EP3303817B1 - Common-rail-injector - Google Patents

Description

State of the art

The invention relates to a common rail injector according to the preamble of claim 1.

Such a common rail injector is from the DE 199 36 668 A1 ( Fig. 7 ) known to the applicant. In the known common rail injector, the high-pressure chamber is essentially formed within a nozzle body of the injector housing. In the area of the nozzle body, a control chamber sleeve is also arranged, in which the end area of a nozzle needle opposite an injection opening is inserted. The nozzle needle is acted upon by force in its closing direction by means of a closing or return spring. For this purpose, the closing spring is supported on the one hand against a support ring resting on a radially circumferential collar of the control chamber sleeve and on the other hand against a sleeve-shaped element which radially surrounds the nozzle needle. The sleeve-shaped element rests against a diameter step of the nozzle needle with an axial interposition of a support ring. To limit the maximum stroke of the nozzle needle during its opening movement, an axial gap is formed between the facing end faces of the control chamber sleeve and the element, the size of which the maximum stroke depends on. When the maximum stroke is reached, the element surrounding the nozzle needle radially rests with its end face on the end face of the control chamber sleeve.

In addition, common rail injectors with nozzle needles are known from the prior art, which in contrast to that in FIG DE 199 36 668 A1 disclosed nozzle needle extend axially over several subregions of the injector housing. An axial stroke stop by means of separate or specially designed components as in the prior art mentioned at the beginning is not provided in common rail injectors of this type. Rather, the maximum stroke in such a common rail injector is limited in that the end face of the nozzle needle facing away from the injection opening rests axially against a surface of the control chamber that delimits the control chamber on the side facing away from the nozzle needle. Further common rail injectors are known from JP 2006 274942 A , DE 10 2006 050065 A1 , DE 10 2011 078429 A1 and US 2010/019066 A1 .

Disclosure of the invention

Based on the prior art presented, the invention is based on the object of developing a common rail injector according to the preamble of claim 1 in such a way that the maximum achievable opening stroke of the nozzle needle can be set even with relatively long nozzle needles, with one at the same time advantageous assembly of the nozzle needle and the components of the stroke limiting device that interact directly with the nozzle needle are to be made possible. Furthermore, a local separation of a control chamber and the setting of the maximum achievable opening stroke of the nozzle needle should be achieved in order to be able to optimally design the corresponding components.

This object is achieved according to the invention in a common rail injector with the features of claim 1 in that the nozzle needle is a second element of the device for setting the maximum stroke of the nozzle needle, which surrounds the nozzle needle radially and axially on the side facing away from the first element is arranged stationary in the injector housing, axially completely penetrated and the end region of the nozzle needle dipping into the control chamber is arranged axially spaced from the second element. The high-pressure chamber in the nozzle body and in the further housing element is formed by a bore section on each side facing one another, the bore section formed in the further housing element for forming the stop surface for the second element having a smaller diameter than the bore section formed in the nozzle body, and the second Element has at least one passage for fuel between the two bore sections. This passage is of particular importance because it ensures that even when the nozzle needle is fully open, in which the second element is on the face of the further housing elements is applied, an inflow of fuel into the area of the at least one injection opening is made possible.

In other words, this means that the device for limiting the maximum opening stroke of the nozzle needle is arranged or formed separately from the control chamber or the second element forming the control chamber. This makes it possible, especially when using relatively long nozzle needles, to arrange the control chamber on the side of the nozzle needle facing away from the at least one injection opening in the injector housing, and the device for limiting the maximum opening stroke of the nozzle needle relatively close to the at least one injection opening in the injector housing. Such a functional separation of the assemblies also enables, in particular, an advantageous assembly of the components of the common rail injector.

Advantageous further developments of the common rail injector according to the invention are listed in the subclaims.

In an advantageous constructive implementation of the general inventive concept, it is provided that the device for setting the maximum stroke of the nozzle needle is arranged in the area of a nozzle body to which at least one further housing element is connected in the axial direction on the side facing away from the at least one injection opening, and that the control chamber is arranged in the area of the further housing element.

To form an axial stop for the second element of the device to limit the maximum opening stroke of the nozzle needle, it is preferably provided that the further housing element with an end face facing the nozzle body forms an axial stop surface for the second element of the device. Such a design has the advantage that a stop for the second element can be formed without additional components, since this is formed by the end face or end face of the further housing element facing the second element.

In order, on the one hand, to achieve the highest possible flow cross-section in the direction of the at least one injection opening through the second element, and at the same time to be able to design the second element in a particularly simple and rigid manner, it is provided that the at least one passage in the second element as over a partial area the axial extent of the second element extending longitudinal slot is formed, which extends from the end face of the second element facing away from the nozzle body.

To limit the wear between the two elements of the device for limiting the maximum opening stroke and for setting the maximum opening stroke, it is provided that the facing ends of the two elements are in contact with the maximum stroke of the nozzle needle, and that the maximum opening stroke of the nozzle needle through the Size of an axial gap formed between the end faces of the two elements is defined.

As explained in the prior art section, a return or closing spring is used to apply force to the nozzle needle in its closed position, on the one hand, to move the nozzle needle into its closed position during operation of the common rail injector when the control is interrupted, and on the other hand, to avoid undesired injection of fuel into the combustion chamber of an internal combustion engine. For this purpose, the spring stiffness or the characteristics of the closing spring must be precisely matched. In a further embodiment of the invention, it can be provided that the maximum opening stroke of the nozzle needle is limited by the end region of the nozzle needle that plunges into the control chamber, and that at the maximum opening stroke of the nozzle needle the two elements are arranged at a distance from one another, forming an axial gap formed between the two elements are. The two elements thus serve to adjust or precisely position the closing spring in relation to the nozzle needle, and not to limit the maximum opening stroke of the nozzle needle.

In a further structural embodiment of the fuel injector, it can be provided that the nozzle needle has a radially circumferential seat for the first element on which the first element rests axially so that the second element with axial interposition of the return spring connects to the first element that the movement of the second element is limited by a nozzle module, the nozzle needle being part of the nozzle module, and that the nozzle module forms a preassembled assembly that can be inserted into the injector housing.

Finally, a further structurally preferred embodiment provides that the high-pressure chamber is hydraulically connected to an inlet channel for fuel under high pressure, and that the inlet channel opens radially into the high-pressure chamber in an axial area between the at least one injection opening and the control chamber. In particular, it can be provided that the opening area of the inlet channel opens into the high-pressure chamber approximately in the middle between the at least one injection opening and the control chamber. Such an arrangement of the inlet channel to the high-pressure chamber enables an optimized supply of both the control chamber and the area from which fuel flows through the at least one injection opening into the combustion chamber of the internal combustion engine.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and with reference to the drawing.

Fig. 1

einen Längsschnitt durch einen erfindungsgemäßen Common-Rail-Injektor,

Fig. 2

einen Teilbereich des Common-Rail-Injektors gemäß der Fig. 1 im Bereich einer Einrichtung zur Begrenzung des maximalen Öffnungshubs seiner Düsennadel,

Fig. 3

einen Einstellring in perspektivischer Ansicht,

Fig. 4

eine perspektivische Ansicht einer Anschlaghülse,

Fig. 5

eine mit dem Einstellring und der Anschlaghülse versehene Düsennadel in Seitenansicht,

Fig. 6

einen gegenüber der Fig. 2 modifizierten Common-Rail-Injektor, ebenfalls im Längsschnitt,

Fig. 7

einen gegenüber den Fig. 1 bis 4 modifizierten Common-Rail-Injektor, im Längsschnitt,

Fig. 8

einen bei dem Common-Rail-Injektor gemäß der Fig. 7 verwendeten Einstellring in perspektivischer Ansicht und

Fig. 9

einen bei dem Common-Rail-Injektor gemäß der Fig. 7 verwendeten Anschlagring, ebenfalls in perspektivischer Ansicht.

This shows in:

Fig. 1

a longitudinal section through a common rail injector according to the invention,

Fig. 2

a portion of the common rail injector according to FIG Fig. 1 in the area of a device for limiting the maximum opening stroke of its nozzle needle,

Fig. 3

an adjustment ring in perspective view,

Fig. 4

a perspective view of a stop sleeve,

Fig. 5

a nozzle needle provided with the setting ring and the stop sleeve in side view,

Fig. 6

one opposite the Fig. 2 modified common rail injector, also in longitudinal section,

Fig. 7

one opposite the Figs. 1 to 4 modified common rail injector, in longitudinal section,

Fig. 8

one in the common rail injector according to FIG Fig. 7 used setting ring in perspective view and

Fig. 9

one in the common rail injector according to FIG Fig. 7 used stop ring, also in perspective view.

The same elements or elements with the same function are provided with the same reference numbers in the figures.

The Indian Fig. 1 The common rail injector 10 shown is used to inject fuel into the combustion chamber, not shown, of an internal combustion engine, in particular a compression-ignition internal combustion engine. The injector 10 has an injector housing 11 consisting of several parts. In the exemplary embodiment shown, the injector housing 11 essentially comprises two parts, a nozzle body 12 and a housing element 13 connected to the nozzle body 12 in the axial direction, which in practice usually consists of several parts, also connected to one another and connected in the axial direction. The pressure-tight connection between the nozzle body 12 and the housing 13 takes place in a manner known per se by means of a nozzle clamping nut 14. On the side facing the combustion chamber of the internal combustion engine, the nozzle body 12 has at least one injection opening 15 for injecting fuel. A high-pressure chamber 18 is formed within the injector housing 11, which is essentially formed by a plurality of bore sections with different diameters, formed in the nozzle body 12, and a plurality of bore sections, also with different diameters, formed in the housing element 13.

The high-pressure chamber 18 can be supplied with fuel which is under system pressure via an inlet channel 19. In the exemplary embodiment shown, the inlet channel 19 opens approximately in a central region of the high-pressure chamber 18 (based on the axial extent of the injector 10), whereby it is radial, i.e. perpendicular to a longitudinal axis 21 of the injector 10, in which the high pressure chamber 18 opens. On the side of the injector housing 11 opposite the inlet channel 19, an outlet channel 22 is formed, which serves to discharge fuel located in a low-pressure region 42 of the injector 10.

Inside the injector housing 11, a nozzle needle 25 is arranged in the longitudinal axis 21 so that it can move in the direction of the double arrow 26. In the in the Fig. 1 In the depicted, lowered position of the nozzle needle 25, the at least one injection opening 15 formed in the injector housing 11 or the nozzle body 12 is at least indirectly closed in order to prevent fuel from being injected into the combustion chamber of the internal combustion engine. For this purpose, a sealing seat is formed between the end region 27 of the nozzle needle 25 facing the at least one injection opening 15 and the inside of the nozzle body 12. In contrast, when the nozzle needle 25 is lifted from the sealing seat, fuel can flow out of the high-pressure chamber 18 through the at least one injection opening 15 into the combustion chamber of the internal combustion engine in a manner known per se.

The nozzle needle 25 is part of one in the Fig. 5 The nozzle module 30, viewed in the axial direction, comprises, in addition to the nozzle needle 25, a pin-shaped center piece 31 and a likewise pin-shaped valve piston 32. The nozzle needle 25, the center piece 31 and valve piston 32 are welded together in the transverse direction, in particular by laser welds. In the area of the nozzle needle 25, the nozzle module 30 also has a stop sleeve 33 that forms a first element of a device 50 for limiting the maximum opening stroke of the nozzle needle 25, a return spring 34 designed as a compression spring, and an adjusting ring 35. The adjusting ring 35 forms a second element of the device 50 for limiting the maximum opening stroke of the nozzle needle 25 and is completely penetrated or penetrated by the nozzle needle 25 in the axial direction. The stop sleeve 33, the return spring 34 and the adjusting ring 35 are attached the nozzle needle 25 is mounted before the nozzle needle 25 is welded to the center piece 31. Due to the different diameters of the nozzle needle 25 and the center piece 31, the stop sleeve 33, the return spring 34 and the setting ring 35 are axially captive to the named components or the nozzle module 30 after the nozzle needle 25 is welded to the center piece 31, whereby the nozzle module 30 represents a pre-assemblable unit for the injector 10.

A control chamber sleeve 36 is arranged inside the injector housing 11 on the side of the nozzle module 30 facing away from the at least one injection opening 15. The control chamber sleeve 36 has, on the side facing the valve piston 32, a blind hole 37 into which the valve piston 32 of the nozzle module 30 dips with its end region 44. In particular, the end region 44 is axially spaced from the device 50 or the setting ring 35. The valve piston 32 delimits a control chamber 38 within the blind hole 37, which is hydraulically connected to the high pressure chamber 18 via an inlet bore 39. The control chamber 38 can be hydraulically relieved of pressure into the low-pressure region 42 of the injector 10, which in turn is connected to the discharge channel 22, via a through-hole 41 formed in the control chamber sleeve 36.

The through-hole 41 can be closed on the side facing away from the valve piston 32 by means of a valve member 43, which is spherical in the exemplary embodiment. The actuation of the valve member 43 is carried out by way of example, and not by way of limitation, via a magnetic actuator 45 in a manner known per se, in such a way that when the magnetic actuator 45 is energized, the valve member 43 lifts off the through-bore 41 to prevent fuel from flowing out of the control chamber 38 to allow in the low pressure region 42 of the injector 10. The fuel flowing out of the control chamber 38 also causes the nozzle module 30 or the nozzle needle 25 to be actuated in a known manner such that the nozzle needle 25 lifts from its sealing seat to release the at least one injection opening 15.

In the Fig. 2 it is shown that the stop sleeve 33, the return spring 34 and the setting ring 35 are arranged within a bore section 46 of the nozzle body 12. At the nozzle body 12 closes in axial direction the housing element 13, whereby a bore section 48 opening into the end face 47 of the housing element 13 has a smaller diameter than the bore section 46 in the area of the setting ring 35 or the bore section 46. This forms the end face 47 for the end face of the setting ring facing it 35 from an axial stop.

How particularly with the Fig. 3 As can be seen, the setting ring 35 has, for example, three longitudinal slots 49 which are arranged in equal angular sections relative to one another and each form a passage for fuel from the bore section 48 into the bore section 46. The longitudinal slots 49, each rectangular in a side view in the exemplary embodiment, extend over a partial area of the length L of the adjusting ring 35 and start from the end face of the adjusting ring 35 facing the housing element 13.

The stop sleeve 33 which radially surrounds the nozzle needle 25 has a radially circumferential collar 51 on the side facing away from the setting ring 35, which collar rests axially on a seat or a shoulder 52 of the nozzle needle 25. The return spring 34 is supported between the collar 51 and the end face of the setting ring 35 facing the return spring 34. The return spring 34 acts on the nozzle needle 25 or the nozzle module 33 with a spring force such that the nozzle needle 25 is pressed in the direction of the at least one injection opening 15 or in the direction of the sealing seat. In particular, the restoring spring 34 ensures that when the magnetic actuator 45 is de-energized, the nozzle needle 25 always forms the sealing seat in order to prevent fuel from injecting into the combustion chamber of the internal combustion engine.

An axial gap 55 is formed between the end face 53 of the stop sleeve 33 facing away from the collar 51 and the end face 54 of the adjusting ring 35 facing the end face 53. The size of the axial gap 55 is set by varying the length I of the stop sleeve 33. In particular, the maximum stroke of the nozzle needle 25 or of the nozzle module 30 in the opening direction is limited by the size of the axial gap 55. The end face 54 of the setting ring 35 thus forms a stop for the stop sleeve 33 in the opening direction of the nozzle needle 25.

When the magnetic actuator 45 is energized and the associated pressure relief of the control chamber 38 is applied, the nozzle needle 25 moves against the spring force of the return spring 34 in the opening direction until the stop sleeve 33 rests axially on the setting ring 35, i.e. the axial gap 55 is zero. In this position, the end face of the valve piston 32 facing the base of the blind hole 37 of the control chamber 38 is still spaced from the base of the blind hole 37.

Alternatively, and not according to the invention, it can correspond to the representation of Fig. 6 It can also be provided that the length I of the stop sleeve 33 is selected to be so small that the maximum opening stroke of the nozzle needle 25 or the nozzle module 30 occurs when the valve piston 32 rests against the base of the blind hole 37 of the control chamber 38. In this case, even with a maximum opening stroke of the nozzle needle 35, as shown in FIG Fig. 6 is shown, the stop sleeve 33 still axially spaced from the setting ring 35, that is, that an axial gap 55 is always formed greater than zero. In this configuration, the dimensions of the setting ring 35 and the stop sleeve 33 define or limit the installation space of the return spring 34 in order to set or define the required return characteristic or return force of the return spring 34.

In the Figures 7 to 9 is a part of the opposite Figs. 1 to 3 modified injector 10a shown. In addition to the stop sleeve 33, the injector 10a has a sleeve-shaped adjusting ring 35a with a constant diameter with a plurality of through bores 57 for the fuel formed on its wall in the radial direction. The setting ring 35a cooperates with a stop ring 58 which has a centering section 59 projecting into the setting ring 35a. In addition, the adjusting ring 35a has flat, closed end faces. The setting of the maximum axial gap 55 can take place by varying the height of the setting ring 35a, the setting ring 35a being able to be connected to the nozzle module 30 later.

Claims (9)

1. Common-rail injector (10; 10a) having an injector housing (11) in which a nozzle needle (25), which is disposed so as to be able to perform reciprocating stroke movements in a high-pressure chamber (18) for releasing or blocking, respectively, at least one injection opening (15) that is configured in the injector housing (11), is disposed, wherein an end region of the nozzle needle (25) that faces away from the at least one injection opening (15) plunges into an element (36) in order for a control chamber (38) to be configured, and wherein the nozzle needle (25) interacts with an installation (50) for restricting the maximum opening stroke of the nozzle needle (25), wherein the installation (50) has a first, preferably sleeve-shaped, element (33) which, in axial terms, is preferably disposed so as to be locationally fixed on the nozzle needle (25) and which, by means of a restoring spring (34), is impinged with a force in the closing direction of the nozzle needle (25), and a second, preferably likewise sleeve-shaped, element (35; 35a) which radially encompasses the nozzle needle (25) and, in axial terms, is disposed so as to be locationally fixed on that side in the injector housing (11) that faces away from the first element (33),
   wherein the nozzle needle (25), in axial terms, completely penetrates the second element (35; 35a), and the end region (44) of the nozzle needle (25) that plunges into the control chamber (38) is disposed so as to be axially spaced apart from the second element (35; 35a), and
   characterized in that a further housing element (13), by way of an end face (47) that faces the nozzle body (12), configures an axial detent face for the second element (35; 35a) of the installation (50), and the high-pressure chamber (18) in the nozzle body (12) and in the further housing element (13) is formed on mutually facing sides of, in each case, one bore portion (46, 48), wherein the bore portion (48) configured in the further housing element (13) for configuring the detent face for the second element (35; 35a) has a smaller diameter than the bore portion (46) configured in the nozzle body (12), and in that the second element (35; 35a), between the two bore portions (46, 48), has at least one passage for fuel.
2. Common-rail injector according to Claim 1,
   characterized in that
   the installation (50) is disposed in the region of a nozzle body (12), said region on the side that faces away from the at least one injection opening (15) in the axial direction being adjoined by the further housing element (13), and in that the control chamber (38) is disposed in the region of the further housing element (13).
3. Common-rail injector according to Claim 1,
   characterized in that
   the at least one passage is configured as a longitudinal slot (49) which runs across a sub-region of the axial extent (L) of the second element (35), said sub-region emanating from the end side of the second element (35) that faces away from the nozzle body (12).
4. Common-rail injector according to Claim 1,
   characterized in that
   the at least one passage is configured as a through bore (57).
5. Common-rail injector according to one of Claims 1 to 4,
   characterized in that
   the mutually facing end sides (53, 54) of the two elements (33, 35) at the maximum stroke of the nozzle needle (25) bear on one another so as to restrict the opening stroke of the nozzle needle (25), and in that the maximum opening stroke of the nozzle needle (25) is defined by the size of an axial gap (55) that is configured between the end sides (53, 54) of the two elements (33, 35).
6. Common-rail injector according to one of Claims 1 to 4,
   characterized in that
   the mutually facing end sides (53, 54) of the two elements (33, 35a) at the maximum stroke of the nozzle needle (25) bear on one another, by way of the intervention of a detent ring (58), so as to restrict the opening stroke of the nozzle needle (25), and in that the maximum opening stroke of the nozzle needle (25) is defined by the size of an axial gap (55) that is configured between the one element (33) and the detent ring (58).
7. Common-rail injector according to one of Claims 1 to 6,
   characterized in that
   the setting of the maximum opening stroke of the nozzle needle (25) takes place by varying the length (1) of the first element (33) or of the second element (35a).
8. Common-rail injector according to one of Claims 1 to 5,
   characterized in that
   the nozzle needle (25) has a radially encircling seat (52) for the first element (33), the first element (33) bearing axially on said seat (52), in that the second element (35) adjoins the first element (33) by way of an axial intervention of the restoring spring (34), in that the movement of the second element (35) is restricted by a nozzle module (30), wherein the nozzle needle (25) is a component part of the nozzle module (30), and in that the nozzle module (30) configures a functional group which is able to be pre-assembled and inserted into the injector housing (11).
9. Common-rail injector according to one of Claims 1 to 8,
   characterized in that
   the high-pressure chamber (18) is hydraulically connected to an infeed duct (19) for pressurized fuel, and in that the infeed duct (19), in an axial region that lies between the at least one injection opening (15) and the control chamber (38), opens radially into the high-pressure chamber (18).

Images