GB2370608A

GB2370608A - A control valve for a fuel injector of an internal combustion engine

Info

Publication number: GB2370608A
Application number: GB0122591A
Authority: GB
Inventors: Wolfgang Scheibe
Original assignee: LOrange GmbH
Current assignee: LOrange GmbH
Priority date: 2000-09-20
Filing date: 2001-09-19
Publication date: 2002-07-03
Anticipated expiration: 2021-09-19
Also published as: DE10046875B4; DE10046875A1; GB0122591D0; GB2370608B

Abstract

A control valve for a fuel injector of an internal combustion engine comprises a control plunger 2 which is axially displaceable in a receiver 7 at the housing 1, and a valve head 10 which axially adjoins control plunger 2. The control plunger 2 is axially guided in the housing 1 over one plunger region 9, whilst an opposite plunger region 8 with respect to the valve head 10 forms the guide for an insert body 22. The insert body 22 comprises a sealing edge (11, 12) which cooperates with the valve head 10 and is axially supported in relation to the housing 1. The insert body 22 may be axially displaceable in the housing 1 and formed as a sleeve, coaxial with the control plunger 2.

Description

s A control valve for fuel injectors This invention relates to a control

valve for fuel injectors, particularly for fuel injectors of internal combustion engines which employ receiver pressure injection and which are 10 operated with diesel or heavy fuel.

In modern fuel injection systems, particularly in injection systems which employ receiver pressure injection, very high pressures are used which reach 2000 bar or more.

Irrespective of this, predetermined control times and predetermined quantities of 15 injected fuel, as well as courses of injection which are predetermined with regard to the engine output which is to be attained, have to be maintained, possibly at predetermined exhaust gas levels. The pressure to be controlled and the actuating forces which are associated therewith and which have to be exerted make it necessary for the injected medium, which is generally diesel or heavy fuel oil, also to be used as a control 20 medium for the injection nozzle of the fuel injector, which is acted upon by an upstream controller which operates substantially free from pressure, so that the requisite actuating forces for the control plunger of the control valve can be applied via actuators of comparatively low power. This is irrespective of the fact that due to the very high pressures to be controlled very narrow guide clearances have to be 25 maintained for sealing reasons also.

With respect to a 3/2-way valve which operates with equalization of pressure, which comprises a valve chamber and a valve head which is associated with the control plunger, which can be displaced between the axially spaced-apart seat faces of the 30 valve chamber by the axial movement of the plunger, and which exposes different flow paths depending on its contact position, this means that due to the larger diameter of the valve head compared with the diameter of the guide faces of the control plunger on the

- 2 housing side, the guide faces have to be associated with separate components so that the valve head, the diameter of which is larger than that of the guide faces, can be disposed in the valve chamber, or can be introduced therein. This means that at very narrow fitting clearances a multiplicity of fit configurations have to be matched to each 5 other, which from a manufacturing point of view means extraordinary accuracy and high cost, particularly since the requisite fit configurations, provided that these are not guidance fit configurations, have to be constructed as sealing press fits. This is made even more difficult because predetermined axial spacings have to be exactly maintained so that they do not falsify the control characteristics which are aimed at each time.

The underlying object of the present invention is to provide a design for a control valve for fuel injectors in which the maintenance of the constructional constraints imposed on the control valve, which are decisive as regards the quality of fuel injection, is achieved at a justifiable cost of production and installation.

For this purpose, the invention provides for the control plunger to be guided in the housing in its region which is situated on one side of the valve head, and to be used as a guide in its other region which is situated on the other side of the valve head, namely to be used as a guide for a strut-off pert or insert part which is disposed floating radially in 20 the housing, which also contains the radial guide for the radially guided plunger region.

The provision of guidance on a plunger region with a floating arrangement of the insert in relation to the housing provides the possibility of radially aligning the insert as long as no fixation in relation to axial support faces due to corresponding frictional forces occurs via the axial support of the insert. After centring has been effected, however, 25 correspondingly high axial compressive forces not only result in radial fixation due to friction, but also result in the requisite sealing, wherein the support of an insert body which is guided floating on one plunger region is advantageously provided in a plane of contact perpendicular to the axis of the control plunger, which plane of contact is also the reference plane with respect to the axial alignment of the insert body with regard to 30 the predetermined axial location of the associated valve seat, so that corresponding installation specifications can also be complied with as regards the location of the seat

face, and as regards the control plunger stroke and the respective control cross sections.

- 3 In combination with axial support in relation to a corresponding housing upper part with which the actuator can also be associated, and with regard to the seal in the corresponding contact face, radial sealing of the insert body in relation to the receiving 5 housing can optionally be dispensed with so that sufficient radial clearance is ensured between the insert body and the housing, wherein it may prove advantageous to provide for the insert body to make contact against the axially supporting top part, e.g. against the housing upper part, by means of a spring-loaded support, so that, superimposed on these spring forces, the respective sealing effect is correspondingly intensified with 10 increasing pressurization.

Within the scope of the invention, however, it is also possible to provide an additional seal, which is preferably provided as a ring seal, for example, which is in axial contact with the end face of the insert body facing the valve chamber, and the radial clearance 15 thereof in relation to the receiving housing is not impeded thereby when the insert body is guided on the plunger.

In particular, when a ring seal is employed which is axially supported against the insert body and is radially supported against the peripheral wall of the valve chamber, sealing 20 effects which are intensified depending on the pressure can be achieved, depending on the shape of the profile. In this respect, it has proved to be particularly advantageous if the ring seal is formed with a curved inner profile between its limbs, whereby additional sealing effects can also be obtained by the ring seal being supported at its outer circumference on a periphery, preferably the periphery of the valve chamber, the 25 diameter of which is smaller than the diameter of the receiver bore for the insert body, so that additional, labyrinth-like sealing effects are obtained.

With regard to the channel guides, it has proved to be advantageous if a channel guide is associated with the insert body and if the connection to the housing is displaced into 30 the region of axial support in relation to the upper part, wherein overlapping channel cross-sections, the extent of overlap of which optionally depends on the stroke position, are provided in the transition from the insert body to the valve chamber, so that throttle

effects which serve to determine the course of fuel injection and which depend on the stroke position can be obtained, for example.

Further details and features of the invention follow from the claims. Moreover, the 5 invention, including further details thereof, is more fully explained below with reference to the drawings, where: Figure 1 is a schematic sectional illustration of the valve chamber region of a control valve for fuel injectors, 10 Figure2 shows part of the valve chamber region with the associated channel guides, on an enlarged scale: Figures shows another embodiment of the control valve, as an illustration corresponding to that of Figure 1; and Figure 4 is a schematic illustration of a control valve.

The starting point for the illustration of Figure 4 is a fuel injector, which in the known manner comprises a fuel injection valve, a control valve associated therewith, and an actuator, which are assembled to form a modular unit, wherein the actuator associated with the rear end opposite the injection valve is constructed as a magnetic actuator or as 20 a hydraulic actuator which acts on the control plunger 2 of the control valve 3, which control plunger is axially displaceable in the valve housing 1, a portion of which control valve is illustrated in Figure 4 and via which the injection valve is controlled. In association with the use of fuel injectors of this type in receiver pressure fuel injection systems, the valve element of the injection valve is displaced into an open position 25 against corresponding restoring forces, by the action of injection medium on the pressure side, and closes again when the pressure-side connection is shut off. The relevant connections are denoted by reference numerals 4 to 6, wherein connection 4 symbolises the connection to a fuel storage device which is under a high pressure, connection 5 symbolises the connection to the injection valve, and connection 6 30 symbolises the connection to a low pressure region, i.e. for example to a return line leading to a supply vessel or to an actuating plunger which maintains the pressure to be

- 5 controlled in the valve chamber 17 provided that the control plunger 2 is not sealed at sealing edge 11.

Connections 4, 5 and 6 lead into a receiver 7 on the housing side for the control plunger 5 2, wherein between two axially opposite regions 8 and 9 the control plunger 2 comprises a valve head 1O, which is axially displaceable between mutually opposite sealing edges 11 and 12 on the housing side and which comprises tapered sealing ring faces 13 and 14 corresponding to sealing edges 11 and 12. On both sides of the valve head 10, regions 8 and 9 comprise annular zones 15; 16 of reduced diameter, which are 10 situated in the region of overlap with connections 6 and 4, respectively, whilst connection 5 leads on to the valve chamber 17.

The valve head 10 has a larger diameter than that of the plunger regions 8 and 9, which with regard to the sought-after pressure equalization have pressurised faces of the same 15 size, so that in order to accommodate the valve head 10 into the valve chamber 17 it is necessary to widen the receiver 7, at least on one side of the valve chamber 17, to a diameter larger than the requisite diameter of the corresponding plunger region, namely of plunger region 8 here. In the schematic illustration, the receiver 7 is accordingly formed by two coaxial bore regions, bore region 18 of which is associated with plunger 20 region 9, and bore region 19, the diameter of which is widened, is associated with plunger region 8, wherein a bridging sleeve 20 is provided to compensate for the differences in diameter in bore region 19. In view of the high pressures to be controlled and the requisite sliding clearance seals for the control plunger 2 and the requisite press-fit seal between the bridging sleeve 20 and the associated receiver bore - bore 25 region 19 - it can be seen that very close radial tolerances are necessary for the corresponding coaxial alignment of the associated bore regions, and that with regard to the maintenance of predetermined control cross-sections it must be ensured that there is a close axial tolerance, which means a corresponding accuracy of insertion with regard to the bridging sleeve 20. In practice, these prerequisites cannot be fulfilled at a 30 justifiable cost.

- 6 In contrast, the embodiments shown in Figures 2 and 3 are designs according to the invention, which will be explained below with reference to the illustrations of Figure 4, using the same reference numerals where possible.

5 In the valve housing, the control plunger 2 is again disposed in a receiver 7, which comprises two bore regions 18 and 19 which are concentric with the axis 21 of the control plunger and in the transition between which the valve chamber 17 is situated.

The latter receives the valve head 10 of the control plunger 2, the diameter of which in its plunger region 9 below the valve head 10 as illustrated in Figure 2 is reduced to the 10 diameter of the bore region 18, and which is longitudinally displaceably guided therein with the formation of a seal. The annular zone 16 of reduced diameter of the plunger 2, on to which channel 4 leads, is situated between said guided plunger region 9 and the valve head 10.

IS In its transition to the valve chamber 17, bore region 18 forms the sealing edge 12, which is associated on the valve head 10 side with a tapered sealing face 14, so that when the sealing face 14 is placed on the sealing edge 12 the connection from connection 4 to the valve chamber 17 is shut off. Connection 5 leads from the valve chamber 17, and in the embodiment exemplified the valve chamber 17 is formed by the 20 lower section of bore region 19. The latter receives the insert body 22, which is of sleeve-like form and functions as a bridging sleeve and a counterseat valve body and bridges the annular space between plunger region 6 and the wall of bore region 19, wherein the clearance between the insert body 22 and the wall of bore region 19 is such that according to the invention it is possible to centre the insert body 22 in relation to 25 plunger region 8 at the periphery thereof. On plunger region 8, the insert body 22 is therefore centred in bore region 19, and is disposed floating in relation to the housing.

The insert body 22, the inside diameter of which corresponds to the outside diameter of the control plunger 2 in plunger region 8 when a sliding seal is formed, is associated with sealing ring face 13 on the valve head 10, which sealing face corresponds to 30 sealing edge 11 on the insert body, so that on the displacement of the control plunger 2 towards the insert body 22 the valve chamber 17 is shut off from connection 6 due to the cooperation of sealing edge 11 with annular sealing face 13. Analogously to the

- 7 annular zone 16, between the valve head 10 and the insert body 22 the control plunger 2 is provided, in region 8 in the transition to the valve head 10, with an annular zone 15 of reducing diameter which communicates with connection 6.

S As can be seen in particular from the enlarged illustration of Figure 2, this connection starts from annular zone lS and runs via one or more bores or channels, for example via a diagonal bore 23 as illustrated here, to an annular groove 24 which is worked into the periphery of control plunger region 8 and is at an axial spacing from annular zone 15. Annular groove 24 is associated with an annular groove 25 in the insert body 22 10 which is connected via junction bores 26 to an annular channel 27, which is provided in the end face of the insert body which is located in the end face of the insert body 22 remote from the valve body 10 or valve chamber 17, said end face being denoted by 28.

Annular channel 27 corresponds to an annular channel 29 in the housing upper part 30, a bore 31 of which freely surrounds part of region 8 of the control plunger 2, which part 1 S axially protrudes beyond the insert body 22 and which is associated, in a manner which is not illustrated, with the actuator via which the control plunger 2 can be acted upon axially, wherein known actuating elements can be used as the actuator, such as magnetic actuators, piezo-electric actuators, or pneumatic or hydraulic actuators which are operated via a controller in the usual manner.

As a result of the design of the control plunger 2 with regard to the equal size of its opposite faces which are acted upon by pressure, said conkol plunger is acted upon in opposite directions, namely in both stroke directions, by equal pressures, so that it is only the blanking- off spring forces which bias the control plunger 2 towards an initial 25 position in which the connection between connections 4 and 5 is blanked off, as illustrated in Figures 1 to 3, which have to be overcome by the actuator. Alternatively, actuators can also be used which act in both stroke directions, for example combined permanent magnet/eleckomagnet actuators. However, the considerable pressures to be controlled mean that very small clearances have to be maintained, irrespective of the 30 displaceability of the control plunger 2 in the respective guide bores, in order to achieve an impervious seal in the respective change-over positions. Moreover, amongst other constraints, the exact maintenance of predetermined injection quantities also implies

very close tolerances with respect to the respective control crosssections, and thus also implies very precise axial positioning of the insert body 22 due to the changing association between the sealing edges.

5 This can be achieved with the solution according to the invention at a justifiable cost of assembly, wherein the upper surface of the housing 1 which delimits the receiver 7 for the control plunger 2 is available as a planar reference plane 32, in relation to which the insert body 22 can be positioned without difficulty when its dimensions are correspondingly matched so that the predetermined clearance widths in the valve seats 10 can be maintained exactly. At the same time, a condition is also created in which during the action of axial forces on the insert body 22 the latter is directly supported against the housing upper part 30, and the design of the housing upper part as a planar surface and as a reference plane means that the insert body can be placed directly thereon, with a corresponding radial overlap with the insert body 22 and with support against the end 15 face 28 thereof. The radial overlap with the insert body 22 also ensures, at low cost, the necessary seal of the insert body 22 from the housing 1, since the housing upper part 30 in the reference plane 32 also overlaps the housing 1. Annular channels 27 and 29 are also situated in the annular sealing and support zone denoted by 33 which is formed by the overlap of the upper part 30 with the insert body 22, so that a more impervious 20 connection is correspondingly ensured, particularly since the corresponding surface pressures increase depending on the pressure, so that an improved seal is obtained at higher pressures. An aspect which is important as regards production costs also is that the radial alignment of the insert body 22 towards the control plunger 2, together with the axially displaceable, close tolerance guidance which is provided, results in 25 relatively large negative tolerances in the guidance of the insert body 22 in relation to the receiver in bore region l9, as can be seen in particular from Figure 2, so that the insert body 22 is guided in relation to the housing 1 so that it is axially displaceable but almost radially free, but nevertheless assumes an axially fixed and predetermined position. This is achieved by the axial support of the insert body 22 in relation to the 30 upper part 30 which is fixed to the housing 1, wherein a corresponding basic support can be provided via spring elements as denoted by 34 in Figure 2. The spring elements 34 are axially supported between the insert body 22 and the housing 1 and bias the

- 9 - insert body towards the upper part 30, wherein plate springs or the like can alternatively be provided as distinct from the type of springs illustrated.

Within the scope of the present invention, the use of the insert body 22 also provides 5 conditions which are advantageous as regards the production technology employed because they affect the course of the fuel injection. The following explanations which relate to this aspect assume that the supply of high pressure is effected via connection 4, the feed to the injection nozzle is effected via connection 5, and the return flow is effected via connection 6, analogously to the illustration of Figure 4. The return flow is 10 effected, in the known manner, via the spring space which accommodates the spring which biases the valve element of the injection nozzle towards the closed position thereof, or via a plunger space in which a holding-down plunger is disposed which assists the spring force under the action of pressure. When return flow is initiated, the pressure-dependent force which biases the valve element towards its closed position 15 decreases, so that the valve element can open and is biased in its direction of opening by the injection pressure. The course of the fuel injection can thus be influenced by correspondingly influencing the course of the pressure on the low-pressure side.

One option for controlling the course of the pressure on the low-pressure side which is 20 particularly advantageous within the scope of the present invention is illustrated in Figure 2, where it can be seen that, with respect to the control plunger 22 and depending on the stroke thereof, the opening cross-sections between the valve head 10 and the insert body 22 on the one hand and between annular grooves 24 and 25 on the other hand can be designed so that they are offset to a greater or lesser extent, or so that 25 they overlap, with respect to a predetermined stroke position, so that, depending on the design, offset opening cross-sections, and, associated therewith, different throttle behaviours, can be achieved.

Figure 2 illustrates that with respect to the given stroke position of the control plunger 30 2, the stroke 35 as far as the shut-off of the opening cross-section for the annular gap between the valve head 10 and the insert body 22 is greater than the stroke 36 which has to be covered before annular grooves 24 and 25 are shut off from each other. The

- 10 pressure on the return side (connection 6) is thus reduced, and in particular an increased build-up of pressure on the return side during the changeover phase of the control valve is reduced by the short circuit between the connections which occurs in this phase, which results in a reduction in the locking force for the valve element of the fuel 5 injection valve and which also results in an earlier commencement of injection at a time when the injection pressure has not yet built up completely, which may be desirable for some types of pre-injection. If other forms of time-dependent fuel injection behaviour are desired, the solution according to the invention provides favourable conditions for these to be realised, e.g. for an increase in locking force during the short circuit phase 10 in order to prevent injection in general in this phase, or to achieve an increase in pressure in the final phase of injection.

Figure 3 shows a construction which in principle is the same as that shown in Figures 1 and 2, and it is only the different constructional features of this design which are 15 considered below in relation to this illustration.

The valve chamber in which the plunger 2 with its valve head 10 is situated is again denoted by 17. The valve chamber 17 is delimited in the direction towards plunger region 8 by an insert body 41, though which plunger region 8 of the plunger 2 passes, 20 and which is centred on the plunger 2 in plunger region 8 thereof with radially floating support in relation to the receiver on the housing side. The latter has a bore 42 for the insert body 41, wherein in the embodiment exemplified the diameter of said bore is larger than the diameter of the valve chamber 17, so that in a manner which is not compulsory but which is advantageous with regard to the seal - a housing step 43 is 25 formed in the transition region to the valve chamber 17, and the radially outer region of the insert body 41 radially overlaps said step. The radially inner region of the insert body 41 runs out into an annular sealing edge 11 which cooperates with the valve head 10, and a sealing ring is disposed in the region of overlap of the insert body 41 towards the valve chamber 17 and is radially supported against the peripheral wall 44 of the 30 valve chamber 17 and axially supported against the insert body 41. The sealing ring 45 is preferably formed as an angled sealing ring and comprises limbs 46, 47, wherein the base which joins the latter is convex and is curved inwards towards the seal vertex 48.

When pressure is applied, the sealing ring 45 is forced radially towards the peripheral wall 44 of the valve chamber 17 and axially towards the insert body 41, so that what is approximately a sealing labyrinth is formed from the valve chamber 17, and the radial S action of pressure on the sleeve-shaped insert body 41 by pressure medium at high pressure which enters the bore 42 is at least reduced. If the sealing ring 45 is additionally inserted in the valve chamber 17 under a certain radial prestress, for which purpose it may be advantageous in order to facilitate assembly if the corresponding wall region of the valve chamber 17 is made slightly tapered in the direction of insertion, the 10 sealing ring 45 can at the same form an axial support for the insert body 41 on the valve chamber side, by means of which the insert body is held with its face facing the housing upper part 30 in contact with the latter, so that the sealing ring 45 in addition approximately performs the function of the spring-loaded support 34 in the embodiment illustrated in Figure 2. An embodiment as shown in Figure 3 can be used IS particularly advantageously for control valves which operate under very high operating pressures of the order of up to 2000 bar. The sealing ring, particularly when it has a rectangular basic cross-section, can also be of stepped, offset or different form in its region of contact with the valve chamber and/or with the insert ring 41, with the effect that the contact faces are reduced in size to provide increased surface pressure and an 20 improved sealing effect.

The construction of the embodiment shown in Figures 1 to 3 results in considerable advantages as regards assembly, since the guidance of the insert body 22, 41 on the control plunger 2 means that positional matching can be effected directly in relation to 25 the control plunger 2 and it is possible to effect corresponding fixation with respect to the housing without a radial pressing operation.

For this purpose, plunger region 9 of the control plunger 2 can first be inserted in bore region 18 until the valve head is seated on the corresponding seat face. Thereafter, the 30 insert body 22, 41 can be pushed, as a counter-seat valve body, on to plunger region 8 of the control plunger 2 until it is seated on the valve head almost forming a seal. As a planar seat face 32 for the upper part 30, the housing upper surface then forms a

- 12 reference plane 32 which enables the initial position described above, and the requisite stroke displacement of the insert body 22, 42 in relation thereto, to be recorded perfectly using metrological techniques, which thus gives the desired overflow cross-

section between the valve head 10 and the insert body 22, 41. It is possible to make a 5 corresponding fine adjustment by correcting the length of the insert body, whereby constructionally predetermined dimensional relationships can also be realised at comparatively low cost, even taking into account the extreme demands imposed on dimensional constancy and the extreme conditions of pressure loading.

l O Due to the radial guidance of the insert body 22 in relation to the control plunger 2, and due to the corresponding radial clearance of the insert body 22, 41 in relation to the receiving bore, the axial support of the insert body 22, 41 in relation to the housing upper part 30 in the reference plane 32 firstly permits alignment with a correct central position, with clearance and with only a slight action of pressure, and secondly under 15 the effect of higher pressures results in accurate fixing due to frictional engagement with the formation of an effective seal at the same time, so that corresponding channel guides can also advantageously bridge the region of the reference plane 32 with the formation of a seal.

20 Superimposed on the radial, central guidance of the insert body 2 in relation to the cylindrical plunger region 8, dimensional differences which result from manufacturing and assembly operations are kept to a minimum, even though the guide and seal faces on the plunger and insert body sides can be machined with metal removal. In this respect, it is also possible to align the insert body towards the valve head so that 25 starting from the aforementioned tapered support in relation to the insert body a central position of the insert body is achieved in relation to thecylindrical plunger region 8.

Claims

- 13 Claims

1. A control valve for fuel injectors, particularly for fuel injectors of internal combustion engines which employ receiver pressure and which are operated with diesel 5 or heavy fuel oil, comprising a control plunger (2) which is axially displaceable in a receiver (7) on the housing side and which comprises a valve head (10) which is situated between two plunger regions (89) and which is disposed in a valve chamber (17) of the housing (1), which valve chamber is provided on both sides of the valve head (10) with a sealing edges (11; 12) which face the latter and which are adjoined by 10 receiver regions (bore regions 18) of smaller diameter on the housing side, one of which receiver regions forms a guide bore for the associated plunger region (9) and the other of which is formed by an insert body (22; 41) which is guided on the associated plunger region (8), is axially supported towards the housing (1) and comprises a sealing edge (1 1).

2. A control valve according to claim 1, characterized in that the insert body (22; 41) is supported so that it is axially displaceable with a radial clearance in relation to the housing (1).

20 3. A control valve according to claims l or 2, characterized in that the insert body (22; 41) is formed as a sleeve which is coaxial with the control plunger (2).

4. A control valve according to any one of the preceding claims, characterized in that the insert body (22; 41) is supported in a direction towards its axial support 25 position in the housing (housing upper part 30).

5. A control valve according to claim 4, characterized in that the insert body (22) is flexibly supported in a direction towards its axial contact position.

30 6. A control valve according to claim 5, characterized in that the insert body (22) is resiliently supported in a direction towards its axial support position.

- 14 7. A control valve according to any one of the preceding claims, characterised in that a sealing ring (45) is associated with the insert body (41) at the boundary thereof towards the valve chamber (17).

5 8. A control valve according to any one of claims 1 to 6, characterised in that the insert body (41) is biased in a direction towards its axial support via a support ring (sealing ring 45) which is associated with the valve chamber (17).

9. A control valve according to claim 8, characterised in that the support ring is 10 formed as a sealing ring (45).

10. A control valve according to any one of claims 7 to 9, characterised in that the support and/or sealing ring (45) is disposed radially clamped in the valve chamber (17).

15 11. A control valve according to any one of claims 7 to 10, characterised in that the support and/or sealing ring (45) is formed as an angled ring.

12. A control valve according to any one of the preceding claims, characterised in that when the valve is constructed as a 3/2-way valve disposed downskearn of the valve 20 chamber (17) the control plunger (2) comprises a cross sectional region (annular groove 24, 25) which exerts a stroke-dependent overload in its region which overlaps the support ring (22).

13. A control valve according to claim 12, characterised in that the cross-sectional 25 region which exerts a stroke-dependent overload is formed by annular grooves (24, 25) and which are associated with each other and which are provided in the control plunger (2) and in the insert body (22; 41).

14. A conko1 valve according to any one of the preceding claims, characterised in 30 that the axial support face is formed as a sealing face in the transition between the insert body (22; 41) and the housing upper part (30).

15. A control valve according to claim 14, characterized in that the channel connection between the insert body (22; 41) and the housing passes through the axial support face between the insert body (22; 41) and the housing upper part (30).

16. A control valve for a fuel injector substantially as any of the embodiments herein described with reference to the accompanying drawings.