JPH0475377B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel supply device for a fuel injection type engine, and in particular, to a fuel supply device for a fuel injection type engine, which is suitable for use in a spark ignition type engine equipped with an electronically controlled fuel injection device. The present invention relates to an improvement of a fuel supply device for a fuel injection type engine for supplying fuel.

[Prior art]

2. Description of the Related Art An electronically controlled fuel injection device is used as one of devices for controlling the air-fuel ratio of an air-fuel mixture in an internal combustion engine such as an automobile engine. In an engine equipped with this electronically controlled fuel injection device, for example, the fuel injection time is determined according to the intake air amount or intake pipe pressure of the engine, the engine rotation speed, etc. The air-fuel ratio of the engine is controlled by intermittently opening an injector that injects fuel toward the engine's intake port or intake manifold. It is becoming widely used in automobile engines equipped with exhaust gas purification measures, which require control over the exhaust gas. However, in such fuel injection type engines, fuel atomization is improved compared to carburetor type engines, where fuel atomization is promoted when pre-air-bleed fuel is discharged from the bench lily into the intake passage. The problem is that it is not very good. In order to solve these problems, traditionally,
Atomization of fuel has been promoted by devising the nozzle shape of the injector, or by using an air assist injector that sends a portion of the intake air into the vicinity of the injector nozzle. If the nozzle shape is complicated, not only will there be a problem that the fuel control accuracy will deteriorate, but also because it is an intermittent injection, even if an air-assist injector is used, the fuel will become liquid at the beginning of the injection. As a result, there was a limit to atomization. Therefore, the injected fuel adheres to the intake port or the intake manifold, resulting in problems such as poor transient characteristics and a low lean combustion limit. On the other hand, as something similar to the present invention, so-called intake air heating, which heats intake air, has been put into practical use, but in this case, the injected fuel is heated by the intake air and atomized, so it can be quickly I couldn't expect a lot of atomization. In order to solve these problems, it is possible to heat and pressurize the fuel injected from the injector to a set temperature and pressure at which the fuel does not boil in the fuel passage, but boils under reduced pressure when it is injected. Although it is possible, regardless of the engine operating condition,
If the fuel is constantly heated, the density of the fuel will decrease due to fuel heating, which will reduce the filling efficiency in the cylinder and reduce the engine output performance, especially when high output is required such as at full load. There was a risk that it would decline.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and is capable of quickly and effectively promoting atomization of injected fuel, while also ensuring engine output performance under full load. The purpose of the present invention is to provide a fuel supply device for a fuel injection type engine that can perform the following steps.

[Structure of the invention]

The present invention relates to a fuel supply system for a fuel injection engine for supplying pressurized fuel to an injector disposed in an intake manifold or a throttle body. On the other hand, there is a fuel heating means for heating the fuel to a set temperature at which reduced pressure boiling occurs when it is injected, and the pressure of the fuel injected from the injector is controlled so that the fuel does not boil in the fuel passage and, on the other hand, when it is injected. A fuel pressurizing means for pressurizing the fuel to a set pressure at which depressurized boiling occurs at times, and a heating control means for lowering the heating temperature by the fuel heating means at full load are provided to promote atomization of the injected fuel, The above object is achieved by preventing a decrease in output performance at full load. Further, in an embodiment of the present invention, the full load state is detected by fully opening the throttle, so that the full load state can be easily and reliably detected.

[Action of the invention]

In the present invention, the temperature and pressure of the fuel injected from the injector are heated and pressurized to a set temperature and pressure at which the fuel does not boil in the fuel passage, but boils under reduced pressure when it is injected, and At full load, the heating temperature is lowered, so the fuel injected into the intake manifold or throttle body boils under reduced pressure, which promotes atomization of the injected fuel and reduces engine output performance at full load. Prevented.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, a first embodiment of the present invention is a fuel injection type engine 10 for supplying pressurized fuel to an injector 16 disposed downstream of a throttle valve 14 of a throttle body 12. In the device, a fuel pump 22 with a larger capacity than the conventional one is used to pressurize the fuel sucked from the fuel tank 18 through the fuel supply passage 20.
Then, the fuel pressurized by the fuel pump 22 is set at a set pressure such that the fuel does not boil in the fuel supply passage 28 and, on the other hand, boils under reduced pressure when injected from the injector 16, such as a normal fuel pressure.
From the injector 16, which is disposed in a fuel pressure regulator 26 for adjusting the pressure to about 3Kg/cm ² G, which is higher than 2.55Kg/cm ² G, and a fuel supply passage 28 connecting the fuel pressure regulator 26 and the injector 16. Only the fuel to be injected is sent to the fuel supply passage 2.
8, the fuel will not boil, but on the other hand, when it is injected, boiling under reduced pressure will surely occur.For example, the set temperature is 80.
A fuel heating device 30 for heating the fuel to ℃, a throttle sensor 32 for detecting the opening degree of the throttle valve 14, and an engine load and engine rotation speed detected by intake pipe pressure or intake air amount. Accordingly, a valve opening time signal is output to the injector 16, and heating by the fuel heating device 30 is stopped when the throttle opening detected by the throttle sensor 32 is at full load and exceeds a predetermined opening. electronic control unit (hereinafter referred to as
(referred to as ECU) 34. In the figure, 40 indicates the fuel pressure regulator 2
6 is a fuel return passage for returning surplus fuel to the fuel tank 18; 42 is an air nose for sucking air from outside; 44 is an air nose 42;
An air cleaner 46 for cleaning air taken in by the intake duct 48 connects the air cleaner 44 and the throttle body 12.
is an intake manifold that connects the throttle body 12 and each cylinder of the engine 10. As the fuel heating device 30, for example, one that uses engine cooling water temperature or engine oil as a heating source can be used, and when heating is to be stopped, an on-off valve 30A provided on the inlet side thereof is closed. be able to. In this case, a separate heating source is not required. The relationship between the set temperature in the fuel heating device 30 and the set pressure in the fuel pressure regulator 26 is set so that the fuel does not boil in the fuel passage, but boils under reduced pressure when it is injected. Generally, the higher the set temperature, the higher the set pressure needs to be, and in conventional electronically controlled fuel injection engines that do not heat fuel, the set pressure of the fuel pressure regulator 26 is set to 2.55 Kg/cm ² G. However, at this set pressure, when heating the fuel, an unstable region where liquid L and gas G coexist will occur depending on the fuel temperature, as shown in Figure 2, so in order to ensure boiling under reduced pressure, It is better to increase the pressure higher than the conventional pressure. Therefore, in this embodiment, the capacity of the fuel pump 22 is increased compared to the conventional one. The action will be explained below. The injector 16 in the ECU 34
Since the control of the energization time is well known, the explanation will be omitted. On the other hand, heating control of the fuel heating device 30 according to the present invention in the ECU 34 is executed according to a flowchart as shown in FIG. That is, for example, every time a predetermined period of time elapses, step 110 is entered and the throttle opening Thr of the throttle sensor 32 output is acquired. Next, the process proceeds to step 112, where it is determined whether the throttle opening Thr that has been taken is equal to or greater than a predetermined opening corresponding to the full load, for example, 50 degrees. If the judgment result is positive, proceed to step 114;
The on-off valve 30A of the fuel heating device 30 is closed, and this routine ends. On the other hand, if the determination result in step 112 is negative, this routine is immediately terminated. In this first embodiment, it is possible to use the same injector 16 used in conventional fuel injection engines. Further, in this first embodiment, since the fuel heating device 30 is disposed downstream of the fuel pressure regulator 26, it is possible to efficiently heat only the fuel injected from the injector 16. The fuel in the tank 18 does not rise. Note that the location of the fuel heating device 30 is not limited to this, and for example, it may be provided between the fuel pump 22 and the fuel pressure regulator 26, and the fuel heating device 30 may be provided between the fuel return passage 40
It is also possible to prevent the temperature of the fuel in the fuel tank 18 from rising by providing a separate fuel cooling device. Next, a second embodiment of the present invention will be described in detail. This second embodiment, as shown in detail in FIG.
A fuel pump 22 with the same capacity and set pressure as before, a fuel pressure regulator 26, and fuel supply passages 20, 24, 28 and an ECU 34 similar to those in the first embodiment.
In the fuel supply system for the fuel injection engine 10 having the fuel return passage 40, the injector 5
By providing a fuel heating means and a final fuel pressurizing means inside the injector 50, fuel heating and final pressurizing are performed inside the injector 50. As shown in detail in FIGS. 4 and 5, the injector 50 pressurizes the fuel introduced into the injector body 50A to a pressure suitable for injection.
A piezoelectric element 52 for ejecting from a nozzle 50B formed at the tip thereof, a piston receiver 54 disposed at the tip of the piezoelectric element 52, and the piston receiver 5
a piston 56 disposed below the piston 56; a plate 58 disposed below the piston 56; a mesh-shaped ceramic heater 60 disposed at the center of the plate 58; 60 to a set temperature, e.g., 80°C, to a final pressure suitable for injection, e.g., higher than the normal fuel pressure of 2.55 Kg/cm ² G.
It is comprised of a nozzle opening/closing valve 62 for pressurizing and injecting up to Kg/cm ² G. In the figure, 6
4 is a check ball for preventing backflow of fuel, and 66 is a check ball holding rod for holding the check ball 64 in a predetermined position. The nozzle opening/closing valve 62 includes a diaphragm 62A.
, a valve spring 62B, and a rod 62C. The action will be explained below. The fuel sucked through the fuel pump 22 is controlled by the fuel pressure regulator 26 to a normal set pressure.
For example, it is adjusted to 2.55Kg/cm ² G, and the excess fuel is
The fuel is returned via the fuel return passage 40.
Fuel adjusted to a normal set pressure by the fuel pressure regulator 26 is supplied to the injector 50. In the injector 50, a necessary pulse frequency and driving voltage are applied to the piezoelectric element 52 by the output of the ECU 34, and the displacement of the piezoelectric element 52 causes the piston 56 to operate. At this time, the fuel pressure in the pressure chamber 57 on the downstream side of the piston 56 becomes considerably higher than the control pressure of the fuel pressure regulator 26 when the piston operates, and the pressure difference is as follows.
It can be adjusted by the valve spring 62B. Therefore, when the piston 56 operates and the fuel pressure reaches the set pressure of the valve spring 62B, for example, 3 kg/cm ² G or more, the nozzle opening/closing valve 62 operates, the nozzle 50B is opened, and fuel is discharged. At this time, the injected fuel is heated to a set temperature, for example 80° C., by the ceramic heater 60 attached to the plate 58, so boiling under reduced pressure occurs and atomization is promoted. Further, as in the first embodiment, when the throttle opening detected by the throttle sensor or the like is at full load and is equal to or higher than the set value, the power supply to the ceramic heater 60 is stopped, and when the throttle opening is at full load, the ceramic heater 60 is stopped. This prevents deterioration in output performance when In this embodiment, since the pressure of the fuel introduced into the injector 50 can be the same as that of the conventional one, the same fuel pump 22 and fuel pressure regulator 26 as the conventional one can be used, and the structure can be constructed at low cost. Further, in this embodiment, since the fuel heating means is a mesh-shaped ceramic heater 60 built into the injector 50, only the fuel injected from the injector 16 can be heated extremely efficiently. Furthermore, the fuel can be heated even during a cold start, and by reducing the amount of fuel added during a cold start, the fuel efficiency of the engine can be improved. Further, in all of the above embodiments, the full load state is detected by fully opening the throttle, so the full load state can be easily and reliably detected. Note that the method for detecting the full load state is not limited to this, and it is also possible to detect from, for example, the intake air amount or intake pipe pressure, or furthermore, the injector valve opening time. In addition, in all of the above embodiments, fuel heating by the fuel heating means is completely stopped during full load, but it is not necessarily necessary to stop fuel heating during full load, but only by lowering the heating temperature. In some cases, sufficient effects can be obtained.

【Effect of the invention】

As explained above, according to the present invention, the fuel injected from the injector is boiled by the principle of reduced pressure boiling, atomization is promoted, and the fuel is in a state close to a gas.
Supplied to the intake manifold or intake port. Therefore, almost no injected fuel adheres to the intake manifold or intake port, improving transient characteristics. Furthermore, since the injected fuel is supplied in a nearly gaseous state, the fuel and air in the engine fuel chamber form a completely homogeneous mixture, improving the lean combustion limit. Furthermore, since the fuel heating temperature is lowered during full load, it has excellent effects such as preventing a decrease in engine output performance due to a decrease in charging efficiency during full load.

[Brief explanation of the drawing]

FIG. 1 is a pipe diagram including a partial cross-sectional view and a block diagram showing the structure of a first embodiment of a fuel supply system for a fuel injection engine according to the present invention, and FIG.
FIG. 3 is a diagram showing the relationship between the set temperature and set pressure and the state of the fuel in the first embodiment. FIG. 4 is a flowchart showing the routine of FIG. 4, and FIG. FIG. 5 is a plan view showing the configuration of the ceramic heater used in the second embodiment. 10...engine, 12...throttle body, 14...throttle valve, 16,50...
Injector, 22... fuel pump, 26... fuel pressure regulator, 30... fuel heating device, 32...
...Throttle sensor, 34...Electronic control unit (ECU), 60...Ceramic heater, 62...
Nozzle opening/closing valve.

Claims (1)

[Claims] 1. In a fuel supply device for a fuel injection engine for supplying pressurized fuel to an injector disposed in an intake manifold or a throttle body, the temperature of the fuel injected from the injector is controlled within the fuel passage. A fuel heating means for heating the fuel to a set temperature at which the fuel does not boil and, on the other hand, causes reduced-pressure boiling when injected;
On the other hand, a fuel pressurizing means for pressurizing the fuel to a set pressure at which reduced pressure boiling occurs when injected, and a heating control means for lowering the heating temperature by the fuel heating means at full load are provided, so that the injected fuel is atomized. 1. A fuel supply system for a fuel injection engine, characterized in that a reduction in output performance at full load is prevented. 2. The fuel supply system for a fuel injection engine according to claim 1, wherein the full load state is detected by fully opening the throttle.