Bellows pressure pulsation damper

A fluid communication device such as a fuel rail having a bellows damper positioned either in the end of the fuel rail or orthogonal to the axis of the fuel rail for dampening pulsed pressure waves from the flowing of the fuel. The bellows is a hollow tubular member having an enclosed end with a plurality of circular hollow ribs forming the outer surface of the bellows. The damper may also be located in a pocket or may be free floating in the fuel rail. An additional spring member is added to the damper for changing the spring rate characteristic of the bellows.

FIELD OF THE INVENTION 
This invention relates to pressure dampers for use in fuel injection 
systems in fuel delivery systems for engines for motor vehicles. 
BACKGROUND OF THE INVENTION 
In fuel rails for injector-based fuel injection systems, the various 
devices associated with the fuel system cause pressure waves in the fuel 
to propagate through the fuel rails. Such pressure waves, if occurring at 
the wrong time, may have a small amount of fuel leaving the fuel rail and 
being injected into the engine at the time the injector is pulsed open. In 
addition such pressure waves cause noise in the system that may be 
objectionable. Pressure pulses will give false readings to fuel pressure 
regulators by operating the regulator with a false indication of fuel 
pressure which may result in fuel being bypassed and returned to the fuel 
tank. 
Prior art pressure dampers such as U.S. Pat. No. 4,660,524 issued on Apr. 
28, 1987 teach the use of elastic walls forming the fuel supply line. As 
pressure pulses occur, the elastic walls function to dampen the pressure 
pulsations. U.S. Pat. No. 5,197,436 issued on Mar. 30, 1993, illustrates 
the use of a pressure damper plugged in the end of a fuel rail with a 
pressure regulator at the other end. U.S. Pat. No. 5,617,827 issued Apr. 
8, 1997, illustrates a fuel rail damper which is a compliant member 
operable to reduce peak pressure during injector firing events. The damper 
is positioned in the fuel rail so as to not adversely affect the flow of 
fuel to an injector opening in the rail. The damper is not free to rotate 
in the rail and the pressure pulses are dampen by the damper which is a 
pair of welded together shell halves with an enclosed airspace. U.S. Pat. 
No. 5,598,823 issued Feb. 4, 1997, teaches an in-line fuel pressure damper 
from the outlet of the fuel filter to the fuel rail. The damper is a 
pressure accumulator which operative to reduce transient pressure 
fluctuations induced by the fuel pump and the opening and closing of the 
fuel injectors. 
U.S. Pat. No. 5,505,181 issued on Apr. 9, 1996, and assigned to a common 
assignee, teaches an integral pressure damper that is easily attached to 
the fuel rail. The return tube is brazed to the rail and then at a 
convenient time in the assembly process the damper which is a diaphragm, 
is attached to the return tube and crimped into position. The diaphragm 
operates to reduce audible operating noise produced by the injector 
pressure pulsations. 
U.S. Pat. Nos. 5,516,266 issued May 14, 1996, and 5,413,468 issued May 9, 
1995, teach the use of a pulse damper in the fuel pump comprising a hollow 
body formed of a thin walled tube of flexible and resilient plastic 
material with heat sealed ends forming at least one chamber. The chamber 
carries a compressible gas to dampen pressure pulsations. U.S. Pat. No. 
5,411,376 issued on May 2, 1995, also teaches the use of a bellows 
modulator inside a gear rotor fuel pump for reducing pump noise by 
reducing the amplitude of fuel pressure pulses. 
U.S. Pat. No. 4,324,276 issued on Apr. 13, 1982, teaches the use of a 
bellows-like device at the junction of the lines of the flow path of the 
fluid from a fuel feed pump thereby forming a discontinuity in the flow 
path to reduce compressional vibrations of fuel being conveyed. 
SUMMARY OF THE INVENTION 
A fuel pressure damper is installed in the fuel injection system preferably 
in the fuel rail and operates to reduce the fuel pressure pulsations which 
are created primarily by the injector opening and closing. The damper has 
a bellows that responds to the pulsations and operates to contract or 
expand depending on the magnitude and direction of the pulse. The bellows 
encloses a chamber which is sealed and may contain an inert gas or 
atmospheric air at any desired pressure. The bellows typically contracts 
in the presence of a pulse and then expands when the pulse pressure is 
less than the enclosed fluid or gas. 
In another embodiment, the enclosed chamber contains a preloaded spring 
member which functions to provide a higher pressure threshold to the 
contraction of the bellows. In still another embodiment, the damper is 
fabricated to float in the rail and to absorb the pressure pulses. 
These and other embodiments will become apparent from the followed detailed 
drawings and detailed description.

DETAILED DESCRIPTION 
Referring to the Figs. by the reference characters wherein like elements 
have the same the reference character in each embodiment and more 
particularly to FIG. 1, there is illustrated a fluid communication device 
10 such as a fuel rail 11 as may be found in the fuel management system of 
a motor vehicle. In an integrated air-fuel module, the fluid communication 
device is a passageway or passageways for either or both a liquid such as 
gasoline or a non-liquid fluid, such as air. This particular fuel rail 11 
has four injector cups 12 for receiving four fuel injectors, not shown. In 
addition, there is illustrated a pair of brackets 14 for mounting the fuel 
rail 11 to an engine which is not shown. At one end of the fuel rail 11 
there is a fuel inlet 16 which is connected through several members, not 
shown, to a source of fuel. At the other end of the fuel rail, there is 
illustrated a damper 18 according to a preferred embodiment of the 
invention. The damper 18, in FIG. 1, functions both to seal the end of the 
fuel rail 11 and to dampen or suppress fuel pressure pulsations or a 
standing wave pressure pulse. 
Referring to FIG. 2, there is illustrated the damper 18 of FIG. 1. The 
damper is a member having a bellows 20 which is formed from a hollow tube 
22 having an enclosed end 24. The bellows 20 maybe formed of stainless 
steel, Inconel, electrodeposited nickel, to name but a few of the 
materials that may be used. Each material must be able to withstand the 
various fluids or fuels that are in the system. At the open end 26 of the 
tube 22, the tube is mounted to a plug member 28 in a manner to prevent 
any fluid leakage from inside the bellows 20. The hollow tube 22 may have 
any suitable fluid contained therein at any desired pressure from a vacuum 
to a positive pressure. The plug member 28 has an O-ring sealing member 30 
or the plug member may be laser welded to the tube 22 forming a seal. The 
end of the plug member 28 opposite the bellows end is secured in the fuel 
rail 11. The plug member has an outside diameter which is sized to slide 
in the fuel rail 10 with the O-ring seal 30 bearing against the inside 
wall of the fuel rail 11 to prevent any flow of fuel past the plug member. 
Once the plug member 28 and O-ring seal 30 are inserted in the fuel rail 
11, the end 32 of the fuel rail is crimped over to retain the damper 18. 
The bellows 22 may be fabricated by rolling, hydroforming, welding or 
chemical deposition. Many uses of bellows are found in motor vehicles such 
as in aneroids to compensate for altitude; in connecting flexible shafts 
together; in areas for transmitting axial or angular motion from one shaft 
to another; providing discontinuities in the fluid path to name but a few 
applications. The use of bellows as a damper however, has not found in 
fuel injection systems. In the present application, the bellows' wall is 
very thin hence very sensitive to pulsed pressure signals. The function of 
the bellows 22 is to received pulsed fuel pressure signals and by 
compressing or when in tension by stretching, to smooth out the pressure 
peaks so as to provide a relatively laminar flow of the fuel or fluid in 
the fuel rail 11 or fluid communication device 10 and into each injector 
as the respective injector is opened. The bellows 22, having its hollow 
ribs forming the discontinuous wall of the hollow tube 20, provides the 
resiliency necessary to absorb the pressure pulses. The pressure pulses 
acting on the plurality of the hollow ribs of the bellows 22 operates to 
compress or stretch the bellows thereby absorbing the pulsed pressure. The 
bellows may be in either a compression mode or in a tension mode as 
illustrated, for instance in either FIG. 5 or 8 respectively. 
The damper 18 has a plug member 28 is secured to the bellows 22 by means 
such as a 360.degree. laser weld or by chemical bonding for a leak-proof 
connection. The plug member 28 has an O-ring pocket 34 to locate and 
secure the O-ring 30 from axial movement. The major outside diameter of 
the plug member 28, as previously indicated is a very close fit to the 
inside diameter of the fuel rail 11 so that the plug member with the 
O-ring 30 functions to retain the damper 18 in the position which it is 
initially placed. Once the plug member is in position the end of the fuel 
rail 11, the fuel rail 11 is crimped 36 or folded over 38 providing a 
fixed stop with the flange 40 of the plug member 28 of the damper 18. 
Referring to FIG. 3, there is illustrated another embodiment of the damper 
18 wherein the plug member 28 is formed to receive a crimping of the fuel 
rail 11 into a groove 42 in the plug member. In this embodiment, the 
bellows 22 functions the same as in FIG. 2, but the end of the plug member 
has a circumferential groove 42 which receives the crimped end of the fuel 
rail 11. 
Referring to FIG. 3, the damper is clipped to the end of the fuel rail 11 
by means of a clip 44. The fuel rail 11 has a pair of diametrically 
opposed slots for receiving the clip 44 which is also secured in a 
circumferential groove in the plug member. Along with the O-ring 30 and 
the tight fit of the plug member, fuel can not leak from the fuel rail 11. 
In embodiments of FIGS. 3, 4 and 7, the end of the plug member 28 has a 
flange 40 that is formed to provide a positive stop to locate the damper 
18 in the end of the fuel rail 11. 
Referring to FIG. 5, there is illustrated another embodiment of the damper 
18 wherein the hollow inter space of the bellows 22 contains a bias member 
46 such as a spring member to provide an additional force. In this 
embodiment, the spring member 46 raises the force level or spring rate of 
the bellows response. Thus, a higher fuel pressure pulsation is required 
to actuate the bellows 22. This embodiment is used in higher pressure 
applications such as in high pressure fuel applications. Without the bias 
member 46, the required thickness of the walls of the hollow ribs would 
reduce the effectiveness of the bellows. 
Referring to FIG. 6, there is illustrated a damper 18 which is a floating 
damper. In this particular embodiment there is no O-ring around the plug 
member 48, as the fuel must flow by. In this particular embodiment there 
is illustrated an optional bias member 46 located in the hollow tube 22 of 
the bellows. The open end 26 of the bellows 20 is enclosed by the plug 
member 48 which also supports the one end of the bias means. The enclosed 
end 24 of the bellows, opposite the plug member 48, supports the other end 
of the bias member 46. 
In each of the previous embodiments, FIGS. 2-6, the damper 18 is located 
along the axial length of the fuel rail. This is the most typical 
application of the damper. 
Referring to FIGS. 7 and 8 the damper is located orthogonal to the axis of 
the fuel rail 11 and in a cup-like member 50 which is secured to the fuel 
rail 11 through an aperture in much the same way as the injector cups 12 
are secured to the fuel rail. Other than the damper 18 being located 
orthogonal to the fuel rail, the damper is identical to one of the dampers 
of the previous Figs. 
In FIG. 8, the damper is also located orthogonal to the axis of the fuel 
rail and the added bias member operates to increase the pressure response 
of the damper. In this particular embodiment the plug member 52 is a 
tubular member having an O-ring seal encircling the plug member 
intermediate its ends, preventing fuel from reaching the outside bottom of 
the plug member 52. The bias member 54 bears against the bottom of the 
enclosed end of the plug member 52 and against the bellows 20. The 
pressure pulses flow into the interior of the hollow tube 22 of the 
bellows and with the cooperation between the spring force and the hollow 
ribs of the bellows 20, the pressure pulses are smoothed out. 
The use of a bellows damper 18 has been shown in a fluid communication 
device 10 such as a fuel rail 11, although such a damper may be positioned 
in other parts of a fuel or fluid systems such as in cooperation with 
molded passageways. Such other areas are in pressure regulator, fuel pump 
motors or any place wherein pressure pulses occur. 
There has thus been shown, taught and illustrated the use of a bellows 
member as a pressure damper. This is in contrast to the pressure dampers 
as shown in the Background of the Invention and more particular the 
inflated members as found in the fuel rails or in the fuel pump motor. In 
addition the bellows does not require the diaphragm as found in U.S. Pat. 
No. 5,505,181.