JPS637260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for a small displacement multi-cylinder engine employing a supercharger and a fuel injector. The purpose is to be able to control the air-fuel ratio even when the required fuel flow rate is small, and to obtain large output through supercharging.

This type of supercharged engine employs an electronically controlled fuel injection system, in which the period during which the injector is open is controlled by pulses using a solenoid valve. However, there is a lower limit to the effective pulse width required to open the injector. That is, if the pulse width is lowered below the lower limit value in order to obtain a minute injection amount, air-fuel ratio control becomes impossible. Therefore, there is a lower limit to the amount of fuel injected per injection, and it is difficult to reduce the injection amount below this limit when using existing injectors. Therefore, when the required fuel flow rate is small, such as during idling in an engine with a small displacement per cylinder, the conventional method of providing one injector for each cylinder results in an excessive injection amount, making it difficult to control the air-fuel ratio. becomes impossible. To explain this with reference to FIG. 1, each intake manifold 2 connected to each cylinder of a four-cylinder engine 1 has one
There are two injectors 3 and a throttle valve 4, and the injector 3 injects each cylinder at its top dead center. 5 is an equalizer tube, 6 is an intake pipe communicating with the compressor of the supercharger, and 7 is an exhaust manifold. If one injector 3 is provided for each cylinder in this way,
Injector 3 injects twice every two revolutions, whereas the corresponding cylinder has an intake stroke only once every two revolutions, so the injection amount tends to be excessive at idle when the required fuel flow rate is small, and the exhaust gas of each cylinder It is not possible to reduce the quantity below a certain value. Moreover, at high loads and high rotations, air that significantly exceeds the displacement per cylinder is forced (supercharged), so the fuel flow rate corresponding to the air flow rate is reduced to 1.
This cannot be covered by just one injector. Therefore, in an engine with a small displacement per cylinder, it is currently impossible to perform optimal air-fuel ratio control when the required fuel flow rate is small, such as when idling, and to obtain large output through supercharging at high load and high rotation speeds. This is not possible with the system shown in FIG. 1, in which one injector is provided for each cylinder.

In a multi-cylinder engine, the present invention sets cylinders whose pistons reach top dead center at the same time as one group, and installs one injector on the upstream side of the intake pipe gathering part,
Fuel is supplied during idle and low load. According to this method, even if the injection is performed at every top dead center, the injected fuel will not remain in the manifold and will be sucked into the specified cylinder every revolution, so the displacement per cylinder will be reduced. It becomes possible to lower the For example, when using the method of the present invention in a 4-cylinder engine, the number of required injectors is 2.
Become an individual. Assuming that the minimum displacement that can be covered by one injector is 150 c.c., the minimum displacement of a 4-cylinder engine with the conventional method of providing one injector per cylinder is 600 c.c. In the case of the present invention, the minimum displacement can be reduced to half that amount, 300c.c. Similarly, in the case of 6 cylinders, it will be 450c.c.

However, at high loads and high rotations, it is necessary to supply a large amount of fuel commensurate with the increase in air flow rate, but the amount of fuel supplied by the injector (main injector) alone is insufficient. Therefore, it is necessary to newly install an auxiliary injector for high-load, high-speed use to compensate for the lack of fuel supply.

FIG. 2 shows an embodiment, and in FIG. 2, the same reference numerals as those in FIG. 1 indicate corresponding parts. The exhaust manifold 7 is connected to the exhaust gas inlet 12 of the turbine 11 of the supercharger 10 . 13 is an exhaust gas outlet. A pressurized air outlet 15 of a compressor 14 driven by a turbine 11 is connected to an equalizer tube 5 via an intake pipe 6. 16 is an air inlet.

Manifold 18 (first group) communicating with the second and third cylinders whose pistons reach top dead center at the same time
The main injector 19 is attached to the intake pipe gathering portion 18a of the
and an auxiliary injector 20 are arranged. Also, the pistons of the first and fourth cylinders reach top dead center at the same time.
A main injector 19 and an auxiliary injector 20 of the same size (same specifications) are also arranged in the intake pipe gathering portion 21a of the manifold 21 (second group) communicating with the cylinders. The explosion interval of each cylinder of engine 1 has a phase difference of 180°. Main injector 19
The injector is in charge of low load and low rotational speed ranges, and the timing is determined so that it injects once at top dead center for every revolution of the engine 1, and the injected fuel flow rate per injection is small. On the other hand, the auxiliary injector 20 is in charge of high load and high rotation speed ranges, and detects high load and high rotation speed based on the amount of intake air, and when the amount of intake air increases above a certain value, the top dead center It is electronically controlled to inject. Both injectors 19, 20 may be of the same size.

During operation in a low load and low rotational speed range, fuel is injected only from the main injector 19. Focusing on the intake pipe gathering portion 18a, the fuel injected from the main injector 19 at top dead center is immediately sucked into the cylinder (second cylinder or third cylinder) that is in the intake stroke at that time, and the next injected fuel is It is immediately drawn into the other cylinder. In other words, the fuel injected at the collecting part 18a does not stay in the intake manifold 18, and is injected once per rotation into the second injected fuel.
It is alternately inhaled into the cylinder or the third cylinder. Therefore, compared to the conventional case shown in FIG. 1, the amount of fuel taken into each cylinder is reduced to 1/2 when the main injector 19 and the injector 3 shown in FIG. 1 have the same specifications.
Therefore, in the case of FIG. 2, the minimum displacement of each cylinder can be reduced to half of the conventional one. During high-load, high-speed rotation, the amount of intake air increases rapidly, so the auxiliary injector 20 starts operating, and each cylinder has one of the main injector 19 and the auxiliary injector 20.
The total amount of fuel for each injection is taken in, making it possible to obtain large output through supercharging.

As explained above, according to the present invention, fuel can be supplied from an idle low load range to a high load high speed range in a small displacement supercharged engine. Therefore, the same output as before can be obtained with a smaller displacement, resulting in improvements in mechanical loss, fuel consumption rate, and driving performance. In addition, it becomes possible to reduce the diameter of the bore by increasing the number of cylinders, thereby improving the knock limit, improving the compression ratio, improving theoretical thermal efficiency, and improving fuel efficiency. To explain the effects of the present invention more specifically, in the present invention, a pulse control solenoid valve type injector is used as an injector in a small displacement multi-cylinder supercharged spark ignition engine in which each cylinder has a small displacement with a very small required fuel flow rate. This applies to cases where
In such cases, there is a lower limit to the effective pulse width required to open the injector, and there is a special situation in which air-fuel ratio control becomes impossible if the pulse width is lowered below the lower limit in order to obtain a minute injection amount. There is. As a countermeasure against this, the fuel supply system of the present invention has two cylinders' intake pipes that reach top dead center at the same time and have a phase difference of 180 degrees as one group, and a pulse control solenoid valve type is installed upstream of the intake pipe gathering part of each group. One main injector 19 for low-load, low-speed range and one or more auxiliary injector 20 for high-load, high-speed range are provided, and the upstream side of each gathering part is sequentially connected to a common equalizer tube 5 and one equalizer tube 5. It is characterized in that it is connected to a pressurized air outlet 15 of a supercharger compressor 14 via an intake pipe 6, and a throttle valve 4 is provided in the intake pipe near the inlet of each cylinder. For example, in the intake pipe gathering portion 18a, the fuel injected from the main injector 19 at top dead center is immediately drawn into one cylinder that is in the intake stroke at that time, and the next injected fuel is injected into the other cylinder. Inhaled immediately. That is, the fuel injected at the collecting portion 18a is transferred to the intake manifold 18.
The fuel does not remain in the cylinder, but is alternately drawn into one or the other cylinder each time it is injected once per revolution.
Moreover, since the throttle valve 4 is provided near the inlet of each cylinder on the downstream side of the main injector 19, the fuel particles injected from the main injector 19 and the auxiliary injector 20 are throttled by the throttle valve 4 into the intake pipe. Atomization is promoted when the engine passes through the engine, and atomization is promoted especially in the low load and low rotational speed range where the opening of the throttle valve 4 is small, and even when the engine is idling with a small displacement engine where the required fuel flow rate is minute. ,
Combustion becomes stable. A supply equalizer tube 5 is arranged upstream of the intake pipe collection parts 18a, 21a, and each intake pipe collection part 18a, 21a has two
Since the cylinders are shared, the intake pipe gathering parts 18a and 21
The suspension period of the intake air flow in the equalizer tube 5 has been shortened (half compared to the conventional one), and as a result, the air flow in the equalizer tube 5 has become smoother with fewer flow stops. Enables uniform fuel supply to small displacement multi-cylinder engines. Even when the amount of intake air increases during high-load, high-speed rotation due to supercharging, the frequency at which the flow of intake air stops within the intake pipe gathering portions 18a and 21a decreases, making it easier to obtain the desired high output.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing a conventional system, and FIG. 2 is a schematic plan view of an apparatus according to the present invention. 1...4-cylinder engine, 18...1st group manifold, 19...
Main injector, 20... Auxiliary injector, 21... Second group manifold.

Claims (1)

[Claims] 1. In a small-displacement multi-cylinder supercharged spark-ignition engine in which each cylinder has a small displacement with a very small required fuel flow rate, the intake pipes of two cylinders that reach top dead center at the same time and have a phase difference of 180 degrees are grouped as one group. , one pulse-controlled solenoid valve-type main injector 19 for low-load, low-speed range and one or more auxiliary injectors for high-load, high-speed range 20 are provided upstream of the intake pipe collection part of each group. A common equalizer tube 5 is installed on the upstream side of the section.
and the turbocharger compressor 1 via one intake pipe 6.
4. A fuel supply system for a small supercharged spark ignition engine, characterized in that a throttle valve 4 is connected to the pressurized air outlet 15 of No. 4 and provided in the intake pipe near the inlet of each cylinder.