JPS63159641A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent fuel quantity from being too much or little when the basic time of fuel injection is corrected according to the atmosphere, by varying an air-fuel ratio correction amount when the air-fuel ratio correction caused by the present atmospheric pressure is deduced to be carried out. CONSTITUTION:Fuel having the pressure adjusted by a pressure regulator for adjusting the fuel pressure with back pressure of the atmospheric pressure is discharged from a fuel injection means C1. The basic time for fuel injection is determined by a determining means C2 on the basis of intake pressure and rotational frequency of an engine. Then, the basic time is subjected to air-fuel ratio correction by a correction means C3 on the basis of a difference between actual exhaust composition value and a predetermined value. Also, when the intake pressure has a value considered to be that of atmospheric pressure, the basic time is subjected to the atmospheric correction by a correction means C4 on the basis of said value. In the atmospheric correction when the air fuel ratio correction cause by the present atmospheric pressure is deduced to be carried out by a deducing means C5, the air fuel correction amount is varied by an adjusting means C6.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a fuel injection control device for an internal combustion engine using a pressure regulator that regulates the pressure of fuel using atmospheric pressure as a back pressure.

[Prior Art] Conventionally, a fuel injection control device for an internal combustion engine discharges fuel whose pressure is regulated by a pressure regulator for a period of time according to the operating state of the internal combustion engine by controlling the opening of a fuel injection valve, and injects the fuel into the internal combustion engine. The amount of fuel used is adjusted. Therefore,
It is desirable to maintain a correlation between the time during which fuel injection is performed and the amount of fuel injected at that time, and for this reason, the pressure inside the intake pipe of the internal combustion engine where fuel injection is performed is used for the back pressure of the pressure regulator. ing.

On the other hand, when the fuel system is in a high temperature state, such as when restarting an internal combustion engine at a high temperature, paper may be generated in the fuel piping, and this paper may prevent fuel from being discharged from the fuel injection valve, making it impossible to start. , problems such as rough idle were occurring. In order to suppress the generation of paper, it is possible to increase the set pressure of the pressure regulator, but this would require improving the quality of all parts such as the pressure resistance of the fuel system and the compression capacity of the fuel pump, which would increase the size of the device. , with increased weight and cost.

Therefore, a method has been proposed to easily suppress the generation of paper by releasing the back pressure of the pressure regulator to the atmosphere. The back pressure of the pressure regulator is released to the atmosphere only at certain times, and in other operating conditions, the pressure inside the intake pipe is used again as the back pressure of the pressure regulator in order to maintain the correlation between the fuel injection time and the amount of fuel supplied as described above. ing.

[Problems to be Solved by the Invention] However, even the fuel injection control device of the type that switches the back pressure of the pressure regulator as described above is not sufficient and has the following problems.

In order to switch the atmospheric pressure, in addition to an expensive pressure switching valve, a large number of new parts such as a power transistor to operate the valve and a control circuit are required, which increases the cost. In addition, the increase in the number of new parts increases the possibility of failure, resulting in poor reliability.Furthermore, it is difficult to set the timing for switching the back pressure of the pressure regulator from atmospheric pressure to intake pipe pressure, which may occur too early. If the switching is carried out at the same time, the same effect as before will be noticeable, and if the switching is delayed, excessively rich fuel will be supplied to the internal combustion engine, resulting in a deterioration of the air-fuel ratio.

The present invention has been made to solve all of the above-mentioned problems, and it eliminates the need for parts involved in pressure switching by constantly opening the back pressure of the pressure regulator to the atmosphere.
An excellent fuel injection control system for internal combustion engines that is low in cost, highly reliable, and can control the air-fuel ratio of the internal combustion engine well. + The purpose is to provide equipment.

Furthermore, a patent application filed in 1980-
According to the technology disclosed in No. 49553, a means is specified to open the back pressure of the pressure regulator to the atmosphere and maintain a good relationship between the fuel injection time and the amount of fuel discharged at that time due to fluctuations in atmospheric pressure. ing. However, the above proposed fuel injection control device requires a separate atmospheric pressure sensor to be installed in the conventional L-J type fuel injection control device or D-J type fuel injection control device, which increases the size and cost of the device. There was an inherent problem that led to

Structure of the Invention [Means for Solving the Problems] The means constructed in the fuel injection control device for an internal combustion engine of the present invention, which was made to solve the above problems, are illustrated in the basic configuration diagram of FIG. 1. As shown in FIG. A basic fuel injection time determining means C2 that determines based on internal pressure and rotational speed; and an air-fuel ratio correcting means C3 that corrects the air-fuel ratio of the basic time based on the difference between the exhaust composition of the internal combustion engine EG and a predetermined exhaust composition. When the pressure inside the intake passage of the internal combustion engine EG reaches a value that is considered to be atmospheric pressure, the atmospheric pressure correction means C4 performs atmospheric correction for the basic time based on that value, and the air-fuel ratio correction means C3 is currently Estimating means C for estimating whether air-fuel ratio correction is being performed based on a deviation in exhaust composition caused by atmospheric pressure.
5, when the atmospheric pressure correction means C4 executes the atmospheric correction and the estimating means C5 estimates that the air-fuel ratio correction is due to the current atmospheric pressure, the amount of the air-fuel ratio correction is changed; It is characterized by comprising: an air-fuel ratio correction amount adjusting means C6;

[Operation] The fuel injection means C1 in the present invention pressurizes fuel using atmospheric pressure as back pressure, and injects and supplies the pressurized fuel to the intake passage of the internal combustion engine EG. That is,
The fuel is pressurized to a predetermined value higher than the atmospheric pressure using the atmospheric pressure as a reference pressure, and the pressurized fuel is discharged toward the intake passage of the internal combustion engine, and the back pressure of a known pressure regulator is released to the atmosphere. It consists of an injection device, etc. The basic fuel injection time determining means C2 determines the operating time of the fuel injection means C1, that is, the basic time, based on the intake passage pressure and rotational speed of the internal combustion engine EG. This is the same function that determines the basic fuel injection time of the so-called D-8 type fuel injection control device, which calculates the required fuel amount of the internal combustion engine EG from the intake passage pressure and rotation speed, and injects fuel for a corresponding period of time. Activate the means C1.

The air-fuel ratio correction means C3 performs air-fuel ratio correction to expand or contract the basic time based on the difference between the exhaust gas composition of the internal combustion engine EG and a predetermined exhaust gas composition. This has the same effect as the air-fuel ratio feedback control that corrects the expansion and contraction of the fuel injection time based on the output of the oxygen sensor provided in the exhaust system of the known internal combustion engine EG. The exhaust gas composition of the internal combustion engine EG is determined by the ratio between the amount of air taken into the internal combustion engine EG and the amount of fuel injected and supplied. Therefore, by feedback controlling the fuel amount while monitoring the exhaust gas composition, the operating state of the internal combustion engine EG can be accurately maintained at a desired state.

Further, the atmospheric pressure correction means C4 has the effect of expanding and contracting the basic time like the air-fuel ratio correction means C3, but its reference is the fluctuation of atmospheric pressure, and the pressure inside the intake passage of the internal combustion engine EG is regarded as the atmospheric pressure. Activates when the value is reached. The fuel injection time determining means C2 requires the intake passage pressure of the internal combustion engine EG as one parameter for determining the basic time, but when this value is considered to be equal to the atmospheric pressure, the atmospheric pressure correcting means C4 will also be used. As mentioned above, since the fuel injection means C1 pressurizes the fuel using atmospheric pressure as back pressure, fluctuations in atmospheric pressure directly affect the fuel pressure, and if atmospheric pressure changes, the amount of fuel discharged within the same fuel injection time will change. will also change.

Atmospheric correction is a method that expands or contracts the basic time in order to correct this change.

The estimating means C5 means that when the internal combustion engine EG is operating under a certain atmospheric pressure environment, the air-fuel ratio correcting means C3 corrects the air-fuel ratio in order to correct a deviation in the exhaust gas composition caused by the atmospheric pressure. Estimate whether or not the In other words, as mentioned above, fluctuations in atmospheric pressure affect the amount of fuel injected and supplied, so fluctuations in atmospheric pressure also affect the internal combustion engine E.
The exhaust gas composition of G will deviate from the desired exhaust gas composition.

If the atmospheric pressure correction means C4 is guaranteed to operate at all times, the deviation in the exhaust gas composition will be eliminated by the atmospheric correction. However, under operating conditions in which the pressure inside the intake passage of the internal combustion engine EG is rarely regarded as atmospheric pressure, there are few opportunities for atmospheric correction to be performed, and air-fuel ratio correction means can even correct deviations in the air-fuel ratio based on fluctuations in atmospheric pressure. It is likely to be done by C3. Therefore, the estimation means C5 estimates whether the air-fuel ratio correction means C3 actually corrects even the deviation in the exhaust composition caused by atmospheric pressure. For example, if air-fuel ratio correction has been performed for a sufficient period of time without running uphill or downhill for long periods of time where atmospheric pressure changes, the difference in exhaust composition due to the current atmospheric pressure may It can be assumed that the correction was made through air-fuel ratio correction.

The air-fuel ratio correction amount adjusting means C6 operates when the following two conditions are satisfied, and changes the amount of air-fuel ratio correction. The two conditions are, first, that the atmospheric pressure correction means C4 is performing atmospheric correction, and second, that the estimating means C5 is performing air-fuel ratio correction due to the current atmospheric pressure. . That is, changes in the injected fuel base due to changes in atmospheric pressure should originally be corrected by the atmospheric pressure correction means C4, but as described above, opportunities for such correction are limited. In such a case, if the air-fuel ratio correcting means C3 operates for a sufficient period of time, a deviation in the air-fuel ratio due to fluctuations in atmospheric pressure will be detected, and an air-fuel ratio correction will be performed that takes even the atmospheric pressure correction valve into consideration. Therefore, if atmospheric correction is performed by the atmospheric pressure correction means C4 without taking any measures in the above state, the basic time correction based on the change in atmospheric pressure will be performed redundantly, and the amount of fuel will be excessive or It becomes too small.

Under such conditions, the main air-fuel ratio correction amount adjusting means C6 operates and changes the amount of air-fuel ratio correction that has not even been added to the atmospheric positive correction amount to avoid the above-mentioned excessive or insufficient fuel amount. be.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, the present invention will be described in detail by giving examples.

[Embodiment] First, FIG. 2 is a block diagram of an internal combustion engine system equipped with a fuel injection control device according to an embodiment.

1 is the internal combustion engine body, 2 is the piston, 3 is the spark plug, 4
is an exhaust manifold, 5 is an oxygen sensor provided in the exhaust manifold 4 and detects the residual oxygen concentration in the exhaust gas, 6 is a fuel injection valve that injects fuel into the intake air of the internal combustion engine body 1, 7 is an intake manifold, and 8 is an oxygen sensor An intake air temperature sensor detects the temperature of intake air sent to the internal combustion engine main body 1, a water temperature sensor 9 detects the temperature of the internal combustion engine cooling water, 10 a throttle valve, and 11 a built-in idle switch for controlling the idle state and throttle valve. Reference numeral 14 represents a throttle sensor that detects the opening degree, a surge tank that absorbs pulsation of intake air, and 15 an intake pressure sensor that detects the pressure within the surge tank 14.

16 is an igniter that outputs the high voltage necessary for ignition; 17 is a distributor that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder; and 18 is a distributor 17 A rotation angle sensor 19 is installed inside the sensor and serves as a rotational speed sensor that outputs 24 pulse signals for one revolution of the distributor 17, that is, two revolutions of the crankshaft. A cylinder discrimination sensor outputs an output, and 20 represents an electronic control circuit as a control means.

Fuel pumped up from a fuel tank 22 by a fuel pump 21 is supplied to the fuel injection valve 6 via a pressure regulator 23.

The pressure regulator 23 is for constantly supplying fuel at a predetermined pressure to the fuel injection valve 6, and
3a communicates with an internal back pressure chamber, and when the fuel pressurized by the fuel pump 21 reaches a predetermined set pressure of 1 s above atmospheric pressure, the return boat 23b pumps the fuel until the fuel pressure reaches the set pressure. The fuel is returned to the fuel tank 22, and the fuel is always supplied to the fuel injection valve 6 at a pressure higher than atmospheric pressure by a predetermined set pressure.

Also, to explain the internal configuration of the electronic control circuit 20, in the figure, 30 is a central processing unit that inputs and calculates data output from each sensor according to a control program, and performs processing for controlling the operation of various devices. (CPU), 31 is a read-only memory (ROM) in which control programs and initial data are stored;
32 is a random access memory (RAM) in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read and written; 33 is a random access memory (RAM) in which the real time for control can be read at any time by the CPU 30; C.P.
Two registers (
36 is an input port for inputting signals from each sensor; 38 is an output port for driving the igniter 16 and the fuel injection valve 6 provided in each cylinder; 39 is an output port for driving the igniter 16 and the fuel injection valve 6 provided in each cylinder This is a common bus that interconnects each of the above elements. Input port 36 is connected to oxygen sensor 5. Intake temperature sensor 8. Water temperature sensor 9, throttle sensor 11. The analog signal from the intake pressure sensor 15 is A
An analog input section (not shown) that receives /D conversion and input, an idle switch (not shown) in the throttle sensor 11,
It consists of a rotation angle sensor 18 and a pulse input section (not shown) into which pulse signals from a cylinder discrimination sensor 19 are input.

When the output port 38 receives a command to start fuel injection from the CPU 30, it outputs a control signal to open the fuel injection valve 6.
This control signal continues to be output until the output port 38 receives a signal from the CPU 30 instructing the end of fuel injection. The command to end fuel injection is issued by a match interrupt routine to the conveyor that occurs when the fuel injection end time t1 set by the CPU 30 on the conveyor A inside the timer 33 matches the real time that the timer 33 continues to count. (described later).

Similarly, the on/off signal to the igniter 16 is performed by a signal from the output port 38 instructing the igniter to turn on or off, but this is the start of the ignition timing set by the CPU 30 on the conveyor B inside the timer 33. and end time t2 or t3 and timer 33
This is given by a conveyor B match interrupt routine (described later) which occurs when the continuous counting of the conveyor B matches the real time.

Note that the detection output TA of the throttle sensor 11 of this embodiment
The relationship between the pressure in the intake passage and the pressure in the intake passage at that time (ratio to the pressure in the intake passage when fully open) is as shown in FIG. As shown in the figure, during the opening operation when the throttle opening TA is 60 [deQ] or more, the pressure inside the intake passage is approximately equal to the pressure inside the intake passage when the throttle opening TA is fully open at its maximum, that is, the atmospheric pressure. becomes. Further, as the rotational speed of the internal combustion engine 1 increases, the intake flow rate increases, and therefore the pressure in the intake passage decreases at the same throttle opening TA. Therefore, it can be seen that the conditions under which the output of the intake pressure sensor 15 is considered to be atmospheric pressure are determined from the mutual relationship between the throttle opening TA and the rotational speed. In this embodiment, as will be described later, the output of the intake pressure sensor 15 when the throttle opening TA is 60 deq1 or more and the rotation speed is 4000 rom or less is assumed to be equal to atmospheric pressure and used for fuel injection control. are doing.

Next, the control executed by the electronic control device 20 of this embodiment will be described in detail.

The flowchart shown in FIG. 4 is the main control routine. This routine is started when a key switch (not shown) is turned on, and first performs initialization such as clearing the internal registers of the CPLJ 30 (step 100), and then sets initial values of data used to control the internal combustion engine 1. , for example, reads out the learned value MKt of air-fuel ratio feedback from a predetermined storage area (step 110). Next, the operating state of the internal combustion engine 1, for example, the intake pressure sensor 15,
Rotation angle sensor 18. The signals from the water temperature sensor 9, etc. are read, and from the various data read in this way, the intake pipe pressure pm and rotational speed N of the internal combustion engine 1, and these intake pipe pressures P are calculated.
Processing is performed to calculate various quantities that are the basis of control of the internal combustion engine 1, such as the basic fuel injection time TB, which is calculated as a function of m and the rotational speed N (step 120). Below, step 12
Based on the various quantities determined in step 0, well-known ignition timing control (step 130) is performed, and then the process moves on to correcting the amount of fuel to be injected and supplied in accordance with the operating state of the internal combustion engine 1. Here, first, an air-fuel ratio correction control suitable for the operating state of the internal combustion engine 1 is selected (step 140), and then atmospheric pressure correction IKI) is calculated (described later) in step 150, and finally the following step The fuel injection time TAU calculation process of 160 is executed, and the injection time for actually supplying fuel to the internal combustion engine 1 is determined according to the following formula,
After this process, the process returns to step 120 and the above process is repeated.

TAU=TBxKt x (1+Kh)xKpHowever,
Kh is an increase coefficient at low temperatures or high loads (Kh=O is set during air-fuel ratio feedback) Next, in the processing of the above main routine, air-fuel ratio correction in step 140, which is a feature of this embodiment, is performed. The control and the atmospheric pressure correction control in step 150 will be explained.

First, the details of the air-fuel ratio control process will be explained based on the flowcharts of FIG. 5 and FIG. 6. FIG. 5 is a flowchart showing an interrupt process that is executed by interrupting the main routine process at predetermined time intervals in connection with the air-fuel ratio control process, and FIG. 2 is a flowchart showing details of the process.

The interrupt processing in FIG.
Every [m5ec], the above-mentioned main routine processing is interrupted and executed. First, it is determined whether the output of the oxygen sensor 5 is at a high level, that is, whether the air-fuel ratio is in a rich state (
Step 200>. If this condition is met, the process proceeds to step 202. Here, the lean flag FL indicating the lean state is reset (step 202). Next, it is determined whether the lean flag FR, which is set when control for shifting the air-fuel ratio to a lean state is being performed, has been reset (step 204).

If this condition is met, that is, if control for shifting the air-fuel ratio to a lean state is not being executed, the process proceeds to step 206, where the value of the noise prevention delay timer counter Cd is counted up. On the other hand, step 204
If the condition does not apply, that is, if control to shift the air-fuel ratio to a lean state is being executed, the process advances to step 212, and the delay timer counter C for noise prevention is executed.
Clear d's 1st shift.

On the other hand, if the condition at step 200 is not met, that is, if the lean state is present, the process proceeds to step 208, where the lean flag FL is set. Next, it is determined whether the lean flag FR has been reset (step 210).

If this condition is met, that is, if control for shifting the air-fuel ratio to a lean state is not being executed, the process proceeds to step 212, where the first shift of the noise prevention delay timer counter Cd is cleared. On the other hand, if the conditions in step 210 are not met, that is, if control to shift the air-fuel ratio to a lean state is being executed, step 210
6, the delay timer counter Cd counts up one shift. These processes are aimed at preventing noise in the output signal of the oxygen concentration sensor 5, and in particular, when the output signal of the oxygen concentration sensor 5 changes between a lean state and a rich state, only a large change occurs. This is done to remove small changes as noise. Therefore, in the air-fuel ratio feedback control process to be described later, even if the air-fuel ratio detected by the oxygen sensor 5 changes from a lean state to a rich state or vice versa,
Do not reduce or increase the amount of fuel supplied immediately.
The control of the fuel supply amount is started only when the value of the delay timer counter cd exceeds a predetermined value. In addition, as mentioned above, water interrupt processing takes 4 [m5
The above step 2 is executed repeatedly by interrupting the main routine processing every time eC].
06 or step 212 delay timer counter C
Following the operation of d, it is determined whether the counter C1 for counting 1 [sec] has already counted r250J (step 214).CI<250
If 'l [sec] has not yet been counted, the contents of the counter C1 are incremented (step 216), and this routine ends.

On the other hand, when C1≧250 and i [SeO3 is being counted, the counter C1 should be set to "1" in preparation for the next time measurement (Step 218), 1 [5
Set flag F1 indicating eC1 progress (step 2
20) End this routine.

Next, the details of the air-fuel ratio control process (step 140) will be explained based on FIG. , or whether the output of the water temperature sensor 9 is 50['C] or more (step 300).
, and whether the intake pipe pressure Pm is below 80 [KPa] is determined in step 302). Air-fuel ratio feedback control is executed only when these two conditions are satisfied, and air-fuel ratio open control is executed at other times. First, when it is determined in step 300 that the water temperature is less than 50 ['C], after returning the variable A to "0" (step 304), the water temperature at that time is used as a parameter to set the pre-prepared cooler. Using the time map, the increase value during cold operation is determined by searching, interpolation, etc., and is set in the variable A (step 306).
), and then it is determined whether or not the load is high (step 308), and if the load is high, a high load correction value commensurate with the load is added to the variable A, and the process continues with step 310). At step 312, the final value of variable A is set to the aforementioned increase coefficient Kh. When it is determined in step 302 that the time is not cold but the time is high load, it is set to zero as described above (step 31
4) The high load correction value is added to variable A (step 310
), the value is set to the increase coefficient Kh in step 312. After these determination processes of the increase coefficient Kh, the value of the learning value MKt obtained during the air-fuel ratio feedback process, which will be described later, is set to the air-fuel ratio correction coefficient Kt (step 316), indicating that the air-fuel ratio feedback process is being performed. Step 318)
, sets a flag FOR indicating that the open process is in progress (step 320), and ends the process of step 140.

On the other hand, when the two conditions of step 300 and step 302 are satisfied, zero is substituted for the increase coefficient Kh (step 3
22), and also sets a flag FFB indicating that feedback processing is in progress (step 324). Thereafter, the state of the lean flag FL is checked to determine whether the air-fuel ratio is in a lean state (step 326).

If this condition is met, that is, if the air-fuel ratio detected by the oxygen sensor 5 is in a lean state, step 3
Proceed to step 28. Here, it is determined whether the lean flag FR has been reset.

If this condition is met, that is, if the process of shifting the air-fuel ratio to a lean state is not being performed, the process proceeds to step 330. Here, the air-fuel ratio feedback correction coefficient is increased by 1 by b, and the process ends. On the other hand, if the condition of step 328 is not met, that is, if the process of shifting the air-fuel ratio to a lean state is being performed, the process proceeds to step 332. Here, it is determined whether the value of the delay timer counter cd mentioned above is 2 or more. If this condition is met, that is, the process of shifting the air-fuel ratio to a lean state is being performed, and the lean state has been detected continuously for 8 [m5ec1 or more since the oxygen sensor 5 detected the lean state. If so, the process proceeds to step 334 and the lean flag FR is reset. Then, the process proceeds to step 336, where the air-fuel ratio feedback correction coefficient Kt@BB is increased, and then, through the process of step 338, the learned value MKt is calculated from the following equation, and this process ends.

MKt=99XMKi + (KU B/2>Here B
and above are constants, and B is chosen to be significantly larger than b. B is a constant for performing a process of greatly increasing the air-fuel ratio feedback correction coefficient Kt, that is, a skip process when it is determined that the air-fuel ratio has shifted from a rich state to a lean state with respect to its target value.

Further, b is a constant for a process of gradually increasing the air-fuel ratio feedback correction coefficient Kt. On the other hand, step 33
If condition 2 is not met, the process proceeds to step 340, and the process of gradually bringing the air-fuel ratio to a lean state is continued.

Further, if the condition of step 326 is not met, that is, if the air-fuel ratio detected by the oxygen sensor 5 is in a rich state, the process proceeds to step 342.

Here, it is determined whether the lean flag FR is set. If this condition is met, that is, if the process of shifting the air-fuel ratio to a lean state is being performed, the process advances to step 340. Here, the air-fuel ratio feedback correction coefficient Kt is decreased by a and the process ends. On the other hand, if the conditions of step 342 are not met, that is, if the process of shifting the air-fuel ratio to a lean state is not being performed, the process proceeds to step 344. Here, the value of the delay timer counter cd mentioned above is 20.
It is determined whether or not this is the case. If this condition is met, that is, the process to shift the air-fuel ratio to a lean state is not performed, and the rich state is detected for more than 80 [m5eC] after the oxygen sensor 5 detects the rich state. If so, the process proceeds to step 346, where the lean flag FR is set. Then, the process proceeds to step 348, where the air-fuel ratio feedback correction coefficient Kt is decreased by A. Here, A and the above a are constants, and their size relationship and purpose are the same as in the case of the constants B and b described above. On the other hand, if the condition in step 344 is not met, the process proceeds to step 330 and continues to gradually bring the air-fuel ratio into a rich state.

Similarly to the process, the current process calculates and updates the learning value MKt using the method shown in the following equation.

MKt=9-儒y人22 工 2 & BU± Thus, in step 350, after updating the correction coefficient undergraduate value MKt as described above, the present process ends. This learned value Mkt is used to calculate the fuel injection amount during the open loop control described above.

Next, step 150 is executed following the processing of step 140 (step 300 to step 350) described above.
The process, that is, the atmospheric pressure correction process will be described in detail.

FIG. 7 is a flowchart describing the process of step 150 in detail. When this process begins, first the fifth
In the 4m5ec interrupt routine shown in the figure, the state of the flag F1, which is set every ``l [sec]'', is determined (
Step 400>, it is determined whether or not to execute special processing (steps 402 to 428) that should be executed every 1 [sec]. First, in step 400, Fl
The processing for each elapse of 'l [SeC] when it is determined that =1 will be explained. In step 402, the 7-lag F1 is reset to prepare for the next time measurement, and then in step 404, the counter COP is counted up. As described in the first variation, the counter COP is cleared when the air-fuel ratio feedback process is satisfied, and counts up the time since the air-fuel ratio open process.

In the following step 406, it is determined whether COP≧700 to prevent the counter COP from overflowing,
Guard processing (step 408) is executed to reset the COP to 700 only when COP≧700. This is because the counter COP only needs to count up to "500" as described later. In step 410, which is executed next, it is determined from the state of the flag FFB whether or not the current air-fuel ratio control is in the process of feedback processing, and if the feedback process is in progress, a counter CFB that counts the duration of the feedback process is counted up. (step 412), and when the value becomes 30 or more (step 414), a flag FFBT is set to indicate that sufficient feedback processing has been performed (step 416), and the counter CFB is set to "3".
0'' (step 418), another counter CFBT is reset, and the process proceeds to step 422. On the other hand, when it is determined in step 410 that flag FFB=O, or when it is determined that CFB<30 in step 414, the above process is not executed and the process directly proceeds to step 422. In step 422, another counter CFBT is counted up. As mentioned above, the counter CFBT is reset when the air-fuel ratio feedback process continues for a sufficient period of time (step 42).
0) Buy something. Therefore, if the air-fuel ratio feedback is not performed, or if it is performed but is always continuous, or if sufficient time has not elapsed, the counter CFBT will gradually take on a larger value and the following step 42
4, it is determined whether the value exceeds 240 or not.

Then, when CF 8 digits ≧ 240 (at this point, the counter CFB is cleared (step 426) and the counter CFBT is cleared (step 428), and after completing the processing every 1 [sec], step 500 Proceed to the subsequent processing.Thus, due to the action of these counters CFB and CFBT, flag FFBT is set to 4 minutes when counter CFB counts 30 [SeC] within the period in which CFB counts 240 [sec]. It is set to "1" only when the air-fuel ratio and feedback processing are performed for 30 seconds or more during the period.

When it is determined in step 400 that flag F1=0, the process directly proceeds to step 500 and subsequent steps without performing the above-described process every 1 [Sec]. First, step 5
At 00, it is determined whether the flag FOR is set and whether or not the air-fuel ratio opening process is currently being performed. FOP=
1 and the air-fuel ratio opening process is in progress, the flag FOP is reset in step 502>, and it is further determined whether the aforementioned flag FFBT is set (step 504). Then, only when FFBT=1, the flag FFBT is reset (step 50
6), counters CFB and COP are cleared (steps 508 and 510). flag FOR
is in reset state or still flag FFB
When T is in the reset state, the above-mentioned counter C
The process proceeds to steps 512 and 514 of the direct method without clearing the FB and COP, and the throttle opening TA is 60 ["deg] or more, and the rotation speed N is 4000 [r om] JX lower F. It is determined whether or not the condition Alf=, that is, the condition in which the output of the intake pressure sensor 15 is regarded as atmospheric pressure is satisfied.

If the above two conditions are not met, this step 150
However, when the two conditions are satisfied, the atmospheric pressure correction amount Kp is determined using the intake pipe pressure Pm at that time.

Here, first, the value of the previous atmospheric pressure correction amount Kp is expressed as Kpol.
d and memorize it (step 516), the atmospheric pressure correction amount Kp matching the current intake pipe pressure Pm (=atmospheric pressure) is searched using a map showing the relationship between Pm and Kp prepared in advance. , is determined by interpolation calculation (step 518). After the atmospheric pressure correction amount Kl) is determined, the content of the counter COP mentioned above is determined if COP≦5.
00 (step 520), and the CO
When P≦500, that is, when 500 [sec] has not yet passed since the air-fuel ratio feedback process was continuously executed for 30 seconds within a 4-minute period, the learned value MKt is corrected for atmospheric pressure. Change in quantity (KDo
fd/KD) (step 522), and the process of step 150 ends. On the other hand, COP>50
If it is 0, the process of step 150 ends without changing the learned value MKt.

The above is a detailed explanation of the air-fuel ratio correction control (step 140) and the atmospheric pressure correction control (step 150) in the aforementioned main routine (Fig. 4).The physical meaning of these processes can be summarized as follows. It is as follows. Fluctuations in atmospheric pressure cause fuel injection! Since it affects the amount of iFI, it is necessary to adjust the atmospheric pressure correction port Kp appropriately according to the atmospheric pressure. However, the fuel injection control device of this embodiment does not newly provide an atmospheric pressure sensor, and captures the slight chance that the intake pressure sensor 15 detects the atmospheric pressure, thereby increasing the atmospheric pressure correction amount Kp.
is being updated. Therefore, air-fuel ratio correction becomes a problem. In other words, if a change in atmospheric pressure actually occurs before the opportunity to perform atmospheric pressure correction arrives, the air-fuel ratio will deviate from the predetermined value based on the change in atmospheric pressure because the atmospheric pressure correction ff1KE) remains unchanged. , correction by air-fuel ratio feedback processing will be executed. Then, the air-fuel ratio correction coefficient Kt at this time is learned and the learned value MKt is also updated. However, the air fuel ratio at this time! rlJ'm is corrected to include changes in the air-fuel ratio due to changes in atmospheric pressure, and when atmospheric pressure is detected in this state and the atmospheric pressure correction amount Kp is updated to an appropriate value. In this case, redundant atmospheric pressure correction will be performed. In order to avoid this duplication, the value of the counter COP is used to determine whether the air-fuel ratio deviation based on the current atmospheric pressure is also corrected by the air-fuel ratio control. In other words, the counter COP is set during a period (4 minutes) in which the atmospheric pressure does not change significantly even when running uphill, etc., for a sufficient period of time (3 minutes) to absorb the influence of the atmospheric pressure at that time.
0 seconds) is reset when the air-fuel ratio feedback process is executed, and the elapsed time after such a state ends is measured. Therefore, if COP≦500, it is assumed that the learning value MKt at that time reflects the influence of the current atmospheric pressure, and the learning value 1MKt is changed according to the change in the atmospheric pressure correction amount to perform redundant correction. Avoid it.

When the increase coefficient Kh air-fuel ratio correction coefficient Kt and the atmospheric pressure correction amount Kp suitable for the operating condition of the internal combustion engine 1 are determined as described above, the final fuel injection time TAU is determined by the process of step 160 as described above. is calculated and determined.

In parallel with the execution of various controls in the main routine in this way, execution of fuel injection based on the optimum opening time of the fuel injection valve 6 calculated in step 160;
And ignition timing control is executed by the following interrupt routine. The flowchart in FIG. 8 is the interrupt routine, and is the 30'CA interrupt routine that controls the start of fuel injection. This control routine uses 30 degrees of crank angle.
' It is started as an interrupt routine by a pulse input from the rotation angle sensor 18 for each CA, and first, step 600
The time when a pulse is input from the cylinder discrimination sensor 19 is set to 0, and each time a pulse is input from the rotation angle sensor 18, the pulse is input from the rotation angle sensor 18.
The current crank angle is determined by knowing the value of a counter (not shown) that is repeatedly counted up from 24 to 24. In the following step 602, step 60
Based on the crank angle determined at 0, it is determined whether or not it is necessary to start the intake stroke of the first cylinder or the sixth cylinder. Since two fuel injections are performed per revolution of the internal combustion engine 1, the current stroke of the internal combustion engine is a stroke in which fuel injection is performed in synchronization with the rotation of the internal combustion engine, that is, the intake air of the first or sixth cylinder. This corresponds to determining whether the crank angle is at the start of the stroke. If the determination in step 602 is rYESJ, in step 604 a command signal is output to the output port 38 to immediately start fuel injection, and the fuel injection valve 6 is opened. Then, in the subsequent step 606, the value obtained by adding the valve opening time [AU of the fuel injection valve 6 obtained in step 160 of FIG. When the fuel injection process is completed, or when it is determined that it is not necessary in step 602, the current crankshaft is A determination is made as to whether the angle is 90' before the top dead center of any cylinder, and if this is the case, the timing t2 for turning on the igniter 16 is determined by known ignition timing control.
is determined in the same manner as in step 606 and set in the conveyor B register (step 610). After this process, or when it is determined in the process of step 608 that the interrupt is not 90' before top dead center, an additional 600' before top dead center is detected.
It is determined whether or not it is an interrupt (step 612);
When the interrupt occurs 60' before the top dead center, time t3 for turning off the igniter 16 is set in the conveyor B register, and the water interrupt routine ends.

The conveyor A of timer 33H continues to compare the set fuel injection end time t1 with the control real time Tr, and when the control real time Tr reaches the fuel injection end time t1,
An interrupt request is issued to the CPU 30 to start the conveyor A match interrupt routine. This is the routine shown in the flowchart of FIG. 9, and at step 700, a signal to end the fuel injection is output to the output port 38, the fuel injection valve 6 is closed, and the fuel injection is ended. let Immediately after completing the process in step 700, 1 is added to RTN.
Then, the match interrupt routine for the main conveyor ends.

Similarly, in the conveyor B in the timer 33, a comparison is made between the time t2 or t3 at which the cell was set and the real time T r on control, and when they match, a conveyor B match interrupt is sent to the CPU 30 (i be exposed.

FIG. 10 is a flowchart of the routine executed by the CPU 30 when the interrupt request occurs. As shown in the figure, it is determined whether the interrupt request is due to (M!l i 2) (step 800).

If the interrupt request is due to time t2, an output signal that turns on the igniter 1('l) is generated at the output port 3B (step 802>, and if the interrupt request is due to time t3, the igniter 16 is turned on by Δ). ] The output to be output is nullified to output port 3B (step 804).
, Processing of this routine: 3.

According to the fuel injection control device of this embodiment configured as described above, the following effects are obvious.

First, its mechanical components are no different from the conventional DJ residual fuel injection control device, and no new parts such as an atmospheric pressure sensor are added, making it inexpensive. Moreover, since the pressure regulator 23 releases the back pressure to the atmosphere, generation of paper when restarting the internal combustion engine 1 at a high temperature is avoided, and good starting characteristics can be obtained.

In addition, correction of the fuel injection amount due to atmospheric pressure fluctuations is performed immediately when the atmospheric pressure is detected by the intake pressure sensor 15, and basically, deviations in the fuel amount due to atmospheric fluctuations are corrected by the atmospheric pressure correction amount Kl). Corrected.

On the other hand, in this embodiment, the above-mentioned atmospheric pressure correction is performed by taking advantage of the slight chance that the intake pipe pressure matches the atmospheric pressure without using a separate atmospheric pressure sensor, so the atmospheric pressure correction amount follows the fluctuations in the atmospheric pressure. You may not get it.

However, even in such a case, the fuel amount is always feedback corrected by the air-fuel ratio correction process so that the desired air-fuel ratio is achieved, and the value is also learned. Therefore, until the atmospheric pressure correction follows the actual atmospheric pressure, compensation by the air-fuel ratio correction process is executed.

Furthermore, when compensation for atmospheric fluctuations is performed by the air-fuel ratio correction process as described above, if the atmospheric pressure correction could follow the actual atmospheric pressure, the fuel m due to atmospheric pressure fluctuations would be
It is assumed that the following corrections will be made redundantly. In this embodiment, even in such a case, the air-fuel ratio correction amount is changed based on the fluctuation ratio of the atmospheric pressure correction amount, so the air-fuel ratio does not become too rich or lean, and it is extremely good under any operating condition. It is possible to obtain excellent driving characteristics.

In addition, in the above-mentioned embodiment, atmospheric pressure correction control step 1
As described in the detailed explanation of 50 (Fig. 7), when the counter COP is 500 or less, the learned value MK of air-fuel ratio correction is
t is changed. However, under conditions where the atmospheric pressure decreases, for example, when climbing a mountain, the load on the internal combustion engine 1 is high and the air-fuel ratio feedback process is generally not performed. Therefore, at this time, the learned value MKt is stored as it is in the lowland (high atmospheric pressure), and there may be no need to change it in conjunction with the atmospheric pressure correction.

On the other hand, under conditions where atmospheric pressure increases, such as when exiting the plane, there is a very high possibility that air-fuel ratio feedback processing will be executed, and the learned value MKt will be a value that corresponds to the atmospheric pressure at that time, so atmospheric pressure correction will be required. It is necessary to change accordingly.

Therefore, as shown in FIG. 11, in the series of processes from step 512 to step 522 explained in FIG.
0 (step 520) plus a new condition to limit when the atmospheric pressure shows an increasing change, )(pol
d>Kl) (step 900) to the above step 52
It may be added immediately before or after the 0 processing. With this added processing, step 512 and step 51
Update of atmospheric pressure correction fttKl) (step 516, step 51) executed when the two conditions of 4 are satisfied.
After 8), the learning value MKt is changed only when the two conditions Kpold>Kp (step 900> and COP≦500 (step 520) are satisfied,
This will prevent unnecessary changes to the learned value MKt.

That is, deviations in the air-fuel ratio during the air-fuel ratio opening process caused by unnecessary changes in the learned value MKt are prevented, and further improvement in driving characteristics is achieved compared to the above-described embodiment.

[Effects of the Invention] As described above in detail with reference to the embodiments, the fuel injection control device of the present invention suppresses the generation of paper by constantly releasing the back pressure of the pressure regulator to the atmosphere, and has a simple and inexpensive configuration that can be used in internal combustion engines. Improvements in starting characteristics are achieved, including even during high-temperature restarts.

In addition, regarding the influence of atmospheric pressure on the fuel port, there is no need to install a new atmospheric pressure sensor. Atmospheric pressure correction is executed at the slightest opportunity, and the period until atmospheric pressure correction follows the actual atmospheric pressure is compensated by air-fuel ratio correction, and when it follows atmospheric pressure, duplicate correction is skillfully avoided.

In other words, although the configuration of the fuel injection control device that controls the operating state of the internal combustion engine has been simplified, reliability has been improved, and costs have been reduced, the control accuracy is extremely high. It is an excellent fuel injection control device that can maintain good starting characteristics of an internal combustion engine, ability to follow atmospheric pressure fluctuations, etc.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a schematic configuration diagram of an embodiment, and Fig. 3 is an output characteristic diagram of the throttle sensor.
Figure 4 is a flowchart of its main routine, Figure 5 is a flowchart of its 4ms interrupt routine, Figure 6 is a detailed flowchart of its air-fuel ratio correction, Figure 7 is a detailed flowchart of its atmospheric pressure correction, and Figure 8. 10 to 10 show a flowchart of an interrupt routine that controls execution of fuel injection and ignition timing control, and FIG. 11 shows a flowchart of another embodiment of atmospheric pressure correction. 1... Internal combustion engine 6... Fuel injection valve 11... Throttle valve 15... Intake pressure sensor 18... Rotation angle sensor 20... Electronic control circuit 23... Pressure regulator 30... CPU

Claims (1)

[Scope of Claims] A fuel injection means for injecting fuel into an intake passage of an internal combustion engine at a predetermined pressure with atmospheric pressure as a back pressure; a basic fuel injection time determining unit that determines the basic fuel injection time based on internal pressure and rotational speed; an air-fuel ratio correcting unit that corrects the air-fuel ratio of the basic time based on a difference between the exhaust composition of the internal combustion engine and a predetermined exhaust composition; atmospheric pressure correction means that performs atmospheric correction for the basic time based on the value when the internal combustion engine intake passage pressure reaches a value that is considered to be atmospheric pressure; an estimating means for estimating whether or not an air-fuel ratio correction is being performed based on a deviation in exhaust composition; A fuel injection control device for an internal combustion engine, comprising: an air-fuel ratio correction amount adjusting means for changing the amount of air-fuel ratio correction when it is estimated that the air-fuel ratio correction is being performed.