JPH0526286Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) This invention relates to a fuel injection supply system for an engine, particularly one that includes fuel injection valves upstream of an intake port and a throttle valve.

(Prior Art) Electronically controlled engines equipped with fuel injection devices have been widely put into practical use, and the entire system of such engines is assembled as shown in FIG. The figure shows a type in which a fuel injection valve 20 that is opened and closed by a drive pulse is provided in the intake port portion 6 of each cylinder, and the amount of fuel supplied is controlled by controlling the width of the opening pulse of the injection valve 20.

To explain this type of fuel injection, please refer to the monthly magazine "Automotive Engineering" published by Railway Japan Co., Ltd.
In the case of simultaneous injection in all cylinders, the fuel injection pulse width (Ti) expressed by the following equation (1) is synchronized with the ignition timing twice per engine revolution. and is output to the injection valve 20.

Ti=Tp×COEF×α+Ts...(1) Here, Tp is calculated from the intake air amount (Qa) detected by the air flow meter 11 and the engine speed (Ne) measured by the crank angle sensor 12. = Basic pulse width calculated as K _cpNsT × Qa/Ne (K _cpNsT is a constant), COEF is the sum of various correction coefficients, α is the air-fuel ratio feedback correction coefficient obtained based on the signal from the oxygen sensor 14, Ts
is the invalid pulse width depending on the battery voltage. For example, in COEF there is a water temperature increase correction factor (K _TW ).
There is also a starting and post-starting increase correction coefficient (K _AS ).
According to K _TW , the lower the cooling water temperature (T _W ) detected by the water temperature sensor 13, the more Tp is increased, and according to K _AS , the lower T _W is during cranking, the more fuel is used, but after that, the amount of fuel increases at a constant level. The amount is increased until it reaches zero. In other words, when the injected fuel is cold, it is difficult to vaporize, so it is difficult to form an air-fuel mixture, and the air-fuel mixture becomes thinner by the amount of fuel that has not vaporized.
The system is designed to supply multiple types of fuel.

Note that the normal injection timing is not synchronized with the intake stroke in order to improve steady combustion.

Also, during acceleration (when the idle contact of the throttle valve switch 15 changes from ON to OFF),
Interrupt injection is performed separately from the normal injection timing to improve drivability during acceleration.

(Problem that the invention aims to solve) By the way, in such devices, interrupt injection during acceleration and fuel increase correction during cold conditions may lead to deterioration of fuel efficiency or an increase in HC due to fluctuations in the air-fuel ratio. Even if you do this, some cylinders may misfire due to insufficient fuel, which may impair acceleration. Furthermore, during a cold start, the injected fuel may wet the spark plug and cause ignition to fail.

These causes are related to the behavior of the injected fuel particles, and it is difficult to form a good air-fuel mixture. In other words, the oil droplets vaporize over time, and the vaporized fuel diffuses and mixes with the air around the oil droplets to form a premixture. In this case, the injected fuel is immediately sucked into the cylinder 7, and the oil droplets do not have enough time to vaporize, which prevents the formation of a good air-fuel mixture.

For this reason, if only the vaporization of the oil droplets is considered, the injection valve 20 should be provided at a distance from the cylinder 7, but if this is done, fuel cannot be supplied to the cylinder 7 with a good response.

Therefore, it is required to form the air-fuel mixture necessary for combustion without reducing the responsiveness of fuel injection.

This idea was created by focusing on these conventional problems.In addition to the first injection valve installed at the intake port, a second injection valve is also installed upstream of the throttle valve to reduce engine load. Sometimes, the amount of fuel injected from the second injector is increased to fill the intake manifold downstream of the throttle valve with a premixed mixture, and the injection timing by the first injector is synchronized with the intake stroke regardless of the engine load. The object of the present invention is to provide a device that allows

(Means for Solving the Problems) As shown in FIG. 3
1, a means 34 for calculating the basic fuel injection amount (Tp) according to the detected values of the engine speed (Ne) and the engine load (for example, the intake air amount Qa), and a means 34 for calculating the basic fuel injection amount (Tp) according to the detected values of the engine speed (Ne) and the engine load (for example, the intake air amount Qa); As the load decreases, the proportion shared by
means 35 for setting the sharing ratio (K _DIS ) of the fuel injectors 31 to be large; and means 35 for setting the sharing ratio (K _DIS ) of the fuel injectors 31 to be large; The fuel injection amount (Tit,
means 36, 37 for calculating the amount of fuel (Tip), and means 36, 37 for calculating the calculated fuel injection amount to the corresponding fuel injection valves 31 and 20.
There are provided means 38 and 39 for respectively outputting to the fuel injection valve 20 and means 40 for instructing the output means 39 to synchronize the injection timing of the first fuel injection valve 20 with the intake stroke. In addition, 32 is an engine rotation speed sensor, 3
3 is an engine load sensor, 3 is an intake manifold, and 7 is a cylinder.

(Function) When the engine is under low load, the proportion of the basic fuel injection amount shared by the second injector 31 (K _DIS ) is increased, and most of the required fuel is directed from the second injector 31 to the throttle valve 2. is injected. In this case, the fuel injected from the injection valve 31 is crushed and finely divided by the high-speed airflow flowing around the throttle valve 2.
Furthermore, the intake manifold 3 downstream of the throttle valve 2
It vaporizes within the air and mixes with the surrounding air, quickly forming a premixed mixture. Therefore, when the engine is under low load, combustion is stabilized and fuel efficiency is improved without having to increase the cold time increase as in the conventional case. Particularly during cold starting, fuel injection from port 6 can be omitted or reduced.
The spark plug inside the cylinder 7 will not get wet.

On the other hand, when the load increases due to opening of the throttle valve 2, the ratio of fuel injection from the second injection valve 31 decreases, and conversely, the ratio of fuel injection from the first injection valve 20 increases.

On the other hand, during acceleration from a low load, since the premixture is filled in the intake manifold 3, the premixture is sucked into the cylinder 7 without waiting until the next injection timing. This prevents the air-fuel mixture in the cylinder 7 from becoming diluted and misfiring at the beginning of acceleration.

After that, the more you press the accelerator pedal, the more
The fuel injection ratio from the first injection valve 20 increases, and a fuel amount corresponding to the engine load at that time is injected from the first injection valve 20 toward the intake valve 8. Moreover, the injection timing is during the intake stroke. In the cylinder in the intake stroke, a large flow of intake air is generated toward the cylinder 7 due to the downward movement of the piston, and the injected fuel quickly flows into the cylinder 7 riding on this intake flow. In other words, when the engine load increases, the injection valve 2 located right next to the cylinder 7
By increasing the fuel supply ratio from 0 and injecting it in time with the intake stroke, there is no delay in fuel supply, so torque builds up quickly and good acceleration is achieved. .

(Example) Figure 2 is a system diagram of an example of this invention.
Air cleaner (not shown), air flow meter 1
Air entering from the duct 1 through the intake manifold 3 is throttled by the throttle valve 2, and flows from the collector section 4 of the intake manifold 3 through the branch section 5 into the cylinder 7 of each cylinder.

In the intake port section 6, a first fuel injection valve 20 is provided facing the intake valve 8, and a second fuel injection valve 31 for injecting fuel toward the throttle valve 2 is provided immediately upstream of the throttle valve 2. The pair of injection valves 20 and 31 are driven by drive pulses from a control unit 41. Reference numeral 21 is a fuel gear that maintains a constant fuel pressure.

The air flow meter 11 may be either a flap type or a hot wire type.
The amount of intake air (Qa) measured in 1 is treated as an amount equivalent to the engine load. 12 is a crank angle sensor that outputs a signal for each unit angle of the crank angle and a signal for each reference position of the crank angle, and the signal for each unit angle is counted in the control unit 41 to determine the engine rotation speed (Ne). is measured. In other words, the crank angle sensor 12 functions as an engine rotation speed sensor. Further, from the signal for each unit angle and the crank angle reference position signal, it is determined which cylinder the engine is in and which stroke in one cycle it is in. For example, in a 4-cylinder engine, the intake stroke of the 1st cylinder is identified from the reference position signal for the 1st cylinder, and then the other cylinders (3rd, 4th, and 2nd cylinders) are identified by taking the ignition order into consideration. ) is determined by shifting the suction stroke by 180°. 13 is a sensor for detecting the cooling water temperature ( _TW ); 14 is an oxygen sensor used for feedback control of the air-fuel ratio.

The control unit 41 composed of a microcomputer includes an air flow meter 11,
Signals from the crank angle sensor 12, water temperature sensor 13, etc. are input, and based on these signals, an ignition timing control signal is output, and the operation shown in FIG. Output. in the control unit 41
In addition to data on the basic pulse width (Tp), the ROM contains data for determining the proportion (K _DIS ) of the required fuel amount to be shared by the second injection valve 31 in accordance with the engine load. Here, control unit 4
1 has the functions of means 34 to 40 in FIG.

FIG. 3 shows a routine for calculating each fuel injection pulse width (Tit and Tip) of a pair of injection valves 20 and 31.
The sharing ratio (K _DIS ) is read according to the engine load (for example, intake air amount Qa), and this K _DIS is used to determine the fuel injection pulse width (Tit) of the second injector 31 and the fuel injection pulse width (Tit) of the first injector 20. The fuel injection pulse width (Tip) is calculated using the following equations (2) and (3), respectively (steps 51 to 53).

Tit=Te×K _DIS +Ts ……(2) Tip=Te×(1−K _DIS )+Ts ……(3) Here, Te is the effective pulse width calculated by Te=Tp×COEF×α, Ts is the invalid pulse width according to the battery voltage, and is calculated in a separate routine. Note that the contents of the basic pulse width (Tp), the sum of various correction coefficients (COEF), and the air-fuel ratio feedback correction coefficient (α) are the same as before. For example, Tp is determined by referring to a table with Qa and Ne as parameters, and is equivalent to the basic injection amount.

In this way, the share of the basic fuel injection amount shared by each fuel injection valve is set in accordance with the load.

Figure 4 shows the characteristics of K _DIS (0.0≦K _DIS ≦1.0). According to the same characteristics, as can be seen from equations (2) and (3), at low load (when K _DIS = 1.0), the entire required amount of fuel is injected only from the second injection valve 31, Conversely, when the load is high (K _DIS = 0.0), only the first injection valve 20 injects. Furthermore, in the intermediate range, the smaller the engine load, the greater the injection ratio from the second injection valve 31. For this reason, during high loads, there is no difference from the conventional method, but
There is a big difference when driving other than that.

Now, when performing simultaneous injection or sequential injection in all cylinders in a multi-cylinder engine (Fig. 5) that has an injection valve only in the port section 6, the injection timing is set at a time outside the intake stroke (for example, before compression top dead center). It is said that The reason why the intake stroke is omitted is as follows. Operating conditions can be broadly divided into steady states and transient states, and ideally the engine rotation should be stable during steady states and have good responsiveness during transient states. Therefore, in order to obtain good response during transient times, it is better to inject in synchronization with the intake stroke, but on the other hand, when the load is low, the amount of fuel supplied is originally small and the combustion condition is poor. First of all, we have to make sure that the engine does not become unstable. To this end, it is desirable to inject at a time when the suction stroke is off, thereby gaining as much time as possible for the spray to form a mixture before it is sucked into the cylinder 7, and to obtain a good mixture. In other words, one injection valve has two characteristics: steady stability and transient response.
However, in conventional systems with only one injector per cylinder, steady-state stability at low loads is prioritized over transient response.

On the other hand, according to the embodiment shown in FIG.
Each cylinder is equipped with two injection valves (20, 31), and when the engine is under low load, all (or most) of the required amount of fuel is injected from the second injection valve 31 according to the characteristics shown in Fig. 4. By supplying the premixed air and forming a premixed air inside the intake manifold 3, combustion is stabilized. In other words, it can be said that the second injection valve 31 is responsible for combustion stability at low loads. Therefore, even if the injection timing of the first injection valve 20 is synchronized with the intake stroke in order to exclusively improve the transient response, it is unlikely that combustion will become unstable. On the contrary, if it is synchronized with the intake stroke, fuel can be supplied to the cylinder 7 without response delay during medium and high loads when the proportion of fuel supplied from the first injector 20 increases, and transient response is significantly improved. It will be done.

Therefore, in this embodiment, the injection timing by the first injection valve 20 is synchronized with the intake stroke regardless of the engine load. The synchronization method used is the one used in known sequential injection. That is, in a multi-cylinder engine, the cylinder is determined based on the reference position signal for the first cylinder of the crank angle sensor 12, and the fuel is injected in sequence according to the ignition order in accordance with the intake stroke of each cylinder.

Furthermore, from Fig. 4, when the engine load is below a certain value, the sharing ratio of the first injector 20 (1-K _DIS )
is zero, that is, no fuel is supplied from the first injection valve 20, so it may be configured to synchronize with the intake stroke only when the engine load exceeds a certain value.

On the other hand, regarding the injection timing by the second injection valve 31, it is conceivable to inject the fuel into several cylinders at equal intervals per cycle, taking into account fuel distribution between cylinders when the engine is under low load. When the load is low, the proportion of fuel supplied from the second injection valve 31 increases, so if the amount of fuel for all cylinders is injected only once per cycle, the fuel distribution will be uneven. Therefore, in order to supply the same concentration of air-fuel mixture to all cylinders, it is necessary to inject the mixture separately for each cylinder.

Note that asynchronous injection such as interrupt injection is not performed for any of the injection valves 20 and 31.

Next, to explain the operation of this example, first, at low engine load when a large negative pressure develops downstream of the throttle valve 2, the second injector 3 out of the required fuel amount is
1 (K _DIS ) is increased, and all (or most) of the required fuel is injected from the second injection valve 31 toward the throttle valve 2 . In this case, the speed of the air flowing around the throttle valve 2 is high, and the fuel injected from the injection valve 31 is atomized by this high-speed airflow, and further
While moving through the branch section 5, it vaporizes and mixes with the surrounding air. In other words, when the load is low, a premixture is quickly formed by using high-speed airflow.
Therefore, even if the cold time increase is not as large as in the conventional case, a good premixture can be obtained, combustion can be stabilized, and fuel efficiency can be improved. Particularly during cold starting, there is no need to inject fuel from the port 6 toward the intake valve 8.
Alternatively, since less fuel is injected, oil droplets before atomization do not adhere to the spark plug in the cylinder 7 and turn into a liquid film, improving startability.

On the other hand, when the load increases due to opening of the throttle valve 2, the second injection valve 3
The fuel injection ratio from 1 gradually decreases. This is because even if fuel is injected from the second injection valve 31 under high load, the air velocity around the throttle valve 2 decreases, making it impossible to atomize the fuel.

On the other hand, when accelerating from a low load, for example, immediately after the first injection valve 20 completes injection, the throttle valve 2
In this case, the intake manifold 3 is filled with sufficient premixture due to the action of the second injection valve 31, so immediately after acceleration, the collector section 4 , the premixture present in the branch 5 is sucked into the cylinder 7. In other words,
The fuel shortage during the time when the first injection valve 20 does not function (at the beginning of acceleration) is compensated for by the premixture stored in the intake manifold 3 during low load. This prevents the air-fuel mixture in the cylinder 7 from becoming diluted and misfiring at the beginning of acceleration.

The more the accelerator pedal is depressed, the more the fuel injection ratio from the first injection valve 20 increases, and the larger the amount of fuel in accordance with the engine load at that time, the more the fuel is injected into the first injection valve 20.
is injected from the injection valve 20 toward the intake valve 8.
Moreover, the injection timing is during the intake stroke.
In the cylinder in the intake stroke, a large flow of intake air into the cylinder 7 occurs due to the downward movement of the piston, and the injected fuel quickly flows into the cylinder 7 riding on this intake flow. Here, the second injection valve 2
0 is located right next to the cylinder 7, and since the fuel is injected into the area where the intake valve 8 is open, there is no delay in fuel supply.

If the provision for the initial stage of acceleration is to compensate for the fuel supply that tends to be insufficient at the early stage of acceleration by injection from the second injection valve 31, then when the load becomes high, the fuel supply from the first injection valve 20 is Increasing the supply rate and synchronizing the injection timing from the first injection valve 20 with the suction stroke corresponds to measures for the subsequent acceleration process. In other words, after the premixture has been burned, an amount of fuel corresponding to the load at that time immediately flows into the cylinder 7 by injection during the intake stroke where a large intake flow can be utilized, thereby requesting acceleration. This allows the torque to be increased with good response. As a result, acceleration performance is sufficiently improved, and there is no need to perform interrupt injection just because the engine is accelerating.

In addition, since fuel supply requires two contradictory roles: good steady-state stability and good transient response, the two injection valves 20,
31 (by assigning steady stability to the injection valve 31 located away from the cylinder 7, and assigning transient response to the injection valve 20 located close to the cylinder 7), both characteristics can be improved. is expected to be obtained in good condition. In other words, the second injection valve 31 is configured for premixing,
By increasing the supply ratio from this second injection valve 31 when the engine is under low load, stable drivability and startability can be obtained without significantly increasing the amount of fuel when the engine is cold.
When the engine temperature increases, acceleration performance is significantly improved by increasing the supply ratio from the first injection valve 20 and synchronizing the injection timing by the first injection valve 20 with the intake stroke.

(Effect of the invention) This invention adds a second injection valve upstream of the throttle valve in addition to the first injection valve provided at the intake port, and when the engine is under low load, fuel is supplied from the second injection valve. By performing all or most of the air supply to form a premixed mixture in the intake manifold, stable drivability and startability can be obtained when the engine is cold, and when the engine load is high, the first injector By increasing the supply ratio from the fuel injection valve and synchronizing the injection timing of the first injection valve with the intake stroke, good acceleration response can be obtained without interrupt injection.

[Brief explanation of the drawing]

Fig. 1 is a claim correspondence diagram of this invention, Fig. 2 is a system diagram of a control system of an embodiment of this invention, and Fig. 3 is a system diagram of a control system of an embodiment of this invention.
FIG. 4 is a flowchart showing the control operation of this embodiment, FIG. 4 is a characteristic diagram showing the contents of the sharing ratio K _DIS of this embodiment, and FIG. 5 is a system diagram of a conventional example. 2... Throttle valve, 3... Intake manifold, 4... Collector section, 5... Branch section, 6... Intake port section, 7... Cylinder, 11... Air flow meter, 12... Crank angle sensor, 13 ……
Water temperature sensor, 20...first fuel injection valve, 31...
... Second fuel injection valve, 32 ... Engine rotation speed sensor, 33 ... Engine load sensor, 34 ... Basic injection amount calculation means, 35 ... Sharing ratio setting means,
36, 37...Fuel injection amount calculation means, 38, 39
... Output means, 40 ... Synchronization instruction means, 41 ...
control unit.

Claims (1)

[Scope of utility model registration request] A first fuel injection valve provided in the intake port portion, a second fuel injection valve provided upstream of the throttle valve, means for calculating a basic fuel injection amount according to engine speed and engine load, and basic fuel injection means for setting the proportion of the amount to be shared by each fuel injector so that as the load decreases, the proportion of the second fuel injector to share increases; and the set proportion of share and the basic fuel injection amount. means for calculating the fuel injection amount shared by each fuel injection valve; means for outputting the calculated fuel injection amount to the corresponding fuel injection valve; and synchronization of the injection timing of the first fuel injection valve with the intake stroke. A fuel injection supply device for an engine, comprising: means for instructing an output means of the first fuel injection valve to