JP2689418B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an engine of an automobile or the like, and more particularly to a device for injecting fuel a plurality of times for each combustion cycle. [Prior Art] Recently, high fuel economy, quick responsiveness, higher output, prevention of generation of harmful exhaust gas components, etc. are required for automobile engines, and all operating conditions are targeted. It is in. As a fuel injection control device for an internal combustion engine that meets these problems, for example, JP-A-60-195347 and JP-A-60-233353.
JP-A-59-211731 and JP-A-59-29733. In these devices, the fuel injection start timing and the final injection amount are determined based on so-called operating state parameters such as engine speed and load, and the amount is increased according to the engine warm-up state, acceleration state, etc. The fuel injection start timing is advanced so that the minute is sucked in during the suction stroke. On the other hand, in addition to the above-mentioned conventional example, control has been attempted in which a plurality of fuel supply timings are set in one combustion cycle.
Some are described in Japanese Patent Publication No. 3. In this device, two supply timings are set for each combustion stroke, and the proportion of the fuel supply amount at these supply timings is determined according to the engine load and the intake air temperature to accelerate the vaporization of the fuel, I'm trying to meet my demand. [Problems to be Solved by the Invention] However, in such a conventional fuel injection control device for an internal combustion engine, the fuel required for one combustion cycle is
Since it is configured to be supplied by one-time injection, it is difficult to satisfy the conflicting fuel injection timings (that is, fuel supply timings) in the steady state and the transient state, and depending on the operating state, sufficient engine stability or Responsiveness may not be obtained. That is, in a steady state, it is necessary to advance the fuel supply timing sufficiently beyond the intake stroke in order to promote the vaporization of fuel and realize a good combustion state. On the other hand, at the time of transition, it is desirable that the fuel supply timing be delayed as much as possible within the range of the intake stroke so that the fuel amount appropriately follows the change of the load. However,
In the conventional device, such contradictory fuel supply timing conditions cannot be satisfied at the same time. Even in the case of performing two fuel supply timings in one combustion cycle, the sharing ratio of the fuel supply amount is only set according to the load, etc. Since the changes are not taken into consideration, it cannot be said that the effect is necessarily sufficient. For example, as shown in FIG. 8A, the fuel amount with respect to the intake air amount per injection is Te, the calculated value based on Te at the time of the first injection is Te ₁ , and the calculated value based on Te at the time of the second injection is T
If the calculated value based on e is Te ₂ , and the load (intake air amount Qa) increases, the fuel amount required for one stroke and two revolutions is 2 ×
Since it is Te, an amount of 2 × Te ₂ fuel must be supplied by the end of the intake stroke. However, assuming that the calculated values based on Te for both the first injection and the second injection are directly injected, the total amount of fuel supplied by the two injections is Te ₁ + Te ₂ <2 × Te _2. Then, the difference between the _first injection amount Te ₁ and the second injection amount Te ₂ is ΔTe = Te ₂ −Te ₁ and the fuel shortage occurs with respect to the load, and the load from the time of the first injection to the intake stroke is increased. Can not follow. As described above, there is room for further improvement in the existing technology, that is, in the conventional apparatus in terms of improvement of responsiveness, drivability, fuel consumption, etc. in any of the steady state, the transient state and the idle state. [Purpose] Therefore, the present invention provides a first fuel supply timing sufficiently advanced from the intake stroke for each combustion stroke, and a start of the intake stroke within the same combustion stroke as the fuel supply amount used for the first injection. Therefore, the shortage of the fuel supply amount, which is the difference from the fuel amount corresponding to the engine load detected after the first injection, that is, the compensation amount for one combustion stroke, is calculated from the crank angle at which the intake valve is closed. In the first injection, the second fuel supply timing is set before the start of the intake stroke after the first injection within the same combustion stroke so that the injection is completed by a certain time. , The total fuel supply amount based on the engine load at the first fuel supply timing is injected, and the engine load changes between the first injection and the second injection in the second injection. Fuel supply based on By compensating for the shortage of the supply amount, it is intended to improve drivability and fuel efficiency without deteriorating the performance in any of the steady state, the transient state, and the idle state. [Means for Solving the Problem] In order to achieve the above, the fuel injection control device for an internal combustion engine according to the present invention includes load detection means a for detecting the load of the engine,
Crank angle detecting means b for detecting the crank angle of the engine
And a first supply timing setting means c for setting the first fuel supply timing sufficiently advanced from the intake stroke for each combustion stroke based on the crank angle of the engine, and the engine load at the first fuel supply timing. Supply amount calculation means d for calculating the fuel supply amount used for the first injection based on
A fuel amount calculating means e for calculating a fuel amount corresponding to an engine load detected before the start of the intake stroke within the same combustion stroke as the first injection and after the first injection,
The difference between the fuel supply amount used for the first injection and the fuel amount is calculated, and the compensation amount calculation means f for calculating the difference as the compensation amount for one combustion stroke, and the compensation amount calculated by the compensation amount calculation means are inhaled. The second fuel supply timing is within the same combustion stroke as the first injection and delayed from the first injection so that the injection is completed by a certain time before the crank angle at which the valve is closed. While instructing the injection of the fuel supply amount at the first fuel supply timing and the second supply timing setting means g set before the start of the intake stroke, the compensation amount calculated by the compensation amount calculation means is equal to or more than a predetermined value. At this time, the supply command means h for instructing the injection of the compensation amount at the second fuel supply timing and the intake port are provided, and the fuel is injected into each cylinder via the intake valve based on the command of the supply command means. A jetting means i for It is provided. [Operation] In the present invention, the first fuel supply timing sufficiently advanced from the intake stroke for each fuel stroke and the intake stroke within the same combustion stroke as the fuel supply amount used for the first injection are not started. Therefore, the shortage of the fuel supply amount, which is the difference from the fuel amount corresponding to the engine load detected after the first injection, that is, the compensation amount of one fuel stroke, is fixed from the crank angle at which the intake valve is closed. In the same combustion stroke, the second fuel supply timing is set before the start of the intake stroke after the injection of the first time so that the injection is completed by the time before, and in the first injection, The entire fuel supply amount based on the engine load at the first fuel supply timing is injected, and the change in engine load between the first injection and the second injection is performed in the second injection. Fuel supply based on Insufficient supply will be compensated appropriately. Therefore, the drivability and the fuel economy are further improved in any of the steady state, the transient state, and the idle state. [Examples] Hereinafter, the present invention will be described with reference to the drawings. 2 to 8 are views showing an embodiment of the invention. First,
The configuration will be described. In FIG. 2, reference numeral 1 denotes an engine, intake air is supplied to each cylinder through an intake manifold 2, an intake manifold 3, and fuel is an injector (injection means) provided in each cylinder based on an injection signal Si. 4a ~
It is jetted by 4f. Then, the exhaust gas combusted in the cylinder is introduced into a catalytic converter (not shown) through an exhaust pipe 5, where the harmful components in the exhaust gas are purified and discharged in the catalytic converter. The flow rate Qa of the intake air is detected by an air flow meter (load detection means) 6 and controlled by a throttle valve 7 of the intake pipe 2. The opening Cv of the throttle valve 7 is detected by a throttle opening sensor 8, and the rotation speed N of the engine 1 is detected by a crank angle sensor (crank angle detecting means) 9. In addition to this, a starter switch, an idle switch, a water temperature sensor, an oxygen sensor, and the like are installed to detect the operating state of the engine. Outputs from the air flow meter 6, the throttle valve opening sensor 8 and various switches are input to the control unit 10, and the control unit 10 performs fuel injection control based on these sensor information. The control unit 10 has a function as a first and second supply timing setting means, a supply amount calculating means, a fuel amount calculating means, a compensation amount calculating means, and a supply commanding means, and the CPU 11, ROM 12, RAM 13, A / D.
It is composed of a converter 14 and an I / O port 15, which are connected to each other by a common bus 16. The A / D converter 14 converts Qa or the like input as an analog signal into a digital signal and outputs it to the CPU 11 or the RAM 13 at a designated time according to the instruction of the CPU 11. The CPU 11 fetches external data required according to the program written in the ROM 12, and exchanges data with the RAM 13 while performing arithmetic processing on the processing values necessary for fuel injection control, and if necessary. The processed data is output to I / O port 15. Signals from various sensors are input to the I / O port 15, and
The injection signal Si is output from the I / O port 15. ROM12 is CP
The calculation program in U11 is stored, and the RAM 13 stores data used for calculation in the form of a map or the like. Note that a part of the RAM 13 is composed of, for example, a non-volatile memory, and retains the stored contents (learning value and the like) even after the calculation is stopped. FIG. 3 is a block diagram showing the injector control circuit of the control unit 10. In FIG. 3, 21
Is an ANG (angle) register, and the injection start angle ADD1 is set in the ANG register 21. The counter 22 is reset by the 120 ° pulse of the crank angle sensor 9 and counts the 1 ° pulse of the crank angle sensor 9. Comparator 23 has ANG register 21 when counter 22 is reset
Read ADD1 set to
When the count value of counter 22 and the count value of counter 22 match
State. The output of the comparator 23 is output to the CPU 11 and gates 27a to 27f described later to generate a fuel injection interrupt for the CPU 11. Above, ANG register 21, counter 22
And the comparator 23 constitutes the injection start angle control circuit 24. On the other hand, 25a to 25f (only 25a and 25f are shown in the figure. The same applies to other members hereinafter) are EGI (fuel injection) registers, and injection pulse width ADD2 is set in the EGI registers 25a to 25f. It Further, the counters 26a to 26f are reset and count clock pulses when the input G of the gates 27a to 27f is ON and the output of the comparator 23 is turned from OFF to ON. Comparators 28a-28f are counters 26a-2
When 6f is reset, the power transistor 29a is read at the same time as the ADD2 set in the EGI registers 25a to 25f is read.
Turn ON ~ 29f, read ADD2 and counter 26a ~ 26f
When the count values of the power transistors 29a to 29f match
To the OFF state. Above EGI registers 25a-25f, counter
26a to 26f, gates 27a to 27f, comparators 28a to 28f and power transistors 29a to 29f are injection pulse width output circuits.
Make up thirty. It should be noted that the injection pulse width output circuit 30 corresponds to each cylinder from 1 to 6 cylinders, and there are 6 sets (in the case of 6 cylinders) each. Next, the operation will be described. FIG. 4 is a flowchart showing a fuel supply amount calculation program written in the ROM 12, and this program is executed once every predetermined period (for example, 10 ms). First,
The intake air amount Qa and engine speed N are read at P ₁ . The rotation speed N can be obtained by measuring the interval time of the reference signal (signal at every 360 °) from the crank angle sensor 9 or calculating the number of pulses of the position signal (signal at every 1 °) at a predetermined time. Next, in P ₂ , the basic injection amount Tp is calculated according to the following equation, and in P ₃ , this Tp is corrected based on the operating state such as the cooling water temperature and the effective injection pulse width Te is calculated. In addition,
The effective injection pulse width Te is the fuel per one rotation, and therefore the supply fuel amount required for one stroke and two rotations is twice this amount. However, with K: constant P ₄ , the fuel injection pulse width Ti corresponding to the total amount of the supplied fuel is calculated according to the following equation. Ti = Te × 2 + Ts ...... Here, the battery voltage correction Ts corrects the change in the effective valve opening time due to the fluctuation of the injector drive voltage (battery voltage), and is actually supplied within the injection pulse width Ti. Is the fuel amount of the effective injection pulse width Te × 2. Then, the first time injection continuation determination process performed in step P ₅ to P _7. That is, the angle θ that progresses during the first injection calculated in accordance with the following equation in P ₅ and the predetermined angle θ ₀ set with a certain allowance angle in the first and second injection intervals
Is compared to determine whether the first injection is continuing. When θ> θ ₀ , it is judged that the first injection is continuing, and the second injection prohibition flag FI is set at P ₆ (FI = 1)
I do. When θ <θ ₀ , it is determined that the first injection has already ended, and the flag FI is reset (FI = 0) at P ₇ . This second injection prohibition means that when the first injection pulse width is switched to the second injection pulse width during output,
The purpose is to prevent the fuel injection pulse width Ti from being supplied completely and accurately. In the present embodiment, at the time when the calculation of the first injection amount is performed, it is predicted whether or not the second injection start time comes during the first injection and the second injection is performed.
The configuration is such that the second injection is prohibited, but of course the invention is not limited to this, and the state of the injection valve output of the cylinder concerned can be changed to I / O port 15
It is also possible to adopt a configuration in which the second injection is prohibited by determining whether or not the injector is being driven at the time when the second injection is started by reading through. Next, at P ₈ , the fuel injection pulse width Ti ₁ output in the _first injection (corresponding to the fuel supply amount used in the first injection) and the current time, that is, before the intake stroke starts and the first injection Based on the difference between the fuel injection pulse width Ti (corresponding to the fuel amount) corresponding to the engine load detected later from, the shortage of the fuel supply amount between the first injection and the present time, that is, compensation Calculate the amount ΔTE. ΔTE = Ti−Ti ₁ …… In P ₉ , the compensation amount ΔTE is compared with a predetermined control value TEmin (predetermined value), and when ΔTE <TEmin or the compensation amount ΔTE is negative, the compensation amount ΔTE is set in P _10. = 0, the fuel supply amount is not compensated. On the other hand, when ΔTE ≧ TEmin, P ₁₁
Proceed to. In this way, in addition to the case where ΔTE becomes negative, the correction is not performed when the value is smaller than the predetermined limit value. This is because it has the opposite effect of improving the viscosity of the fuel ratio and prevents the fuel from being wasted. Then, at P ₁₁ , the battery voltage correction Ts is added to the compensation amount ΔTE to calculate the injection pulse width Ti ₂ of the _second injection, and at P ₁₂ the injection pulse width Ti is stored in the output register of the I / O port 15. At the specified crank angle
The injection signal Si having the fuel injection pulse width corresponding to is output to the injectors 4a to 4f, and the processing of this time is ended. The processing performed in this step will be described in detail later with reference to FIG. By the way, because injection is performed for each cylinder,
The injection times of the first and second injections are different for each cylinder. Therefore, the first injection pulse width Ti
_The memory for storing ₁ and the memory for storing the second injection pulse width Ti ₂ are provided so as to correspond to the respective number of cylinders, and the calculation of steps P _{8 to} P ₁₁ is performed for each cylinder. FIG. 5 is a flow chart showing a program for setting the fuel supply timing, and this program is executed every reference signal of each cylinder (120 ° in the case of 6 cylinders). First, counting the reference signal at P _21, to determine the position of every 120 ° of crank angle sensor 9. Then, set the second fuel injection start timing INJANG at P _22. This fuel injection start timing is
Before the start of the intake stroke within the same fuel stroke, the compensation amount ΔTE for one combustion stroke, which is calculated based on the engine load detected after the first injection, is calculated based on the engine speed N and the fuel injection pulse width. It is set so that the injection is finished within a certain time from the crank angle at which the intake valve is closed according to Ti, and the injected fuel can enter the cylinder before the intake valve is closed. The fixed time shown in FIG. 8 is determined in consideration of the time required for the fuel to reach the intake valve from the injection valve and the increase in ΔTe, and the fuel injection start timing INJANG is 2 In the digit data, the upper digit is the 120th place and the lower digit is the 1 ° place. P ₂₃ 120 crank angle position and INJANG detected by P ₂₁ in
° by comparing the digit calculating a cylinder number INJ2 as the second round of injection timing within 120 °, Zansuru the cylinder number INJ1 to be the first injection timing at P _24. Note that hit the calculating a cylinder number INJ1, a cylinder number which is delayed three cylinders than INJ2 based on INJ2 calculated in P ₂₃ in this embodiment INJ1
Although the first injection is performed at the timing of advancing 360 ° with respect to the cylinder of INJ1, it may be set at any timing. Then, at P ₂₅ INJAN
1 ° digit data of G is set to ANG register 21 of the I / O port 15, and turns ON the gate G corresponding to the cylinders in the P ₂₆ INJ1 to set the injection timing. In P ₂₇ , it is determined whether or not the flag FI is set (FI = 1) in the first injection continuation determination process (P _{5 to} P ₇ ) described above with reference to FIG. 4, and the flag is set.
When FI is not set (FI = 0), it is determined that the second injection may be performed, and the second injection gate corresponding to the cylinder of INJ2 is set at P ₂₈ . Meanwhile, when the flag FI is set (FI = 1) is directly proceeds to P _12,
The second injection is prohibited without setting the gate of the second cylinder. Then, at P ₁₂ , the injection pulse width is set in the I / O port 15 as described above with reference to FIG. FIG. 6 is a subroutine showing a program for setting the injection pulse width, and this process corresponds to step P ₁₂ shown in FIGS. 4 and 5. This program is executed by both the time interruption shown in FIG. 4 and the crank angle interruption shown in FIG. First, set the fuel injection pulse width Ti in the EGI register of the I / O port 15 corresponding to the cylinder of INJ1 which is the timing of the first injection at P ₃₁ , and set the second injection timing at P ₃₂ . Then, the second injection pulse width Ti ₂ is set in the EGI1 register corresponding to the cylinder INJ2. The injection pulse width set in the EGI register of the I / O port 15 is triggered when the crank angle reaches the injection start timing set in the ANG register, and the injectors 4a to 4f
Drive. FIG. 7 is a flow chart showing a program for storing the fuel injection pulse width Ti ₁ , and this program is executed every time the EGI register is triggered. First, on page ₄₁ , first
The fuel injection pulse width Ti is stored in the _first injection pulse width memory Ti ₁ corresponding to the cylinder of INJ1 which is the first injection, and the process ends. Thus, in this embodiment, FIG. 8 (b)
As shown in Fig. 2, the second injection and the first injection of the cylinder delayed by three cylinders (360 °) with the intake valve open period (hatched part in the figure) sandwiched between the fuel per pair of combustion cycles. It is set as the supply amount, and the total amount Te ₁ × 2 of the fuel supply amount is injected in the first injection, and the first injection and the second injection are performed.
The shortage of the fuel supply amount based on the change in the engine load between the second injection and the second injection is compensated as ΔTE. Therefore, as shown in FIG. 7A, the total amount of fuel supplied by the two injections is Te ₁ × 2 + ΔTe = Te ₂ × 2, and it is possible to appropriately supply the required fuel that follows the change in load. . As a result, good drivability and fuel economy can be achieved regardless of whether the operation is steady or transient.
In addition, since the entire amount is injected in the first time even during idling, the responsiveness can be improved as compared with the case where fuel injection is simply performed a plurality of times, and the control accuracy can be further improved. In the present embodiment, the present invention is applied to a 6-cylinder engine, but it is needless to say that the present invention is not limited to this and can be applied to an engine having another number of cylinders, for example, a 4-cylinder engine. EFFECTS OF THE INVENTION According to the present invention, the first fuel supply timing sufficiently advanced from the intake stroke for each combustion stroke, and the intake stroke within the same fuel stroke as the fuel supply amount used for the first injection. The intake valve closes the shortage of the fuel supply amount, which is the difference between the start circle and the fuel amount corresponding to the engine load detected after the first injection, that is, the compensation amount for one fuel stroke. The second fuel supply timing is set before the start of the intake stroke within the same combustion stroke and after the first injection so that the injection is finished by a certain time before the crank angle. Injection of the entire fuel supply amount based on the engine load at the first fuel supply timing, and the second injection of the engine between the first injection and the second injection. Based on load changes Since the shortage of fuel supply is compensated for,
It is possible to improve drivability and fuel efficiency without degrading performance in both the transient state and the idle state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 8 are diagrams showing an embodiment of the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. FIG. 4 is a block diagram showing the injector control circuit, FIG. 4 is a flow chart showing a program for calculating the fuel supply amount, FIG. 5 is a flow chart showing a program for setting the fuel supply timing, and FIG. 6 is setting the injection pulse width. FIG. 7 is a flow chart showing a program for storing the fuel injection pulse width, FIG. 7 is a flow chart showing a program for storing the fuel injection pulse width, and FIG. 8 is a timing chart for explaining its operation. 1 ... Engine, 6 ... Air flow meter (load detection means), 9 ... Crank angle sensor (crank angle detection means), 10 ... Control unit (first and second supply timing setting means, supply amount calculation means) , Fuel amount calculation means, compensation amount calculation means, supply command means).

Claims (1)

(57) [Claims] a) load detecting means for detecting the load of the engine, b) crank angle detecting means for detecting the crank angle of the engine, and c) the first time sufficiently advanced from the intake stroke for each combustion stroke based on the crank angle of the engine. First supply timing setting means for setting the fuel supply timing of d, and d) supply amount calculating means for calculating the fuel supply amount used for the first injection based on the engine load at the first fuel supply timing. E) fuel amount calculation means for calculating a fuel amount corresponding to an engine load detected before the start of the intake stroke within the same combustion stroke as the first injection and after the first injection, f) Compensation amount calculation means for calculating a difference between the fuel supply amount used for the first injection and the fuel amount, and the difference being the compensation amount for one combustion stroke; and g) the compensation calculated by the compensation amount calculation means. Amount of intake air The second fuel supply timing is within the same fuel stroke as the first injection and delayed from the first injection so that the injection is completed by a certain time before the crank angle at which the valve is closed. Second supply timing setting means set before the start of the intake stroke, and h) commanding the injection of the fuel supply amount at the first fuel supply timing, while the compensation amount calculated by the compensation amount calculating means is predetermined. Supply command means for instructing injection of the compensation amount at the second fuel supply timing when the value is greater than or equal to the value, and i) provided in the intake port, and based on the command of the supply command means, to each cylinder via the intake valve. A fuel injection control device for an internal combustion engine, comprising: an injection unit that injects fuel.