KR20160063872A - Method of fuel injection during cold start - Google Patents

Abstract

The present invention relates to a fuel injection method during cold start. The present invention relates to the fuel injection method during cold start, comprising: a step in which an injection valve performs pre-injection of a fuel to shield a low temperature on a surface of a combustion room, or an intake port formed under a cold start environment of an intake port area; a step in which the pre-injected fuel surrounds a wall of the intake port area in a liquid film state; a step of performing main injection of the fuel to supply the fuel to a combustion room area after an established time has passed; a step in which an intake valve is opened, and the main-injected fuel supplied into a cylinder; and a step of igniting a mixture of the fuel and air through an ignition plug. The fuel injection method of the present invention is able to reduce heat loss in the intake port area and the combustion room area.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of fuel injection during cold start,

The present invention relates to a fuel injection method for cold start in a port fuel injection type engine, and more particularly, to a fuel injection method for injecting fuel into a fuel injection device in order to shield a low temperature of an intake port formed in a cold start environment. The first injected fuel wrapping the wall of the intake port region in a liquid film state; Secondarily injecting fuel to be supplied to the combustion chamber region after a predetermined time has elapsed; The intake valve is opened and the secondary injected fuel is fed into the cylinder; Igniting the fuel and air mixture through an ignition plug; The present invention relates to a cold start-up fuel injection method.

Engines employing fuel injection, referred to as Port Fuel Injection (PFI) or port injection, use a variety of fuels (gasoline, ethanol, mixed fuels, etc.) in countries with varying climatic conditions, There is a difference in the starting performance depending on the combustion characteristics of the fuel and the climate of each country (in particular, the outside air temperature). In particular, in countries with very low temperatures, the characteristics of fuel depend on the fuel. However, the problem of 'start-up at cold start', in which start-up performance deteriorates due to insufficient combustion of fuel during start-up, A number of techniques have been developed to improve the performance.

In a conventional Single Point Injection (SPI) engine, the injector is installed in a place before the intake manifold branches, and the temperature of the engine cylinder and the intake manifold is lower than the temperature of the fuel at the time of cold start The phenomenon of heat loss occurring at a low temperature is relatively large because the injected fuel stays in the wall of the intake manifold for a relatively long period of time and thus the combustion performance of the fuel is further lowered and the starting performance is adversely affected .

In addition, in the case of a conventional multi-injection (MPI) type engine, injectors as many as the number of cylinders of the engine are installed in each intake manifold, and fuel injection is performed for each stroke of each cylinder. Although there is less cold startability problem due to heat loss, there is still a problem in start up due to the intake manifold and the combustion chamber wall being cooled in a very low temperature starting environment.

In the case of a conventional heated injector system developed to solve such a problem, the temperature of the fuel is higher than that of the general system to compensate for the cold startability. However, in the conventional single injection type engine There is still a problem that heat loss phenomenon still occurs and the heat energy of the heated fuel can not be fully utilized.

In addition to the above method of integrating the heater into the injector or heating the fuel supply pipe to raise the fuel temperature to accelerate the atomization, However, there has been no technology for eliminating the heat loss caused by cold engine components in the cold start environment.

Korean Patent Publication No. 2005-0069275

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique for reducing heat loss in an intake port region and a combustion chamber region where heat loss occurs during cold start in a port injection type engine.

That is, in order to shield the cold manifold wall surface temperature in the intake manifold region immediately before each cylinder of the engine, the fuel is injected first so that the injected fuel surrounds the wall of the intake port region in a liquid film state, The fuel to be supplied to the combustion chamber region is secondarily injected so as to reduce the heat loss in the intake port region and the combustion chamber region.

The technical problem to be solved by the present invention is not limited to the above-mentioned technical problems, and various technical problems can be included within the scope of what is well known to a person skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of injecting fuel during cold start in an engine of a port fuel injection type, the method comprising the steps of: (a) Firstly injecting fuel into the intake port region with a fuel injector to shield the low temperature of the intake port or the cylinder wall surface; (b) surrounding the wall of the intake port region with the first injected fuel in a liquid film state; (c) secondarily injecting fuel for supplying to the combustion chamber region after a predetermined time has elapsed.

In the fuel injection method according to an embodiment of the present invention, the intake port region is a region surrounded by the intake manifold inner surface and the intake valve upper surface. In the combustion chamber region, Wherein the internal combustion engine is a four-stroke engine including a plurality of cylinders.

According to another aspect of the present invention, there is provided a method of injecting fuel at a cold start, the method comprising the steps of: injecting fuel to be supplied to a combustion chamber region in a second stage, And the secondary injection of the fuel is started at a point located between the 1/2 point and the 3/4 point of the entire stroke.

According to another aspect of the present invention, there is provided a method of injecting fuel at a cold start, comprising the steps of: injecting fuel to be supplied to a combustion chamber region in a second stage, And the secondary injection of the fuel is started at a point located between the 1/4 point and the 1/2 point of the entire stroke.

The fuel injection method according to an embodiment of the present invention includes a plurality of injectors installed in a plurality of cylinders for simultaneously injecting fuel into the intake port and the combustion chamber formed in the cold starting environment, Or immediately after the intake valves are closed in each of the plurality of cylinders, the fuel is firstly injected.

Also, a method of injecting fuel at a cold start according to an embodiment of the present invention includes the steps of: (d) opening an intake valve and supplying fuel injected into a cylinder; (e) igniting the fuel and air mixture by an ignition plug; As shown in FIG.

In addition, in the cold start-up fuel injection method according to an embodiment of the present invention, when the engine starts normally and the engine is operated, the internal combustion engine is operated only by the secondary injection without the primary injection.

Meanwhile, the cold start fuel injection method according to an embodiment of the present invention may be implemented as a controller equipped with a control logic for executing the method.

The present invention can reduce the heat loss in the intake port region and the combustion chamber region when compared with the conventional injection control method during the cold start and can increase the residence time of the spray fuel in the combustion chamber So that the atomization of the fuel is further promoted and the combustion efficiency can be increased.

In addition, it is possible to improve the response speed of the vehicle to the driver's intention of driving by providing a smooth starting performance compared with the existing technology, and if the start failure is repeated at the cold start, environmental pollution may be caused by incompletely burned exhaust gas. By increasing the starting success rate through the invention, it is possible to reduce the degree of air pollution caused by the exhaust gas and to reduce the battery consumption according to the operation of the cranking motor.

Moreover, the control logic for implementing the fuel injection method of the present invention can be mounted on an existing controller without having to manufacture related peripherals separately or to combine additional components, which can be advantageous in terms of system cost and application.

1 is a conceptual diagram of an operation cycle in a conventional port injection type engine.
2 is a configuration diagram of a conventional heating type injector system.
3 is an exemplary view showing a structure of a cylinder to which the fuel injection method according to the present invention can be applied.
4 is an exemplary view showing a fuel injection process during cold start of the present invention.
5 is an exemplary view showing the fuel injection method during cold start according to the present invention in relation to each stroke.
FIG. 6 is an exemplary view showing the first embodiment according to the fuel injection method according to the present invention for each cylinder.
FIG. 7 is an exemplary view showing a second embodiment according to the fuel injection method according to the present invention for each cylinder.

Hereinafter, the 'fuel injection method during cold start' according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the scope of the present invention. In addition, the matters described in the attached drawings may be different from those actually implemented by the schematic drawings to easily describe the embodiments of the present invention.

In the meantime, each constituent unit described below is only an example for implementing the present invention. Thus, in other implementations of the present invention, other components may be used without departing from the spirit and scope of the present invention. In addition, each component may be implemented solely by hardware or software configuration, but may be implemented by a combination of various hardware and software configurations performing the same function. Also, two or more components may be implemented together by one hardware or software.

Also, the expression " comprising " is intended to merely denote that such elements are present as an expression of " open ", and should not be understood to exclude additional elements.

FIG. 1 is a conceptual view showing an operation cycle in a conventional port injection type engine, in which fuel injection in each cylinder at a room temperature condition is started at the latter half of the combustion stroke and lasts until the end of the exhaust stroke.

In the conventional port injection system, the internal surface temperature of the intake port region and the combustion chamber region is lower than that of the fuel at the time of cold start, resulting in a heat loss phenomenon. As a result, the combustion performance of the fuel is further deteriorated, There is a disadvantage that it adversely affects.

In order to overcome the problem of cold startability, a heated injector system as shown in FIG. 2 has been developed. This system can improve the cold startability by increasing the temperature of the fuel than the general system. However, Is still applied to the conventional single injection method, the heat loss phenomenon still occurs and the heated fuel can not be fully utilized.

Therefore, there is a problem that the problem of the cold start can not be sufficiently solved only by the conventional injection method or the method using the heating type injector.

3 is an exemplary view showing a structure of a cylinder to which the fuel injection method according to the present invention can be applied.

Referring to FIG. 3, an engine to which the fuel injection method according to an embodiment of the present invention can be applied includes an injection valve 100, an intake port region 101, an intake manifold 102, an ignition plug An intake valve 111, an exhaust valve 112, a piston 120, and a combustion chamber area 130. The intake valve 111, the exhaust valve 112, the piston 120,

Among the internal combustion engines to which the fuel injection method of the present invention is applied, in the case of a four-stroke engine, there are an intake stroke that receives fuel and air into the cylinder, a compression stroke in which the mixture of fuel and air in the cylinder is compressed by the piston, An explosion stroke which is ignited by the ignition plug to generate a sudden exothermic reaction and which obtains a force for moving the organ by the expansion which occurs at this time, and an exhaust stroke for discharging the gas which has undergone the reaction to the outside of the engine.

In the intake stroke, the piston descends from the top dead center (TDC) to the bottom dead center (BDC), and as the internal pressure of the cylinder lowers, air is pushed into the intake manifold, And becomes a mixer. Thereafter, the mixer is introduced into the cylinder through the intake valve, and the crankshaft rotates to fill the mixer in the cylinder.

In the compression stroke, with the intake valve and the exhaust valve both closed, the piston compresses the mixer while rising from the bottom dead center (BDC) to the top dead center (TDC). At this time, the crankshaft rotates once, and as the rotation speed of the engine becomes faster, the compression ratio increases.

In the explosion stroke, the piston is lowered by pushing the piston by the pressure of the combustion gas generated while the mixer inside the cylinder is burned, and power is generated in this process. In gasoline engines, spark ignition through a spark plug will burn.

In the exhaust stroke, the exhaust valve is opened and the piston rises to the TDC (top dead center), and the combustion gas is pushed up and discharged out of the cylinder. The crankshaft will make a total of two rotations.

In order to improve the cold startability of the conventional engine, fuel injection is performed at a time point when the piston is closer to the top dead center position by slowing the injection timing from the fuel injection timing under the normal starting condition under the cold starting condition, It is possible to consider a method of improving the cold startability by shortening the residence time in which the fuel is deprived of heat.

That is, the fuel injection performed from the second half of the explosion stroke to the middle half of the exhaust stroke during the normal startup under normal temperature conditions is retarded so as to be performed from the second half of the exhaust stroke to the first half of the intake stroke, If the retention time is shortened, the effect of improving the heat loss in the combustion chamber area can be partially expected.

However, if the residence time of the fuel in the combustion chamber is shortened by delaying only the injection timing of the fuel, the heat loss improvement effect in the combustion chamber region can be partially expected. However, when the injection timing is too close to the top dead center, There is a problem that the time for the fuel to be fully atomized is not ensured, resulting in a negative effect on the combustion efficiency of the fuel.

Accordingly, in the present invention, as shown in FIG. 4, the fuel injection step is divided into two steps. First, the fuel is first injected to shield the low temperature of the intake port wall formed in the cold starting environment, Thereby forming a liquid film on the wall surface of the intake port, thereby improving the heat loss in the intake port region.

In the second stage, as described above, the injection timing of the fuel is perceived as compared with the case of the normal temperature starting, but the delay time of the injection timing is made smaller than that of the first stage, .

That is, the primary injection may be a pre-injection to form a fuel oil film on the surface of the intake port to improve the heat loss in the intake port area, and the secondary injection may improve the heat loss in the combustion chamber area In order to delay the injection timing in order to inject the fuel for combustion, it may be called main injection.

The method of injecting fuel at a cold start according to an embodiment of the present invention includes the steps of: (a) injecting a low-temperature fuel into the intake port or the surface of a combustion chamber formed in a cold start- Firstly injecting the fuel for the first time; (b) surrounding the wall of the intake port region with the first injected fuel in a liquid film state; (c) secondarily injecting fuel to be supplied to the combustion chamber region after a predetermined time has elapsed; (d) an intake valve is opened, and the fuel injected into the cylinder is fed into the cylinder; (e) igniting said fuel and air mixture through an ignition plug; .

At this time, if the cold start is normally performed and the engine is operated, the internal combustion engine can be operated only by the secondary injection (main injection) without the first injection in the repeated driving of the stroke, In a fully heated state, only normal injection may be performed without a perception of the injection timing.

In addition, the present invention may be implemented by a controller equipped with control logic configured to execute the respective steps of the fuel injection method at the time of cold start, or may be realized by a controller configured by a controller.

The present invention is further described in detail below with reference to the accompanying drawings. It should be noted that, prior to the main injection or effective injection for injecting the fuel to be used for combustion at the start of the engine, the low temperature of the intake port or the combustion chamber surface formed in the cold start- Pre-injection is performed first to shield. The primary injected fuel wall-wetts the wall of the intake port region in the form of a liquid film, and the wall of the intake port region coated with the fuel at a relatively high temperature is displaced from a low temperature. Preferably, the fuel injection method of the present invention further enhances the coating effect by the high temperature fuel when the fuel is heated by the heating type injector.

The intake port region may include the intake manifold 102 as well as the intake passage 101 which is a narrow space between the injector serving as the fuel injector and the cylinder. Depending on the ambient environment such as the temperature and humidity outside the vehicle, The fuel injected first may be wrapped in a liquid film only in the intake manifold or wrapped in a liquid film form to the intake valve.

5, in a four-stroke engine, a cylinder is divided into a compression stroke (bottom dead center → top dead center), an explosion stroke (top dead center → bottom dead center), an exhaust stroke (bottom dead center → top dead center), an intake stroke Point → bottom dead center). During normal startup at normal temperature rather than cold start, the main injection starts at the latter half of the explosion stroke and stops at the middle of the exhaust stroke.

However, it is the first embodiment of the present invention that, at the time of cold start, the injection is started later than the general injection timing in the vicinity of TDC where the temperature in the cylinder is highest. In this case, when the piston advances from the bottom dead center of the exhaust stroke to the top dead center, the injection delay is delayed between the 1/2 point and the 3/4 point of the total stroke length, .

However, if the fuel injection timing is delayed too much, the temperature can be increased. However, since the atomization time during which the fuel is blown and granulated is reduced, sufficient atomization time can not be ensured. 2, the fuel is firstly injected to reduce the heat loss in the intake manifold, thereby reducing the heat loss of the fuel in the intake manifold. As a result, the main injection timing of the fuel is advanced, If the piston moves from the bottom dead center of the exhaust stroke to the top dead center, the secondary injection (primary injection) of the fuel between the 1/4 point and the 1/2 point reduces the heat loss and increases the ignition time to increase the combustion efficiency. It can be planned.

The point at which the secondary injection timing is delayed in the exhaust stroke is selected to maximize the effect of reducing the heat loss by injecting it immediately before the start of the intake stroke as in the first embodiment in accordance with the ambient environment such as temperature or humidity outside the vehicle Alternatively, as in the second embodiment, the atomization time can be sufficiently secured to increase the combustion probability and increase the startup success rate.

In addition, the first injection is performed once during the cold start, and the fuel injection for obtaining the power thereafter can be performed through the repetition of the second injection and the stroke. At this time, the primary injection timing may be collectively injected simultaneously for a plurality of cylinders as shown in Fig. 6, or may be injected for a plurality of cylinders immediately after the intake valves are closed, as shown in Fig.

6, all the injection valves provided in the cylinders 0 to 3 in the four-stroke engine are firstly subjected to the first injection in order to shield the low temperature of the intake port or the combustion chamber surface formed in the cold starting environment, The injected fuel surrounds the wall of the intake port area in the form of a liquid film and the wall of the intake port area deviates from the low temperature.

When the engine starts operating normally after a preset time has elapsed, as shown in Fig. 5, between the 1/2 point of the exhaust stroke and the 3/4 point or the 1/4 point to the 1/2 point of the exhaust stroke for each cylinder The cold start can be performed by appropriately selecting the effect of increasing the combustion probability and reducing the heat loss by delayed injection of the fuel.

7, immediately after each intake valve of the intake port for supplying fuel and air to each of the cylinders 0 to 3 in each of the cylinders 0 to 3 in the four-stroke engine is closed, the wall of the intake port region is wrapped in liquid film form through the primary injection, The wall of the region is deviated from the low temperature.

After the first injection, the secondary injection starts in the exhaust stroke and ignition occurs, and then the engine is operated with only secondary injection without a separate primary injection to form a liquid film.

At this time, the injection timing of the primary injection and the secondary injection shown in Figs. 6 and 7 is appropriate for each cylinder, depending on the operating condition (rotational speed, load, temperature) of the engine, The injection valve can be selectively stopped for each cylinder, or the injection can be individually controlled.

100: injection valve
101: intake passage
102: intake manifold
110: spark plug
111: intake valve
112: Exhaust valve
120: piston
130: combustion chamber area

Claims (7)

A fuel injection method for cold start of a port injection engine,
(a) firstly injecting fuel into the fuel injection device to shield the low temperature of the intake port or the surface of the combustion chamber formed in the cold starting environment;
(b) surrounding the wall of the intake port region with the first injected fuel in a liquid film state;
(c) secondarily injecting fuel to be supplied to the combustion chamber region after a predetermined time has elapsed;
And a fuel injection valve for injecting fuel.
The method according to claim 1,
The step (c)
When the piston of the exhaust stroke advances from the bottom dead center to the top dead center, the secondary injection of the fuel starts at a time point between the 1/2 point and the 3/4 point of the entire stroke. Spraying method.
The method according to claim 1,
The step (c)
When the piston of the exhaust stroke advances from the bottom dead center to the top dead center, the secondary injection of the fuel is started at a point located between the 1/4 point and the 1/2 point of the entire stroke. Spraying method.
The method according to claim 1,
The step (a)
Wherein all of the injection valves provided in the plurality of cylinders are simultaneously subjected to the first injection in order to shield the low temperature of the surface of the intake port or the combustion chamber formed in the cold starting environment.
The method according to claim 1,
The step (a)
Wherein the first injection of the fuel is performed immediately after the intake valves of the intake port for supplying the fuel and the air to the respective cylinders are closed, respectively.
The method according to claim 1,
(d) an intake valve is opened, and the fuel injected into the cylinder is fed into the cylinder;
(e) igniting said fuel and air mixture through an ignition plug;
Further comprising the steps of:
The method according to claim 6,
Wherein the internal combustion engine is operated only with the secondary injection without the primary injection when the engine is normally started and the engine is operating.

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