U.S. patent application number 10/675560 was filed with the patent office on 2005-03-31 for pre braze installed desiccant assembly for automotive condenser with integral receiver.
This patent application is currently assigned to DELPHI TECHNOLOGIES, INC.. Invention is credited to Baker, James Allen, Kent, Scott Edward, Southwick, David A..
Application Number | 20050066685 10/675560 |
Document ID | / |
Family ID | 34313999 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050066685 |
Kind Code |
A1 |
Kent, Scott Edward ; et
al. |
March 31, 2005 |
Pre braze installed desiccant assembly for automotive condenser
with integral receiver
Abstract
A condenser (10) with a return header tank (14) has a receiver
tank (22) physically attached along side a return header tank (14).
The bottom of receiver tank (22) is closed by an end cap (42) that
is attached during the single, high temperature braze process that
forms the entire condenser. The desiccant cartridge assembly (24)
of the invention has components of a material and design that allow
it to be installed within tank (22) before the end cap (42) is
attached during the braze process, with no subsequent steps.
Inventors: |
Kent, Scott Edward; (Albion,
NY) ; Southwick, David A.; (Lockport, NY) ;
Baker, James Allen; (Williamsville, NY) |
Correspondence
Address: |
PATRICK M. GRIFFIN
DELPHI TECHNOLOGIES, INC.
Legal Staff, Mail Code: 480-410-202
P.O. Box 5052
Troy
MI
48007-5052
US
|
Assignee: |
DELPHI TECHNOLOGIES, INC.
Legal Staff - Mail Code: 480-410-202 P.O. Box 5052
TROY
MI
|
Family ID: |
34313999 |
Appl. No.: |
10/675560 |
Filed: |
September 30, 2003 |
Current U.S.
Class: |
62/474 ;
62/509 |
Current CPC
Class: |
F25B 2339/0441 20130101;
F25B 43/003 20130101; F25B 39/04 20130101 |
Class at
Publication: |
062/474 ;
062/509 |
International
Class: |
F25B 043/00; F25B
039/04 |
Claims
1-3. (Canceled)
4. A condenser having a header tank and a receiver tank attached to
said header tank, said receiver tank having a tubular body, an end
closure brazed to one end thereof and an end closure brazed to an
opposite end thereof, said condenser further comprising a desiccant
cartridge assembly installed within the receiver tank prior to a
brazing operation for brazing the end closures to the tubular
structure, said desiccant cartridge assembly comprising, a tube
formed of a material capable of withstanding the braze operation,
and inserted within the receiver tank spaced apart by a radial
clearance, said tube comprising an open end, a desiccant material
contained with the tube spaced apart from the open end and exposed
to refrigerant within said receiver tank, a filter plug formed of a
material capable of withstanding the brazing operation, said filter
plug being disposed within the tube adjacent the open end to retain
said desiccant material, and, a locating and retention member
between the tube and the tubular body of the receiver tank so as to
maintain said tube radially centered and axially retained.
5. A condenser according to claim 1, further characterized in that
said locating and retention member is a clip formed of a braze
compatible material that brazes to the outside of said tube and to
the inside of said tubular body.
6. A condenser according to claim 1, further characterized in that
the filter plug has a porosity sufficiently small to retain said
desiccant material and sufficiently large to admit refrigerant,
said desiccant cartridge assembly further comprising a screen
disposed within the open end of the tube and retaining the filter
plug.
Description
TECHNICAL FIELD
[0001] This invention relates to condensers with integrated
receivers, and specifically to a desiccant cartridge capable of
being installed in the receiver prior to the condenser brazing
operation.
BACKGROUND OF THE INVENTION
[0002] Certain automotive air conditioning systems use a canister
like reservoir container for refrigerant located downstream of the
condenser, generally referred to as a "receiver." This, as opposed
to a reservoir canister located upstream of the compressor,
generally called an accumulator. Historically, receivers have been
separate canisters plumbed into the system at a location remote
from the condenser, but lately, many designs have been proposed for
directly structurally integrating the receiver/reservoir with the
outlet manifold tank of the condenser itself, often by co extruding
the two, or brazing them directly together when the entire
condenser is brazed. This generally creates a long, thin reservoir
tank, directly adjacent to the outlet manifold tank of the
condenser.
[0003] An air conditioning system needs a supply of desiccant to
which the refrigerant charge is continually exposed during the life
of the system in order to pick up any traces of moisture entering
the lines. The refrigerant reservoir canisters have generally been
the most convenient location for the desiccant supply, which may be
in a filter bag or cartridge somehow fixed inside the canister
before it is closed up. Whatever the location, it is necessary that
the desiccant material be well exposed to the refrigerant flow, but
be protected from jostling, fracture or dislodgment, so as to
prevent any of the desiccant particles from migrating through the
lines and doing damage to other parts of the system.
[0004] In the case of condensers with integral receivers, often
referred to as integral RD's, existing patents show a number of
variations on a common theme. Various cartridges and other
assemblies are provided to allow the desiccant charge to be
installed after the basic condenser/receiver structure has been run
through the braze oven and substantially completed, but for the
addition of one or more end caps to the integral receiver tank
itself. The desiccant assembly is generally made long and thin so
as to take maximum advantage of the interior size of the receiver
tank while still allowing the refrigerant to rise and fall freely
within. The cartridge is axially inserted post braze, and the tank
end cap added last. The end cap may be threaded and removable, or
welded in place. In either case, the desiccant assembly or
cartridge need not tolerate any more heat than, at the most, the
heat involved in brazing on the end cap itself, which is localized
and rather brief. For example, co owned U.S. Pat. No. 6,170,287
shows a long, thin fabric sleeve held above and away from the end
cap by a plastic post or stand off, which protects the sleeve from
the heat of end cap welding, and later maintains the sleeve
axially, and, to an extent, radially in position during condenser
operation. None of these known assemblies, however, would allow the
desiccant cartridge to be installed before the condenser/receiver
assembly was brazed, which involves temperatures approaching 1200
degrees F. for substantially longer periods than it takes to weld
on an end cap. Consequently, a post braze installation operation is
a necessity, which adds cost and cycle time.
SUMMARY OF THE INVENTION
[0005] The invention discloses a desiccant cartridge structure for
a condenser with integrally brazed receiver tank that allows the
cartridge to be assembled and installed before the condenser braze
operation. In the embodiment disclosed, the cartridge is also fixed
in place within the tank by and during the braze operation
itself.
[0006] In the preferred embodiment, all parts of the desiccant
assembly or cartridge are initially chosen to be capable of
withstanding the braze operation temperature. These components
include a long, thin heat resistant tube (preferably, a metal tube
of material similar to the tank itself), filled with a heat
resistant desiccant and open to refrigerant flow through a suitable
heat resistant filter material and ventilated end closure. A
similarly heat resistant locating and retention member serves to
keep the cartridge axially and radially located within the tank
interior as it is inserted within the tank, prior to the tank being
closed with its end cap. The tank end cap is fixed to the tank by
and during the braze operation, with no post braze operation
needed, and the desiccant cartridge remains in place, without
damage, during the same braze operation. In the embodiment
disclosed, the locating and retention member is a crown shaped clip
surrounding the cartridge tube, which not only withstands the braze
operation, but takes advantage of it by fusing to the tube and tank
interior so as to fix it permanently within the tank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features of the invention will appear from
the following written description, and from the drawings, in
which:
[0008] FIG. 1 is a schematic view of the general type of condenser
and integrated receiver tank referred to above;
[0009] FIG. 2 is a perspective view of the components of the
desiccant cartridge disassembled;
[0010] FIG. 3 is a plan view of the completed cartridge;
[0011] FIG. 4 is a cross section taken along the line 4-4 of FIG.
3;
[0012] FIG. 5 shows the cartridge about to be inserted into the
receiver tank, prior to the braze operation;
[0013] FIG. 6 shows the cartridge fully inserted, with the end cap
being added;
[0014] FIG. 7 shows the cartridge being brazed in place inside the
tank during the basic condenser brazing operation itself.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] Referring first to FIG. 1, a condenser 10 of the cross flow,
headered type, or brazed aluminum construction. Condenser 10 has an
inlet/outlet header tank 12 on one side, and a return header tank
14 on the other, each of which is divided into discrete upper (U)
and lower (L) sections by separators 16 and 18 respectively.
Heated, compressed refrigerant vapor enters the upper section (U)
of header tank 12, above separator 16, and flows across and through
the flow tubes in the main pass section (not illustrated in
detail). In the main pass, refrigerant is condensed to liquid form
and flows into the upper section (U) of return tank 14, above the
separator 18. From there, all liquid refrigerant is forced, by the
separator 18, to flow through an upper inlet 20 and into an
attached reservoir or receiver tank 22, where it backs up into a
reserve column of varying height. From the reserve column, liquid
refrigerant can flow down and through a lower outlet 21, into lower
section (L) of return tank (14) and ultimately into a sub cooler
section of condenser 10, comprised of those flow tubes located
below the two separators 16 and 18. In the sub cooler section,
liquid refrigerant is further cooled, below the temperature
necessary to simply condense it, and flows finally back into the
lower section (L) of header tank 12. The desiccant containing
structure of the invention, not illustrated in FIG. 1, is installed
within receiver tank 22, as described next. Mutually contacting
surfaces of the various components of condenser 10 (tube ends to
tube slots, fin surface to tube outer surface, etc) are, as is
conventional, clad with a braze material of a eutectic
aluminum-silicon alloy that melts at braze temperatures, is pulled
by capillary action into contact interfaces, and later hardens to
form structural and sealed joints.
[0016] Referring next to FIGS. 2 through 4, a preferred embodiment
of the desiccant cartridge of the invention, referred to generally
at 24, is illustrated. Cartridge assembly 24 has relatively few
components, the materials for which are chosen primarily so as to
be capable of withstanding the typical temperatures and times of
the braze process, which can rise to around 1200 degrees F. The
main component is a long, thin cylindrical tube 26, of aluminum or
other material that is heat resistant and compatible with the base
material of receiver tank 22. As disclosed, tube 26 is
substantially closed at the upper end and, initially, open at the
lower end, with a wall thickness of approximately half a
millimeter, and approximately 250 mm in length and 25 mm in
diameter, so as to take maximum advantage of the axial and radial
space within receiver tank 22. Tube 26 has a volume sufficient to
hold a charge of approximately 70 grams of a suitable desiccant
material 28 which, here, is a synthetic, crystalline, potassium
sodium alumina silicate molecular sieve, often referred to simply
as a synthetic zeolite. This material is suitable to the product
and process disclosed in that it absorbs moisture, and also can
withstand the braze temperatures described above. The desiccant
material 28 is packed into the tube 26, followed by a firmly packed
filter plug 30, about 25 mm thick, of a binderless felt material of
the general type manufactured by Johns Mansville Co., and referred
to as Micro-fiber Felt-Type E. The filter material is suitable to
the task by virtue of being, again, heat resistant, and also being
fine enough to retain the desiccant particles, but still porous
enough to freely admit refrigerant in and out. The filter plug 30
is followed by a disk shaped aluminum screen 32, which is pressed
down firmly against the filter plug 30 and then crimped in place by
the bottom edge of tube 26 being formed over its outer edge. If
desired, a bleed hole 34 can be added at the top of tube 26.
[0017] Still referring to FIGS. 4 through 6, the sub assembly of
tube 26 along with desiccant 28, filter plug 30 and retention
screen 32 is positioned within the receiver tank 22 before and
during the braze process, as well as retained within receiver tank
22 thereafter, by a locating and retention member in the form of a
crown shaped clip, indicated generally at 36. Clip 36 is also
formed of a metal compatible with the receiver tank 22, with a rim
38 that fits tightly over the outside of tube 26, and a series of
resilient, outwardly extending fingers 40, sized to slide along and
tightly, resiliently engage the inner surface of tank 22 when
inserted, as shown in FIG. 6. Clip 36 locates the entire desiccant
assembly 24 axially above the ports 20 and 21, as well as radially
centered within the inner surface of tank 22, with approximately 3
mm radial clearance all the way around. As such, tube 26 takes
maximum advantage of the interior space within tank 22, but without
blocking refrigerant flow in any direction, and without blocking
the inlet and outlet 20 and 21. Clip 36 is also clad, on both
surfaces, with the same kind of braze material referred to
above.
[0018] Referring finally to FIGS. 6 and 7, after assembly 24 is
installed, a close fitting tank bottom end cap 42 is installed (but
not otherwise attached to tank 22) and the entire assembly of
condenser 10, integral tank 22 and desiccant assembly 24 is
fixtured and sent through a braze oven, indicated schematically at
44. Within oven 44, all parts are heated to the braze melt
temperature (higher than the clad melt temperature, but
significantly lower than the melt temperatures of the base
components themselves). The mechanical retention force of the tight
fitting clip fingers 40 within tank 22 is sufficient to keep tube
26 in place during the braze process, during which time liquid
braze material runs into the interface between clip rim 38 and the
outside of tube 26, as well as the interface between the tips of
clip fingers 40 and the inner surface of tank 22. Post braze, this
solidifies to form a rigid joint between tube 26 and tank 22, just
as at all other structural interfaces. As a consequence of the
structural connection formed during the basic braze process, no
post processing steps are needed either to install the desiccant
assembly or finish the receiver tank. Thus, the method as disclosed
does more than just tolerate or withstand the braze process, it
takes advantage of it, as well, to establish and create a
structural connection. In operation, rising refrigerant flows up
through screen 32, filter plug 30 and into and through the
desiccant charge 28, while any displaced gas exits the bleed hole
34, reversing the process as it falls. The braze joints between
clip 36, tube 26 and tank 22 are sufficient to hold up to vibration
and jostling during later operation of condenser 10, as much so as
for any other brazed joint in the entire structure. In addition,
the resilience of the clip fingers 40 helps to dampen such
jostling, while the radial clearance around tube 26 should prevent
it from colliding with the inside of tank 22.
[0019] Variations in the disclosed embodiment could be made. Any
heat resistant material for tube 26 could work, but the metal
compatible with the tank 22 is preferred, because it can work with
the braze process to establish structural joints, as noted. A tube
26 that was very finely meshed or ventilated could, alone, serve to
expose the desiccant charge 28 to the refrigerant inside tank 22,
while still keeping the desiccant grains from sifting out. However,
the filter plug 30 and screen 32 would generally be more likely to
assure proper exposure and retention of the desiccant grains,
especially if they were likely to pulverize partially over long
use. While the structural use of the braze process is preferred, a
clip like 36 could, for example, use barbs on the fingers 40 and a
very tight interference on the rim 38 so as grab the inner surface
of the receiver tank 22 and the outer surface of tube 26
respectively, and thereby serve to adequately locate and retain the
tube 26. Such a modified clip would tolerate the braze process, and
enable pre braze installation, but without participating in the
braze process per se. Such mechanical force only installation would
require a greater insertion force, however. Theoretically,
something comparable to the stand-off post in U.S. Pat. No.
6,170,287 referred to above, if made of a heat resistant material,
and also designed to be fixed to the desiccant tube 26 as well as
to be fixable to the interior of tank 22 in such a way as to
radially and axially locate the tube 26, would work. The clip 36
disclosed is smaller and lighter, however, and, since it is fixable
axially along the length of the tube 26, and radially between
outside of tube 26 and inside of tank 22, is much more efficient at
maintaining the axial and radial position of tube 26, both in
structural terms and in terms of low weight and material cost.
* * * * *