JP2002332929A - Fuel injection system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electromagnetic force required for valve opening drive, and achieve compactness in a fuel injection system for directly injecting mixed gas of fuel and air into a combustion chamber. SOLUTION: An air chamber 15 to compose a mixed gas supply passage, and an actuation assisting chamber 14 are parted by a needle valve guide 13a of a needle valve 13. To the actuation assisting chamber 14, liquid fuel is supplied through a check valve 24, and on the downstream side of the check valve 24, one end of a piston 25 which receives pressure in the combustion chamber at the other end is provided to face it. The actuation assisting chamber 14 is kept at a prescribed pressure or more by supply of liquid fuel, and it is pressurized as pressure in the combustion chamber 3 rises. Pressure in the actuation assisting chamber 14 corresponding to the pressure in the combustion chamber 3 acts in a valve opening direction of the needle valve 13. Demand for electromagnetic force generated by energization to an electromagnetic coil 29 is thus reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine, and more particularly to a two-fluid fuel injection device for injecting a mixture of fuel and air.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection device for a direct-injection spark ignition engine, as described in Japanese Patent Application Laid-Open No. 5-256230, fuel and air are mixed in advance, and a needle valve is lifted by electromagnetic force. Then, there is a configuration in which a mixture of the fuel and the air is injected.

[0003]

In the fuel injection device for injecting a mixture of fuel and air as described above, the injection volume flow rate is increased as compared with the device for injecting only fuel. It is necessary to increase the diameter of the seat portion and the stroke of the needle valve to increase the opening area of the injection hole portion of the injection nozzle.

Here, when the seat diameter is increased, the needle valve is more likely to receive the pressure in the combustion chamber, and when the injection timing is from the intake stroke to the latter half of the compression stroke, the needle valve opposes the pressure in the combustion chamber that acts in the valve closing direction. It is required to open the needle valve with a possible electromagnetic force, which requires a large magnetic material. However, if the weight of the movable part increases due to the use of a large magnetic material, it is necessary to increase the set load of the spring that biases the needle valve in the valve closing direction in order to maintain the responsiveness. There is a problem that a large electromagnetic force is required, the size of the magnetic material portion is increased, and the size of the fuel injection device is increased.

[0005] Furthermore, the weight of the movable part increases,
The collision energy when the needle valve is seated on the seat increases, which lowers the durability of the injection device, generates an impact sound, and further reduces the needle valve after closing. There is a problem that a lift (bouncing) occurs.
In particular, when the bouncing of the needle valve occurs, there is a problem that the exhaust performance is deteriorated due to the injection of the excess air-fuel mixture, and the deposit is deposited on the nozzle.

The present invention has been made in view of the above circumstances, and has a small electromagnetic force, that is, an electromagnetic two-fluid fuel injection that can set the injection timing to the second half of the compression stroke while being a light movable part. It is intended to provide a device.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection device for an engine for injecting a mixture of fuel and air by driving a needle valve held by a nozzle. The needle valve is driven by a combined force of an electromagnetic force acting on the needle valve and a force acting on the needle valve by the pressure in the operation auxiliary chamber formed by the needle valve and the nozzle, and the injection timing of the air-fuel mixture Is controlled by the generation timing of the electromagnetic force.

According to this configuration, the needle valve is not driven to be opened only by the electromagnetic force, but the pressure of the operation auxiliary chamber is made to act auxiliary, and the needle valve is actuated by the combined force of the electromagnetic force and the pressure of the operation auxiliary chamber. The valve is driven to open, and the opening and closing of the needle valve is switched depending on whether or not an electromagnetic force is generated. According to the second aspect of the present invention, an air chamber formed by the needle valve and the nozzle and constituting a part of the supply path of the air-fuel mixture is provided, and the air chamber and the operation auxiliary chamber are provided in the needle valve. The needle valve guide is configured to be separated in the axial direction of the needle valve.

According to this configuration, the needle valve guide provided for slidingly moving the needle valve to the nozzle and guiding the movement is provided.
It also functions as a shut-off unit that separates an air chamber that forms a supply path of the air-fuel mixture and an operation auxiliary chamber that auxiliaryly drives the needle valve. According to the third aspect of the present invention, the pressure of the liquid in the auxiliary operation chamber is changed, and the pressure of the liquid in the auxiliary operation chamber is set higher than the pressure in the air chamber.

According to this structure, since the pressure of the liquid in the auxiliary operation chamber is higher than the pressure of the air chamber, the flow of the fluid in the gap of the needle valve guide section separating the auxiliary operation chamber and the air chamber is increased. The flow is limited to the flow from the auxiliary chamber to the air chamber. According to a fourth aspect of the present invention, the pressure of the liquid in the auxiliary operation chamber is changed, and a seal member is interposed in the needle valve guide.

With this configuration, leakage of air from the air chamber side to the operation auxiliary chamber is blocked by the seal member. In the invention described in claim 5, the fuel injection device is configured to directly inject the air-fuel mixture into the combustion chamber of the engine, and the pressure in the operation auxiliary chamber is changed according to the pressure in the combustion chamber. .

According to this configuration, the pressure in the operation auxiliary chamber that generates a force for driving the needle valve in the valve opening direction changes according to the pressure in the combustion chamber that is the pressure received by the needle valve in the valve closing direction. Become. In the invention according to claim 6, the fuel supply passage for supplying liquid fuel to the operation auxiliary chamber, and the liquid fuel is provided when the pressure in the operation auxiliary chamber is lower than a predetermined pressure. A check valve to be supplied to the auxiliary chamber and a piston for receiving the pressure in the combustion chamber and pressurizing the liquid in the operation auxiliary chamber are provided.

According to this configuration, when the pressure in the operation auxiliary chamber decreases, the check valve opens to supply liquid fuel to the operation auxiliary chamber, the pressure in the operation auxiliary chamber is maintained at a certain pressure or higher, and the pressure in the combustion chamber is reduced. When it rises, the working auxiliary chamber is pressurized by the piston. In the invention according to claim 7, the piston is configured to increase the pressure in the operation auxiliary chamber to a pressure higher than the pressure in the combustion chamber.

According to this structure, the pressure of the liquid fuel in the operation auxiliary chamber is increased by the piston to a value higher than the pressure in the combustion chamber, and the needle valve is driven by the pressure of the operation auxiliary chamber and the electromagnetic force. The invention according to claim 8 is provided with a communication passage for communicating the operation auxiliary chamber with the combustion chamber of the engine, and closing the communication passage when the pressure in the combustion chamber becomes a predetermined value or more. did.

According to this configuration, since the auxiliary working chamber and the combustion chamber are communicated with each other through the communication passage, the pressure in the auxiliary operating chamber is reduced.
Although the pressure becomes equal to the pressure in the combustion chamber, when the pressure in the combustion chamber becomes equal to or higher than a predetermined value, the intrusion of the combustion gas into the operation auxiliary chamber is shut off by closing the communication passage particularly in the combustion stroke. According to the ninth aspect of the present invention, there is provided a piston that receives the pressure in the combustion chamber, performs a stroke, closes the communication passage in the middle of the stroke, and increases the pressure in the operation auxiliary chamber to a pressure higher than the pressure in the combustion chamber. The configuration was adopted.

According to this configuration, when the pressure in the combustion chamber increases, the communication path is closed by the stroke of the piston, and the working auxiliary chamber becomes a closed space. Is increased above the pressure in the combustion chamber. In the invention according to claim 10, the stroke of the piston is restricted by a stopper.

According to this structure, the stroke of the piston for pressurizing the operation auxiliary chamber is regulated by the stopper,
Stroke exceeding the stopper position, in other words, pressurization exceeding the pressure at the stopper position is prohibited.

[0018]

According to the first aspect of the present invention, since the needle valve is driven by using the pressure of the operation auxiliary chamber formed by the needle valve and the nozzle in an auxiliary manner, the needle valve is opened with a small electromagnetic force. As a result, the weight of the movable portion can be reduced, so that the magnetic material portion can be reduced in size to reduce the size of the fuel injection device, and the impact energy at the time of sitting is reduced, thereby improving durability. In addition to this, there is an effect that the re-lift at the time of closing the valve is prevented and the exhaust performance can be improved.

According to the second aspect of the present invention, the air chamber and the operation auxiliary chamber are separated by the guide portion of the needle valve.
By providing the operation auxiliary chamber, it is possible to prevent an increase in the number of parts and an increase in precision processing sites. According to the third and fourth aspects of the invention, it is possible to prevent the air in the air chamber from entering the auxiliary operation chamber, and thus to prevent the cavitation of the liquid in the auxiliary operation chamber.

According to the fifth aspect of the invention, the pressure in the combustion chamber received by the needle valve can be offset, and even if the injection timing is set in the latter half of the compression stroke, the electromagnetic force required for opening the valve is reduced. There is an effect that can be. According to the invention of claim 6, there is an effect that the pressure of the liquid in the operation auxiliary chamber is increased in accordance with the rise in the pressure in the combustion chamber, and the pressure in the combustion chamber received by the needle valve can be offset.

According to the seventh aspect of the present invention, there is an effect that a biasing force by a spring or the like applied to the needle valve in the valve closing direction and a pressure against the pressure in the combustion chamber can be generated in the operation auxiliary chamber. . According to the invention as set forth in claim 8, the pressure in the operation auxiliary chamber can be made to correspond to the combustion chamber with a simple configuration, and the pressure in the combustion chamber received by the needle valve can be offset, and the combustion gas enters the operation auxiliary chamber. This has the effect of preventing the inside of the injection device from being soiled.

According to the ninth aspect of the invention, the urging force of a spring or the like applied to the needle valve in the valve closing direction and the pressure against the pressure in the combustion chamber can be generated in the operation auxiliary chamber, and the combustion gas can be generated. Can be prevented from entering the operation auxiliary chamber with a simple configuration. Claim 1
According to the invention described in Item 0, by regulating the stroke of the piston that pressurizes the operation auxiliary chamber, it is possible to reliably prevent the pressure in the operation auxiliary chamber from becoming too high.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a fuel injection device according to the first embodiment. The fuel injection device 1 shown in FIG. 1 is a device for directly injecting a mixture of fuel and air into a combustion chamber 3 of an engine 2.

The main body 11 of the fuel injection device 1 is provided with a hollow nozzle 12 having an injection hole 12a at the tip, and a needle valve 13 is held in the nozzle 12. Needle valve 1
A needle valve guide 13a having an enlarged diameter is provided at an intermediate portion of the needle valve 3, and the needle valve guide 13a is fitted into the hollow portion of the nozzle 12, so that the needle valve 13 can be moved in the axial direction with respect to the nozzle 12. You will be guided.

The operation auxiliary chamber 1 is formed vertically above and below the needle valve guide 13a by the outer periphery of the needle valve 13 and the inner periphery of the nozzle 12.
4. Each of the air chambers 15 is formed in an annular shape. An air-fuel mixture injected into the engine 2 is supplied to an air chamber 15 formed at a more distal end side than the needle valve guide 13 a through an air-fuel mixture supply passage 16 provided in the main body 11.

A liquid fuel injection valve 17 fixed to the main body 11 faces the middle of the mixture supply passage 16, while an end of the mixture supply passage 16 extending to the outside of the body 11 is provided at the end of the mixture supply passage 16. An air pump 18 is provided, and a fuel-air mixture is formed by injecting fuel from the liquid fuel injection valve 17 into compressed air pressurized by the air pump 18. The liquid fuel injection valve 17 is sucked from a fuel tank 19 by a fuel pump 20 and is supplied to the pressure regulator 2.
The liquid fuel adjusted to a predetermined pressure in 1 is supplied through the first fuel supply passage 22.

The pressure regulator 21 adjusts the fuel pressure to a predetermined pressure by returning surplus fuel to the fuel tank 19 via the relief passage 21a. On the other hand, a liquid fuel adjusted to a predetermined pressure by the pressure regulator 21 is supplied to the operation auxiliary chamber 14 formed on the base end side of the needle valve guide 13 a through a second fuel supply passage 23.

A check valve 24 is interposed in the second fuel supply passage 23. The check valve 24
Means that the pressure of the liquid fuel on the downstream side of the check valve 24 is lower than the pressure of the liquid fuel on the upstream side (the pressure regulator 21
The valve opens when it becomes lower than the set pressure
The valve allows the fuel to be introduced into the auxiliary operation chamber 14 and shuts off the second fuel supply passage 23 in other cases.

It should be noted that the pressure in the operation auxiliary chamber 14 is changed to the air chamber 15
, So that the air in the air chamber 15 is displaced through the fitting gap of the needle valve guide 13a that separates the auxiliary operation chamber 14 and the air chamber 15 from each other. It is designed to prevent intrusion. Here, when the pressure setting cannot be performed, or when the operation auxiliary chamber 14
When it is desired to prevent the fuel from leaking from the air chamber 15 into the air chamber 15, as shown in FIG.
The O-ring 13b (seal member) may be interposed.

One end of the second fuel supply passage 23 downstream of the check valve 24 faces the other end of the piston 25 receiving the pressure in the combustion chamber 3. The piston 25 is urged toward the combustion chamber 3 by a spring 26 while receiving a pressure in the combustion chamber 3.
5a and a small diameter portion 25b facing the second fuel supply passage 23.

Accordingly, when the pressure in the combustion chamber 3 increases, the piston 25 strokes toward the second fuel supply passage 23 as shown in FIG.
4 is pressurized, and the operation auxiliary chamber 1
The combustion chamber 3 depends on the pressure receiving area difference between the combustion chamber 3 and the combustion chamber 3 side.
The internal pressure is increased and transmitted to the fuel in the operation auxiliary chamber 14.

Here, the stroke of the piston 25 toward the second fuel supply passage 23 is restricted by the stopper 25c, and the fuel pressure in the operation auxiliary chamber 14 is increased by the piston 25 to a predetermined value or more. I do not have it. The needle valve 13 is urged by a coil spring 27 in a valve closing direction (upward in FIG. 1), and an armature 28 (magnetic material) is integrally provided at a base end thereof, and is fixed to the main body 11. By supplying a current to the coil 29, an electromagnetic attraction force for driving the needle valve 13 in the valve opening direction (downward in FIG. 1) is generated.

The needle valve 1 penetrating the base end side of the nozzle 12
The fuel leaking from the sliding contact portion 3 into the space in which the coil spring 27 is provided is returned to the fuel tank 19 via the drain passage 30. In the fuel injection device 1 having the above-described configuration, the needle valve 13 is lifted and opened by passing a current through the electromagnetic coil 29 at the injection timing, and together with the electromagnetic force acting in the valve opening direction by the electromagnetic coil 29, Since the fuel pressure in the operation auxiliary chamber 14 acts on the needle valve 13 in the valve opening direction, the electromagnetic force required for valve opening drive can be reduced.

Further, since the fuel pressure in the operation auxiliary chamber 14 increases in accordance with the increase in the pressure in the combustion chamber 3, even if the latter half of the compression stroke is set as the injection timing, the electromagnetic force required for the valve opening drive is set. Does not increase sharply with respect to the intake stroke injection. Therefore, even when the injection timing is set from the intake stroke to the latter half of the compression stroke, the electromagnetic force required for the valve opening drive can be suppressed small, whereby the armature 28 (magnetic material) can be reduced, and the fuel injection device 1 can be miniaturized.

FIG. 4 shows the correlation between the pressure change in the combustion chamber and the force acting on the needle valve. As shown in FIG. 4, the needle valve 13 has a force in the valve closing direction by the coil spring 27, a force in the valve closing direction by the working gas pressure in the combustion chamber 3, and a gas mixture pressure in the air chamber 15. The force in the valve opening direction and the force in the valve opening direction due to the fuel pressure in the operation auxiliary chamber 14 are always applied.

Here, the force in the valve opening direction due to the fuel pressure in the operation auxiliary chamber 14 can be increased and changed in accordance with the increase in the force in the valve closing direction due to the working gas pressure in the combustion chamber 3. By setting the diameter of the piston 25, the pressure receiving area in the needle valve guide 13a, and the like, the force in the valve closing direction and the force in the valve opening direction can be substantially balanced irrespective of the pressure change in the combustion chamber 3, and The electromagnetic quantity required for driving the valve can be suppressed to a small value regardless of the pressure change (injection timing) in the combustion chamber.

On the other hand, when the force in the valve opening direction by the operation auxiliary chamber 14 is not applied, the electromagnetic force is increased by the absence of the force in the valve opening direction by the operation auxiliary chamber 14, as shown in FIG. In order to enable the injection timing to be set in the latter half of the compression stroke, a large electromagnetic force is required, and the armature 28 (magnetic material) is increased in size and, consequently, the fuel injection device 1 is increased in size. Will be invited.

FIG. 6 shows a fuel injection device according to the second embodiment. The fuel injection device shown in FIG.
Only the configuration of the pressure control system of the operation auxiliary chamber 14 is different from the first embodiment shown in FIG. In the fuel injection device shown in FIG. 6, the fluid guided to the operation auxiliary chamber 14 is the working gas in the combustion chamber 3.

Specifically, the inside of the combustion chamber 3 and the operation auxiliary chamber 14
Is provided, and a piston 32 for increasing the pressure in the operation auxiliary chamber 14 higher than the pressure in the combustion chamber 3 is provided. The piston 32 includes a large-diameter portion 32a that receives the pressure in the combustion chamber 3 and a small-diameter portion 32b that faces the operation auxiliary chamber 14, and at a reference position on the combustion chamber 3 side urged by a spring 33, Passage 3
1 is opened, the pressure in the combustion chamber 3 and the operation auxiliary chamber 1
4 is equal to the pressure inside.

Here, when the pressure in the combustion chamber 3 rises and the force acting in the direction in which the piston 32 strokes due to the difference in pressure receiving area exceeds the urging force of the spring 33, the piston 32 strokes. , Small diameter portion 32b
(See FIG. 7). After the communication passage 31 is closed by the piston 32, when the pressure in the combustion chamber 3 becomes higher, the piston 32 further strokes, and the pressure in the operation auxiliary chamber 14 increases to be higher than the pressure in the combustion chamber 3.

Incidentally, also in the second embodiment, the stopper 32c regulates the stroke of the piston 32, so that the pressure in the operation assist 14 is not increased more than a predetermined value. Also in the second embodiment having such a configuration, the pressure in the operation auxiliary chamber 14 acts in the valve opening direction of the needle valve 13, and
Since the pressure in the operation auxiliary chamber 14 increases in accordance with the increase in the pressure of the combustion chamber 3, even if the injection timing is set in the latter half of the compression stroke, the electromagnetic force required for the valve opening drive is reduced. Thus, the armature 28 (magnetic material) can be made smaller, and the fuel injection device 1 can be made smaller.

Further, by closing the communication passage 31 when the pressure in the combustion chamber 3 becomes high, the inflow of the combustion gas into the operation auxiliary chamber 14 can be prevented. It is possible to prevent carbon or the like from flowing into the sliding portion between the needle valve 13 and the nozzle 12 to prevent the movement of the needle valve 13 from being obstructed.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a fuel injection device according to a first embodiment.

FIG. 2 is a partially enlarged view showing a configuration in which an O-ring is added to a needle valve guide in the first embodiment.

FIG. 3 is a partially enlarged view showing a stroke state of a piston in the first embodiment.

FIG. 4 is a graph showing a correlation between a load applied to a needle valve and a pressure in a combustion chamber according to the first embodiment.

FIG. 5 is a graph showing a correlation between a load applied to a needle valve and a pressure in a combustion chamber when a force in a valve closing direction is not generated by an operation auxiliary chamber.

FIG. 6 is a system configuration diagram showing a fuel injection device according to a second embodiment.

FIG. 7 is a partially enlarged view showing a stroke state of a piston in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection device 2 ... Engine 12 ... Nozzle 13 ... Needle valve 13a ... Needle valve guide 14 ... Operation auxiliary chamber 15 ... Air chamber 16 ... Mixture supply passage 17 ... Liquid fuel injection valve 18 ... Air pump 19 ... Fuel tank 20 ... Fuel pump 21 ... Pressure regulator 24 ... Check valve 25 ... Piton 27 ... Coil spring 28 ... Armature 29 ... Electromagnetic coil 31 ... Communication passage 32 ... Piston

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 61/14 310 F02M 61/14 310D 61/16 61/16 K 61/20 61/20 P 67/02 67/02 67/12 67/12 (72) Inventor Kenmei Kubo 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside (72) Inventor Akihiro Iiyama 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. F term (reference) 3G066 AA02 AB02 AD12 BA63 BA67 CC06T CC06U CC08T CC14 CC40 CC46 CC51 CC64Z CD10 CE13 CE15 CE22

Claims (10)

[Claims] 1. A fuel injection device for an engine for injecting a mixture of fuel and air by driving a needle valve held by a nozzle, comprising: an electromagnetic force acting on the needle valve; The needle valve is driven by a combined force with the force acting on the needle valve by the pressure in the operation auxiliary chamber, and the injection timing of the air-fuel mixture is controlled by the generation timing of the electromagnetic force. Engine fuel injection system. 2. A needle valve guide comprising an air chamber formed by the needle valve and the nozzle and constituting a part of a supply passage for the air-fuel mixture, wherein the air chamber and the operation auxiliary chamber are provided in the needle valve. The fuel injection device for an engine according to claim 1, wherein the needle valve is separated in an axial direction of the needle valve. 3. The structure according to claim 2, wherein the pressure of the liquid in the auxiliary operation chamber is changed, and the pressure of the liquid in the auxiliary operation chamber is set higher than the pressure in the air chamber. Engine fuel injection device. 4. The fuel injection device for an engine according to claim 2, wherein the pressure of the liquid in the auxiliary operation chamber is changed, and a seal member is interposed in the needle valve guide. 5. The fuel injection device according to claim 1, wherein the air-fuel mixture is directly injected into a combustion chamber of the engine, and the pressure in the operation auxiliary chamber is changed according to the pressure in the combustion chamber. Item 5. An engine fuel injection device according to any one of Items 1 to 4. 6. A fuel supply passage for supplying a liquid fuel to the operation auxiliary chamber, and a liquid fuel interposed in the fuel supply passage, the liquid fuel being supplied to the operation auxiliary chamber when a pressure in the operation auxiliary chamber is lower than a predetermined pressure. 6. The fuel injection device for an engine according to claim 5, further comprising a check valve for supplying, and a piston for receiving a pressure in the combustion chamber and pressurizing the liquid in the auxiliary operation chamber. 7. The fuel injection device for an engine according to claim 6, wherein the piston increases the pressure in the operation auxiliary chamber to a pressure higher than the pressure in the combustion chamber. 8. A fuel cell system, comprising: a communication passage for communicating the auxiliary operation chamber with a combustion chamber of an engine; and closing the communication passage when a pressure in the combustion chamber becomes equal to or higher than a predetermined value. The fuel injection device for an engine according to claim 5. 9. A piston that receives a pressure in the combustion chamber, performs a stroke, closes the communication passage in the middle of the stroke, and increases a pressure in the operation auxiliary chamber to a pressure higher than a pressure in the combustion chamber. The fuel injection device for an engine according to claim 8, wherein: 10. The fuel injection device for an engine according to claim 6, wherein a stroke of the piston is regulated by a stopper.