Decoupling element

Abstract

A decoupling element (3) serves to decouple a fuel injector (2) from a cylinder head. The decoupling element (3) has a base body (6) which, when assembled, serves to enclose a housing (5) of the fuel injector (2). A cylinder-side support region (7) is formed on the base body (6) and serves to support the cylinder head (4). Furthermore, a valve-side support region (8) is formed on the base body (6) and serves to support the fuel injector (2). When the fuel injector (2) is supported between the valve-side support region (8) and the cylinder-side support region (7), the base body (6) is subjected to pressure.In this case, only the cylinder-side support region (7) of the base body (6) is designed in the form of a closed ring, while the base body (6) has segments (15-18) distributed over a circumference, which are connected to one another by the closed ring (20) of the cylinder-side support region (7). The closed ring (20) of the cylinder-side support region (7) is at least indirectly connected to a snap ring (34) which, in the assembled state, interacts with the housing (5) of the fuel injector (2), whereby the decoupling element (3) can already be pre-assembled on the fuel injector (2). The decoupling element (3) enables the reduction of noise transmission from the fuel injector (2) to the cylinder head (4). Furthermore, an arrangement (1) with such a decoupling element (3) and a fuel injector (2) is described.

Description

State of the art

[0001] The invention relates to a decoupling element used to decouple a fuel injector from a cylinder head, and to an assembly comprising a fuel injector and such a decoupling element. Specifically, the invention relates to the field of fuel injection systems of internal combustion engines, wherein fuel under high pressure is injected into associated combustion chambers of the internal combustion engine via fuel injectors.

[0002] A compensating element for a fuel injector is known from DE 103 38 715 A1. The compensating element serves to mount a fuel injector in a cylinder head of an internal combustion engine. The compensating element is annular and arranged between a valve housing of the fuel injector and a wall of a receiving bore in the cylinder head. The compensating element has legs that are supported on the fuel injector and the cylinder head. A first leg rests against a shoulder of the cylinder head. A second leg rests against a shoulder of the valve housing. Undercuts and openings can be provided on the compensating element. The compensating element can have segments that are punched out of the compensating element and bent radially inward.In this way, the compensating element compensates for manufacturing tolerances of the individual components as well as tolerances resulting from the heating of the fuel injector during operation, thus preventing jamming and misalignment.

[0003] The design of the compensating element for a fuel injection valve known from DE 103 38 715 A1 has the disadvantage that, under a correspondingly high load, stresses occur in the material around the circumference, which can lead to cracks on the circumference and ultimately to the failure of the compensating element.

[0004] EP 2 469 069 A1 already discloses a damping element for an injection valve, which has a washer-like, substantially annular shape and comprises a central longitudinal axis. It further comprises a plurality of at least three uneven portions extending parallel to the central longitudinal axis and arranged at equal distances from one another.

[0005] DE 10 2008 054 591 A1 discloses a decoupling element for a fuel injection device. The decoupling element enables a low-noise design. The spring stiffness of the decoupling element is selected to be so low, and the decoupling element is positioned such that the decoupling resonance lies in the frequency range below 2.5 kHz. In one possible embodiment, a possible misalignment of a fuel injector is compensated for by locally weakening an inner support area of ​​the decoupling element. This local weakening of the radially inner support area is achieved by radially extending slots that extend from the inner diameter of the decoupling element, for example, to the inner radius. Typically, such slots or other stiffness-reducing openings can be provided in a number of three to twenty.

[0006] The decoupling element known from DE 10 2008 054 591 A1 has the disadvantage that it is constructed like a disc spring and is subjected to tensile stress when installed. This poses the problem of ensuring sufficient component strength and, at the same time, the desired noise reduction over its service life. Disclosure of the invention

[0007] The decoupling element according to the invention with the features of claim 1 has the advantage of ensuring improved vibration damping throughout its service life. In particular, this results in the advantage of ensuring sufficient noise damping even after a long service life, preventing premature component failure.

[0008] The proposed decoupling element can be used to reduce noise transmission from the fuel injector to the cylinder head in a simple manner, with the smallest possible installation space, and at minimal additional cost. A specified target stiffness, for example, of less than 50 kN / mm, can be maintained. The associated fatigue strength, which is particularly required at high system pressures, such as in gasoline direct injection, can also be ensured. Vibration isolation, decoupling, and isolation from structure-borne noise can be ensured.

[0009] The background to the invention has been found that rotationally symmetrical designs, such as those used in disc springs, do not produce the desired result in a decoupling element for high system pressures and thus large axial loads, combined with the very small installation space required. This is because such designs, due to the acting forces and the resulting deformations, create large circumferential stresses, which lead to cracks on the circumference and ultimately to the failure of the component. One conceivable solution would be to counteract these problems by increasing the wall thickness. However, due to the massive design of these elements to reduce stress, the required decoupling rigidity can then no longer be guaranteed.

[0010] According to the invention, the problem of circumferential stresses can be limited by a special segmentation that breaks the rotational symmetry. The decoupling stiffness is then determined by the sum of the stiffnesses of the individual segments distributed around the circumference. This corresponds to a parallel connection of spiral springs. The segments, which act as individual bending elements, are held together only by a comparatively small, circumferential, closed ring of the cylinder-side support area of ​​the base body. This results in better elasticity of the segments, as they are comparatively large and can therefore be designed with comparatively thicker material for a given target stiffness.On the other hand, the mechanical circumferential stresses are concentrated on the cylinder-side support area of ​​the base body, which does not contribute to the spring behavior and can therefore be designed with respect to the required circumferential forces.

[0011] The advantage of this special segmentation into the individual segments serving as bending elements is that, while maintaining the required stiffness values, significantly lower loads occur in the component and thus the strength requirements for the material are lower.

[0012] A further advantage is that the function of the tolerance compensation element required for transverse force compensation can be easily integrated into the shape of the segments (flexural elements). A spherical or similar design of the segments allows the fuel injector to tilt on the decoupling element like a ball joint, thus compensating for transverse forces and tolerance offsets between the centerline of a mounting hole on the cylinder head and the centerline of a rail cup.

[0013] Thus, the inventive design, in which only the cylinder-side support area of ​​the base body is at least partially configured in the form of a closed ring, offers significant advantages. This design is to be understood as meaning that the base body is segmented into segments distributed over the circumference, at least outside the cylinder-side support area. However, this also includes the possibility that the segments distributed over the circumference also extend partially into the cylinder-side support area of ​​the base body. In this case, the cylinder-side support area of ​​the base body is only partially configured in the form of a closed ring.

[0014] Only if the cylinder-side support area of ​​the base body is designed entirely in the form of a closed ring, then the segments of the base body distributed over the circumference do not extend into the cylinder-side support area.

[0015] It is advantageous that the base body is subjected to pressure between the valve-side support area and the cylinder-side contact area when supporting the fuel injector. This allows the segments distributed around the circumference to advantageously act as bending segments. Relatively large bending movements are possible with respect to a given maximum material stress. This enables, among other things, advantageous tolerance compensation regarding the positioning of the fuel injector.

[0016] It is also advantageous that the closed ring of the cylinder-side support area has bulges that extend radially outwards between the segments distributed over the circumference. It is further advantageous that the base body has recesses that are provided between the segments of the base body and that the recesses of the base body extend partially into the cylinder-side support area of ​​the base body, so that the cylinder-side support area of ​​the base body is only partially designed in the form of a closed ring. With this design, the segments of the base body distributed over the circumference also extend somewhat into the support area. This further facilitates bending of the segments. The component stresses that occur in the circumferential direction can also advantageously be concentrated on the closed ring.The bulges provided between the segments, which are distributed around the circumference and are themselves distributed around the circumference, ensure that the material cross-section in the area of ​​the segments is sufficiently large to absorb the forces acting in the circumferential direction. At the same time, the bulges do not influence the bending behavior of the segments. However, the bulges can be used to increase the contact surface on the cylinder head. The bulges therefore enable an improved design with additional advantages. Another advantage here is that the bulges of the closed ring bridge the recesses that partially extend into the cylinder-side contact area of ​​the base body. In this design, the bulges also extend somewhat into the areas of the cylinder-side contact area that adjoin the recesses on both sides in the circumferential direction.This results in an advantageous introduction of force into the areas adjacent to the recesses and thus an advantageous force connection over the circumference.

[0017] It is also advantageous that the closed ring of the cylinder-side support area is designed as an at least substantially flat cylinder-side support area for the cylinder head. This results in a favorable support surface and reliable positioning on the cylinder head.

[0018] It is also advantageous that a securing element is configured on at least one segment of the valve-side support area, which, when installed, interacts with the housing of the fuel injector. In particular, several securing elements can be provided, each of which is preloaded radially against the housing of the fuel injector to form a captive lock. This also enables advantageous assembly of the assembly comprising the fuel injector and the decoupling element attached to it.

[0019] Furthermore, it is advantageous that the closed ring of the cylinder-side support area is at least indirectly connected to a snap ring, which interacts with the housing of the fuel injector when installed. This also represents a possibility for attaching the decoupling element to the fuel injector, for example, during pre-assembly. This allows the assembly comprising the fuel injector and the decoupling element to be easily mounted on the cylinder head. Short description of the drawings

[0020] A preferred embodiment of the invention is explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with identical reference numerals. It shows: Fig. 1 an arrangement with a fuel injection valve and a decoupling element as well as a cylinder head in an excerpted, schematic and spatial representation according to a first example; Fig. 2 which in the Fig. 1 and the cylinder head according to a second example; Fig. 3 which in Fig. 1 and the cylinder head according to a third example; Fig. 4 the decoupling element of the Fig. 1 shown arrangement according to the first example in an excerpted, schematic and spatial representation to illustrate the functioning of a possible embodiment; Fig. 5 shows an arrangement with a fuel injection valve and a decoupling element as well as a cylinder head in a partial, schematic sectional view according to a fourth example; Fig. 6 which in Fig. 5 illustrated arrangement and the cylinder head according to an embodiment of the invention and Fig. 7 which in Fig. 5 and the cylinder head according to a sixth example. Embodiments of the invention

[0021] Fig. 1 shows an arrangement 1 with a fuel injection valve 2 and a decoupling element 3 and a cylinder head 4 in an excerpted, schematic and spatial representation according to a first example. The arrangement 1 serves for a fuel injection system of internal combustion engines. The arrangement 1 is particularly suitable for fuel injection systems for the direct injection of fuel into the combustion chambers of the internal combustion engine. In particular, the internal combustion engine can be designed as a mixture-compressing, spark-ignition internal combustion engine, wherein gasoline or other fuels suitable for such internal combustion engines, as well as suitable mixtures of such fuels, can be injected.

[0022] The decoupling element 3 is particularly suitable for such applications.

[0023] The arrangement 1 and the decoupling element 3 make it possible to reduce the noise transmission from the fuel injector 2 to the cylinder head 4. For example, the fuel injector 2 can be designed as an electromagnetic high-pressure injector, which is used in direct-injection gasoline engines. Without a decoupling element, the problem arises that the fuel injector 2 makes a noticeable and disruptive contribution to the overall engine noise. A noise that can be described as valve ticking can arise, for example, from the rapid opening and closing of the fuel injector 2 when a valve needle is moved to its respective end stops with high dynamics.The impact of the valve needle on the end stops results in brief, very high contact forces, which can be largely transmitted to the cylinder head 4 as structure-borne noise and vibrations via a housing 5 of the fuel injector 2. This then leads to a strong noise development at the cylinder head 4, which is, however, significantly reduced by the decoupling element 3, which is located between the cylinder head 4 and the fuel injector 2.

[0024] However, in addition to reducing noise generation, the decoupling element 3 must also meet the requirement that it demonstrate the required decoupling stiffness and strength, particularly at high system pressures, over its service life within a given small installation space. This is achieved by the design of the decoupling element 3 according to the invention described below with reference to the exemplary embodiment.

[0025] The decoupling element 3 has a base body 6 with a cylinder-side support area 7 and a valve-side support area 8. The cylinder-side support area 7 serves to support an upper side 9 of the cylinder head 4. The valve-side support area 8 serves to support the fuel injection valve 2. In the assembled state, which is shown in the Fig. 1, the decoupling element 3 circumferentially surrounds the housing 5 of the fuel injector 2. The upper side 9 of the cylinder head 4 is designed as a flat upper side 9 in this example.

[0026] When supporting the fuel injector 2, the base body 6 of the decoupling element 3 is subjected to pressure between the valve-side support area 8 and the cylinder-side bearing area 7. The base body 6 has segments 15, 16, 17, 18 distributed over the circumference, which are elastically bent when subjected to pressure. The segmentation of the valve-side support area 8 ensures optimal elasticity over the service life with regard to the specified material thickness. Stresses acting in the circumferential direction are significantly reduced by the segmentation in the valve-side support area 8. Furthermore, the cylinder-side bearing area 7 of the base body 6 is at least partially designed in the form of a closed ring 20. In this case, only the cylinder-side bearing area 7 of the base body 6 is at least partially designed in the form of the closed ring 20.In this example, the cylinder-side support area 7 of the base body 6 is only partially designed in the form of a closed ring 20. This is because recesses 21, 22, 23 are provided between the segments 15 to 18, which also extend slightly into the cylinder-side support area 7. As a result, for example, a web 25 of the closed ring 20 remains at the recess 22, in which the cylinder-side support area 7, viewed in the circumferential direction, has a reduced radial extension of a flat support surface 26 (. Fig. 5).

[0027] In this example, the closed ring 20 of the cylinder-side support area 7 is designed as a flat cylinder-side support area 7 with a flat contact surface 26 for the cylinder head 4. This enables reliable positioning on the cylinder head 4. This also improves vibration damping while simultaneously providing tolerance compensation for the fuel injector 2.

[0028] The recesses 21, 22, 23 extending into the cylinder-side support area 7 are preferably maximally pronounced, so that the remaining ring thickness on the web 25 is reduced to a possible minimum.

[0029] Fig. 2 shows the Fig. 1 and the cylinder head 4 according to a second example. In this example, an outer edge 27 of the closed ring 20 is bent upwards, as viewed from the top side 9 of the cylinder head 4. Depending on the respective application, this can improve the stability of the closed ring 20, particularly at the web 25, especially in confined spaces.

[0030] Fig. 3 shows the Fig. 1 and the cylinder head 4 according to a third example. In this example, the closed ring 20 of the cylinder-side support area 7 has bulges 28 between the segments 15 to 18 distributed over the circumference, whereby only the bulge 28 is identified to simplify the illustration. The bulge 28 extends radially outwards. In this example, the support surface 26 of the cylinder-side support area 7 is enlarged by the bulge 28. A bulge 28 bridges the recess 22 extending partially into the cylinder-side support area 7. As a result, the cross-sectional area, which is important for absorbing the circumferential tensile forces, is increased, particularly in the region of the web 25. This reduces the corresponding tensile stresses.For this purpose, the bulge 28 also extends into areas (zones 29, 30) of the cylinder-side support area 7 that border the recess 22 in the circumferential direction. Zones 29, 30 thus enable an advantageous frictional connection in the closed ring 20.

[0031] Fig. 4 shows the decoupling element 3 of the Fig. 1 according to the first example in an excerpted, schematic and spatial representation to illustrate the functioning of a possible embodiment. The section shown can, for example, be a quarter section of a possible embodiment. The upwardly bent segments 16, 17 are designed in the form of bent tabs which offer the fuel injector 2 a support or support along the line 31 drawn for illustration. The load due to the hold-down and compressive forces on the fuel injector 2 is transferred via this line (support line 31) to the decoupling element 3. The segments 16 to 18 bend due to the load. The overall rigidity of the decoupling is then the sum of the individual bending stiffnesses. This corresponds to a parallel connection of individual bending springs.Due to the spherical shape of the segments 15 to 18 serving as bending elements and the corresponding counter contour on the housing 5 of the fuel injector 2, the decoupling also incorporates the function of a tolerance compensation to compensate for transverse forces and / or a tolerance-related offset.

[0032] Depending on the application, segments 15 to 18 can be designed in a suitable shape, number and thickness through shape optimization so that the desired stiffness is achieved with the required strength.

[0033] Fig. Figure 5 shows an arrangement 1 with a fuel injection valve 2 and a decoupling element 3 and a cylinder head 4 in a partial, schematic sectional view according to a fourth example. For illustration purposes, a segment 18 of the base body 6 is shown in section. The valve-side support region 8 is formed on the segment 18 and other segments not shown, with the housing 5, for example, abutting against the line 31 of the segments 18, as can also be seen from Figure 5. Fig. 4 is described accordingly.

[0034] Furthermore, in this example, a securing element 32 is configured on segment 18. Preferably, further securing elements configured corresponding to securing element 32 are configured on further segments (not shown). In the assembled state shown, securing element 32 interacts with housing 5. When applied to housing 5, securing element 32 can be expanded radially outward. In particular, a claw engagement in housing 5, in particular a magnet pot of housing 5, can be achieved by a special shaping of securing element 32. This creates a loss prevention feature.

[0035] Fig. 6 shows the Fig. 5 and the cylinder head 4 according to one exemplary embodiment. In this exemplary embodiment, the segment 18 is designed as an inwardly open segment 18. This design has the additional advantage that an end stop can be realized in order to limit the maximum deformation of the segment 18. In this case, a spacer element 33 is designed on the segment 18 of the valve-side support region 8, which spacer element 33 faces the cylinder-side support region of the base body 6. When the valve-side support region 8 is subjected to pressure against the cylinder-side support region 7, the spacer element 33 strikes the cylinder-side support region 7 after a certain movement path. The spacer element 33 thus then interacts with the cylinder-side support region to limit the possible range of movement.

[0036] Furthermore, in this exemplary embodiment, a snap ring 34 is provided, which interacts with the housing 5. The closed ring 20 of the cylinder-side support area 7 is at least indirectly connected to the snap ring 34, so that the decoupling element 3 is reliably fastened to the housing 5 of the fuel injector 2. This particularly facilitates assembly of the fuel injector 2 in the cylinder head 4, since the decoupling element 3 can already be pre-assembled on the fuel injector 2.

[0037] Depending on the application, an outwardly open decoupling element 3, as shown for example in the Fig. 1 to 4, as well as an inwardly open decoupling element 3, as described in the Fig. 6 and the Fig. 7 is described.

[0038] Fig. 7 shows the Fig.5 and the cylinder head 4 according to a sixth example. In this example, the housing 5 of the fuel injector 2 has an undercut cone 35, on which the fuel injector 2 is supported on the valve-side support area 8 of the decoupling element 3. Here, the housing 5, with its undercut cone 35, rests against the line 31 of the valve-side support area 8. In this example, the design of the decoupling element 3 is simplified.

[0039] Thus, an arrangement 1 can be realized that serves for a fuel injection system of internal combustion engines. In this case, the fuel injection valve 2, in the assembled state, can be supported on the cylinder head 4 of the internal combustion engine via the decoupling element 3.

Claims

[1] Decoupling element (3) which serves to decouple a fuel injection valve (2) from a cylinder head (4), comprising a base body (6) which, in the assembled state, serves to enclose a housing (5) of the fuel injection valve (2), wherein a cylinder-side support region (7) which serves to support the cylinder head (4) and a valve-side support region (8) which serves to support the fuel injection valve (2) are formed on the base body (6), wherein only the cylinder-side support region (7) of the base body (6) is at least partially formed in the form of a closed ring (20), and wherein the base body (6) has segments (15-18) distributed over a circumference which are connected to one another by the closed ring (20) of the cylinder-side support region (7), characterized bythat the closed ring (20) of the cylinder-side support area (7) is at least indirectly connected to a snap ring (34) which, in the assembled state, interacts with the housing (5) of the fuel injection valve (2), whereby the decoupling element (3) can already be pre-assembled on the fuel injection valve (2). [2] Decoupling element according to claim 1, characterized by that the base body (6) is subjected to pressure when supporting the fuel injection valve (2) between the valve-side support area (8) and the cylinder-side support area (7). [3] Decoupling element according to claim 1 or 2, characterized by that the closed ring (20) of the cylinder-side support area (7) has bulges (28) extending radially outwards between the segments (15 - 18) distributed over the circumference. [4] Decoupling element according to claim 3, characterized bythat the base body (6) has recesses (21 - 23) which are provided between the segments (15 - 18) of the base body (6), and that the recesses (21 - 23) of the base body (6) extend partially into the cylinder-side support area (7) of the base body (6), so that the cylinder-side support area (7) of the base body (6) is only partially designed in the form of a closed ring (20). [5] Decoupling element according to claim 4, characterized by that the bulges (28) of the closed ring (20) bridge the recesses (21 - 23) extending partially into the cylinder-side support area (7) of the base body (6). [6] Decoupling element according to one of claims 1 to 5, characterized by that the closed ring (20) of the cylinder-side support area (7) is designed as an at least substantially flat cylinder-side support area (7) for the cylinder head (4). [7] Decoupling element according to one of claims 1 to 6, characterized by that a spacer element (33) is formed on at least one segment (18) of the valve-side support region (8), which, when the valve-side support region (8) is acted upon against the cylinder-side support region (7), cooperates with the cylinder-side support region (7) to limit a range of movement.

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