JPH0245026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply technology for a spark-ignition internal combustion engine, and more particularly to an electronically controlled fuel injection system for a multi-cylinder internal combustion engine.

Fuel supply methods for spark ignition internal combustion engines can be roughly divided into two types: a method using a carburetor and a method using a fuel injection valve. The latter is a relatively recently developed technology that has been attracting attention in recent years from various viewpoints including exhaust gas countermeasures. In other words, the main advantage of the fuel injection method in spark-ignition internal combustion engines is that one fuel injection valve is provided for each intake port of each cylinder, and each injection valve injects the same amount of fuel into each combustion chamber. It is possible to equalize the fuel supply amount of
The problem of fuel distribution between cylinders inherent in carburetor systems is resolved, allowing the engine to operate with a leaner combustion mixture and eliminating harmful unburned compounds such as HC and CO. The reason is that it can reduce the occurrence of living organisms. There are two types of operating methods for fuel injection valves: a continuous injection method in which fuel is continuously injected from the injector, and a pulse injection method in which fuel is injected intermittently. The latter method uses an electromagnetic fuel injection valve that is opened and closed by a solenoid.
This solenoid is generally energized by injection commands in the form of pulses from an electronic control unit containing a microcomputer. This method is called an electronically controlled fuel injection method (EFI), and the technology targeted by the present invention also belongs to this. In conventional electronically controlled fuel injection systems, the fuel injection timing is set at the same time for all fuel injection valves, that is, the fuel is injected all at once (simultaneous injection system), and the number of injections depends on each engine operation. Once or twice per cycle.

On the other hand, in today's engines, whether fuel-injected or carburetor-based, the intake port profile is generally relatively large in diameter and straight in order to maximize power output during high-load, high-speed operation. Designed to have a shape with low ventilation resistance. However, when the intake port is shaped like this, sufficient turbulence is not generated in the air-fuel mixture sucked into the combustion chamber during low-speed, low-load operation and low-speed, high-load operation, which increases the flame propagation speed. I can't. Methods for generating strong turbulence in the intake air-fuel mixture during low-speed, low-load operation include creating a helical intake port or using a shroud valve to forcefully generate a swirling flow within the combustion chamber. However, these methods have a problem in that the charging efficiency during high-speed, high-load operation decreases because the ventilation resistance to the intake air mixture increases. Therefore, in a carburetor type engine, a second intake throttle valve is individually provided in each intake passage in each branch pipe of the intake manifold downstream of the main intake throttle valve, and a second intake throttle valve is individually provided in each intake passage in each branch pipe of the intake manifold, and a second intake throttle valve is installed in each intake port of each cylinder near the intake valve. Each cylinder is provided with a small-diameter jet port that opens into the cylinder, and the jet ports are communicated with each other through a common communication pipe, so that when a certain cylinder enters the intake stroke during low-speed operation of the engine, the jet port enters the intake stroke. Intake air is induced from the intake ports of other cylinders that are currently in the intake stroke, and the air is jetted from the jet ports to the intake ports of the cylinders that are in the intake stroke, thereby generating strong turbulence in the combustion chamber, thereby causing a strong turbulent flow during low-speed operation. It has been proposed to secure output during high-speed operation while improving combustion of the engine (Japanese Patent Laid-Open No. 55-25547). For convenience, this method will be abbreviated as the forcible attraction turbulence generation method hereinafter.

By the way, when applying the above forced turbulence generation method to an engine with a conventional carburetor, the jet port is located downstream of the main throttle valve of the carburetor, and a homogeneous air-fuel mixture is formed in the carburetor. Even if the air-fuel mixture is divided into each jet port, the fuel distribution between the cylinders will not deteriorate. However, when a fuel injection method that simultaneously injects fuel into each branch pipe of the intake manifold or individual intake ports is combined with the above-mentioned forced turbulence generation method, the fuel distribution between the cylinders deteriorates and the induced turbulence There was a problem in that the combustion improvement effect was attenuated by the fluctuations in the air-fuel ratio between cylinders, resulting in increased engine torque fluctuations.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a fuel supply device that does not cause deterioration in fuel distribution even when an electronically controlled fuel injection system is combined with the above-mentioned forcibly induced turbulent flow generation method. This ensures output during high-speed, high-load operation, prevents torque fluctuations during low-speed, low-load operation, and low-speed, high-load operation, and enables the engine to operate with a leaner combustion mixture. The aim is to improve fuel efficiency and reduce harmful exhaust gas components.

According to the present invention, the above deterioration in fuel distribution is caused by fuel that is injected simultaneously at a certain time and remains in the intake port of each cylinder, and when a certain cylinder enters the intake stroke, it circulates through the jet port and the communication pipe. This is based on the knowledge that this is due to the fact that the amount of fuel sucked into that cylinder and as a result, the amount of fuel sucked into the other cylinders that subsequently enter the intake stroke sequentially decreases gradually. A second intake throttle valve is provided in each intake passage downstream of the main intake throttle valve of the internal combustion engine, and a small diameter jet port that opens into the intake port of each cylinder near the intake valve is provided for each cylinder. The jet ports are communicated with each other through a common communication pipe, and the second intake throttle valve is almost fully closed.When the engine is operated at low speed, when a certain cylinder is in the suction stroke, other cylinders are not in the suction stroke. The intake air is induced from the intake ports of the cylinders so that the intake air is jetted from the jet ports to the intake ports of the cylinders in the intake stroke, and the second intake throttle valves in the intake ports of each cylinder A fuel injection valve is provided for each cylinder so as to open between the opening of the jet port, and the fuel injection valve of each cylinder is configured to operate sequentially according to the ignition order of each cylinder. The present invention proposes an electronically controlled fuel injection device for a multi-cylinder internal combustion engine characterized by the following features.

Hereinafter, embodiments will be described with reference to the accompanying drawings.

FIG. 1 is a diagram showing the overall arrangement of an engine equipped with an electronically controlled fuel injection system according to the present invention, and FIG. 2 is a sectional view taken along the line taken from FIG. 1. The figure shows a four-cylinder engine, and as is well known, cylinder bore 2a
A cylinder head 6 equipped with a valve train and an intake/exhaust port is mounted on the cylinder block 4 forming the cylinder bore 2, and a cylinder head 6 is provided between the cylinder bore 2, the piston 8 that reciprocates therein, and the cylinder head 6. A combustion chamber 10 is formed. An intake manifold 12 and a surge tank 14 are sequentially fixed to the side surface of the cylinder head 6, and the intake manifold 12 has a base 13 that contacts the cylinder head 6.
and four branch pipes 15a to 15 extending from the base.
It consists of d. An air cleaner 16 is used for intake air, and an air flow meter 1 is used to measure intake air flow rate.
8. The air is introduced into the surge tank 14 through the throttle body 22 equipped with the throttle valve 20, and from there is inhaled into the combustion chamber 10 via the intake manifold 12 and through the intake port 24 formed in the cylinder head 6. It's summery. 26 is a well-known electronic control unit (ECU) with a built-in microcomputer, which receives the intake air amount signal from the air flow meter 18, the intake temperature signal from the intake air temperature sensor 28 provided in the air flow meter, and the signal from the throttle position sensor 30. , a signal from the cooling water temperature sensor 32, a signal from an engine rotation speed sensor (not shown), etc. are inputted to calculate the fuel injection amount and output a fuel injection command signal. Each fuel injection valve 34 is supplied with fuel from a fuel pump (not shown) via a fuel hose 36 and a delivery pipe 38. The fuel injection valve 34 is a known electromagnetic injection valve having a solenoid, and injects fuel toward the intake port 24 in response to an injection command signal from the electronic control unit 26.

Each intake manifold branch pipe 15 is provided with a second intake throttle valve 40a to 40d, which are linked by a common shaft 42. The shaft 42 is linked, for example, to an accelerator pedal (not shown), and is configured to rotate the second throttle valve 40 to substantially block the main air passage in the branch pipe 15 during low load operation of the engine. It's summery. On the other hand, in the cylinder head 6, small-diameter jet ports 44a to 44d are formed approximately parallel to the intake port 24 for each cylinder. These jet ports are
As is clear from the cross section shown in the figure and the dotted line in FIG. 1, the intake port 24 opens near the terminal end in a direction approximately tangential to the periphery of the intake valve 46, and air flows through these ports. When injected from the jet port 44, strong turbulence is generated within the combustion chamber. Each jet port 44 communicates with one another by a longitudinally extending communication passage 48 (see FIG. 2) formed in the base 13 of the intake manifold 12. With such a configuration, the second throttle valves 40a to 4 are closed during low speed operation of the engine.
When a certain cylinder enters the intake stroke when 0d is fully closed, the jet port 44 of that cylinder receives air from the other cylinder via the communication passage 48 and the jet port of the other cylinder that is not in the intake stroke. The air-fuel mixture is drawn from the intake port and is ejected from the jet port to the intake port of the cylinder that is on the intake stroke. Therefore, strong turbulence occurs within the combustion chamber of that cylinder. This relationship holds true even when the other cylinders sequentially enter their intake strokes. At the bottom of FIG. 1, the reference number 50 indicates a distributor, and its rotating shaft has a star-shaped ignition pulse generation rotor with eight protrusions and a cylinder discrimination rotor with one protrusion. On the other hand, an ignition pulse detection sensor 52 and a cylinder discrimination sensor 54 are installed in the housing of the distributor 50 at positions corresponding to the respective rotors.

In accordance with the present invention, each fuel injector 34a-34d is operated sequentially by an injector drive circuit 56 according to the firing order. FIG. 3 is a block diagram of an electronically controlled fuel injection system including this injection valve drive circuit 56, in which the ignition pulse detection sensor 52 of the distributor 50 (see FIG. 1) is connected via a waveform shaper 58 and a flip-flop 60. It is connected to one input terminal of the electronic control unit 26 and the shift register 62. On the other hand, data streamer 5
The cylinder discrimination sensor 54 provided at 0 is connected to the other input terminal of the shift register 62 via another waveform shaper 64. Fuel injection command signal output section of electronic control unit 26 and shift register 62
The output portions of are connected to the input portions of AND gates 66a to 66d, respectively. Each AND gate 66a~
66d is a transistor 68a to 68 via a resistor.
connected to the base of d. Each transistor 6
Collectors 8a to 68d are connected to a power source via solenoids 70a to 70d of each fuel injection valve, and emitters are grounded. In addition, solenoid 70
a is for the first cylinder, 70b is for the second cylinder, 70
c corresponds to the third cylinder, and 70d corresponds to the fourth cylinder.

Next, the operation of this electronically controlled fuel injection system will be explained with reference to the drawings from FIG. 4 onwards. As the ignition pulse generation rotor of the distributor 50 rotates in conjunction with the crankshaft of the engine, the ignition pulse detection sensor 52 outputs an electrical signal. This electrical signal is shaped by a waveform shaper 58 to obtain the pulse signal shown in FIG. 4a. This pulse signal is divided by the flip-flop 60 to obtain the pulse signal shown in FIG. 4b, which is input to one terminal of the shift register 62. A signal from the cylinder discrimination sensor 54 is input as a shift pulse to the other terminal of the shift register. Therefore, the pulse signals of FIG. 4b are sequentially shifted to the right, and the shift register 62 outputs to each AND gate 66 one of the corresponding pulse signals c to f of FIG. On the other hand, as is well known, the electronic control unit 26 determines the injection amount based on the signal from the air flow meter 18 and the ignition signal, and outputs the fuel injection command signal shown in FIG. 4g to the AND gate 66. . Therefore, each AND gate 66a-66d corresponds to the pulses c-f in FIG.
A signal of "1" is output only when the pulses overlap. Triggered by this output signal, the collector and emitter of each transistor are brought into conduction, and current flows through the solenoids 70a to 70d of the fuel injection valve, injecting fuel. In Figure 3, the solenoids of the fuel injection valves correspond to those of the first, third, fourth, and second cylinders from the top, and since each cylinder is ignited in this order, fuel injection is also performed in the ignition order. This will be done in accordance with. This condition will be clear from the injection timing chart in FIG. 5, which is shown in comparison with the conventional method.

Fig. 5a shows a conventional system in which fuel is injected to all cylinders at the same time at 360° intervals, but in the illustrated embodiment of the present invention, the fifth
As shown in Figure b, by sequentially operating the fuel injection valves of each cylinder at 180° intervals according to the ignition order of each cylinder, it is possible to synchronize the intake stroke and fuel injection timing of each cylinder. There is.

When the above-mentioned forcibly induced turbulent flow generation method is combined with a conventional electronically controlled fuel injection system, the cylinders into which the fuel circulates through the jet ports and communication passages (crank angles of 180° and 540° as shown in Figure 5a) , 900°, where the intake stroke occurs within a period of approximately 180° from the start of fuel injection), and cylinders where fuel does not circulate (such as the crank angles of 360° and 720° illustrated in Figure 5a). The air-fuel ratio with the cylinder (in which the intake stroke comes after approximately 180° or more from the start of fuel injection) is 6th.
There were fluctuations as shown in Figure a. The present invention sequentially operates the fuel injection valves of each cylinder according to the ignition order, so when a certain cylinder is in the intake stroke, the air-fuel mixture coming from the intake port of the other cylinder via the jet port and the communication passage is The conditions are the same for all cylinders. Therefore, the air-fuel ratio of each cylinder becomes uniform as shown in FIG. 6b, and torque fluctuations can be minimized during low-speed, low-load operation and during low-speed, high-load operation.

[Brief explanation of drawings]

Figure 1 is an overall layout of a four-cylinder engine equipped with an electronically controlled fuel injection system, and Figure 2 is the same as in Figure 1.
Figure 3 is a block diagram of the injection valve drive circuit, Figure 4 is a waveform diagram showing changes in pulse signals over time, Figure 5 is an injection timing chart, and Figure 6 is a graph comparing air-fuel ratio fluctuations. be. 12... Intake manifold, 15... Intake manifold branch pipe, 20... Throttle valve, 24... Intake port, 26... Electronic control unit, 34... Fuel injection valve, 40... Second intake throttle valve, 44... Jet port, 48 ...Communication path, 56...Injection valve drive circuit, 60
...Flip-flop, 62...Shift register, 6
6...AND gate, 68...transistor, 70...
Fuel injection valve solenoid.

Claims (1)

[Claims] 1 A second intake throttle valve is provided in each intake passage downstream of the main intake throttle valve of a multi-cylinder internal combustion engine, and a small diameter jet port that opens into the intake port of each cylinder is provided for each cylinder near the intake valve. , the jet ports are communicated with each other by a common communication pipe,
When the second intake throttle valve is substantially fully closed during low-speed operation of the engine, when a certain cylinder enters the intake stroke, intake air is induced from the intake ports of other cylinders that are not in the intake stroke to complete the intake stroke. The intake air is ejected from the jet port to the intake port of the cylinder located in the cylinder, and each cylinder is configured to open between the second intake throttle valve in the intake port of each cylinder and the opening of the jet port. Electronically controlled fuel for a multi-cylinder internal combustion engine, characterized in that fuel injection valves are provided for each cylinder, and the fuel injection valves of each cylinder are configured to operate sequentially according to the ignition order of each cylinder. Injection device.