JP2000018120A - Common rail fuel injector injector - Google Patents

Abstract

(57) [Summary] [Problem] To reduce dynamic leakage of pressurized fuel, reduce pump capacity, improve fuel efficiency, and the like. SOLUTION: The injector of the common rail type fuel injection device according to the present invention has a hole 29 in which a needle upper end portion 31 is inserted into a nozzle body and pressurized fuel acting on the upper end surface 32 is introduced through a throttle passage 42. A pressure control chamber 33 which is opened to the hole to raise the needle 2 by leaking fuel in the hole, and at least one of the needle or the nozzle body is brought into contact with a counterpart when the needle is lifted, and A protrusion-like stopper 44 for closing the inlet 43 of the pressure control chamber is provided, and the protrusion-like stopper is formed in such a size that pressurized fuel acts on the upper end surface of the needle when the inlet is closed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector for a common rail type fuel injection device applied to a diesel engine, a direct injection gasoline engine, and the like.

[0002]

2. Description of the Related Art Generally, in a common rail type fuel injection device, fuel pressurized by a high pressure pump is supplied to a common rail (accumulation chamber).
The fuel is temporarily stored in the cylinder, and is injected into the respective cylinders from the injector by a predetermined amount at a predetermined timing.

[0003] The injector opens and closes an injection hole provided at the lower end or the tip thereof by raising and lowering a needle (needle valve) to execute fuel injection. In particular, the needle is immersed in the high-pressure fuel, so as to be in a floating state, a downward (valve closing direction) force is applied to the needle by a spring member, and the needle tip is pressed against the valve seat to close the valve. There is something to put. In this case, the downward fuel pressure applied to the upper end of the needle is controlled by a pressure control chamber (balance chamber), and by appropriately leaking high-pressure fuel in the pressure control chamber, the pressure balance with respect to the needle is broken, the needle is raised, and the valve is opened. It is made to let.

FIG. 10 shows a main part of the injector previously proposed by the present applicant (Japanese Patent Laid-Open No. 10-77924). A fuel passage 82 is formed in the nozzle body 81, and pressurized or high-pressure fuel sent from a common rail is always supplied to the fuel passage 82. The fuel in this passage is sent to the injection hole below in the figure, and wraps around the needle 83 so that the needle 83 is floated. 84
Is a pressure control chamber, in which high-pressure fuel in the fuel passage 82 is always introduced through a fuel introduction passage 85 serving as a throttle passage. A spring 86 and a spring receiver 87 are provided in the pressure control chamber 84.
A downward force is always applied to the needle 83 via the.

[0005] When the valve is closed, the needle 83 comes into contact with the lower valve seat to close the injection hole. At this time, the needle 83 receives almost all the pressure of the high-pressure fuel except for a small area on the inner peripheral side of the valve seat at the tip, and is in a substantially pressure-balanced state. Therefore, the needle 83 is lowered by the force of the relatively weak spring 86 and can be pressed against the valve seat.

On the other hand, when the valve body 88 is lowered in the pressure control chamber 84 and the outlet 89 is opened, high-pressure fuel in the pressure control chamber 84 leaks from the outlet 89, and the pressure in the chamber is reduced, and the pressure balance with the needle 83 is reduced. Crumble. When this occurs, the needle 83 rises, the injection hole is opened, and fuel injection is performed. As described above, the fuel injection control is performed by controlling the up and down movement of the valve body 88. For this reason, an actuator such as a solenoid (not shown) is provided above the valve shaft 90, and the energization of this actuator is controlled by the electronic control unit based on the operating state of the engine.

The valve body 88 is a self-sealing valve that opens and closes an outlet 89 in the pressure control chamber 84. That is, as the indoor pressure increases, the pressure is strongly pressed against the valve seat around the inlet of the outlet 89, and the sealing pressure is increased. Therefore, there is an advantage that static leakage of the pressure control chamber 84 can be completely prevented even when the fuel pressure increases during a high-load operation or the like.

[0008]

However, in such an injector, there is a problem that a dynamic leak is remarkably generated. That is, during execution of fuel injection, the outlet 89 is opened and fuel in the pressure control chamber 84 leaks, but also at this time, high-pressure fuel is constantly introduced into the pressure control chamber 84. In other words, in such a structure, the internal pressure is maintained while the high-pressure fuel always passes through the pressure control chamber 84. Therefore, the pump capacity must be increased more than necessary. This causes deterioration of fuel efficiency and high cost.

[0009]

According to the present invention, there is provided an injector for a common rail type fuel injection device, wherein a needle upper end is inserted into a nozzle body, and a hole for introducing pressurized fuel acting on the upper end of the needle body. A pressure control chamber for raising the needle by opening the hole and leaking fuel in the hole, and providing at least one of the needle or the nozzle body with the counterpart when the needle is raised to contact the other party. A protruding stopper for closing the inlet is provided, and the protruding stopper is formed in such a size that pressurized fuel acts on the upper end surface of the needle when the inlet is closed.

Here, the projection-shaped stopper surrounds the pressure control chamber inlet and has a ring shape smaller in diameter than the needle upper end surface, and is provided on at least one of the needle and the nozzle body at the outer periphery of the projection-shaped stopper. It is preferable that another protruding stopper is provided intermittently to be in contact with the counterpart when the needle is raised.

A self-sealing valve for opening and closing the outlet of the pressure control chamber in the chamber is provided. The self-sealing valve is projected from the inlet of the pressure control chamber into the hole, and the self-sealing valve is provided at the upper end of the needle. Preferably, a recess is provided for inserting the projection of the valve.

[0012]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 9 shows an entire injector according to the present invention. As shown, a needle 2 is inserted into a nozzle body 1 so as to be able to move up and down, and a plurality of injection holes 3 at the lower end or the tip of the nozzle body 1 are simultaneously formed. It can be opened and closed.

In the nozzle body 1, the needle 2 is immersed in high-pressure fuel and is in a floating state. A downward force (valve closing direction) is constantly applied to the needle 2 by a spring 16, and the needle tip normally abuts the valve seat at the tip of the nozzle body to close the injection hole 3. By appropriately releasing the downward fuel pressure applied to the upper end of the needle in the pressure control chamber (balance chamber) 33, the pressure balance with respect to the needle is broken, the needle is raised, and the injection hole 3 is opened.

In the nozzle body 1, a first piece 5, a second piece 6, and a third piece 7 are sequentially and coaxially mounted below a central nozzle body 4 at a central portion in a height direction, and these are fixed by a retaining nut 8. Are collectively stored.
The relative position in the circumferential direction between the central nozzle body 4 and the first piece 5 is defined by the positioning pin 9. Needle 2 is second,
Center holes 29,1 provided in the axial centers of the third pieces 6,7
It is charged in 0. In particular, the center hole 29 of the second piece 6 forms the hole of the present invention. A predetermined gap 11 is provided between the outer peripheral surface of the needle 2 and the inner peripheral surface of the center hole 10 of the third piece 7, and the passage of fuel is allowed. This gap 11
Is connected to a fuel pipe 13 which leads to a common rail (not shown) via a fuel passage 12 formed inside the nozzle body 1. As a result, high-pressure fuel is constantly supplied to the gap 11, and the needle 2 receives the fuel pressure at the intermediate pressure receiving surface 14 and the pointed tip surface, and receives an upward force.

The fuel passage 12 and the gap 11 are connected to the third piece 7
The spring chamber 15 is provided with a spring 16. The spring chamber 15 is provided with a spring 16. Spring 16
A coil spring is used to be fitted on the outer peripheral side of the needle 2, and is sandwiched in a compressed state between the collar 17 formed integrally with the needle 2 and the second piece 6, and the needle 2 has a downward force. Has been granted.

A pressure controller 18 is provided directly above the needle 2. This will be described later. A pressing piston 19 is provided above the push piston 19, and a push pin 20 is provided above the press piston 19. The pressing piston 19 and the push pin 20 are urged upward by springs 21 and 22, respectively, and are in contact with each other. A solenoid 23 is provided above the push pin 20. When the solenoid 23 is ON, the push pin 20 and the pressing piston 19 are simultaneously lowered, and when the solenoid 23 is OFF, the push pin 20 and the pressing piston 19 are simultaneously raised. It has become. ON / OFF of the solenoid 23 is performed by an electronic control unit (not shown) connected thereto.

Although the push pin 20 is inserted into the center hole 24 of the central nozzle body 4, the passage of fuel is also allowed in the gap 25 between them, and in particular, the leak fuel is allowed to pass. That is, fuel leaks from the pressure control unit 18 when the injector is opened, and this fuel leaks from the gap on the outer peripheral side of the pressing piston 19, the gap between the contact portions between the pressing piston 19 and the push pin 20, and the gap 25. Through a nipple 28 and a leak pipe (not shown) to return to a fuel tank (not shown).

FIG. 8 shows the structure of the pressure control unit 18. As shown in the figure, a center hole 29 (a hole of the present invention) is formed through the second piece 6, and a chamber hole 30 machined from the bottom surface is formed in the first piece 5. The chamber hole 30 is the center hole 29
And the lower end is opened to the center hole 29. The chamber hole 30 defines a pressure control chamber 33 (balance chamber), and an opening at the lower end of the chamber hole 30 defines an inlet 43 of the pressure control chamber 33. The diameter of the chamber hole 30 is about half the diameter of the center hole 29. The upper end 31 of the needle 2 is inserted into the center hole 29 so as to be able to move up and down. The spring chamber 15 is the second
It is directly below the piece 6 and is isolated from the pressure control chamber 33.

The upper end of the chamber hole 30 is formed in a tapered shape having a smaller diameter as it goes upward. Then, a small hole 35 opening at the upper end or the apex position and along the axis is drilled from the bottom side. The outlet of the pressure control chamber 33 is defined by the small holes 35, and the fuel in the pressure control chamber 33 leaks upward through the small holes 35. However, since the shaft 36 is inserted into the small hole 35, the fuel leaks through the gap between the small hole 35 and the shaft 36. The outlet of the small hole 35 communicates with the piston insertion hole 38 via the concave portion 37. The leaked fuel is supplied to the piston insertion hole 38 and the pressing piston 1
It flows upward through the gap 9.

A valve body 39 is disposed in the pressure control chamber 33. The shaft 36 is pressed into the central hole 40 of the valve body 39,
Completely fixed by swaging. The valve body 39 and the shaft body 36 form a self-sealing valve 41 and move up and down integrally to open and close the small hole 35 in the pressure control chamber 33. Since the self-sealing valve 41 is disposed in the pressure control chamber 33 in this manner, the volume of the pressure control chamber 33 can be reduced accordingly, and the responsiveness can be improved. The lower end surface of the self-sealing valve 41 faces directly the upper end surface 32 of the needle 2. The upper end of the valve body 39 is tapered so as to follow the upper end of the small hole 35, and the tapered surfaces are in surface contact with each other. That is, small hole 3
The five tapered surfaces form the valve seat. This surface contact becomes stronger as the fuel pressure in the pressure control chamber 33 increases, thereby achieving self-sealing. Valve 39 and chamber hole 30
Of the pressure control chamber 33 is reduced.

The upper end of the shaft body 36 is projected upward from the small hole 35, and a tapered portion 46 having a larger diameter is formed at the upper end thereof. The pressing piston 1 is
9 abuts from above, and lowers the shaft 36 and the valve 39 together to open the small hole 35. During this downward movement, the tapered portion 46 enters the concave portion 37, whereby the pressing piston 19 abuts against the bottom surface of the piston insertion hole 38 on the outer peripheral side of the concave portion 37 and can be stopped. When the pressing piston 19 contacts the shaft 36, the tapered portion 46 closes the center hole 45 of the pressing piston 19 as shown in FIG.
When 9 rises and separates from tapered portion 46, leak fuel is also introduced into center hole 45, and discharge of leak fuel is promoted.

FIG. 1 shows the structure of the pressure controller 18 in more detail and conceptually. The center hole 29 is formed in a stepped shape, and its upper end is reduced in diameter so as to form a throttle passage 42 with a small gap between the needle upper end 31. Then, on the lower surface of the first piece 5, a ring-shaped projecting stopper 44 is formed integrally around the entrance 43. The upper end surface 32 of the needle 2 at the time of ascending abuts on the protruding stopper 44 as shown in the drawing. Thereby, the inlet 43 of the pressure control chamber 33 is completely closed. At this time, since the diameter of the protrusion stopper 44 is smaller than that of the needle upper surface 32, the outer peripheral portion of the needle upper surface 32 located on the outer peripheral side of the protrusion stopper 44 forms a predetermined space 47 between the lower surface of the first piece 5 and the first piece 5. Form.

Next, the operation of the injector will be described.

Referring to FIG. 1, FIG. 8, and FIG.
The high-pressure fuel introduced into the spring chamber 15 through the gap 2 between the needle upper end 31 and the center hole 29, particularly the throttle passage 42
Is always supplied to the upper side.

On the other hand, when the injection is stopped, the solenoid 23
The switch is turned off, and the push pin 20 and the pressing piston 19 are in the raised position. Therefore, the fuel after passing through the throttle passage 42 is
First, a downward force is applied to the needle upper end surface 32 in the space 47 to push down the needle 2 and open the inlet 43. Then, the high-pressure fuel enters the pressure control chamber 33 and pushes up the self-sealing valve 41 to close the small hole 35. As a result, the pressure in the center hole 29 and the pressure control chamber 33 is maintained at a high pressure, the needle 2 is held at the lowered position, and the valve closed state is maintained. At this time, the fuel pressure acts on the entire upper surface 32 of the needle.

Next, during execution of injection, the solenoid 23
It is turned ON, the push pin 20 and the pressing piston 19 are lowered, and the self-sealing valve 41 is pushed downward to
5 opens (see the phantom line in FIG. 1). Then, fuel leaks from the small holes 35 and the pressure inside the pressure control chamber 33 becomes low. That is, since the introduction of fuel is performed from the throttle passage 42, the amount of leak exceeds the amount of introduction, and the pressure in the room is reduced. As a result, the fuel pressure acting on the needle upper end surface 32 is released, the force balance is lost, the needle 2 rises, and the injection hole is opened.

The raised needle 2 abuts on the projection-like stopper 44 as shown in FIG. Then, the inlet 43 is closed, and on the other hand, the fuel that has passed through the throttle passage 42 is
And the pressure in the space 47 gradually increases. When this pressure reaches a predetermined pressure, the needle 2 slightly descends, and the inlet 43 is slightly opened. Then space 47
Since the fuel inside flows into the pressure control chamber 33, the pressure in the space 47 decreases, the needle 2 rises again, and the inlet 43 is closed.

Since the inlet 43 is opened intermittently and to a minimum by repeating the minute raising and lowering of the needle 2, the leakage of the high-pressure fuel is minimized, and the pump capacity is increased and the fuel consumption is prevented from deteriorating. it can.

During the minute elevation of the needle 2, the pressure in the space 47 and the pressure control chamber 33 is kept as high as possible, so that the solenoid 23 is turned off in order to terminate the fuel injection.
Immediately after the injection, the needle 2 is lowered, and the response at the end of the injection is also improved.

Further, since the throttle passage 42 is formed by the gap between the center hole 29 and the needle upper end 31, a constant passage can be obtained with high precision, and processing is easy. Thereby, the dispersion of the injection is improved and the injection characteristics are stabilized. In addition, the flow rate of the introduced fuel can be controlled by the size and length of the gap, and the degree of freedom in selecting the flow rate increases.

Next, another embodiment will be described. The same components are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

FIGS. 2 and 3 show an example in which another protruding stopper is intermittently provided around the outer periphery of the protruding stopper 44. FIG. That is, another projection-shaped stopper is composed of four fan-shaped divided projections 50, each of which is integrally formed on the lower surface of the first piece 5, arranged so as to form a concentric circle with the projection-shaped stopper 44, and And the same height. Grooves 51 are formed between the split protrusions 50 at 90 ° intervals in the radial direction, and the flow of fuel toward the inlet 43 is allowed. Note that another projection-shaped stopper is not limited to such a form, and may take various forms. For example, a circular projection may be arranged in a staggered manner. According to this, there is an advantage that the load on the protrusion-shaped stopper 44 at the time of the needle contact can be reduced.

FIG. 4 shows an example in which the aforementioned throttle passage is provided inside the needle. That is, a shaft hole 52 through which high-pressure fuel is introduced is provided inside the needle upper end portion 31.
2 has a central hole 29 through a throttle hole 53 (throttle passage).
Is communicated within. Here, the gap between the center hole 29 and the needle upper end 31 is extremely small, and has a so-called shaft seal structure in which the fuel cannot pass.

FIG. 5 shows an example in which the above-described throttle passage is provided inside the nozzle body. That is, an introduction hole 54 is provided inside the first piece 5 to reach the fuel passage 12 (see FIG. 8), and the introduction hole 54 and the center hole 29 are communicated with each other by the throttle hole 55 (throttle passage). As described above, the gap between the center hole 29 and the needle upper end 31 is small, and the shaft seal is provided.

FIG. 6 shows an example in which a projection-like stopper is provided on the needle side. That is, the protruding stopper 44 is omitted, and the diameter is larger than the inlet 43 and the needle upper end surface 32 is replaced.
A projecting stopper 56 having a smaller diameter is formed integrally with the needle upper end surface 32. The protruding stopper 56 is formed solid and contributes to reducing the volume of the center hole 29, that is, improving the response. Here, a throttle passage 42 similar to FIG. 1 is formed.

FIG. 7 shows an example in which the self-sealing valve 41 and the needle 2 have a so-called nested structure. That is, the pressure control chamber 33
The length of the pressure control chamber 3 is reduced.
A concave hole 57 (a concave portion) is provided in the needle upper end portion 31 which projects from the inlet 43 of the third member 3 into the center hole 29 and into which the projecting portion of the self-sealing valve 41 is inserted. The recess 57 has the same diameter and diameter as the pressure control chamber 33. The projecting stopper 44 is provided on the lower surface of the first piece 5, and the throttle passage 42 is also formed as in FIG. This configuration is advantageous for reducing the overall length of the injector.

In addition, the present invention can adopt various embodiments. For example, the protruding stopper may be provided on both the nozzle body and the needle.

[0039]

In summary, according to the present invention, the excellent effects of reducing the dynamic leakage of the pressurized fuel, reducing the pump capacity, improving the fuel efficiency, and the like are exhibited.

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view of a main part of an injector according to the present invention.

FIG. 2 is a vertical cross-sectional view showing another embodiment, and another protruding stopper is shown in a cross section taken along line AA of FIG. 3;

FIG. 3 is a bottom view showing another protruding stopper.

FIG. 4 is a longitudinal sectional view showing another embodiment.

FIG. 5 is a longitudinal sectional view showing another embodiment.

FIG. 6 is a longitudinal sectional view showing another embodiment.

FIG. 7 is a longitudinal sectional view showing another embodiment.

FIG. 8 is an enlarged longitudinal sectional view of the injector according to the present invention.

FIG. 9 is a longitudinal sectional view showing the entire injector according to the present invention.

FIG. 10 is a longitudinal sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle body 2 Needle 5 1st piece 6 2nd piece 29 Center hole 31 Upper end part 32 Upper end face 33 Pressure control chamber 35 Small hole 41 Self-sealing valve 42 Throttle passage 43 Inlet 44 Projection stopper 50 Divided projection 53 Throttle hole 55 Throttle hole Hole 56 protruding stopper 57 hollow

Claims (3)

[Claims] 1. A nozzle body having an upper end portion into which a needle is inserted and into which a pressurized fuel acting on the upper end surface is introduced, and a needle which is opened in the hole portion to leak fuel in the hole portion. And a pressure control chamber for raising the pressure, at least one of the needle or the nozzle body,
When the needle is raised, a projection-shaped stopper is provided which abuts on the other side to close the entrance of the pressure control chamber, and the projection-shaped stopper is sized so that pressurized fuel acts on the upper end surface of the needle when the entrance is closed. An injector for a common rail fuel injection device, wherein the injector is formed. 2. The projection-shaped stopper surrounds the pressure control chamber entrance and has a ring shape smaller in diameter than the needle upper end surface, and is located on at least one of the needle and the nozzle body at an outer periphery of the projection-shaped stopper. 2. The injector for a common rail fuel injection device according to claim 1, wherein another protrusion-shaped stopper that abuts on the other side when the needle is raised is intermittently provided. 3. A self-sealing valve for opening and closing the outlet of the pressure control chamber in the chamber, the self-sealing valve protruding from the inlet of the pressure control chamber into the hole, and the self-sealing valve is provided at an upper end of the needle. 3. The injector according to claim 1, further comprising a recess into which the protrusion of the valve is inserted.