JPH0510495B2 - - 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) Conventionally, in order to precisely control the amount of fuel injected to each cylinder of an engine, an injector was provided in the intake path of each cylinder on the downstream side of the intake manifold, and fuel was injected at appropriate timing. Things have been put into practical use, for example,
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 operating conditions, no particular problem arises because the fuel adhering to the wall is sucked in in fixed amounts with a certain delay, but during transient operating conditions such as during acceleration, only the amount of fuel adhering to the wall is supplied. A delay in response occurs, and furthermore, it is not possible to respond to changes in the required amount from 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.

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

(Object of the Invention) The present invention has been made to solve the above problems, and it is possible to improve the vaporization of fuel during steady operation, and to provide a fuel that does not cause a delay in the response of fuel supply during transient operation. An object of the present invention is to provide an injection timing control device.

(Structure of the Invention) A fuel injection timing control device according to the present invention is arranged in each intake passage of a multi-cylinder engine as shown in FIG. In the fuel injection timing control device, the fuel injection timing control device includes a fuel injection valve provided in the fuel injection valve, and a fuel injection timing control means for controlling a fuel injection timing for injecting fuel from the fuel injection valve. a charging amount detection means disposed in the combustion chamber for detecting a value related to the filling amount of air taken into the combustion chamber;
a discriminating means for discriminating between a steady operating state and an accelerating operating state based on the rate of change in the charging amount of combustion air upon receiving the output of the charging amount detecting means; The fuel injection timing setting means sets the injection timing to a timing other than the intake stroke and sets the fuel injection timing to the intake stroke when the engine is in an accelerated driving state.

(Function) In the fuel injection timing control device according to the present invention, the filling amount detection means detects a value related to the filling amount of air taken into the combustion chamber, and the discriminating means detects the output of the filling amount detection means. Based on the rate of change in the filling amount, a steady state of operation and an accelerated state of operation are determined.

The fuel injection timing setting means sets the fuel injection timing to a timing other than the intake stroke when the engine is in a steady state of operation, and sets the fuel injection timing to a period other than the intake stroke when the engine is in an accelerating operation state based on the output of the determining means.

In other words, during steady operation, fuel is injected at a time other than the intake stroke, so the time between fuel injection and intake becomes longer, and the injected fuel is heated in the intake passage and becomes vaporized and atomized. is promoted, improving combustibility within the combustion chamber. In a steady state of operation, even if the fuel is injected at a time other than the intake stroke, there will be no problem of a delay in the response of fuel supply. On the other hand, during accelerating operation, fuel is injected during the intake stroke, so the injected fuel does not adhere to the wall of the intake passage, and almost the entire amount is taken into the combustion chamber by the intake air flow immediately after injection. Acceleration responsiveness can be improved by supplying fuel in an amount corresponding to the demands of the accelerating driving state to the combustion chamber with good responsiveness.

(Effect of the invention) According to the fuel injection timing control device according to the present invention,
As explained above, by providing the filling amount detection means, the discrimination means, and the fuel injection timing setting means,
In steady-state operating conditions, fuel vaporization and atomization can be promoted by injecting at times other than the intake stroke, and in accelerating operating conditions, by injecting during the intake stroke, the injected fuel is carried along with the intake airflow. By sending most of the fuel to the combustion chamber, it is possible to supply a highly accurate injection amount according to the request without delay in response.

In other words, in steady-state operating conditions, where delay in fuel supply response due to fuel adhesion to walls is not a problem, fuel is injected at times other than the intake stroke to promote vaporization and atomization of the fuel, but response delay in fuel supply becomes a problem. During acceleration operation, the fuel can be injected during the intake stroke to improve the responsiveness of fuel supply.

(Example) Hereinafter, an example in which the present invention is applied to a vertical four-cylinder fuel injection engine will be described 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 downstream of the throttle valve 6 and upstream of the intake manifold 8, 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 quank shaft 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 Celsius (90 degrees Celsius 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; V and throttle opening signal
An A/D converter 19 that receives TH, A/D converts each, and outputs it to the input/output port 13, and receives output signals C and K from the crank angle sensor 9 and cylinder identification sensor 11 and shapes each into waveforms. A second input circuit 20 outputs to the input/output port 13, and receives the crank angle signal C whose waveform has been shaped by the second input circuit 20, detects the rise and fall of the crank angle signal C, and generates corresponding interrupts. A rising/falling detection circuit 22 outputs a signal I to the CPU 14, and receives a fuel injection signal from the computer to each injector ₃₁ to ₃₄ and outputs a fuel injection pulse f having a timing and time width corresponding to the signal. timer 21
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 time control system will be explained.

First, during steady operation, fuel is injected in the middle of the exhaust stroke (exhaust ABDC 90°: 90° after exhaust bottom dead center) to lengthen the time from injection to intake, thereby increasing the vaporization of fuel in the intake passage 2. While promoting atomization, it also 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 immediately after returning from a fuel cut. be.

When switching from exhaust ABDC 90° injection to intake TDC injection or from intake TDC injection to exhaust BTDC 90°
When switching to injection, in order to prevent duplicate injection of fuel (injection twice in one cylinder stroke cycle) and omission of injection, apply the new injection timing after switching sequentially from cylinders 1 ₁ to 1 ₄ where the intake stroke has ended, or Immediately after returning from the fuel cut, there is no possibility of duplicate injection, so the new timing after switching is applied immediately.

The fuel injection timing described above 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 determined as described above. Based on the required fuel injection timing obtained in the main routine, the seventh
This is executed in the interrupt processing routine shown in the flowchart in the figure.

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

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

Next, according to the flowchart in Fig. 6, the main routine (step S1
~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 read in S1, and the throttle opening signal TH is read in S2.
is compared with the previous throttle opening TH, and based on this comparison result, it is determined in S3 whether or not the acceleration state is reached, and when it is in the acceleration state, it is changed from S4 to S8 or
It moves from S4 to S8 via S6 and S7, and when it is not in an acceleration state, it moves to S8 via S5. S4
Then, it is determined whether the acceleration flag FACC is 1 or 0,
When FACC=0, that is, when acceleration starts, it moves to S6,
In S6, the acceleration flag FACC is set to 1,
At S7, the number of intake top injections NTDC is set in the intake top injection counter CINJ.

In other words, when determining acceleration based on the throttle opening, it is determined that acceleration is occurring only for a moment, and the intake air is often drawn after a delay in the acceleration determination; In view of this, the intake top injection counter CINJ is provided in order to execute the intake top injection approximately the predetermined number of times, and the intake top injection number NTDC is set to, for example, 20 times. However, it is also possible to set the value to 20 or less or 20 or more times.

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 acceleration flag FACC is reset in S5.

In S8 to S11, the fuel cut condition is determined, so 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, and if it is, the process proceeds to S10, and if it is not, the process proceeds to S13. In S10, it is determined whether the engine speed is greater than the fuel cut determination rotation speed FCRPM, and if it is, the process moves to S11, and if it is not, the process moves to S13.

In S11, it is determined from the throttle opening signal TH whether the throttle valve 5 is fully closed or not. If it is fully closed, the process advances to S12, and if it is not fully closed, the process advances to S13.

S12 is the case when all fuel cut conditions are met, and in S12, the fuel cut flag is
FFC=1 is set.

S13 is a case where it does not correspond to a fuel cut, and in S13 it is determined whether the fuel cut flag FFC is 1 or 0. If FFC = 1, that is, it was a fuel cut last time and has returned to a state where it is not a fuel cut this time, the fuel cut flag is set in S14. The FFC is reset and the number of intake top injections is displayed on the intake top injection counter CINJ in S15.
NTDC is set.

That is, after the fuel cut is released, the intake top injection is executed a predetermined number of times as described above.

In order to immediately shift to intake top injection upon return from the fuel cut, injection timing flags FIN ₁ to FIN ₄ corresponding to each injector 3 ₁ to 3 ₄ are all set to FIN=1 in S16.

Fuel cut flag FFC = 0 in S13
It will return as is when .

In the above main routine, the fuel injection timing is set to exhaust ABDC 90° and to 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 each crank signal C is read, and in S24 Then, it is determined whether the level of the crank angle signal C is "H" or "L", and when the level of the crank angle signal C is "H", that is, the intake TDC
When it is "L", that is, when ATDC is 90°, it 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".
When it is "L", it is determined that it corresponds to the intake TDC of the first cylinder ₁₁ , 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, it is determined whether the intake top injection counter CINJ is 0 or not. When CINJ = 0, that is, if it does not correspond to intake top injection, the process moves to S30, and in S30, it is determined which of 1 to 4 the injector counter N corresponds to. Determined, S31 to S34 depending on the value of N
In each of S31 to S34, each injection timing flag FIN is reset and set to inject at the normal exhaust ABDC of 90°.

In S30 to S34 above, for example, when N=2
In S32, the injection timing flag FIN ₁ is reset by the intake air of the 3rd cylinder ₁₃ when N=2.
This corresponds to TDC and takes into consideration the fact that the intake stroke of the No. 1 cylinder ₁₁ has been completed at this point.

In S29, intake top injection counter CINJ=
When it is not 0, that is, when intake top injection is set, the process moves to S35, and the intake top injection counter CINJ is counted down in S35.
This is to count the number of intake top injections. Next, in S36, it is determined which of 1 to 4 the injector counter N corresponds to, and the process moves to one of S37 to S40 depending on the value of N, and S37 to
In each of S40, each injection timing flag FIN is 1
The engine is set to inject at the intake top TDC.

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

When the level of the crank angle signal C is "L" in the above S24, the process moves to S51, and from each of the above S31 to S34 and each of the above S37 to S40, the process moves to S71.

S51 to S59 are normal injection timings, that is, exhaust
This is a routine that judges and executes whether or not to actually inject at ABDC90°, and S71 to S79 are intake TDC
This routine determines whether or not to actually inject the fuel and executes it.

In S51, the value of the injector counter N is determined, and S52 to S55 are determined according to the value of N at that time.
In each of S52 to S55, it is determined whether each injection timing flag FIN is 1 or 0.

When transitioning from S51 above, for example, when N=2
In S53, the injection timing flag FIN ₃ is judged as N=2, as can be seen from FIG.
When , it corresponds to the intake ATDC of 3rd cylinder 1 ₃ , 90°,
At this time, No. 4 cylinder 1 ₄ (corresponds to injector 3 ₃ )
This is because the fuel injection timing matches the exhaust ABDC90°.

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, and in each of S56 to S59, the corresponding injector ₃₁ to ₃₄ ( INJ ₁ ～
Fuel is injected from 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, when it is determined that FIN=1 in each of S52 to S55, the process returns to the main routine without injecting.

Next, from S71 onwards, the injection is performed at the timing of the intake TDC. In S71, the value of the injector counter N is determined, and the process moves to one of S72 to S75 depending on the value of N. In each of S72 to S75, It is determined whether each injection timing flag FIN is 1 or 0.

For example, when transitioning from S71 to S72 to S75 above, N
Injection timing flag in S73 when = 2
FIN ₂ is judged because the current interrupt point corresponds to the intake TDC, so when N=2, as can be seen from Fig. 5, the No. 3 cylinder ₁₃ corresponding to this injector ₃₂ is at the intake TDC. Applicable, FIN ₂
This is because the fuel may be immediately injected from the injector 3 ₂ on the condition that =1.

Judgment result FIN=1 in each of S72 to S75
Fuel is injected from the corresponding injectors 3 ₁ to 3 ₄ (INJ ₁ to INJ ₄ ) only in each of S76 to S79. On the other hand, when it is determined that FIN=0 in each of S72 to S75, no injection is performed and the process returns to the main routine.

Figure 5 shows exhaust ABDC90° under steady operating conditions.
Intake and intake of each cylinder 1 ₁ to _{1 4} when fuel is injected at the timing of
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 from S29 through S35, S36, and S37
Transition to S71, and from S71 to S72, but the injection timing FIN ₁ is the same as before in the steady operating state.
Since FIN ₁ = 0 is set in S32,
The process does not proceed from S72 to S76 and returns in S76 without being injected from the injector 3 ₁ (INJ ₁ ). Therefore, the intake TDC of the first intake stroke after the injection timing change determination at the time point C1 of the symbol
It is not injected, and at the second intake TDC
This is because FIN ₁ has already been set to 1 in S38.
The fuel will be injected moving from S72 to S76.

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

Next, the same applies when switching from intake TDC injection to exhaust ABDC 90° injection, and until the end of the first intake stroke after the injection timing change determination at the time of code C2, injection is performed at the original injection timing. It is becoming more and more like this.

Of course, the injection timing during the steady operation state may be other than the exhaust ABDC90°, and injection may be performed 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 .

Here, each means described in the claims,
To explain the correspondence with the configuration in the above embodiment, what corresponds to the fuel injection timing control means is:
A control unit 4 including various circuits, ports, computers, etc., each crank sensor 9,
The cylinder identification sensor 11 corresponds to the filling amount detection means, and the throttle opening sensor 5 corresponds to the determination means. ~S6 and acceleration flag
FACC, which corresponds to the fuel injection timing setting means, includes the control unit 4, a control program for controlling the fuel injection timing, an intake top injection counter CINJ, an injector counter N, and an injection timing flag in the control program.
It is FIN.

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

According to the fuel injection timing control device of the above embodiment,
During steady operating conditions, fuel vaporization and atomization can be promoted by injecting at the timing of exhaust BTDC 90°, and during transient operating conditions, fuel is injected at the timing of intake TDC to carry the injected fuel into the intake air flow. This makes it possible to minimize adhesion to the wall surface of the intake passage, thereby increasing the responsiveness of fuel supply.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; 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 4a and 4b 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 the fuel 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. A fuel injection valve disposed in each intake passage of a multi-cylinder engine and located at a predetermined distance from a combustion chamber in the intake passage, and injecting fuel from the fuel injection valve. In a fuel injection timing control device comprising a fuel injection timing control means for controlling fuel injection timing, the fuel injection timing control device is arranged in an intake passage upstream of the fuel injection valve and is related to the filling amount of air taken into the combustion chamber. a charging amount detecting means for detecting a value of the filling amount; a discriminating means for receiving the output of the filling amount detecting means and discriminating between a steady operating state and an accelerated operating state based on a rate of change in the charging amount of combustion air; and the discriminating means The fuel injection timing setting means sets the fuel injection timing to a period other than the intake stroke when the engine is in a steady state of operation, and sets the fuel injection timing to the intake stroke when the engine is in an accelerating state of operation based on the output of the fuel injection device. Fuel injection timing control device.