JPH0245029B2 - - 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. Because it is possible to equalize the fuel supply 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. Such a method is called an electronically controlled fuel injection method (EFI), and the technology to which the present invention is directed 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.
Unable to increase flame propagation velocity. Methods of 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 forcibly 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 main throttle valve that is artificially operated in the main intake passage and an auxiliary throttle valve that is located downstream of the main throttle valve and is fully closed only at low load are installed. A main intake passage between the and the auxiliary throttle valve is led to a communication pipe by a pipe, and a sub-intake passage branch pipe that opens near the intake port is branched from the communication pipe, and the pipe and the communication passage are connected to each other. A sub-intake passage that bypasses the auxiliary throttle valve is formed with the pipe, and when the load is low, the auxiliary throttle valve is closed or slightly closed, and a strong mixture jet is ejected from the auxiliary intake passage to prevent turbulence from occurring in the combustion chamber. It has been proposed to prevent a decrease in output by minimizing intake resistance by fully opening the main intake passage during high loads while promoting combustion improvement (Japanese Patent Application Laid-Open No. 137320/1983). In this specification, for convenience, this method will be abbreviated as a sub-intake passage type turbulence generation method.

By the way, when applying the above auxiliary intake passage type turbulence generation system to an engine with a conventional carburetor, the branch pipe of the auxiliary intake passage is located downstream of the main throttle valve of the carburetor, and a homogeneous flow is generated in the carburetor. Since the air-fuel mixture is formed, even if the air-fuel mixture is divided into the branch pipes of the auxiliary intake passage, fuel distribution between the cylinders will not deteriorate. However, when the fuel injection method in which fuel is simultaneously injected into each branch pipe of the intake manifold or each intake port is combined with the auxiliary intake passage type turbulence generation method,
There was a problem in that the fuel distribution between the cylinders deteriorated, and the combustion improvement effect of the auxiliary intake passage was offset by the fluctuations in the air-fuel ratio between the cylinders, resulting in an increase in engine torque fluctuations.

The present invention aims to eliminate the above-mentioned problems, and provides a fuel supply device that does not deteriorate fuel distribution even when an electronically controlled fuel injection system is combined with the above-mentioned auxiliary intake passage type turbulence generation method. By doing so, it secures output during high-speed, high-load operation, prevents torque fluctuations during low-speed, low-load operation, and enables the engine to operate with a lean combustion mixture, improving fuel efficiency. The purpose is to reduce harmful exhaust gas components.

According to the present invention, the above-mentioned deterioration in fuel distribution is caused by fuel remaining in the intake ports of each cylinder that has been injected at the same time at a certain time flowing around through a communication pipe when a certain cylinder enters its intake stroke. The present invention is based on the knowledge that this is due to the fact that the amount of fuel sucked into a cylinder gradually decreases as a result of the amount of fuel sucked into other cylinders that subsequently enter the intake stroke, and the present invention aims to prevent such a situation. , an auxiliary intake throttle valve that is substantially fully closed during low-load operation is provided in the intake passage of each cylinder downstream of the main intake throttle valve of the multi-cylinder internal combustion engine, and between the main intake throttle valve and the auxiliary intake throttle valve. A sub-intake passage is formed by connecting jet ports that branch from the intake passage section of the engine and bypass the auxiliary intake throttle valve and open near the intake valves of each cylinder to form an auxiliary intake passage. When in the intake stroke, intake air is induced from the intake passages of other cylinders not in the intake stroke through the auxiliary intake passage, and the intake air is jetted from the jet port to the intake passage of the cylinder in the intake stroke, Further, a fuel injection valve for each cylinder is provided so as to open between the auxiliary intake throttle valve in the intake passage of each cylinder and the opening of the jet port, and the fuel injection valve for each cylinder is electronic control for a multi-cylinder internal combustion engine, characterized in that the engine is divided into two groups each having half the number of cylinders, and the fuel injection valves of each group are configured to operate at predetermined ignition timing intervals according to the ignition order. This paper proposes a type fuel injection system.

Embodiments will be described below 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 the cylinder head 6 is connected between the cylinder bore 2, the piston 8 that reciprocates therein, and the cylinder head 6. A combustion chamber 10 is formed in the combustion chamber 10 . cylinder head 6
An intake manifold 12 and a surge tank 14 are sequentially fixed to the side surface of the intake manifold 12, and the intake manifold 12 has an integral flange 13 that contacts the cylinder head 6 and the surge tank 14, respectively, and four intermediate branch pipes 15a to 15d. Consists of. Intake air is led to a surge tank 14 via an air cleaner 16, an air flow meter 18 for measuring the intake air flow rate, and a throttle body 22 equipped with a throttle valve 20, and from there is formed in the cylinder head 6 via an intake manifold 12. The air is sucked into the combustion chamber 10 through an intake port 24 which has been opened. Reference numeral 26 denotes a well-known electronic control unit (ECU) with a built-in microcomputer, which controls the intake air amount signal from the air flow meter 18, the intake air temperature signal from the intake temperature sensor 28 provided in the air flow meter, and the throttle position provided in the throttle body 22. It inputs signals from the sensor 30, the coolant temperature sensor 32, the engine rotation speed sensor (not shown), etc., calculates the fuel injection amount, and outputs the fuel injection command signal. be. Fuel injection valves 34a to 34d are installed in the intake manifold 12 for each cylinder. 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 is controlled by the electronic control unit 2.
The fuel is injected toward the intake port 24 in response to an injection command signal from 6.

Each intake manifold branch pipe 15 is provided with auxiliary throttle valves 40a to 40d, which are linked by a common shaft 42. shaft 42
is linked to the output shaft of the diaphragm device 44, and when the engine is operating at low load, the auxiliary throttle valve 4 is
0 can be rotated to substantially block the main air passage within the branch pipe 15. On the other hand, in the cylinder head 6 and the intake manifold 12, small-diameter jet ports 46a to 46d are formed for each cylinder, substantially parallel to the intake passage. As is clear from the cross section shown in FIG. 2 and the dotted line in FIG. These jet ports are open so that when air is drawn in through these jet ports, turbulence or swirl is generated within the combustion chamber. Each of the jet ports 46 communicates with each other through a communication pipe 50 formed at the bottom of the surge tank 14.
This communication pipe 50 is connected to the auxiliary throttle valve 4 through an opening 52.
0 is bypassed and communicated with the inside of the surge tank 14. Opening 52, communication pipe 50, jet port 46
a to 46d constitute a sub-intake passage. With this configuration, when the auxiliary throttle valves 40a to 40d are fully closed during low-load operation of the engine, intake air is supplied exclusively from the auxiliary intake passage, causing turbulence within the combustion chamber. The number 56 shown at the bottom of Figure 1 is a distributor, and its rotating shaft has a star-shaped ignition pulse generation rotor with four protrusions and a cylinder discrimination rotor with one protrusion. On the other hand, an ignition pulse detection sensor 58 and a cylinder discrimination sensor 60 are installed in the housing of the distributor at positions corresponding to the respective rotors.
is installed.

According to the present invention, each fuel injector 34a-34d is configured, for example, by combining odd-numbered cylinders and even-numbered cylinders into one group, and by combining four cylinders into two groups.
into two groups. That is, the fuel injection valve 34a of the first cylinder and the fuel injection valve 34d of the fourth cylinder counted from the front of the engine, that is, from the right side of FIG. The injection valves 34b and 34c are grouped. These two groups of injection valves are operated by the injection valve drive circuit 62 at predetermined ignition timing intervals according to the ignition order.

FIG. 3 is a block diagram of an electronically controlled fuel injection system including this injection valve drive circuit 62, in which the ignition pulse detection sensor 58 (see FIG. 1) of the distributor 56 is connected via a waveform shaper 64 and a flip-flop 66. It is connected to one input terminal of electronic control unit 26 and shift register 68. On the other hand, the cylinder discrimination sensor 60 provided in the distributor 56 is connected to the other input terminal of the shift register 68 via another waveform shaper 70. The fuel injection command signal output section of the electronic control unit 26 and the output section of the shift register 68 are
They are connected to the inputs of AND gates 72 and 72', respectively. Each AND gate 72, 72' is connected to the base of a transistor 74, 74' via a resistor. The collector of each transistor 74, 74' is connected to a power source via a solenoid 76a-76d of each fuel injection valve, and the emitter is grounded. Note that the solenoid 76a is connected to the No. 1 cylinder.
6b is for the second cylinder, 76c is for the third cylinder, 7
6d corresponds to the fuel injection valve of 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 56 rotates in conjunction with the crankshaft of the engine, the ignition pulse detection sensor 58 outputs an electrical signal. This electrical signal is shaped by a waveform shaper 64 to obtain the pulse signal shown in FIG. 4a. This pulse signal is frequency-divided by a flip-flop 66 to obtain the pulse signal shown in FIG. A signal from the cylinder discrimination sensor 60 is input as a shift pulse to the other terminal of the shift register. Therefore, the pulse signal of FIG. 4b is sequentially shifted to the right, and the shift register 68 outputs the corresponding pulse signal of either FIG. 4c or d to each AND gate 72, 72'. On the other hand, the electronic control unit 26 controls the air flow meter 18 as is well known.
The injection amount is determined by the signal from the ignition signal and the ignition signal.
A fuel injection command signal shown in FIG. 4e is outputted to the AND gates 72 and 72'. Therefore, each AND gate 72, 72' outputs a signal of "1" only when the pulses c and d in FIG. 4 overlap with the pulses e in the same figure. Triggered by this output signal, the collector and emitter of each transistor 74, 74' become conductive, and current flows through the solenoids 76a to 76d of the fuel injection system of each group to inject fuel. When the transistor 74 is conductive, the injection valves 34 of the group, that is, the first and fourth cylinders
When the injectors a and 34d are activated and the transistor 74' is conductive, the injection valves 34b and 34c of the group, that is, the second and third cylinders are activated. This condition will be clear from the injection timing chart in FIG. 5, which is shown in comparison with the conventional method. Fifth
Figure a 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, as shown in Figure 5b, The two groups are operated alternately at 180° intervals, and each fuel injection valve injects one-half of the fuel injection amount for one cycle at a rate of once per crankshaft revolution. .

When the conventional electronically controlled fuel injection system is combined with the auxiliary intake passage type turbulence generation system, the cylinders (crank angle 180 as shown in FIG. cylinders whose intake stroke occurs within a period of approximately 180° from the start of fuel injection, such as cylinders with a crank angle of 360°, 540°, and 900°; The air-fuel ratio with a cylinder whose intake stroke comes after a period of approximately 180° or more after the start of fuel injection, such as 720°, is
There were fluctuations as shown in Figure 6a. In the present invention, the fuel injection valves of each cylinder are divided into two groups, and the fuel injection valves of each group are operated at predetermined ignition timing intervals according to the ignition order, so that the air-fuel mixture flow circulating through the communication pipe 50 contributes. is the same condition 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-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... Branch pipe of intake manifold, 20... Throttle valve,
24...Intake port, 26...Electronic control unit, 34...Fuel injection valve, 40...Auxiliary throttle valve,
46... Jet port, 48... Intake valve, 50...
Communication pipe, 52...Opening, 62...Injection valve drive circuit, 66...Flip-flop, 68...Shift register, 72...AND gate, 74...Transistor, 76...Injection valve solenoid.

Claims (1)

[Claims] 1. An auxiliary intake throttle valve that is almost fully closed during low-load operation is provided in the intake passage of each cylinder downstream of the main intake throttle valve of a multi-cylinder internal combustion engine, and an auxiliary intake throttle valve is provided between the main intake throttle valve and the auxiliary intake throttle valve. A sub-intake passage is formed by connecting jet ports that branch from the intake passage section of the engine and bypass the auxiliary intake throttle valve and open near the intake valves of each cylinder to form an auxiliary intake passage. When the engine enters the intake stroke, intake air is induced through the auxiliary intake passage from the intake passages of other cylinders that are not in the intake stroke, and the intake air is jetted from the jet port to the intake passage of the cylinder that is in the intake stroke; Further, a fuel injection valve for each cylinder is provided so as to open between the auxiliary intake throttle valve in the intake passage of each cylinder and the opening of the jet port, and the fuel injection valve for each cylinder is electronic control for a multi-cylinder internal combustion engine, characterized in that the engine is divided into two groups each having half the number of cylinders, and the fuel injection valves of each group are configured to operate at predetermined ignition timing intervals according to the ignition order. type fuel injection device.