JPS63173826A - Fuel injection method for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of flame-out at the time of transition by correcting the latest fuel injection start timing according to a change of fuel injection start timing and the interval from the fuel injection start timing computing timing to the fuel injection start timing. CONSTITUTION:During operation of an engine, in an interruption routine started at every designated crank angle in an electronic control circuit 14, first the latest fuel injection start timing theta is computed according to an intake pipe pressure detected by a pressure sensor 6 and the engine speed detected by a rotation sensor 48. Secondly the absolute value of a difference between the latest value theta and the preceding computed value is compared with a designated value. When the absolute value of the difference is larger than a designated value K1, a correction amount theta is computed according to the difference and a coefficient K2 of correction expressed by the ratio of a crank angle between the latest value theta computing timing C2 and the preceding computing timing C1 to a crank angle between the computing timing C2 and the fuel injection start timing. The latest value theta is corrected according to the above correction amount #.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection method for an internal combustion engine, and in particular calculates the fuel injection start timing for each cylinder at a predetermined timing, and calculates the latest fuel injection start timing that has been calculated. The present invention relates to a fuel injection method for an internal combustion engine in which fuel injection is started independently for each cylinder at a certain time.

[Prior art] Conventionally, the basic fuel injection time is calculated based on the engine load (intake pipe pressure or intake air amount per engine revolution) and the engine rotation speed, and this basic fuel injection time is used to calculate the intake air temperature or engine cooling water temperature. An internal combustion engine is known in which a fuel injection time is determined by correcting the fuel injection time, etc., and the fuel injection valve is opened for a time corresponding to the fuel injection time to inject fuel independently to each cylinder. In addition, in such an independent injection type internal combustion engine, the a mixture and the lean mixture are formed in layers in the combustion chamber, and the rich mixture is ignited by a spark to perform stratified combustion, thereby burning the lean mixture as a whole. is being carried out. In such a stratified combustion engine, the misfire range changes depending on the engine load and engine speed, so
As shown in Fig. 2, the fuel injection start timing is determined based on the engine load (intake pipe pressure PM in the example shown in Fig. 2) and the engine speed NE, and the fuel injection start timing is determined based on the engine load (intake pipe pressure PM in the example shown in Fig. 2) and the engine speed NE. The injection start timing is calculated, and fuel is injected from the calculated fuel injection start timing.

On the other hand, the fuel injection time increases as the engine load increases, and as the engine speed increases, the fuel injection interval time decreases, so fuel injection starts at the fuel injection start time due to a delay in the fuel injection start timing calculation timing. In order to prevent this from not being executed, the fuel injection start timing calculation timing is changed depending on the engine load (in the example of FIG. 3, the intake pipe pressure PM) and the engine rotational speed NE, as shown in FIG. ing. In other words, as the engine load increases, the fuel injection time becomes longer, so the fuel injection start timing is calculated at a crank angle position advanced from top dead center, and when the engine rotation speed increases, the fuel injection start timing is calculated from the point where the fuel injection start timing is calculated. Since the time until the injection start timing is shortened, the fuel injection start timing is calculated at a crank angle position that is advanced from the top dead center.

As a technology related to the present invention, there is a technique disclosed in Japanese Patent Application Laid-Open No. 1983-1981, in which the fuel injection start timing of a cylinder to which fuel is to be injected is determined based on the fuel injection amount of the cylinder in which the previous injection was performed. There is a technique described in Publication No. 3515.3.

(Problem to be Solved by the Invention) However, in an engine where the fuel injection start timing is calculated based on the engine load and engine speed as described above, when the engine load or engine speed is ．In the case of a transient period when the fuel injection start timing is (Determined by the engine load and engine rotation speed near the valve closing point)
There is a problem in that an error occurs between the fuel injection start timing and the calculated fuel injection start timing, resulting in a misfire.

For example, if we accelerate from point A to point B via point B and the fuel injection start timing calculated at point B is 0 as shown in Figures 2 and 4, then at point B, The calculated fuel injection start timing is the required value at point B (10@CA
BTDC), but since the engine load and engine speed change during acceleration from point B to point 0, the required value for the fuel injection start timing at point 0 is 20'CA ATDC.

However, at point 0, the fuel injection start timing is controlled by the fuel injection start timing calculated at point B, so an error of δθ occurs between the required value and the actual value. For this reason, the actual value of the fuel injection start timing advances with respect to the required value, and therefore enters the misfire region shown in FIG. 5 and misfire occurs. Additionally, when the engine decelerates, the actual value of the fuel injection start timing will be delayed relative to the required value.
As can be understood from FIG. 5, the engine enters the misfire region and misfire occurs. When a misfire occurs in this way, as can be understood from FIG. 5, torque fluctuation becomes large and acceleration/deceleration shock and surging occur.

The present invention has been made to solve the above-mentioned problems, and is an internal combustion engine that prevents the actual value of the fuel injection start timing during transient times from deviating from the required value, thereby preventing the occurrence of acceleration/deceleration shock or surging due to misfire. The purpose of this invention is to provide a fuel injection method.

[Means for solving problems]

To achieve the above object, the present invention provides a fuel injection method for an internal combustion engine in which a fuel injection start time is calculated at a predetermined calculation timing and fuel injection is started from the latest calculated fuel injection start time. The difference between the fuel injection start time and the fuel injection start time calculated before the latest fuel injection start time calculation timing, and the difference between the latest fuel injection start time calculation timing and the latest fuel injection start time with respect to the interval between the calculation timings. The present invention is characterized in that the latest fuel injection start timing is corrected based on a ratio of intervals up to the start timing.

[Effect]

Next, the principle of the present invention will be explained with reference to FIG. 9 showing an embodiment. Since the intervals between calculation timings C1, C2, and C3 are approximately equal, the latest fuel injection start timing θ calculated at calculation timing C2 and the fuel injection start timing θ calculated at calculation timing C1 before calculation timing C2, - 1 and the latest fuel injection start timing θ1 using the difference θ lid −θi−1
By correcting, it is possible to predict the calculated value of the fuel injection start timing at the next calculation timing C3. On the other hand, since the fuel injection start timing exists between calculation timing C2 and calculation timing C3, the interval α between calculation timing C1 and calculation timing C2 and the interval β from calculation timing C2 to the latest fuel injection start timing By correcting the predicted calculated value using the ratio β/α, the required value of the fuel injection start timing can be predicted.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to predict the requested value of the fuel injection start timing and start fuel injection from the point corresponding to this one requested value, thereby preventing misfires from occurring during transient periods. This has the effect of preventing acceleration/deceleration shocks and surging.

〔Example〕

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

FIG. 6 schematically shows an internal combustion engine equipped with a fuel injection amount control device to which the present invention is applicable.

This engine is controlled by an electronic control circuit such as a microcomputer, and a throttle valve 8 is arranged downstream of an air cleaner (not shown), and a surge tank 12 is arranged downstream of the throttle valve 8. It is being A diaphragm type pressure sensor 6 is attached to this surge tank 12. This pressure sensor 6 is connected to a filter (Fig. 7) composed of a CR filter or the like that has a small time constant (for example, 3 to 5 m5ec) and good responsiveness to remove the pulsating component of the intake pipe pressure. There is.

Note that this filter may be built into the pressure sensor, or it may bypass the throttle valve 8 and be installed in the surge tank 12 on the upstream side of the throttle valve and the downstream side of the throttle valve.
A bypass path 14 is provided to communicate with the.

This bypass path 14 has an opening degree of 1! by a pulse motor 16A equipped with a 4-pole stator. A knotted l5C (idle speed control) pulp 16B is attached. The surge tank 12 is the intake manifold 1
8, communicates with the combustion chamber of the engine 20 via an intake boat 22 and an intake valve 23.

An electromagnetic fuel injection valve 24 is attached to each cylinder so as to protrude into the intake manifold 18.

The combustion chamber of the engine 20 includes an exhaust valve 25 and an exhaust boat 26.
The exhaust manifold 28 communicates with a catalyst device (not shown) filled with a three-way catalyst. A 0□ sensor 30 is attached to the exhaust manifold 28 and outputs a signal that is inverted at the stoichiometric air-fuel ratio. A cooling water temperature sensor 34 is installed in the engine block 32 so as to penetrate through the engine block 32 and protrude into the water jacket. This cooling water temperature sensor 34 detects the engine cooling water temperature and outputs a water temperature signal, and the water temperature signal represents the engine temperature.

Note that engine oil salt may be detected to represent the engine temperature.

A spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and protrude into the combustion chamber. This spark plug 3 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a microcomputer or the like.

Inside the distributor 40, a cylinder discrimination sensor 46 and a rotation angle sensor 48 are installed, each of which is composed of a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. For example, the cylinder discrimination sensor 46 has an angle of 720°.
A cylinder discrimination signal is output for each CA, and the rotation angle sensor 48 outputs an engine rotation speed signal, for example, every 30° CA.

As shown in FIG. 7, the electronic control circuit 44 includes a microprocessing unit (MPU) 60, a read-only memory (ROM) 62, and a random access memory (R
AM) 64, backup ram (BU-RAM) 66,
Input/output capotro 8, input port door 0, output port door 2.
74, 76 and a bus 75 such as a data bus or a control bus that connects them. An analog-to-digital (A/D) converter 78 and a multiplexer 80 are connected in sequence to the input/output capotro 8. The pressure sensor 6 is connected to the multiplexer 80 via a filter 7 and a buffer 82 which are composed of a resistor R and a capacitor C, and the cooling water temperature sensor 34 is also connected via a buffer 84 . The MPU 60 controls the multiplexer 80 and the A/D converter 78 to
The output of the pressure sensor 6 and the output of the cooling water temperature sensor 34 that are input through the converter are sequentially converted into digital signals and stored in the RAM 64. Therefore, the multiplexer 80, A/D converter 7, MPU 60, etc. act as sampling means for sampling the pressure sensor output at predetermined time intervals. 0! to input port door 0 via comparator 88 and buffer 86. The sensor 30 is connected, as well as a cylinder discrimination sensor 46 and a rotation angle sensor 48 via a waveform shaping circuit 90. Output port door 2 is drive circuit 9
2 to the igniter 42, and the output port door 4
is connected to the fuel injection valve 24 via a drive circuit 94 with a down counter, and the output port door 6 is connected to the ISC valve pulse motor 16A via a drive circuit 96.

Note that 98 is a clock and 99 is a timer. The above RO
The M62 stores in advance a control routine program, etc., which will be explained below.

Next, a control routine of an embodiment in which the present invention is applied to the above engine will be explained.

FIG. 8 shows a main routine that is executed every predetermined time (for example, 4 m5ec). In step 100, the engine rotation speed NE and intake pipe pressure PM are acquired, and in step 102, the engine rotation speed Nu and the intake pipe pressure are taken in. PM
The basic fuel injection time TP is calculated based on the following. Then, in step 104, the basic fuel injection time TP is corrected based on the intake air temperature, engine cooling water temperature, etc., and the fuel injection time TA is
Calculate LI.

FIG. 1 shows an interrupt routine that is interrupted every crank angle determined by the intake pipe pressure and engine speed shown in FIG. 3. When this interrupt routine is started, a second From the map showing the fuel injection start timing shown in the figure, engine rotation speed NE and intake pipe pressure P are calculated.
In the first step 112 in which the latest fuel injection start timing θ is calculated according to M, the latest fuel injection start timing θ is calculated in order to prevent hunting of the fuel injection timing.

The absolute value lθ, -θ, -I 1 of the difference between the fuel injection start timing θi-1 and the previously calculated fuel injection start timing θi-1 is compared with a predetermined value 1. When the absolute value 1θ1-θe-11 is larger than the predetermined value 1, the required value of the fuel injection start timing determined by the engine load and engine rotational speed near the time when the intake valve closes and the calculated value of the fuel injection start timing are calculated. It is determined that the error is large and a misfire will occur, and in step 116, a correction value Δθ is calculated according to the following equation.

Δθ-(θ1-θ, -1) ・K2...(1) However, K! As shown in FIG. 9, is the crank angle α between the calculation timing C2 at which the latest fuel injection start timing was calculated and the calculation timing C1 before the calculation timing C2, and the difference between the calculation timing C2 and the fuel injection start timing. is a correction coefficient expressed by the ratio β/α of the crank angle β.

On the other hand, if the absolute values 1θ, -〇, -21 are less than 1 to the predetermined values, it is determined that the error between the required value of the fuel injection start time and the calculated value of the fuel injection start time is small and no misfire will occur. In step 114, the correction value Δθ is set to 0. In the next step 118, the latest calculated fuel injection start timing θ
The effective fuel injection start timing θ is calculated by adding the correction value Δθ to . Then, the latest fuel injection start time θ calculated in step 120 is set to the value of the previously calculated fuel injection start time θ, −1, thereby rewriting the previous fuel injection start time.

FIG. 10 shows an interrupt routine that is interrupted when the effective fuel injection start timing θ calculated in step 118 of FIG. Zero-order step 124 where the electromagnetic coil is energized and fuel injection begins.
Now, the fuel injection time TAU calculated in the main routine
In step 126, a fuel injection stop time is calculated by adding the fuel injection time TAU to the current time (fuel injection start time), and this fuel injection stop time is set as the time to stop energizing the fuel injection valve. set to the down counter. This down counter continues counting down until the energization stop time is reached.

FIG. 11 shows an interrupt routine that is interrupted when the count value of the down counter reaches 0. When the count value of the down counter reaches 0, step 128
At this point, power supply to the fuel injection valve is stopped and fuel injection is completed.

As explained above, according to this embodiment, the required value of the fuel injection start timing determined by the intake pipe pressure and engine rotational speed near the time when the intake valve closes is predicted, and from the time corresponding to this required value. Since fuel injection can be started, misfires during transient times are prevented, which reduces torque fluctuations and prevents acceleration/deceleration shocks and surging.

Although the example above uses the intake pipe pressure as the engine load, in engines etc. where the basic fuel injection time is determined by the intake air amount and the engine speed, the engine load is the intake pipe pressure taken per engine rotation. The amount of air may also be used.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing an interrupt routine that is interrupted at each fuel injection start timing calculation timing according to the embodiment of the present invention, Fig. 2 is a diagram showing a map of fuel injection start timing, and Fig. 3 is a diagram showing a fuel injection start timing calculation timing. A diagram showing a timing map,
Fig. 4 is a diagram for explaining the deviation between the required value and the actual value of the fuel injection start timing, Fig. 5 is a diagram showing the misfire region, and Fig. 6 is a diagram showing an internal combustion engine to which the present invention is applicable. Schematic diagram, No. 7
6 is a block diagram showing details of the control circuit of FIG. 6, FIG. 8 is a flowchart showing the main routine of the above embodiment, FIG. 9 is a diagram showing the relationship between fuel injection start timing and calculation timing, etc., and FIG. The figure is a flowchart showing an interrupt routine that is interrupted at the fuel injection start time, and FIG. 11 is a flowchart showing the interrupt routine that is interrupted at the fuel injection end time. 6... Pressure sensor, 24... Fuel injection valve, 46... Cylinder discrimination sensor, 48... Rotation angle sensor.

Claims (1)

[Claims] (1) In a fuel injection method for an internal combustion engine in which a fuel injection start time is calculated at a predetermined calculation timing and fuel injection is started from the latest calculated fuel injection start time, the latest fuel injection start time and the latest and the ratio of the interval between the latest fuel injection start time calculation timing and the latest fuel injection start time to the interval between the calculation timings. A fuel injection method for an internal combustion engine, comprising: correcting the latest fuel injection start timing.