JP2000018116A - Injector of common rail type fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve response of a needle and fuel injection characteristics by reducing capacity of a pressure control chamber. SOLUTION: In an injector of a common rail type fuel injection system, a hole 8 having the upper end surface 15 is formed in a nozzle body 1, and a pressure control chamber 5 is formed between the upper end surface 15 of the hole and the upper end surface 25 of the needle by inserting the upper end portion 4 of the needle into the hole 8. The injector is provided with a compression member 20 that is pressed by the pressurized fuel and a spring member 3 within a fuel space separated from the pressure control chamber 5 to project from the upper end surface 15 of the hole or the upper end surface 25 of the needle and to be pressed.

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. 4 shows a main part of the injector previously proposed by the present applicant (JP-A-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. Reference numeral 84 denotes a pressure control chamber, in which a fuel introduction passage 8 serving as a throttle passage is provided.
5, high-pressure fuel in the fuel passage 82 is always introduced. A spring 86 as a spring member and a spring receiver 87 are provided in the pressure control chamber 84, and the spring 86 constantly applies a downward force to the needle 83 via the spring receiver 87.

[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. That is, at this time, the amount of leakage from the outlet 89 exceeds the amount of introduction from the fuel introduction passage 85. 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]

Incidentally, in order to improve the fuel injection characteristics, it is preferable to reduce the volume of the pressure control chamber 84. That is, by reducing the volume, the pressure in the room is quickly changed, and the ON / OFF of the actuator, that is, the outlet 89 is used.
The response of the needle 83 to the opening and closing of the needle 83 can be improved.

In particular, when controlling the fuel injection rate, the control of the initial injection rate (rise of fuel injection) is performed by controlling the valve element 8.
There are improvement measures on the actuator side, such as increasing the descent speed of 8 and increasing the descent amount. However, at the end of injection, the volume of the pressure control chamber 84 has a great influence, and the same improvement measures cannot be taken. That is, the rising speed of the valve body 88 is increased, and the outlet 8
Even if the valve 9 is closed early, the fuel introduction passage 8
Since only a constant flow rate of fuel according to the passage area of No. 5 enters, if the volume is large, it is difficult to increase the pressure, and as a result, the timing of lowering the needle 83 is delayed. In such a case, the injection end timing is delayed, the injection time is lengthened, and the exhaust gas and fuel consumption are deteriorated.

However, in the above structure, the pressure control chamber 84 has a cross-sectional area that covers the entire upper end surface of the needle and changes the pressure on the entire upper end surface of the needle. Is not enough. That is,
In this type of injector, it is only necessary to break or restore the pressure balance with respect to the needle 83, so that it is not always necessary to change the pressure over the entire upper end surface of the needle.

[0011]

According to the present invention, a hole having an upper end face is provided in a nozzle body, and an upper end of a needle is inserted into the hole so that a pressure is formed between the upper end face of the hole and the upper end face of the needle. In the injector of the common rail type fuel injection device in which the control chamber is defined, the pressurized fuel and the spring member push the pressurized fuel and the spring member in the fuel space separated from the pressure control chamber to protrude from the upper end face of the hole or the upper end face of the needle. And a pressing member that is pressed against the other party.

Further, according to the present invention, a hole having an upper end surface is provided in a nozzle body, an upper end of a needle is inserted into the hole, the diameter of an upper portion of the insertion portion is reduced, and a sleeve is moved up and down in the reduced diameter portion. A spring member is disposed between the sleeve and the lower end of the reduced diameter portion by freely fitting, and the sleeve is pressed against the upper end surface of the hole by the spring member. The pressure control chamber is defined by the inner peripheral surface.

Further, according to the present invention, a hole having an upper end surface is provided in the nozzle body, and an upper end portion of the needle is inserted into the hole portion, and a receiving hole is formed in the upper end portion of the needle so as to extend downward from the upper end surface. A piston member is fitted to the upper portion of the receiving hole so as to be vertically movable, and a spring member is disposed between the piston member and the lower end of the receiving hole. The piston member is pressed against the upper end surface of the hole by the spring member. The pressure control chamber is defined by the upper end surface of the hole, the inner peripheral surface of the hole, the upper end surface of the needle, and the outer peripheral surface of the piston member.

Further, according to the present invention, a hole having an upper end surface is provided in the nozzle body, an upper end portion of the needle is inserted into the hole portion, and a receiving hole is formed in the nozzle body so as to face upward from the upper end surface of the hole portion. A piston member is fitted to the lower part of the accommodation hole so as to be vertically movable, and a spring member is provided between the piston member and the upper end of the accommodation hole. The spring member presses the piston member against the upper end surface of the needle. The pressure control chamber is defined by the upper end surface of the hole, the inner peripheral surface of the hole, the upper end surface of the needle, and the outer peripheral surface of the piston member.

[0015]

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

FIG. 1 shows a main part of an injector according to a first embodiment. As shown, a needle 2 (needle valve) is inserted into a nozzle body 1 so as to be able to move up and down. A plurality of lower injection holes are opened and closed at the same time by raising and lowering the nozzle 2.

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 the spring 3, and the lower end of the needle, which is not shown in the drawing, normally abuts the valve seat at the front end of the nozzle body to close the injection hole. By appropriately releasing the downward fuel pressure applied to the needle upper end portion 4 in the pressure control chamber (balance chamber) 5, the pressure balance with respect to the needle 2 is broken, the needle 2 is raised, and the injection hole is opened. ing.

The nozzle body 1 has an upper nozzle body 6 and a lower nozzle body 7 joined to each other. The lower nozzle body 7 has a large-diameter hole 8 in the upper part and a small-diameter hole 9 in the lower part, and accommodates the needle 2 in these holes 8 and 9 so as to be able to move up and down. That is, the needle 2 also has a large-diameter upper end 4.
And a shaft portion 11 having a small diameter. The upper end portion 4 is accommodated in the large-diameter hole 8, and the shaft portion 11 is accommodated in the small-diameter hole 9.

The upper end 4 of the needle 2 and the shaft 11 are connected by a tapered portion 12, and the tapered portion 12 is housed in a fuel reservoir 13 connecting the large diameter hole 8 and the small diameter hole 9. Fuel reservoir 1
A fuel passage 14 formed in the upper nozzle body 6 and the lower nozzle body 7 is opened in 3 so that pressurized or high-pressure fuel sent from the common rail is always introduced. The fuel in the fuel chamber 13 is supplied to the shaft 11 and the small-diameter hole 9.
Flows downward toward the nozzle hole. In the fuel reservoir 13, the fuel pressure acts on the tapered portion 12 and applies an upward force to the needle 2.

The upper opening of the large-diameter hole 8 is closed by the upper nozzle body 6, the large-diameter hole 8 defines the hole of the present invention, and the lower end surface 15 of the upper nozzle body 6 defines the upper end of the hole of the present invention. Eggplant The upper end 17 of the needle upper end portion 4 is reduced in diameter in a stepped manner with respect to a lower portion 16 having a reference diameter. The upper portion 17 forms the reduced diameter portion of the present invention. The large-diameter hole 8 has a constant inner diameter along the height direction, and guides the fuel in the fuel storage chamber 13 upward from a gap 18 between the large-diameter hole 8 and the lower portion 16.

The springs 3 (coil springs) forming a spring member of the present invention are arranged on the needle upper part 17 in order from the bottom.
And the sleeve 20 (pressing member) are fitted. The sleeve 20 is vertically movable relative to the needle upper part 17. The spring 3 includes a sleeve 20 and an upper lower end surface 21.
(The lower end of the reduced diameter portion of the present invention), which is compressed and presses the sleeve 20 against the lower end surface 15 of the upper nozzle body 6 and simultaneously presses the needle 2 downward. The upper end of the sleeve 20 has an edge-like cross section, and the outer peripheral side is formed into a cylindrical shape having a constant diameter, and the inner peripheral side is formed into a tapered shape which expands upward.

In particular, a gap 21 between the outer peripheral surface of the sleeve 20 and the inner peripheral surface of the large-diameter hole 8 forms a throttle passage for fuel so that a small amount of fuel can flow. That is, the gap 21 is smaller in the radial direction than the gap 18 and has a predetermined length in the axial direction. In addition, there is almost no gap between the inner peripheral surface of the sleeve 20 and the outer peripheral surface of the needle upper portion 17, and it is just about the size that allows relative movement, and does not allow the passage of fuel. Thus, a shaft seal is formed between the sleeve 20 and the needle upper part 17.

At the lower end of the upper nozzle body 6, a large-diameter hole 8
And a small diameter valve chamber hole 22 is provided. Valve chamber hole 22
Has a pentagonal cross section and a tapered upper end. Leak hole 2 at the upper end of valve chamber hole 22
3 is drilled, and the leak hole 23 is formed above the leak passage 2.
4 is opened.

As described above, the pressure control chamber 5 is defined by the valve chamber hole 22, the lower end surface 15 of the upper nozzle body 6, the upper end surface 25 of the needle 2, and the inner peripheral surface of the sleeve 20.

The leak hole 23 is opened and closed by a self-sealing valve 26 in the valve chamber hole 22. That is,
The self-sealing valve 26 is a valve body 2 housed in the valve chamber hole 22.
7 and a valve shaft 28 that is inserted into the leak hole 23 with a small gap, and is configured as a so-called poppet valve. The valve body 27 also has a pentagonal cross section, and its upper end is tapered so as to follow the upper end of the valve chamber hole 22 so that it can be seated in a planar manner on the valve seat around the inlet of the leak hole 23. According to this configuration, the valve body 27 is strongly pressed as the pressure in the pressure control chamber 5 increases, and static leakage can be completely prevented.
The self-sealing valve 26 is driven to move up and down by an actuator (solenoid, piezo-electric element, etc.) at the top of the figure. The valve chamber hole 22 has a very small inner diameter that allows the fuel immediately before the leak to pass radially outward of the valve body 27,
The length is just about the size that can cover the up-and-down stroke of the valve body 27.

Next, the operation of the injector will be described.

First, when fuel injection is stopped, as shown in FIG. 1, the self-sealing valve 26 closes the leak hole 23, the pressure control chamber 5 is filled with high-pressure fuel, the needle 2 is at the lowered position, and the injection hole is closed. Can be At this time, the sleeve 20 is pushed up by the spring 3 and the high-pressure fuel in the surrounding fuel space and is in contact with the lower end surface 15. And gap 1
The high-pressure fuel guided upward from 8 stays in the gap 21 around the sleeve 20.

Next, when the fuel injection is performed, the self-sealing valve 26 is lowered to open the leak hole 23, and the high-pressure fuel in the pressure control chamber 5 leaks from the leak hole 23, and the pressure in the pressure control chamber 5 becomes low. Then, the pressure balance is lost and the needle 2 rises, the injection hole is opened, and fuel injection is performed.

When the pressure in the pressure control chamber 5 is reduced, a pressure difference is generated between the inner and outer circumferences of the sleeve 20, and the sleeve 20 is lowered by this pressure difference, and the high-pressure fuel waiting in the gap 21 is transferred to the pressure control chamber 5. Flow in. When the pressure in the pressure control chamber 5 is increased, the differential pressure decreases, the sleeve 20 returns to the original position, and the inflow of fuel is shut off. The sleeve 20 repeats such a small vertical movement while the pressure control chamber 5
High-pressure fuel intermittently. According to this, the dynamic leak can be reduced and the high-pressure fuel consumption can be reduced as compared with the prior application (FIG. 4) in which the fuel is always introduced and leaked. Further, the pump capacity can be reduced, and the fuel efficiency can be improved.

Here, when the sleeve 20 is raised, the sleeve 20 is in contact with the lower end face 15 all around.
Although a downward force does not appear to be applied to the sleeve 20, the gap 20 exists microscopically, and the sleeve 20 can be pushed down by the fuel flowing into this gap.

In the above configuration, the upper portion 17 of the needle upper end 4 is reduced in diameter, the sleeve 20 is fitted into the reduced diameter portion, and the lower end surface 15, the upper end surface 25 and the inner peripheral surface of the sleeve 20 are joined together. Since the pressure control chamber 5 is partitioned, the radial size of the pressure control chamber 5 can be reduced, and the volume can be reduced. As a result, the pressure can be changed quickly, the response of the needle 2 can be increased, and the fuel injection characteristics can be improved. On the other hand, even if the area of the pressure control surface (upper end surface 25) of the needle 2 is reduced in this way, the pressure balance with respect to the needle 2 can be surely broken, so that there is no operational problem.

Also, the volume of the pressure control chamber 5 can be reduced by the point that the spring 3 is extended out of the pressure control chamber 5 and the valve chamber hole 22 is formed almost the size of the valve body 27.

Further, the amount of fuel flowing into the pressure control chamber 5 can be adjusted by the outer diameter and length of the sleeve 20, and the sleeve 20 can be easily processed, so that the degree of freedom can be increased.

[Second Embodiment] FIG. 2 shows a second embodiment. The same components are denoted by the same reference numerals in the drawings, and description thereof will be omitted. As shown, an intermediate piece 30 is provided between the upper nozzle body 6 and the lower nozzle body 7. In the pressure control chamber 5, the portion of the valve chamber hole 22 is moved above the intermediate piece 30, and has a so-called separation structure. And the part of the large diameter hole 8 and the part of the valve chamber hole 22
The intermediate pieces 30 communicate with each other through a communication path 31 provided in the intermediate piece 30. The fuel passage 32 is also provided in the intermediate piece 30.

The upper end 4 of the needle is formed to have a constant outer diameter without a reduced diameter portion, forms a throttle passage with a gap 33 between the large diameter hole 8 and always introduces the fuel in the fuel reservoir 13 into the pressure control chamber 5. . In particular, an accommodation hole 34 having a predetermined depth is formed in the axial center of the needle upper end 4 downward from the needle upper end surface 25. A spring 3 serving as a spring member is provided below the accommodation hole 34.
5 (coil spring) is provided, and a cylindrical piston member 36 (pressing member) is fitted to the upper part so as to be able to move up and down.

The accommodation hole 34 communicates with the fuel reservoir 13 through a communication passage 37 provided below the accommodation hole 34 to form a fuel space separated from the pressure control chamber 5. That is, the piston member 3
The gap between 6 and the accommodation hole 34 is small, and is large enough to allow only their relative movement and not allow fuel to pass through. The spring 35 is arranged in a compressed state, and constantly presses the piston member 36 against the lower end surface 38 of the intermediate piece 30 and simultaneously presses the needle 2 downward. Therefore, the piston member 36 is held at a fixed position with respect to the needle 2 that moves up and down,
The needle is always in contact with the upper end surface 25 of the needle.

According to this configuration, the lower end face 38, the large-diameter hole 8
A part of the pressure control chamber 5 is formed in a ring shape by the inner peripheral surface, the needle upper end surface 25 and the outer peripheral surface of the piston member 36. In particular, the volume of the pressure control chamber 5 can be reduced by the insertion of the piston member 36. Further, since the piston member 36 and the needle 2 do not necessarily have to be coaxial, manufacture is easy.

Here, the housing hole 34 is always filled with high-pressure fuel via the communication passage 37, and the decrease in the pressurized area by the piston member 36 is compensated for at the bottom surface of the housing hole 34. When the needle 2 moves up and down, fuel is breathed from the communication passage 37 in response to this. Here, unlike the above, since high-pressure fuel is always introduced into the pressure control chamber 5 through the gap 33, a dynamic leak occurs.

[Third Embodiment] FIG. 3 shows a third embodiment. The same components are denoted by the same reference numerals in the drawings, and description thereof will be omitted. As shown in the figure, here, the intermediate piece 3
The thickness of the intermediate piece 30 is increased, and a receiving hole 34 that extends upward from the lower end face 38 is formed in the axial center portion of the intermediate piece 30. A spring 35 is provided at an upper portion of the housing hole 34, and a piston member 36 (pressing member) is fitted to a lower portion so as to be able to move up and down. In the intermediate piece 30, the accommodation hole 34 introduces high-pressure fuel from the fuel passage 32 through the communication passage 40. The valve chamber hole 22 is separated as described above, and the upper nozzle body 6 and the intermediate piece 3 are separated.
0 communicates with the large-diameter hole 8 through a communication passage 31. The point that the piston member 36 and the receiving hole 34 form a shaft seal is the same. On the other hand, unlike the above, the needle upper end 4
The large diameter hole 8 also forms a shaft seal. The accommodation hole 34 and the valve chamber hole 22 communicate with each other through a small hole 41 as a throttle passage.

Also in this configuration, the lower end surface 3
8, a part of the pressure control chamber 5 is formed into a ring shape by the inner peripheral surface of the large diameter hole 8, the needle upper end surface 25, and the outer peripheral surface of the piston member 36. In particular, the volume of the pressure control chamber 5 can be reduced by the insertion of the piston member 36.

In this injector, the fuel passage 3
The high-pressure fuel is always introduced into the large-diameter hole 8 of the pressure control chamber 5 through the communication passage 40, the housing hole 34, the small hole 41, the valve chamber hole 22, and the communication passage 31. On the other hand, the introduced fuel is leaked from the leak hole 23 through the path of the communication passage 31 and the valve chamber hole 22, but also at this time, since the fuel is supplied from the small hole 41 to the valve chamber hole 22, Leakage occurs.

As described above, the present invention can employ various embodiments.

[0043]

In summary, according to the present invention, the pressure control chamber can be reduced in volume, and the excellent effects of improving the response of the needle, improving the fuel injection characteristics, and the like can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an injector according to a first embodiment.

FIG. 2 is a longitudinal sectional view of an injector according to a second embodiment.

FIG. 3 is a longitudinal sectional view of an injector according to a third embodiment.

FIG. 4 is a longitudinal sectional view of a conventional injector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle body 3 Spring 4 Upper end part 5 Pressure control chamber 8 Large diameter hole 15 Lower end face 17 Upper part 20 Sleeve 21 Upper lower end face 34 Housing hole 35 Spring 36 Piston member

Claims (4)

[Claims] 1. A common rail type in which a hole having an upper end surface is provided in a nozzle body, and a pressure control chamber is defined between the upper end surface of the needle and the upper end surface of the needle by inserting an upper end portion of the needle into the hole portion. In the injector of the fuel injection device, a pressing member protruding from the upper end surface of the hole or the upper end surface of the needle and pressed against the other by being pressed by the pressurized fuel and the spring member in the fuel space separated from the pressure control chamber. An injector for a common rail fuel injection device, wherein the injector is provided. 2. A hole having an upper end surface is provided in the nozzle body, an upper end of the needle is inserted into the hole, the diameter of the upper part of the insertion portion is reduced, and a sleeve is fitted to the reduced diameter portion so as to be movable up and down. A spring member is disposed between the sleeve and the lower end of the reduced diameter portion in combination,
An injector for a common rail fuel injection device, wherein the spring member presses the sleeve against the upper end surface of the hole, and a pressure control chamber is defined by the upper end surface of the hole, the upper end surface of the needle, and the inner peripheral surface of the sleeve. 3. A hole having an upper end surface is provided in the nozzle body, an upper end portion of the needle is inserted into the hole portion, and a receiving hole is formed in the upper end portion of the needle so as to extend downward from the upper end surface. A piston member is fitted to the upper part of the hole so as to be vertically movable, and a spring member is disposed between the piston member and the lower end of the receiving hole. The spring member presses the piston member against the upper end surface of the hole, and An injector for a common rail type fuel injection device, wherein a pressure control chamber is defined by an upper end surface of a portion, an inner peripheral surface of a hole, an upper end surface of a needle, and an outer peripheral surface of a piston member. 4. A hole having an upper end surface is provided in the nozzle body, an upper end portion of the needle is inserted into the hole portion, and a receiving hole is formed in the nozzle body so as to extend upward from an upper end surface of the hole portion. A piston member is fitted to the lower part of the accommodation hole so as to be able to move up and down, and a spring member is provided between the piston member and the upper end of the accommodation hole. The spring member presses the piston member against the upper end surface of the needle. An injector for a common rail fuel injector, wherein a pressure control chamber is defined by an upper end surface, an inner peripheral surface of a hole, an upper end surface of the needle, and an outer peripheral surface of a piston member.