JP2611699B2 - Fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes an air assist device for atomizing fuel injected from a fuel injection valve by an injection air flow in order to improve combustion and fuel efficiency of an internal combustion engine.
The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art In order for an internal combustion engine to burn efficiently with less fuel, first, it is necessary to supply fuel to a combustion chamber in a state where combustion is most easily performed. For an internal combustion engine equipped with a fuel injection valve (fuel injector) in recent years, in order to promote atomization of fuel injected from the fuel injection valve, external air is supplied to the vicinity of the injection port of the fuel injection valve. There has been proposed a fuel injection device having an air assist device that spouts vigorously and promotes atomization of injected fuel, and further guides an air-fuel mixture of atomized fuel and assist air to near an intake valve. There has been proposed a fuel injection device in which a cylindrical member (long nozzle) for providing a mixed gas passage is mounted on a fuel injection valve (Japanese Utility Model Application Laid-Open No. 64-11364).

[0003]

However, in the fuel injection device in which the above-described cylindrical member is mounted on the tip of the fuel injection valve, the tip of the nozzle or the inner wall surface of the fuel injection valve is low when the temperature of the engine is low because the mixture passage is long. The fuel may adhere to the engine, and the atomization of the fuel may worsen, or the adhering fuel may evaporate at a stroke under certain operating conditions (for example, during deceleration), which may lower the air-fuel ratio control accuracy of the engine. Also, in addition to this fuel, moisture in the intake air may condense and adhere to the nozzle inner wall surface when the engine operation is stopped.In cold regions, such water droplets freeze, and atomized fuel is injected when the engine is started cold. In some cases, a so-called icing phenomenon may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem in the case where a mixture passage is formed ahead of a fuel injection valve in a fuel injection device which promotes atomization of injected fuel by assist air.

[0005]

According to the present invention, there is provided a fuel injection device for an internal combustion engine having an air assist device for atomizing fuel injected from a fuel injection valve by assist air in order to solve the above-mentioned problems. In the above, the fuel injection valve is formed on the downstream side in the injection direction from the injection port, from the injection port
The fuel injected and the fuel injected from the air assist holes
The mixture passage for mixing the stir air and the internal combustion engine
Heating means for heating the mixture passage when in a warm state, and an assist air supply system for controlling the supply of assist air.
Control means, wherein the assist air supply control means
The internal combustion engine is running at a high speed and the heating means is not operating
Always supplies assist air to the mixture passage,
While the internal combustion engine is at a high speed and the heating means is operating,
Only during a specific period including the fuel injection engine of the fuel injection valve,
Supplying assist air to the mixture passage.
A fuel injection device for an internal combustion engine is provided.

[0006]

When the internal combustion engine is in a low temperature state, fuel and water droplets adhering to the inner wall surface of the air-fuel mixture passage in the nozzle are heated and evaporated by the heating means, so that icing is prevented and atomization of the fuel is promoted. Air assist supply control
By means , the internal combustion engine is at high speed and the heating
During operation of the means include the fuel injection engine of the fuel injection valve
Assist air is supplied to the mixture passage only during a specific period
Therefore , the mixture passage can be prevented from being cooled by the assist air.

[0007]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a fuel injection device according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a fuel injection valve, and reference numeral 2 denotes an air assist device to be described later. An air delivery for distributing air taken in from an intake passage (not shown) of the fuel supply around the fuel injection valve 1 as assist air for atomizing fuel, and an assist air supply unit 3 for supplying pressurized air to the air delivery 2 It is.

The fuel injection valve 1 has a fuel injection port (hereinafter referred to as an injection port) 4 on its central axis A, and a needle valve 5 is provided inside the main body of the fuel injection valve 1 in the direction of the central axis A. Is reciprocally mounted.

According to the present embodiment in the fuel injection device configured as described above, a long nozzle 6 is attached to the tip of the fuel injection valve 1 along the central axis A.

An air-fuel mixture passage 7 is formed inside the long nozzle 6 so as to extend from the injection port 4 to the downstream side in the fuel injection direction along the central axis A, and the air-fuel mixture passage 7 and the air delivery are further formed. Air assist holes 9a and 9b communicating with the inner space 8 are formed. That is, the fuel injected from the injection port 4 of the fuel injection valve 1 and the air (assist air) supplied from the air assist device are uniformly mixed by the mixture passage 7 to further atomize the fuel.
An O-ring 10 and an insulator 11 for sealing the internal space 4 from the outside are mounted between the air delivery 2 and the fuel injection valve 1.

In this embodiment, the mixture passage 7 is branched into two passages 7a and 7b near the front end of the long nozzle 6, and is opened with mixture ejection ports 12a and 12b. The branch passages 7a and 7b are such that the atomized fuel flowing through the mixture passage 7 is equally divided, and in the case of the present embodiment, is injected toward two intake valves (not shown). Then, it is inclined at a predetermined angle with respect to the central axis A.

Further, according to the present embodiment, as means for heating the above-described mixture passage 7, a heater 13 is provided on the fuel injection valve 1 so as to cover the long nozzle 6 along its longitudinal direction.
Is provided. The heater 13 has, for example, a positive temperature characteristic (PTC) having a positive temperature characteristic indicating that the heater resistance increases when a certain temperature (Curie point) is reached.
nt) By using a heater, it is possible to ensure quick heat at low engine temperature, and to suppress heat generation by making it difficult for current to flow when the temperature of the fuel injection device rises to a low level where fuel and water droplets are unlikely to adhere. May be. In FIG. 1, 14
Numeral 15 denotes an O-ring, and numeral 16 denotes an electrode for a heater.
Note that the heating means of the present invention is not limited to the above-described heater 13, and may be integrally formed so as to have the above-mentioned mixture passage 7, though not shown.

The air assist device is the air delivery 2 described above.
And an assist air passage 17 for guiding air from an intake passage upstream of the throttle valve to the assist air supply unit 3, and the assist air passage 1.
7 is provided with an air pump 18 provided in the middle. The air pump 18 pressurizes the air taken in from the intake passage and supplies it to the assist air supply unit 3. The air pump 18 is located in the assist air passage 17 and downstream of the air pump 18. A pressure control valve 19 for controlling air to a constant pressure, and an assist air control valve 20 for communicating and blocking the assist air passage 17 are provided.
The assist air control valve 20 is controlled to open and close by a control circuit 21. Incidentally, the assist air control valve 20 and the control circuit 21 in the present embodiment correspond to the present invention.
This corresponds to assist air supply control means .

The fuel injection valve 1 and the heater 13 are connected to the control circuit 21 in addition to the above-described assist air control valve 20, and these are operated via drive circuits 22, 23 and 24, respectively. Has become. Various other driving signals are output from the control circuit 21, but they are not directly related to the present invention, and thus are omitted.

On the input side of the control circuit 21, a starter signal ST from an ignition switch 25, a water temperature signal THW from an engine cooling water temperature sensor 26, and an engine speed sensor (crank angle sensor) 28 provided in a distributor 27 are provided. In addition to the rotation speed signal N, various signals are input. Then, the control circuit 21 operates the fuel injection valve 1, the assist air control valve 20, and the heater 13 based on the present operating conditions detected by these signals.

Hereinafter, an operation example of the fuel injection device having the above-described configuration will be described with reference to FIG.

The needle valve 5 is synchronized with the intake stroke of each cylinder.
Is operated, the fuel in the fuel injection valve 1 becomes
The fuel is injected from the injection port 4 into the mixture passage 7, while the assist air (pressurized air) is generated by an air pump 18 and controlled to a constant pressure by a pressure control valve 19. The assist air is supplied to the air delivery 2 via the assist air control valve 20 and the assist air supply unit 3 in the open state.
And is discharged from the air assist holes 9a and 9b into the air-fuel mixture passage 7.

According to the illustrated embodiment, the connection between the air-assist hole and the air-fuel mixture passage, which serves as a junction between the injected fuel and the assist air, is a mixture air passage extending along the central axis A starting from the injection port 4. 7, the fuel injected from the fuel injection valve 1 is set near the injection port 4.
Immediately, it collides with the assist air injected from the air assist holes 9a and 9b and is atomized. The fuel atomized in this manner flows through the mixture path 7 toward the tip of the long nozzle 6, and in this flow process, the atomized fuel is sufficiently mixed with the assist air, and the flow direction component is also reduced. More uniform.

As described above, the air-fuel mixture stabilized in the mixing and flow directions is almost equally divided and injected toward the respective intake valves from the respective air-fuel outlets 12a and 12b. .

The above-described operation is an example of the operation of the fuel injection device during normal operation of the engine in this embodiment (for example, when the engine speed is higher than 3000 rpm and the engine water temperature is higher than 60 ° C.). In addition to this, when the engine water temperature is low, for example, during a cold start, the heater 13 is operated (energized) and generates heat before the start of the engine. FIG. 2 is a flowchart illustrating an operation example of the control circuit 21 related to the energization control of the heater 13.

According to this flowchart, first, in step 21, the output from the ignition switch 25 is read, and the state where the starter signal ST is not currently output (OF
F), it is determined whether or not No, that is, if the starter signal ST is currently output to start the engine (ON), the process proceeds to step 24, in which the power supply to the heater 13 is stopped. Secure enough power to start the engine. On the other hand, if Yes in step 21, the routine proceeds to step 22 in which the output signal THW from the engine coolant temperature sensor 26 is fetched and whether or not the engine coolant temperature is, for example, 60 ° C. or less, that is, whether or not the engine is in a low temperature state. Is determined. If the result of step 22 is Yes (low temperature state), the operation proceeds to step 23 to output an operation signal to the drive circuit 24 so as to energize the heater 13.

When the heater 13 is heated in this manner, the mixture passage 7 (branch passages 7a, 7a) of the long nozzle 6 is heated.
b) is also heated, and the fuel and water droplets (including ice by icing) attached to the inner wall surface evaporate, thereby promoting the atomization of the fuel. It should be noted that when the determination in step 22 is No, that is, when the engine is in a warm-up state, the fuel and water droplets do not adhere to the inner wall surface of the mixture passage 7 or the tip of the long nozzle 6, so that step 2
Proceeding to 4, the power supply to the heater 13 is stopped.

By the way, in the apparatus according to the present embodiment, the heater 13 is heated at the time of low temperature of the engine as described above, but the assist air is constantly ejected from the air assist holes 9a and 9b as in the conventional air assist apparatus. In this case, the heated mixture passage 7 is cooled by the assist air, and there is a possibility that the amount of heat sufficient to vaporize the attached fuel and water droplets cannot be secured. FIG.
FIG. 9 is a flowchart showing control of an assist air control valve 20 of an air assist device which is another feature of the fuel injection device of the present invention as a measure against such a case.

First, at step 31, the output signal THW of the engine coolant temperature sensor 26 is fetched, and it is determined whether or not the engine coolant temperature is, for example, 60 ° C. or lower, that is, whether or not the engine is in a low temperature state. And in this step 31 Ye
s, that is, when the engine is in a low temperature state, there is a problem of supercooling if the assist air is introduced into the air-fuel mixture passage 7. Therefore, the routine proceeds to step 32, and executes a discontinuous air assist process described later.

On the other hand, if No in step 31, the routine proceeds to step 33, in which the current engine speed Ne is read from the engine speed sensor 28 and compared with a relatively small predetermined speed of 3000 rpm, for example. ,
It is determined whether the rotation speed is equal to or lower than the rotation speed. And this step 3
If Yes in 3 (low rotation range), the routine proceeds to step 32
To perform the above-described discontinuous air assist processing. This is because if the current operating state is in the idle, low-speed, light-load range where the amount of injected fuel is small, and if the assist air is constantly supplied by the air assist device at this time, the intake air amount becomes excessive, Since there is a problem that the number increases, the air assist is discontinuous to suppress an increase in the intake air amount.

On the other hand, if No in step 33, that is, if the engine is currently in the warm-up state and is not in the low speed range, the routine proceeds to step 34, in which the assist air control valve 20 of the air assist device is constantly opened. Continuous air assist processing such as outputting a signal for operating the valve is performed, and the routine ends.

FIG. 4 is a timing chart for explaining a specific example of the discontinuous air assist processing in the above-mentioned step 32, in which the time (crank angle) is plotted on the horizontal axis, and the upper row shows the intake valve of a specific cylinder. In the valve opening period (not shown), the middle stage shows the drive signal output timing of the fuel injection valve 1 provided in this cylinder (that is, the fuel injection period), and the lower stage shows the air assist control valve 2
Output timing of the valve opening drive signal of 0 (that is, the air assist period)
It shows.

That is, as is apparent from this figure, the discontinuous air assist processing in the present embodiment includes the fuel injection period when the engine temperature is low or when the engine speed is low after warm-up. The air assist is executed only for a short period to promote the atomization of the fuel, and the drive signal output to the air assist control valve 20 is turned off at other times (ie, other than near the time of fuel injection) to reduce the supply air amount in one cycle. This is set to be smaller than usual, and the cooling of the air-fuel mixture passage 7 is suppressed (when the temperature is low), or the increase in the engine speed due to the excessive intake air amount is suppressed. The opening control of the air assist control valve 20 for achieving the continuous or discontinuous air assist as described above is performed by the air assist control valve drive circuit 22 in the same manner as the normal drive control of the fuel injection valve 1. When the discontinuous air assist process is determined in step 32 (for example, a flag is set) in the control circuit 21, the predetermined fuel A program for outputting a signal to the drive circuit 22 only during a stop period near the injection point (executed at every predetermined crank angle) is stored.

In the discontinuous air assist processing example described above, the same air assist stop period is set for both when the engine temperature is low and when the engine speed is low after warm-up. The assist process may be set for each case.

As described above, according to this embodiment, in addition to the original effect of the heating means, the long nozzle 6
Is provided, the flow of the assist air in the air-fuel mixture passage 7 is stabilized, and the air-fuel mixture can be injected with a more uniform flow velocity and concentration. Further, the distance between the fuel injection point and the intake valve can be shortened by the long nozzle 6, so that the amount of fuel deposited on the port wall can be reduced.

In addition, according to the present embodiment, since the air assist and the mixture passage heating are executed for a limited period according to the operation state at that time, the capacity of the installed air pump and heater can be designed to be small. Therefore, power consumption can be reduced.

Although the embodiment of the present invention has been described based on the example of the fuel injection device shown in FIG. 1, the form of the mixture passage is not limited to this embodiment, and the number of branch passages is also two. It is not limited to one. Further, needless to say, the heating means is not limited to the PTC heater, and may be a known heater having excellent temperature-rise characteristics.

[0034]

As described above, according to the present invention ,
When the fuel engine is in a low temperature state, fuel, water droplets or ice adhering to the inner wall surface of the air-fuel mixture passage in the nozzle is heated and evaporated by the heating means, so that icing is prevented and atomization of the fuel is promoted. In addition, the internal combustion engine operates at a high speed.
And during the operation of the heating means, the fuel
Only during a specific period including the fuel injection engine,
Since the cyst air is supplied, the mixture passage can be prevented from being cooled by the assist air.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection device as one embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of heater control performed by the fuel injection device of the present invention.

FIG. 3 is a flowchart illustrating a control example of an assist air control valve executed by the fuel injection device of the present invention.

4 is an operation timing chart of an assist air control valve that can be achieved by the flowchart of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 6 ... Long nozzle 7 ... Air-fuel mixture passage 13 ... Heater 20 ... Assist air control valve 21 ... Control circuit

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-63648 (JP, A) JP-A-61-112773 (JP, A) JP-A-57-146050 (JP, A) JP-A 54-63 53714 (JP, A) JP-A-56-6056 (JP, A)

Claims (1)

(57) [Claims] 1. A Assist the fuel injected from the fuel injection valve
A fuel injection system for an internal combustion engine having an air assist device for atomization by Toea, formed in the injection direction downstream side of the nozzle holes of the fuel injection valve,
Fuel injected from the nozzle and air injected from the air assist hole
And heating the mixture passage when the internal combustion engine is at a low temperature.
Heating means and the assist air supply control hand for controlling the supply of assist air that
And wherein the assist air supply control means is configured to determine whether the internal combustion engine is rotating at a high speed and the heating means is not operating.
Always supplies assist air to the air-fuel mixture passage so that the internal combustion engine is running at a high speed and the heating means is operating.
Is a specific period including the fuel injection period of the fuel injection valve
Supply of assist air to the mixture passage.
A fuel injection device for an internal combustion engine.