FUEL INJECTION VALVE WITH A SLIDE VALVE FOR INTERNAL COMBUSTION ENGINES

Description

[0001] The present invention relates to a fuel injection valve for intermittent fuel injection into the combustion chamber of an internal combustion engine according to the preamble of claim 1.

[0002] A fuel injector of this type is known from document EP 1 273 791 A2. The Fig. 6The fuel injector shown in this document has a slide valve body which is guided in a hollow cylindrical sleeve with a tight sliding fit and which has a first end face facing a control chamber and a second end face opposite this first end face. A throttle inlet runs from the second end face to the first end face, with the throttle inlet having a throttle constriction at a distance from the second end face and at a further distance from the first end face. Furthermore, a throttle passage runs from the first end face to the second end face and has a further throttle constriction at correspondingly equal distances to the throttle inlet. A throttle inlet which runs in the radial direction and opens into the throttle passage is formed on the slide valve body.A stationary control body, with its front side facing the slide valve body, forms a slide valve seat that interacts with the second end face of the slide valve body. The control body has a control passage extending from the front side, which is permanently fluidically connected to the throttle passage and can be connected to and separated from a low-pressure chamber by means of a pilot valve. The throttle passage and the control passage are permanently fluidically connected to the high-pressure chamber via the throttle inlet. When the slide valve body is lifted off the slide valve seat, a gap is formed through which the throttle passage and the control passage, as well as the throttle inlet, are additionally fluidically connected to the high-pressure chamber.

[0003] The eccentrically designed adhesion surface between the second end face of the slide valve body and the front face of the control body leads to a delay in the response of the fuel injector to terminate an injection process. Furthermore, manufacturing is complex because the slide valve body must be precisely designed and, in particular, the throttle constrictions of the throttle inlet, throttle passage, and throttle inlet must be manufactured with very tight tolerances.

[0004] The document DE 11 2016 002905 T5 discloses a known fuel injector.

[0005] It is therefore an object of the present invention to further develop a generic fuel injection valve in such a way that the delay in response is minimized with simple production.

[0006] This object is achieved in a generic fuel injector having the features in the characterizing part of claim 1.

[0007] The fuel injector for intermittent fuel injection into the combustion chamber of an internal combustion engine has a housing with a high-pressure inlet for the fuel at very high pressure, up to 2000 bar or more, and an injector seat.

[0008] Inside the housing, a high-pressure chamber runs from the high-pressure inlet to the injection valve seat.

[0009] An injection valve member is arranged in the housing so that it can move longitudinally. This injection valve member is loaded against the injection valve seat by the force of a closing spring and is designed to interact with the injection valve seat. In the resting state, the injection valve member rests against the injection valve seat and thus, in a known manner, prevents the injection of fuel from the high-pressure chamber into the combustion chamber of the internal combustion engine. To trigger an injection process, the injection valve member is lifted from the injection valve seat against the force of the closing spring. To end an injection process, the injection valve member then rests against the injection valve seat again.

[0010] A double-acting control piston is formed on the injection valve member, which defines the high-pressure chamber with its side facing the injection valve seat and a control chamber with its side facing away from the injection valve seat.

[0011] Preferably, the control chamber is circumferentially delimited by a preferably hollow-cylindrical sleeve on which the control piston is slidably guided in a tight fit and on which the closing spring is supported, which on the other hand is supported on the injection valve member and applies its spring force to the latter in the direction of the injection valve seat.

[0012] A slide valve body is guided in a preferably tight sliding fit defining a longitudinal axis, allowing it to move freely along the longitudinal axis. This slide valve body has a first end face facing the control chamber and delimiting it, and a second end face facing away from the control chamber in the longitudinal direction.

[0013] Preferably, the slide valve body has an outer wall that is at least approximately rotationally symmetrical to the longitudinal axis.

[0014] If necessary, this sliding fit is also formed on the sleeve or on the housing or component.

[0015] Furthermore, a control body is arranged in the housing, fixed to the housing, which, with its front side facing the slide valve body, forms a slide valve seat that interacts with the second end face of the slide valve body.

[0016] Preferably, the sleeve is held in contact with the control body by means of the force of the closing spring acting on it.

[0017] Furthermore, the slide valve body has a throttle passage arranged between the first end face and the second end face.

[0018] The control body has a control passage extending from its front side, which is permanently connected to the throttle passage and at the other end can be connected to and separated from a low-pressure chamber by means of a pilot valve.

[0019] A preferred constriction of the control passage is located in an end region of the control passage facing the low-pressure chamber.

[0020] This control passage and the throttle passage can be connected to the high-pressure chamber via a throttle inlet formed on the slide valve body, preferably permanently, at least for terminating an injection process.

[0021] The slide valve body further comprises a throttle inlet extending from the second end face into the control chamber, which is closed by the control body when the slide valve body is in contact with the control body.

[0022] When the slide valve body lifts off the control body, a gap forms between them, through which the throttle passage, the control passage, and the throttle inlet are connected to the high-pressure chamber. When the slide valve body is in contact with the control body, this gap is closed.

[0023] In order to connect this gap to the high-pressure chamber, the sleeve may have a passage connected to the high-pressure chamber in its end region facing the control body.

[0024] According to the invention, a blind hole-shaped recess is formed on the slide valve body, extending from its first end face, which is centric to the longitudinal axis and preferably rotationally symmetrical.

[0025] From this recess, preferably from its bottom, which is preferably flat and runs at right angles to the longitudinal axis, the throttle passage running towards the second end face leads away and into this recess, preferably in the region of its bottom, the throttle inlet coming from the second end face opens.

[0026] Since the recess starts from the first end face of the slide valve body, its volume is part of the control chamber.

[0027] The recess makes it possible to make both the throttle passage and the throttle inlet shorter than is known from the prior art, which simplifies their production.

[0028] Furthermore, the inventive design of the slide valve body allows the throttle passage and the throttle inlet to be positioned close to one another and close to the longitudinal axis. This avoids the need for an adhesion surface between the control body and the slide valve body that is significantly eccentric relative to the longitudinal axis; the adhesion surface exhibits less eccentricity than in the prior art. These measures improve the response of the fuel injector compared to the prior art.On the one hand, the delay in response is shorter, meaning there is a faster response to end an injection process, and on the other hand, due to the symmetrical pressure distribution, the stability of the movement of the slide valve body is also improved, which is particularly important in the case of multiple injections and which evens out the operating behavior of identically designed fuel injectors.

[0029] Preferably, the throttle passage has a preferably pocket-shaped recess formed on the slide valve body, open toward the second end face, into which both the throttle section of the throttle passage that exerts the throttling effect and, if present, the throttle inlet open. Preferably, the throttle section extends in a straight line from the recess to the recess.

[0030] This recess allows the throttle passage and, if applicable, its throttle section to be positioned close to the longitudinal axis while still ensuring a permanent connection between the control passage and the throttle passage. Furthermore, the recess allows the throttle inlet, if present, to be designed with a short length, which preferably runs radially to the longitudinal axis, which also facilitates the simple production of the slide valve body.

[0031] The reduced length of the throttle passage or its throttle section compared to the prior art due to the recess and, if applicable, the depression allows the throttle passage or the throttle section to be designed with a constant cross-section or conical along its entire length. With a conical design, the taper runs in the direction from the first end face and thus from the control chamber to the second end face.

[0032] Furthermore, it is possible to round off the inlet edge from the control chamber into the throttle passage or its throttle section in order to improve flow stability and flow uniformity.

[0033] Since the throttle inlet has a larger cross-section than the throttle passage or its throttle section, it can be designed with a constant cross-section over its entire length.

[0034] If a throttle inlet is present and opens into the recess, it is preferably designed with a constant cross-section or conical along its entire length. With a conical design, the taper runs toward the recess. Furthermore, it is possible to round the inlet edge of the throttle inlet facing the high-pressure chamber to improve flow stability and flow uniformity. The short length of the throttle inlet enables cost-effective manufacturing.

[0035] In a plan view of the second front side, the recess preferably has the shape of a rectangle with rounded corners, wherein the long sides preferably extend parallel to a radial to the long axis and the short sides extend at right angles thereto.

[0036] The throttle section preferably opens into the recess adjacent to the radially inner end of the recess. Furthermore, this embodiment allows for a particularly short throttle inlet length.

[0037] Preferably, the throttle passage, if applicable its throttle section, as well as the throttle inlet run straight and parallel to the longitudinal direction, which enables the production of the throttle passage and the throttle inlet with a single machine setup.

[0038] Furthermore, the distance between the recess and the throttle inlet can be small, since the partition wall between them has only a short length, measured in the direction of the longitudinal axis.

[0039] Preferably, the throttle inlet extends with its wall at least approximately along the longitudinal axis or adjacent to it. This allows for only slight eccentricity and a design of the adhesion surface that is at least almost rotationally symmetrical to the longitudinal axis.

[0040] Preferably, the throttle passage and the recess are arranged diametrically opposite the throttle inlet, allowing for a space-saving design.

[0041] Preferably, the second end face has an annular, self-contained orifice sealing bead extending around the opening of the throttle inlet on this side, and a self-contained annular sealing bead extending along the radial outer wall of the slide valve body. The orifice sealing bead and the annular sealing bead are designed to cooperate sealingly with the slide valve seat of the control body when the slide valve body rests against the control body.

[0042] The mouth sealing bead and the ring sealing bead have a low height measured in the longitudinal direction.

[0043] Preferably, the orifice sealing bead radially inward and the annular sealing bead radially outward define an annular disc-shaped front recess into which the throttle passage opens and from which the recess may extend.

[0044] This design allows the sealing surfaces between the slide valve body and the control body to be kept small, which leads to a further reduction of the adhesion forces.

[0045] Preferably, the front side of the control body forming the slide valve seat is flat. This allows for simple production of the control body and ensures a cleanly sealing slide valve seat.

[0046] Preferably, a spring element is arranged in the recess, which is supported on the one hand in the recess on the slide valve body and on the other hand on the injection valve member.

[0047] The task of this spring element is to keep the slide valve body in contact with the control body when the pressure forces are balanced.

[0048] Preferably, the recess has a shoulder against which the spring element rests with its adjacent end. This prevents a conflict between the spring element and the adjacent orifices of the throttle passage and the throttle inlet, which could negatively affect the flow.

[0049] Furthermore, the spring element can be made smaller than in the prior art, which enables a reduction in the volume of the control chamber and thus a faster response, especially when triggering an injection process.

[0050] Preferably, the depth of the recess measured from the first end face in the direction of the longitudinal axis, i.e., from the first end face to the bottom of the recess, is at least half as long as the distance between the first end face and the second end face of the slide valve body. Preferably, the depth is at least approximately three-quarters of this distance.

[0051] This allows, on the one hand, a very short length of the throttle passage and the throttle inlet and, on the other hand, the accommodation of the largest part of the spring element.

[0052] Preferably, the smallest cross-section of the recess is at least five times the sum of the flow cross-sections of the throttle inlet and the throttle passage. Thus, the recess does not represent a throttle restriction for the fuel with respect to the throttle inlet and the throttle passage.

[0053] Preferably, the throttle passage and the control passage are connected to the high-pressure chamber via the throttle inlet formed on the slide valve body, preferably permanently, but at least until the end of an injection process. This supports a very rapid termination of an injection process, in which fuel can flow through the throttle inlet when the control passage is closed.

[0054] Preferably, the slide valve body is provided with a circumferential outer taper in an end region adjacent to the second end face, radially outward, which is acted upon by the high-pressure fuel. This creates a pressure-effective annular surface, which leads to a pressure force directed away from the control body and toward the control chamber.

[0055] This supports or, in the absence of a throttle inlet, causes the slide valve body to lift off the control body to end an injection process.

[0056] If a throttle inlet is present, the pressure on the second end face increases very rapidly due to the fuel flow when the control passage is closed to terminate an injection cycle. This leads to a rapid lift of the slide valve body from the control body and a very rapid termination of the injection cycle.

[0057] If there is no throttle inlet and the control passage is closed to end an injection process, the slide valve body lifts off the control body as soon as the force of the fuel acting on the second end face, together with the aforementioned pressure force, is greater than the force acting on the slide valve body from the fuel in the control chamber and any spring element present. As soon as the slide valve body is lifted off the control body, fuel flows into the control chamber via the gap thus formed and the throttle inlet and the throttle passage, which leads to a rapid pressure increase in the control chamber and a corresponding movement of the injection valve member towards the injection valve seat.

[0058] The advantage of this variant is that during an injection process, no fuel can flow from the high-pressure chamber into the control passage, resulting in lower fuel consumption for controlling the injector. Furthermore, when the control passage opens to trigger an injection process, the pressure in the control chamber decreases more quickly, resulting in the rapid lifting of the injector valve element from the injector seat.

[0059] The invention is described in more detail using an exemplary embodiment shown in the figures. They show, purely schematically: Fig. 1 a longitudinal section through a fuel injection valve for intermittent fuel injection into the combustion chamber of an internal combustion engine; Fig. 2 also in longitudinal section and opposite Fig. 1 enlarged section of the fuel injection valve marked there with rectangle II; Fig. 3 also in longitudinal section and opposite Fig. 2enlarges the section of the fuel injection valve designated there by rectangle III; Fig. 4 a longitudinal section through a slide valve body of the fuel injection valve according to the Fig. 1 to 3 ; Fig. 5 in plan view the slide valve body according to Fig. 4 ; Fig. 6 in perspective view from above the slide valve body according to the Figs. 4 and 5 ; and Fig. 7 in perspective view from below the slide valve body according to the Fig. 4 to 6 .

[0060] In all figures, the same reference numerals are used for corresponding components.

[0061] The Fig. 1 to 3The fuel injector 10, shown in a longitudinal section, for intermittent fuel injection into the combustion chamber 12 of an internal combustion engine comprises a housing 14, on which a high-pressure inlet 16 and an injection valve seat 18 are formed. A high-pressure chamber 20 extends inside the housing 14 from the high-pressure inlet 16 to the injection valve seat 18.

[0062] Fuel under very high pressure is supplied to the high-pressure chamber 20 through the high-pressure inlet 16 in a known manner.

[0063] A needle-shaped injection valve member 22, which interacts with the injection valve seat 18, is arranged and guided in the housing 14 for longitudinal movement. A closing spring 24 is supported on the injection valve member 22 and applies a spring force toward the injection valve seat 18.

[0064] A double-acting control piston 26 is formed in an end region of the injection valve member 22 facing away from the injection valve seat. Its piston surface 28 facing the injection valve seat 18 defines the high-pressure chamber 20 and is thus exposed to the high-pressure fuel. With its end surface 30 facing away from the injection valve seat 18, the control piston 16 defines a control chamber 32.

[0065] The control piston 26 is slidably guided in a tight fit 34 in a hollow cylindrical control sleeve 36, which is rotationally symmetrical about a longitudinal axis 38. In the illustrated embodiment, this axis coincides with the longitudinal axis of the housing 14 and the longitudinal axis of the injection valve member 22.

[0066] The control sleeve 36 delimits the control chamber 32 circumferentially and the closing spring 24 is supported at its end facing the injection valve seat.

[0067] In the control sleeve 36, a cylindrical slide valve body 42 is movably guided in the direction of the longitudinal axis 38 in a tight sliding fit 40 which defines the longitudinal axis 38.

[0068] The slide valve body 42 has a first end face 44 facing the control chamber 32 and thus the control piston 26, and a second end face 46 opposite the first end face and thus facing away from the control piston 26. A throttle passage 48 is arranged between the first end face 44 and the second end face 46.

[0069] A control body 50 is arranged fixedly in the housing 14, which, with its front side 52 facing the slide valve body 42 and, in the example shown, flat, forms a slide valve seat 54 which interacts with the second end face 46 of the slide valve body 42.

[0070] The control sleeve 36 rests with its this-side end against the front side 52 of the control body 50, where it is held in place by the closing spring 24. In the this-side end region, the control sleeve 36 has at least one passage 56 connected to the high-pressure chamber 20.

[0071] A control passage 58 extends from the front side 52 through the control body 50. On the side of the control body 58 facing away from the front side 52, this passage can be connected to and separated from a low-pressure chamber 62 by means of a pilot valve 60. The narrowest point of the control passage 58 is located in the end section of the control passage 58 facing the low-pressure chamber.

[0072] In a known manner, fuel flowing into the low-pressure chamber 62 is returned to a fuel tank via a fuel return line.

[0073] The throttle passage 48 and the control passage 58 are permanently connected to each other.

[0074] Furthermore, the throttle passage 48 and the control passage 58 are permanently fluidically connected to the high-pressure chamber 20 via a throttle inlet 64 formed on the slide valve body 42; in the illustrated embodiment, namely via the passage 56 of the control sleeve 36.

[0075] Furthermore, the slide valve body 42 has a throttle inlet 66 extending from the second end face 46 and opening into the control chamber 32. This throttle inlet is closed when the slide valve body 42 rests against the control body 50.

[0076] If the slide valve body 42 moves away from the control body 50, a gap 68 is formed between them, which is also connected to the high-pressure chamber 20 via the passage 56 and via which the throttle passage 48 and the control passage 58 are additionally connected and the throttle inlet 66 are connected to the high-pressure chamber 20.

[0077] Formed on the slide valve body 42 is a blind hole-shaped recess 70 extending from the first end face 44 and rotationally symmetrical to the longitudinal axis 38. From the bottom 72 of this recess 70, which extends perpendicular to the longitudinal axis 38, the throttle passage 48 extends to the second end face 46. Furthermore, in the region of the bottom 72, the throttle inlet 66 opens into the recess 70 and thus into the control chamber 32.

[0078] With additional reference to the Fig. 4 to 7 , which show the slide valve body 42 in different representations, this will now be described in more detail.

[0079] In the exemplary embodiment shown, a throttle section 74 of the throttle passage 48 and the throttle inlet 66 have a circular cylindrical shape throughout and run parallel to the longitudinal axis 38. The throttle inlet 66 borders on the longitudinal axis 38 and, diametrically opposite, runs the throttle section 74 at a radial distance from the longitudinal axis 38.

[0080] It is also possible to form the throttle section 74 from the recess 70, preferably over the entire length, in a conical manner and / or to round the edge between the base 72 and the throttle section 74.

[0081] The throttle section 74 opens into a pocket-shaped recess 76, which belongs to the throttle passage 48 and is recessed on the slide valve body 42 from the second end face 46.

[0082] The throttle inlet 64, which runs radially to the longitudinal axis 38, also opens into this pocket-shaped recess 76.

[0083] At the radially outer inlet opening of the throttle inlet 64 and diametrically opposite thereto, a chamfer 78 running in a tangential direction is provided on the slide valve body 42 in order to ensure a low-loss inflow of the fuel and symmetrical pressure force conditions and to enable better machining of the throttle inlet 64.

[0084] The pocket-shaped recess 76, which is fully open toward the second end face 46, is cuboid-shaped with rounded edges. The long sides 80 run parallel to the radial direction, to which the throttle inlet 64 is centered. The short sides 82 run at right angles to it. Radially inward, the throttle passage 48 is thus separated from the throttle inlet 66 by a thin wall over its entire axial length.

[0085] Alternatively, it is also possible to form the second sides, in plan view, semicircular.

[0086] The second end face 46 has a self-contained, annular orifice sealing bead 86 extending around the this-side orifice 84 of the throttle inlet 66. Along the radially outer surface 88 of the slide valve body 42, the second end face 46 has a self-contained, circular annular sealing bead 90. The annular sealing surfaces at the axially free end of the orifice sealing bead 86 and the annular sealing bead 90 lie in a common plane, which runs perpendicular to the longitudinal axis 38. The orifice sealing bead 86 and the annular sealing bead 90 interact with the slide valve seat 54 formed by the front face 52 of the control body 50.

[0087] An annular disc-shaped front recess 92 is bounded radially inward by the mouth sealing bead 86 and radially outward by the annular sealing bead 90. The pocket-shaped recess 76 is completely open towards the front recess 92.

[0088] The depth of the front recess 92 and thus the height of the mouth sealing bead 86 and the annular sealing bead 90 are small; for example, between 0.05 mm and 0.20 mm.

[0089] As is particularly evident from the Fig. 3 , 4 to 7 As can be seen, in the embodiment of the slide valve body 42 shown, a permanent connection between the control passage 58 and the throttle passage 48 is guaranteed in the region of the second end face 46, regardless of the rotational position of the slide valve body 42 relative to the control body 50. Furthermore, the annular sealing surfaces formed by the mouth sealing bead 86 and the annular sealing bead 90 have a small radial width, which on the one hand leads to low adhesion between the slide valve body 42 and the control body 50 and on the other hand leads to a good sealing effect with respect to the high-pressure chamber 20 when the slide valve body 42 rests against the control body 50.

[0090] For the sake of completeness, it should be mentioned that in an end region adjacent to the second end face 46, the lateral surface 88 is formed with an external taper 148, tapered conically in the illustrated embodiment, toward the end of the slide valve body 42 on this side and extending into the chamfers 78. This ensures that high-pressure fuel is always present in this region around the slide valve body 42, thus ensuring that symmetrical hydraulic forces act on the slide valve body 42.

[0091] This effect is supplemented by a ring recess 94 radially inside the control sleeve 36 in the end area on this side, see Fig. 3 , which is connected to the high-pressure chamber 20 via the passage 56.

[0092] As a result of the external taper 148, a pressure-effective annular surface with an outer diameter D1 and an inner diameter D2 (see Fig. 4) is present, which is pressurized with the high-pressure fuel. As a result, when the slide valve body 42 rests against the control body 50, a pressure force generated by the high-pressure fuel acts on it in the direction away from the control body 50 and toward the control chamber 32. The diameter D1 corresponds to the diameter of the tight sliding fit 40, and the diameter D2 corresponds to the outer diameter of the annular sealing bead 90 and thus of the slide valve seat 54.

[0093] The recess 70 of the slide valve body 42, which has a circular cross-section over its entire length, extends, in the direction of the longitudinal axis 38 and measured from the first end face 44, over a length L of approximately three-quarters of the distance A between the first end face 44 and the second end face 46. Approximately centrally between the first end face 44 and the second end face 46, the recess 70 has a shoulder 96 narrowing the cross-section, on which, as the Fig. 1 to 3 show, a spring element 98 is supported.

[0094] Measured from the first end face 44, the recess has a conical taper 100 at approximately one-third of the distance A between the first end face 44 and the second end face 46. This ensures that the spring element 98 is securely held with its end region on this side, between the conical taper 100 and the shoulder 96, but does not rest against the slide valve body 42 between the first end face 44 and the conical taper 100.

[0095] In the illustrated embodiment, the smallest cross-section of the recess 70, in the circular cylindrical section between the shoulder 96 and the bottom 72 of the recess 70, is approximately eight times larger than the sum of the cross-sections of the throttle inlet 66 and the throttle passage 48. In the area from the first end face 44 to the shoulder 96, this ratio is even greater, even with the spring element 98 inserted. Consequently, the recess 70 has no throttling effect on the fuel flowing through the throttle inlet 66 and the throttle passage 48.

[0096] The design of the first end face 44 is shown in the Fig. 4 and 7particularly clearly visible. On the otherwise flat first end face 44, six trapezoidal stop cams 104 are formed, which are evenly distributed in the circumferential direction and project in the axial direction and are separated from one another by end depressions 102. The stop cams 104 are intended to engage with a stop shoulder 106 formed on the inside of the control sleeve 36 (see Fig. 3 ) to cooperate. This design of the slide valve body 42 on the first end face 44 ensures minimal adhesion forces between the stop shoulder 106 and the slide valve body 42 when the latter, as a result of the pressure conditions, wants to move away from the stop shoulder 106 in the direction of the control body 50.

[0097] How this Fig. 2 and 3As shown, the end surface 30 of the injection valve member 80 facing the slide valve body 42 has a centrally projecting knob 108, which is encompassed by the end region of the spring element 98 on this side. As a result, the spring element 98 is also held centrally on this side.

[0098] The spring force generated by the spring element 98 is small compared to that of the closing spring 24, but guarantees that when hydraulic pressure is equalized on both sides of the slide valve body 42, the latter rests against the control body 50.

[0099] The slide valve body 42 can thus rotate around the Fig. 3 with a stroke designated H2 between the stop shoulder 106 and the control body 50. In the Fig. 3 the slide valve body 42 is shown resting against the stop shoulder 106 and thus lifted from the control body 50 by the maximum stroke H2.

[0100] Further on, Fig. 3H1 indicates the maximum stroke of the injection valve member 22. In the Fig. 3 In the position shown, the injection valve member 22 rests against the injection valve seat 18. However, this maximum stroke H1 is only possible if the slide valve body 42 rests against the control body 50.

[0101] If the control piston 26 of the injection valve member 22 comes into contact with the slide valve body 42 during an injection process, the stop cams 104 also ensure minimal adhesion conditions between the slide valve body 42 and the injection valve member 22.

[0102] The tight fit 34 for the control piston 26 has a tolerance of 2 µm to 10 µm, and the sliding fit 40 for the slide valve body 40 also has a tolerance of 2 µm to 10 µm. The stroke H2 of the slide valve body 42 is approximately 0.04 mm to approximately 0.10 mm, and the stroke H1 of the injection valve member 22 is approximately 0.30 mm to approximately 0.50 mm, depending on the size of the combustion chambers 12 of the internal combustion engine.

[0103] Also depending on the size of the combustion chambers 12 of the internal combustion engine, the diameter of the throttle passage 66 is, for example, approximately 0.30 mm to approximately 0.80 mm, of the throttle section 74 approximately 0.10 mm to approximately 0.25 mm, of the throttle inlet 64 approximately 0.10 mm to approximately 0.25 mm and of the narrowest point of the control passage approximately 0.20 mm to approximately 0.45 mm.

[0104] The following are the remaining Fig. 1 to 3 shown components of the fuel injector 10 are described.

[0105] The housing 14 has a substantially circular-cylindrical storage body 110, on the front of which the high-pressure inlet 16 is formed. A blind-hole-like bore extends from the high-pressure inlet 16 to an end region of the storage body 110 facing away from it, forming a discrete storage chamber 112.

[0106] A truncated cone-shaped support 114 with a cup-shaped filter 116 for the fuel is inserted into this blind-hole-like bore from the high-pressure inlet 16. The support 114 can also be designed as a valve support with a check valve, as is known from document WO 2014 / 131497 A1.

[0107] A section of a fuel channel 118 extends from the bottom of the blind hole-like bore forming the discrete storage chamber 112 to the end face of the storage body 110 on this side, extending obliquely in a radial direction towards the outside with respect to the longitudinal axis 38.

[0108] With respect to this section of the fuel channel 118, radially opposite the longitudinal axis 38, a bore 120 extends from the end face of the storage body 110 to an electrical control connection 122. An electrical control line 126 for controlling the pilot valve 60 runs in the bore 120 from the control connection 122 to a connector plug 124.

[0109] A generally known electromagnetic actuator 128 is housed in an intermediate body 130 of the housing 14, which sealingly abuts the end face of the accumulator body 110 facing away from the high-pressure inlet 16. The coil of the actuator 128 is electrically connected to the connector plug 124.

[0110] A second section of the fuel channel 118 extends laterally of the actuator 128 parallel to the longitudinal axis 38 through the intermediate body 130.

[0111] The pilot valve 60 has a plunger 132 - Fig. 2 and3 - which is actuated by the actuator 128 to connect or disconnect the control passage 58 from the low-pressure chamber 62. For the sake of completeness, it should be mentioned that the rotational position of the intermediate body 130 relative to the storage body 110 is determined by positioning pins.

[0112] On the end face of the intermediate body 130 facing away from the storage body 110, a nozzle body 134 is sealingly located, on which the injection valve seat 18 is formed.

[0113] A union nut 136 is supported on an outer shoulder of the nozzle body 134, receives the intermediate body 130 and is threaded with its internal thread onto an external thread of the storage body 110, so that the nozzle body 134 lies sealingly against the intermediate body 130 and the latter against the storage body 110.

[0114] In the nozzle body 134, a third section of the fuel channel 118 extends from the second section in the intermediate body 130 obliquely in the radial direction towards the inside into a control recess 138 which is rotationally symmetrical to the longitudinal axis 38 and which extends from the end face of the nozzle body 134 facing the intermediate body 130 to the injection valve seat 18.

[0115] In an end region of this control recess 138 facing the intermediate body 130 there is the control body 50 which is in sealing contact with the end face of the intermediate body 130 and whose rotational position is determined by means of a positioning pin 140 which is inserted into the control body 50 on the one hand and engages into the intermediate body 130 on the other hand.

[0116] A further positioning pin 142 engages on the one hand in the nozzle body 134 and on the other hand in the intermediate body 130 in order to fix their mutual rotational position.

[0117] The control recess 138, the fuel channel 118 and the discrete storage chamber 112 form the high-pressure chamber 20.

[0118] In a guide section of the nozzle body 134 facing the injection valve seat 18, the control recess 138 is circularly cylindrical. The injection valve member 122, located in the control recess 138, is guided on the guide section so that it can move freely in the direction of the longitudinal axis 38 by guide projections 144 spaced apart from one another in the circumferential direction and extending in the direction of the longitudinal axis 38. Between the guide projections 144, the fuel can reach the injection valve seat 18 virtually unhindered.

[0119] Downstream of the conically shaped injection valve seat 18, nozzle passages 146 are formed on the nozzle body 134 in a known manner, through which fuel is injected into the combustion chamber 12 during an injection process.

[0120] In a central section of the control recess 138 there is the control sleeve 136, which is held in contact with the control body 50 by the closing spring 24, the closing spring 24 on the other hand being supported on the injection valve member 22.

[0121] As described above, both the double-acting control piston 26 and the slide valve body 42, which is guided between the double-acting control piston 26 and the control body 50 on the control sleeve 36 in a close sliding fit 40, are arranged in the control sleeve 36.

[0122] The fuel injector 10 functions as follows: In the idle state, the pilot valve 60 separates the control passage 58 from the low-pressure chamber 62. The slide valve body 42 rests with its second end face 46 sealingly against the front face 52 of the control body 50. High-pressure fuel is present in the control chamber 32, the control passage 58, the throttle inlet 66, the throttle passage 48, and the end recess 92, with the injection valve member 22 resting against the injection valve seat 18.

[0123] To trigger an injection process, the actuator 128 is activated, causing the pilot valve 60 to connect the control passage 58 to the low-pressure chamber 62 by lifting the tappet 132 from the control body 50. Since the narrowest hydraulic cross-section of the control passage 58 is larger than the flow cross-section of the throttle inlet 64, fuel flows from the control chamber 32 through the throttle passage 48 to the low-pressure chamber 62, which leads to a rapid pressure drop in the control chamber 32 and a concomitant lifting of the injection valve member 22 from the injection valve seat 18. As soon as the injection valve member 22 is lifted from the injection valve seat 18, high-pressure fuel is injected through the nozzle passages 146 into the combustion chamber 12.

[0124] To end an injection process, the actuator 128 is de-energized, causing the tappet 132 of the pilot valve 60 to re-engage the control body 50, thereby closing the control passage 58. Since no more fuel can now flow into the low-pressure chamber 62, but fuel continues to flow through the throttle inlet 64, the pressure of the fuel in the control passage 58, in the recess 76, and thus in the end recess 92, increases more quickly than in the control chamber 32, into which fuel can flow less quickly through the throttle section 74 of the throttle passage 48. The increased fuel pressure on the second end face 46 compared to the lower pressure on the first end face 44, together with the pressure force on the annular surface, causes the slide valve body 42 to quickly lift off the control body 50, thereby forming the gap 68 therebetween.This leads to a more rapid pressure increase in the control chamber 32 via the throttle inlet 66, which causes the injection valve member 22, supported by the force of the closing spring 24, to move towards the injection valve seat 18 and come into contact with it, which leads to the termination of the injection process.

[0125] As soon as the pressure on the first end face 44 and the second end face 46 of the slide valve body 42 is approximately equalized, the slide valve body 42 moves again, under the action of the spring element 98, into contact with the control body 50.

[0126] If no throttle inlet 64 is present, the fuel injection valve and in particular the slide valve body 42 can otherwise be designed the same as described and shown in the figures.

[0127] The mode of operation when initiating an injection process is the same as described above, with the exception that no fuel can flow from the high-pressure chamber 20 and thus the pressure drop in the control chamber 32 occurs somewhat faster.

[0128] If the control passage 58 is closed to end an injection process, the slide valve body 42 lifts off the control body 50 as soon as the force of the fuel acting on the second end face 46, together with the pressure force on the annular surface mentioned above, is greater than the force acting on the slide valve body 42 from the fuel in the control chamber 32 and the spring element 98, if present. As soon as the slide valve body 42 is lifted off the control body 50, fuel flows from the high-pressure chamber into the control chamber 32 via the gap 68 thus formed and the throttle inlet 66 as well as the throttle passage 48, which leads to a rapid pressure increase in the control chamber 32 and a related movement of the injection valve member 22 towards the injection valve seat 18.

Claims

1. Fuel injection valve for intermittent fuel injection into the combustion chamber of an internal combustion engine, with a housing (14) having a high-pressure inlet (16) for the fuel under high pressure and an injection valve seat (18), a high-pressure chamber (20) arranged in the housing (14) and extending from the high-pressure inlet (16) to the injection valve seat (18), an injection valve member (22) intended for cooperation with the injection valve seat (18), arranged longitudinally movably in the housing (14) and spring-loaded in the direction towards the injection valve seat (18), a double-acting control piston (26) formed on the injection valve member (22), which delimits the high-pressure chamber (20) on the one hand and a control chamber (32) on the other hand, a spool valve body (42) which is guided in a sliding fit (40) defining a longitudinal axis (38) and which has a first end face (44) facing the control chamber (32), a second end face (46) opposite thereto and a throttle passage (48) arranged between these end faces (44, 46), a control body (50), which, with its front side (52) facing the spool valve body (42), forms a spool valve seat (54) interacting with the second end face (46) of the spool valve body (42) and has a control passage (58) which extends from the front side (52), is flow-connected to the throttle passage (48), can be connected to a low-pressure chamber (62) and separated therefrom by means of a pilot valve (60), wherein the throttle passage (48) and the control passage (58) are flow-connected to the high-pressure chamber (20) via a gap (68) which forms when the spool valve body (42) is lifted from the spool valve seat (54), and the spool valve body (42) has a throttle admission (66) which extends from the second end face (46) and opens into the control chamber (32), which is closed when the spool valve body (42) lies against the control body (50) and is connected to the high-pressure chamber (20) when the spool valve body (42) is lifted from the control body (50), wherein a recess (70) in the form of a blind hole extending from the first end face (44) and running at least approximately centrally to the longitudinal axis (38) is formed on the spool valve body (42), the throttle passage (48) extends from this recess (70) and runs to the second end face (46) and the throttle admission (66) opens into this recess (70), characterized in that the control chamber (32) is circumferentially bounded by a sleeve (36), on which the control piston (26) is guided in a sliding manner in a tight fit and on which a closing spring (24) is supported, which, on the other hand, is supported on the injection valve member (22) and acts on the latter with its spring force in the direction of the injection valve seat (18), and in that the sliding fit (40), in which the spool valve body (42) is guided, is also formed on the sleeve (36).

2. Fuel injection valve according to claim 1, characterized in that the throttle passage (48) has a preferably pocket-shaped depression (76) which is formed on the spool valve body (42), is open towards the second end face (46) and into which a throttle section (74) of the throttle passage (48) opens.

3. Fuel injection valve according to claim 1 or 2, characterized in that the throttle admission (66) extends at least approximately parallel to the longitudinal axis (38) and is at least approximately adjacent to the longitudinal axis (38).

4. Fuel injection valve according to one of claims 1 to 3, characterized in that the second end face (46) has an annular orifice sealing bead (86) extending preferably directly around an orifice (84) on this side of the throttle admission (66) and an annular sealing bead (90) extending along the radially outer shell surface (88) of the spool valve body (42), wherein the orifice sealing bead (86) and the annular sealing bead (90) are intended to cooperate with the spool valve seat (54), and wherein the orifice sealing bead (86) radially inwardly and the annular sealing bead (90) radially outwardly delimit an annular disk-shaped end depression (92) into which the throttle passage (48) opens and which is open preferably over its entire surface towards the control body (50).

5. Fuel injection valve according to claims 2 and 4, characterized in that the depression (76) is open preferably over its entire surface towards the end depression (92).

6. Fuel injection valve according to one of claims 1 to 5, characterized in that a spring element (98) is arranged in the recess (70), which is supported in the recess (70) on the spool valve body (42) on the one hand and on the injection valve member (22) on the other hand.

7. Fuel injection valve according to one of claims 1 to 6, characterized in that the length (L) of the recess (70) measured from the first end face (44) in the direction of the longitudinal axis (38) is at least half, preferably at least approximately three-quarters of the distance (A) between the first and the second end face (44, 46).

8. Fuel injection valve according to one of claims 1 to 7, characterized in that the smallest cross-section of the recess (70) is at least five times as large as the sum of the smallest cross-sections of the throttle admission (66) and the throttle passage (56).

9. Fuel injection valve according to one of claims 1 to 8, characterized in that the throttle passage (48) and the control passage (58) are flow-connected, preferably permanently, to the high-pressure chamber (20) via a throttle inlet (64) formed on the spool valve body (42).

10. Fuel injection valve according to claims 2 and 9, characterized in that the throttle inlet (64) opens into the depression (76).

11. Fuel injection valve according to one of claims 1 to 10, characterized in that the spool valve body (42) has, in an end section facing the second end face (46), radially outwards, a circumferential outer taper (148) which is acted upon by the fuel under high pressure.