JPH048282Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a fuel injection control device, and more particularly, to a fuel injection control device that performs asynchronous injection in addition to synchronous injection for each cylinder group when a fuel cut is released.

(Prior art) In general, in the group fuel injection method, which is one of the fuel injection methods for multi-cylinder engines, the group fuel injection method is used to There is a method that uses synchronous injection timing, and this method has excellent torque generation responsiveness because the injected fuel is quickly taken into the cylinder.

For example, a fuel injection control device that performs such synchronous injection and cuts off the supply of fuel to the engine in a predetermined operating state, so-called fuel cut, can be found in the following materials: )” (June 1988, published by Nissan Motor Co., Ltd.) is known.

This conventional fuel injection control device can be shown as shown in FIG. In FIG. 6, 1 is a crank angle sensor that detects the rotation angle of the crankshaft of a 6-cylinder engine.
outputs a 120° signal with a predetermined pulse width every 120° of crank angle, and a 720° signal with a wider pulse width than the 120° signal every 720° of crank angle. Occurs at 70° before the point.) is output. 2 is an air flow meter that detects the flow rate (intake amount) of intake air of the engine, and 3 is a rotation speed sensor that detects the rotation speed N of the engine. 4 is a throttle switch that detects the fully closed state of a throttle valve provided in the intake passage of the engine, and 5 is a control unit. The control unit 5 includes a CPU 6, memory 7 and I/
The I/O port 8 includes the crank angle sensor 1, air flow meter 2, rotation speed sensor 3, and throttle switch 4.
Each signal from is input. In addition, an injection signal is output from the I/O port 8 to power transistors 9 and 10, and the collector of the power transistor 9 is connected to the intake passages of the first cylinder #1, second cylinder #2, and third cylinder #3 of the engine. The fuel injection valves 11, 12, and 13 provided respectively are commonly connected,
Fuel injection valves 14, 15, and 16 provided in the intake passages of the fourth cylinder #4, fifth cylinder #5, and sixth cylinder #6 of the engine are commonly connected to the collector of the power transistor 10, respectively. Also,
Each of these fuel injection valves 11 to 16 has a battery 17.
A predetermined voltage is supplied.

In this fuel injection control device, the fuel injection valves 11 to 16 are connected to a first group that supplies fuel to a first cylinder #1, a second cylinder #2, and a third cylinder #3, a fourth cylinder #4, and a fifth cylinder. #5 and a second group that supplies fuel to the sixth cylinder #6, and fuel is injected into each group in synchronization with a predetermined crank angle. That is, by outputting an injection signal to the power transistor 9 at a predetermined crank angle, the fuel injection valves 11, 12, 1
3 are driven at the same time, and fuel is simultaneously injected into the intake passages of the first cylinder #1 and the third cylinder #3. Then, by outputting an injection signal to the power transistor 10 at a predetermined crank angle, the fuel injection valves 14, 15, and 16 are simultaneously driven and the fourth
Fuel is simultaneously injected into the intake passages of cylinder #4 to sixth cylinder #6. Therefore, each cylinder has the seventh
As shown in the figure, fuel is injected simultaneously for each group at crank timings indicated by diagonal lines A, B, and C.

Further, in this fuel injection control device, the engine rotation speed N is the first fuel cut rotation speed shown in FIG.
When the temperature is higher than N ₁ (N≧N ₁ ) and the throttle switch is ON (throttle valve is fully closed),
and the engine rotation speed N is the second value shown in FIG.
The fuel cut rotation speed is higher than N ₂ (N≧N ₂ ),
When the throttle switch switches from OFF to ON (when the throttle valve switches to fully closed), the output of the injection signal to the power transistors 9 and 10 is stopped, and the supply of fuel to the engine is stopped. Shut off and perform what is called a fuel cut. In FIG. 7, the fuel cut state is shown before the injection timing indicated by the diagonal line A.

Then, during fuel cut, the engine speed N
decreases below the recovery rotation speed Nr shown in Figure 8 (N
<Nr) or when the throttle switch is turned OFF (acceleration operation), the fuel cut is released and an injection signal is output at the normal crank timing of synchronous injection, for example at the injection timing indicated by diagonal line A in Fig. 7. Fuel supply will be resumed.

(Problem to be solved by the invention) However, in such a conventional fuel injection control device, when an acceleration operation is performed during fuel cut, the fuel cut is released and fuel supply is restarted, but the Because the injection timing for re-injection was set to the crank timing for normal synchronous injection, it may take a long time after an acceleration operation is performed until fuel is injected and output torque is obtained, resulting in poor acceleration response. There was a risk that it would decline. Additionally, during this time, the engine speed may become too low, causing the engine to stall or large torque fluctuations to occur.

(Purpose of the invention) Therefore, the present invention performs asynchronous injection at the time of fuel cut recovery and limits the target period of the asynchronous injection to a predetermined period, thereby improving the recovery response and reducing the overbalance of the air-fuel ratio. The purpose is to prevent the emission from worsening.

(Means for Solving the Problems) The fuel injection control device of the present invention, as its overall configuration diagram is shown in FIG. 1, includes: (a) a fuel injection valve that supplies fuel to each cylinder of a multi-cylinder engine; b) an operating state detection means for detecting the operating state; c) an injection amount calculation means for calculating the amount of fuel to be injected based on the operating state; d) for dividing the fuel injection valves into cylinder groups, an injection signal output means for outputting a synchronous fuel injection signal to the cylinder group immediately before the intake stroke of the preceding cylinder enters the intake stroke; e. stopping output of the synchronous fuel injection signal in a predetermined deceleration operating state; a fuel cut means for cutting off the supply of fuel to the engine; If it is within the period, an asynchronous fuel injection signal is output to the cylinder group to which the period including the acceleration operation timing belongs, while if the acceleration operation timing is outside the period, the asynchronous fuel injection signal is output to any cylinder group. The present invention is characterized by comprising: asynchronous injection control means that does not output an injection signal.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 2 to FIG. 5 are diagrams showing an embodiment of the present invention.
This invention is applied to a fuel injection control device that classifies three fuel injection valves into two groups and performs synchronous injection for each group.

First, to explain the configuration, in Fig. 2, 2
1 is a six-cylinder engine, and intake air is supplied to each cylinder #1 to #6 of the engine 21 through an intake pipe 22. The intake pipe 22 includes fuel injection valves 23, 24, 25, which inject fuel for each cylinder #1 to #6.
26, 27, and 28 are attached, and the flow rate (intake amount) of intake air supplied to the engine 21 is controlled by the throttle valve 2 provided at the gathering part of the intake pipe 23.
9. The throttle valve 29 is linked with the accelerator pedal of the vehicle.
The fully closed state of No. 9 is detected by the throttle switch 30. Further, the rotation of the crankshaft of the engine 21 is detected by a crank angle sensor 31, and the crank angle sensor 31 is attached to the crankshaft of the engine 21 and has a protrusion on its outer periphery. It has a magnetic deck 31b for detecting. The crank angle sensor 31 receives a 1° signal indicating the rotational speed N and angle of the engine 21, and a 120° signal generated every 120° at 70° before the piston top dead center of each cylinder #1 to #6. At the same time, the first cylinder #1 of the 120° signal
In order to indicate that it is a 120° signal, a 720° signal with a wider pulse width than the 120° signal (pulse width of 10° or more) is output every 720°. Also, engine 21
The temperature of the cooling water is detected by a water temperature sensor 32. Various sensors such as the throttle switch 30, crank angle sensor 31, water temperature sensor 32, and air flow meter (not shown) (which detects the amount of intake air) collectively constitute a driving state detection means 33 that detects the driving state of the vehicle. .

34 is an injection amount calculation means, an injection signal output means,
Fuel cut means, fuel cut release means,
This is a control unit that has a function as an asynchronous injection control means, and the control unit 3
4 is composed of a CPU 35, ROM 36, RAM 37, and I/O port 38. CPU
35 takes in necessary external data from the I/O port 38 according to the program written in the ROM 36, performs arithmetic processing while exchanging data with the RAM 37, and performs arithmetic processing as necessary. The processed data is output to the I/O port 38. The ROM 36 stores a program for controlling the CPU 35, and the RAM 37 is made up of, for example, a non-volatile memory and stores data used in calculations in the form of a map, etc., and retains the stored contents even after the engine 21 is stopped. . I/O
Signals from the throttle switch 30, crank angle sensor 31, water temperature sensor 32, air flow meter, etc. are input to the port 38, and analog input signals are converted into digital signals. Also,
From the I/O port 38, the first cylinder #1 to the third cylinder
The injection signal _S1 is simultaneously output to the fuel injection valves 23, 24, and 25 for the cylinder #3, and the injection signal is simultaneously output to the fuel injection valves 26, 27, and 28 for the fourth cylinder #4 to the sixth cylinder #6. Output S ₂ . That is, the fuel injection valves 23 to 28 are a group (first group) of fuel injection valves 23, 24, and 25 for the first cylinder #1 to the third cylinder #3, and a group (first group) of the fuel injection valves 23, 24, and 25 for the first cylinder #1 to the third cylinder #3, and a group (first group) of the fuel injection valves 23, 24, and 25 for the first cylinder #1 to the third cylinder #3, It is classified into two groups: a group of fuel injection valves 26, 27, and 28 for 6 (second group),
Injection signals S ₁ and S ₂ are input to each group in synchronization with a predetermined crank angle.

Next, the action will be explained.

In the case of this embodiment, the fuel injection valves 23 to 26 are
The injection signals S ₁ and S ₂ are output for each group in synchronization with a predetermined crank angle. ₁ and _S2 , that is, the function of the injection signal output means is performed by an interrupt program shown in FIG.

The interrupt program will be explained based on FIG. In addition, in FIG. 3, P ₁ to P ₁₁ indicate each step of the flow. Step P ₁ , 120°
It is determined whether the signal is ON or not, and if the 120° signal is ON, the control unit ₃ is
1 is added to the count value C ₁ of the first counter built in 4. This first counter counts every time a 120° signal is input, and is a counter that selects a group of fuel injection valves 23 to 28 to inject fuel and determines the injection timing, as will be described later. In step _P3 , it is determined whether the count value _C1 is 6 or not, and _C1 =
6, the count value C ₁ of the first counter is reset to 0 in step P ₄ and the process proceeds to step P _5. If C ₁ ≠ 6, the process directly proceeds to step P ₅ . That is, in the case of this embodiment, since the target is the 6-cylinder engine 21, when the count value _C1 reaches 6, it is reset to 0 and the count value _C1 is set to the first cylinder #1 when the next program is executed. I am trying to display it. In step _P5 , it is determined whether the count value C ₁ is 3 or not, and when C ₁ = 3,
In step _P3 , the injection signal _S1 is output to the first group of fuel injection valves 23, 24, and 25. Therefore, fuel is injected from the fuel injection valves 23, 24, and 25 into the intake pipes 22 of the first cylinder #1 to the third cylinder #3 in synchronization with the injection timing indicated by diagonal lines D or F in FIG. Then, in the next intake stroke, it is immediately mixed with air and sucked into each cylinder #1 to #3. If C ₁ ≠ 3 at step P ₅ , step P ₇
Proceed to step C ₁ to determine whether the count value C ₁ is 0 or not.
When =0, the injection signal _S2 is outputted to the second group of fuel injection valves 26, 27, and 28 in step _P8 . Therefore, fuel is injected from the fuel injection valves 26, 27, and 28 into the intake pipes 22 of the fourth cylinder #4 to the sixth cylinder #6 in synchronization with the injection timing indicated by the diagonal line E in FIG. In the next intake stroke, it is immediately mixed with air and sucked into each cylinder #4 to #6. If C ₁ ≠0 in step _P7 , this flow ends immediately.

In step _P1 , when the 120° signal is OFF, the control unit 34 is turned off in step _P9 .
The count value C ₂ of the second counter built in is 10
Compared to this, when C ₂ <10, this flow ends as is. When C ₂ ≧10 in step _P9 ,
At step _P10 , the count value _C1 of the first counter becomes 0.
If C ₁ =0, this flow ends, but if C ₁ ≠0, the count value C ₁ is reset to 0 in step _P11 . This second counter is a 1° signal counter that is incremented every time a 1° signal is input, and among the 120° signals, the 720° signal that is input every 720° has a pulse width of 10° or more. have. Therefore, step P ₉
Then, in step _P11 , by checking the count value _C2 of the second counter counted during the time when the 120° signal is ON, it is determined whether or not the 120° signal is a 720° signal. The count value _C1 of the first counter is set to 0 to indicate that it is a 120° signal corresponding to the first cylinder #1. As a result, the count value of the first counter due to noise
_C1 can be prevented from varying, and the injection time and the group of fuel injection valves 23 to 28 to be injected can be reliably selected.

Next, an injection amount calculation means, a fuel cut means,
The functions of the fuel cut release means and the asynchronous injection control means will be explained based on the flowchart shown in FIG. Note that this program is executed every 10 ms, and P ₁₀₁ to _{P 122} in FIG. 5 indicate each step of the flow.

First, in step _P101 , the throttle switch
It is determined whether the throttle switch is ON or not, and if the throttle switch is OFF, the fuel flag is set to 0 in step _P102 .
Determine whether or not. This fuel flag is 0
1 indicates that fuel is being supplied, and 1 indicates that fuel is being cut off. When the fuel flag is 0 in step _P102 , that is, when fuel was being supplied during the previous execution, the process proceeds to step _P103 , where the fuel flag is set to 0, and the process proceeds to step _P104 , where the fuel injection amount is calculated. The fuel injection amount is determined by, for example, calculating the basic injection amount based on the engine speed N and the intake air amount, and making various corrections to this basic injection amount based on the cooling water temperature, throttle full-open correction, starting correction, etc. demand. The fuel injection amount resulting from this calculation is synchronously injected for each group at the injection timing.

When the fuel flag is 1 at step P ₁₀₂ ,
In other words, the fuel cut was in progress when the program was executed last time, and the throttle switch was turned OFF this time.
When a predetermined acceleration operation is performed during fuel cut, the amount of fuel injection for asynchronous injection performed during acceleration is calculated based on the operating state in step _P105 , and the count value _C1 of the first counter is checked in step _P106 . do. When the count value _C1 of the first counter is either 3 or 4 in step _P106 , the injection signal _S1 is output as an asynchronous injection signal to the fuel injection valves 23, 24, 25 in step _P107 . , asynchronous injection is performed to supply fuel at the same time as the acceleration operation is performed. When the count value _C1 of the first counter is either 0 or 1 in step _P106 , the injection signal _S2 is used as an asynchronous injection signal to control the fuel injection valves 26, 27, 28 in step _P108 .
During fuel cut, asynchronous injection is performed at the same time as acceleration operation is performed to supply fuel.
Then, in step _P106 , when the count value _C1 of the first counter is either 2 or 5, the step continues without performing asynchronous injection.
Proceeding to step _P109 , the throttle flag and fuel flag are set to 0 _, and this flow ends.

Therefore, if an acceleration operation is performed in the area _G1 surrounded by a broken line in FIG. 4 during fuel cut, the acceleration operation will be performed simultaneously without waiting until the diagonal line H, which is the next synchronous injection , injection signal S ₁
is output as an asynchronous injection signal to fuel injector 2.
3, 24, and 25 to perform asynchronous injection. As a result, the output torque can be obtained at the time g ₁ indicated by the cross in Fig. 4, and the output torque is obtained when the injection is performed at the time indicated by the diagonal line H, which is the synchronous injection time.
Compared to the G ₂ , output torque can be obtained 360° earlier at the crank angle. In addition, if an acceleration operation is performed in the area _G2 surrounded by a broken line in Fig. 4 during fuel cut, the diagonal line D, which is the next synchronous injection timing,
At the same time as the acceleration operation is performed, the injection signal _S2 is output as an asynchronous injection signal to cause the fuel injection valves 26, 27, and 28 to perform asynchronous injection. As a result, the output torque can be obtained at the time g ₂ indicated by the cross mark in Fig. 4, and compared to g ₃ when the output torque is obtained when the injection is performed at the timing indicated by the diagonal line D, which is the synchronous injection timing. , output torque can be obtained 360° faster at the crank angle. Furthermore, during the fuel cut, the area indicated by the broken line in Figure 4
If an acceleration operation is performed in P ₁ and area P ₂ ,
Asynchronous injection is not performed, but synchronous injection is performed after waiting until the next synchronous injection timing, indicated by the diagonal line H or D. That is, when asynchronous injection is performed in region _P1 and region _P2 , the first cylinder #1, the second cylinder #2, and the fourth cylinder
In cylinder #4 and fifth cylinder #5, the fuel is injected at the end or mid-to-late stage of the intake stroke, and the injected fuel remains in the intake pipe 22 without being sufficiently sucked into the cylinder. Therefore, the remaining fuel is sucked into each cylinder in the next intake stroke together with the fuel injected at the next synchronous injection timing (diagonal lines D and E), resulting in a rich mixture. As a result, there is a greater possibility that engine stalling or torque fluctuations will occur, deteriorating acceleration performance, and exhaust performance will also deteriorate. However, in this example, the area P ₁
Even if an acceleration operation is performed in region P ₂ , asynchronous injection is not performed, and injection is performed after waiting until the next synchronous injection timing.This prevents engine stalling and torque fluctuations, improves acceleration performance, and improves exhaust performance. can be made good. As described above, in the present invention, when an acceleration operation is performed during fuel cut, it is determined whether or not to perform asynchronous injection based on the operating state, and if asynchronous injection is performed, it is determined based on the operating state. Since the injection cylinder can be selected based on the fuel injection cylinder and asynchronous injection can be performed immediately, the time from acceleration operation to output torque can be shortened without deteriorating exhaust performance. This makes it possible to reduce the drop in engine speed within this time. Therefore, acceleration response can be improved, and acceleration performance can be improved.

For example, in the case of this embodiment, the longest time is required from when the acceleration operation is performed until the output torque is obtained when the acceleration operation is performed at time t ₁ or t ₂ in FIG. However, in this case, output torque is obtained at g ₂ or g ₃ . point in time
The crank angle from t ₁ to time g ₂ or from time t ₂ to time g ₃ is 550°, and the engine speed is
Assuming that the acceleration operation is performed at 1600 rpm,
It takes 0.057 seconds to rotate 550 degrees. Furthermore, when the engine speed is 1200 rpm, it is 0.076 sec. In other words, it takes 0.057sec or 0.076sec after acceleration operation is performed until output torque is obtained.
It is. On the other hand, when injecting after waiting until the regular synchronous injection timing after the acceleration operation is performed as in the past, for example, the acceleration operation is performed at time _t3 , the injection is performed at time H, and the injection is performed at time g. ₂ , or an acceleration operation is performed at time _t4 , an injection is performed at time D, and output torque is generated at time _g3 . The crank angle from time t ₃ to time g ₂ or from time t ₄ to time g ₃ is 790°.
If an acceleration operation is performed when the engine speed is 1600 rpm, it will take 0.082 seconds to rotate 790 degrees. Therefore, according to the present invention, the time from when an acceleration operation is performed until output torque is obtained can be significantly shortened, and acceleration performance can be improved.

If the throttle switch is ON in step P ₁₀₁ , it is determined in step P ₁₁₀ whether the throttle flag is 1 or not. When it is turned ON during execution, the throttle flag is set to 1 in step _P111 , and the engine speed N is set to the second fuel cut speed shown in FIG. 8 in step _P112 .
Compare with _N2 . If N<N ₂ in step P ₁₁₂ , this flow ends via steps P ₁₀₃ and P ₁₀₄ , and if N≧N ₂ , the fuel flag is set to 1 in step P ₁₁₃ , and the flow returns to step P ₁₁₄ .
Set the fuel injection amount to 0. That is, when the throttle switch is switched from OFF to ON and the engine speed N is higher than the predetermined second fuel cut speed _N2 , the fuel flag is set to 1.
After setting the fuel injection amount to 0, the output of the injection signals S ₁ and S ₂ is stopped, and the supply of fuel to the engine 21 is cut off to perform a so-called fuel cut.

In step _P110 , the throttle flag is set to 1.
In this case, it is determined in step _P115 whether the fuel flag is 1 or not. If the fuel flag is 0, in step _P116 , the engine speed N is set to the predetermined first fuel cut speed _N1 shown in FIG. Compare with. In step P ₁₁₆ , when N≧N ₁ , the steps P ₁₁₃ and P ₁₁₄ are performed.
The routine proceeds to step _P103 and step _P104 to continue fuel injection when N< _N1 . That is, when the engine speed N becomes higher than the first fuel cut speed _N1 while the throttle switch remains ON, for example, when descending down a slope with the accelerator pedal released, Fuel cuts are used to reduce fuel consumption.

At step P ₁₁₅ , the fuel flag is 1.
At step _P117 , the engine speed N
is compared with a predetermined recovery rotational speed Nr, and when N≧Nr, the process proceeds to step P ₁₁₃ and step P ₁₁₄ to continue fuel cut. Step P ₁₁₇
When N<Nr, the fuel injection amount during asynchronous injection is calculated based on the operating condition in step _P118 , and the count value _C1 of the first counter is checked in step _P119 . In step _P119 , when the count value _C1 of the first counter is either 3 or 4, the injection signal is activated in step _P120 .
Fuel injection valves 23, 2 with S ₁ as an asynchronous injection signal
4 and 25, asynchronous injection is performed, and fuel is supplied at the same time as the engine speed N falls below the recovery speed Nr. If the count value _C1 of the first counter is either 0 or 1 at step _P119 , the injection signal is set at step _P121 .
The fuel injection valves 26, 2 use S ₁ as an asynchronous injection signal.
7 and 28, asynchronous injection is performed, and fuel is supplied at the same time as the engine speed N falls below the recovery speed Nr. At step _P119 , if the count value _C1 of the first counter is 2 or 5, the step continues without performing asynchronous injection.
Proceed to page ₁₁₂ . Then, in step _P122 , the fuel flag is set to 0, and this flow ends. Therefore, during fuel cut, if the engine speed N falls below the recovery speed Nr in the area _G1 surrounded by the broken line in FIG. At the same time as the engine speed N drops below the recovery speed Nr,
The injection signal _S2 is output as an asynchronous injection signal to cause the fuel injection valves 23, 24, and 25 to perform asynchronous injection. As a result, the output torque can be obtained at the time g ₁ indicated by the cross in Fig. 4, which is compared to the time g ₁ when the output torque is obtained when the injection is performed at the time indicated by the diagonal line H, which is the synchronous injection time. This allows you to obtain output torque 360° faster at the crank angle. Also, during the fuel cut, the area indicated by the broken line in Figure 4
When the engine speed N falls below the recovery speed Nr at G ₁ , the engine speed N decreases to the recovery speed without waiting until the diagonal line D, which is the next synchronous injection timing.
At the same time, the injection signal S ₂ is output as an asynchronous injection signal to control the fuel injection valves 26 and 2.
7 and 28 to perform asynchronous injection. As a result, the output torque can be obtained at the time g ₂ shown by the cross mark in Fig. 4, compared to g ₃ when the output torque is obtained when the injection is performed at the timing indicated by the diagonal line D, which is the synchronous injection timing. , output torque can be obtained 360° faster at the crank angle. Furthermore, during the fuel cut, the fourth
If the engine speed N falls below the recovery speed Nr in areas P ₁ and P ₂ surrounded by broken lines in the figure, asynchronous injection is not performed and the next synchronous injection timing is indicated by the diagonal line H or the diagonal line D. Wait until then and perform synchronous injection. In other words, when asynchronous injection is performed in region _P1 and region _P2 , in the first cylinder #1, the second cylinder #2, the fourth cylinder #4, and the fifth cylinder #5, the injection occurs at the end or middle of the intake stroke. The fuel is injected at a later stage, and the injected fuel remains in the intake pipe 22 without being sufficiently sucked into the cylinder. Therefore, the remaining fuel is sucked into each cylinder in the next intake stroke together with the fuel injected at the next synchronous injection timing (diagonal lines D and E), resulting in a rich mixture.
As a result, there is a greater possibility that engine stalling or torque fluctuations will occur, and exhaust performance will deteriorate. However, in this example, the area
Even if the engine speed N drops below the recovery speed Nr in P ₁ and P ₂ , no asynchronous injection is performed,
Because we wait until the next synchronous injection period before injecting,
It is possible to prevent engine stalling and torque fluctuations, and to improve exhaust performance. In this way, in the present invention, when the engine speed N becomes lower than the recovery speed Nr during fuel cut, it is determined whether or not to perform asynchronous injection based on the operating condition, and if asynchronous injection is performed, can select injection cylinders based on operating conditions and immediately perform asynchronous injection.
Without deteriorating exhaust performance, it is possible to shorten the time from when the engine speed N drops below the recovery speed Nr to when output torque can be obtained. Can be made smaller. Therefore, occurrence of engine stall or large torque fluctuation can be set lower than the recovery rotation speed, and fuel consumption can be further reduced.

For example, in the case of this embodiment, it takes the longest time until output torque is obtained after the engine speed N falls below the recovery speed Nr at time t ₁ or t ₂ in FIG. In this case, in order to generate output torque when the engine speed N is 642 rpm, g ₂
Or engine speed N at g ₃ is 642rpm
In order to do so, the recovery rotation speed Nr should be 981 rpm. In other words, the deceleration of the engine rotation when the engine suddenly decelerates after the fuel cut is generally
3000 rpm/sec (=100 π radian/sec), and if the engine rotation speed N is 642 rpm at this deceleration, it becomes 21.4 π radian/sec. Also, deceleration
At 3000 rpm/sec (=100πradian/sec), the relationship between the recovery rotation speed Nr (=ωoradian/sec) and the engine rotation speed Np (=ωpradian/sec) at the time when output torque is generated (g ₂ or g ₃ ) is given by the following equation.

ωp=21.4π=ωo−100πt...(1) Then, the crank angle from time t ₁ to time g ₂ or from time t ₂ to time g ₃ is 550 degrees (≒
3.06πradian), the following equation is obtained.

∫ωpdt=ωot−1/2・100πt ² =3.06π …(2) Solving this gives t=0.113sec ωo=32.7πradian/sec=981rpm. Therefore, in order to set the engine rotation speed Np at the time of torque generation to 642 rpm, the recovery rotation speed must be
Just set Nr to 981rpm.

In contrast, the conventional engine speed N
If the engine is injected after waiting until the regular synchronous injection timing after the engine speed drops below the recovery rotation speed Nr, for example, at time t ₃ the engine speed falls below the recovery rotation speed Nr and is injected at time H, and at time g ₂ the output increases. Torque is generated, or becomes less than the recovery rotation speed Nr at time _t4 , injection occurs at time D, and output torque is generated at time _g3 . From time t ₃ to time g ₂ and from time t ₄ to time g ₃ , the crank angle is 790° (≒
4.39πradian). Therefore, in order for the engine speed Nr at time g ₂ or time g ₃ to be 642 rpm, from the following equation, ωp = 21.4π = ωo−100πt ……(3) ∫ωpdt = ωot−1/2・100πt ² =4.39π ...(4) It is necessary that t=0.131sec ωo=34.5radian/sec=1035rpm. As a result, in the past,
In order to set the engine rotational speed Np at the time of torque generation to 642rpm, it is necessary to set the recovery rotational speed Nr higher (1035rp) than in the case of the present invention (981rpm). Therefore, according to the present invention, the recovery rotation speed Nr can be set even lower, and fuel consumption can be further reduced.

In the above embodiment, the case where the present invention is applied to a six-cylinder engine has been described, but the present invention is not limited to this. Further, although the case has been described in which the fuel injection valves are divided into two groups, the present invention is not limited to this, and the invention may be divided into three or four groups. Furthermore, the crank timing for performing synchronous injection is not limited to the timing of the above embodiment.

(Effects of the invention) According to the invention, when an acceleration operation is performed during fuel cut, it is determined whether or not to perform asynchronous injection based on the operating state, and if asynchronous injection is performed, the cylinder in which the asynchronous injection is performed is determined. By selecting the group and immediately performing asynchronous injection, it prevents the occurrence of an overrich air-fuel ratio due to unnecessary asynchronous injection, and shortens the time from acceleration operation to output torque being obtained. Therefore, acceleration performance can be improved without deteriorating exhaust performance, and driving performance can be improved by preventing engine stalling and large torque fluctuations.

Furthermore, according to the above embodiment, during fuel cut, the time from when the engine speed drops below the recovery speed to when output torque is generated can be shortened, so that occurrence of engine stalling and large fluctuations in torque can be reduced. This can be prevented and driving performance can be improved. Moreover, the recovery rotation speed can be set even lower, and fuel consumption can be further reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention. Figure 2~
FIG. 5 is a diagram showing one embodiment of the present invention, and the second
3 is a flowchart showing the interrupt program of the synchronous injection, FIG. 4 is a diagram showing the injection timing, and FIG. 5 is a flowchart showing the main program. 6 to 8 are diagrams showing a conventional example, FIG. 6 is a schematic configuration diagram thereof, FIG. 7 is a diagram showing its injection timing,
FIG. 8 is a diagram showing the relationship between the fuel cut rotation speed, recovery rotation speed, and cooling water temperature. 23, 24, 25, 26, 27, 28... fuel injection valve, 33... operating state detection means, 34... control unit (injection amount calculation means, fuel cut means, fuel cut release means, asynchronous injection control means).

Claims (1)

[Scope of Claim for Utility Model Registration] a. A fuel injection valve that supplies fuel to each cylinder of a multi-cylinder engine; b. Operating state detection means for detecting the operating state; c. Calculating the amount of fuel to be injected based on the operating state. d) the fuel injection valves are divided into cylinder groups, and a synchronous fuel injection signal is applied to the cylinder group immediately before the start of the intake stroke of the preceding cylinder that first enters the intake stroke among the arbitrary cylinder groups; e) fuel cut means for stopping the output of the synchronous fuel injection signal and cutting off the supply of fuel to the engine in a predetermined deceleration operating state; f) starting immediately before the start of the intake stroke of the preceding cylinder; The period until just before the end of the intake stroke is predetermined for each cylinder group, and if the timing at which an acceleration operation is performed during the fuel cut is within the period, an asynchronous fuel injection signal is sent to the cylinder group to which the period including the acceleration operation timing belongs. asynchronous injection control means that outputs an asynchronous fuel injection signal to any cylinder group, while outputting an asynchronous fuel injection signal to any cylinder group when the acceleration operation timing is outside the period.