JPH0646012B2 - Fuel injection control method for internal combustion engine - Google Patents

Description

The present invention relates to a fuel injection control method for an internal combustion engine, and more particularly to a fuel injection control method for an internal combustion engine that preferably prevents the occurrence of a surge phenomenon during idle travel. Regarding

[Prior Art] Conventionally, a load of an internal combustion engine is obtained based on various parameters that represent operating conditions such as an intake air intake amount and a rotational speed of the internal combustion engine, and thereby a fuel injection amount of the internal combustion engine is controlled. In an internal combustion engine, when the rotational speed of the internal combustion engine fluctuates due to the occurrence of irregular combustion, the fuel injection amount fluctuates accordingly, and the existence of a control delay time causes
It has been known that a repetitive phenomenon in which the rotation speed further fluctuates may occur. FIG. 6 shows the number of revolutions N of the internal combustion engine, the value Q / N obtained by dividing the intake air amount Q by the number of revolutions N, the basic fuel injection pulse width (basic fuel injection time) τ 0, and the empty time during execution of such fuel injection control. 3 is a graph schematically showing the states of the fuel ratio A / F and the output torque of the internal combustion engine. As shown in the figure, a change in the rotation speed N of the internal combustion engine is reflected in the basic fuel injection pulse width with a control delay, and further, as a fluctuation (output torque fluctuation) of the air-fuel ratio A / F of the internal combustion engine with a predetermined delay time. You can see that it appears.

In a vehicle equipped with an internal combustion engine that performs fuel injection control, fluctuations in output torque due to the above-described repetitive phenomenon cause resonance of the drive system of the vehicle, which causes low-frequency vibration (surge) in the vehicle front-rear direction, which is unsuccessful to passengers. May give a pleasant sensation.

Therefore, various measures have conventionally been taken to prevent such a surge phenomenon, for example, Japanese Patent Laid-Open No. 56-16.
Proposal to prevent the occurrence of a surge phenomenon by apparently reducing the fluctuation of the rotational speed of the internal combustion engine, as in the "electronic fuel injection control device" of Japanese Patent No. 2234, and Japanese Patent Laid-Open No. 58-58.
Proposal to prevent the surge phenomenon that occurs during decelerating traveling and idle traveling by setting a lower limit value of the fuel injection amount according to the traveling state, as in the "fuel injection control method for internal combustion engine" of Japanese Patent Publication No. 155226. And so on.

[Problems to be Solved by the Invention] Against the background of such conventional technology, the present invention intends to solve the following problems.

(1) The occurrence of the surge phenomenon is due in part to the existence of a delay time until the change in the parameter indicating the operating state of the internal combustion engine is reflected in the output torque of the internal combustion engine. It is possible that a surge may occur due to fluctuations in the amount. Therefore, it is considered that the surge cannot be completely prevented even if the fluctuation of the rotational speed is apparently suppressed to a small level, which may cause a problem in some cases.

(2) Since the surge phenomenon is caused by the twisting phenomenon of the drive system, etc., depending on the running condition of the vehicle,
A surge may not occur even if the rotational speed fluctuates. On the other hand, if control is performed to suppress the rotational speed fluctuation to be apparently small, the feedback control of the rotational speed of the internal combustion engine cannot be sufficiently executed. It was also possible.

Therefore, the present invention has been made to solve the above problems, and an object thereof is to propose a fuel injection control method for an internal combustion engine that can suitably prevent a surge phenomenon.

Structure of the Invention [Means for Solving Problems] In order to achieve the above object, the present invention has the following structures as means for solving the problems. That is, as shown in FIG. 1, a parameter reflecting the load of the internal combustion engine is detected (step P1), and the fuel injection amount of the internal combustion engine is obtained based on the detected parameter (step P2) to control the fuel injection (step P2). (Step P5) In the fuel injection control method for an internal combustion engine, at the time of idling (step P3: YES), a predetermined weight is given between the value of the fuel injection amount obtained above and the actual fuel injection amount actually injected last time. The average value is calculated and used as the fuel injection amount (step P6), and when the idle speed control other than during the idle running is performed (step P4: YES), the calculated fuel injection amount is reflected more than the weighted average value. Is set as the fuel injection amount (step P7), and fuel injection is performed using the fuel injection amount calculated at that time (step P5). Structure of the fuel injection control method of the combustion engine is it.

[Operation] In the present invention thus configured, the parameter reflecting the load of the internal combustion engine is detected (step P1), and when not in the idle state (steps P3, P4: NO), the fuel is detected based on the detected parameter. Fuel injection is performed at the fuel injection amount (step P2) for which the injection amount is obtained (step P2).
5). When it is determined that the vehicle is idling (step P3: YES), a predetermined weighted average value is calculated between the value of the fuel injection amount (step P2) obtained above and the actual fuel injection amount actually injected last time. Is calculated as the fuel injection amount (step P6), and fuel injection is performed using this (step P5). Further, when it is determined that it is during the idle speed control other than the idle running (step P
4: YES), a value that reflects the calculated fuel injection amount more than the weighted average value is set as the fuel injection amount (step P7), and fuel injection is performed using this (step P5).

At the time of idling, the value of the fuel injection amount calculated based on the parameter is converted into a weighted average value with the actual fuel injection amount that was actually injected last time. Is not reflected in. Therefore, the surge phenomenon resulting from the fluctuation of the output torque is favorably prevented. Further, at the time of idle speed control other than during idle running, the value of the fuel injection amount is set to a value that largely reflects the value of the fuel injection amount obtained above. Therefore, the idle speed is controlled with good responsiveness.

[Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the drawings in order to further clarify the configuration and operation of the present invention described above. FIG. 2 is a schematic configuration diagram showing a schematic configuration of an internal combustion engine as an embodiment to which the method of the present invention is applied.

As shown in the figure, the internal combustion engine 1 draws in air from the atmosphere, mixes the fuel injected from the fuel injection valve 3 with the air, and introduces it to the intake port 5, and an electric spark formed in the spark plug 9. A combustion chamber 11 for taking out the combustion energy of the air-fuel mixture ignited as a rotary motion through a piston 10 and an exhaust system 13 for exhausting the burned gas through an exhaust port 12 are configured.

The intake system 7 is provided with an air cleaner (not shown), an air flow meter 14 for detecting the intake air amount Q, a throttle valve 16 for controlling the intake air amount, and a surge tank 18 for smoothing the pulsating flow of the intake air from upstream. There is. The intake air intake amount Q is controlled by the opening degree of the throttle valve 16 which is interlocked with an accelerator pedal (not shown), but when the throttle valve 16 is fully closed (idle time), the bypass passage 20 that bypasses the throttle valve 16 is used. The intake air amount Q is controlled by an idle speed control valve (hereinafter abbreviated as ISCV) 22 provided in the. The intake system 7 has a built-in idle switch that is turned on when the slot valve 16 is fully closed, and a throttle sensor 23 that also detects the opening of the throttle valve 16 and an intake air temperature that detects the intake air temperature THA. A sensor 24 is also provided.

The air-fuel mixture of the air sucked through the intake system 7 and the fuel injected from the fuel injection valve 3 is sucked into the combustion chamber 11 and compressed by the piston 10 and then ignited. Ignition is performed by electric sparks formed on the spark plug 9. A spark plug 9 provided in each cylinder of the internal combustion engine 1 is connected to a distributor 29 that distributes the high voltage generated in the igniter 27 in synchronization with the rotation of a crankshaft (not shown) by a high voltage cord (not shown). ing. In the distributor 29, a cylinder discrimination sensor 31 that generates one pulse for one rotation of the crankshaft is used.
And a rotation speed sensor 33 that generates one pulse for every 30 degrees of the crankshaft.

The air-fuel mixture that is ignited by spark ignition and explosively burned is discharged as exhaust gas, and the exhaust system 13 uses an oxygen concentration sensor (hereinafter, referred to as “O”) for detecting the air-fuel ratio of the air-fuel mixture based on the composition of the exhaust gas. ₂ ) 35, a three-way catalyst device 37 for purifying exhaust gas, and the like.

The cylinder block 38 of the internal combustion engine 1 is cooled by the circulating cooling water, and the temperature THW of the cooling water is detected by the cooling water temperature sensor 39.

The output signals of the above-described sensors for detecting the operating state of the internal combustion engine are input to the electronic control unit 50, and the fuel injection valve 3, ISCV 22, igniter 27, etc. are controlled according to the operating state of the internal combustion engine 1. The electronic control unit 50 is a well-known central processing unit (CPU) 51, read-only memory (ROM) 52, random access memory (RAM) 5
3, backup RAM 54 that stores the stored data
Centering on these, input port 55, output port 56
And the like are connected to each other by a bus 57 as a logical operation circuit.

An analog input section (not shown) for inputting analog signals from the air flow meter 14, the throttle sensor 23, the intake air temperature sensor 24, the O ₂ sensor 35, the cooling water temperature sensor 39, etc., to the input port 55, and the cylinder discrimination sensor 31. , A pulse input section (not shown) for inputting pulse signals from the rotation speed sensor 33, the vehicle speed sensor 62, and the like. Here, the vehicle speed sensor 62 is provided on an output shaft 65 of a transmission 64 coupled to the output shaft of the internal combustion engine 1, and the output shaft 6
A pulse signal corresponding to the vehicle speed is generated from a magnetic rotor fixed to No. 5 and a reed switch facing the rotor.

On the other hand, the output port 56 is provided with the fuel injection valve 3 provided in the intake port 5 of each cylinder and the IS provided in the bypass passage 20.
The control signal is output to the CV 22 or an igniter 27 that generates a high voltage.

The electronic control unit 50 has an ignition switch 67.
It operates by receiving power from the battery 69 via the.

Next, the fuel injection control performed in the present embodiment having the above configuration will be described with reference to the flowchart of FIG. The flowchart of FIG. 3 shows the electronic control unit 5
Among various controls performed by 0, a process for obtaining a fuel injection amount and a process for executing fuel injection are shown. The electronic control unit 50 repeatedly executes this fuel injection control routine along with other controls such as ignition timing control.

First, in step 100, the intake air amount Q, the rotation speed N, and the cooling water temperature TH of the internal combustion engine 1 read from the air flow meter 14, the rotation speed sensor 33, and the like via the input port 55.
A process for determining the fuel injection time τi is performed based on the W intake air temperature THA. A method for calculating the fuel injection time τi is well known, and thus a detailed description thereof will be omitted. However, the basic fuel injection amount (fuel injection time) is calculated based on the value Q / N that reflects the load of the internal combustion engine 1. It is general to obtain and correct this using the cooling water temperature THW, the intake air temperature THA, the air-fuel ratio A / F detected by the O ₂ sensor 35, and the like. For example, the fuel injection time τi is τi = K1 × K2 × Q / N + K3 (where K1 is a constant, K2 is a correction coefficient by the cooling water temperature THW, intake air temperature THA, air-fuel ratio A / F, etc., and K3 is the invalid fuel injection time. And other correction terms). Incidentally, here, the additional time i indicates that it is the calculation result at the time when this control routine is being executed. Therefore, τi-1 indicates the fuel injection time handled at the time when this control routine was executed last time.

Next, at step 110, it is judged if the idle switch built in the throttle sensor 23 is on, that is, if the throttle valve 16 is fully closed. When the throttle valve 16 is fully closed, the process proceeds to step 120, where it is determined whether or not the vehicle speed Vm detected by the vehicle speed sensor 62 exceeds 2 km / h.

Both the judgments at step 110 and step 120 are “YE
S ", that is, when the throttle valve 16 is fully closed (the idle switch is on) and the vehicle speed Vm exceeds 2 km / h, it can be considered that the vehicle is idling. At this time, the process proceeds to step 130, where the fuel injection time τi is set to τi ← (7 · τi-1 + τi) / 8 by using the previous calculation result τi-1. This is the fuel injection time τi−1 used previously and the fuel injection time τ obtained in step 100 this time.
This is a so-called smoothing process of taking a weighted average with i, and the influence of the newly calculated fuel injection time (τi obtained in step 100) is reflected only 1/8 in the fuel injection time τi thus determined. Therefore, the fluctuation of the fuel injection time is suppressed.

After the processing of step 130, the processing proceeds to a fuel injection control routine (step 140) that performs fuel injection using the fuel injection time τi determined in step 130. In step 140, the crank angle of the internal combustion engine 1 is determined from the outputs of the cylinder determination sensor 31 and the rotation speed sensor 33, and if a predetermined cylinder arrives at the fuel injection timing, the fuel injection valve 3 of that cylinder is opened. -Control and execute fuel injection. In the fuel injection control routine based on the fuel injection time τi (step 140), after the fuel injection is executed, the fuel injection time τi is stored in the predetermined area of the RAM 53 as the previous value τi-1 in preparation for the next execution of this control routine. Above, exit to NEXT and end this control routine once.

On the other hand, when the vehicle speed Vm is determined to be less than 2 km / h in step 120 among the above determinations, it is considered that the vehicle is almost stopped, so that the normal idle speed control is executed. You can judge.
Therefore, the process proceeds from step 120 to step 150, and it is determined whether the rotation speed N of the internal combustion engine 1 is 600 rpm or more. If the idle speed control (ISC) is performed, the normal speed N of the internal combustion engine 1 is 700 rpm.
Maintained in the vicinity of. Therefore, the rotation speed N is 600 rp
If m or more, the process proceeds to step 160, and the fuel injection time τi is obtained as τi ← (τi-1 + τi) / 2, while if the rotation speed N is less than 600 rpm, the fuel injection time obtained in step 100 Save the time τ i,
Each process proceeds to step 140 described above. The determination / processing of steps 150 and 160 described above is such that, at the time of idling, if the engine speed N of the internal combustion engine 1 is 600 rpm or more, the fluctuation of the fuel injection time τi is slightly smoothed in order to suppress the change of the engine speed N. If the speed is less than 600 rpm, it means that the fuel injection time .tau.i is not annealed at all in order to quickly recover the decrease in the rotational speed N that causes the engine stall.

If the idle switch is not turned on, the fuel injection time τi does not need to be annealed.
The fuel injection time τi obtained in step 00 is directly used in step 14
0 is used in the fuel injection control routine.

In the present embodiment configured as described above, the fuel injection time τi is slowed down during idling (steps 110, 120, 130), and the fuel injection time τi is reduced during idle speed control. Furthermore (steps 110, 120, 150, 160), when the idle speed further decreases considerably, the fuel injection time τi is not annealed (steps 110, 120, 15).
0), fuel injection is performed using the fuel injection time τi thus determined. Therefore, the fluctuation of the fuel injection time (fuel injection amount) during idling is suppressed, and the problem that a surge phenomenon occurs in the vehicle during idling is sufficiently solved. FIG. 4 is a graph showing this state, in which the fluctuation of the output torque of the internal combustion engine 1 is sufficiently suppressed with respect to the change of the rotational speed N of the internal combustion engine 1 or the change of the intake air amount Q. I understand.

Also, when the vehicle is stopped and idle speed control is being performed, only a small amount of smoothing is being performed, so
When a load such as an air conditioner is disconnected from or connected to the internal combustion engine 1 during idling, the rotation speed N of the internal combustion engine 1 can be promptly feedback-controlled to be stabilized. In addition, when the rotational speed N of the internal combustion engine 1 is less than 600 rpm, the fuel injection time τi is not slowed down at all, so that the responsiveness in the direction of increasing the rotational speed N of the internal combustion engine 1 is kept good.

Next, a second embodiment of the present invention will be described. The second embodiment is the same internal combustion engine 1 and electronic control unit 50 as the first embodiment.
The configuration is different from that of the first embodiment except for the fuel injection control routine. FIG. 5 shows a flowchart of this fuel injection control routine.

As shown, the fuel injection control routine of the second embodiment is
Except that snaps 211, 213, 215, 217, 219 are added, the same processing and determination as in the first embodiment are performed, and steps 200 to 260 of the second embodiment are the last two digits. Is the same as steps 100 to 160 of the first embodiment. Therefore, detailed description of these processes is omitted.

In the second embodiment, when it is determined in step 210 that the idle switch is on, the process proceeds to step 211, and it is determined whether the fuel cut condition is satisfied. The fuel cut is usually
This is performed when the engine speed is above a certain level and the throttle valve is fully closed. Therefore, in step 211, the rotation speed sensor 33 determines that the rotation speed N of the internal combustion engine is a predetermined rotation speed, for example, 1300 rpm or more, and the throttle valve 16 is fully closed based on the output of the throttle sensor 23. It is possible to determine that the fuel cut condition is satisfied by detecting that the vehicle is decelerating at a predetermined speed or more.

If the fuel cut condition is satisfied, the process proceeds to step 213, where the value 1 is set to the flag FC indicating that the fuel cut is performed. The initial value of this flag FC is 0. In the following step 215, the fuel injection time τi is set to 0, and then the process proceeds to step 240. In step 240, the fuel injection execution routine is executed, but the fuel injection time τi
Is set to zero in step 215, so fuel injection is not performed at all and fuel cut is performed.

On the other hand, when it is determined in step 211 that the fuel cut condition is not satisfied, the process proceeds to step 217, and it is determined whether or not the value of the flag FC is 0. Once the fuel cut condition is satisfied, the flag FC is set to the value 1, so
The determination in step 217 is “NO”, and the process proceeds to step 219. In this case, only the process of resetting the value of the flag FC to 0 (step 219) is performed, the value obtained in step 200 is stored as the fuel injection time τi, and the fuel injection in step 240 is performed by this fuel. It is executed by the injection time τ i. That is, since the previous fuel injection time τi-1 is 0 at the time of returning from the fuel cut, the fuel injection time τi is also determined to be an extremely small value when the anneal process is performed. It does nothing at all. In other words, except for the time immediately after returning from the fuel cut, the annealing process of step 220 and the subsequent steps is performed as necessary.

If the fuel cut condition is not satisfied and the value of the flag FC is zero in the determinations of steps 211 and 217 described above, the same processing as in the first embodiment is performed. In the second embodiment configured as described above, in addition to the effects of the first embodiment, when the fuel cut is performed as a result of deceleration, the fuel cut after the throttle valve 16 is fully closed is performed. At the time of return, the fuel injection time τi is not annealed so that the response of the control of the fuel injection amount immediately after the return from the fuel cut is not hindered.

The several embodiments of the present invention have been described above.
The present invention is not limited to these examples at all, for example, the fuel injection amount is obtained as a function of the rotation speed of the internal combustion engine and the cooling water temperature, the weighting coefficient in the smoothing process,
The method of the present invention is applied to a method of performing fuel injection control or a configuration using intake pipe negative pressure, throttle opening or other various intake air amount detection means instead of the configuration of detecting the intake air amount using an air flow meter. It goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

Effects of the Invention As described above in detail, according to the fuel injection control method for an internal combustion engine of the present invention, the value of the fuel injection amount obtained based on the parameter at the time of idling is used as the actual fuel injection amount obtained last time. Since it is converted into the weighted average value with the fuel injection amount, it is possible to favorably prevent the surge phenomenon due to the fluctuation of the output torque. Further, at the time of idle speed control other than during idle running, the value of the fuel injection amount is set to a value that reflects the value of the fuel injection amount obtained above to a greater extent, so that the idle speed can be controlled with good responsiveness. it can.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a schematic configuration diagram of an internal combustion engine of an embodiment of the present invention, FIG. 3 is a flow chart showing control performed in the first embodiment, and FIG. FIG. 5 is a graph showing an example of control in the embodiment, FIG. 5 is a flow chart showing the control performed in the second embodiment of the present invention, and FIG. 6 is a graph showing the state of surge phenomenon occurrence. 1 ... Internal combustion engine 3 ... Fuel injection valve 7 ... Intake system 13 ... Exhaust system 14 ... Air flow meter 16 ... Throttle valve 22 ... Idle speed control valve (ISC)
V) 23 ... Throttle sensor 24 ... Intake air temperature sensor 33 ... Rotation speed sensor 39 ... Cooling water temperature sensor 50 ... Electronic control unit 51 ... CPU 62 ... Vehicle speed sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Takeda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) References JP 61-234238 (JP, A) JP 59-196949 (JP, A) JP 58-150039 (JP, A) Actually developed 59-105040 (JP, U)

Claims (1)

[Claims] 1. A fuel injection control method for an internal combustion engine, wherein a parameter reflecting the load of the internal combustion engine is detected, the fuel injection amount of the internal combustion engine is obtained based on the detected parameter, and fuel injection is controlled. Between the calculated fuel injection amount value and the actual fuel injection amount that was actually injected last time, a predetermined weighted average value is calculated as the fuel injection amount, and during idle speed control other than during idle running,
A value that reflects the obtained fuel injection amount more than the weighted average value is set as the fuel injection amount, and fuel injection is performed using the fuel injection amount calculated at that time. Fuel injection control method.