FIG.
Sampling of the intake pipe pressure is performed by setting PM ₇ at ₇ , and so on.

EFFECTS OF THE INVENTION As described above, according to the present invention, the intake pipe pressure can be accurately obtained over a wide range from low rotation to high rotation of the internal combustion engine without being affected by the pulsating component due to the pumping action of the cylinder. In addition, since the transient response to a sudden change in the intake pipe pressure can be improved, an appropriate fuel injection amount, ignition timing, etc. can be calculated, and engine performance can be improved.

Furthermore, the load on the control CPU due to the increase in A / D conversion processing at high rotation speed and processing to calculate the arithmetic mean of the converted values, etc., the engine at high rotation speed is stable and the measured value of the intake pipe pressure is high. Since there is no problem even if is slightly deviated from the actual pressure, it is possible to reduce the A / D conversion process and the calculation process of the arithmetic mean of the converted values without affecting the engine condition.
The load on the control CPU can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart explaining 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 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, 10: Spark plug, 11: Exhaust pipe, 13: Pressure sensor, 15: Control device, 16: Input interface, 18: Analog / Digital converter, 19:
Central processing circuit, 20: Output interface, 21: Memory

Claims (1)

[Claims] 1. The air pressure in the intake pipe of an internal combustion engine is ½ of the pulsation cycle t = h / (mn) (where h: constant, m: engine speed, n: number of cylinders). In the method of detecting the air pressure in the intake pipe by at least the arithmetic mean of the previous sampling value and the pulsation cycle t of the pressure is equal to or less than a predetermined value, the sampling interval is (1/2 + k) .t. (However, k = 1, 2, ...) The method for detecting the air pressure in the intake pipe of an internal combustion engine, wherein: