JPH0127260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for an engine.

Generally, a fuel injection device includes a fuel injection valve in the intake passage, and controls the opening time of the fuel injection valve using a pulse signal output from a control circuit depending on the operating state, thereby controlling the fuel injection amount. ing. In this case, in the case where the fuel injection amount is controlled by one fuel injection valve over the entire operating range of the engine, the fuel injection valve is Since the opening area of the fuel cell must be increased to a certain extent, there is a problem in that fuel control during light load operation is difficult.

As a countermeasure to this problem, as seen in Japanese Patent Application Laid-Open No. 54-53718, a first fuel injection valve (main fuel injection valve) that injects fuel in the entire operating range of the engine,
By providing a second fuel injection valve (auxiliary fuel injection valve) that injects fuel during high-load operation, the required fuel supply amount during high-load operation is satisfied, and the opening area of the first fuel injection valve is compared. There is a known system that improves the accuracy of fuel control in light load operating ranges by making the target smaller. By the way, in general fuel injection devices, there is a known method for promoting atomization of fuel by providing an air bleed passage that supplies air from the intake passage upstream of the throttle valve to the vicinity of the injection port of the fuel injection valve. When this is applied to a fuel injection device having the first and second fuel injection valves described above, a structure in which an air bleed passage is provided for each of the two fuel injection valves can be considered. However, according to this structure, during light load operation when the amount of intake air is originally small and atomization is difficult to occur, air bleed air is also distributed to the second fuel injection valve where fuel injection is not performed, so the fuel There was a drawback that the amount of air supplied to the first fuel injection valve where injection was being performed was insufficient, and a sufficient fuel atomization promotion effect could not be obtained.

In addition, when the above-mentioned first and second fuel injection valves are arranged in the intake passage, the responsiveness of the fuel (the time until the fuel is drawn into the combustion chamber) at light load when the intake air amount is small and the intake air flow rate is slow. In order to prevent this from worsening, it is desirable to place the first fuel injector, which is used for fuel supply during light loads, downstream of the second fuel injector. In particular, since the distance from the first fuel injection valve to the combustion chamber becomes short and sufficient atomization is not performed during this distance, the above-mentioned drawbacks become noticeable when there is insufficient air for air bleed.

In view of these circumstances, the present invention promotes atomization of the fuel injected from the first fuel injection valve during light load operation in an engine equipped with first and second fuel injection valves, and improves the atomization of the fuel injected from the first fuel injection valve during light load operation. The present invention provides a fuel injection device that can improve performance.

That is, the present invention provides at least a first fuel injection valve that injects fuel during light load operation and a second fuel injection valve that injects fuel during high load operation, with the first fuel injection valve located downstream of the second fuel injection valve. In an engine provided in an intake passage such that a fuel injection valve is located, an air bleed passage is provided for sending air bleed air to each of the fuel injection valves, and
By providing an air bleed control device that controls air supply from the air bleed passage so that air bleed air is supplied only to the first fuel injection valve during light load operation, sufficient atomization can be achieved even during light load operation. This is done so that

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an engine body, 2 is an intake passage, 3 is an exhaust passage, and 4 is a throttle valve provided in the intake passage 2. In FIG. Intake passage 2 downstream from throttle valve 4
A first fuel injection valve 5 that injects fuel in the entire operating range of the engine from light load to high load, and a second fuel injection valve 6 that injects fuel during high load operation are disposed. The first fuel injection valve 5 is provided downstream of the second fuel injection valve 6 as shown in the figure in order to improve the responsiveness of fuel supply during light loads.
In other words, it is provided at a position relatively close to the combustion chamber of the engine body 1.

Each of the fuel injection valves 5 and 6 is controlled by a control circuit 20. The control circuit 20 receives an intake air flow rate detection signal from an air flow meter 7 provided in the intake passage 2 upstream of the throttle valve 4, an ignition signal obtained from an ignition signal generator 8, and a signal from a throttle valve opening sensor 9. A throttle valve opening detection signal is input.

Also, as an air bleed passage, a first air bleed passage 11 for supplying air to the first fuel injection valve 5 is provided.
and a second air bleed passage 12 for supplying air to the second fuel injection valve 6, and an on-off valve 13 that opens and closes the second air bleed passage 12 under the control of the control circuit 20. There is. The on-off valve 13 and the control circuit 20 constitute an air bleed control device that controls air supply so that air bleed air is supplied only to the first fuel injection valve 5 during light load operation.

One end of the first air bleed passage 11 is connected to the intake passage 2 between the air flow meter 7 and the throttle valve 4, and the other end opens near the injection port of the first fuel injection valve 5. Said second air bleed passage 12
is branched from the first air bleed passage 11 and opens near the injection port of the second fuel injection valve 6,
An on-off valve 13 is provided in this second air bleed passage 12 . The control circuit 20 closes the on-off valve 13 during light load operation and opens it during high load operation. Note that 14 is an air cleaner connected to the upstream end of the intake passage 2.

The control circuit 20 is configured as shown in FIG. That is, in this control circuit 20, the engine rotation speed is detected by the rotation speed detection circuit 21 which receives the ignition signal from the ignition signal generating section 8, and the intake air flow rate detection signal from the air flow meter 7 and the above-mentioned ignition signal are detected. The rotation speed detection signal from the rotation speed detection circuit 21 is connected to the injection pulse generation circuit 22.
has been entered. This injection pulse generation circuit 22
This generates an injection pulse for fuel injection valve control. Based on the intake air flow rate detection signal and rotation speed detection signal, the pulse width is determined according to the intake air amount per engine revolution, and the pulse width is determined based on the intake air flow rate detection signal and the rotation speed detection signal. Based on this, an injection pulse is generated at a predetermined timing. A drive circuit 23 for the first fuel injector 5 is connected to the output side of the injection pulse generation circuit 22, and a drive circuit 23 for the first fuel injection valve 5 is connected to the output side of the injection pulse generation circuit 22. A drive circuit 25 for the two fuel injection valves 6 is connected. On the other hand, the rotation speed detection circuit 21
A reference voltage generation circuit 26 receives a rotation speed detection signal from the engine and generates a reference voltage according to the engine rotation speed.
and a comparison circuit 27 that compares the throttle valve opening detection signal from the throttle valve opening sensor 9 with the reference voltage, so that the throttle valve opening is larger than a reference value predetermined in association with the engine rotation speed. When the temperature drops, a fuel injection state switching signal is generated on the output side of the comparison circuit 27. The switching circuit 24 is controlled by the output of the comparison circuit 27 to cut off the injection pulse when the switching signal is not generated, and to conduct the injection pulse when the switching signal is generated. The output of the comparison circuit 27 is also input to the injection pulse generation circuit 22, and the output of the comparison circuit 27 is inputted to the injection pulse generation circuit 22 according to the switching signal in order to adjust the total fuel supply amount when the second fuel injection valve 6 is operated. A circuit is built in to correct the pulse width of the injection pulse. Further, the output of the comparison circuit 27 is also sent to the on-off valve 13, so that when the switching signal is not generated, the on-off valve 13 is closed, and only when the switching signal is generated, the on-off valve 13 is opened.

In this fuel injection system, only the first fuel injection valve 5 is operated during light load operation when the throttle valve opening detected by the throttle valve opening sensor 9 is below the reference voltage. In this case, fuel is injected from the first fuel injection valve 5 by the injection pulse from the injection pulse generation circuit 22 via the drive circuit 23 at a predetermined timing according to the ignition signal for a time corresponding to the pulse width of the injection pulse. Injected. That is, the fuel injection amount is controlled by controlling the pulse width of the injection pulse according to the amount of intake air per rotation of the engine. In addition, during this light load operation, by closing the on-off valve 13, the supply of air bleed air to the second fuel injection valve 6 which is in an inoperable state is cut off, and only to the first fuel injection valve 5. , air flow meter 7 and throttle valve 4
from the intake passage 2 to the first air bleed passage 1 between
Air is supplied through 1. As a result, during light load operation when the amount of intake air including air bleed air is limited, compared to the case where air bleed air is distributed and supplied to both the first and second fuel injection valves, The amount of air bleed air supplied to each fuel injection valve 5 can be increased, and the effect of promoting fuel atomization can be enhanced.

During high-load operation when the throttle valve opening is equal to or higher than the reference voltage, the switching circuit 24 is switched to a state in which the injection pulse is conducted by the switching signal output from the comparison circuit 27, and the injection pulse generation circuit is switched to a state where the injection pulse is conducted. At step 22, the pulse width of the injection pulse is corrected, and the first and second fuel injection valves 5, 6 are actuated by the injection pulse via both drive circuits 23, 25. Therefore, the fuel injection amounts of both fuel injection valves 5 and 6 are controlled so as to satisfy the required fuel supply amount during high-load operation. Also, during this high-load operation, the on-off valve 13 is opened by the switching signal, so that air is distributed and supplied to both the fuel injection valves 5 and 6 through the first and second air bleed passages 11 and 12, respectively. In this case, since the amount of intake air is large, atomization of the fuel is sufficiently promoted.

In addition, as another example of the control means for both the fuel injection valves 5 and 6, the first fuel injection valve 5 is connected to the second fuel injection valve 6.
By using a fuel injector with a larger opening area, during high-load operation, the second fuel injector is injected while the first fuel injector 5 is stopped.
The fuel injection valve 6 may also be operated. Further, in the above embodiment, both fuel injection valves 5 and 6 are arranged in one intake passage 2, but the intake passage is divided into a primary passage and a secondary passage, and the first fuel injection valve is separately provided in these passages. An injection valve and a second fuel injection valve may be provided.

As described above, in the present invention, the first and second fuel injection valves are arranged in the intake passage so that the first fuel injection valve is located on the downstream side, and only the first fuel injection valve is used during light load operation. In a device configured to inject fuel from the first fuel injection valve, air bleed passages are provided for both fuel injection valves, and the air bleed is controlled so that air bleed air is supplied only to the first fuel injection valve during light load operation. Therefore, during light load operation with a small amount of intake air, the amount of air supplied to the first fuel injector is reduced to avoid dispersing the air for air bleed from the second fuel injector where fuel injection is not performed. can be increased. In other words, it is possible to enhance the air bleed effect when the amount of intake air is small and atomization is difficult to achieve, and to significantly enhance the effect of promoting fuel atomization.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the apparatus of the present invention, and FIG. 2 is a block diagram showing a control circuit. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake passage, 5... First fuel injection valve, 6... Second fuel injection valve, 11... First air bleed passage, 12... Second air bleed passage, 1
3...Opening/closing valve, 20...Control circuit.

Claims (1)

[Claims] 1 At least a first fuel injection valve that injects fuel during light load operation and a second fuel injection valve that injects fuel during high load operation are arranged such that the first fuel injection valve is located downstream of the second fuel injection valve. In an engine provided in the intake passage, an air bleed passage is provided to send air bleed air to each of the two fuel injection valves, and air bleed air is sent only to the first fuel injection valve during light load operation. A fuel injection device for an engine, comprising an air bleed control device that controls air supply from the air bleed passage so as to supply air from the air bleed passage.