JPS62243956A - Injecting method for liquefied gas - Google Patents

Abstract

PURPOSE:To improve engine starting by presuming fuel pressure or its temperature at the time of engine stop, and the quantity of fuel vapour generated in a fuel supply pipe with the lapse of time after the engine stop to correct starting fuel, and then controlling a fuel injection valve for injecting liquefied gas into a suction pipe according to the said corrected starting fuel. CONSTITUTION:Liquefied gas fuel supplied from a liquefied gas tank 4 is fed to a fuel injection valve 3 for injecting the said fuel into a suction pipe 2 through an isolation valve 6, a filter 7, and a pump 8, and excess fuel is returned into the tank 4 through a return pipe 9, a pressure regulator 10 to balance the said fuel pressure with pressure in the tank 4, and an isolation valve 11. Since fuel vapour is generated in the fuel supply pipe during the engine stop, fuel temperature 17 and its pressure 18 are detected during then, and the said generated fuel vapour is presumed on the above temperature 17 and pressure 18, and the time elapsed after the engine stop, and then a control device 13 computes starting fuel according to the number of engine revolutions, engine temperature 15, and negative suction pressure 16 in consideration of the said presumed value of the generated fuel vapour to control the fuel injection valve 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of injecting liquefied gas into an intake passage, and is used for supplying fuel to an engine of a motor vehicle or other power device.

The line that supplies liquid fuel to the spark ignition type 1/ji/ of an automobile by an injection method is such that the fuel is pressurized by a fuel pump and adjusted to a predetermined pressure by a pressure regulator, and then injected from the injection valve into the intake passage. For example, as shown in FIG. 4, the fuel inlet 2 is supplied from the fuel inlet 21 through the fuel pump 22 to the injection valve 24, and through the pressure regulator 25.
1.

(In known fuel supply systems, for example, when the area around the engine becomes high temperature after the engine has stopped, the fuel gets heated and may evaporate and generate bubbles, reducing the amount of injection from the injection valve 24 and causing engine damage.) As a countermeasure, when the fuel temperature exceeds the set temperature, the intake manifold pressure introduced into the pressure regulator 25 is switched to atmospheric pressure to increase the set pressure (and increase the injection amount). To compensate for insufficient flow due to a decrease in fuel density.

Prior to restarting, the fuel pump 22 is operated for a certain period of time, and the high temperature fuel in the supply pipe 23 is replaced with the low temperature fuel in the tank 21.

However, due to the above-mentioned fuel supply system, LPG
When injecting fuel in a liquefied manner, it is more susceptible to thermal effects than liquid fuel and easily vaporizes, producing large amounts of bubbles and causing significant pressure fluctuations. In addition, in a multi-cylinder engine/engine/engine with an injection valve 24 for each cylinder, most of the fuel inside it may vaporize because it is close to the engine/engine and is susceptible to thermal effects. , 17 Since the injection valve 24 branches from the supply pipe 23 and is a dead end,
Not only is it not possible to properly control the injection amount at the time of restart by simply changing the set pressure of the pressure regulator 25, but even if the fuel pump 22 is operated before the restart, the injection valve 2
It is impossible to drain the fuel within 4.

The present invention solves the above-mentioned problem and provides a liquefied scum injection method that can accurately inject a proper flow rate of fuel when restarting an engine even when the fuel in the heat supply system is heated. For a different purpose.

In the liquefied gas injection method according to the present invention, after the engine has stopped, the engine temperature, W! , detect at least one of the fuel temperature and fuel pressure in the fuel supply system, estimate the bubble generation rate in the fuel supply system from changes in the detected values over time after the engine is stopped, and estimate the bubble generation rate in the fuel supply system when restarting the engine. A correction coefficient for correcting the increase in the fuel injection amount is calculated by 1/1 based on the estimated bubble generation rate, and the fuel in the injection amount calculated by this correction coefficient is injected when the engine is restarted.

Example Examples of the present invention will be described based on the drawings.

In Fig. 1, a supply pipe 5 for distributing and supplying liquefied gas fuel from a fuel tank 4 consisting of a pressure-resistant container to an injection valve 3 installed in each intake passage 2 of an intake manifold connected to each cylinder (E/G/1). Shutoff valve 6. A filter 7 and a fuel pump 8 are provided in this order, and a pressure regulator 10° cutoff valve 11 is provided in this order in a return pipe 9 from the terminal end of the supply pipe 5 to the fuel tank 4, and these constitute a 12ft fuel supply system. are doing.

The shutoff valves 6 and 11 are installed for the same purpose as those generally provided for safety in systems that handle liquefied gas, and in the embodiment, they are opened and closed by electromagnetic force. Kabo/Pu8. The injection valves 3 and 1 are driven by drive signals sent from the electronic control unit 13. Also, the pressure regulator: LV-10 is the intake manifold pressure in the case of liquid/heat charge, and the fuel The gas phase part of the tank 4 is controlled pressure, and the fuel pressure of the injection valve 3 is controlled by the fuel port/port.
It is adjusted according to the differential pressure between the inlet pressure and the outlet pressure of the tube 8.

The control unit H3 has a rotation speed control installed in the machine/gear/1.
f 14 , fFjA degree sensor 15. Pressure cassette/slot provided in intake passage 2 16. An electric signal is input from a sensor installed near the injection valve 3 in the supply pipe 5 to detect the temperature sensor/sink 17, pressure sensor/s 18, and other conditions of the engine 1 and its surroundings. .

The fuel supply system 12 having such a configuration is configured such that the blow valve 6. l! is open.

Liquefied gas pressurized by the fuel pump 8 and adjusted to a predetermined pressure by the pressure regulator IO is injected from the injection valve 3 into the intake passage 2.

Controlling the injection amount by opening and closing the injection valve 12 at the duty ratio determined by the control unit 13 based on electrical signals such as engine rotational speed and intake manifold pressure is the same as sudden ratio control in a liquid injection system. be.

When the engine 1 stops and the shutoff valve 6.11 closes, the fuel pump 8. When the injection valve 3 stops, the fuel supply system 1
Liquefied gas is sealed between the two shutoff valves 6.11. In the present invention, the control unit 13 is kept in an operating state nK until a certain period of time has passed after the engine is stopped, and the input and calculation of electrical signals from the two temperature sensors 15 and 17 and the pressure sensor 18 are performed. have them do it.

Here, the state of the liquefied gas sealed in the fuel supply system 12 is controlled by the temperature 17. The temperature and bubble generation rate can be determined directly by the pressure case/sustainer 18. Further, it is thought that there is a primary relationship between the temperature of the engine 1 and the temperature of the enclosed liquefied gas, and the temperature of the liquefied gas and the bubble generation rate can be indirectly detected from the temperature change after the engine 1 is stopped. Furthermore, it is also possible to indirectly detect the temperature of the liquefied gas and the bubble generation rate by integrating the operating state of the engine 1 before it is stopped, changes in engine/engine temperature after the engine is stopped, changes in liquefied gas pressure, etc.

In addition, it is especially important to know the bubble generation rate inside the injection valve 3, so make sure that the injection valve 3 is installed in a location that is easily affected by the heat of the engine. In consideration of this, it is preferable to detect the temperature change after the engine 1 is stopped and use it as a parameter for calculation processing.

Figure 2 shows an example of changes over time in the engine temperature and the bubble generation rate of the enclosed liquefied gas after the engine stops, and shows the positional relationship between the engine L and the injection valve 3 and their Although there are some differences depending on the adiabatic state during the period, it reaches a maximum after a certain time depending on the engine temperature, and then decreases to a constant value as the engine temperature decreases.

The fuel injection amount R is R=Ro(K
(RAt +RA2) 10 RT) (However, ni: correction coefficient, Ro: basic injection amount.

RAI: Start-up amount increase, RA2: After-start amount increase, RTy (engine temperature correction). The correction coefficients for the elapsed time after the engine is stopped and the bubble generation rate at that time are set in the control unit 13 and are determined based on the two-hour proportionality or based on a map with respect to time. The values of the correction coefficients corresponding to the bubble generation rate shown in Fig. 2 follow the same trace as shown in Fig. 2,
The correction coefficient Ko when the bubble generation rate becomes a constant value is stored in the control unit 13.

In addition, the correction coefficient is when the engine l is stopped.

It is automatically set to a constant value of 1 corresponding to the engine temperature at that time, and thereafter changes to correspond to the bubble generation rate.

The control unit 13 maintains the operating state for a sufficiently long period of time until the correction coefficient Ko is determined, but the control unit 13 maintains the operating state for a sufficiently long period of time until the correction coefficient Ko is determined.
You may.

When the engine 1 is restarted, the injection valve 3 is coarsely opened and closed at a ratio at which the injection IIH fuel calculated by the correction coefficient KoK determined as described above is supplied.

It goes without saying that when the engine 1 is restarted while the control unit 13 maintains the operating state n, the injection amount Rik is set based on the correction coefficient K calculated at that time.

After the engine 1 is started, the air bubbles in the supply pipe 5 and the injection valve 3 are injected into the intake pipe 2 or returned to the fuel tank 4, and are gradually reduced.

Therefore, the correction coefficient K is gradually set to a smaller value so as to gradually reduce the injection amount per unit time determined by the injection amount per opening/closing operation of the injection valve 3 and the number of injections.

Correct the injection amount R. An example of the relationship between the correction coefficient after engine startup and the injection amount R is shown in FIG.

According to the present invention, after the engine is stopped, the engine temperature, the fuel temperature in the fuel supply system, and the low pressure are detected, and the bubble generation rate is estimated from the change over time, and the engine is restarted. This is because the injection amount is determined by calculating the correction coefficient for the increase/amount of fuel injection amount at the time.

The injection amount is corrected according to the bubble generation rate of liquefied gas that is easily affected by heat (which easily generates bubbles), and the fuel can be accurately injected at the appropriate flow rate to ensure engine restart. be.

[Brief explanation of drawings]

Figure 2 is a diagram showing the layout of the embodiment of the present invention, Figure 2 is a diagram showing changes over time in the engine temperature, bubble generation rate, and correction coefficient after the engine is stopped, and Figure 3 is a diagram showing the correction coefficient and injection amount after the engine is started. FIG. 4 is a layout diagram of a conventional example. l...Engine, 2...Intake path, 3.
...Injection valve, 4...Fuel tank, 5...
-... Supply pipeline. 8...Fuel pump, 9...Return pipe,
12... Fuel supply system, 13... Control l
15.17...Temperature sensor, 18...Pressure sensor. I

Claims (1)

[Scope of Claims] After the engine has stopped, at least one of the engine temperature, the fuel temperature in the fuel supply system, and the fuel pressure is detected, and the change in the detected value with the passage of time after the engine has been stopped is detected. A correction coefficient for correcting the increase in fuel injection amount when restarting the engine is calculated based on the estimated bubble generation rate, and the fuel injection amount calculated by this correction coefficient is used when restarting the engine. A liquefied gas injection method characterized by injection at the time of startup.