JP2002276461A - Fuel injection mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection mechanism capable of stably controlling opening/closing of an injection hole even at low injection pressure, and also capable of downsizing. SOLUTION: In a direct injection type fuel injection mechanism 26 for directly injecting fuel pressurized to a prescribed pressure by a fuel injection pump 5 to a combustion chamber 16 of an engine, a main body drum part 23 of a fuel injection device 7 provided with a needle valve 18 for opening/closing the injection hole 17, a spring 19 for energizing the needle valve 18 in a close direction of the injection hole 17 and an electromagnetic coil 22 for moving a mover 21 integrated with the needle valve 18 in an open direction of the injection hole 17 is stored within a cylinder head 24, and a water jacket 25 for cooling the fuel injection device 7 is formed on the cylinder head 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type fuel injection mechanism for directly injecting fuel, which has been raised to a predetermined pressure by a fuel injection pump, into a combustion chamber of an engine.

[0002]

2. Description of the Related Art A fuel injection device (injector) supplies fuel pressurized to a required supply pressure by a fuel injection pump (supply pump) directly driven by an engine to a combustion chamber of the engine. . The fuel injection device opens and closes a fuel passage with an electromagnetic valve or the like according to an electric signal, and injects fuel sent from a fuel injection pump into a combustion chamber.

[0003] Various fuel injection devices are employed. A conventional common rail fuel injection device has a structure in which an injection hole is opened and closed using a fuel pressure balance.

[0004] As shown in FIG.
An oil reservoir 54 is formed around a needle valve 53 that opens and closes the injection hole 52, and a pressure chamber 5 is provided above a control piston 55.
6 are formed. These oil sump 54 and pressure chamber 5
The operating pressure applied to the needle valve 53 by the fuel pressure in 6 is used.

More specifically, the fuel pressure in the pressure chamber 56 is released by opening an electromagnetic valve 57 provided in the upper part of the fuel injection device 51, thereby reducing the fuel pressure in the oil reservoir 54 on the needle valve 53 side. Is relatively higher, the needle valve 53 rises,
The injection hole 52 is opened, and fuel is injected.

[0006] In the lower space of the control piston 55, there is provided a fuel low pressure leak line for allowing the fuel leaking from the oil reservoir 54 around the needle valve 53 to the lower portion of the control piston 55 to escape. This is because the leaked fuel gradually increases the pressure in the lower part of the control piston 55, and if the fuel does not leak, the needle valve 53
Cannot move up and down.

In the drawing, reference numeral 61 denotes a fuel inlet of a fuel flow path;
62 indicates a small diameter orifice and 63 indicates a large diameter orifice.

[0008]

The above-described fuel injection device 5
First, when light oil is used as fuel, the injection pressure is 2
0 MPa to 160 MPa, and the difference between the operating force of the fuel pressure in the pressure chamber 56 applied to the control piston 55 and the operating force of the fuel pressure in the oil reservoir 54 applied to the needle valve 53 can be increased. High controllability.

When dimethyl ether is used as a fuel, it is not necessary to increase the injection pressure as much as light oil because the dimethyl ether is easily vaporized by its nature (15 MPa to 15 MPa).
25 MPa). Rather, considering the fuel efficiency of the entire engine, it is desirable that the injection pressure be low.

However, in the above-described fuel injection device 51, the injection hole 52 is opened and closed by utilizing the pressure difference between the fuel in the oil reservoir 54 and the fuel in the pressure chamber 56. However, there is a problem that the controllability of opening and closing the injection holes 52 is deteriorated.

When the injection pressure is low, the set force of the spring 58 for urging the needle valve 53 downward must be weakened. Therefore, bounce of the needle valve 53 is likely to occur, and the exhaust gas performance of the engine is reduced. There was also a problem that it became worse.

Further, since the fuel injection device 51 is provided with an electromagnetic valve 57 for adjusting the fuel pressure at the upper portion thereof, the overall height is increased, and as shown in FIG. It protrudes from the upper part of the cylinder head 59 of the engine, and requires a large installation space.

Accordingly, the present invention has been devised in order to solve the above-mentioned problem, and an object of the present invention is to provide a fuel injection mechanism capable of stably controlling the opening and closing of an injection hole even at a low injection pressure and achieving a reduction in size. Is to provide.

[0014]

In order to solve the above-mentioned problems,
The present invention provides a direct injection type fuel injection mechanism for directly injecting fuel, which has been raised to a predetermined pressure by a fuel injection pump, into a combustion chamber of an engine. A body body of a fuel injection device including a spring that biases in a closing direction and an electromagnetic coil that moves a movable element integrated with the needle valve in an opening direction of the injection hole is housed in a cylinder head. And a water jacket for cooling the fuel injection device is formed in the cylinder head.

According to the above construction, the movable element integrated with the needle valve is sucked by the electromagnetic force of the electromagnetic coil to open the injection hole, while the electromagnetic coil is cut off and the needle valve is pushed back by the urging force of the spring. Since the injection hole is closed, even if the fuel injection pressure is low, the opening and closing of the injection hole can be stably controlled without being affected by the low injection pressure. In addition, since the needle valve is moved directly by the electromagnetic coil, there is no need to provide a pressure chamber or the like, so that the overall height can be reduced as compared with the conventional fuel injection device, and downsizing is achieved. Is done.

Preferably, the fuel is a dimethyl ether fuel.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a preferred embodiment of a fuel injection device for a fuel injection mechanism according to the present invention, and FIG. 2 is a sectional view showing a preferred embodiment of the fuel injection mechanism according to the present invention. FIG. 3 is a schematic configuration diagram showing a fuel supply system of a dimethyl ether engine.

First, the configuration of a fuel supply system for a dimethyl ether engine including the fuel injection mechanism according to the present invention will be described.

As shown in FIG. 3, the fuel supply system 1
Is provided with a fuel tank 3 on the chassis side 2. A fuel pipe 6 for supplying dimethyl ether (DME) fuel to a fuel injection pump 5 provided on the engine side 4 is connected to the fuel tank 3.

The fuel injection pump 5 is connected to a common rail 8 to which a plurality of direct injection type fuel injection devices (injectors) 7 for directly injecting fuel into a combustion chamber (see FIG. 2) 16 of the engine are connected. I have.

A fuel return pipe 9 for returning excess fuel to the fuel tank 3 is connected to the fuel injection pump 5. A fuel return pipe 11 for returning excess fuel from the common rail 8 to the fuel tank 3 is connected in the middle of the fuel return pipe 9.

In the fuel tank 3, there is provided a pressure feed pump 12 for raising the pressure of dimethyl ether to a value higher than the saturated vapor pressure and sending it to the fuel injection pump 5.

In the figure, reference numeral 14 denotes a fuel cooler, and 15 denotes a fuel cut valve.

In the present invention, as shown in FIGS. 1 and 2, the fuel injection device 7 is provided with a needle valve 18 for opening and closing the injection hole 17 and a needle valve 18 for closing the injection hole 17 in the closing direction (lower side). ), And an electromagnetic coil 22 for moving the mover 21 integrated with the needle valve 18 in the opening direction (upward) of the injection hole 17, and the main body of the fuel injection device 7. A water jacket 25 for accommodating substantially the entire part 23 in the cylinder head 24 and cooling the body 23 of the fuel injection device 7 in the cylinder head 24.
The fuel injection mechanism 26 is characterized in that the fuel injection mechanism 26 is formed.

More specifically, the fuel injection device 7 is provided with a tip holder 27 having an injection hole 17 at a lower end at a lower portion thereof. The tip holder 27 is formed in a cylindrical shape, and accommodates the needle valve 18 therein. A rod 28 for connecting integrally with the mover 21 is provided above the needle valve 18. Tip holder 2
7, an oil reservoir 31 is formed above the needle valve 18 and has an inner peripheral surface formed with an enlarged diameter. A holding member 30 for holding the chip holder 27 is provided above the chip holder 27. A cavity 29 serving as a fuel passage is formed in the holding member 30. A fuel flow path 32 is formed in the tip holder 27 so as to connect from the cavity 29 of the holding member 30 to the oil reservoir 31.

The needle valve 18 is formed in a square cross section (for example, a quadrangle), and the fuel in the oil reservoir 31 is supplied to the tip holder 2.
The gas flows through the gap between the inner peripheral surface of the needle 7 and the needle valve 18 and is supplied to the injection hole 17 side. In order to open and close the injection hole 17, a seat portion 33 that is in close contact with the lower end surface of the needle valve 18 is provided above the injection hole 17. When the needle valve 18 is lowered, the needle valve 18 comes into close contact with the seat portion 33 to close and close the injection hole 17.

The mover 21 connected to the upper part of the rod 28
The lower part has a reduced diameter, and a cavity 34 is formed around the lower part. The mover 21 is connected to a fixed core portion 36 extending from a fuel receiving pipe 35 provided above the mover 21. The fixed core portion 36 is formed in a cylindrical shape, and forms a fuel supply channel 37 through which fuel flows.

Between the fuel supply channel 37 and the mover 21,
The spring 19 described above is provided. The spring 19 has a function of pressing the needle valve 18 against the seat 33 of the injection hole 17 when the injection hole 17 is closed.

Inside the mover 21, a fuel supply flow path 37 is provided.
A fuel flow path 38 is formed for flowing the fuel into the cavity 34. The hollow portion 34 is connected to the lower hollow portion 29 and supplies fuel to the oil reservoir 31.

An electromagnetic coil 22 is provided above the mover 21.
And a core 39 for generating the electromagnetic force. The core 39 is formed in a cylindrical shape, and is disposed so as to surround the fuel supply flow path 37.
2 are arranged. That is, these electromagnetic coils 22
The fuel supply channel 37 is located at the center of the core 39.

The above-described tip holder 27, cavity 29,
The outer peripheral portions of the armature 34, the mover 21, and the electromagnetic coil 22 are covered with a boss 41 that forms an outer shell of the fuel injection device 7.

The fuel receiving pipe 35 has a common rail 8
Nozzle 43 for connecting a fuel pipe extending from
Is attached.

As shown in FIG. 2, substantially the entire body 23 of the fuel injection device 7 having the above structure is accommodated in the cylinder head 24, and the injection hole 17 at the lower end thereof is provided.
However, it projects so as to face the combustion chamber 16 of the engine. The water jacket 25 in the cylinder head 24 is formed so as to surround the body 23 of the fuel injection device 7. The fuel injection mechanism 26 of the present invention is constituted by the fuel injection device 7 and the cylinder head 24 having the water jacket 25.

In FIG. 2, reference numeral 44 denotes a fixture for pressing the fuel injection device 7 from above and fixing it to the cylinder head 24.

Next, the operation of the fuel injection mechanism 26 will be described.

The dimethyl ether serving as fuel is boosted to a pressure suitable for being injected into the combustion chamber 16 of the engine by the fuel injection pump 5 and supplied to the fuel injection device 7 via the common rail 8. The dimethyl ether is
From the connection nozzle 43, the fuel supply channel 37, the fuel channel 38 of the mover 21, the cavity 34, the cavity 29, the tip holder 2
The fuel passes through the fuel passage 32 in the order of 7, and is stored in the oil sump 31 to be in a state of waiting for injection.

At this time, the needle valve 18 is urged downward by the spring 19, and is pressed against and closely adhered to the seat portion 33, so that the injection hole 17 is securely sealed and dimethyl ether leaks out. There is no.

At the time of fuel injection, an electric current flows through the electromagnetic coil 22, an electromagnetic force is generated in the core 39, the movable element 21 is pulled up, and the needle valve 18 is raised. As a result, the needle valve 18 is separated from the seat portion 33, the injection hole 17 is opened, and dimethyl ether passes around the needle valve 18 and is injected into the combustion chamber 16 from the injection hole 17.

As described above, since the movable element 21 is pulled up by the electromagnetic coil 22 to move the needle valve 18 directly, even if the fuel injection pressure is low, such as dimethyl ether, it is not affected by it. The opening and closing of the injection holes 17 can be controlled stably.

Further, since the set force of the spring 19 for urging the needle valve 18 downward can be set in accordance with the electromagnetic force of the electromagnetic coil 22, even when the fuel injection pressure is low,
By increasing the electromagnetic force, the set force of the spring 19 can be increased. Therefore, it is possible to prevent bounce of the needle valve 18 when the injection hole 17 is closed, prevent drooping of fuel, and prevent deterioration of exhaust gas performance of the engine.

Further, according to the above configuration, since there is no sliding portion such as a piston that separates the high-pressure portion and the low-pressure portion unlike the related art, fuel does not leak. Thereby, fuel loss can be prevented, and fuel efficiency can be improved.

In the present invention, the water jacket 25 is formed around the fuel injection device 7 to cool the fuel injection device 7, so that the electromagnetic valve portion including the electromagnetic coil 22 and the core 39 can be cooled. As a result, a decrease in the electromagnetic force due to a rise in temperature can be prevented, the electromagnetic force can be stabilized, and the opening and closing of the injection hole 17 can be more stably controlled.

Further, since the fuel supply passage 37 is provided in the central portion of the electromagnetic coil 22 and the core 39 to allow fuel to pass through, the cooling effect of the electromagnetic valve portion is further improved.

The fuel injection device 7 is provided with a needle valve 1 from the mover 21.
8 can be shortened, and the overall height can be shorter than that of the conventional fuel injection device 51 shown in FIG. In addition to the above advantages, the overall height of the engine can be reduced, and compactness, light weight, and low center of gravity can be achieved.

In the present embodiment, a common rail type fuel supply system has been described as an example. However, the fuel injection mechanism 26 of the present invention can be applied to a fuel supply system without a common rail. Of course.

[0047]

In summary, according to the present invention, even if the fuel injection pressure is low, the opening and closing of the injection hole can be controlled stably without being affected by the low fuel injection pressure. As compared with, the overall height can be reduced, and an excellent effect such as downsizing is achieved.

By cooling the electromagnetic coil, the electromagnetic force can be stabilized, and more stable control of the opening and closing of the injection hole is achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of a fuel injection device for a fuel injection mechanism according to the present invention.

FIG. 2 is a sectional view showing a preferred embodiment of a fuel injection mechanism according to the present invention.

FIG. 3 is a schematic configuration diagram showing a fuel supply system of a dimethyl ether engine.

FIG. 4 is a schematic configuration diagram showing a conventional dimethyl ether engine fuel injection device.

FIG. 5 is a schematic configuration diagram showing a mounting state of a conventional dimethyl ether engine fuel injection device.

[Explanation of symbols]

 Reference Signs List 5 fuel injection pump 7 fuel injection device 16 combustion chamber 17 injection hole 18 needle valve 19 spring 21 mover 22 electromagnetic coil 23 main body body 24 cylinder head 25 water jacket 26 fuel injection mechanism

Claims (2)

[Claims] 1. A direct injection type fuel injection mechanism for directly injecting fuel, which has been raised to a predetermined pressure by a fuel injection pump, into a combustion chamber of an engine, comprising: a needle valve for opening and closing an injection hole; The main body of the fuel injection device, which includes a spring for urging the needle valve in the closing direction and an electromagnetic coil for moving the mover integrated with the needle valve in the opening direction of the injection hole, is housed in the cylinder head. A fuel injection mechanism, wherein a water jacket for cooling the fuel injection device is formed in the cylinder head. 2. The fuel injection mechanism according to claim 1, wherein the fuel is a dimethyl ether fuel.