JPH0253612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection timing control device for an engine.

[Prior art and its problems]

Conventionally, in order to precisely control the amount of fuel injected to each cylinder of an engine, an injector was installed in the intake path of each cylinder on the downstream side of the intake manifold, and fuel was injected at the appropriate timing. For example, JP-A-Sho
Japanese Patent No. 57-108428 describes a fuel injection supply device for an engine that injects fuel into the intake passage at the end of the intake stroke of each cylinder to promote vaporization of the fuel.

However, as long as fuel is injected into the intake passage, if fuel is injected at an early point, such as at the end of the intake stroke, a considerable portion of the injected fuel will adhere to the wall of the intake passage, and this will be transferred to the cylinder with a time delay. The phenomenon of inhalation occurs.

However, during steady operation, no particular problem arises because the fuel adhering to the wall is sucked in in small quantities with a certain delay, but during transient operating conditions such as during acceleration, only the amount of fuel adhering to the wall is supplied. There is a delay in response, and furthermore, it is not possible to respond to changes in the required amount from the time of injection amount determination to intake. As a result, there is a problem that acceleration performance deteriorates. In other words, there will be a shortage of the required fuel.

Further, the same problem of delay in fuel supply response as described above occurs during a transient operating state such as when returning from a fuel cut.

Therefore, in order to solve the above problem, fuel is injected in the middle of the exhaust stroke during steady operating conditions, and fuel is injected at the start of the intake stroke during transient operating conditions such as during acceleration or when returning from a fuel cut. , it is conceivable to change the fuel injection timing depending on the operating state.

However, when changing the fuel injection timing as described above, for example, if the timing is changed immediately after injection in the exhaust stroke, the fuel will be injected again at the start of the intake stroke before the fuel is inhaled, and twice during one stroke cycle. There is a problem with being sprayed.

When switching from intake stroke injection to exhaust stroke injection, for example, if the switch is made just before the intake stroke, fuel will not be injected during that intake stroke but will be injected during the next exhaust stroke, resulting in one fuel injection being omitted. There is a problem with that.

Further, when returning from a fuel cut state to a steady operating state, it is desirable to supply fuel as soon as possible after the return, and if fuel supply is delayed, engine operability may be impaired.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems.The present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide a fuel injection timing control device that can improve drivability.

[Means to solve the problem]

As shown in FIG. 1, the fuel injection timing control device according to the present invention injects fuel from a fuel injection valve corresponding to each cylinder based on a synchronization signal synchronized with the rotational phase of a crankshaft of a multi-cylinder engine. A fuel injection timing control device configured to control injection timing, comprising a first discriminating means for discriminating between a steady operating state and a transient operating state based on a signal related to a rate of change in a charging amount of combustion air; 1 fuel injection for setting the fuel injection timing to a predetermined first timing in a steady operating state and setting the fuel injection timing to a predetermined second timing different from the first timing in a transient operating state based on the output of the first determining means; a timing setting means; and a first fuel controlling the fuel injection timing setting means so as to sequentially change the fuel injection timing from the cylinder that has completed one intake stroke after determining a change in the operating state based on the output of the first determining means. an injection timing change control means; a second determination means for determining whether a predetermined fuel cut condition has been resolved based on the output of the detection means for detecting the operating state of the engine; and outputs of the first and second determination means. and a second injection timing change control means for controlling the fuel injection timing setting means so as to change the fuel injection timing immediately after determining the return when returning from the fuel cut state to the steady operation state based on the above.

[Effect]

In the fuel injection timing control device according to the present invention, the first discriminating means discriminates between a steady operating state and a transient operating state, and the fuel injection timing setting means determines whether the steady operating state is a steady operating state based on the output of the first discriminating means. In this case, the fuel injection timing is set to the predetermined first timing, and in the transient operating state, the fuel injection timing is set to the first predetermined timing.
The timing is set to a predetermined second timing different from the timing.

The first fuel injection timing change control means causes the fuel injection timing setting means to change the fuel injection timing in order from the cylinder that has completed one intake stroke after determining the change in the operating state based on the output of the first determination means. Control.

The second determining means determines whether a predetermined fuel cut condition has been resolved based on the output of the detecting means for detecting the operating state of the engine.

The second injection timing changing means is configured to control the fuel injection timing setting means to immediately change the fuel injection timing upon returning from the fuel cut state to the steady operating state based on the outputs of the first and second determining means. Control.

〔Effect of the invention〕

In the present invention, as described above, when determining whether the operating state is a steady state or a transient state based on a change in the amount of charging air for combustion, and changing the fuel injection timing based on the result of the determination, the intake stroke is changed once. Since the injection timing is changed sequentially from the completed cylinder, duplicate fuel injection and injection errors are reliably prevented, resulting in fuel savings and
It is possible to prevent output from decreasing.

In addition, when changing the fuel injection timing due to the return from the fuel cut to steady operation, the injection timing is changed immediately after the return is determined, so fuel can be injected quickly without causing duplicate injection, and the fuel injection timing can be changed from the fuel cut to It is possible to improve engine drivability (preventing engine stalling, improving acceleration, etc.) when the engine returns to normal operation.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a vertical four-cylinder fuel injection engine will be described below with reference to the drawings.

The fuel injection timing control system in this embodiment is as shown in _FIG.
Four injectors 3 1 to ₃ 4 each injecting fuel into the intake passages 2 of ₁ to 1 ₄ , and these injectors 3
The control unit 4 basically comprises a control unit 4 which outputs drive signals to the control units ₁ to ₃₄ , and various sensors described below which output various detection signals to the control unit 4.

The throttle opening sensor 5 is the throttle valve 6
is connected to detects the opening degree of the throttle valve 6 and outputs a throttle opening signal TH.

The manifold negative pressure sensor 7 is provided upstream of the intake manifold 8 on the downstream side of the throttle valve 6, detects the negative pressure of the intake manifold 8, and outputs a manifold negative pressure signal V.

The crank angle sensor 9 is provided in conjunction with the crankshaft 10 and outputs a crank angle signal C as shown in FIG. 4a.

The cylinder identification sensor 11 is connected to the distributor 12
1, as shown in Figure 4b.
Intake TDC (intake top dead center) of cylinder No. 1 ₁ and its
A cylinder identification signal K is output that covers ATDC 90 degrees (90 degrees after top dead center) at a high level.

As shown in FIG. 3, the control unit 4 includes an input/output port 13, a central processing unit (CPU) 14, and a read-only memory (ROM).
15 and random access memory (RAM) 1
6 and a free running counter 17; a first input circuit 18 that receives the output signals V and TH from the manifold negative pressure sensor 7 and the throttle opening sensor 5; An A/D converter 19 receives V and throttle opening signals TH, converts them into A/D, and outputs them to the input/output port 13, and output signals C and K from the crank angle sensor 9 and cylinder identification sensor 11. A second input circuit 20 receives and shapes each waveform and outputs it to the input/output port 13, and the second input circuit 20 receives the waveform-shaped crank angle signal C and detects the rise and fall of the crank angle signal C. and a rise/fall detection circuit 22 that outputs interrupt signals I corresponding to each to the CPU 14, and a fuel injection signal that receives fuel injection signals from the computer to each of the injectors ₃₁ to ₃₄ and injects fuel with timing and time width corresponding to the signals. Timer 21 that outputs injection pulse f
₁ to ₂₁₄ , and each injector ₃₁ to ₃₄ receives and amplifies the fuel injection pulse f from each timer ₂₁₁ to _214.
The drive circuits 23 ₁ to 23 ₄ output data to the drive circuits 23 1 to 23 4 .

Here, the basic idea of this fuel injection timing control system will be explained.

First, during steady operation, fuel is injected in the middle of the exhaust stroke (exhaust ABDC 90°: exhaust bottom dead center 90°), which slightly lengthens the time from injection to intake, thereby reducing fuel vaporization and mist in the intake passage 2. At the same time, it aims to improve the responsiveness of fuel supply by injecting fuel at the beginning of the intake stroke (intake TDC) during transient operating conditions such as during acceleration or when returning from a fuel cut.

In order to prevent duplicate fuel injection when switching from exhaust ABDC 90° injection to intake TDC injection, and to prevent fuel injection errors (omissions) when switching from intake TDC injection to exhaust ABDC 90° injection, the fuel timing change is determined. The fuel injection timing is sequentially switched starting from the cylinder whose intake stroke has completed once.

However, since duplicate injection is unlikely when switching from fuel cut to steady operating state, the injection timing is immediately switched to the new injection timing after the injection timing change is determined.

The above fuel injection timing is determined by the main routine shown in the flowchart of FIG. 6 based on various detected data indicating the operating state of the engine E, and the fuel injection from each injector 3 ₁ to 3 ₄ is Based on the injection timing determined in the main routine, the interrupt processing routine shown in the flowchart of FIG. 7 is executed during execution of the main routine.

However, the above interrupt processing is executed based on the interrupt signal I output from the rise/fall detection circuit 22 to the CPU 14 at the rise and fall of the crank angle signal C.

The main routine program, the interrupt processing routine program, and other necessary constants are input and stored in the ROM 15 of the computer in advance.

Next, according to the flowchart of FIG. 6, the main routine (step S1) for determining the fuel injection timing is started.
~S16) will be explained.

First, the input/output ports 13 and
When the necessary data stored in the RAM 16 is initialized, the throttle opening signal TH is output in S1.
is read, and in S2 this throttle opening signal
TH and the previous throttle opening signal TH are compared, and based on this comparison result, it is determined in S3 whether or not the throttle is in an acceleration state. If it is in an acceleration state, the process moves to S8 via S4 to S6, and if it is not in an acceleration state. Sometimes, the process moves to S8 via S5.

In S4, it is determined whether the acceleration flag FACC is 1 or 0, and when FACC=0, that is, when acceleration starts, the process moves to S6, the acceleration flag FACC is set to 1 in S6, and the intake top injection counter is set in S7.
The number of intake top injections NTDC is set in CINJ. When the acceleration flag FACC=1 in S4, that is, when the acceleration is in progress since the previous time, the process moves to S8.

S5 is a case where the vehicle is not in an acceleration state, and the ready flag FACC is reset in S5.

In S8 to S11, the fuel cut condition is determined. In S8, the manifold negative pressure signal V is read. In S9, it is determined whether the manifold negative pressure is greater than the fuel cut judgment vacuum FCVAC. If it is, the process goes to S10; if it is not, the process goes to S13. Move to. In S10, it is determined whether the engine rotational speed is greater than the fuel cut determination number FCRPM, and if it is, the process proceeds to S11, and if it is not, the process proceeds to S13. S11
Then, it is determined from the throttle opening signal TH whether the throttle valve 5 is fully closed or not, and when it is fully closed, S1
2, and if it is not fully closed, the process moves to S13.

S12 is a case where all fuel cut conditions are satisfied, and in S12, the fuel cut flag FFC is set to 1.

S13 is a case where the fuel cut does not apply, and in S13, the fuel cut flag FFC
It is determined whether FFC is 1 or 0, and when the state is returned to FFC = 1, that is, it was a fuel cut last time and is not a fuel cut this time, the fuel cut flag FFC is reset in S14, and the fuel cut flag FFC is reset in S15.
At step S16, the number of intake top injections NTDC is set in the intake top injection counter CINJ, and the injection timing flag corresponding to each injector ₃₁ to ₃₄ is set at S16 in order to immediately shift to intake top injection upon return from the fuel cut.
FIN ₁ to FIN ₄ are all set to FIN=1.

Fuel cut flag FFC in S13
When = 0, it returns as is.

In the above main routine, the fuel injection timing is set to exhaust ABDC 90° or intake TDC via the intake top injection counter CINJ.

Next, when the crank angle signal C rises or falls, each injector 3
Determination of the order of fuel injections ₁ to _3.4 , determination of whether to actually inject or not, and fuel injection will be explained based on the flowchart of FIG.

First, when interrupt processing is started by the interrupt signal I from the rising/falling detection circuit 22,
In S21, the time is read from the free running counter 17, in S22, the interrupt cycle is calculated from the previous interrupt time and the current interrupt time, and the engine rotation speed is calculated, in S23, the level of the crank angle signal C is read, and in S24 Then, it is determined whether the level of the crank angle signal C is "H" or "L".
When the level of the crank angle signal C is "H", that is, at intake TDC, it goes to S25, and when it is "L", that is,
When ATDC is 90°, the process moves to S51.

S25 is the case of intake TDC. In S25, the cylinder identification signal K is read, and in S26, it is determined whether the cylinder identification signal K is "H" or "L". If it is "H", the first cylinder 1 ₁ is detected. It is determined that the intake TDC corresponds to , and the process moves to S27, and when it is "L", the process moves to S28.

In S27, the injector counter N is set to 1, and in S28, the injector counter N is incremented by 1.

In this way, in S25 to S28, it is determined which of 1 to 4 the value of the injector counter N indicating the ignition order corresponds to.

Note that this injector counter N corresponds to the subscripts of injectors 3 ₁ to 3 ₄ in FIG. 5, and when the value of this injector counter N is determined, the corresponding cylinder number is also determined, and that cylinder 1 ₁
It can be seen that this corresponds to an intake TDC of ~ ₁₄ (see Figure 5).

In S29, the intake top injection counter CINJ is 0.
When CINJ=0, that is, when it does not correspond to intake top injection, the process moves to S30, and S
In step 30, it is determined which of 1 to 4 the injector counter N corresponds to, and in accordance with the value of N, the process is performed in step S3.
In each of S31 to S34, each injection timing flag FIN is reset and set to inject at the normal exhaust ABDC of 90 degrees.

In S31 to S34 above, for example, when N=2, the injection timing flag FIN ₁ is set in S32.
When N=2, the number ₃ cylinder is reset.
This corresponds to the intake TDC of , and is based on the fact that the intake stroke of the first cylinder ₁₁ has ended at this point.

Intake top injection counter CINJ in S29
= not 0, that is, when intake top injection is set, the process moves to S35, where the intake top injection counter CINJ is counted down.
In S36, it is determined whether the injector counter N corresponds to one of 1 to 4, and depending on the value of N, the process is performed in S37.
- S40, and in each of S37-S40, each injection timing flag FIN is set to 1, and the injection is set to be performed at the intake top TDC.

Even when transitioning from S36, the injector counter N and injection timing counter FIN ₁
The correspondence relationship with IIN ₄ is the same as above, and the cylinders 1 ₁ to 1 ₄ whose intake strokes have been completed at that time are sequentially switched to intake top injection.

When the level of the crank angle signal C is "L" in the above S24, the process moves to S51, and the above S3
1 to S34 and each of S37 to S40 described above, the process moves to S71.

S51 to S59 are routines that determine and execute whether or not to actually inject at the normal injection timing, that is, exhaust ABDC 90°, and S71 to S79 determine and execute whether or not to actually inject at intake TDC. It is.

In S51, the value of the injector counter N is determined, and depending on the value of N at that time, S52 to
Transition to any one of S55, and in each of S52 to S55, each injection timing flag FIN is 1 or 0.
It is determined whether

When transitioning from S51, for example, when N=2, the injection timing flag FIN ₃ is determined in S53 as shown in FIG.
This is because when N=2, the intake ATDC of the third cylinder _I3 corresponds to 90 degrees, and at this time, the fourth cylinder _I4 (corresponding to the injector ₃₃ ) matches the fuel injection timing of the exhaust ABDC of 90 degrees.

In each of S52 to S55, it is determined whether each injection timing flag FIN is 1 or 0, and only when FIN=0, the process moves to S56 to S59, respectively, and S56
- In each of S59, the corresponding injector 3
Fuel is injected from ₁ to 3 ₄ (INJ ₁ to INJ ₄ ).

That is, since S51 to S59 are injected at the timing of exhaust ABDC 90°, they are injected under the condition that FIN=0.

Therefore, in each of S52 to S55, FIN=
When it is determined to be 1, the process returns to the main routine without injecting.

Next, from S71 onwards, injection is performed at the timing of intake TDC, and in S71, the value of the injector counter N is determined, and depending on the value of N, S72 to S
75, and in each of S72 to S75, it is determined whether each injection timing flag FIN is 1 or 0.

At the time of transition from the above S71 to S72 to S75,
For example, when N=2, the injection timing flag FIN ₂ is determined in S73 because the current interrupt time corresponds to the intake TDC.
This is because, as can be seen from FIG. 5, when FIN ₂ =1, the No. 3 cylinder 1 ₃ corresponding to this injector 3 ₂ corresponds to the intake TDC, and injection may be performed immediately from the injector 3 ₂ on the condition that FIN 2 =1.

The determination result FIN in each of S72 to S75
Only when =1, fuel is injected from the corresponding injectors 3 ₁ to 3 ₄ (INJ ₁ to INJ ₄ ) in each of S76 to S79. On the other hand, S72 to S7
When it is determined that FIN=0 in each of 5, the injection is not performed and the process returns to the main routine.

Figure 5 shows the intake of each cylinder 1 ₁ to 1 ₄ when fuel is injected at the timing of exhaust ABDC 90° in a steady operating state, and from that state it shifts to a transient operating state of acceleration state, and then shifts to a steady operating state again.・
This is an operation time chart showing the compression, explosion, and exhaust strokes and fuel injection timing (indicated by arrows in the figure).

A supplementary explanation will be given of the above interrupt processing routine in relation to FIG. 5 above.

Assuming that the state shifts to the acceleration state at the time of code C1 in FIG. 5, the intake TDC of N=1 at the next interrupt.
However, at this time, the intake top injection counter CINJ
is not 0, so S29 to S35, S36, S
The process moves to S71 through 37, and from S71 to S72, but the injection timing flag FIN ₁ is set to FIN ₁ in S32 during the steady operation state before that.
= 0, the injector 3 ₁ (INJ ₁ ) is activated in S76 without moving from S72 to S76.
It will return without being ejected. Therefore, the fuel is not injected at the intake TDC of the first intake stroke after the injection timing change determination at the time of code C1,
At the time of the second intake TDC, FIN ₁ has already been set to 1 in S38, so S72 to S
76 and is injected.

This also applies to the other injectors 3 ₂ to 3 ₄ .

Next, the same applies when changing from intake TDC injection to exhaust ABDC 90° injection for the first time, and injection will continue at the original injection timing until the first intake stroke after the injection timing change determination is completed. ing.

Of course, the injection timing during the above-mentioned steady operation state may be other than the exhaust ABDC 90°, and may also be injection during the compression stroke or the explosion stroke.

In the flowcharts shown in FIGS. 6 and 7 above, the setting of the fuel injection amount is not explained, but the fuel injection amount is determined by the engine speed and throttle opening, or the intake air detected by an intake air sensor (not shown). The CPU 14 uses a predetermined calculation formula, map, etc. that has been input in advance to the ROM 15 based on the amount.
timer 21 ₁ as a fuel injection signal.
~21 Output to ₄ .

As described above, it is possible to prevent duplicate injections and injection errors (omissions) due to injection timing switching.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a functional block diagram of the present invention, FIG. 2 is an overall configuration diagram of a fuel injection timing control system, FIG. 3 is a basic configuration diagram of a control unit, and FIG. Figures a and b are waveform diagrams of the crank angle signal and cylinder identification signal, respectively. Figure 5 is an operation time chart showing the relationship between the stroke of each cylinder, fuel injection timing, and required injection timing. Figure 6 is an operation time chart showing the relationship between the stroke of each cylinder, fuel injection timing, and required injection timing. FIG. 7 is a flowchart of the main routine for determining the interrupt processing routine. 3 ₁ to 3 ₄ ...Injector, 4...Control unit, 5...Throttle opening sensor, 7...Manifold negative pressure sensor, 9...Crank angle sensor, 11
...Cylinder identification sensor.

Claims (1)

[Scope of Claims] 1. Fuel injection timing control that controls the fuel injection timing at which fuel is injected from the fuel injection valve corresponding to each cylinder based on a synchronization signal synchronized with the rotational phase of the crankshaft of a multi-cylinder engine. The apparatus includes a first discrimination means for discriminating between a steady operating state and a transient operating state based on a signal related to a rate of change in the charging amount of combustion air; a fuel injection timing setting means for setting the fuel injection timing to a predetermined first timing when the fuel injection timing is at a predetermined first timing, and setting the fuel injection timing to a predetermined second timing different from the first timing when the fuel injection timing is in a transient operating state; and an output of the first determining means. a first fuel injection timing change control means for controlling the fuel injection timing setting means to sequentially change the fuel injection timing from the cylinder that has completed one intake stroke after determining the change in the operating state based on the engine operating state; a second determining means for determining whether or not a predetermined fuel cut condition has been resolved based on the output of the detecting means; and a return from the fuel cut state to a steady operating state based on the outputs of the first and second determining means. A fuel injection timing control device comprising: second injection timing change control means for controlling the fuel injection timing setting means so as to sometimes change the fuel injection timing immediately after determination of return.