JP2768766B2 - Electronically controlled fuel injector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled fuel injection device for a three-cylinder four-cycle engine for an automobile.

2. Description of the Related Art Conventionally, in this type of electronically controlled fuel injection device, an injector is provided for each cylinder (cylinder) of a three-cylinder four-cycle engine, and the injector is driven by a crankshaft in accordance with an output of a control means. There is a type in which three cylinders are simultaneously fuel-injected by being simultaneously driven at every rotation angle (crank angle) of 720 °. FIG. 5 is an explanatory diagram of this injection operation.

In the figure, the horizontal axis indicates time, and each cylinder # 1 to # 1
The process diagram of # 3 is shown. In the stroke diagram, “explosion” indicates an explosion stroke, “discharge” indicates an exhaust stroke, “suction” indicates a suction stroke, “pressure” indicates a compression stroke, and hatched portions indicate injection timings of all injectors. The signal of each crank sensor is shown on the upper side of the process diagram.
A pulse signal is output every ° (every 240 ° CA). By using every third pulse signal of this pulse signal as an injection timing signal, a crank angle of 720 ° (every 720 ° CA)
The fuel is injected simultaneously into each cylinder every time.

The fuel injection device of the above-mentioned type is described in, for example, “1-Mitsubishi Minica New Model Manual No. 1034030 (issued in January 1989)”
Illustration of injection operation of "Fuel injection during normal operation" on page 88, or "Alto / Frote Service Manual Overview (Suzuki Motor Co., Ltd., issued in September 1988)", 6E-15
It is disclosed in the section of “Injection Timing” on the page.

[Problems to be Solved by the Invention] According to the conventional fuel injection device described above, fuel injection is performed at an injection timing motivated by a specific cylinder, in this case, the suction stroke of the third cylinder # 3. And the first
In the cylinder # 1, the second cylinder # 2 is constantly operated during the compression stroke.
In this case, fuel injection is performed during the exhaust stroke, and this relationship is fixed.

Therefore, the fuel injected at time t1 is the third cylinder # 3
Is supplied to each of the cylinders # 1 to # 3 in the suction stroke a, the second cylinder # 2 in the suction stroke b, and the first cylinder # 1 in the suction stroke c.

Here, in the third cylinder # 3, the intake stroke a is at the time of fuel injection, and the intake valve is open. For this reason,
The injected fuel is charged into the cylinder # 3 in the latter half of the intake stroke in a state that can be said to be almost directly, following the intake flow directly or after colliding with the intake valve. But the second
In the cylinder # 2 and the first cylinder # 1, the intake stroke is not performed during the fuel injection. For this reason, the injected fuel collides with the closed intake valve, atomizes, fills the intake pipe, and then is charged into the cylinders # 2 and # 1 in the intake stroke b or c. That is, in the cylinders # 1 and # 2, the fuel becomes an air-fuel mixture that is almost completely mixed with the air and is charged into the cylinders. Further, the first cylinder # 1 and the second cylinder # 2 have different times from fuel injection to inhalation, so that the degree of atomization and the state of fuel adhesion to the intake pipe are different.

More specifically, in the third cylinder # 3, the fuel is intensively sucked at one time in the latter half of the suction stroke a, and as a result, the fuel and the air are unevenly distributed, while the first and second cylinders # 3 are not.
In the cylinders # 1 and # 2, a substantially uniform distribution of fuel and air is obtained, and the degree of atomization of the air-fuel mixture differs for each of the cylinders # 1 to # 3. Is different from the combustion state of the first and second cylinders # 1 and # 2, and therefore, the output of each cylinder may differ. The combustion state depends on the engine temperature, the fuel temperature, the intake air amount, the intake flow velocity, the fuel amount, and the like, and differs depending on the intake port shape, the cylinder shape, the port position, the ignition position, and the like. The effect of timing exists as described above.

As described above, in the above-described conventional example, the intake state of the air-fuel mixture in each of the cylinders # 1 to # 3 is fixedly determined. There was a problem of becoming. This is particularly noticeable when the engine is running at a low speed such as at idle.

If the injection timing is set to a crank angle of 720 ° or less, for example, 480 °, it is easily conceivable that the intake state in each cylinder can be sequentially changed. However, in this case, the amount of fuel to be taken into each cylinder varies depending on whether it is a single injection or a double injection, and this also causes instability of the engine rotation and is difficult to put into practical use. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to supply a substantially equal amount of fuel to each cylinder without a fixed determination of the air-fuel mixture intake form in each cylinder. An object of the present invention is to provide an electronically controlled fuel injection device that can stabilize engine rotation.

[Means for Solving the Problems] In an electronically controlled fuel injection device of the present invention for solving the above problems, an injector is provided for each cylinder of a three-cylinder, four-cycle engine, and the injector responds to the output of the control means. In the electronically controlled fuel injection device of the type in which three cylinders are simultaneously driven at predetermined injection timings to simultaneously perform fuel injection, the control means controls the injectors of all cylinders based on signals at every 480 ° crank angle. It outputs an injection timing signal, calculates the fuel injection time, calculates the time from the current time of the signal generation for each crank angle 480 ° to the end of the first suction stroke, and calculates the fuel injection time from the end time. And a time obtained by subtracting an offset time until fuel injected from the injector reaches the combustion chamber is added to the current time. It calculates the injection start time, in which from the injection start time to the injection end time after the fuel injection time is configured to output as the injection timing signal for the injector.

[Operation] According to the means, the intake mode of the air-fuel mixture in each cylinder is different for each cycle of the engine, and the combustion state of each cylinder is changed for each cycle, so that the variation in combustion between cylinders is reduced. You.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 3 shows an overall configuration diagram of an electronically controlled fuel injection device of a three-cylinder four-cycle engine for an automobile. In the figure, in the middle of an intake pipe 2 connected to an engine 1,
A throttle valve 3 is provided.

The throttle valve 3 is provided with a throttle sensor 4. The throttle sensor 4 is a throttle valve 3
It detects that the valve opening is equal to or less than a predetermined opening, that is, is in an idling position, and outputs a throttle valve opening signal to an electronic control unit (ECU) 5.

Injector 6 arranged downstream of throttle valve 3
Is connected to a fuel pump (not shown) by a pipe and is also electrically connected to the ECU 5, and is controlled by a drive signal from the ECU 5. The injector 6 is provided for each cylinder.

In the pipe 7 branched from just downstream of the throttle valve 3,
An intake pressure sensor 8 is provided. The intake pressure sensor 8
The absolute pressure in the intake pipe 2 is detected, and the intake pressure signal is output to the ECU 5.

The engine 1 is provided with a water temperature sensor 9. Water temperature sensor 9 detects the temperature of the cooling water of engine 1 and outputs a temperature signal to ECU 5.

The engine 1 is provided with a crank angle sensor 10. The crank angle sensor 10 outputs a pulse signal to the ECU 5 every three rotations of the crankshaft, ie, every 240 degrees of the crank angle. In the ECU 5, the engine speed Ne is calculated based on the ignition cycle based on the pulse signal. The pulse signal of the crank angle sensor 10 (also referred to as a crank angle sensor signal) can be replaced with another signal synchronized with the rotation of the engine, for example, a timing signal such as an ignition signal.

The internal structure of the ECU 5 is shown in a block diagram in FIG. In the figure, signals from an intake pressure sensor 8, a water temperature sensor 9, and a throttle sensor 4 enter an input processing circuit 51 and are input to a CPU 53 via an A / D converter 52.

The pulse signal of the crank angle sensor 10 is input to an input processing circuit 54.
Is input to CPU 53. C to which ROM55 and RAM56 are connected
In the PU 53, each input signal is arithmetically processed, that is, the required fuel amount is calculated, and a pulse signal having a time width corresponding to the amount or an asynchronous pulse signal is driven.
Send to 57. The drive circuit 57 controls the injector 6 by sending a drive current to the injector 6 while the pulse signal is on.

FIG. 1 shows a flowchart of an interrupt processing routine for each input of a crank angle sensor signal (every 240 ° crank angle) in the ECU 5. This processing is executed by the operation of the CPU 53 based on the program stored in the ROM 55. When the engine key of the automobile is turned on, the ECU 5 starts operating, and the program stored in the ROM 55 in advance is executed. The processing is advanced based on.

In step S1, it is determined whether a fuel cut has occurred. The fuel cut is to stop the fuel injection under a predetermined condition, for example, at the time of deceleration when the engine speed is equal to or higher than the predetermined speed and the throttle valve is in an idling state, and the engine speed drops below the predetermined speed. Is released when the accelerator pedal is depressed or when the accelerator pedal is depressed.

If it is determined that the fuel is not cut, the step
Proceeding to S2, the injection timing control flag FIG is checked. If FIG = 1, it is the fuel injection timing, so the fuel is injected by the processing of steps S3 to S6 (this processing will be described later in detail). Then, in step 7, "0" is set in the flag FIG, and the process ends. Here, the flag FIG is used to indicate that the timing of “1” indicates the fuel injection timing, and the status of “0” indicates that it is not the fuel injection stop timing, that is, the injection timing. Accordingly, if the process is performed with FIG = 0 in step S7, the next time an interrupt is made by the crank angle sensor signal, NO in step S2.
Is determined, and step S3 is not executed. That is, no fuel is injected at this time. Then, at the next interruption, in order to perform injection, in step S8, FIG is set to "1" and the processing is terminated. As a result, every 480 ° crank angle (480 ° CA
Each time). Also, no fuel injection is performed when the fuel is cut in step S1. At this time, FIG. Set in step 9 is set to "1", and preparation is made so that the fuel cell can be immediately returned (fuel injection) when the fuel cut is released.

Next, the case of performing fuel injection based on the determination in step S2 will be described with reference to FIG. 2 and FIG. 2 showing an injection operation explanatory diagram when the program is executed, in addition to FIG.
In FIG. 2, the horizontal axis represents time, and from the top to the bottom, the operation diagram of the crank angle sensor signal generated at every crank angle of 240 °, the stroke diagram of each cylinder # 1 to # 3, An operation diagram of the injector and a diagram of a predicted cylinder arrival timing of the fuel are shown. In the above stroke diagram, “explosion” is an explosion stroke, “discharge” is an exhaust stroke, “suction” is a suction stroke, and “pressure” is a compression stroke. Have been.

In FIG. 2, if every other crank angle sensor signal is injected during fuel injection, that is, if fuel injection is simultaneously performed for three cylinders based on the crank angle sensor signal at time t1, next time t
3. Next, as in the crank angle sensor signal at the time t5, the fuel is injected at one injection timing every 480 ° of the crank angle based on each sensor signal.

This fuel injection is based on the processing of steps S3 to S6 in FIG. 1. First, in step S3, the engine speed Ne is determined.
The fuel injection time TINJ is calculated from the pressure P and the intake pipe pressure P.

Next, in step S4, a time TADM from the current time TNOW to the end of the first suction stroke is calculated. For example, when the present process is executed based on the crank angle sensor signal at time t1 in FIG.
The time TADM up to the end time of the suction stroke a is calculated.
Since the crank angle at the end of the intake stroke has a fixed relationship, the intake stroke end time TADM is the engine speed Ne at that time.
Is calculated based on Similarly, the time until the end of the suction stroke c of the first cylinder # 1 at time t3, and the second time at time t5.
The time until the end of the suction stroke e of the cylinder # 2 is obtained.

Next, the injection start time TON is set in step S5. The injection start time TON is obtained by subtracting a half time (TINJ / 2) of the fuel injection time TINJ from the intake stroke end time TADM and an offset time TOFFSET until the fuel injected from the injector reaches the combustion chamber. It is calculated by adding time to the current time to TNOW. That is, TON = TNOW + TADM- (TINJ / 2) -TOFFSET. Then, when the injection start time TON is reached by the built-in timer, the CPU 53 turns on the injector by a timer interrupt. Subsequently, at step S6, the injection start time
The injection end time TOFF is set by adding the injection time TINJ to TON. When the internal timer reaches the injection end time TOFF, the CPU 53 turns off the injector by a timer interrupt.

The processes in steps S4 to S6 are processes for causing half of one injection to flow rapidly to the cylinder in the suction stroke at the current time TNOW. Thus, a fuel amount of 1.5 times is supplied to each cylinder uniformly in each intake stroke for each intake stroke of the cylinder.

This will be described in detail with reference to FIG. Now, the first cylinder #
In one intake stroke c, the fuel injected at time t1 and half the amount of fuel injected at time t3 are sucked. That is, a total of 1.5 times of fuel is sucked. Of the injection amount at the time t3, the injection amount in the latter half is sucked in the next suction stroke f together with the injection amount at the next time t5. In the suction stroke d of the third cylinder # 3, of the fuel injected at the time t1, the fuel in the latter half of the suction stroke a and the injection amount at the time t3 are sucked. Further, in the suction stroke g, the fuel injected at the time t5 and the fuel half the injection amount at the time t7 are sucked.
Further, in the suction stroke e of the second cylinder # 2, the fuel injected at the time t3 and the fuel of half the injection amount at the time t5 are sucked.

Thus, in each of the cylinders # 1 to # 3, the fuel amount for 1.5 times is almost uniformly sucked in each suction stroke.

When the processes in steps S3 to S6 are completed, "0" is set in the flag FIG in step 7 as described above, and the process ends.

According to the above-mentioned electronically controlled fuel injection device, the intake mode of the air-fuel mixture in each of the cylinders # 1 to # 3 is the same as that of the engine.
It changes sequentially in each cycle, and the combustion state in each cylinder is 1
The fuel supply amount is changed every cycle, and the amount of fuel supplied to each of the cylinders # 1 to # 3 is also supplied substantially equally. Therefore crank angle
Unlike the conventional fuel injection system in which fuel is injected every 720 °, the variation in combustion between the cylinders # 1 to # 3 is reduced, so that the engine rotation is stabilized. This is effective at the time of low rotation such as at the time of idling.

Further, since the fuel injection cycle is shortened from the conventional 720 ° CA to the 480 ° CA, the transient responsiveness is improved.

Also, in FIG. 2, if the fuel injection return condition is satisfied at time T1 after the fuel cut state is reached during the fuel injection, the crank angle sensor signal immediately after that is at time T2.
The fuel injection is performed based on the crank angle sensor signal at the time T2.
Times and simultaneous injection. In the conventional one,
Assuming that the injection timing matches the suction stroke of the second cylinder # 2 before the fuel cut, the injection restart after the fuel cut is the time when the second cylinder # 2 is ignited after the time T2.
From T4, the injection timing is delayed by the crank angle of 480 °, but according to this example, the delay is also eliminated.

Further, since the calculation of the fuel injection amount is performed for each cycle of the crank angle sensor signal, the fuel injection can be restarted from any signal timing based on the latest calculation result, and the required fuel amount can be injected without delay. Transient response is also improved.

It should be noted that the present invention is not limited to the above-described embodiment, and can be modified without departing from the gist of the present invention.

[Effect of the Invention] According to the electronically controlled fuel injection device of the present invention, it is possible to supply a substantially equal amount of fuel to each cylinder without being able to determine the intake mode of the air-fuel mixture in each cylinder in a fixed manner. In addition, variations in combustion between cylinders are reduced, so that engine rotation can be stabilized.

[Brief description of the drawings]

1 to 4 show a first embodiment of the present invention. FIG. 1 is a flow chart of an electronically controlled fuel injection system of a three-cylinder four-cycle engine, and FIG. FIG. 3 is an overall configuration diagram of the fuel injection device,
FIG. 4 is a block diagram of the electronic control unit. FIG. 5 is an explanatory view of a conventional injection operation.

Claims (1)

(57) [Claims] An injector is provided for each cylinder of a three-cylinder four-cycle engine, and the injectors are simultaneously driven at predetermined injection timings in accordance with an output of a control means, whereby fuel is simultaneously injected into three cylinders. In the electronically controlled fuel injection device, the control means outputs an injection timing signal to injectors of all cylinders based on a signal at every crank angle of 480 °, and calculates a fuel injection time and the crank angle. Calculate the time from the current time of signal generation for every 480 ° to the end of the first suction stroke, and calculate the half of the fuel injection time from the end time and the time from when the fuel injected from the injector reaches the combustion chamber. An injection start time is calculated by adding the time obtained by subtracting the offset time to the current time, and the injection after the fuel injection time from the injection start time is calculated. Electronically controlled fuel injection device according to the up completion time characterized by being configured to output as the injection timing signal for the injector.