Title of Invention

FUEL-INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES

Abstract

ABSTRACT (IN/PCT/2002/01374/CHE) 'FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES' A fuel injection system for internal combustion engines with a fuel injection valve, which is supplied by a high-pressure fuel source and has a valve member which can be moved by the pressure in a pressure chamber formed in the fuel injection valve and thereby controls at least one injection opening which can be corrected to the pressure chamber, and with a control valve which has a control-valve member which, in a first position, separates a first pressure space connected continuously to the high-pressure fuel source food a feed hole leading to the pressure chamber and, in a second position, opens the connection between the high-pressure fuel source and the pressure chamber, characterized in that, between the high-pressure fuel source and the first pressure space, there is a line, which has a restrictor, leading to an otherwise closed damping space; said damping space is arranged within the fuel injection valve. Figure 1

Full Text

Prior art The invention takes as its starting point a fuel injection system for internal combustion engines of the generic type of Patent Claim 1. A fuel injection system of this kind is known from publication DE 197 01 879 Al and comprises a fuel tank, from which fuel is pumped into a high pressure collecting space by a high-pressure pump. A predetermined high fuel pressure is maintained in the high-pressure collecting space by a regulating device. A number of high-pressure feed lines corresponding to the number of combustion chambers in the internal combustion engine each lead from the high-pressure collecting space to a respective fuel injection valve, it being possible for the fuel injection valve to be connected to the high-pressure line by a control valve. For reasons of space, the control valve and the fuel injection valve are arranged in one housing. In this arrangement, the fuel injection valve comprises a valve needle, which is guided in a hole and is surrounded in the region facing the combustion chamber by a pressure space. The valve needle has formed on it a pressure surface, which is acted upon by the fuel in the pressure space, with the result that, when a certain opening pressure in the pressure space is reached, the valve needle performs a longitudinal motion against a closing force and thus exposes at least one injection opening, through which fuel passes out of the pressure space into the combustion chamber of the internal combustion engine. The control valve of the fuel injection system is designed as a 3/2-way valve, which, in one position, connects the high-pressure collecting space to the pressure chamber of the fuel injection valve and, in a second position, interrupts the connection to the high-pressure collecting space and connects the pressure chamber to a leakage-oil space formed in the valve Doay, wnicn leaKage-oil space is connected by a line to the fuel tank, with the result that a low fuel pressure prevails in the leakage-oil space at all times. If the control valve switches from the closed position to the open position, a pressure wave is produced, which passes through the feed passage into the pressure space and there leads to an additional increase in pressure, that is to say that the injection of the fuel takes place at a pressure which is significantly higher than the pressure in the high-pressure collecting space. High injection pressures are thereby obtained with a moderate high pressure in the high-pressure collecting space and in those parts of the fuel injection system which carry the high fuel pressure. Since the fuel in the feed lines is in motion through the openened control valve, it is stopped abruptly when the control valve is closed, with the result that the kinetic energy of the fuel is converted into compression work. This gives rise to pressure oscillations, making accurate proportioning and exact metering in of the injection quantity more difficult for a second injection immediately following the first injection since, owing to the pressure oscillations, the state at the control valve is not precisely known. The present invention is therefore based on the object of designing a fuel injection system which allows accurate proportioning of the injection quantity and main, pilot and postinjections that can be offset accurately. Advantages of the invention In contrast, the fuel injection system according to the invention with the characterizing features of patent claim 1 has the advantage that the pressure oscillations which occur upon closure of the control valve, i.e. upon interruption of the connection to the high-pressure collecting space, are damped through the connection of the first pressure space or high-pressure feed line to a damping space via a restrictor, and thus die away quickly. After closure, the control valve thus returns very quickly to a steady state, enabling a second injection to be performed at a short time interval with respect to the preceding injection and, at the same time, enabling the injection quantity for the second injection to be controlled very accurately. The control valve is a 3/2-way valve in a control-valve body and contains a control-valve member which is guided in a longitudinally displaceable manner in a control hole. Two pressure spaces are formed in the control hole by means of a radial expansion of the control hole, the first pressure space being connected to the high-pressure collecting space and the second pressure space being connected to the pressure chamber formed in the fuel injection valve. In the closed position of the control-valve member, the connection from the first to the second pressure space is interrupted in the first position, and the second pressure space and hence the pressure chamber are connected to a leakage-oil space and are thus unpressurised. In the open position of the control-valve member, the connection from the first to the second pressure space is opened and the connection between the second pressure space and the leakage-oil space is interrupted, with the result that the high-pressure collecting space is connected to the pressure chamber. The first pressure space is connected to a damping space via a restrictor, with the result that pressure oscillations of the type which occur in the first pressure space and also in the high-pressure feed line during the opening and closure of the control valve are damped. Through appropriate configuration of the restrictor, the damping characteristic can be set in such a way that pressure oscillations in the pressure space die away completely after just a few oscillation periods. In a first advantageous refinement of the subject matter of the invention, the damping space is designed as a hole, which extends in the valve-holding body, parallel to its longitudinal axis. As a result, the damping space can be formed in the already known fuel injection valves without modifications and without the need to change the outside diameter of the fuel injection valve. In another advantageous refinement, the valve-holding body is clamped axially against the control-valve body with a washer in between. The hole forming the damping space extends partially in the control-valve body, through the washer and, for the most part, in the valve-holding body. The restrictor is formed in the washer, with the result that it is possible to adapt the fuel injection valve to the requirements of the respective by swapping the washer for one with a different restrictor without the need to make design changes to the rest of the fuel injection valve. In another advantageous refinement of the subject matter of the invention, the damping space comprises two mutually parallel hole sections, which both extend in the valve-holding body. The two hole sections of the damping space are connected to one another by a transverse passage, making it possible to achieve a shorter valve-holding body with the same volume of the restriction hole. In a further advantageous refinement, the two hole sections of the damping space are connected by a transverse passage which is arranged in a washer arranged between the valve-holding body and the valve body. This refinement eliminates a transverse connection between the hole sections within the valve- holding body, which can be manufactured only in a relatively involved manner, e.g. with the aid of an end mill. The formation of the transverse connection in the washer makes it possible to form both hole sections of the damping space starting from one of the ends of the valve-holding body. In another advantageous refinement of the subject matter of the invention, a closing valve, which opens the connection from the first pressure space to the damping space only when damping is desired, is arranged between the damping space and the first pressure space. The additional increase in pressure when the control valve opens, which is the aim for injection at the highest possible pressure, is somewhat reduced by the continuous connection of the first pressure space to the damping space. The closing valve therefore interrupts the connection of the first pressure space to the damping space during the opening phase of the control valve. On completion of the injection, the closing valve is opened, ensuring that the pressure waves in the first pressure space are damped quickly, as before. By means of this closing valve, an optimum injection pressure and, at the same time, damping of the pressure oscillations is thus obtained, making possible exact proportioning of the injections. In another advantageous refinement, the closing valve is controlled by the pressure in the second pressure space. When the control valve is open, the pressure prevailing in the second pressure space is at least approximately the same as that in the first pressure space, and the closing valve is closed by this pressure. If the control valve closes the connection from the first to the second pressure space, the pressure in the second pressure space falls, and, as a result, the closing valve opens the connection from the first pressure space to the damping space. The damping of the pressure oscillation then take place in the manner already aescriiDed, Control by the pressure in the second pressure space renders an additional electronic system for controlling the closing valve superfluous. In another advantageous refinement of the subject matter of the invention, the control-valve body is manufactured from a hard steel, while the valve-holding body, in which the damping space is formed, is manufactured from a relatively soft steel. The control valve, which contains sealing surfaces that are exposed to severe stress, is arranged in the control-valve body. Formation by means of a hard steel reduces wear in the region of the valve seat of the control valve. To form the valve-holding body, on the other hand, a soft steel is advantageous since there are no seating or sealing surfaces provided at this point, and severe mechanical stress thus does not occur. The cavity forming the damping space can be formed economically and quickly in the soft steel. Further advantages and advantageous refinements of the subject matter of the invention can be found in the drawing, the description and the claims. In the drawing Various exemplary embodiments of the fuel injection system according to the invention are illustrated in the drawing, in which: Drawing Figure 1 shows a fuel injection valve in longitudinal section and the schematically illustrated construction of the high-pressure fuel supply. Figure 2 shows an enlargement of Figure 1 in the region of the control valve. Figure 3 shows the same detail as Figure 2 of another exemplary embodiment, Figure 4 shows another exemplary embodiment of a fuel injection system illustrated in the same way as in Figure 1, Figure 5 shows a cross section through the fuel injection valve illustrated in Figure 4 along line of section V-V, Figure 6 shows the schematically illustrated construction of another exemplary embodiment of a fuel injection system according to the invention, and Figure 7 shows a detail from Figure 6 of another exemplary embodiment. Description of the exemplary embodiments A fuel injection valve according to the invention is shown in longitudinal section in Figure 1, forming a fuel injection system together with the schematically illustrated high-pressure fuel supply and the leakage-oil system, likewise illustrated only schematically. Fuel is fed from a fuel tank 1, via a fuel line 3, to a high-pressure pump 5, which pumps the fuel under high pressure into a high-pressure collecting space 10 via a feed line 7. A predetermined high fuel pressure is maintained in the high-pressure collecting space 10 by means of a regulating device (not shown in the drawing). Leading off from the high-pressure collecting space 10 are high-pressure feed lines 12, each of which is connected to a fuel injection valve 15, of which one is illustrated in the drawing by way of example. The fuel injection valve 15 is of multi-part construction and comprises a control-valve body 17, in which a control valve 50 is arranged. A valve-holding body 22 is clamped axially against the control-valve body 17 by means of a clamping nut 20, with a washer 19 in between. At the other end of the valve-holding body 22, which faces the combustion chamber, the valve-holding body 22 rests via a valve washer 24 against a valve body 25, which valve body 25 is clamped against the valve-holding body 22 by means of a clamping nut 27. Formed in the valve body 25 is a hole 30, at the combustion-chamber end of which is formed an essentially conical valve seat 36, in which at least one injection opening 38 is arranged. Arranged in the hole 30 is a piston-shaped valve needle 32, which is guided in a sealing manner in the section of the hole 30 that is remote from the combustion chamber and which tapers toward the combustion chamber, forming a pressure surface 33. At its combustion-chamber end, the valve needle 32 merges into an essentially conical valve-sealing surface 34, which interacts with the valve seat 36 and thus closes the injection opening 38 in the closed position, i.e. when resting against the valve seat 36. A pressure chamber 31, which is continued as far as the valve seat 36 as an annular passage surrounding the valve needle 32, is formed at the level of the pressure surface 33 by a radial expansion of the hole 30. The pressure chamber 31 can be connected to the high-pressure collecting space 10 and thus filled with fuel under high pressure via a feed hole 28 extending in the valve body 25, the valve washer 24, the valve-holding body 22, the washer 19 and the control-valve body 17. A central opening 83, which connects the hole 30 to a spring space 40 formed in the valve-holding body 22, is formed in the valve washer 24. In this arrangement, the spring space 40 is embodied as a hole and is arranged coaxially with the hole 30. The central opening 83 has a smaller diameter than the hole 30 that guides the valve needle 32, with the result that a stop shoulder 35 is formed at the transition from the valve body 25 to the valve washer 24. The axial distance between the opposite end of the valve needle 32 from the combustion chamber and the stop shoulder 35 of the valve washer 24 in the closed position of the fuel injection valve defines the opening stroke of the valve needle 32. At its end remote from the combustion chamber, the valve needle 32 merges into a pressure pin 37, which is arranged coaxially with the valve needle 32 and is arranged in the central opening 83 of the valve washer 24. The pressure pin 37 merges into a spring plate 42, which is arranged in the spring space 40 and between which and the opposite end of the spring space 40 from the combustion chamber a closing spring 44 designed as a helical compression spring is arranged under compressive prestress. In this arrangement, the compressive prestress of the closing spring 44 can be determined by means of the thickness of a shim 45, which is arranged between the closing spring 44 and the opposite end of the spring space 40 from the combustion chamber. Via the spring plate 42 and the pressure pin 37, the force of the closing spring 44 presses the valve-sealing surface 34 of the valve needle 32 against the valve seat 36 and thereby closes the injection opening 38. The spring space 40 is connected to the fuel tank 1 via a leakage-oil line 69, ensuring that fuel that penetrates into the spring space 40 is carried away to the fuel tank 1, for which reason there is always a low fuel pressure prevailing in the spring space 40. At its end remote from the combustion chamber, the spring space 40 merges into a through hole 46, which is arranged coaxially with the hole 30 and the spring space 40 and extends into a discharge space 76 formed in the washer 19. An enlarged representation of the control valve 50 is shown in longitudinal section in Figure 2. The control-valve hole 52 is divided into a sealing section 152 and a guiding section 252 of smaller diameter. At the end remote from the combustion chamber, the control-valve hole 52 opens into a leakage-oil space 66 formed in the control-valve body 17 and, at its other end, it opens into the discharge space 76, which is connected via the through hole 46 to the spring space 40. By means of a radial expansion of the control-valve hole 52, a first pressure space 57 is formed, this being connected via a feed passage 13 formed in the control-valve body 17 to the high-pressure feed line 12 and hence to the high-pressure collecting space 10. Starting from the first pressure space 57, a second pressure space 58 is formed on the side facing the valve-holding body 22 by a further radial expansion of the control-valve hole 52. The feed hole 28, which connects the second pressure space 58 to the pressure chamber 31, opens into the second pressure space 58. An essentially conical control-valve seat 56 is formed on the wall of the control-valve hole 52 at the transition from the first pressure space 57 to the second pressure space 58. Arranged in a longitudinally displaceable manner in the control-valve hole 52 is a control-valve member 54, which is guided in a sealing manner in the sealing section 152 of the control-valve hole 52. From the sealingly guided section of the control-valve member 54, the control-valve member 54 tapers toward the valve-holding body 22 to form a control-valve sealing surface 55, which is of essentially conical design and interacts with the control-valve seat 56. The control-valve member 54 extends through the second pressure space 58 as far as the discharge space 76 formed in the washer 19, where the control-valve member 54 merges into a control section 62, which is of cylindrical design and has a diameter that is only slightly smaller than the diameter of the guiding section 252 of the control-valve hole 52. Between the control section 62 and the second control space 58, the control-valve member 54 is guided in the guiding section 252 of the control-valve hole 52, recesses 60 being formed on the control-valve member 54, allowing fuel to flow past the guided section of the control-valve member 54. In the closed position of the control-valve member 54, that is to say when the control-valve sealing surface 55 is resting against the control-valve seat 56, the annular end face 78 of the control section 62, the end face facing the control-valve body 17, is at an axial distance from the start of the control-valve hole 52 that corresponds to a discharge stroke hg. At the end remote from the valve-holding body 22, the control-valve member 54 merges into a magnet armature 67, which is arranged in the leakage-oil space 66, the leakage-oil space 66 being connected via a leakage-oil line 73 to the fuel tank 1. In the closed position of the control-valve member 54, the magnet armature 67 is at an axial distance hg from an electromagnet 65, which is likewise arranged in the leakage-oil space 66. The electromagnet 65 surrounds a valve spring 68, which is arranged under prestress between a fixed-location stop (not shown in the drawing) and the magnet armature 67 and acts upon the control-valve member 54 in the direction of the closed position. The electromagnet 65 is arranged at a fixed location in the leakage-oil space 66 and can exert an attractive force on the magnet armature 67 through appropriate energization, the magnet armature thereby being pulled in the opening direction of the control-valve member 54 until it comes to rest against the electromagnet 65. This opening-stroke motion of the control-valve member 54 takes place against the closing force of the valve spring 68, with the result that the control-valve member 54 is pushed back into the closed position by the valve spring 68 when the energization of the electromagnet 65 is removed. Also opening into the first pressure space 57 in addition to the feed passage 13 is a line designed as a connecting passage 71. The connecting passage 71 extends at an angle to the longitudinal axis of the control-valve member 54 as far as the washer 19. Formed in the washer 19 is a restrictor 72, via which the connecting passage 71 is connected to a damping space 70 formed in the valve-holding body 22. In this arrangement, the damping space 70 is embodied as a pocket hole, which extends parallel to the longitudinal axis 23 of the valve-holding body 22 and to the through hole 46. The length of the pocket hole forming the damping space 70 can vary, depending on the desired volume of the damping space 70. It is also possible to form the pocket hole forming the damping space 70 with different diameters. Another exemplary embodiment of the fuel injection system according to the invention is illustrated in Figure 3, the same detail enlargement being illustrated as in Figure 2. Its operation and construction correspond exactly to those of the exemplary embodiment illustrated in Figure 2, but here the damping space 70 is formed by a recess in the control-valve body 17, the recess being of cylindrical design and extending parallel to the control-valve hole 52. Close to the first pressure space 57, the damping space is connected to the feed passage 13 via a line designed as a connecting passage 71. Arranged within the connecting passage 71 is a restrictor 72, which damps the flow of fuel through the connecting passage 71. Since the damping space 70, together with the connecting passage 71 and the restrictor 72, are arranged within the control-valve body 17, there is no need to modify the construction of the valve-holding body 22 as compared with the fuel injection valve without a damping space 70. Figure 4 illustrates another exemplary embodiment of a fuel injection system according to the invention, only the design of the damping space 70 having been modified as compared with Figure 1. In this exemplary embodiment, the damping space 70 is not designed as a simple pocket hole but is divided into two hole sections 170, 270, which are formed parallel to one another in the valve-holding body 22. The first hole section 170 of the damping space 70 extends from one end of the valve-holding body 22 to the other end, i.e. from the washer 19 to the valve washer 24. In the valve washer 24, the first hole section 170 of the damping space 70 opens into a transverse connection 85, which has an oval or kidney-shaped form in cross section, as Figure 5 shows in a cross section of the valve washer 24. Formed in the valve-holding body 22, starting from the end of the valve-holding body 22 facing the combustion chamber, is a second hole section 270 of the damping space 70, this hole section being embodied as a pocket hole and being arranged rotated by an angle a about the longitudinal axis 23 of the valve-holding body 22 relative to the first hole section 170. The transverse connection 85 in the valve washer 24 connects the two hole sections 170 and 270 to one another, so that together they form the damping space 70. Figure 5 shows a cross section through the fuel injection valve along the line V-V in Figure 4. Two further centering-pin holes 88 and 89 are formed in the valve washer 24 in addition to the central opening 83 and the transverse connection 85. During the assembly of the fuel injection valve, centering pins are inserted into these centering-pin holes 88 and 89, entering corresponding holes in the valve-holding body 22 and the valve body 25 and thereby ensuring exact positioning of these bodies relative to one another. The fuel injection system illustrated in Figure 1 to 5 operates as follows: the high-pressure pump 5 pumps fuel out of the fuel tank 1 through the fuel line 3 and, via a high-pressure feed line 7, into the high-pressure collecting space 10. A predetermined high fuel pressure level is maintained in the high-pressure collecting space 10 by means of a regulating device (not shown in the drawing) . In the case of the high-pressure collecting spaces that are customary nowadays, the pressure level is up to 140 MPa. From the high-pressure collecting space 10, the fuel is carried through the high-pressure feed lines 12 to the fuel injection valves 15. In the fuel injection valve 15, the fuel passes through the feed passage 13 into the first pressure space 57. At the beginning of the injection cycle, the control valve 50 is in the closed position, that is to say the electromagnet 65 is not energized and the control-valve sealing surface 55 of the control-valve member 54 is pressed against the control valve 56 by the valve spring 68 and closes the first pressure space 57 relative to the second pressure space 58. The second pressure space 58 is connected via the recesses 60 to the discharge space 76, which is connected by the through hole 4 6 to the spring space 40, which is connected to the fuel tank 1. As a result, a low fuel pressure corresponding to the pressure in the fuel tank 1 prevails in the second pressure space 58 and, by way of the feed hole 28, which starts from the second pressure space 58, also in the pressure chamber 31. Owing to the connecting passage 71, the pressure prevailing in the damping space 70 is the same as that in the first pressure space 57 and hence also that in the high-pressure collecting space 10. If an injection is to take place, the electromagnet 65 is energized, with the result that the magnet armature 67 moves toward the electromagnet 65 against the force of the valve spring 68. Owing to the movement of the magnet armature 67, the control-valve member 54 also moves, and the control-valve sealing surface 55 rises from the control-valve seat 56. As a result, the first pressure space 57 is connected to the second pressure space 58. Until the discharge stroke ha has been traversed by the control-valve member 54, the second pressure space 58 remains connected to the discharge space 76 via the recesses 60, with the result that, at the beginning of the stroke motion of the control-valve member 54, fuel flows out of the first pressure space 57 into the second pressure space 58 and, from the latter, into the discharge space 76. As a result, the quantity of fuel which is under high pressure in the feed passage 13 is set in motion and thus receives kinetic energy. After executing the discharge stroke ha, the control section 62 enters the control-valve hole 52 and thus closes the second pressure space 58 with respect to the discharge space 76. The fuel in the feed passage 13, which is already in motion, now flows into the feed hole 28 and on into the still-closed pressure chamber 31, where the kinetic energy of the fuel is converted into a compression work. This is associated with an increase in the pressure in the pressure chamber 31, and a significantly higher pressure than in the high-pressure collecting space 10 is obtained. This pressure can be several tens of MPa above the pressure in the high-pressure collecting space 10. The pressure in the pressure chamber 31 results in a hydraulic force on the pressure surface 33 of the valve needle 32, which is thereby moved away from the combustion chamber in the axial direction against the force of the closing spring 44. As a result, the valve-sealing surface 34 rises from the valve seat 36 and the injection openings 38 are exposed, with the result that fuel flows out of the pressure chamber 31, past the valve needle 32, to the injection openings 38 and, from there, is injected into the combustion chamber of the internal combustion engine. In this process, the opening-stroke motion of the valve needle 32 is continued until its end remote from the combustion chamber is resting against the stop shoulder 35 of the valve washer 24. If the injection is to be ended, the electromagnet 65 is no longer energized, with the result that the valve spring 68 pushes the control-valve member 54 back into the closed poisition. In the course of the closing motion of the control-valve member 54, the control section 62 reemerges from the guiding section 252 of the control-valve hole 52 and connects the second pressure space 58 and hence, via the feed hole 58, also the pressure chamber 31 to the discharge space 76, which is connected to the leakage-oil system. The pressure chamber 31 is thus relieved and the force of the closing spring 44 on the valve needle 32 exceeds the hydraulic force on the pressure surface 33, and the valve needle 32 returns to the closed position. Since the fuel in the feed passage 13 still has kinetic energy, this kinetic energy is converted into compression work after the closure of the control valve 50, with the result that the pressure in the first pressure space 57 rises. Owing to this additional increase in pressure, the pressure prevailing in the first pressure space 57 is higher than in the damping space 70, with the result that fuel now flows out of the first pressure space 57, through the connecting passage 71 and the restrictor 72 into the damping space 70, where the pressure is thereby increased accordingly. The pressure wave flowing in the damping space 70 thus lowers the pressure in the first pressure space 57 and increases the pressure in the damping space 70 until the pressure in the damping space 70 is higher than in the first pressure space 57. Some other fuel now flows back out of the damping space 70 through the restrictor 72 and the connecting passage 71 into the first pressure space 57, where the pressure accordingly rises again. This pressure oscillations is damped by the restrictor 72, with the result that the pressure oscillations die down after a small number of oscillations, in contrast to fuel injection systems without corresponding damping, and a constant pressure again prevails in the first pressure space 57, this pressure corresponding to the pressure in the high-pressure collecting space 10. The degree of damping can be adapted to the requirements of the fuel injection valve by means of the cross section of the restrictor 72 and the volume of the damping space 70. Figure 6 illustrates another exemplary embodiment of the fuel injection system according to the invention as a schematic block diagram. As in the previous exemplary embodiment, the mode of operation of the control valve 50 is that of a 3/2-way valve, which connects the first pressure space 57, the second pressure space 58 and the leakage-oil line 69 accordingly. The first pressure space 57 is connected to the damping space 70 via a connecting passage 71 and a restrictor 72, a closing valve 92 being arranged between the restrictor 72 and the damping space 70 in this exemplary embodiment. The closing valve 92 is controlled by the force of a spring 94 and the pressure in the second pressure space 58, which acts on the closing valve 92 via a connecting line 96. If the fuel pressure prevailing in the second pressure space 58 is high enough, exerting a larger force on the closing valve 92 than the spring 94, the closing valve 92 will interrupt the connecting passage 71, and the damping space 70 will no longer be connected to the first pressure space 57, with the result that a pressure oscillation occurring in the first pressure space 57 will no longer be damped. If the fuel pressure in the second pressure space 58 is correspondingly low, as is the case when the control valve 50 is closed, the force of the spring 94 is greater than the force of the fuel pressure in the second pressure space 58, and the closing valve 92 opens the connection from the first pressure space 57 to the damping space 70. The advantage of the closing valve 92 is that pressure oscillations in the first pressure space 57 are damped only when the control valve 50 is closed, i.e. when no injection is taking place. If the first pressure space 57 is connected continuously to the damping space 70 via the restrictor 72, the desired pressure surge at the start of injection will also be damped somewhat, with the result that the maximum achievable additional increase in pressure in the pressure chamber 31 will be somewhat lower than in the case of a closed first pressure space 57 that otherwise does not have any damping. Thanks to the closing valve 92, a higher injection pressure is thus obtained for the same pressure in the high-pressure collecting space 10. In this arrangement, the closing valve 92 is advantageously likewise formed in the control-valve body 17, thus continuing to allow a compact construction for the fuel injection system and ensuring that the operation of the closing valve 92 is not delayed by an unnecessarily long connecting line 96. In addition to the arrangement of the restrictor 72 in the washer 19, provision can also be made to form the restriction in the control-valve body 17 or in the valve-holding body 22. For this purpose, the washer 19 can be omitted, thus eliminating one high-pressure sealing surface. In this case, the discharge space 76 is accordingly arranged in the valve-holding body 22. Provision can furthermore be made to form the damping space 70 by means of two hole sections 170, 270, although the connection between the hole sections 170, 270 is not formed in the valve washer 24 but in the valve-holding body 22. This gives a damping space that is at least approximately U-shaped in longitudinal section. A damping space of this kind can be produced with the aid of an end mill. Figure 7 shows, in a fragmentary view a further exemplary embodiment of the fuel injection system shown in Figure 6. Here, provision is made to control the closing valve 92 directly, with the aid of an electric actuator 102 activated by a control unit 100 for example, instead of by means of the pressure in the second pressure space 58. One possible input variable among others for the control unit is the pressure in the second pressure space 58, the pressure being measured by means of a sensor element 101. Instead of forming the damping space 70 as a hole, provision can furthermore also be made to form any desired cavity in the valve-holding body 22 and to connect it to the first pressure space 57 via a restricted connection. A damping space of this kind can be adapted in an optimum manner to the space conditions of the valve-holding body 22. Moreover, it is also possible to form the damping space 70 in the control-valve body 17, thereby eliminating a corresponding high-pressure sealing surface, as formed between the washer 19 and the valve-holding body 22, on the one hand, and the control-body 17 and the washer 19, on the other hand. Provision can furthermore be made to control the control valve 50 directly with the aid of an electromagnet, rather than in the way illustrated in the exemplary embodiments. As an alternative, the control-valve member 54 can be controlled by means of a device which bring the control-valve member 54 into the open and/or closed position with the aid of hydraulic forces. The control-valve seat 56 of the control valve 50 is subjected to high mechanical loading when the control-valve sealing surface 55 lands during the longitudinal motion of the control-valve member 52. It is therefore necessary to manufacture the control-valve body 17 from a hard, wear-resistant steel. On the other hand, forming the damping space 70 as a pocket hole in the valve-holding body 22 is possible only with a considerable outlay if the latter is made of hard steel. Since there are no mechanically highly stressed surfaces in the valve-holding body 22, the valve-holding body 22 can be manufactured from a relatively soft steel in which holes can be formed easily. WE CLAIM: 1. A fuel injection system for internal combustion engines with a fuel injection valve, which is supplied by a high-pressure fuel source and has a valve member (32) which can be moved by the pressure in a pressure chamber (31) formed in the fuel injection valve and thereby controls at least one injection opening (38) which can be connected to the pressure chamber (31) and with a control valve (50), which has a control-valve member (54) which, in a first position, separates a first pressure space (57) connected continuously to the high-pressure fuel source from a feed hole (28) leading to the pressure chamber (31) and, in a second position, opens the connection between the high-pressure fuel source and the pressure chamber (31), characterized in that, between the high-pressure fuel source and the first pressure space (57), there is a line (71), which has a restrictor (72), leading to an otherwise closed damping space; said damping space (70) is arranged within the fuel injection valve. 2. The fuel injection system as claimed in claim 1, wherein the line (71) leads from the first pressure space (57) to the damping space (70). 3. The fuel injection system as claimed in claim 1, wherein the fuel injection valve has a control-valve body (17), a valve-holding body (22) and a valve body (25), the control-valve body (17) and the valve body (25) being arranged at opposite ends of the valve-holding body (22), and the control valve (50) being arranged in the control-valve body (17), and the valve member (32) being arranged in the valve body (25). 4. The fuel injection system as claimed in claim 3, wherein the damping space (70) is formed in the control-valve body (17). 5. The fuel injection system as claimed in any of the preceding claims, wherein a closing valve (92), which controls the opening of the line (71) leading to the damping space (70), is arranged in said line (71). 6. The fuel injection system as claimed in claim 5, wherein the closing valve (92) is controlled by the hydraulic pressure in the feed passage (28). 7. The fuel injection system as claimed in claim 5, wherein the closing valve (92) opens the connection from the first pressure space (57) to the damping space (7) at a certain opening pressure in the feed passage (28), and closes it when this opening pressure is undershot. 8. The fuel injection system as claimed in claim 5, wherein the closing valve (92) is actuated by a controllable electric actuator (102). 9. The fuel injection system as claimed in any of the preceding claims, wherein the high-pressure fuel source is a high-pressure collecting space (10) ("common rail").

Documents:

in-pct-2002-1374-che abstract-duplicate.pdf

in-pct-2002-1374-che abstract.jpg

in-pct-2002-1374-che abstract.pdf

in-pct-2002-1374-che claims-duplicate.pdf

in-pct-2002-1374-che claims.pdf

in-pct-2002-1374-che correspondence-others.pdf

in-pct-2002-1374-che correspondence-po.pdf

in-pct-2002-1374-che description (complete)-duplicate.pdf

in-pct-2002-1374-che description (complete).pdf

in-pct-2002-1374-che drawings.pdf

in-pct-2002-1374-che form-1.pdf

in-pct-2002-1374-che form-18.pdf

in-pct-2002-1374-che form-26.pdf

in-pct-2002-1374-che form-3.pdf

in-pct-2002-1374-che form-5.pdf

in-pct-2002-1374-che petition.pdf