Nozzle assembly for a fuel injector, and fuel injector

Abstract

A nozzle assembly for a fuel injector includes a nozzle needle (1), which is accommodated in a high-pressure bore (2) of a nozzle body (3) in such a way that the nozzle needle can be moved in a reciprocating manner in order to open and close at least one injection opening (4) and to which a spring force of a spring (5) is applied at least indirectly in a closing direction. The nozzle needle (1) is at least partially surrounded by a throttle bore body (7) in order to form at least one closing throttle (6). The throttle bore body (7) has a multi-part design and comprises at least two sleeves (7.1, 7.2), which are at least partially guided in each other.

Claims

1. A nozzle assembly for a fuel injector having a nozzle needle (1) which is received in a high pressure bore (2) of a nozzle body (3) such that the nozzle needle can perform stroke movements in order to open and close at least one injection opening (4) and is loaded in the closing direction at least indirectly by the spring force of a spring (5), the nozzle needle (1) being at least partially surrounded by a throttle bore body (7) in order to configure at least one closing throttle (6), characterized in that the throttle bore body (7) is configured in multiple pieces and comprises at least first and second sleeves (7.1, 7.2) which are at least partially guided into one another, and in that the second sleeve (7.2), which is arranged closer to the injection opening (4), is of substantially pot-shaped configuration and at least partially surrounds the first sleeve (7.1).

2. The nozzle assembly as claimed in claim 1, characterized in that the closing throttle (6) is configured in the second sleeve (7.2), which is arranged closer to the injection opening (4).

3. The nozzle assembly as claimed in claim 1, characterized in that the second sleeve (7.2), which is arranged closer to the injection opening (4), is supported in the axial direction on a shoulder (8) of the nozzle needle (1).

4. The nozzle assembly as claimed in claim 3, characterized in that the second sleeve (7.2) is loaded by the spring force of the spring (5) in a direction of the shoulder (8) of the nozzle needle (1).

5. The nozzle assembly as claimed in claim 1, characterized in that an annular space (9) is configured between the nozzle needle (1) and the first sleeve (7.1) which is arranged less closely to the injection opening (4).

6. The nozzle assembly as claimed in claim 1, characterized in that the first sleeve (7.1) has a collar section (10) for housing-side support.

7. The nozzle assembly as claimed in claim 1, characterized in that the spring (5) is arranged so as to lie radially on the outside in relation to at least one of the first and second sleeves (7.1).

8. The nozzle assembly as claimed in claim 1, characterized in that the nozzle needle (1) is of stepped configuration.

9. The nozzle assembly as claimed in claim 1, characterized in that the sleeves (7.1, 7.2) interact so as to form a stroke stop (13).

10. A fuel injector for injecting fuel into the combustion chamber of an internal combustion engine, the fuel injector comprising a nozzle assembly as claimed in claim 1, the throttle bore body (7) being supported via one of the sleeves (7.1, 7.2) on a body component (11) of the fuel injector.

11. The nozzle assembly as claimed in claim 1, characterized in that the closing throttle (6) is configured in the second sleeve (7.2), which is arranged closer to the injection opening (4), as an axially or obliquely running bore.

12. The nozzle assembly as claimed in claim 1, characterized in that the second sleeve (7.2), which is arranged closer to the injection opening (4), is supported in the axial direction on an annular shoulder (8) of the nozzle needle (1).

13. The nozzle assembly as claimed in claim 12, characterized in that the second sleeve (7.2) is loaded by the spring force of the spring (5) in a direction of the annular shoulder (8) of the nozzle needle (1), the spring (5) being supported on an annular end face (14) of the sleeve (7.2).

14. The nozzle assembly as claimed in claim 1, characterized in that the first sleeve (7.1) has a radially outwardly extending collar section (10) for housing-side support, the first sleeve (7.1) being mounted in the high pressure bore (2) in a radially floating manner.

15. The nozzle assembly as claimed in claim 1, characterized in that the nozzle needle (1) is of stepped configuration, in order to configure an annular shoulder (8), a section (12) of the nozzle needle (1) which is surrounded by the throttle bore body (7) being configured with a reduced external diameter.

16. A fuel injector for injecting fuel into the combustion chamber of an internal combustion engine, the fuel injector comprising a nozzle assembly as claimed in claim 1, the throttle bore body (7) being supported via one of the sleeves (7.1, 7.2) on a plate-shaped body component (11) of the fuel injector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One preferred embodiment of the invention will be explained in greater detail in the following text using the appended drawing.

(2) FIG. 1 shows a diagrammatic longitudinal section through a nozzle assembly according to the invention.

DETAILED DESCRIPTION

(3) The nozzle assembly which is shown comprises a nozzle needle 1 which is received in a high pressure bore 2 of a nozzle body 3 such that it can perform stroke movements. At least one injection opening 4 can be opened and closed by the stroke movement of the nozzle needle 1. When the injection opening 4 is open, highly pressurized fuel is injected into a combustion chamber of an internal combustion engine (not shown).

(4) The nozzle needle 1 is loaded in the closing direction by the spring force of a spring 5 which to this end is supported on one side on a collar section 10 of a first sleeve 7.1 and on the other side on an annular end face 14 of a pot-shaped second sleeve 7.2 of a throttle bore body 7 which is configured in multiple pieces. A throttle bore which runs obliquely through a bottom region 15 of the sleeve 7.2 is configured in the pot-shaped second sleeve 7.2 as a closing throttle 6 which is part of the flow path of the fuel to be injected. The closing throttle 6 brings it about that the hydraulic pressure p1 in a first part region 2.1 of the high pressure bore 2 is greater than the hydraulic pressure p2 in a second part region 2.2 of the high pressure bore 2. The pressure difference in turn leads to a hydraulic force which acts in the closing direction and loads the pot-shaped sleeve 7.2 and, indirectly via the pot-shaped sleeve 7.2, the nozzle needle 1. Together with the spring force of the spring 5, the hydraulic force brings about rapid needle closure.

(5) To this end, the pot-shaped sleeve 7.2 is supported on an annular shoulder 8 of the nozzle needle 1 and is prestressed axially in the direction of the shoulder 8 by means of the spring force of the spring 5. The spring force of the spring 5 and the hydraulic force which acts in the closing direction bring about a sealing force which largely prevents a leakage in the contact region 16 of the sleeve 7.2 with the nozzle needle 1.

(6) The pot-shaped sleeve 7.2 surrounds the further sleeve 7.1 of the multiple-piece throttle bore body 7 in regions, with the result that said further sleeve 7.1 is guided via the pot-shaped sleeve 7.2. The guide region 17 represents a further contact region which is as a rule afflicted by leakage. In the present case, however, the pressure conditions in the part regions 2.1, 2.2 of the high pressure bore 2 counteract a leakage. This is because the pressure p1 prevails on the inner circumferential side on the sleeve 7.1 which is flowed through by the fuel to be injected, and the pressure p2 prevails on the outer circumferential side on the sleeve 7.2. The wall of the sleeve 7.1 is pressed against the wall of the sleeve 7.2 on account of the pressure difference. In addition, the sleeve 7.1 can experience radial widening in a manner which is dependent on the pressure p1. In order that the sleeve 7.1 is flowed through by the fuel to be injected, an annular space 9 which is part of the flow path of the fuel to be injected is configured between the sleeve 7.1 and the nozzle needle 1.

(7) The contact region 18 of the sleeve 7.1 on a plate-shaped body component 11 of the fuel injector represents a further sealing location which is in principle afflicted by leakage. Since, however, the spring 5 is supported on the collar section 10 of the sleeve 7.1 in the present case, the spring force of the spring 5 presses the sleeve 7.1 against the body component 11. Moreover, the pressure p1 which brings about an additional hydraulic force in the direction of the body component 11 prevails on that end face of the sleeve 7.1 which faces away from the contact region 18. In the present case, the end face of the sleeve 7.1 at the same time forms a stroke stop 13 if, during opening of the needle, the sleeve 7.2 passes into contact via its bottom region 15 with that end face of the sleeve 7.1 which serves as a stroke stop 13.

(8) The nozzle needle 1 of the nozzle assembly which is shown is of stepped configuration and has a section 12 with a reduced external diameter for receiving the multiple-piece throttle bore body 7 and for configuring the annular shoulder 8, on which the pot-shaped sleeve 7.2 of the throttle bore body 7 is supported. The fuel to be injected flows past said section 12 of the nozzle needle 1 in the direction of the closing throttle 6, and passes via the closing throttle 6 into the second part region 2.2 of the high pressure bore 2. The flow direction of the fuel is indicated by means of the arrows 19.