JPS6350661A - Fuel control device for fuel injection type engine - Google Patents

Abstract

PURPOSE:To aim at enhancing the efficiency of heating and pressurizing means while ensuring stable evaporation at a negative pressure, by changing the pressure of pressurized fuel or the temperature of heating in accordance with the atmospheric pressure. CONSTITUTION:An engine 1 has a fuel regulator 21 for pressurizing fuel fed into a fuel injection valve 11 and a heater 22 for heating fuel up to a temperature at which fuel is not evaporated under this pressurized condition but is evaporated under negative pressure, when fuel is injected from a fuel injection valve 11. When the atmospheric pressure detected by an atmospheric pressure sensor 31 lowers, an electronic control unit 16 sets a new desired pressure which is lower than the standard atmospheric pressure by a value corresponding to the pressure reduction if stable evaporation at a negative pressure may be obtained even through the pressure of fuel and the temperature are raised up to desired fuel pressure and temperature, respectively, which have been set at during operation at the standard atmospheric pressure. With this arrangement, no useless energy is consumed, thereby it is possible to reduce the burdens of the fuel pressure regulator 21 and the heater 22.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a fuel control device for a fuel injection engine.
In particular, the present invention relates to an improvement in a fuel control device that pressurizes and heats fuel supplied to a fuel injection valve and injects the fuel in a vaporized state.

(Conventional technology) For fuel-injected engines, the amount of air intake into the engine.

The engine's air-fuel ratio is controlled by determining the fuel injection amount according to intake pipe pressure, engine speed, etc., and opening the fuel injection valve installed in the engine's intake passage intermittently in response to this. It is known to be effective in purifying exhaust gas.

This type of fuel injection engine has the disadvantage that the atomization or atomization of the fuel is inferior to that of a carburetor type engine, and various measures to promote atomization have been proposed in the past. As one of these methods, the use of so-called reduced pressure boiling phenomenon has been proposed, for example, in Japanese Utility Model Application Laid-Open No. 60-82575.

As shown in Figure 3, in the state characteristic expressed by the relationship between fuel temperature and pressure, reduced pressure boiling refers to fuel that is in a liquid state at a temperature above the fuel's saturated vapor pressure line. This is a phenomenon in which when the pressure is suddenly reduced below the superheating curve, bubbles rapidly grow due to the superheated state of the liquid fuel, and the fuel instantly splits and boils to vaporize.

To apply this phenomenon to an engine, for example, if the fuel is allowed to shift from a state above the saturated steam pressure line to a state below the superheat curve before and after the fuel injection valve, the Iζ fuel will be injected from the fuel injection valve. vaporizes immediately after that.

Therefore, in the fuel control device disclosed in the above publication,
Is there a pressurizing means for pressurizing the fuel, and when the fuel is pressurized by the pressurizing means, it does not boil in the fuel passage of the fuel injection valve, and when the fuel is injected, the pressure decreases due to sudden pressure reduction? The system is equipped with a heating means that heats the fuel to a temperature that generates 18 m, and maintains a liquid state in the fuel passage, and when injecting the fuel, instantaneously vaporizes it by boiling under reduced pressure to promote atomization of the fuel. However, this device had the following problems.

(Problems to be Solved by the Invention) That is, in the fuel control device having the above configuration, the fuel pressure applied to the fuel injection valve is controlled to a constant value (approximately 2.55 kg/cj) with respect to the pressure in the intake passage. There is.

However, the air taken into the intake passage of an engine is normally 1 atm (760 mnl Hg), but the pressure is considerably lower, for example, at high altitudes of several thousand meters.

Therefore, with control in which the fuel pressure is set to a constant value, when the atmospheric pressure itself is reduced, such as when driving at high altitudes, the pressure difference before and after the fuel injection valve becomes large, making it easy for boiling to occur under reduced pressure.

However, if the vehicle is operated without changing the fuel pressure or temperature from the normal driving conditions, there is a problem in that energy is wasted in the fuel pressurizing means and heating means.

This invention was made in view of the problems of the prior art, and its purpose is to provide fuel for a fuel injection engine that efficiently reduces and boils the fuel regardless of changes in atmospheric pressure. The purpose is to provide a control device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pressurizing means for pressurizing fuel to be supplied to a fuel injection valve, and a pressurizing means for pressurizing fuel that does not boil under pressure by the pressurizing means. A fuel injection type engine comprising a heating means for heating the fuel to a temperature at which reduced pressure boiling occurs when injected from a fuel injection valve, comprising an atmospheric pressure detecting means, and responding to the atmospheric pressure detected by the atmospheric pressure detecting means. A reduced pressure boiling condition changing means is provided for changing the fuel pressure by the pressurizing means or the fuel pressure by the heating means.

(Function) In the fuel control device having the above configuration, the pressurizing pressure and heating temperature of the fuel by the pressurizing means or the heating means depend on the atmospheric pressure. For example, when the atmospheric pressure becomes lower than 1 atm, the pressure of the fuel and Since the temperature is changed to a lower value in accordance with the magnitude of the decrease, it is possible to improve the efficiency of the heating/pressurizing means while ensuring stable boiling under reduced pressure.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 2 show an embodiment of a fuel H7ll III device for a fuel injection engine according to the present invention.

Figure 1 shows the overall configuration of the fuel control system for a fuel injection engine, where 1 is an upper engine, 2 is a combustion chamber formed with a variable volume by a piston 4 that is slidably inserted into a cylinder 3 of the engine 1. An intake passage 5 has one end communicating with the atmosphere via an air cleaner 6 and the other end opening into the combustion chamber 2 to supply intake air to the engine 1. Reference numeral 7 has one end opening into the combustion chamber 2. , is an exhaust passage for discharging exhaust gas whose other end is open to the atmosphere, and a throttle valve 8 for controlling the intake air flow rate is disposed in the middle of the intake passage 5. In the vicinity of the combustion chamber 2,
A main intake passage 5a with a large passage area and a sub-intake passage 5b with a small passage area are vertically divided by a partition wall 9, and at the upstream end of the main intake passage 5a there is formed a main intake passage 5a which closes at low load and which closes at low load.
A shirt starter valve 10 that opens during medium and high loads, and the main intake passage 5
A fuel injection valve 11 for injecting and supplying fuel is disposed downstream of the shatter valve 10 of a.

Further, an air flow sensor 12 for measuring the amount of intake air is provided downstream of the air cleaner 6, and its output signal is sent to an intake air temperature sensor 13 installed inside the air cleaner 6.
The output signal is input to the electronic control unit 16 along with output signals from an opening sensor 14 linked to the throttle valve 8 and a water temperature sensor 15 that measures the cooling water temperature of the engine 1 .

On the other hand, a fuel supply system to the fuel injection valve 11 is configured as follows.

The fuel injection valve 11 and the fuel tank 17 are connected through a fuel supply passage 18, and the fuel tank 1 is connected to the fuel supply passage 18.
Is it more voluminous than normal to pressurize the fuel downstream from 7? 1 large fuel pump, 20 fuel filters,
A fuel pressure regulator 21 for adjusting the pressure to a set pressure at which reduced pressure boiling occurs when fuel is injected from the fuel injection valve 11, for example, about 3.5 kQ/cf;
For example, a heater 22 for heating to about 120° C., a fuel pressure sensor 23 for detecting the pressure value of the pressurized fuel, and a fuel temperature sensor 24 for detecting the temperature of the heated fuel are installed in this order.

Further, a return passage 25 for returning excess fuel is connected between the fuel injection valve 11 and the fuel tank 17. , an expander that adiabatically expands and depressurizes the return fuel; a decompression/cooling device 26 that cools the expander and lowers the fuel temperature; and a regulator that controls the return fuel when the pressure of the return fuel is higher than the set pressure of the fuel pressure regulator 21 to reduce the burden on the heater 22 or fuel pump 19, and also to reduce the burden on the regulator 21.
A fuel pressure limiter 27 is provided in order to return the return fuel to the return passage 25 when the pressure is lower than the set pressure of No. 1 or when the temperature is abnormally high.

Further, between the fuel supply passage 18 on the upstream side of the heater 22 and the return passage 25 on the upstream side of the fuel limiter 27, heat is generated between the fuel before being heated by the heater 22 and the return fuel. A heat exchanger 28 is provided for carrying out the exchange.

The set pressure of the fuel pressure regulator 21, the heating temperature by the heater 22, and the control of the fuel pump 19 are controlled by the fuel pressure sensor 23. This is performed by the electronic control unit 16 using the output signal of the fuel temperature sensor 24 as an input value.

In addition to the input signals from the above-mentioned sensors, the electronic control unit 16 receives input signals from the A/F sensor 29. There is a rotation speed sensor 30 and an atmospheric pressure sensor 31 for the engine 1 .

FIG. 2 shows an example of the fuel injection control by the electronic control unit 16, particularly a subroutine for controlling the fuel pressure and fuel temperature to zero.

First, in the kffi'1f2Il flow in the same figure, the illustration is 'a'
Although omitted, the fuel injection location is determined by the following procedure.

After initializing the system, the engine 1 rotation speed N signal from the rotation speed sensor 30 and the intake air ff1Q (i) from the air flow sensor 12 are read, and the basic injection amount τa from the fuel injection valve 11 is calculated. It is calculated based on the following formula according to the engine speed N and intake air flQ: τa = <Q/N)XK K: injection ratio conversion coefficient.

When the fuel injection rFJ is set, the subroutine shown in FIG. 2 starts, and first, in step S1, the atmospheric pressure sensor 3 is
Atmospheric pressure values P from 1 are sampled.

Next, the fuel temperature TF from the fuel temperature sensor 24 and the fuel pressure F) from the fuel pressure sensor 23 are determined in step 8.
2. It is sampled at S3.

In step S4, the atmospheric pressure value P is 1 atm, that is, 760
It is determined whether or not it is higher than mm HIJ, and the atmospheric pressure value P
If is higher than this, the target fuel pressure PC9 at standard atmospheric pressure (1 atm) is not corrected to the target fuel temperature TC, and the process moves to the next step.

On the other hand, if it is determined in step S4 that the atmospheric pressure value P is smaller than 760 mm H, step S5 is executed.

In step S5, first, the differential pressure (ΔP) between the atmospheric pressure value P and 760 mmHg is determined from the target fuel pressure pc, and is set as a new target fuel pressure Pc -.

In this example, if the fuel pressure () is decreased, the target point A (Pc, Tc> shown in FIG. 3 enters the unstable region where liquid and gas coexist, so the new target fuel temperature TC- is set as follows.

First, the target fuel temperature Tc, Tc = is set on the curve B located above the saturated steam pressure line in the phase diagram of Fig. 3, and is determined as a pressure box Wlt = f(P). put.

Then, when the target fuel pressure is changed from pc to Pc =, the amount of change Δt to change the target fuel temperature from Tc to TC- is calculated from the above function t=f(P), and from the target fuel temperature TO A new target fuel temperature T is obtained by subtracting ΔT.
c- is set.

In each step above, the target fuel pressure Pc or Pc −
When the target fuel temperature 1”c or Tc- is set,
In step 8B, the current fuel pressure PF and Pc - (Pc
) is calculated, and if the value is within a predetermined range α, the process moves to the next step, but if it is outside the range, step $7 is performed so that the fuel pressure PF is within the range α. The fuel pressure regulator 21 is controlled.

When the fuel pressure PF falls within the predetermined range α from the target fuel pressure Pc - (Pc), in step 3.5, the absolute value of the difference between the current fuel temperature T' and Tc' (Tc) is determined, and the If the value is within the predetermined range β, the control flow ends, but if it is outside the range, the fuel temperature T is
The heater 22 is controlled so that F is within the range of β, and the fuel temperature 1"l temperature 1]" becomes the target fuel temperature Tc - (T
c) When the value falls within +β, the subroutine ends.

The pressure and temperature of the fuel are respectively the target ratio PC' (Pc
>, Tc - (Tc), it is determined whether it is the fuel 1'N injection timing or not, and when the fuel injection timing (J) is reached, the fuel injection pulse width τa determined by the above formula is set. The corresponding fuel is injected and supplied from the fuel injection valve 11.

Now, in the fuel control device controlled as described above, the atmospheric pressure P decreases, and the target fuel pressure P set at standard atmospheric pressure is reduced.
C1 Under conditions where stable boiling under reduced pressure is possible without pressurizing or heating up to the fuel temperature Tc, a new target fuel pressure Pc- and fuel temperature Tc'' lowered by the amount lowered from standard atmospheric pressure are set. Unlike conventional devices of this kind, wasteful energy consumption is eliminated, and the burden on the fuel pressure regulator 21 and heater 22 can be reduced.

(Effects of the Invention) As described above in detail in the embodiments, according to the fuel injection m-type engine fuel-1111] device according to the present invention,
changing fuel temperature and pressure in response to changing atmospheric pressure;
Vacuum boiling! Since only the minimum amount of heating and pressurization required for boiling is performed, reduced pressure boiling can be carried out efficiently.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the apparatus of the present invention, FIG. 2 is a flowchart showing the operation of the controller, and FIG. 3 is an explanatory diagram of the state characteristics of fuel. １・・・・・・・・・Engine １１・・・・・・
Fuel injection) 1 valve 19... Fuel pump 21... Fuel pressure regulator 22... Heater

Claims (1)

[Claims] a pressurizing means for pressurizing the fuel supplied to the fuel injection valve; and a heating means for heating the fuel to a temperature at which it does not boil under the pressure applied by the pressurizing means and boils under reduced pressure when injected from the fuel injection valve. In a fuel injection engine equipped with an atmospheric pressure detection means, the fuel injection engine is equipped with an atmospheric pressure detection means, and the fuel pressure by the pressurization means or the fuel pressure by the heating means is changed according to the atmospheric pressure detected by the atmospheric pressure detection means. 1. A fuel control device for a fuel injection engine, comprising: means.