WO2010124464A1

WO2010124464A1 - Pressure control valve and fuel injection device for an internal combustion engine

Info

Publication number: WO2010124464A1
Application number: PCT/CN2009/071584
Authority: WO
Inventors: Xiaojian Wu; Friedemann Weber; Jianxiong Gong; He ZHU
Original assignee: Bosch Automotive Diesel Systems Co., Ltd.
Priority date: 2009-04-30
Filing date: 2009-04-30
Publication date: 2010-11-04
Also published as: CN103026044B; CN103026044A

Abstract

A pressure control valve comprises a valve seat (38), a valve body (40) and a valve rod (42) housed and being slidable axially in an axial through bore (52) of the valve body. The valve rod (42) comprises a cylindrical stem (54), a head (56) and a central passage (60) extending through the stem and the head. The head is received in a concave cavity of the valve body. The valve body (40) also comprises a branch passage leading into an annular chamber (59) between the outer surface of the valve rod and the inner surface of the axial through bore. The head of the valve rod and the concave cavity are shaped and dimensioned such that the head of the valve rod mates in fluid-tight manner with the wall of the concave cavity to form a first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward. At least one through hole is formed in the valve seat.

Description

Pressure control valve and fuel injection device for an internal combustion engine

FIELD OF THE INVENTION

The present invention relates to a pressure control valve for a fuel injection device and a fuel injection device to be used for an internal combustion engine.

BACKGROUND OF THE INVENTION

A fuel injection device with which the fuel can be injected directly into a combustion chamber of an internal combustion engine is known on the market. The fuel injection device comprises generally a housing, a needle-like valve element for opening or closing fuel outlet openings, and a pressure control valve for controlling the pressure in a control chamber defined in the housing so that the needle-like valve element may move to open or close the fuel outlet openings as a function of the pressure in the control chamber.

US2003/0102452A1 discloses a common rail fuel injection device for injecting fuel in an internal combustion engine, having a housing, which communicates with a central high-pressure reservoir and in which a nozzle needle is axially displaceable in order to adjust the injection as a function of the pressure in a control chamber, and having a sealing element, which is disposed in an annular chamber that is provided between a valve element and the housing. To lengthen the service life, in addition to the sealing element, a support device is disposed in the annular chamber between the valve element and the housing. Such fuel injection device uses the high pressure sealing element and the additional support device, which increase the manufacture costs.

US2008/0210787A1 discloses a fuel injection device comprising a housing and a valve element disposed therein and cooperating with a valve seat located in the area of at least one fuel discharge port. The valve element is composed of several parts while at least two parts of the valve element are coupled to each other via a hydraulic coupler. Although such fuel injection device does not use the high pressure sealing element, it has complex pressure circuits, which increases the manufacture costs too.

EP1612398B1 discloses a fuel injection device. The fuel injection device comprises a control servo valve which is housed inside the housing of the fuel injection device, and has a piezoelectric actuator, and a control chamber having a fuel outlet passage. The outlet passage comes out inside an annular chamber defined by a fixed tubular portion and by a shutter, which engages the tubular portion in substantially fluid-tight manner and is slid axially by the piezoelectric actuator from a closed position, in which it closes the annular chamber and is subjected to a zero axial resultant force by the fuel pressure, to an open position, in which the outlet passage communicates with a discharge conduit. In such a fuel injection device, the high pressure fuel from a high pressure fuel passage goes directly into the control chamber. When the piezoelectric actuator exerts axial thrust on the shutter to open the injection nozzle, the high pressure fuel passage communicates with a low pressure circuit (LPC) via the control chamber, the fuel outlet passage and the annular chamber. To prevent the high pressure in the high pressure fuel passage from dropping dramatically so that the fuel can not be injected desirably from the injection nozzle, the fuel outlet passage is provided with a calibrated section hole. The calibrated section hole must be designed and manufactured precisely so that the fuel injection device is complicated in structure and is difficult to be manufactured.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a pressure control valve for a fuel injection device and a fuel injection device for an internal combustion engine, which are simple in structure, are capable of being manufactured easily and in a low-cost manner and improve the reliability in operation.

According to one aspect of the present invention, there is provided a pressure control valve for a fuel injection device, comprising: a valve seat; a valve body disposed on the valve seat, the valve body comprising an axial through bore and a concave cavity formed in a lower end of the axial through bore; and a valve rod housed in the axial through bore and being slidable axially in the axial through bore in a substantially fluid-tight manner, an annular groove being arranged on an outer surface of the valve rod to form an annular chamber between the outer surface of the valve rod and the inner surface of the axial through bore, the valve rod comprising a cylindrical stem, a head formed at a lower end of the stem and a central passage extending through the stem and the head, the head being received in the concave cavity, and the valve body also comprising a branch passage leading into the annular chamber; wherein the head of the valve rod and the concave cavity are shaped and dimensioned such that the head of the valve rod mates in fluid-tight manner with the wall of the concave cavity to form a first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward, and the head of the valve rod spaces from the wall of the concave cavity to communicate the annular chamber with a space defined between the wall of the concave cavity and the outer wall of the head and to form a second fluid seal between the central passage of the valve rod and the space when the valve rod moves axially and downward to abut in fluid-tight manner against the valve seat; and at least one through hole is formed in the valve seat to communicate with the space defined between the wall of the concave cavity and the outer wall of the head.

According to other aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, comprising: a housing having a pressure chamber and fuel outlet openings formed therein, the pressure chamber communicating with a fuel supply passage; a needle-like valve element which is slidable axially within the housing so that the fuel outlet openings is disconnected from the pressure chamber or made to communicate with the pressure chamber; a pressure control valve disposed within the housing, the pressure control valve comprising: a valve seat disposed above the needle-like valve element so that a control chamber is defined between the valve seat and an upper end of the needle-like valve element; a valve body disposed on the valve seat, the valve body comprising an axial through bore and a concave cavity formed in a lower end of the axial through bore; and a valve rod housed in the axial through bore and being slidable axially in the axial through bore in a substantially fluid-tight manner, an annular groove being arranged on an outer surface of the valve rod to form an annular chamber between the outer surface of the valve rod and the inner surface of the axial through bore, the valve rod comprising a cylindrical stem, a head formed at a lower end of the stem and a central passage extending through the stem and the head, the head being received in the concave cavity, and the valve body also comprising a branch passage communicating the annular chamber and the fuel supply passage; wherein the head of the valve rod and the concave cavity are shaped and dimensioned such that the head of the valve rod mates in fluid-tight manner with the wall of the concave cavity to form a first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward, and the head of the valve rod spaces from the wall of the concave cavity to communicate the annular chamber with a space defined between the wall of the concave cavity and the outer wall of the head and to form a second fluid seal between the central passage of the valve rod and the space when the valve rod moves axially and downward to abut in fluid-tight manner against the valve seat; and at least one through hole is formed in the valve seat to communicate the control chamber with the space defined between the wall of the concave cavity and the outer wall of the head; a lifting mechanism for lifting axially and upward the valve rod of the pressure control valve; and a spring disposed at an upper end of the valve rod, the spring pushing the valve rod toward valve seat so that the head of the valve rod abuts in a fluid-tight manner against the valve seat.

For a clear understanding of the present invention, a preferred, non-limiting embodiment will be described by way of example with reference to the accompanying drawings, in which some parts are removed for clarity.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic, partially sectional view of the fuel injection device according to the present invention, showing the fuel injection device in a closed state; FIG. 2 is a partial magnification of FIG. 1;

FIG. 3 is a schematic, partially sectional view of the fuel injection device according to the present invention, showing the fuel injection device in an injection state; and

FIG. 4 is a partial magnification of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS 1 and 2, a fuel injection device for an internal combustion engine according to the present invention is indicated as a whole by "1". The fuel injection device 1 comprises a housing 10 with a nozzle body 12, a main body 14, and an end body 16. A nozzle needle 18 is movably received in the nozzle body 12 and a pressure chamber 20 is defined in the nozzle body 12 around the nozzle needle 18. Fuel outlet openings 22 are formed in a lower end of the pressure chamber 20. The nozzle needle 18 cooperates in a known manner with a valve seat of the nozzle body 12. In this way, the fuel outlet openings 22 can be disconnected from the pressure chamber 20 or made to communicate with it.

The main body 14 defines a lower bore 24 and an upper stepped recess 26. The lower bore 24 houses a plunger 28 which may slide axially inside the lower bore 24. A spring 30 is braced on the lower portion of the plunger 28 via an annular projection 32 formed inside the lower bore 24 and an annular collar 34 on the nozzle needle 18. The spring 30 always tends to push the nozzle needle 18 to close the fuel outlet openings 22. The plunger 28 and the nozzle needle 18 together are called as a needle-like valve element. It should be understood that the plunger 28 and the nozzle needle 18 may be integral with each other.

The upper stepped recess 26 of the main body 14 houses a pressure control valve 36. The pressure control valve 36 comprises a valve seat 38 preferably in a plate form, a valve body 40 disposed on the valve seat 38 and a valve rod 42. The valve seat 38 is disposed on a bottom 44 of the upper stepped recess 26 so that a control chamber 46 is defined between the valve seat 38 and an upper end 29 of the plunger 28.

The valve body 40 is retained axially, in fluid-tight manner and in a fixed position, against the valve seat 38 by a nut 48 screwed to an inner surface 50 of the upper stepped recess 26, and comprises an axial through bore 52. The valve rod 42 is housed in the axial through bore 52 and may slide axially in the axial through bore 52 in a substantially fluid-tight manner with an inner surface of the axial through bore 52. The valve rod 42 comprises a cylindrical stem 54 and a head 56 formed at the lower end of the stem 54. The head 56 has a diameter larger than that of the stem 54. The valve rod 42 also comprises an annular groove 58 on its partial outer surface to form an annular chamber 59 between the outer surface of the valve rod 42 and the inner surface of the axial through bore 52. Preferably, the annular groove 58 is formed on the outer surface of the stem 54. A central passage 60 extends through the stem 54 and the head 56. The valve body 40 also comprises a concave cavity 62 formed in a lower end of the axial through bore 52 to receive the head 56 of the valve rod 42. A space 61 is defined between a wall of the concave cavity 62 and an outer wall of the head 56 of the valve rod 42 when the head 56 of the valve rod 42 abuts against the valve seat 38. The head 56 of the valve rod 42 and the concave cavity 62 are shaped and dimensioned such that the head 56 of the valve rod 42 mates in fluid-tight manner with the wall of the concave cavity 62 to form a first fluid seal between the annular chamber 59 and the concave cavity 62 when the valve rod 42 moves axially and upward (as shown in FIG. 4) and the head 56 of the valve rod 42 spaces from the wall of the concave cavity 62 to communicate the annular chamber 59 with the concave cavity 62 when the valve rod 42 moves axially and downward to abut against the valve seat 38 (as shown in FIG. 2). Preferably, the head 56 of the valve rod 42 and the concave cavity 62 are in frustoconic shape.

The fuel injection device 1 also comprises a lifting mechanism 63 for lifting axially and upward the valve rod 42 of the pressure control valve 36. The lifting mechanism 63 comprise an armature 64 fixed to the stem 54 of the valve rod 42 and an electromagnetic coil 66. The armature 64 is supported by a spring 68 disposed between the armature 64 and the nut 48. The electromagnetic coil 66 is disposed with in a coil casing 67 above the armature 64. When the electromagnetic coil 66 is supplied with an electric current, an electromagnetic attraction force is produced to attract the armature 64 upward so that the valve rod 42 of the pressure control valve 36 slides axially and upward in the axial through bore 52. Although the lifting mechanism 63 is shown as an electromagnetic lifting mechanism, it should be understood that it may be a piezoelectric lifting mechanism, a hydraulic lifting mechanism and the like.

The valve rod 42 of the pressure control valve 36 extends partially into a central channel 69 of the coil casing 67. A spring 70 is disposed at an upper end of the valve rod 42 and within the coil casing 67 and is hold in position by the end body 16 of the fuel injection device 1. The spring 70 always tends to push the valve rod 42 toward valve seat 38 so that the head 56 of the valve rod 42 abuts in a fluid-tight manner against the valve seat 38 to form a second fluid seal between the central passage 60 of the valve rod 42 and the space 61 outside the head 56 of the valve rod 42. The central channel 69 connects to a backflow pipe of a low pressure circuit (not shown).

The fuel injection device 1 also comprises a fuel supply passage 72 formed in the housing 10 and connectable to a feeding pump (not shown). The fuel supply passage 72 is divided into a first branch passage 74 and a second branch passage 76. The first branch passage 74 leads into the pressure chamber 20 defined in the nozzle body 12 and the second branch passage 76 leads into the annular chamber 59 between the outer surface of the cylindrical stem 54 and the inner surface of the axial through bore 52. At least one through hole 78 is formed in the valve seat 38 to communicate with both the control chamber 46 and the space 61 defined between the wall of the concave cavity 62 and the outer wall of the head 56 of the valve rod 42.

The fuel injection device 1 shown in the drawings functions as follows: In the outset state, with the electromagnetic coil 66 currentless, no electromagnetic attraction force applies to the armature 64. Under the action of the thrust exerted by the spring 70 at the upper end of the valve rod 42, the valve rod 42 slides axially and downward in the axial through bore 52 in a substantially fluid-tight manner so that the head 56 of the valve rod 42 abuts in a fluid-tight manner against the valve seat 38 to form the second fluid seal between the central passage 60 of the valve rod 42 and the space 61 outside the head 56 of the valve rod 42. At this time, the head 56 of the valve rod 42 spaces from the wall of the concave cavity 62. The control chamber 46 communicates, via the through hole 78, the space 61, the annular chamber 59 and the second branch passage 76, with the fuel supply passage 72, as shown in Fig 2. The high pressure thus prevails in the control chamber 46. In such state, the high pressure also prevails in the pressure chamber 20. Since the diameter of the upper end of the plunger 28 adjacent the control chamber 46 is larger than that of the nozzle needle 18, a downward force difference is produced and exerted on the plunger 28. As a result of this force difference and of the spring 30, the plunger 28 pushes the nozzle needle 18 downward to press against the valve seat of the nozzle body 12. Accordingly, fuel is unable to exit through the fuel outlet openings 22, as shown Fig 1.

When the electric current is now supplied to the electromagnetic coil 66, the electromagnetic attraction force is produced to attract the armature 64 upward so that, counter to the force of the spring 70, the valve rod 42 of the pressure control valve 36 together with the armature 64 slides axially and upward in the axial through bore 52. As a result, the head 56 of the valve rod 42 mates in fluid-tight manner with the wall of the concave cavity 62 to form the first fluid seal between the annular chamber 59 and the concave cavity 62. At the same time, since the head 56 of the valve rod 42 moves away from the valve seat 38, the control chamber 46 communicates, via the through hole 78 and the concave cavity 62, with the central passage 60 of the valve rod 42, as shown in Fig 4. Since the central channel 69 connects to the backflow pipe of the low pressure circuit, the pressure in the control chamber 46 drops. However, at this time, the high pressure still prevails in the pressure chamber 20. Under the action of the high pressure in the pressure chamber 20, the nozzle needle 18 move axially and upward against the force of the spring 30 and the hydraulic force caused by the pressure in the control chamber 46 to lift from the valve seat of the nozzle body 12. Thus, the pressurized fuel from the fuel supply passage 72 is injected into a combustion chamber (not shown), via the first branch passage 74, the pressure chamber 20 and the fuel outlet openings 22, as shown Fig 3.

To terminate an injection, the electric current supplied to the electromagnetic coil 66 is cut off. No electromagnetic attraction force applies to the armature 64. Under the action of the thrust exerted the spring 70 at the upper end of the valve rod 42, the fuel injection device 1 goes back to a closed state as shown in Fig 1.

According to the fuel injection device of the present invention, the pressurized fuel from the fuel supply passage is supplied to the annular chamber between the outer surface of the cylindrical stem and the inner surface of the axial through bore without going directly into the control chamber, and the pressure control valve may provide the second fluid seal between the central passage of the valve rod and the space outside the head of the valve rod when the valve rod moves axially and downward and the first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward. So, the calibrated section hole or the throttle restriction is unnecessary. Further, the pressure circuits in the fuel injection device of the present invention are relatively simple. The fuel injection device of the present invention thus is simple in structure, is capable of being manufactured easily and in a low-cost manner and improves the reliability in operation.

Although the preferred embodiments of the invention were described in detail taken in conjunction of the accompanying drawings in a non-limiting sense, it should be understood that various changes and modifications could be made without departing from the scope defined by accompanying claims of the invention.

Claims

What is claimed is:

1. A pressure control valve for a fuel injection device, comprising: a valve seat; a valve body disposed on the valve seat, the valve body comprising an axial through bore and a concave cavity formed in a lower end of the axial through bore; and a valve rod housed in the axial through bore and being slidable axially in the axial through bore in a substantially fluid-tight manner, an annular groove being arranged on an outer surface of the valve rod to form an annular chamber between the outer surface of the valve rod and the inner surface of the axial through bore, the valve rod comprising a cylindrical stem, a head formed at a lower end of the stem and a central passage extending through the stem and the head, the head being received in the concave cavity, and the valve body also comprising a branch passage leading into the annular chamber; wherein the head of the valve rod and the concave cavity are shaped and dimensioned such that the head of the valve rod mates in fluid- tight manner with the wall of the concave cavity to form a first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward, and the head of the valve rod spaces from the wall of the concave cavity to communicate the annular chamber with a space defined between the wall of the concave cavity and the outer wall of the head and to form a second fluid seal between the central passage of the valve rod and the space when the valve rod moves axially and downward to abut in fluid-tight manner against the valve seat; and at least one through hole is formed in the valve seat to communicate with the space defined between the wall of the concave cavity and the outer wall of the head.

2. The pressure control valve as claimed in claim 1, wherein the head of the valve rod has a diameter larger than that of the stem of the valve rod.

3. The pressure control valve as claimed in claim 1, wherein the annular groove is disposed on an outer surface of the stem of the valve rod.

4. The pressure control valve as claimed in claim 1, wherein the head of the valve rod and the concave cavity are in frustoconic shape.

5. A fuel injection device for an internal combustion engine, comprising: a housing having a pressure chamber and fuel outlet openings formed therein, the pressure chamber communicating with a fuel supply passage; a needle-like valve element which is slidable axially within the housing so that the fuel outlet openings is disconnected from the pressure chamber or made to communicate with the pressure chamber; a pressure control valve disposed within the housing, the pressure control valve comprising: a valve seat disposed above the needle-like valve element so that a control chamber is defined between the valve seat and an upper end of the needle-like valve element; a valve body disposed on the valve seat, the valve body comprising an axial through bore and a concave cavity formed in a lower end of the axial through bore; and a valve rod housed in the axial through bore and being slidable axially in the axial through bore in a substantially fluid-tight manner, an annular groove being arranged on an outer surface of the valve rod to form an annular chamber between the outer surface of the valve rod and the inner surface of the axial through bore, the valve rod comprising a cylindrical stem, a head formed at a lower end of the stem and a central passage extending through the stem and the head, the head being received in the concave cavity, and the valve body also comprising a branch passage communicating the annular chamber and the fuel supply passage; wherein the head of the valve rod and the concave cavity are shaped and dimensioned such that the head of the valve rod mates in fluid-tight manner with the wall of the concave cavity to form a first fluid seal between the annular chamber and the concave cavity when the valve rod moves axially and upward, and the head of the valve rod spaces from the wall of the concave cavity to communicate the annular chamber with a space defined between the wall of the concave cavity and the outer wall of the head and to form a second fluid seal between the central passage of the valve rod and the space when the valve rod moves axially and downward to abut in fluid-tight manner against the valve seat; and at least one through hole is formed in the valve seat to communicate the control chamber with the space defined between the wall of the concave cavity and the outer wall of the head; a lifting mechanism for lifting axially and upward the valve rod of the pressure control valve; and a spring disposed at an upper end of the valve rod, the spring pushing the valve rod toward valve seat so that the head of the valve rod abuts in a fluid-tight manner against the valve seat.

6. The fuel injection device as claimed in claim 5, wherein the head of the valve rod has a diameter larger than that of the stem of the valve rod.

7. The fuel injection device as claimed in claim 5, wherein the annular groove is disposed on an outer surface of the stem of the valve rod.

8. The fuel injection device as claimed in claim 5, wherein the head of the valve rod and the concave cavity are in frustoconic shape.

9. The fuel injection device as claimed in claim 5, further comprising a spring to push the needle-like valve element to close the fuel outlet openings.

10. The fuel injection device as claimed in claim 5, wherein the lifting mechanism is an electromagnetic lifting mechanism comprising an armature fixed to the stem of the valve rod and an electromagnetic coil disposed above the armature.