JPS6340266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for a fuel injection type 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, it has been conventionally practiced 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 amount and fuel atomization change depending on the operating conditions, such as cold, acceleration/deceleration, high/low load, low/high speed, etc. It is desirable to vary the pressure.

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 state. 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 device for an engine that can reduce exhaust temperature by increasing the differential pressure between fuel pressure and intake pressure near a fuel injection position when exhaust gas temperature rises. .

The configuration of the present invention includes a fuel injector that injects and supplies fuel, a fuel pressure regulator that controls the fuel pressure of the fuel supplied to the fuel injector, and a pressure difference between the intake pressure and the fuel pressure at the fuel injection position of the intake passage. a means for operating the fuel pressure regulator so that the pressure difference is equal to or higher than a set value; It is characterized by comprising a control means for activating the differential pressure increasing means when the pressure difference increases.

According to the present invention, when the temperature of the exhaust passage becomes equal to or higher than a set value, the differential pressure increasing means is operated by the control means, and the differential pressure between the fuel pressure and the intake pressure is increased. This promotes fuel atomization and
The mixture becomes more homogenized, the combustion rate increases, and the exhaust gas temperature decreases. In carrying out the present invention, it is preferable to control the fuel injection time so as to maintain the fuel supply amount constant by changing the fuel injection time in accordance with the above-described fuel pressure control, but it is not necessary to perform such control. Exhaust gas temperature can be lowered by changing the air-fuel ratio to make the air-fuel mixture richer, but simply changing the air-fuel ratio will inevitably result in a decrease in output. However, if measures are taken without increasing the fuel pressure, as in the present invention, it is not necessarily necessary to enrich the air-fuel mixture, and it is possible to reduce the exhaust temperature without reducing the output. Furthermore, if the fuel injection time is not corrected in accordance with fuel pressure control, the amount of fuel supplied will increase by the amount of increase in fuel pressure, and a further decrease in exhaust gas temperature can be expected. Furthermore, in normal conditions, the fuel pressure is maintained at a relatively low value, so the power consumption of the fuel pump is small, and there is little effect on fuel efficiency or battery power.

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

FIG. 1 shows a schematic diagram of an engine E incorporating the fuel pressure control device of the present invention. The engine E includes a cylinder 10 and a piston 12 that slides within the cylinder 10, and a combustion chamber 14 is formed in the upper part of the cylinder 10. cylinder 1
4 has an intake port 16 and an exhaust port 18 open therein, and these ports 16 and 18 are provided with an intake valve 20 and an intake 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, and an air flow meter 30 for measuring the amount of intake air is provided downstream of the air cleaner 28.
Subsequently, a supercharger 32 for supercharging intake air is provided downstream. Further, downstream of the supercharger 32, a throttle valve 3 is operated in conjunction with the access pedal.
4, and a fuel injector 36 that injects and supplies fuel at a predetermined fuel pressure is disposed downstream thereof. A catalytic converter 27 is disposed in the exhaust passage 26, and an exhaust temperature sensor 29 for detecting exhaust gas temperature is attached downstream of the catalytic converter 27. The fuel in the fuel tank 38 is pressurized by the fuel pump 40 and flows into the passage 42.
The fuel is discharged into the fuel injector 36 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 has a negative pressure chamber 56 that is partitioned by a diaphragm 52 and connected to the downstream side of the throttle valve 34 in the intake passage 24 via a passage 54, and a fuel A fuel chamber 58 communicating with the branch passage 44 from the passage 42 is formed inside. A spring 60 is arranged in the negative pressure chamber 56 and the diaphragm 52
is biased to the left in the figure. One end of the spring 60 is supported by a disk 62, and a pin 63 extending outward from the inside of the casing 50 is connected to the disk 62, and this pin 63 constitutes a movable element of the solenoid. A solenoid coil 64 is provided around the pin 63.
4 is energized, the pin 63 and disk 62 are moved to the left in the figure. A return passage 45 to the fuel tank 38 protrudes from the fuel chamber 58, and its tip 66 opens into the chamber 58 so as to face 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. diaphragm 52
moves to the right in the figure when the pressure in the intake passage decreases. This increases the gap between the tip 66 and the diaphragm 52, which increases the gap between the tank 40 and the diaphragm 52.
The amount of return to will increase. Therefore, the fuel pressure applied to the injector 36 decreases. In this case, the diaphragm 52 moves in response to changes in the pressure in the intake passage, the differential pressure between the fuel pressure and the pressure in the intake passage is kept constant, and the amount of fuel injection is determined by the time the injector is open. . Furthermore, when the solenoid coil 64 is excited, the pin 63 moves to the left in the figure and strengthens the biasing force of the spring 60, so that the amount of fuel returned decreases and the fuel pressure increases.

A control 65 that receives a signal from the exhaust temperature sensor 29 is provided to control the solenoid coil 64 . The control 65 includes a comparison circuit and a drive circuit, and the exhaust temperature sensor 2
The signal from 9 is first input to the comparison circuit. The comparison circuit compares the temperature signal from the exhaust temperature sensor 29 with a predetermined value, and outputs a high level signal when the exhaust gas temperature is higher than the predetermined temperature, and a low level signal when it is below the predetermined temperature, and this signal is sent to the drive circuit. is input. The drive circuit outputs a signal that excites the solenoid coil 64 when the signal from the comparison circuit is at a high level. Referring again to FIG. 1, the apparatus of this example is provided with a control unit 68 in addition to the controller 65 described above. The control unit 68 calculates signals from the engine speed sensor 70 and the air flow meter 30 and outputs a signal to the electromagnetic valve type injector 36 to control the valve opening time, that is, the injection amount.

In the device having the above structure, under normal operating conditions, that is, when the exhaust gas temperature is below a predetermined value, the output of the comparison circuit of the controller 65 is at a low level, so the solenoid coil 64 is not excited, and the spring 60 The biasing force of is small. Therefore, the amount of fuel returned is large and the fuel pressure is at a low value. When the exhaust gas temperature exceeds a predetermined value, the output of the comparison circuit changes to a high level, and the solenoid coil 64 is energized. As a result, the pin 63 and the disc 62 move to the left in FIG. 2, and the biasing force of the spring 60 is strengthened. Therefore, the diaphragm 52 moves to the left, the amount of fuel returned decreases, and the fuel pressure increases. When the fuel pressure increases, the atomization of the fuel is promoted, the air-fuel mixture becomes more homogeneous, and the combustion rate increases.
Therefore, the exhaust temperature decreases. In this case,
Since the controller 65 operates independently of the control unit 68, the injection time is not corrected even if the fuel pressure increases. Therefore, the air-fuel mixture is enriched, and the exhaust gas temperature is further reduced. Also, the output of the controller 65 is connected to the control unit 6.
8, when the control to increase the fuel pressure is performed, the fuel injection time can also be controlled so that the fuel supply amount does not change.

As described above, in the present invention, when the exhaust gas temperature rises above a predetermined value, the fuel pressure is increased and the combustion speed is accelerated, so the exhaust temperature is effectively lowered and a fire caused by overheating of the exhaust pipe is prevented. It can prevent danger and deterioration of the exhaust system catalyst.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a fuel supply system for an engine according to an embodiment of the present invention, and FIG. 2 is a detailed view of the fuel pressure regulator shown 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, 29...Exhaust temperature sensor,
30...Air flow meter, 32...Supercharger, 3
4...Throttle valve, 36...Injector, 3
8...Fuel tank, 40...Fuel pump, 46...
...Fuel pressure regulator, 64... Solenoid coil, 65... Controller, 68... Control unit.

Claims (1)

[Claims] 1. A fuel injector that injects and supplies fuel, a fuel pressure regulator that controls the fuel pressure of the fuel supplied to the fuel injector, and a fuel pressure regulator that controls the fuel pressure so that the differential pressure between the intake pressure and the fuel pressure at the fuel injection position in the intake passage becomes a predetermined value. A fuel injection engine comprising means for operating the fuel pressure regulator,
It is characterized by comprising means for increasing the differential pressure, means for detecting the temperature of the exhaust passage, and control means for operating the differential pressure increasing means when the temperature of the exhaust passage exceeds a set value. Engine fuel supply system.