Patent Application
20190107092
The present application claims priority to and the benefit of German patent application no. 10 2017 218 007.2, which was filed in Germany on Oct. 10, 2017, the disclosure which is incorporated herein by reference.
The present invention is directed to a decoupling element for a fuel injection device.
Another type of a simple intermediate element for a fuel injection device is already discussed in DE 101 08 466 A1. The intermediate element is a washer, having a circular cross section, that is situated in an area in which the fuel injector as well as the wall of the receiving borehole extend in the cylinder head in the shape of a truncated cone, and that is used as a compensation element for bearing and supporting the fuel injector.
Intermediate elements for fuel injection devices that are more complicated and much more difficult to manufacture are known from DE 100 27 662 A1, DE 100 38 763 A1, and EP 1 223 337 A1, among others. These intermediate elements are characterized in that they all have a multi-part or multi-layer configuration, and are sometimes intended to take on sealing and damping functions. The intermediate element discussed in DE 100 27 662 A1 includes a base body and a support body in which a sealant, through which a nozzle body of the fuel injector extends, is inserted. A multi-layer compensation element is discussed in DE 100 38 763 A1 that is made up of two rigid rings and an elastic spacer ring situated in between in a sandwich-like manner. This compensation element allows tilting of the fuel injector with respect to the axis of the receiving borehole over a relatively large angular range, as well as radial displacement of the fuel injector from the center axis of the receiving borehole.
A likewise multi-layer intermediate element is also discussed in EP 1 223 337 A1, this intermediate element being made up of multiple washers made of a damping material. The damping material made of metal, rubber, or PTFE is selected and configured in such a way that noise damping of the vibrations and noise generated by operation of the fuel injector is made possible. However, for this purpose the intermediate element must include four to six layers in order to achieve a desired damping effect.
Damping elements in a disk shape for a fuel injector, in particular an injector for injecting diesel fuel in a common rail system, are also already discussed in DE 10 2005 057 313 A1. The damping disks are intended to be inserted between the injector and the wall of the receiving borehole in the cylinder head in such a way that damping of structure-borne noise is made possible, even under high pressing forces, so that the noise emissions are reduced. The ring-shaped damping element rests with an annular face against the support surface of the cylinder head, and with a circumferential ridge rests against the conical support surface of the injector. However, this overall system has the disadvantage that the contact points of the damping element on the cylinder head and on the injector, viewed in the radial direction, are quite close to one another, and the damping element has a fairly stiff configuration due to its installation situation. As a result, clearly audible noise emissions are still present in this system.
In addition, U.S. Pat. No. 6,009,856 A provides for enclosing the fuel injector with a sleeve and filling the resulting space with an elastic, noise-damping compound to reduce noise emissions. However, this type of noise damping is very complicated, difficult to install, and costly.
The decoupling element according to the present invention for a fuel injection device having the characterizing features described herein has the advantage that an improved reduction in noise is achieved, in a very simple configuration, by decoupling or insulating. According to the present invention, the decoupling element has a bowl- or cup-shaped configuration, with a radially outer contact area and a radially inner contact area with which the decoupling element is radially inwardly and radially outwardly placeable against the fuel injector and a shoulder of the receiving borehole, the radially inner contact area of the decoupling element having a contact surface that corresponds to a convexly curved countersurface on the fuel injector or on the shoulder of the receiving borehole.
It is particularly advantageous to likewise provide a cardanic bearing between the fuel injector and the decoupling element, in the area of the radially outer contact area. In this way, during operation a constant lever arm that is independent of tolerances may be ensured between the two radial positions of the contact surfaces of the decoupling element over the entire service life. Further advantages of the arrangement according to the present invention are the defined axial rigidity with very low dispersion, and the axial support force that is free of lateral force. In addition, there is advantageously no excessively sharp-edged contact at the contact areas of the decoupling element.
Due to the shaping of the decoupling element according to the present invention, the tensile stresses and compressive stresses in the decoupling element in the installed state are minimized in a particularly advantageous manner.
Advantageous refinements and improvements of the fuel injection device described herein are possible as a result of the measures set forth in the further descriptions herein.
Ideally, the radially inner contact surface of the decoupling element is provided with a convex curvature of the countersurface, whose spherical radius has a midpoint situated approximately on the valve longitudinal axis of the fuel injector or the longitudinal axis of the receiving borehole of the cylinder head, which as a whole optimizes the reduction in the stresses, the noise decoupling, and the centered bearing of the decoupling element.
The decoupling element advantageously has an annular disk shape and an overall bowl- or cup-shaped configuration, and is manufactured as a stamped/bent part or as a turned part.
Depending on the use in an alternating pressure system or in a constant pressure system, the decoupling element is particularly advantageously configured with a nonlinear progressive spring characteristic or with a nonlinear degressive spring characteristic.
Exemplary embodiments of the present invention are illustrated in simplified form in the drawings, and explained in greater detail in the following description.
One known specific embodiment of a fuel injection device is explained in greater detail below, with reference to
A flat intermediate element 24 configured in the form of a washer is inserted between a step 21 of a valve housing 22 (not shown) or a lower end-face side 21 of a support element 19 (
Fuel injector 1 on its inflow-side end 3 includes a plug-in connection to a fuel distributor line (fuel rail) 4 that is sealed off by a sealing ring 5 between a connecting piece 6 of fuel distributor line 4, illustrated in a sectional view, and an inlet connector 7 of fuel injector 1. Fuel injector 1 is inserted into a receiving opening 12 of connecting piece 6 of fuel distributor line 4. Connecting piece 6 emerges in one piece, for example, from actual fuel distributor line 4, and upstream from receiving opening 12 has a flow opening 15 with a smaller diameter, via which the flow onto fuel injector 1 takes place. Fuel injector 1 includes an electrical connector plug 8 for the electrical contacting for actuating fuel injector 1.
A hold-down device 10 is provided between fuel injector 1 and connecting piece 6 in order to separate fuel injector 1 and fuel distributor line 4 from one another, largely free of radial force, and to securely hold down fuel injector 1 in the receiving borehole of the cylinder head. Hold-down device 10 is configured as a bow-shaped component, for example as a stamped/bent part. Hold-down device 10 includes a partial ring-shaped base element 11 from which a downwardly bent hold-down bracket 13 extends, which in the installed state rests against a downstream end face 14 of connecting piece 6 on fuel distributor line 4.
The object of the present invention is to achieve improved noise reduction, compared to the known intermediate element and damping disk approaches, in a simple manner, in particular in the noise-critical no-load operation, but also in constant pressure systems at system pressure, via a targeted configuration and geometry of intermediate element 24. The forces introduced into cylinder head 9 during the valve operation (structure-borne noise), which result in a structural excitation of cylinder head 9 and which are emitted from same as airborne noise, are the primary noise source of fuel injector 1 during the direct high-pressure injection. To achieve an improvement in the noise level, the objective is therefore to minimize the forces that are introduced into cylinder head 9. In addition to reducing the forces caused by the injection, this may be achieved by influencing the transmission behavior between fuel injector 1 and cylinder head 9.
In addition, the aim is for decoupling element 240 to achieve its full function under actual installation conditions with as little stress as possible. Therefore, according to the present invention, a configuration and an installation situation of decoupling element 240 between fuel injector 1 and cylinder head 9 are selected which minimize the tensile stresses and compressive stresses in decoupling element 240.
According to the present invention, decoupling element 240 is characterized in that it is used for reducing the power flow between fuel injector 1 and its installation environment, with the objective of reducing undesirable noise excitation in the surrounding structure. In each case the advantageous features of the spring characteristic are included in the geometric configuration and material selection of decoupling element 240 in the specific embodiments of decoupling elements 240 described below.
Decoupling element 240 in the installed state includes two support or contact areas 30, 31, a radially outer contact area 30 and a radially inner contact area 31. With outer contact area 30, in the first exemplary embodiment decoupling element 240 rests on shoulder 23 of receiving borehole 20 in cylinder head 9, for example perpendicular to the valve longitudinal axis. With inner contact area 31, decoupling element 240 is supported on valve housing 22 of fuel injector 1 in a ring shape. For this purpose, valve housing 22 includes, for example, a tapering, beveled housing section 27 which to a certain extent radially inwardly follows the course of decoupling element 240. The installation of decoupling element 240 is thus simplified.
According to the present invention, decoupling element 240 is characterized in that radially inner contact area 31 of decoupling element 240 has a contact surface 35 that corresponds to a convexly curved countersurface 37 on fuel injector 1. Tapering, beveled housing section 27 of valve housing 22 ends radially inwardly in a recess-like manner, and from this area then merges directly into convex countersurface 37. Convexly curved countersurface 37 on fuel injector 1 is advantageously formed with a constant spherical radius. The midpoint of the imaginary sphere on which countersurface 37 extends is ideally situated approximately on the valve longitudinal axis of fuel injector 1. In other words, with spherically convex countersurface 37 on radially inner contact area 31, a spherical segment of valve housing 22 annularly and circumferentially spans a full 360° about a sphere midpoint situated approximately on the valve longitudinal axis of fuel injector 1.
Contact surface 35 in radially inner contact area 31 of decoupling element 240 may have a relatively sharp-edged configuration, which has the disadvantage of increased compressive stresses in decoupling element 240. For this reason it is advantageous to likewise round contact surface 35, in particular with a very small radius, resulting in an essentially linear contact of decoupling element 240 on countersurface 37 of valve housing 22. A contact angle β of contact surface 35 of decoupling element 240 with respect to countersurface 37 is approximately 45°+/−25°.
Decoupling element 240 has a bowl- or cup-shaped configuration overall. With this configuration, optimal use is likewise made of the installation space in receiving borehole 20 of cylinder head 9, which is typically only small, in favor of a beneficial constant lever arm. Likewise spherically convex contact surface 36 in radially outer contact area 30 of decoupling element 240 has either a rounded configuration with a constant radius, or a crowned, spherically curved, or convex configuration with a nonconstant radius. The radius of contact surface 36 of radially outer contact area 30 may be selected to be much larger than the radius of spherical countersurface 37 of valve housing 22, which in turn has a much larger radius than that of contact surface 35 in radially inner contact area 31, as the result of which the fatigue strength-determining tensile stresses in the outer area of decoupling element 240 may be reduced.
Prior to installation, a lock washer 39 that is pressed onto or integrally joined to valve housing 22, beneath decoupling element 240, may be provided to captively secure decoupling element 240 on fuel injector 1.
Inner end face 41 and outer end face 42 of decoupling element 240 extend in parallel to the valve longitudinal axis in a simple manner; however, to reduce the stresses in decoupling element 240, they may also extend at a small angle with respect to the valve longitudinal axis of fuel injector 1.
In
According to the present invention, decoupling element 240 is once again characterized in that radially inner contact area 31 of decoupling element 240 has a contact surface 35 that corresponds to a convexly curved countersurface 47 on cylinder head 9. Specially configured, convexly curved countersurface 47, as part of shoulder 23, radially inwardly directly adjoins shoulder 23, which extends flatly and at a right angle with respect to the valve longitudinal axis of fuel injector 1. Convexly curved countersurface 47 on cylinder head 9 is advantageously formed with a constant spherical radius. Ideally, the midpoint of the imaginary sphere on which countersurface 47 extends is situated approximately on the valve longitudinal axis of fuel injector 1 or on the longitudinal axis of receiving borehole 20. In other words, with spherically convex countersurface 47 on radially inner contact area 31, a spherical segment of cylinder head 9 annularly and circumferentially spans a full 360° about a sphere midpoint situated approximately on the longitudinal axis of receiving borehole 20.
The above statements with regard to the radii and angles also apply to this second exemplary embodiment.
Due to the double cardanic bearing of decoupling element 240, a constant lever arm that is independent of tolerances may advantageously be ensured during operation between the two radial positions of contact surfaces 35 and 36 of decoupling element 240 over the entire service life.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017218007.2 | Oct 2017 | DE | national |
