JPH0425434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for a fuel injection engine, and particularly to a fuel pressure adjustment system thereof.

BACKGROUND ART In fuel injection engines, in order to supply an appropriate amount of fuel, control has been conventionally performed to maintain a constant pressure difference between the fuel pressure at a fuel injection nozzle and the intake pressure near the nozzle. However, the required fuel supply condition changes depending on the operating condition, for example, when it is cold, when accelerating/decelerating, when high load is low, when the load is low or high speed, etc. Therefore, the differential pressure is changed depending on the operating condition, and the fine particles of fuel It is desirable to control the

JP-A-55-12269 is equipped with a fuel pressure regulator that maintains the differential pressure between the supplied fuel pressure and the intake pressure near the fuel outlet at a predetermined value, and also adjusts the supplied fuel pressure by the fuel pressure regulator according to the operating state of the engine. A fuel supply device including a fuel pressure correcting means has been proposed. However, this publication does not specifically disclose how the fuel pressure is corrected depending on the driving condition. Moreover, it does not take into account that changes in fuel pressure not only change the amount of fuel supplied, but also affect the combustion state.

An object of the present invention is to provide a fuel supply system for an engine that can promote atomization of fuel by increasing the fuel pressure, particularly during light loads, thereby improving combustibility.

In order to achieve this object, the present invention includes a throttle valve that controls the amount of intake air by changing the passage area of an intake passage, a fuel injector that injects and supplies fuel, and a fuel pressure regulator that controls the fuel pressure applied to the fuel injector. The fuel pressure regulator includes an intake pressure chamber to which the intake passage pressure on the downstream side of the throttle valve is introduced via an intake pressure introduction passage, and a difference between the pressure and the fuel pressure in response to the pressure in the intake pressure chamber. In a fuel injection engine having a fuel pressure regulating valve mechanism that maintains the fuel pressure at a substantially constant level, the throttle valve is located upstream of the throttle valve when the throttle valve is in its closed position, and is located downstream of the throttle valve when the throttle valve opens to a predetermined opening degree. The fuel pressure regulator is characterized in that a correction pressure introduction passage communicating with the intake passage is connected to the fuel pressure regulator through an opening located at the intake passage. It is known that increasing the fuel pressure promotes atomization of the fuel and improves combustion conditions. However, depending on the operating conditions, the combustion state may become too good and the generation of Nox may become a problem.

According to the present invention, at light load when the throttle valve opening is below a predetermined value, the correction pressure introduction passage opens into the intake passage on the upstream side of the throttle valve. introduced into the pressure chamber. As a result, the differential pressure between the fuel pressure and the intake passage pressure near the fuel injector is maintained high, promoting atomization of the fuel, thereby improving the combustion state. When the throttle valve opens to a predetermined value or higher during medium-high load, the pressure in the correction pressure introduction path becomes the same as the intake pressure, and the differential pressure is maintained at a relatively low, almost constant value. This alleviates the atomization of the fuel, prevents the combustion state from becoming excessively good, and suppresses the generation of Nox.

Further, in carrying out the present invention, it is preferable to include an adjustment mechanism that changes the passage area of the intake pressure introduction passage, and by operating the adjustment mechanism, the fuel pressure can be changed during light load, especially when idling. This makes it possible to provide appropriate fuel supply and reduce the influence of metering errors of the air flow heater. By installing this adjustment mechanism independently of the control circuit for controlling the fuel supply amount, it is possible to avoid complication of the control circuit, and it is also possible to adjust the fuel supply amount during idling independently of the control by the control circuit. It has the advantage of making it possible.

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

FIG. 1 shows a schematic diagram of an engine E according to the invention.

The engine E includes a cylinder 10 and a cylinder 10.
The cylinder 10 includes a piston 12 that slides therein, and a combustion chamber 14 is formed in the upper part of the cylinder 10.
The combustion chamber 14 has an intake port 16 and an exhaust port 1.
8 is open, and these ports 16 and 18 are provided with an intake valve 20 and an exhaust valve 22 for opening and closing the ports. Further, an intake passage 24 is connected to the intake port 16, and an exhaust passage 26 is connected to the exhaust port 18. An air cleaner 28 is provided at the upstream end of the intake passage 24, an air flow meter 30 for measuring the amount of intake air is installed downstream of the air cleaner 28, and a supercharger 32 for supercharging the intake air is located downstream of the air cleaner 28.
is provided. Furthermore, a throttle valve 34 that is moved in conjunction with the accelerator pedal is disposed downstream of the supercharger 32, and a fuel injector 36 that injects and supplies fuel at a predetermined fuel pressure is disposed downstream of the throttle valve 34. The fuel in the fuel tank 38 is pressurized by the fuel pump 40 and is discharged into the passage 42 and guided to the fuel injector 36.

The pressure of the fuel discharged into the passage 42 is regulated by a fuel pressure regulator 46.

As shown in FIG. 2, the fuel pressure regulator 4
6 is equipped with a diaphragm device 48, and a casing 50 of the diaphragm device 48 is partitioned by a diaphragm 52, and an intake pressure chamber 56 that communicates with the intake passage 24 via a passage 54 and a branch passage 44 from the fuel passage 42. A fuel chamber 58 communicating with the fuel chamber 58 is formed inside. The fuel tank 3 is located in the fuel chamber 58.
A return passage 45 to 8 protrudes, and its tip 6
6 opens into the chamber 58 so as to oppose the diaphragm 52. A portion of the fuel discharged from the fuel pump 40 is guided from the branch passage 44 into the fuel chamber 58 and returned to the fuel tank 38 through the gap between the diaphragm 52 and the tip 66. A spring 60 is arranged in the intake pressure chamber 56 and urges the diaphragm to the left in the figure. Further, the passage 54 from the intake pressure chamber 56 branches into a correction pressure introduction passage, that is, an upstream communication passage 55, and an intake pressure introduction passage, that is, a downstream communication passage 57, which communicate with the intake passage 24. As shown in FIG.
7 is connected downstream of the throttle valve 34,
The upstream communication passage 55 opens upstream of the throttle valve 34 during idling, that is, when the throttle valve 34 is in the fully closed position as shown by the solid line in the figure, and when the engine load increases, the throttle valve 34 closes as shown by the broken line.
4 is connected to a position where it opens downstream of the valve 34 when the valve 4 opens to a predetermined opening degree. The upstream communication passage 55 is provided with an adjustment valve 59 that changes the passage area of the passage 55.

Referring again to FIG. 1, a control unit 68 is provided to control the injection and injection amount of the solenoid valve type fuel injector 36, that is, the valve opening time. The control unit 68 calculates signals from the engine speed sensor 70 and the air flow meter 30 and sends control signals to the fuel injector 36.

In a device with this structure, when the engine is under a light load, the upstream communication passage 55 opens upstream of the throttle valve 34, so that relatively high intake pressure on the upstream side of the throttle valve 34 is introduced into the communication passage 55. Ru. On the other hand, downstream of the throttle valve 34, the valve 34
Strong negative pressure is generated because the opening degree is small.
Therefore, a pressure difference is generated between the communication passages 55 and 57, and an air flow from the communication passage 55 toward the communication passage 57 is generated. An intermediate pressure between the communication passage 55 and the communication passage 57 is introduced into the intake pressure chamber 56 of the diaphragm device 48 through the passage 54 . Therefore, the diaphragm 52 moves to the left in FIG. 2, the gap between the diaphragm 54 and the tip 66 of the return passage 45 narrows, and the amount of fuel returned to the fuel tank 38 decreases. This increases the fuel pressure applied to the fuel injector 36. At this time, the intake pressure near the fuel injector 36 is low, so the differential pressure between the fuel pressure and the intake pressure becomes large. Therefore,
Atomization of fuel is promoted and combustion conditions are improved.
After that, when the load increases and the throttle valve opening exceeds a predetermined value, and the opening of the upstream communication passage 55 is located downstream of the throttle valve 34, the communication passage 55
The pressure difference between 5 and 57 disappears, and the air flow in the communication path disappears. Therefore, the low pressure downstream of the throttle valve is introduced into the intake pressure chamber 56. Therefore, the diaphragm 52 moves to the right in FIG. 2, the gap between the diaphragm 52 and the return passage 45 increases, and the amount of fuel returned increases.
As a result, the difference between the fuel pressure and the intake passage pressure decreases as the fuel pressure decreases, and atomization of the fuel is alleviated. Thereafter, when the opening degree of the throttle valve 34 further increases, the intake passage pressure increases and the fuel pressure also increases, but the differential pressure therebetween remains constant. That is, in medium to high load operation, by maintaining a relatively small constant differential pressure, combustibility is prevented from becoming excessively high and the generation of Nox is suppressed. Furthermore, by operating the regulating valve 59 to change the passage area of the communication passage 55, the pressure introduced into the intake pressure chamber 56 changes, thereby making it possible to appropriately adjust the fuel pressure. By performing such adjustment, it is possible to reduce the influence of measurement errors of the air flow meter 30 that occur when the amount of intake air is small, such as during idling, and to perform proper operation. Note that in order to control the pressure introduced into the intake pressure chamber 56, it is preferable to provide an appropriate throttling mechanism such as an orifice in the communicating passages 55, 57 so that they have appropriate resistance.

[Brief explanation of drawings]

1 is a schematic diagram of an engine according to an embodiment of the present invention, FIG. 2 is a detailed diagram of the fuel pressure regulator of FIG. 1, and FIG. 3 is a detailed diagram of section A in FIG. 1. Explanation of symbols, 10...Cylinder, 12...Piston, 14...Combustion chamber, 16...Intake port, 1
8...Exhaust port, 20...Intake valve, 22...Exhaust valve, 24...Intake passage, 26...Exhaust passage, 2
8...Air cleaner, 30...Air flow meter, 32...Supercharger, 34...Throttle valve, 36
...Injector, 38...Fuel tank, 40...
...Fuel pump, 46...Fuel pressure regulator, 55
...Upstream communication path, 57...Downstream communication path, 59
……Regulating valve.

Claims (1)

[Claims] 1. A throttle valve that controls the amount of intake air by changing the passage area of an intake passage, a fuel injector that injects and supplies fuel, and a fuel pressure regulator that controls the fuel pressure applied to the fuel injector,
The fuel pressure regulator includes an intake pressure chamber to which the intake passage pressure on the downstream side of the throttle valve is introduced via an intake pressure introduction passage, and responds to the pressure in the intake pressure chamber to keep the difference between the pressure and the fuel pressure substantially constant. In a fuel injection engine having a fuel pressure regulating valve mechanism for maintaining a fuel pressure, an opening located upstream of the throttle valve when the throttle valve is in a closed position and located downstream of the throttle valve when the throttle valve is opened to a predetermined opening degree. 1. A fuel supply system for an engine, characterized in that a correction pressure introduction passage communicating with an intake passage is connected to the fuel pressure regulator.