GB2324336A

GB2324336A - I.c. engine fuel-injection unit with electromagnetic control valve

Info

Publication number: GB2324336A
Application number: GB9806898A
Authority: GB
Inventors: Josef Buergler; Franz Guggenbichler; Jaroslaw Hlousek
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-04-18
Filing date: 1998-04-01
Publication date: 1998-10-21
Anticipated expiration: 2018-04-01
Also published as: GB9806898D0; GB2324336B; JP4125816B2; JPH10299602A; DE19716220A1; DE19716220B4

Abstract

The invention relates to a fuel-injection unit (15), which comprises an injection valve (17), which protrudes into the combustion chamber of the internal combustion engine, and for the purpose of controlling the injection procedure comprises a 3 port directional valve as a double seat valve, having a control valve member (45), which can be controlled by the supply of current by virtue of an electric operating magnet (49), wherein by means of a damping device (101) the control valve member (45) receives an anchor plate (81) on an end which is directed towards the operating magnet (49), whereby the control valve member (45) is moved without bouncing into position on a first valve seat (59) and a second valve seat (55).

Description

2324336

1 DESCRIPTION FUEL-INJECTION UNIT FOR INTERNAL COMBUSTION ENGINES

The invention relates to fuel-injection units for internal combustion engines.

Fuel injection units for internal combustion engines are known which comprise in each case at least one injection valve, which extends into the combustion chamber of the internal combustion engine and has an injection valve member which, for the purpose of controlling the injection procedure, cooperates with a valve seat and comprises a pressure surface which lies in a first pressure chamber and is influenced in the opening direction by virtue of the pressure in the first pressure chamber and said injection valve member comprises on its rear side remote from the valve seat a second pressure chamber which is influenced at least indirectly by said pressure, wherein the first pressure chamber is continuously connected to a high pressure collecting chamber by way of a connection line to the high pressure line, and comprising a 3-port directional control valve which is controlled by an electric control device by means of an operating magnet and has a control valve member which comprises two sealing surfaces cooperating in each case with a valve seat and which in its one position moves into position with the one sealing surface on to the one valve seat and in so 2 doing closes the connection of the high pressure line to the second pressure chamber and opens the connection of the second pressure chamber to a relief line and in its other position opens and/or closes this connection, wherein the control valve member defines in its one position, which produces the connection with respect to the second pressure chamber to the relief line, a restricted cross-section, and in its other position produces an unrestricted connection, which is free in both directions of flow, from the second pressure chamber to the high pressure line.

DE 43 32 119 Al discloses a fuel-injection unit of this type which comprises a plurality of fuel-injection devices corresponding to the number of injection sites into the combustion chamber of a fuel engine which is to be supplied, wherein, for the purpose of achieving optimum fuel combustion in the combustion chamber of the internal combustion engine it is also possible, in addition to a free control of the commencement and termination of the injection, to control the injection pressure in a free manner. A high pressure fuel pump delivers fuel from a fuel storage tank at high pressure by way of a delivery line into a high pressure collecting chamber which is connected by way of high pressure lines to individual injection units corresponding to the number of injection sites into the combustion chamber of the internal combustion engine which is to be supplied. These injection units are each formed by an injection valve, which protrudes into.-the combustion chamber of the 3 internal combustion engine, and by a three port directional valve which controls said injection valve, wherein the valve member of the injection valve, which is formed as a seat valve, comprises on its shaft a pressure surface which is formed by virtue of a reduction in crosssection in the direction towards the valve seat and with which the said valve member protrudes into a first pressure chamber which is continuously connected to the high pressure line leading to the high pressure collecting chamber and the injection orifice on the valve seat and the pressure of said pressure chamber influences the valve member in the opening direction. By means of its end face remote from the valve seat the valve member defines a second pressure chamber which can be connected by way of a 3 port directional valve either to the high pressure line or to a relief line leading to the fuel storage container, wherein the cross-section, which is influenced in an effective manner by the pressure, of the valve member is smaller in the region of the first pressure chamber than in the region of the second pressure chamber.

The 3 port directional valve which is controlled by an electric control device is formed as a double seat valve whose piston-shaped control valve member, which can be adjusted in an axial manner between two stops formed as valve seats, connects the second end face pressure chamber on the injection valve to the high pressure line or the relief line depending upon the switching position. In so doing, the restricting function is produced within the 3 port directional valve during 4 the connection of the second pressure chamber to the relief line by way of a reduction in the through-flow cross-section for the cross-section flowing-off.

The control valve member is controlled by way of an operating magnet which is disposed separately by way of an intermediate plate on a housing of the injection unit. An anchor plate is placed on the control valve member on an end, facing the operating magnet, and is clamped by means of a screw. When the operating magnet is in a currentless state the control valve member is positioned by way of a return spring which is clamped between an annular disc of the intermediate plate and a spring plate on the valve member, whereby the control valve member moves into position with a second valve sealing surface on to a second valve seat, wherein the high pressure line is connected to a first pressure c6amber and the high pressure line is connected to the second pressure chamber by way of a second through-flow chamber on the 3 port directional valve. If an injection procedure is to be performed, the electric operating magnet is supplied with current by a control device and as a result displaces the control valve member of the 3 port directional control valve against the force of the return spring so as to lie on a first valve sealing surface and closes the connection between the first through-flow. chamber connected to the high pressure line and the second through-flow chamber connected to the second pressure chamber. Consequently, pressure is reduced in the second pressure chamber so that the injection valve member rises from its valve seat against the force of a valve spring and the injection valve opens.

The known fuel-injection unit has the disadvantage that upon the operating magnet being supplied with current the control valve member becomes unseated upon contact with the first valve sealing surface and in particular after the injection procedure has been performed and the electric operating magnet is switched to currentless, the control valve member becomes unseated as soon as it moves into position on its second sealing surface. At the commencement of the injection procedure, this unseating of the valve serves to delay the injection procedure and leads to a subsequent injection of fuel in particular when the injection procedure is terminated, so that it is not possible to form the injection progression in an exactly predeterminable and defined manner.

In accordance with the present invention in a fuel- injection unit of the initially mentioned type, between an end, which is directed towards the operating magnet, of the control valve member and an anchor plate, which is allocated to the control valve member, there is provided a damping device which damps a closing procedure of the control valve member in at least one direction of movement of the control valve member.

In contrast to known devices, a fuel-injection unit in accordance with the present invention has the advantage that by virtue of the 6 arrangement of a damping device between an end, which is directed towards the operating magnet, of the control valve member and the anchor plate it is possible to prevent the valve from becoming unseated, so that the control valve member moves into position on the first and second valve seat without bouncing. As a result it is possible to control the fuel-injection quantity in an exact manner, whereby a controlled and defined combustion is achieved in the combustion chamber of the internal combustion engine.

This damping device comprises in an advantageous manner a resilient element which on the one hand is fixedly connected to the control valve member and on the other hand is fixedly connected to the anchor plate. As a result, an indirect arrangement of the anchor plate with respect to the control valve member is provided so that a type of floating bea ring arrangement of the anchor plate can be provided. This arrangement has the advantage that, after a valve sealing surface moves into position on the valve seat and the closing procedure is terminated, the damping device becomes effective in that the movement of the anchor plate can be braked slowly by way of the resilient element. As a consequence, a sealing surface of the control valve member can lie on the valve seat without bouncing. Furthermore, it is advantageous that the anchor plate is mounted in a recess of an intermediate plate which on the one hand is attached to the housing and on the other hand receives the operating magnet. This intermediate space is filled with oil 7 in a damped manner so that in addition a damping effect can be achieved by virtue of the displacement of oil produced by the adjusting movement.

In accordance with a further advantageous embodiment of the invention it is provided that the resilient element is formed as a spring plate so that a damping effect similar to a leaf spring can be achieved. Furthermore, it is provided in an advantageous manner that the spring plate is disposed between two flexible elements by way of a screw in a fixed manner with respect to the control valve member. As a consequence, it is possible to adjust the degree of damping of the spring plate. In so doing it is provided in an advantageous manner that a flexible element disposed between the spring plate and the anchor plate is formed to be larger than an element which is disposed between the spring plate and the control valve member. As a result, a greater degree of damping can be produced when the operating magnet is switched to currentless and thus when the injection procedure is terminated, so that any subsequent injection of the fuel is reliably obviated.

The spring plate and the anchor plate are mutually connected by way of a known releasable or non-releasable connection, wherein a distance disc is disposed between the spring plate and the anchor plate. The thickness of the distance disc is advantageously greater than the thickness of at least one flexible element disposed between the anchor 8 plate and the spring plate, so that an intermediate space A remains which predetermines a resilient path of the anchor plate when the operating magnet is switched to currentless. By virtue of the thickness of the distance disc and/or the thickness of the flexible element it is thus possible to adjust the resilient path in dependence upon the adjusting forces.

The anchor plate comprises in an advantageous manner a stepped bore in which an attachment means, preferably a screw, is disposed and serves to fix the spring plate and the flexible elements to the control valve. The stepped through-going bore is formed with a first and second diameter to be larger than a screw head and a cylindrical shaft of the attachment means which is connected thereto, so that the anchor plate can be mounted in a floating manner in the direction of movement f the control valve member.

Furthermore, it is provided in an advantageous manner that a spaced interval B is formed between a screw head of the cofinection means and a shoulder formed by virtue of the stepped bore and said spaced interval forms a resilient path for the anchor plate when the operating magnet is supplied with current, so that it is possible commence the injection procedure in a controlled manner when the control valve member is moved on to a first valve seat.

The bouncing behaviour of the control valve member can be predetermined in an advantageous manner by virtue of the mass of the 9 anchor plate and by virtue of the mass of the damping device as well as by virtue of the design of the damping device. Furthermore, the resilient path can be adjusted by virtue of the size of the intermediate space between the flexible element and the anchor plate and also between the screw head and the shoulder of the stepped bore.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 shows a schematic cross-sectional illustration of a fuel- injection unit in accordance with the invention, and Figure 2 shows a schematic detailed illustration of a damping device which is disposed between the control valve member and an anchor plate.

In the case of the fuel-injection device illustrated in Figure 1, a high pressure fuel pump 1, which can be designed as e.g. a piston pump, delivers fuel from a low pressure chamber 3, which is formed as a fuel storage container, by way of a delivery line at high pressure into a high pressure collecting chamber 7. The pressure in the high pressure collecting chamber 7 can be controlled by way of a pressure control valve 9, which is inserted into a return line 11, which leads off from the high pressure collecting chamber 7, into the low pressure chamber 3 and which functions in dependence upon the operating parameters of the internal combustion engine, or the pressure can be controlled by virtue of the delivery rate of the high pressure fuel pump.

Furthermore, high pressure lines 13 lead off from the pressure collecting chamber 7 to the individual injection units 15 which correspond to the number of injection sites into the combustion chamber of the internal combustion engine to be supplied and which are each formed from an injection valve 17, which protrudes into the combustion chamber of the internal combustion engine, and a 3 port directional control valve 19 which are disposed in a common housing 20. The injection valve 17 is formed as a seat valve, having a piston-shaped injection valve member 21 which is guided in an axial manner in guide bore 23 and the one end face thereof comprises a conical sealing surface 25 with which the said valve member cooperates with a valve seat 29 which is adjacent to an injection orifice 27. The injection valve 21 comprises on its shaft a pressure shoulder 31 which is formed by virtue of a reduction in cross-section and which is directed in the direction towards the valve seat 29 with which the said injection valve protrudes into a first pressure chamber 33 which is formed by virtue of an increase in cross-section of the guide bore 23 and continues as an annular gap around the shaft of the injection valve member 21 as far as to the valve seat 29 and which pressure chamber is continuously connected by way of a connection line 35 in the housing 20 of the injection unit 15 to the high pressure line 13, through which the fuel pressure located therein continues into the first pressure chamber 33 and influences the injection valve member 21 in the opening direction against the force of a valve spring 39 disposed in a spring chamber 37. The said valve spring acts upon an end of the valve member 21, which end protrudes on the side of the guide bore 23 remote from the valve seat 29, by way of a spring plate 40, upon which a piston 38 also acts, which piston comprises a slightly larger diameter than the diameter of the guide bore 23 and defines, with its end face remote from the valve seat, a second pressure chamber 41 in a blind bore 42 which guides said piston chamber. The second pressure chamber 41 is connected by way of a connection duct 43 to the 3 port directional control valve 19, wherein the fuel pressure which can be built up therein influences the injection valve member 21 in the closing direction.

The 3 port directional control valve 19 which is connedted to the second pressure chamber 41 is formed as a double valve seat having a pistonshaped control valve member 45 which is guided in a housing bore 47 and is influenced on its one end face 48 by an electric operating magnet 49 attached to the housing 20 and comprises on its peripheral surface an annular cross piece 50 which separates a first annular groove-shaped recess 51 from a second annular groove-shaped recess 53, wherein the diameter of the annular cross piece 50 is larger than the 12 diameter of the valve member portions 55, 56 which define the two recess 51, 53 on the other side.

The annular end face of the annular cross piece 50 facing the end face 48 which is influenced by the operating magnet 49 changes in a conical manner from the outer diameter to the inner diameter corresponding to the diameter of the first recess 51 and thus forms a first conical valve sealing surface 57, which cooperates with a first valve seat 49 produced by virtue of a conical widening in diameter of the housing bore 47, wherein between the first valve seat 59 and the end of the first recess 51 remote from the annular cross piece 50 a first through-flow chamber 61 is formed between the wall of the housing bore 47 and the control valve member 45. The high pressure line 13 issues with respect to the common high pressure collecting chamber 7 into this first through-flow chamber 61 and the connection line 35 leads off from this site to the first pressure chamber 33 of the injection valve 17, wherein the connection line 35 remains continuously connect-xd to the high pressure line 13.

On the side remote from the operating magnet 49 the first valve seat 49 defines a second through-flow chamber 63, into which the connection duct 43 issues with respect to the second pressure chamber 41 of the injection valve 17 and which second through-flow chamber extends beyond the region of the second recess 53 as far as to a second housing-fixed valve seat 65, wherein this second valve seat 65 13 is formed by virtue of a conical reduction in cross-section of the housing bore 47 and cooperates with a second valve sealing surface 67 on the end face of the control valve member 45 remote from the operating magnet 49.

The second valve seat 65 is disposed in a filling piece 69 which receives a part of the housing bore 47 and which is clamped by way of a closure screw 71 on the housing 20. The part of the housing bore 47 located in the filling piece 69 changes in the form of a stepped bore into an axial blind bore 73 of a smaller diameter in the extension of the housing bore 47. The diameter of the valve member portion 55 protruding into filling piece 69 is slightly smaller than the diameter of the part of the housing bore 47 which guides the valve member portion 55, wherein the free cross- section is smaller in dimension than the orifice cross-section on the second valve seat 65 and thus forms a restrictor length.

However, it is also possible to guide the control valve inember 45, with its valve member portion 55 which is adjacent to the second valve sealing surface 67 in a tight-fitting manner in the housing bore 47 in the filling piece 69 and to render possible the passage of fuel by way of a longitudinal groove from the second through-flow chamber 63 into an inner annular groove, which is adjacent to the second valve seat 65 from the through-flow chamber, in the housing bore. From the axial blind bore 73, which forms a third through-flow chamber 74, leads off a 14 transverse bore 75, which is connected to the low pressure chamber 3 by way of a relief line 77 and by way of which the second through-flow chamber 63 can be relieved when the control valve member 45 has been raised from the second valve seat.

On its end facing the operating magnet 49 an anchor plate 81 is disposed by way of a damping device 101 on the control valve member 45 and cooperates with the operating magnet 49 [not illustrated in detail] which is attached to the housing 20 of the injection unit 15 by interposition ing an intermediate plate 85 in the axial extension of the housing bore 47. In so doing, the size of housing bore 47 increases in the region of the outlet with respect to the intermediate plate 85 and thus forms a spring chamber 87, in which is disposed a return spring 91, which is clamped between an annular disc of the intermediate plate 85 and a spring plate 89 on the control valve member 45 and which holds the control valve member 45 of the 3 port directional control valve 19 with its second valve sealing surface 67 in position on the second valve seat 65 when the operating magnet 49 is in a currentless state.

The operating magnet 49 is controlled by means of an electronic control device 93 which processes the operating parameters of the internal combustion engine to be supplied and the pressure control valve 9 can also be controlled by way of said control device.

Figure 2 shows an enlarged illustration of the damping device 101 which is formed in accordance with the invention and is disposed between the control valve member 45 and the anchor plate 81. By way of the damping device 101 the anchor plate 81 is mounted in a resiliently flexible and/or floating manner with respect to the control valve member 45. The damping device 101 comprises a resilient element 102 which is formed to be the same size as or smaller than the anchor plate 81. In a preferred manner it is provided that the resilient element 102 is formed in strip-like manner. In the outer edge region the resilient element 102 is fixedly connected to the anchor plate 81 by way of a releasable or non- releasable connection 115, such as, for example, a rivet connection or a screw connection, wherein distance discs 103 are disposed between the resilient element 102 and the anchor plate 81. The thickness of the distance disc 103 predetermines the spaced interval between the resilient element 102 and the anchor plate 81. The resilient element 102 is clamped in the middle region between two flexible elements 104, 105 by way of an attachment means 106 which is formed as a screw and said resilient element is fixed with respect to the control valve member 45. For this purpose the screw 106 -comprises a threaded portion 107 which engages into a threaded bore 110 of the control valve member 45. The threaded portion 107 is connected to a cylindrical shaft 108 having a larger diameter, whereby an annular portion 109 is formed which acts upon the flexible element 105 disposed between the resilient element 102 and the anchor plate 81 and fixes the underlying discs, formed as flexible elements 104 and 105, and the __I 16 resilient element 102 with respect to the control valve member 45.

The cylindrical shaft 108 and an adjoining screw head 111 of the attachment screw 106 is surrounded by a stepped through-going bore 112 of the anchor plate 81. The through-going bore 112 comprises a first bore 113 and a second bore 114 which have a larger diameter than the screw head 111 and the cylindrical shaft 108, wherein the diameter of the second bore 114 is smaller than the diameter of the screw head 111, so that a shoulder 116 is formed which engages behind an annular portion 117 of the screw head 111. The length of the cylindrical shaft 108 and the length of the second bore 114 are tailored to suit each other in such a manner that a spaced interval B is formed between the shoulder 116 and with [sic] the annular portion 117. Furthermore, the thickness of the distance disc 103 is greater than the thickness of the underlying disc 105, so that an intermediate space A is formed between the underlying disc 105 and the opposite-lying body edge of the anchor plate 81. The length of the shaft 108 is to be formed in dependence upon the desired spaced interval B and the desired spaced interval A.

The intermediate space A forms a resilient path and predetermines the damping in the event that the operating magnet 49 is switched to currentless and the control valve member 45 performs a closing movement, whereby the control valve member 45 moves with its second valve sealing surface 47 into position on the second valve seat 45. The spaced interval B forms a resilient path and/or the extent of the 17 damping in the event that an injection procedure is to take place and the electric operating magnet 49 is supplied with current by the control device 93, whereby against the force of the return spring 21. the control valve member 45 moves the first valve sealing surface 57 into position on the first valve seat 69.

By virtue of the size of the underlying discs 104 and 105 and by virtue of the thickness of the underlying discs 104, 105 and of the elasticity modulus of the underlying discs 104, 105 it is possible to predetermine the damping of the resilient element 102. Furthermore, it is necessary when adjusting the damping device 101 to take into consideration the masses of the anchor plate 81 and of the control valve member 45 which have been moved.

By virtue of the embodiment, illustrated in Figure 2, with respect to the underlying disc 105, which is larger than the underlying disc 104, the damping can be more flexible, as the injection procedure is terminated, during a closing movement of the control valve member 45 than during the opening movement of the control valve member 45 if the operating magnet 49 is supplied with current. Alternatively it can be provided that the underlying discs 104, 105 are the same size. Furthermore, it can also be provided that merely one underlying disc 104 or 105 can be provided depending upon the particular application. Furthermore, it is possible to influence the bouncing behaviour of the control valve member 45 by virtue of the thickness and the width of the 18 preferably rectangular resilient element 102.

It is understood that the damping device 101 can also be effective in only one direction of movement specific to the particular application, wherein either the intermediate space A or spaced interval B is only provided. Alternatively it can also be provided that instead of the attachment means 106, which is formed as a screw, further attachment possibilities can be provided, which render it possible for the resilient element 102 and where appropriate the flexible elements 104, 105 to be fixed.

The fuel-injection device in accordance with the invention functions in the following manner:

When the internal combustion engine is started-up the high pressure pump 1 delivers fuel from the low pressure chamber 3 into the high pressu re collecting chamber 7 and at this site builds up a high pressure fuel which can be adjusted by way of the pressure control valve 9.

This high pressure fuel is transferred by way of the high pressure lines 13 to the individual injection units 15 and continues at this site initially by way of the connection line 35 into the first pressure chamber 33 of the injection valve 17 and in the currentless state of the electric operating magnet 49, wherein the control valve member 45 of the 3 port directional valve 19 lies with its second valve sealing surface 67 on the second valve seat 65, said high pressure fuel continuing by way of the 19 first through-flow chamber 61 and the second through-flow chamber 65 on the 3 port directional valve 19 and by way of the connection duct 43 into the second pressure chamber 41 of the injection valve 17. In so doing, the injection valve member 21 is held, in the first pressure chamber 33 and with the support of the valve spring 39 on the valve seat 29 by virtue of the working surface on the piston 38, which working surface defines the second pressure chamber 41 and is larger than the working surface of the pressure shoulder 31, so that the injection valve 17 is closed.

If an injection procedure is to take place, the electric operating magnet 49 is supplied with current by the control device 93 and as a result thereof displaces the control valve member 45 of the 3 port directional control valve 19 against the force of the return spring 91 in position on the second stop thereof, i.e. the first valve sealing surface 57 moves into position on the first valve seat 59 and closes the connection between the first through-flow chamber 61, which is connected to the high pressure line 13, and the second through-flow chamber.63, which is connected to the second pressure chamber 41. During this adjusting movement the anchor plate 81 moves in a retarded manner by virtue of the resilient element 102. As a consequence, the valve sealing surface 57 comes into contact ina damped manner with the first valve seat 59, so that the valve is prevented from becoming unseated.

The anchor plate 81 can be deflected about the resilient path according to the spaced interval B, wherein the resilient path is selected in a preferred manner such that the shoulder 116 of the stepped through-going bore 112 does not move into position on the annular portion 117 of the screw head 111.

When the control valve member 45 is moved for the purpose of closing the first valve seat 59, the connection between the second through-flow chamber 63 with respect to the third through-flow chamber 74, which is connected to the relief line 77 and is formed by virtue of the blind bore 73, is opened simultaneously, so that the pressure in the second pressure chamber 41 is relieved. As a result of this discharge, which is restricted by virtue of the small through-cross-section in the region 55, out of the second pressure chamber 41 and as a result of the drop in pressure associated therewith, the force which acts in the opening direction in the first pressure chamber 44 upon the injection valve member 21 is now sufficient to raise said injection valve member from its valve seat 29 against the force of the valve spring 39, so that the injection valve 17 opens and the fuel is provided at the injection orifice 27 for injection If the injection procedure is to be terminated, the electric operating magnet 49 is once again switched to currentless by way of the control device 93, the control valve member 45 is once again moved with the first valve sealing surface 57 into position on the first valve seat 59 by the return spring 91, so that the second through-flow chamber 63 21 is once again connected to the high pressure line 13 and high pressure, which presses the injection valve member 21 with its sealing surface 25 on to the valve seat 29, is built up once again in the second pressure chamber 41 of the injection valve 17 and holds the injection valve closed against the force of the pressure in the first pressure chamber 33. Owing to the resilient path which is formed by virtue of the intermediate space A, the anchor plate 81 can be moved further in a closing movement after the closing movement has been performed so that a damped closing movement is achieved, whereby in turn the control valve member 45 is prevented from becoming unseated from the first valve seat 59. This damping is preferably softer since in this case larger adjusting forces are effective. This is achieved in particular by virtue of the fact that the flexible element 104 is smaller than the flexible element 105, so that it is possible for the resilient element 102 to be damped further or deflected to a greater extent.

Claims

22 CLAIMS

1. A fuel-injection unit, which comprises in each case at least one injection valve, which protrudes into the combustion chamber of an internal combustion engine and has an injection valve member which, for the purpose of controlling the injection procedure, cooperates with a valve seat and comprises a pressure surface which lies in a first pressure chamber and is influenced in the opening direction by virtue of the pressure in the first pressure chamber, and said injection valve member comprises on its rear end remote from the valve seat a second pressure chamber which is influenced at least indirectly by the pressure, wherein the first pressure chamber is continuously connected to a high pressure collecting chamber by way of a connection line to the high pressure line, and comprising a 3 port directional control valve which is controlled by an electric control device by means of an operating magnet and has a control valve member which comprises two sealing surfaces cooperating in each case with a valve seat and which in its one position moves into position with the one sealing surface on to the one valve seat and in so doing cl oses the connection of the high pressure line to the second pressure chamber and opens the connection of the second pressure chamber to a relief line and in its other position opens and/or closes this connection, wherein the control valve member defines in its one position, which produces the connection with respect to the second pressure chamber to the relief line, a restricted cross- -. ' - 23 section, and in its other position produces an unrestricted connection, which is free in both directions of flow, from the second pressure chamber to the high pressure line, and wherein, between an end, which is directed towards the operating magnet, of the control valve member and an anchor plate, which is allocated to the control valve member, there is provided a damping device which damps a closing procedure of the control valve member in at least in one direction of movement of the control valve member.

2. A fuel-injection unit according to claim 1, wherein the damping device comprises a resilient element which on the one side is fixedly connected to the control valve member and on the other side is fixedly connected to the anchor plate.

3. A fuel-injection unit according to claim 2, wherein the resilient element is formed as a spring plate which is disposed substantially parallel with the anchor plate and is disposed on the control valve member by means of attachment means, preferably a screw.'

4. A fuel-injection unit according to claim 3, wherein the outer edge region the spring plate is attached to the anchor plate by means of connection means, wherein at least one distance element is provided between the anchor plate and the spring plate.

5. A fuel-injection unit according to any of claims 2 to 4, wherein at least one flexible element is disposed in parallel with the resilient element and is positioned with'respect to the control valve member by 24 way of attachment means.

6. A fuel-injection unit according to claim 5, wherein the resilient element is disposed between two flexible elements on the control valve member.

7. A fuel-injection unit according to claim 3, wherein the thickness of the distance element is greater than the thickness of the flexible element disposed between the resilient element and the anchor plate and an intermediate space formed thereby can adjust the resilient path in one direction of movement of the control valve member.

8. A fuel-injection unit according to any of claims 3 to 7, wherein the anchor plate comprises a stepped through-going bore for the purpose of receiving the attachment means and the diameter of a first bore and a second bore are larger than the attachment means disposed therein.

9. A fuel-injection unit according to any of claims 3 to 8, wherein the attachment means is formed as a screw and comprises a' cylindrical shaft which is connected to a screw head, is smaller in diameter and in turn becomes a threaded portion which has a smaller diameter, wherein the length of the shaft region is greater than said intermediate space and the length of the second bore.

10. A fuel-injection unit according to claim 8 or 9, wherein the stepped through-going bore comprises a shoulder which with respect to an annular portion formed between the shaft and the screw head comprises a spaced interval, whereby a resilient path can be adjusted for a second direction of movement of the control valve member.

11. A fuel-injection unit according to any of claims 2 to 10, wherein the rigidity of the resilient element can be adjusted in dependence upon the size of the flexible elements.

12. A fuel-injection unit according to any of claims 2 to 11, wherein the rigidity of the resilient element can be adjusted by virtue of the thickness of the resilient element and in particular by virtue of the thickness of the flexible elements.

13. A fuel-injection unit according to any of the preceding claims, wherein the resilient path of the control valve member can be adjusted by virtue of the size of said intermediate space and said spaced interval.

14. A fuel-injection unit according to any of the preceding claims, wherein the bouncing behaviour of the control valve member can be adjusted by virtue of the mass of the anchor plate and of the damping device and also by virtue of the free resilient path of said intermediate space and of said spaced interval.

15. A fuel-injection unit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.