JPH0797970A - Air-assisted fuel injection device - Google Patents

Abstract

PURPOSE:To provide an air-assisted fuel injection device which can atomize sprayed fuel without using exhaust gas and increasing idle speed. CONSTITUTION:An intake system 1 is provided with a spiral intake manifold surrounding a surge tank 3, and an injector 11, a delivery pipe 13, a pressure regulator 15, and a return pipe 17, etc., are disposed within the surge tank 3. The injector 11 has its end portion 11a inserted into a mounting cylinder 25 in the surge tank 3 and held in place in such a way as to be capable of injecting fuel into the intake manifold 5. An air assist passage 27 communicating with the inside of the mounting cylinder 25 from the surge tank 3 is formed in the mounting cylinder 25. Air in the surge tank 3 is not contaminated as is exhaust gas, and since the surge tank 3 is located downstream of a throttle, engine speed is not increased during idle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-assist type fuel injection device for atomizing fuel injected from an injector.

[0002]

2. Description of the Related Art Conventionally, an air inlet is provided near an injection hole of an injector, and an air flow (assist air) flowing from the air inlet increases the flow velocity of air near the nozzle hole of the injector to inject the air. There is known an air-assist type fuel injection device that promotes atomization of the fuel. For example, in the fuel injection device described in Japanese Utility Model Publication No. 3-1261, the high temperature exhaust gas is guided to the air inlet to be used as assist air to promote atomization of the fuel.

[0003]

However, according to such a conventional technique, since the exhaust gas is introduced as the assist air, the assist air passage to the air introduction port, the tip of the injector, and the injection hole are apt to be contaminated. It was In particular, when the amount of adhered carbon or the like increases, there is a problem that the flow rate of assist air and the fuel injection amount of the injector decrease. On the other hand, it is possible to purify the assist air by using a filter or the like, but this causes a new problem that the pressure loss due to the filter increases and the flow rate of the assist air decreases. Further, if hot exhaust gas is introduced, the tip portion of the injector may deteriorate early.

The above publication also discloses an example in which exhaust gas and intake air are switched to assist air depending on temperature conditions. When the assist air is switched to the intake air, the above-mentioned problems due to the introduction of the exhaust gas do not occur. However, since the intake air is introduced from the upstream side of the throttle, a certain amount of air always flows in from the assist air passage regardless of the opening of the throttle valve. That is, when the accelerator is loosened to reduce the opening degree of the throttle valve, particularly when the throttle valve is fully closed and in the idle state, more air than necessary is continuously sucked through the assist air passage. As a result, there has been a problem that the idle speed exceeds the desired speed and rises.

It is therefore an object of the present invention to provide an air-assist type fuel injection device which can atomize the injected fuel without using exhaust gas and without increasing idle speed.

[0006]

In the present invention, therefore, an intake pipe for supplying air to the internal combustion engine, and a throttle valve provided in the intake pipe for adjusting the amount of air supplied to the internal combustion engine. A fuel injection valve for supplying fuel to the internal combustion engine, and a bypass passage provided so as to bypass the intake pipe in the vicinity of the injection hole portion of the fuel injection valve from the throttle valve downstream of the intake pipe. An air-assisted fuel injection device is provided.

According to the present invention, the air guided as the assist air is a part of the intake air flowing in the portion downstream of the throttle valve. Therefore, this air is completely free from the dirt contained in the exhaust gas. Moreover, even if the assist air flows in, the total flow rate of the intake air becomes the flow rate determined by the opening degree of the throttle valve. In particular, when the throttle is closed, intake air does not continue to flow and the idle speed does not increase.

When the internal combustion engine is in a low temperature state and the injected fuel is difficult to vaporize, the atomization of the fuel is further promoted by increasing the flow rate of the assist air. Therefore,
As described in claim 2 of the present invention, when the internal combustion engine is in a low temperature state, the ratio of the assist air may be increased to further promote atomization of the fuel.

In the device according to the second aspect of the present invention, since the ratio of the assist air introduced from the downstream side of the throttle is simply increased, the total flow rate of intake air does not change. Therefore,
It is possible to promote atomization of the fuel at low temperature of the internal combustion engine without increasing the idle speed.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. First, the first embodiment will be described. The fuel injection device of the first embodiment is incorporated as a part of the intake device 1, as shown in FIG. The intake system 1 is provided in an engine equipped with a known speed density type air-fuel ratio control system that estimates the intake amount by the intake pipe pressure.

The intake device 1 is provided with a surge tank 3, an intake manifold 5 surrounding the surge tank 3 in a spiral shape, and a pipe 7 incorporated in the center of the surge tank 3 and the intake manifold 5. . Where piping 7
Forms an intake path that is located upstream of the surge tank 3, and has an air cleaner 9 inside.

In the surge tank 3, an injector 11 is installed.
A delivery pipe 13 for guiding the fuel to be supplied to the injector 11, a pressure regulator 15 for adjusting the fuel pressure in the delivery pipe 13 in accordance with the pressure in the surge tank 3, and an excessively supplied fuel flowing out from the pressure regulator 15. A return pipe 17 that guides fuel to a fuel tank (not shown) is fixed by a stay or the like (not shown).

Further, the surge tank 3 is provided with a pressure sensor 19 for detecting the internal pressure and an intake air temperature sensor 21 for detecting the temperature of the air in the surge tank 3. As shown in the enlarged cross-section of FIG. 2, the injector 11 has its tip portion 11 a attached to the mounting cylinder 25 in the surge tank 3.
Is fixed so that fuel can be injected into the intake manifold 5. An insulator 26 is interposed between the injector 11 and the mounting cylinder 25.
An air assist passage 27 that communicates from the surge tank 3 to the inside of the attachment cylinder 25 is formed in the attachment cylinder 25 as a bypass passage for intake air. The air assist passage 27 is
It is provided at least at two or more places with respect to one mounting cylinder 25, and its diameter is set to about 1 to 2 mm.

The intake device 1 is assembled by sandwiching the pipe 7 between the upper body 41 and the lower body 43, as shown in an exploded view in FIG. At that time, the upper body 4
The contact surfaces of the lower body 43, the lower body 43, and the pipe 7 at the time of assembly are sealed with an adhesive or an elastic body such as rubber to prevent air from leaking to an adjacent intake path or the outside. .

A tank 49 is formed in the lower body 43 between the side walls 45 and 47 at both longitudinal ends thereof. This tank 49 is the surge tank 3 in the assembled state (see FIG. 1).
become. Further, in the upper body 41, four grooves 57 are formed by partitioning the side walls 51 and 53 at both ends in the longitudinal direction with three partition walls 55. The groove 57 communicates with the tank 49 in the assembled state. Then, four tubes 59 are formed in the lower body 43 so as to surround the tank 49 and wrap around from the side surface to the lower side. In the assembled state,
The groove 57 and the pipe 59 communicate with each other to form the intake manifold 5 (see FIG. 1).

Further, the side walls 51, 53 of the upper body 41 and the partition wall 55 have a recess 61, the side wall 45 of the lower body 43,
Recesses 63 are formed in each 47. In the assembled state, the pipe 7 fits between the recess 61 and the recess 63. At this time, the flanges 67 formed on both ends 7a, 7b of the pipe 7 are caught by sandwiching the side walls 45, 47, 51, 53 from the front and back. As a result, the pipe 7 is fixed so as not to shift in the axial direction. The outer wall surface of the pipe 7 forms a part of the inner wall surfaces of the surge tank 3 and the intake manifold 5 in the assembled state (see FIG. 1).

In addition, one end of a U-shaped intake duct 71 is connected to the end 7b of the pipe 7. This intake duct 71
A throttle body 73 is provided at the other end of the.
The throttle body 73 is screwed and fixed so as to communicate with an intake hole 75 formed in the side wall 47 of the lower body 43.

Furthermore, the lower body 43 is provided with a fuel supply pipe 81 and a fuel return pipe 83. The fuel supply pipe 81 has the delivery pipe 13 in the surge tank 3 and the fuel return pipe 8
Return pipes 17 in the surge tank 3 are connected to the respective fuel tanks 3 via rubber tubes (not shown). Further, the lower body 43 has a centralized electrical connector 87.
Is also provided. The injector 11, the pressure sensor 19, the intake air temperature sensor 21 and the like are connected to this via a wire harness (not shown). The centralized electrical connector 87 is further connected to a vehicle-side harness (not shown).
Connected to.

In addition, inside the above-mentioned pipe 7,
As shown in FIG. 4, a cylindrical pipe 91 having numerous holes is provided, a cylindrical filter element 93 is fitted into the pipe 91, and the filter element 93 is shown by a stay 95 in FIG. 5B. As described above, the stay 95 is fixed to the pipe 7 with the bolt 97 to form the air cleaner 9. The air flowing in from the end 7a of the pipe 7 flows as shown by the arrow in FIG. 5A, and the air filtered by the filter element 93 is
Flows out from the end 7b.

Next, the flow of intake air in the intake device 1 incorporating the fuel injection device of this embodiment will be described.
The flow rate of the air flowing into the surge tank 3 is adjusted by the valve of the throttle body 73, and most of the air flows from above the surge tank 3 to the intake manifold 5. At this time, a part of the air flows into the air assist passage 27. The air that has passed through the air assist passage 27 (assist air) hits the side surface of the tip portion 11a of the injector 11 and flows along the side surface in the fuel injection direction,
The flow velocity near the tip 11a of the injector 11 increases.
When the injector 11 injects fuel into such an air flow, the injected fuel droplets collide with the assist air and are torn off. The fuel that has been torn off and atomized passes through the intake manifold 5 together with air and is sucked into the engine.

As described above, in the air assist type fuel injection system of this embodiment, the air in the surge tank 3 is
The assist air flows to the vicinity of the tip 11a of the injector 11. By introducing the assist air in this way, the injected fuel is atomized and the fuel adhering to the wall surface of the intake manifold 5 is reduced. As a result, the fuel becomes easy to completely burn, and HC emission can be reduced.

Further, since the exhaust gas is not introduced as the assist air, the injector 11 and the air assist passage 27 are not contaminated, and the injector 11 and the like are not deteriorated by the heat of the high-temperature exhaust gas. Furthermore, since the assist air is guided from the surge tank 3, the amount of air according to the throttle opening is always supplied to the engine. As a result, like when the assist air is taken from the throttle upstream,
There is no problem such as an increase in engine speed during idle operation.

In addition, in the embodiment, since the intake device 1 is a spiral type, the air assist passage 27 from the surge tank 3 can be formed only by making a hole in the mounting cylinder 25.
Therefore, no long pipes are required to guide the intake air, and an air-assist type fuel injection device can be configured very easily at low cost. In addition, the pressure loss is reduced as compared with the case where long pipes are used, and the assist air flows smoothly.

The air assist passage 27 is shown in FIG.
As shown in (a), the fuel injected from the injector 11 is slanted with respect to the axial direction of the injector 11, and at the same time, is twisted and blown into the mounting cylinder 25 as shown in (b) of the drawing. A swirl may be applied to the structure.

Next, the second embodiment will be described. Second
As shown in FIG. 7, the fuel injection device of the embodiment is also incorporated in a part of the spiral intake device 1 similar to that of the first embodiment. The difference from the first embodiment is that an intake control valve 31 is provided. The intake control valve 31 is rotatably provided around the shaft 33. The shaft 33 is
Driven by a diaphragm type valve (not shown), a DC motor or the like, the position of the intake control valve 31 is switched to either of the states shown in FIG. 7 (a) or FIG. 7 (b). Further, the intake control valve 31 is provided with a vent hole 35.
The inside diameter of the vent hole 35 is made slightly larger than that of the tip portion 11a of the injector 11. When the intake control valve 31 is brought to the position shown in FIG. 7 (b), the tip portion 11a of the injector 11 is inserted into the vent hole 35. Get in. Even in the state of FIG. 7B, assist air flows near the tip 11a of the injector 11 through the ventilation hole 35.

Next, switching control of the rotational position of the intake control valve 31 will be described with reference to FIG. Switching of the rotational position of the intake control valve 31 is controlled by an electronic control unit (ECU) (not shown), and is executed according to the cooling water temperature that is correlated with the intake pipe wall surface temperature.

First, the cooling water temperature is detected by the water temperature sensor (S10). For example, when the water temperature is low (for example, 70 ° C. or lower) as when the engine is cold started (S20: YES), the intake control valve 31 is switched to the position shown in FIG. The proportion of intake air flowing as air increases (S30). That is, the flow rate of air flowing from the surge tank 3 along the intake manifold 5 decreases, and the flow rate of air flowing from the surge tank 3 into the intake manifold 5 through the periphery of the injector 11 increases. As a result, atomization of the injected fuel is further promoted, and the amount of fuel adhering to the wall surface of the intake pipe is reduced even if the temperature of the intake pipe is low. Therefore, the fuel becomes easy to burn completely and the HC
Emissions can be reduced.

On the other hand, when the water temperature is high (for example, higher than 70 ° C.) as in the steady operation (S20: N
O), the intake control valve 31 is switched to the position shown in FIG. 7B, and the ratio of intake air flowing along the intake manifold 5 increases (S40). That is, the flow rate of the air flowing from the surge tank 3 along the intake manifold 5 increases and the assist air passing around the injector 11 decreases.
As a result, make full use of the length of the intake manifold 5,
The torque can be improved by the inertia supercharging.

As described above, in this embodiment, the ratio of the air flowing along the intake manifold 5 to the air flowing into the intake manifold 5 as assist air that passes through the vicinity of the injector 11 is selectively set according to the cooling water temperature. Since it can be changed to, it is possible to achieve both reduction of HC emission when the engine is cold and improvement of torque during continuous operation.

In particular, when the engine immediately shifts to high speed operation without warming up when the engine is cold,
A large amount of fuel is injected into the low temperature intake pipe, but since the intake control valve 31 is opened and a large amount of assist air is flown, atomization of the fuel is further promoted and the fuel adhering to the wall surface of the intake pipe is further promoted. The amount is also reduced. As a result, the amount of fuel sucked into the combustion chamber in a liquid state without being vaporized is reduced, complete combustion is facilitated, and HC emission is reduced. Moreover, even though the assist air is greatly increased in this way, the total flow rate of intake air does not change, so there is no sudden increase in the engine speed and a feeling of acceleration according to the accelerator operation is obtained. Does not give any sense of incongruity.

Further, in this embodiment as well, as in the first embodiment, since the assist air is guided from the surge tank 3 to the vicinity of the injector 11 without passing through a long pipe, the pressure loss is small and the assist air is smooth. Flowing. Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modes can be adopted without departing from the scope of the present invention.

For example, the surge tank 3 and the intake manifold 5 are not limited to the spiral type shown in the embodiment.

[0033]

As described above, according to the fuel injection device of the present invention, by injecting the assist air to the vicinity of the injector, the injected fuel is atomized and the fuel adhering to the wall surface of the intake manifold is reduced. . As a result, the fuel is completely burned and the reduction of HC emission can be achieved.

At this time, since the exhaust gas is not introduced as the assist air, the injector and the air assist passage are not contaminated by carbon adhering, and the injector and the like are deteriorated by the heat of the high temperature exhaust gas. Don't worry. Further, since the assist air is guided from the surge tank located downstream of the throttle, the amount of air corresponding to the throttle opening is always supplied to the engine. As a result, there is no problem such as an increase in engine speed during idle operation, which occurs when assist air is taken from the upstream of the throttle.

Particularly, in the fuel injection device according to the second aspect, the fuel can be atomized effectively even when the engine is cold, and H
C emission can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fuel injection device as a first embodiment.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the tip of the injector.

FIG. 3 is an exploded view of the intake device.

FIG. 4 is a cross-sectional view showing an exploded air cleaner.

FIG. 5 shows an air cleaner, (a) is a cross-sectional view showing the internal structure and air flow, and (b) is a side view seen from the axial direction.

FIG. 6 is an enlarged cross-sectional view of the vicinity of a tip portion of an injector as a modified example.

FIG. 7 is a cross-sectional view of a fuel injection device as a second embodiment, where (a) and (b) show the difference in air flow depending on the position of the intake control valve.

FIG. 8 is a flowchart showing switching control of the intake control valve.

[Explanation of symbols]

1 ... Intake device, 3 ... Surge tank, 5 ... Intake manifold, 7 ... Piping, 9 ... Air cleaner,
11 ... Injector, 13 ... Delivery pipe,
15 ... Pressure regulator, 17 ... Return pipe, 19 ... Pressure sensor, 21 ... Intake temperature sensor, 25 ... Mounting cylinder, 26 ... Insulator,
27 ... Air assist passage, 31 ... Intake control valve,
33 ... Shaft, 35 ... Vent hole, 41 ... Upper body, 43 ... Lower body, 45, 47, 51,
53 ... Side wall, 49 ... Tank, 55 ... Partition wall, 57
... Grooves, 59 ... Tubes, 61, 63 ... Recesses, 67
... Flange, 71 ... Intake duct, 73 ... Throttle body, 75 ... Intake hole, 81 ... Fuel supply pipe, 83 ... Fuel return pipe, 87 ...
Centralized electrical connector, 91 ... Pipe, 93 ... Filter element, 95 ... Stay, 97 ... Bolt.

Claims (2)

[Claims] 1. An intake pipe for supplying air to an internal combustion engine, a throttle valve provided in the intake pipe for adjusting the amount of air supplied to the internal combustion engine, and a fuel injection for supplying fuel to the internal combustion engine. An air-assisted fuel injection device, comprising: a valve; and a bypass passage that is provided downstream of the throttle valve of the intake pipe and near the injection hole of the fuel injection valve so as to bypass the intake pipe. . 2. An intake control valve for adjusting the ratio of the amount of air supplied to the vicinity of the injection hole of the fuel injection valve through the bypass passage and the amount of air supplied through the intake pipe, Warm-up state detecting means for detecting a warm-up state of the internal combustion engine, and when the warm-up state detecting means detects that the internal combustion engine is in a low temperature state, the amount of air supplied through the bypass passage The air-assisted fuel injection device according to claim 1, further comprising: intake control means for controlling the intake control valve so that the ratio becomes large.