JPH0529779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides fuel injection amount, ignition timing,
The present invention relates to a signal processing device for an internal combustion engine that is used to electrically control the amount of secondary air, etc., and processes, for example, an intake pipe pressure signal, an intake air amount signal, and a throttle valve opening signal.

When performing electronic control of an internal combustion engine (in other words, an engine), for example, intake pipe pressure, intake air amount, etc. are detected as voltage values, and converted to digital data using an A/D converter. It calculates the fuel injection amount, ignition timing, secondary air amount, etc., and controls the injector, igniter, valve, etc. based on the results. The bit precision (resolution) required for digital data is determined by the resolution required for fuel injection amount, ignition timing, etc. For example, for intake pipe pressure data, it is usually 9~
It is 12 bit. Therefore, the conventional engine control computer uses an expensive A/D converter of 10 to 12 bits even if the CPU is capable of 8-bit processing.

On the other hand, intake pipe pressure data, intake air amount data, etc. are data that pulsate with the rotational combustion cycle of the internal combustion engine. It is necessary to remove data pulsations, calculate the average value per combustion cycle, and calculate the fuel injection amount, etc. based on it.

An object of the present invention is to use an A/D conversion means with a small number of bits to effectively remove pulsation, and to obtain data having resolution performance greater than the number of bits unique to this A/D conversion means. Our goal is to provide inexpensive, high-performance equipment.

Therefore, in the present invention, as shown in FIG. 9, there is provided a detection means for generating a signal indicating at least one operation amount of the internal combustion engine, and A/D conversion processing is performed at predetermined intervals based on the signal of the detection means. An A/D conversion means, a storage means for storing digital values A/D converted by the A/D conversion means, and a storage means that receives synchronization signals synchronized with the rotation of the internal combustion engine, and receives synchronization signals at predetermined angular intervals at which these synchronization signals are generated. an average value calculating means for calculating an average value of the digital values obtained during the period including values of a lower bit number than the bit number of the A/D conversion signal; and an average value calculation angle changing means for lengthening a predetermined angular interval for calculating the average value by the average value calculation means, the average value calculation means increasing the number of bits lower than the number of bits of the A/D converted signal. It is characterized in that the average value calculated including the above is outputted as one operation amount of the internal combustion engine.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in which the engine electronic control system according to the present invention is applied to a 4-cylinder, 4-stroke, spark ignition engine installed in a normal automobile or the like. Combustion air is taken in through an air cleaner 7, a throttle mechanism 6, a surge tank 5, and an intake pipe 4. An intake pipe pressure sensor 12 is provided in the surge tank section,
The intake pipe pressure (surge tank internal pressure) corresponding to the amount of intake air per revolution of the engine 1 is converted into an electric signal and taken out. As the intake pipe pressure sensor, a general diaphragm type sensor made of, for example, a semiconductor or metal is used.

Moreover, for the fuel injection valve 2 of the engine 1,
Fuel is supplied from a fuel system not shown in the figure, and fuel is injected from this injection valve. The ignition system 3, which includes an igniter, an ignition coil, a distributor, etc., supplies an ignition high-voltage signal to a spark plug (not shown) in synchronization with engine rotation, and also transmits a high-voltage signal generated on the primary side of the ignition coil to the computer 10. supply

Exhaust gas after combustion from the engine 1 is released into the atmosphere via an exhaust manifold 8, an exhaust pipe 9, a catalytic converter 11, etc., and this exhaust system includes a A fuel ratio sensor 16 is provided.

In addition, the throttle mechanism 6 is provided with a throttle opening sensor 13, the intake pipe 4 is provided with an intake temperature sensor 14, and the main body of the engine 1 is provided with a cooling water temperature sensor 15. Along with the signal from the intake pipe pressure sensor 12, detection signals from the throttle opening sensor 13, intake temperature sensor 14, cooling water temperature sensor 15, etc. are also supplied to the computer 10, as well as a primary high pressure signal from the ignition system 3. Ru. The computer 10 calculates the optimum fuel injection amount based on these detection signals and controls the opening/closing timing of the fuel injection valve 2.

Next, the computer 10 will be explained in detail with reference to FIG. The system bus 106 is composed of a data bus, an address bus, and control signals. The CPU 100 responsible for calculation and control is the system bus 10
Data is exchanged with each unit 101 to 105 through 6. The A/D converter 105 has a conversion speed
In this case, an 8-bit high-speed A/D converter (for example, successive approximation type) is built in, and each sensor 12
~16, and each voltage signal of battery voltage +B
Upon request from the CPU 100, it is converted into digital data and transferred to the CPU 100. The timer unit 103 has a free-run timer that counts up in one fixed period (for example, 8 μs), and stores the generation time of the primary high voltage signal from the ignition system 3, and also sends the time data to the CPU 100 upon request. transfer. Further, based on the injector (fuel injection valve) ON and OFF times instructed by the CPU 100, ON and OFF signals are output to the output driver 110.

The interrupt control unit 104 performs an interrupt control at regular intervals (for example, 1 ms) based on the signal from the timer unit 103.
Or, when an IG high voltage signal is generated, send an interrupt request signal.
Transfer to CPU100. The ROM 101 is a read-only storage unit that stores programs and optimum control data for each engine condition, and the RAM 102 is a temporary storage unit used during program operation. CPU100
The input signal from each sensor is sent to the timer unit 103 according to the program stored in the ROM 101.
and calculates the optimum injection amount according to the engine condition at that time by inputting it through the A/D converter 105,
The opening time of the injection valve 2 is controlled by instructing the timer section 103 to indicate the injector ON/OFF time.

In this embodiment, a four-cylinder simultaneous injection system is adopted, and the injection valves of each cylinder are connected in parallel. Also, the CPU 100, timer section 103, interrupt control section 104, A/D conversion section 105, ROM
In this embodiment, a one-chip microprocessor having all built-in components such as 101, RAM 102, and an input/output port section is used.

Next, the programs stored in the ROM 101 will be described in detail. The program can be divided into three levels: main routine, timer interrupt processing program, and rotation synchronous interrupt processing program. First, regarding the main routine, it is the program with the lowest execution priority, and if an interrupt from one of the other two occurs while this program is running,
Giving priority to its execution, the main routine is temporarily suspended and resumed after the interrupt program ends.

First, the processing in the main routine is shown in FIG.
When the power of the computer 100 is turned on, the program starts execution, proceeds to step 1001, and uses the RAM 100.
Initialization processing such as clearing 2 and setting input/output ports is executed. Next, the process proceeds to step 1002, where engine cooling water temperature data is taken in from the A/D converter 105, and a water temperature correction coefficient f _TH w is calculated from the engine cooling water temperature using a one-dimensional map. Similarly, in step 1003, the intake temperature correction coefficient f _THA is determined, in step 1004, the invalid injection time τ _B is determined according to the battery voltage, and in step 1005, the air-fuel ratio correction coefficient f _A/F is determined according to the output voltage of the air-fuel ratio sensor 16. calculate. When the processing in step 1006 is completed, the process returns to step 1002 and thereafter steps 1002 to 1006 are repeated.

Next, FIG. 4 shows a flowchart of the timer interrupt processing program. Every fixed period (for example, 1 ms) in response to a request from the interrupt control unit 104
CPU 100 executes a timer processing program. In step 1100, intake pipe data P _M (8 bits) is taken in through the A/D converter 105, and added to an addition buffer ΣP _M , which will be described later, in step 1101. Further, in step 1102, the addition number counter _CPM is incremented by one. Next, proceed to step 1103, compare P _M a certain period of time (for example, 50 ms) ago with P _M at the present time,
If there is a change of more than a certain value, it is determined that there is an acceleration/deceleration (transient) state, and the process proceeds to step 1104 to calculate the acceleration/deceleration correction coefficient _fACC , and then proceeds to step 1105. If the amount of change is less than a certain value, it is determined that the state is steady, and the process proceeds to step 1106.
Then, set f _ACC =1 and proceed to step 1105. Note that average P _M data _M , which will be described later, may be used instead of P _M in determining acceleration/deceleration. In step 1105, other processes such as determining the necessity of asynchronous injection and calculating the amount of asynchronous injection are executed, and the timer interrupt processing routine is ended.

5 and 6 show flowcharts of the rotation synchronization (IG) interrupt program. In response to the primary high voltage signal synchronized with the ignition signal from the ignition system 3, the interrupt control unit 104 outputs an interrupt request signal to the CPU 100. The rotation synchronization interrupt processing program is started from step 1201 in response to this interrupt request signal. As mentioned above, the generation time of the primary high voltage signal is stored in the timer unit 103, and the
1201, read the data t _IG (sec) and calculate the rotation speed.
Calculate N _E using equation (1).

N _E = {1/(t _IG − t _IGA )} × (180/360) × 60 …(1) t _IGA is the time when the previous primary high pressure signal occurred, that is, the time 180° CA ago at the engine crank angle. be.

Now, if the execution period of the timer interrupt, that is, the A/D conversion period of the intake pipe pressure P _M is 1 ms, then
The sampling number of P _M between 180° CA (=C _PM is N _E
is 50 times at 600 rpm and 5 times at 6000 rpm. In order to obtain an accurate average intake pipe pressure P _M with pulsation removed, a certain number of samplings (for example, 10 times) or more are required. Therefore, in this example, in step 1202 the engine speed is C ₁ (for example
3000rpm), and if it is less than that, calculate the average intake pipe pressure M of 180° CA, that is, for each ignition, and if it is more than that, calculate the average intake pipe pressure _M of 360° CA, that is, for each engine revolution. The constant _C1 depends on the sampling period, the number of cylinders (pulsation period), the resolution (number of bits) required for _M , etc. If the sampling period is slow and the pulsation period is fast,
Pm may be calculated every two or three revolutions.
If the engine speed is above C ₁ , step 1210
Proceed to and determine whether it is time for calculation.
Calculation timing (in this example, 2 ignitions, i.e. engine 1)
(once per rotation), the process advances to step 1203; otherwise, the interrupt process ends.

In step 1203, the average intake pipe pressure _M (2 byte data) is calculated from the addition value ΣP _M (2 byte data) of P _M and the number of additions C _PM calculated by the timer interrupt processing program shown in Fig. 4 using equation (2). calculate.

ΣP _M ×2 ⁿ /C _PM = _M …(2) Here, n is A/D converted intake pipe pressure data
Indicates the number of bits added (carry) to improve the resolution of P _M (8 bits). In addition, since the average intake pipe pressure _M is shown as a binary value, by adding n bits to the intake pipe pressure data P _M (8 bits), it is multiplied by 2n (carry up by n).
will be the value.

Now, if the number of sampling times is m, the effective number of bits of _M is (K+n) bits for the intake pipe pressure data P _M (Kbit) determined by the resolution of the A/D converter.
It is possible to (n≦log ₂ m; n is an integer) In this example, m≧10 for 8-bit _PM , so
P _M is 9 to 11 bits. The output voltage signals of each sensor 12 to 16 installed in the engine room include
Since ignition noise, alternator noise, flasher noise, etc. are superimposed, high-frequency noise components other than signal components are included. Therefore, when using a successive approximation type high-speed A/D converter like the one in this example, the averaging process can remove high frequency noise superimposed on the sensor signal and improve the resolution of the sensor signal. . This is shown in FIG.

Now, the center value of the input signal Vi _N of the A/D converter is between "a" and "a+1" in binary digital data after A/D conversion, and (a+1/2)<Vin<
Let it be (a+3/4). It is assumed that high frequency noise as shown in FIG. 7 is superimposed on the input signal Vin. 7th
Asynchronously to high frequency noise, as shown at the bottom of the figure,
When A/D conversion is performed at a fixed cycle timing (10 times), the converted data becomes "a+1" seven times and the converted data becomes "a" three times. If this is arithmetic averaged, {7(a+1)+3a}/10=a+7/10, which satisfies (a+1/2)<Vin<(a+3/4). This uses a k-bit A/D converter,
This means that (k+2) bits of A/D converter data have been obtained. In this way, 1LSB of A/D conversion data
It is impossible to obtain data with one A/D conversion for an input signal that fluctuates as described above. In the case of the intake pipe pressure signal _PM , in addition to high-frequency noise, pulsations synchronized with ignition due to intermittent combustion in the engine are superimposed.

Therefore, A/D converted intake pipe pressure data
Using P _M as it is to calculate the basic injection amount τ _P described later is important because if the A/D conversion timing is very small compared to the pulsation period as in this example, τ _P will vary widely and the engine will not stabilize. Sexuality worsens. In the case of an actual engine, the magnitude of the pulsation is, in the worst case,
(At low revolutions and full throttle) If the amplitude is 100mmHg or more, it will be 10% or more of the _PM signal.

In addition, as a countermeasure for the above phenomenon, in synchronization with the engine rotation, for example, in synchronization with the primary high pressure signal in this example,
A method of A/D conversion is also considered, but the pulsating waveform or phase superimposed on P _M depends on the engine speed,
It is difficult to adopt this method because engine conditions such as load and even the same engine conditions change complicatedly due to aging. In the case of automobile engines,
Rotation speed: 600rpm~6000prm, intake pipe pressure: 150~
750mmHg (up to 1200mmHg if equipped with a supercharger), requires a large dynamic range of injection amount, for example 1.5ms to 30ms, and satisfies drivability and exhaust gas purification performance through accurate fuel metering. In order to do this, the intake pipe pressure data used inside the CPU must be 9 bits or more. According to this embodiment, it is possible to obtain highly accurate intake pipe pressure data P _M from which pulsation and high frequency noise are removed using an inexpensive A/D converter with a small resolution.

In step 1204, for the next averaging process,
P _M addition buffer ΣPm, addition number counter CPM
is cleared to "0". Next step 1205
Then, it is determined whether or not to start injection, and if so, the process advances to step 1206; otherwise, the rotation synchronization interrupt routine is ended and the process returns to the main routine. This is because this example uses a four-cylinder simultaneous injection system and a one-time-per-rotation injection system.
This is because it is sufficient to inject once every two rotational synchronization interruptions that occur.

In case of injection, proceed to step 1206 and perform the second injection.
The injection start time is set in the timer unit 103, and then, in step 1207, a two-dimensional map consisting of the engine speed N _E obtained in step 1201 and the average intake pipe pressure _M obtained in step 1203 is calculated by interpolation. Find the basic injection time τ _P.

Next, in step 1208, steps 1002 to 1005 of the main routine in FIG. 3 and step 1104 in FIG.
The injection time τ is calculated from the correction coefficient obtained in step 1106 using equation (3).

τ=τ _P ×f _TH w×f _THA ×f _A/F ×f _ACC +τ _B …(3) Finally, in step 1209, the timer sets the injection end time to the time obtained by adding τ to the injection start time set in step 1206. section 103, and the rotation synchronization interrupt processing routine is ended.

In this embodiment, the intake pipe pressure P _M was sampled by timer interrupt processing, but if the sampling cycle is fast (for example, 1 ms or less), the processing time required for calculating the injection amount, etc. will be longer than the sampling cycle. In this case, one or more P _M sampling routines are included in the injection amount calculation routine,
May be inserted.

In addition, if the timer interrupt processing is a burden on other processing, the main routine
03 may be monitored and A/D conversion may be performed approximately every sampling period.
An example of this is shown in FIG.

In step 1301, the current time _tNOw is read from the free run timer of the timer section 103. Next, in step 1302, it is checked whether the sampling execution time _tA/D has passed, and if it has, the step
Proceed to 1303, otherwise end this subroutine. In step 1303, the A/D converter 105
Outputs an instruction to start A/D conversion of intake pipe pressure P _M to
After waiting for a certain period of time (about 100 μs) until completion, proceed to steps 1304 and 1305, and then proceed to the steps shown in Figure 4.
Addition processing similar to 1101 and 1102 is performed. Finally, in step 1306, the next sampling time is set as (t _A/D +
(sampling period) and update t _A/D .
End the subroutine. If there is a routine whose processing routine, such as injection amount calculation, exceeds the sampling period, insert this subroutine into that processing routine, and execute this subroutine at least once within (sampling period x 2) when the program is executed. You can arrange this subroutine so that

In this embodiment, the averaging process is performed on the intake pipe pressure _PM , but this is applicable to all engine parameters that have pulsations due to intermittent combustion in the engine, such as the amount of intake air.

Furthermore, although this embodiment discloses control of the fuel injection amount, this also applies to the ignition timing, EGR amount, and fuel injection amount.
Of course, it can be applied to anything that needs to be controlled by the intake pipe pressure P _M , such as the amount of secondary air.

In addition, when the averaging process is performed once every two or more revolutions, (acceleration/deceleration) is determined before step 1207 in FIG. 6, and the A/D conversion data P _{M is}
It is necessary to calculate the basic injection timing τ _P accordingly.

Furthermore, in this embodiment, the primary side high voltage signal of the ignition coil is used as the engine rotation synchronization signal.
This may be any signal that is synchronized with the engine rotation, such as a crank angle sensor in the distributor. When using a crank angle sensor, use a 30° CA crank angle sensor, synchronize with the angle (30° CA in this case), convert the intake pipe pressure from A/D to 180° CA or 360°. A similar effect can also be obtained by taking the average for each CA.

As described above, according to the present invention, a signal synchronized with the rotation of the engine is input using an A/D conversion means with a small number of bits, and in synchronization with this signal, a predetermined period sufficiently shorter than the period of this signal is input. average value calculation that averages the A/D converted digital data and lengthens a predetermined angular interval for average value calculation by the average value calculation means when the rotational speed of the internal combustion engine is equal to or higher than a predetermined value. Since it is equipped with an angle changing means, even at high rotation, the A/
An average value is calculated from the D-converted signal to obtain data that can satisfactorily remove pulsations from low to high rotations of the internal combustion engine and has resolution performance greater than the number of bits unique to this A/D conversion means. This makes it possible to provide an inexpensive and high-performance signal processing device.

[Brief explanation of the drawing]

1 to 7 show one embodiment of the present invention, FIG. 1 is a block diagram showing an outline of the device of the present invention, FIG. 2 is a detailed block diagram of the computer section, and FIGS. 3 to 6
7 are a flowchart and a signal waveform diagram for explaining the operation of the present invention, FIG. 8 is a flowchart for explaining another embodiment of the present invention, and FIG. 9 is a block diagram showing the overall configuration of the present invention. It is a diagram. 1... Internal combustion engine (engine), 2... Fuel injection valve, 3... Ignition system, 10... Computer, 12
...Intake pipe pressure sensor, 13...Throttle opening sensor, 100...CPU, 101...ROM, 10
2...RAM, 103...Timer section, 104...
...Interrupt control section, 105...A/D conversion section.

Claims (1)

[Claims] 1. A detection means that generates a signal indicating at least one operation amount of the internal combustion engine, A/D conversion means that obtains the signal of the detection means and performs A/D conversion processing at predetermined intervals, and this A/D conversion. storage means for storing digital values A/D converted by the means; receiving a synchronization signal synchronized with the rotation of the internal combustion engine; and storing an average value of the digital values obtained during a predetermined angular interval at which these synchronization signals are generated. , an average value calculation means for calculating including values of lower bit numbers than the bit number of the A/D conversion signal, and an average value calculation means for calculating the average value by the average value calculation means when the rotation speed of the internal combustion engine is equal to or higher than a predetermined value. average value calculation angle changing means for lengthening a predetermined angular interval;
A signal processing device for an internal combustion engine, characterized in that an average value calculated including values of bit numbers lower than the bit number of a D-converted signal is output as one operation amount of the internal combustion engine.