Damper element
This is a continuation of copending application Ser. No. 375,909, filed May 7, 1982, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention is based on a damper element for damping a pulsating fluid flow particularly for smoothing out and reducing pressure fluctuations arising in fuel supply systems for internal combustion engines of motor vehicles having at least one elastic, non-metallic damper diaphragm. A damper element is already known which in order to smooth out and reduce pressure fluctuations communicates with the pressurized fuel of a fuel injection system and has a fabric diaphragm as its damper member. The fabric diaphragm is not absolutely impermeable to fuel, however, so that over a relatively long period in operation, more and more fuel diffuses through the fabric diaphragm into the damper chamber located behind it, the damper chamber being unventilated for safety reasons. The fuel collecting in the damper chamber impairs the damping effect more and more with time, until the damping effect actually ceases. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The damper element according to the invention, intended for damping a pulsating fluid flow has the advantage over the prior art that the passage of fuel through the damper diaphragm is prevented, at least to such an extent that the damper element retains its function over the required period in operation without impairment of the damping behavior. 
     The principal object of the invention is to provide an elastic, non-metallic diaphragm, which is in operative communication on one side with fluid and is clamped across a metal damper housing comprising a base and a cap, of polyimide. 
     It is further particularly advantageous to weld the base and cap of the damper housing together in order to reduce the danger of their destruction, such as may happen in an automobile accident, and to provide a clamping area on the cap which is slightly inclined toward the damper diaphragm and over the required service life of the damper element assures the proper fastening and sealing of the damper diaphragm. 
     It is also advantageous to clamp the damper diaphragm between a plastic cap and a plastic ring sealingly connected therewith and to dispose these elements in the interior of the welded damper housing. 
     The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a first exemplary embodiment of a damper element; 
     FIG. 2 shows a first embodiment of a cap; 
     FIG. 3 shows a second embodiment of a cap; 
     FIG. 4 shows a second exemplary embodiment of a damper element; and 
     FIG. 5 is an enlarged fragmentary illustration showing part of the damper element according to FIG. 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The damper element 1 shown in FIG. 1 has a damper housing comprising a base 2 and a cap 3. The base 2 has an outwardly extending step or flange 4, which is adjoined in the axial direction, oriented toward the open end 5, by an upstanding wall providing a closure section 6. The cap 3 has a rim area 8 associated with the closure section 6 and extending in the axial direction and also has an annular clamping area 9 provided transversely relative to the rim area 8 and associated with the step 4 of the base 2. The closure section 6 of the base 2 and the rim area 8 of the cap 3 are welded to one another, so that even if there is a severe deforming strain, such as may occur in an accident, the chamber surrounded by the damper housing 2, 3 remains sealed. A damper diaphragm 10 is sealingly clamped at its circumference between the clamping area 9 of the cap 3 and the step 4 of the base 2, separating a damper chamber 11 in the cap 3 from a fluid chamber 12 in the base 2. An oblique area 13 is advantageously provided between the rim area 8 and the clamping area 9 of the cap 3; during the assembly of the damper element 1, while the welding procedure is being performed on the base 2 and cap 3, a cooled pressing tool can rest against this oblique area 13. The damper diaphragm 10 may advantageously be made of polyimide 15, and it may be efficacious to provide additional sealing means, such as O rings or rubber washers, at the fastening location of the polyimide diaphragm 15 in order to seal it. The damper diaphragm 10 may, however, also be embodied by a fabric diaphragm 16, with the polyimide diaphragm 15 being clamped in place parallel to it on one side, or else two layers of fabric diaphragm 16 may be provided, between which the polyimide diaphragm 15 is clamped. The fabric diaphragms 16 effect sealing at the circumference, while the polyimide diaphragm prevents diffusion of the fluid from the fluid chamber 12 into the damper chamber 11. Thus, presuming that the damper diaphragm 10, embodied as a polyimide diaphragm 15 alone or also a combination of the polyimide diaphragm 15 and the fabric diaphragm 16, is intact, the passage of fuel into the damper chamber 11 is effectively prevented. The fluid chamber 12 communicates via connector fittings 17, 18 with a fluid-pressure system. The damper element 1 may thus be integrated into a fuel injection system, by way of example, and the connector fitting 17 can communicate via a fuel supply line 19 with the pressure side of a fuel supply pump 20 which supplies fuel in a pulsating manner from a fuel container 21. From the connector fitting 18, the fuel supply line 19 leads to a fuel metering unit 23, which on the one hand permits a certain return flow of the fuel to the fuel container by way of a return-flow line 24 and on the other hand determines the amount of fuel to be injected via a fuel injection valve 25. As indicated by broken lines 26, the damper element may also, however, also communicate with the return-flow line 24. 
     In the case of the cap 3 shown separately in FIG. 2, it is clearly visible that the clamping area 9 of the cap 3 inclines downward from the oblique area 13 toward the center by an angle α, so that in the assembled state, a constant tension is exerted on the damper diaphragm 10 at the fastening location. As a result, it is assured that the damper diaphragm 10 will remain in place and sealed over a long period. The size of the angle α is from 1° to 3°. 
     The cap 3&#39; shown in FIG. 3 has a central stop area 28, which limits the deflecting movement of the damper diaphragm 10 and thus prevents excessive stretching on the part of the damper diaphragm 10, particularly at very high fluid pressures. 
     In the further damper element 4&#39; of FIG. 4, the elements still the same as and having the same function as those of the corresponding damper element 1 of FIG. 1 are identified by identical reference numerals. In the damper element 1&#39; of FIG. 4, a plastic cap 30 is embedded in the damper housing 2, 3&#34; which has been welded at 6, 8. The plastic cap 30 for the most part rests on the cap 3&#34; and in order to fix its position it engages an interstice formed between the base 2 and the cap 3&#34; with an annular step 31. As shown in more detail in FIG. 5, a plastic ring 32 rests on the side of the plastic cap 30 remote from the cap 3&#34;. The plastic ring 32 is sealingly connected with the plastic cap 30, for example by ultrasonic welding, and the damper diaphragm 10 is held clamped in place between the plastic ring 32 and the plastic cap 30. The damper diaphragm 10 here may be embodied by the polyimide diaphragm 15 or by a combination of the polyimide diaphragm 15 and the fabric diaphragm 16. It may be efficacious to provide upstanding protuberances 33 on the plastic ring 32, which engage means defining openings 34 in the polyimide diaphragm 15 and protrude into corresponding recesses 35 of the plastic cap 30. The polyimide diaphragm 15 is thus firmly clamped into place in the radial direction at the tangs 33. Welding of the tangs 33 to the plastic cap 30 simultaneously increases the strength of the unit as a whole. 
     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other embodiments and variants thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.