JPH0520577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electronically controlled fuel injection device mounted on a vehicle such as an automobile.

[Prior Art] Conventionally, an electronically controlled fuel injection device for injecting fuel into a multi-cylinder internal combustion engine at every predetermined rotational position of the engine crankshaft has been disclosed in Japanese Unexamined Patent Application Publication No. 1983-1999.
As shown in Publication No. 75543, fuel is injected in a high-speed injection mode with a short injection interval in which fuel is injected once per engine revolution in order to improve the responsiveness of the engine during engine transients, such as acceleration. Check whether the injection pulse width corresponding to the basic fuel injection amount obtained by dividing the air amount by the engine speed is less than the set value corresponding to the lower limit value that can guarantee the linearity of the electromagnetic injector. If the injection pulse width is determined to be below the set value, the fuel injection that was previously performed in high-speed injection mode will be changed to low-speed injection with a long injection interval, such as once every two engine revolutions. Fuel injection is performed in injection mode, and the injection pulse width is set to a size that can sufficiently guarantee the linearity of the electromagnetic injection valve.

However, with this type of electronically controlled fuel injection system, when switching from low-speed injection mode to high-speed injection mode, the air-fuel ratio continues to deviate toward the lean side for a relatively long time, causing the engine to misfire and drivability to deteriorate. It was easy to invite.

[Object of the Invention] In view of the above, the present invention has been made to suppress the duration of the air-fuel ratio lean state that occurs when switching the injection mode as described above to a sufficiently short period of time, and to prevent engine misfires and deterioration of drivability. The purpose of the present invention is to provide an electronically controlled fuel injection device.

[Configuration of the Invention] Therefore, as shown in FIG. 1, the electronically controlled fuel injection device of the present invention is an electronically controlled fuel injection device that performs fuel injection by switching between a plurality of synchronous injection modes according to changes in the operating state of the internal combustion engine A. The fuel injection device includes: a calculation means C that calculates the pulse width of an injection pulse applied to the electromagnetic injection valve B at every predetermined calculation cycle; and a calculation means C that corresponds to the calculated pulse width at the same cycle as the calculation cycle. A first synchronous injection mode that outputs an injection pulse, and a second synchronous injection mode that outputs an injection pulse in which the calculated pulse width is corrected according to the relationship between the calculation period and the injection period at a period longer than the calculation period.
An injection pulse output means D for switching the synchronous injection mode of the internal combustion engine A according to the operating state;
When transitions to the acceleration state, the mode transitions to the first synchronous injection mode, and when no injection pulse is output at the pulse width calculation timing immediately before the transition, the pulse width calculated by the calculation means C and outputting an injection pulse having a pulse width N times (N>1) at a synchronous injection timing immediately after the above condition is satisfied.

An example of the basic operation according to the present invention is, as shown in FIG. 2, in which the basic injection pulse width is adjusted according to the operating state of the engine at an injection interval of 360 mm in an injection mode in which fuel is injected once per engine revolution. Calculate for each °CA,
This calculated injection pulse width is doubled and necessary corrections are made to output an injection pulse with this final injection pulse width to the electromagnetic injection valve every 720°CA. Then, when an acceleration operation such as depressing the accelerator pedal is performed, the injection pulse _p1 is output at time b, which is before time a when this acceleration is detected and corresponds to the calculation timing closest to the time a. If not, double the basic injection pulse width found at the calculation timing corresponding to the acceleration detection time point a, as in the case of the low-speed injection mode as described above, and add any necessary corrections to obtain the final value. An injection pulse _P2 having a width of injection pulse is outputted.

[Example] The present invention will be described below by giving examples and referring to the drawings.

3 and 4 show an embodiment in which the present invention is applied to an internal combustion engine (engine) with simultaneous injection in all cylinders. FIG. 3 is a schematic system diagram of the engine and its surroundings, and FIG. 1 is a block diagram mainly showing the internal configuration of a fuel injection control circuit.

In Fig. 3, 2 is a known four-stroke spark ignition engine installed in a car, 4 is an electromagnetic injection valve, 6 is an air cleaner that filters air taken into the engine, 8 is an intake pipe, and 10 is a cylinder. Throttle valve that controls the amount of intake air drawn into the
11 is a spark plug, 12 is an exhaust manifold, 1
4 is an exhaust pipe. Incidentally, fuel is supplied from a fuel system (not shown) to electromagnetic injection valves 4 provided corresponding to each cylinder.
The combustion air is supplied through the air cleaner 6, the intake pipe 8, and the throttle valve 10. After combustion, the exhaust gas is discharged into the atmosphere through the exhaust manifold 12, the exhaust pipe 14, a catalytic converter (not shown), and the like.

16 is a potentiometer-type intake air flow sensor, 18 is a thermistor-type intake air temperature sensor, 20 is a thermistor-type water temperature sensor, 22 is a rotation sensor,
24 is a fuel injection control circuit, 26 is a starter switch, 27 is a throttle opening sensor that detects the opening of the throttle valve 10, 28 is a battery, and 30 is a key switch.

The intake air amount sensor 16 detects the amount of intake air taken into the engine 2 and outputs an analog voltage (analog detection signal) corresponding to the amount of intake air.
Further, the intake temperature sensor 18 detects the temperature of the air taken into the engine 2 and outputs an analog voltage (analog detection signal) corresponding to the intake temperature. Note that the intake air amount sensor 16 and the intake air temperature sensor 18 are installed in the intake pipe 8.

The water temperature sensor 20 detects the coolant temperature and outputs an analog voltage (analog detection signal) corresponding to the coolant temperature, and the water temperature sensor 20 is installed in the engine 2.

The rotation sensor 22 detects a predetermined rotation angle position of the engine crankshaft and outputs a pulse signal with a frequency proportional to the rotation speed. For example, an ignition coil of an ignition device may be used as the rotation sensor 22, and an ignition pulse signal from a primary terminal of the ignition coil may be used as the rotation speed signal.
Alternatively, it may be one that converts changes in magnetic flux into electrical signals using electromagnetic pickup.

Furthermore, the fuel injection control circuit 24 basically calculates the basic fuel injection amount (basic injection pulse width) based on the detection signals of the intake air amount sensor 16 and the rotation sensor 22, and calculates the basic fuel injection amount (basic injection pulse width). The final injection pulse width is determined by correcting the basic fuel injection amount using the signals from the intake air temperature sensor 18 and water temperature sensor 20, and the opening time of the electromagnetic injection valve 4 is thereby controlled. The details will be described later.

Next, the fuel injection control circuit 24 will be explained based on FIG.

In the figure, 100 is a microprocessor (CPU) that calculates the fuel injection amount (injection pulse width), etc. Further, 101 is a rotation number counter, 102 is an interrupt control unit, and 150 is a common bus. In the rotation number counter 101, the number of rotations of the crankshaft is counted based on the signal from the aforementioned rotation sensor 22, and when the measurement is completed, an interrupt command signal is supplied to the interrupt control section. The interrupt control unit 102 generates an interrupt signal based on the signal, and sends it via the common bus 150.
The interrupt processing routine is input to the CPU 100 and executed by the CPU 100 for calculating the fuel injection amount.

Further, 103 is a digital input port, and a digital signal from a starter switch 26 for turning on and off a starter (not shown) is inputted to the CPU 100 from the digital input port 103.

Next, 104 is an analog multiplexer and an A/D
An analog input port consisting of a converter,
The aforementioned intake air amount sensor 16, intake temperature sensor 18,
Each signal from the water temperature sensor 20 and throttle opening sensor 27 is A/D converted, and the signals are sequentially
Loaded into the CPU 100.

As described above, the output information of the rotation number counter 101, the interrupt control unit 102, the digital input port 103, and the analog input port 104 is transmitted to the common bus 15.
0 to the CPU 100.

Furthermore, 105 and 106 are power supply circuits, 107
is RAM, and 108 is ROM. Power supply circuit 10
5 is directly connected to the battery without passing through the key switch 30, so the RAM 107, which is supplied with power from this power supply circuit 105, is connected directly to the battery without passing through the key switch 30.
Power is always applied regardless of the On the other hand, the power supply circuit 106 is connected to the battery 28 through the key switch 30, and supplies power to everything other than the RAM 107 from this power supply circuit 106.
The RAM 107 is a temporary storage unit that is used temporarily during operation, but as mentioned above, the RAM 107 is a temporary storage unit that is used temporarily during operation.
Power is always applied regardless of 0, and the memory contents are not lost even if the key switch 30 is turned off and engine operation is stopped, thus forming a non-volatile memory. The ROM 108 is a read-only memory that stores programs, various constants, and the like.

Further, 109 is a down counter, 110 is a power amplifying section, and 111 is a timer. The down counter 109 is a fuel injection time control counter including a register, and the digital signal representing the valve opening time of the electromagnetic injection valve 4 calculated by the CPU 100, that is, the fuel injection amount, corresponds to the actual valve opening time of the electromagnetic injection valve 4. It is converted into a pulse signal with the given pulse width. The power amplifier 110 amplifies the power necessary to drive the electromagnetic injection valve 4. Furthermore, the timer 111 constantly measures the elapsed time and transmits it to the CPU 100, where it is used to detect, for example, the number of rotations N.

Next, based on the flowchart in Figure 5, the CPU
The control program processed by 100 will be described as well as the operation of the entire arrangement.

Key switch 30 and starter switch 26
When the is turned on and the engine is started, arithmetic processing is started in the main routine 200, and step 201 is started.
Initialization processing is performed.

Next, in step 202, the analog input port 10 is
The values corresponding to the cooling water temperature and intake air temperature from step 4 are read, and in the following step 203, a correction amount K is calculated from the values, and the calculation result is stored in the RAM 107. Note that the correction amount K is the correction amount according to the intake air temperature, which can be obtained by searching a map or calculating.
This is the overall correction amount calculated based on K ₁ and the correction amount K ₂ depending on the cooling water temperature.

Normally, the main routine processing from step 202 to step 203 is executed repeatedly according to the control program, and an interrupt signal for fuel injection amount calculation (a signal generated every 360° CA) from the interrupt control unit 102 is input. Then, the microprocessor 100
Even if the main routine is in progress, it immediately interrupts the processing and moves to the interrupt handling routine shown at 210.

In step 211, a signal representing the rotation speed N of the crankshaft is measured from the rotation speed counter 101, and in the following step 212, the signal of the intake air amount sensor 16 is taken in from the analog input port 104, and the intake air amount Q is measured.
Measure.

Next, in step 213, the basic injection amount (that is, the basic injection pulse width t for the electromagnetic injection valve 4) determined from the rotational speed N and the intake air amount Q is determined by the following equation.

t=F×Q/N [msec] (F: constant) In the following step 214, the correction amount K obtained in step 203 of the main routine is read out from the RAM 107, and the fuel injection amount for the engine to operate in the optimum condition is determined. Correction calculation is performed using the following equation.

T=t×K [msec] Here, T is the amount of fuel injected during one rotation of the engine that is optimal for the operating condition of the engine, with respect to the basic injection pulse width t determined in step 213. This is the injection pulse width that takes a value.

Next, in step 215, the acceleration state is detected,
It is determined whether or not the vehicle is currently in an acceleration state, but the method for detecting the acceleration state will be described later.

If it is determined in step 215 that the engine is not in an acceleration state, the process proceeds to step 216, where the corrected injection pulse width T is doubled to obtain the final injection pulse width τ. Next, in step 217, it is determined whether the crankshaft has rotated twice, that is, whether 720° CA has elapsed.
If 720°CA has not elapsed, the process moves to step 218, and the interrupted process of the main routine 200 is restarted. On the other hand, 720°CA at step 217
If it is determined that the time has elapsed, then in step 219,
The final injection pulse width τ already determined in step 216 is set in the down counter 109, and the process proceeds to step 218.

On the other hand, if it is determined in step 215 that the engine is in an acceleration state, then in step 220 it is determined whether or not injection was performed previously, that is, before one revolution of the crankshaft (before 360° CA). When the engine is first detected to be accelerating, the previous fuel injection must have occurred either one crankshaft revolution ago (before 360° CA) or two revolutions before the crankshaft (before 720° CA). Therefore, the judgment result of step 220 can be either "YES" or "NO," but if injection was performed before 360° CA, the next step is
At step 219, the corrected injection pulse width T already determined at step 214 is counted down by the down counter 109.
720° CA and proceed to step 218.
If injection was performed before, then in step 221 the corrected injection pulse width T is doubled to obtain the final injection pulse width τ, and then in step 221
At step 219, this final injection pulse width τ is set in the down counter 219, and the process proceeds to step 218. Then, in the next interrupt processing, the step
While it continues to be determined in step 215 that the engine is in an accelerating state, the determination result in step 220 is always "YES" because injection is performed before 360° CA, and the corrected injection pulse width T Counter 1 is down as it is without being doubled.
09.

In this way, in the interrupt processing routine,
() When the engine is in an operating state other than an acceleration state, the injection pulse width T after correction is counted as the final injection pulse width by the down counter 109 every 720° CA.
A pulse with a pulse width T is applied to the electromagnetic injection valve 4, and () Immediately after the engine shifts from this operating state to an acceleration state, the down counter 109 is set depending on the presence or absence of injection before 360° CA. If the injection pulse width to be performed is different and the injection occurs before 360° CA, the corrected injection pulse width T is set in the down counter 109 as the final injection pulse width, but if the injection occurs before 360° CA. If there is no injection pulse width T, the value obtained by doubling the injection pulse width T after correction is set in the down counter 109 as the final injection pulse width, and () while the engine is in the acceleration state,
The injection pulse width T after correction is set in the down counter 109 as the final injection pulse width every 360° CA.

Next, the method for detecting the acceleration state in step 215 will be explained with reference to FIGS. 6 and 7.

The method of detecting the acceleration state shown in FIG. 6 is as follows.

In step 301, which is processed after the process shown in step 214 in FIG. 5 is performed, the rotation speed N read in step 211 is compared with a preset rotation speed N ₁ (for example, 3000 rpm). If the rotational speed N is greater than or equal to the set rotational speed _N1 , the process moves to point 42, where injection is performed every 720° CA, that is, low-speed injection as described above. On the other hand, the rotation speed N is the set rotation speed N ₁
If it is less than
At step ₃₀₂ , _the basic injection pulse width t obtained at step 213 shown in FIG. ) or more, the process moves to point 40 and injection every 360°CA, that is, high-speed injection, is performed as described above. Otherwise, the point
42 and low-speed injection is performed.

In this way, the acceleration detection shown in Fig. 6 determines that the engine is in an accelerating state when the rotational speed N is less than or equal to the set rotational speed _N1 and the basic injection pulse width t is larger than the set pulse width _t1 . It's a method.

Further, detection of the acceleration state shown in FIG. 7 is performed as follows.

First, in step 401, the steps shown in FIG.
Similarly to 301, the rotational speed N is compared with the set rotational speed _N1 , and if the rotational speed N is greater than or equal to the set rotational speed _N1 , the process moves to point 42 and low-speed injection is performed. On the other hand, if the rotational speed N is less than the set rotational speed _N1 , the process advances to step 402, and in this step 402, the intake air amount Q read in step 212 of FIG.
Previous) Calculate the intake air amount change rate ΔQ obtained from the read intake air amount Q, and calculate the intake air amount change rate ΔQ and the preset change rate ΔQ ₁ (for example, 2 cm ³ /msec)
are compared, and the intake air amount change rate ΔQ is the set change rate ΔQ ₁
If it is larger than , the process moves to point 40 and high-speed injection is performed; otherwise, the process moves to point 42 and low-speed injection is performed.

In this manner, the acceleration detection shown in FIG. 7 determines that the engine is in an accelerated state when the rotational speed N is less than the set rotational speed _N1 and the intake air amount change rate ΔQ is greater than the set change rate _ΔQ1 .

Next, the functions and effects of the above embodiment will be explained based on FIG. 8. In the same figure, T ₁ to T ₆ are
The calculation timing is every 360°CA synchronized with the rotation of the crankshaft, and since no acceleration is detected during calculation timings _T1 to _T4 , fuel injection is performed every 720°CA, that is, low-speed injection once every 2 revolutions. The acceleration state is detected for the first time at calculation timing _T5 , and the injection is immediately switched to high-speed injection every 360° CA. At this time, since fuel injection is not performed as shown in the figure at the output timing corresponding to the previous calculation timing _T4 of the calculation timing _T5 , the corrected injection is performed as described above in the flowchart of FIG. A process of doubling the pulse width T is executed, and a pulse having a pulse width τ ₃ as shown by the broken line in FIG. 5 is applied to the electromagnetic injection valve 4. Therefore, if the process of doubling the injection pulse width as described above is not executed, the applied pulse width of the electromagnetic injection valve 4 corresponding to the calculation timing _T5 is small as shown by the solid line in the figure, so the engine's While the lean state of the air-fuel ratio (A/F) that occurs at the same time as the transition to the actual acceleration state begins lasts for a relatively long time as shown by the solid line in the figure, according to this embodiment, this lean period lasts for a relatively long time. As shown by the broken line, the time is short, and as a result, the probability of engine misfire is reduced and drivability is improved.

In the above embodiment, the acceleration state is used as the criterion for switching the injection mode, but it is also possible to perform high-speed injection only when the engine is started, or to perform high-speed injection only when the engine is not idling. .

[Effects of the Invention] As explained above, the present invention has the second injection mode.
When switching from the first synchronous injection mode (low-speed injection mode) to the first synchronous injection mode (high-speed injection mode), the first injection pulse immediately after the conditions for this switch are satisfied, the high-speed injection mode Since the pulse width of this injection pulse is increased when no previous injection was performed in the injection cycle, the duration of the air-fuel ratio lean state that occurs when switching modes can be sufficiently shortened.
This makes it possible to prevent engine misfires and improve drivability.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram for clearly demonstrating the present invention, Figure 2
The figure is an explanatory diagram for explaining the operation of the present invention.
4 is a block diagram mainly showing the internal structure of the control circuit, FIG. 5 is a flowchart showing the control program, and FIGS. 6 and 7 are The specific flowchart of step 215 in FIG.
The figure shows a timing chart showing the operation of this embodiment. A... Internal combustion engine, B... Electromagnetic injection valve, C... Calculating means, D... Output means.

Claims (1)

[Scope of Claims] 1. An electronically controlled fuel injection device that performs fuel injection by switching between a plurality of synchronous injection modes according to changes in the operating state of an internal combustion engine, which controls the pulse width of an injection pulse applied to an electromagnetic injection valve. a first synchronous injection mode that outputs an injection pulse corresponding to the calculated pulse width in the same period as the calculation period; A second device that outputs an injection pulse obtained by correcting the calculated pulse width according to the relationship between the calculation period and the injection period.
The injection pulse output means switches between the first synchronous injection mode and the first synchronous injection mode according to the operating state, and when the internal combustion engine shifts to an acceleration state, the first synchronous injection mode shifts to the first synchronous injection mode, and the pulse width calculation timing immediately before the shift occurs. When no injection pulse is output at the time, an injection pulse having a pulse width N times the pulse width calculated by the calculation means (where N>1) is output at the synchronous injection timing immediately after the above condition is satisfied. An electronically controlled fuel injection device comprising: