EP2294309A1

EP2294309A1 - Fuel injector

Info

Publication number: EP2294309A1
Application number: EP09765667A
Authority: EP
Inventors: Matthias Burger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-06-19
Filing date: 2009-04-22
Publication date: 2011-03-16
Anticipated expiration: 2029-04-22
Also published as: RU2541484C2; RU2011101635A; CN102066741B; CN102066741A; BRPI0914857A2; EP2294309B1; WO2009153087A1; DE102008002527A1

Abstract

The invention relates to a fuel injector, in particular common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, having a fuel return port (10) and having a single-part or multi-part injection valve element (13) which can be adjusted between an open position and a closed position and which is arranged at least in sections in a high-pressure chamber (8) which is provided in an injector body (19). According to the invention, an annular chamber (42) is arranged radially between the high-pressure chamber (8) and the injector body (19), in which annular chamber (42), during the operation of the fuel injector (1), the fuel pressure is at least intermittently lower than the fuel pressure in the high-pressure chamber (8) and higher than the fuel pressure in the fuel return port (10).

Description

description

title

Fuel injector

State of the art

The invention relates to a fuel injector, in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1.

Compliance with emission limits has the highest priority in the development of internal combustion engines. Especially the common-rail injection system has made a decisive contribution to the reduction of pollutants. The advantage of the common-rail systems lies in their independence of the injection pressure of speed and load. For the compliance with future exhaust gas values, however, a significant increase of the injection pressure is necessary, especially for diesel engines.

Latest fuel injectors, such as the fuel injector described in DE 10 2007 021 330, are carried out low leakage, by dispensing with a low-pressure stage on the injection valve element. Components such as the injector body (housing part) are subjected to high pressure throughout the entire area, resulting in a completely new load case compared to earlier fuel injectors. Especially at rail pressures beyond 2000 bar, not only component intersections are problematic, but also material defects on at inconspicuous places, such as at a central bore in Injektorkör- per, lead to failures. These failures are statistically determined. Especially when a component is subjected to pressure over a large area, it becomes more and more probable that the component will fail under high pressure loads due to a structural defect. This type of failure is difficult to evaluate with conventional computational methods because failure does not occur at locations characterized by a peak stress, but rather at locations that are less critical in terms of stress distribution.

Therefore, for the production of fuel injectors for highest injection pressures of much greater than 2000 bar extremely expensive specialty materials must be used, whereby not only the material itself, but also its processing is associated with high costs.

DISCLOSURE OF THE INVENTION Technical Problem

The invention has for its object to propose a designed for highest injection pressures fuel injector. Preferably, this should be produced with conventional materials such as C45 steel.

Technical solution

This object is achieved with a fuel injector having the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention. The invention is based on the idea of arranging an annular space radially between the injector body (housing part) and a high-pressure chamber, preferably as an injector-side rail pressure accumulator (minirail), in which permanently or temporarily a lower fuel pressure than in the high-pressure space and a higher one Fuel pressure prevails as in the low pressure region of the fuel injector. In this way, it is achieved that only the differential pressure from the fuel pressure in the high-pressure chamber and the fuel pressure in the annular space acts on the annular space bounding the annular space radially inside. The load acting on the outer injector body is also reduced because it is only exposed to the fuel pressure in the annulus. By providing an annular space with lower hydraulic pressure than the high-pressure space, the pressure is thus gradually reduced from radially inward to radially outward, so that critical material loads can be avoided. In this way it is possible for injector bodies of fuel injectors designed for well over 2000 bar to be designed with conventional materials such as C45 steel, in particular if the fuel pressure in the annular space does not exceed about 1800 bar , If the pressure in the high-pressure chamber of the fuel injector is, for example, at most 2000 bar, it is generally sufficient if the pressure difference between the annular space and the high-pressure space is approximately 200 bar.

Particularly preferred is an embodiment of the fuel injector, wherein the pressure in the annular space during operation of the fuel injector is at least half as high as the pressure in the pressure chamber so as not to burden the separation between the annulus and the high-pressure chamber overly. Particularly preferred is an embodiment in which the fuel flowing in from the fuel supply connection from an external high-pressure fuel accumulator (rail) is conducted directly into the high-pressure space. For this purpose, a channel passing through the annular space in the radial direction is preferably provided, which is formed, for example, by the injector component which radially bounds the annular space.

The fuel injector is preferably a so-called low-leakage injector, preferably without a permanent, low-pressure stage which produces a hydraulic closing force acting on the one-part or multi-part injection valve element. Such fuel injectors are preferably equipped with a long injection valve element whose axial extent preferably corresponds to at least 50%, preferably at least 60% or 70%, of the axial extent of the entire fuel injector. In this case, an embodiment is particularly preferred in which the high-pressure space in which the injection valve element is accommodated extends in the axial direction as far as a nozzle hole arrangement, wherein the high-pressure space can be subdivided as required into two axially adjacent space sections, between which a closing throttle is arranged is to lower the fuel pressure in the region of an injection valve element tip slightly, for example by 100 to 200 bar, thereby to produce a hydraulic closing force component. Particularly preferred is an embodiment in which the high-pressure chamber extends in the axial direction into a nozzle body which is axially adjacent to the injector body, in which case an embodiment can also be realized in which the pressure-reduced annular space formed between the injector body and the high-pressure chamber extends in the axial direction as far as into the nozzle body.

To achieve the required pressure reduction in the annular space, it is conceivable to realize a series-connected throttle combination, which consists of at least one annular space inlet throttle and at least one annular space drain throttle, flowing over the annular space inlet throttle under high pressure, in particular at least approximately under rail pressure, standing fuel in the annulus can. Fuel can in turn flow out of the annular space in the direction of the low-pressure region of the fuel injector via the annular space drain throttle, wherein the flow cross-sections of the at least one annular space inlet throttle and the at least one annular space drain throttle are dimensioned such that the desired pressure difference between annular space and high-pressure space adjusts. This pressure reduction mechanism is comparable to known Steuerraumdruckab- reduction, as is known from servo-controlled fuel injectors. The essential difference is that the annular space pressure in comparison to the control chamber pressure has no influence on the injection behavior of the fuel injector, so that a lower accuracy requirement can be made in the production of the at least one annular space inlet throttle and the at least one annulus flow restrictor. It is particularly advantageous if the at least one annular space inlet throttle and / or the at least one annular space outlet throttle are structurally realized via a guide and / or a leak gap, as a result of which additional working steps for producing throttle bores can be saved. Of course it is also possible to perform at least one of the throttles as a throttle bore.

The at least one annulus drain can also be replaced or formed by a pressure relief valve to be explained later.

Particularly preferred is an embodiment of the fuel injector, is not lowered in the pressure in the annulus during the entire operating time against the pressure in the high pressure chamber, but only at times when the pressure in the high pressure chamber exceeds a critical limit. This is usually only the case when the internal combustion engine is operated under full load. In other words, an embodiment is preferred in which the pressure in the annular space is reduced or reduced in comparison with the pressure in the high-pressure space only when a minimum pressure, in particular of approximately 1800 bar, is exceeded.

This requirement can be realized constructively in that at least one pressure relief valve is provided in the fuel flow direction between the annulus and the low pressure region of the fuel injector, which is preferably designed as a check valve. In this case, an embodiment is particularly preferred in which the overpressure valve is designed in such a way that it acts as an annular space outlet throttle in the open state, so that the desired annular space pressure is set in a defined manner. Due to the only temporary opening of the pressure relief valve, the parasitic drainage quantity can be reduced to an absolute minimum.

Preferably, the overpressure valve comprises at least one spring which has an adjustable valve element spring-force-loaded. beat. The spring is particularly preferably a leaf spring and / or the valve element is a valve ball, in particular designed as a steel ball. Structurally elegant is an embodiment in which the valve element is pressed by the spring onto a valve seat which is formed on an injector component axially delimiting the low-pressure region. In this case, for example, the leaf spring can be clamped axially between a valve clamping screw for securing the injector component in the injector body and the injector component.

Alternatively, an embodiment can be realized in which the adjustable valve element of the pressure relief valve is formed by the low pressure region axially limiting injector component, said injector component is in this case by means of a spring, for example an expansion sleeve or a disc spring, against the injector body spring-loaded. It is particularly preferred if the fuel from the annulus with open pressure relief valve flows through an annular leakage gap in the low pressure region of the fuel injector, wherein the leakage gap, preferably axially, is formed between the Injektorbauteil and the injector, wherein to ensure sufficient tightness of the closed overpressure valve on the injector body and / or on the injector component, preferably at least one biting edge is formed.

Preferably, the spring of the pressure relief valve is arranged such that the bias of the spring and thus the maximum pressure of the annular space is adjustable by means of a valve clamping screw, the valve clamping screw preferably an axial securing for the low pressure region of the Fuel injector in the axial direction limiting injector component.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show in:

1 shows a first embodiment of a fuel injector with an annular space formed between a high-pressure chamber and an injector body in which the fuel pressure during operation of the fuel injector relative to the fuel pressure in

High pressure space is permanently reduced,

Fig. 2: an alternative, second embodiment of a fuel Inj ector arranged between the annulus and low pressure region of the fuel injector designed as a check valve overpressure valve, which has the task to reduce the fuel pressure in the annulus only when a minimum pressure is exceeded and

3 shows a further alternative, third exemplary embodiment of a fuel injector, in which the valve element of the pressure relief valve is formed by an injector component delimiting a control chamber. Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals are marked.

FIG. 1 shows a fuel injector 1 designed as a common-rail injector for injecting fuel into a combustion chamber, not shown, of an internal combustion engine of a motor vehicle. A high pressure pump 2 delivers fuel from a reservoir 3 into a high-pressure fuel accumulator 4 (rail). In this fuel, especially diesel or gasoline, under high pressure, of about 2500 bar in this embodiment, stored. To the high-pressure fuel accumulator 4, the fuel injector 1 is connected, among other injectors, not shown, via a supply line 5. This supply line 5 leads to a fuel supply connection 6 of the fuel Inj ector 1, which leads via a supply channel 7 to a central, serving as a minirail high pressure chamber 8. In this high-pressure chamber 8 there is essentially rail pressure of about 2500 bar. At a Injektordeckel 9, a fuel return port 10 is provided, to which a return line 11 is connected. By way of the fuel return connection 10 and the return line 11, a control quantity to be explained later and a leakage quantity of fuel can be discharged from a low-pressure region 12 of the fuel injector 1 to the reservoir 3, which is also at low pressure of approximately 1 to 10 bar.

Within the high-pressure chamber 8, an injection valve element 13 which is integral in the embodiment shown is one recorded axially adjustable. Alternatively, the injection valve element 13 is designed in several parts and consists for example of an upper control rod and a lower nozzle needle.

The injection valve element 13 is guided longitudinally displaceable in a guide bore 14 of a lower nozzle body 15 in the drawing plane. In this case, axial channels 16 are realized on the outer circumference of the injection valve element 13 in the region of its lower guide as polished sections, via which the fuel can flow in the axial direction down to a nozzle hole arrangement 17 when the injection valve element 13 is open. The nozzle body 15 is clamped by means of a union nut 18 with an injector body 19. In the exemplary embodiment shown, the injector body 19 forms the largest housing part of a housing 20.

The injection valve element 13 has at its tip 21 a closing surface 22 with which the injection valve element 13 can be brought into tight contact with an injection valve element seat 23 formed inside the nozzle body 15. When the injection valve element 13 abuts against its injection valve element seat 23, ie is in a closed position, the fuel outlet from the nozzle hole arrangement 17 is blocked. If, on the other hand, it is lifted off its injection valve element seat 23, fuel can flow from the high-pressure chamber 8 in the axial direction via the axial channels 16 into a lower nozzle space 24 designed as an annular space and from there past the injection valve element seat 23 to the nozzle hole arrangement 17 and there substantially under high pressure (FIG. Rail pressure) standing in the combustion chamber (not shown) to be injected. From an upper end face 25 of the injection valve element 13 and a control chamber portion 26 of an injector 27, a control chamber 28 is limited, which is supplied via an introduced into the injection valve element 13 inlet throttle 29 with fuel from the high-pressure chamber 8. The control chamber 28 is connected via a axially extending in the injector component 27 drain passage 30 with outlet throttle 31 with a valve chamber 32 of a control valve 33 (servo-valve). The valve chamber 32 is bounded radially on the outside by a sleeve-shaped control valve element 34. The sleeve-shaped control valve element 34 is substantially pressure-balanced in its closed position in the axial direction. The valve chamber 32 is bounded in the axial direction upward by a pressure pin 35, which is supported axially on Injektorde- disgust 9 and is formed as a component separate from the injector component 27. A co-operating with the sleeve-shaped control valve element 34 control valve seat 36 (here flat seat) is formed on the injector component 27.

The sleeve-shaped control valve element 34 is integrally formed with an anchor plate 37 which cooperates with an electromagnetic actuator 38. If this is energized, lifts the control valve member 34 in the axial direction of its control valve seat 36 so that fuel from the valve chamber 32 and subsequently from the control chamber 28 in the low pressure region 12 and from there via the fuel return port 10 and the return line 11 to the reservoir 3 can flow out. In this case, the flow cross-sections of the inlet throttle 29, which may alternatively be embodied, for example, in the injector component 27, and the outlet throttle 31 are matched to one another such that when the control valve 33 is open, a net outflow of fuel from the control chamber 28 results. with the result that the fuel pressure in the control chamber 33 drops rapidly and thus a hydraulic opening force acts on the injection valve element 13, which lifts in sequence from its injection valve element seat 23 and the nozzle hole assembly 17 for injecting fuel into the combustion chamber releases.

To end the injection process, the energization of the electromagnetic actuator 38 is interrupted. With a one end on a shoulder of the pressure pin 35 and the other end on an upper end face of the armature plate 37 supporting the control closing spring 39, the sleeve-shaped control valve member 34 is moved back to its control valve seat 36. The fuel flowing in through the inlet throttle 29 causes an increase in pressure in the control chamber 28, with the result that the injection valve element 13 is moved back onto the injection valve element seat 23 assisted by a closing spring 40. The closing spring 40 is arranged in the high-pressure space 8 projecting into the nozzle body 15 and is supported at one end on a lower end face of the injector component 27 and at the other end against a circumferential collar 41 of the injection valve element 13. To generate a sufficiently high closing force, the axial channels 16 may be formed as throttle channels, thus reducing the pressure in the nozzle chamber 24 in comparison to the high pressure chamber 8 something. However, the pressure is advantageously reduced by only about 100 to 200 bar, so that the nozzle chamber 24 and the high-pressure chamber 8 can be regarded as a common space. By caused by the closing of the injection valve element 13 abrupt drop in the injection rate arises in the nozzle chamber 24 and especially in the high-pressure chamber 8 a pressure surge (Joukowski shock) of the fuel high-pressure accumulator 4 reflected becomes. These volume waves lead to pressure oscillations. The resulting peak pressures may be several hundred bar above the maximum rail pressure, whereby the entire fuel injector 1 and the supply system must be designed according to the peak pressures.

In order to allow the injector body 19 to not be overly stressed and subsequently made from conventional steels such as C45, the fuel injector 1 shown in FIG. 1 provides an annular space 42 extending radially in between the high-pressure chamber 8 and the injector body 19 is located. The annular space 42 extends in the axial direction over the largest part of the axial extent of the injector body 19 and, if necessary, can also project axially into the nozzle body 15.

The annular space 42 is bounded radially inwards with respect to the high-pressure space 8 by a tubular portion 43 of the injector component 27. In the injector component 27, a stepped bore 44 is introduced for this purpose, which delimits the control chamber 28 in its upper end in the drawing plane. In the annular space 42 there is permanently a lower fuel pressure than in the high pressure chamber 8 and permanently higher fuel pressure than in the low pressure region 12 of the fuel injector 1. By means of a throttle arrangement to be explained below, the pressure in the annular space 42 is permanently lower than in the high pressure chamber 8. Die Flow cross sections of the chokes to be explained below are adjusted so that the pressure in the annular space 42 does not exceed 1800 bar. As a result, the pressure load of the injector body 19, at least in druckkriti- see areas reduced over most of its axial extent.

As is apparent from FIG. 1, the supply channel 7 is formed in sections as a bore in a sleeve-shaped connection part 60 screwed to the injector body 19, wherein the supply channel 7 continues in the radial direction into the high-pressure space 8, and thereby the annular space 42 in FIG Passed through radial direction and sealed against this. For this purpose, the injector component 22 is provided with a positive diameter jump 45 (circumferential collar) in the region of the supply channel 7, into which recesses 46 running at a distance from the supply channel 7 are introduced, via which the fuel flows from a lower section of the annular space 42 into an upper one Section of the annular space 42 can flow unhindered and preferably unthrottled.

The injector component 27 shown in FIG. 1 does not necessarily have to be made in one piece. Thus, it is conceivable, for example, to limit the annular space 42 with an independent, tubular element formed here by the tubular section 43, which is supported in the axial direction on a separate component which defines the low-pressure region 12 here as a plate section 47 of the injector component 27.

In the axial direction upward, the annular space 42 is bounded by the plate section 47 of the injector component 27, which, as mentioned above, can also be embodied as a separate component. This is pressed by a valve clamping screw 48 against an annular shoulder 49 of the injector body 19. In the axial direction down the annular space 42 is bounded by a sealing element 50, which is located radially between the lower region of the tubular section 43 of the injector component 27 and the injector body 19.

As can be seen from FIG. 1, under high pressure, in the exemplary embodiment shown, 2500 bar of fuel can flow in the radial direction via an annular space inlet throttle 51 into the annular space 42. From there, fuel flows through an annular component outlet throttle 52 provided in the injector component 27 into the low-pressure region 12 of the fuel injector 1. The flow cross-sections of the annular space inlet throttle 51 and the annular space outlet throttle 52 are matched to one another such that the pressure in the annular space 42, as explained above, does not exceed a maximum pressure of 1800 bar, whereby the pressure load of the injector body 19 is significantly reduced. As can be seen from FIG. 1, the annular space inlet throttle 51 and the annular space outlet throttle 52 are designed as throttle bores, whereby alternative production possibilities can also be realized. Since the pressure in the annular space 42 has no influence on the injection behavior of the fuel injector 1, the annular space inlet throttle 51 and the annular space drain throttle 52 can be made very small, whereby the necessary for the pressure reduction parasitic flow rate is low. On the other hand, the pressure in the annular space 42 does not react to highly dynamic pressure changes in the high-pressure space 8 serving as a minirail, but only to function-related rail pressure changes.

In the following, further alternative embodiments of a fuel injector 1 are explained with reference to FIGS. 2 and 3. In this case, the structure of these embodiments substantially corresponds to that shown in Fig. 1 and before described embodiment. To avoid repetition, therefore, only differences from the exemplary embodiment shown in FIG. 1 and described above will be explained below. With regard to common features, reference is made to FIG. 1 and the preceding description of the figures.

In contrast to the embodiment of FIG. 1, the pressure in the annular space 42 is not permanently reduced in the embodiment of FIG. 2 compared to the high-pressure chamber 8. This is due to the fact that the fuel from the annular space 42 can only temporarily flow into the low-pressure region 12 of the fuel Inj ector 1. The flow from the high-pressure chamber 8 into the annular space 42 also takes place in the exemplary embodiment shown in FIG. 2 via an annular space inlet throttle 51 designed as a throttle bore. The annular space drain throttle 52 is formed by a pressure relief valve 53 designed as a check valve in the embodiment according to FIG is designed that this opens only in the direction of low pressure area 12 when a minimum pressure in the annular space 42 is exceeded. In this way, a pressure reduction in the annular space 42 is thus only realized if this is necessary, so critical pressures occur for the stability. Overall, this can further reduce the parasitic outflow quantity. The overpressure valve 53 comprises a valve element 54 formed as a steel ball, which is acted upon by a spring 55 designed as a flat spring in the direction of a valve seat 56 formed on the injector component 27, more precisely on the plate section 47. In this case, the underside of the valve element 54 via a channel 57 in the injector 27 is permanently in communication with the annulus volume of the annular space 42. The pressure exceeds In the annular space 42, a minimum pressure, the spherical valve element 54 is lifted against its spring force from its valve seat 56 so that throttled fuel can flow out of the annular space 42 into the low-pressure region 12. The pressure relief valve 53 is dimensioned so that the throttling action of the pressure relief valve 53 has the desired level of pressure reduction in the annular space 42 result.

As is further apparent from FIG. 2, the spring 55 designed as a flat spring is clamped axially between the valve clamping screw 48 and the upper side of the plate section 47 of the injector component 27 in the plane of the drawing.

The exemplary embodiment of a fuel injector 1 shown in FIG. 3 functions on the same principle as the exemplary embodiment shown in FIG. 2 and described above. In contrast to the exemplary embodiment according to FIG. 2, here the annular space inlet throttle 51 is not designed as a throttle bore but as a leakage gap between a circumferential collar 58 of the tubular section 43 of the injector component 27 and the injector body 19. A further annular space inlet throttle 51 is provided between the upper positive diameter jump 45 (circumferential collar) and the injector body 19.

Also, no throttle channel is provided as annular space drain throttle 52. This is formed by the pressure relief valve 53, via which the annular space 42 is connected to the low-pressure region 12 of the fuel Inj ector 1. The valve element 54 is formed by the plate portion 47 of the Injektorbauteils 27. This is in the closed state of the pressure relief valve 53 on the annular shoulder 49 of the injector body 9 on. When the overpressure valve 53 is open, the plate section 47 is adjusted in the axial direction upward, so that an annular gap is formed axially between the plate section 47 and a biting edge 59 of the injector body 19, with the flow cross-section of the annular gap being adjusted so that the desired throttling is achieved ,

The plate section 47 only lifts off from its valve seat 56 formed by the biting edge 59 on the injector body 19 when the pressure force acting on it exceeds the spring force of a spring 55 designed as a plate spring, which is supported in the axial direction upward on the valve clamping screw 48. The spring 55 tends to press the plate portion 47 axially downwardly against the annular shoulder 49 of the injector body 19. By adjusting the valve clamping screw 48, the bias of the spring 55 can be adjusted.

Claims

claims

1. Fuel Inj ector, in particular common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, with a fuel return port (10) and with a one-piece or multi-part, adjustable between an open position and a closed position injection valve element (13) at least in sections, in a high-pressure chamber (8) provided in an injector body (19),

characterized,

that between the high-pressure chamber (8) and the injector body (19) an annular space (42) is arranged, in which the fuel pressure during operation of the fuel injector (1), at least temporarily, less than the fuel pressure in the high-pressure chamber (8) and is higher than the fuel pressure in the fuel return port (10).

2. Fuel Inj ector according to claim 1, characterized in that the pressure in the annular space (42) is at least half as high as the pressure in the high-pressure chamber (8).

3. fuel Inj ector according to one of claims 1 or 2, characterized in that the from a supply channel (7) inflowing fuel is passed directly into the high-pressure chamber (8).

4. Fuel injector according to one of the preceding claims, characterized in that the high-pressure chamber (8) extends axially up to a nozzle senlochanordnung (17).

5. Fuel Inj ector according to any one of the preceding claims, characterized in that the high-pressure chamber (8) and / or a high-pressure chamber (8) leading supply channel (7) via at least one annular space inlet throttle (51) hydraulically connected to the annular space (42) is.

6. Fuel Inj ector according to any one of the preceding claims, characterized in that the annular space (42) via at least one annular space drain throttle (52) with a, preferably a control erventil (33) hydraulically downstream, low pressure region (12) of the fuel Inj ector (1).

7. Fuel injector according to one of the preceding claims, characterized in that the annular space (42) is bounded radially inwardly by an at least partially tubular, preferably a control chamber (28) limiting injector component (27).

8. Fuel injector according to one of the preceding claims, characterized in that the pressure in the annular space (42) in comparison to the pressure in the high-pressure chamber (8) only after exceeding a minimum pressure, in particular more than 1800 bar, is reduced.

9. Fuel Inj ector according to one of the preceding claims, characterized in that the annular space (42) via at least one, preferably throttled in the open state, in particular designed as a check valve, pressure relief valve (53) with the low pressure region (12) of the fuel - Injector (1) is hydraulically connectable.

10. Fuel injector according to one of the preceding claims, characterized in that the pressure relief valve (53) comprises a spring (55), in particular a leaf spring, and a, in particular spherical, valve element, by the spring (55), preferably against a the low-pressure region (12) limiting injector component (27), spring force is applied.

11. fuel Inj ector according to any one of the preceding claims, characterized in that an adjustable valve element of the pressure relief valve (53) by a low pressure region (12) limiting the injector component (27) is formed, the mit- A spring (55), in particular by means of an expansion sleeve or a plate spring, against the injector body (19) is pressed.

12. Fuel Inj ector according to claim 11, characterized in that when the overpressure valve (53) is open, in particular an annular, leakage gap, preferably axially, between the injector component (27) and the injector torkörper (19) is formed.

13. Fuel injector according to one of claims 11 or 12, characterized in that the bias of the spring (55) of the pressure relief valve (53) by means of a valve clamping screw (48) is adjustable.