U.S. patent application number 10/476877 was filed with the patent office on 2004-09-23 for waste gas heat exchanger.
Invention is credited to Birkert, Arndt, Glockl, Hans, Haarscheidt, Knut.
Application Number | 20040182547 10/476877 |
Document ID | / |
Family ID | 27634759 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040182547 |
Kind Code |
A1 |
Birkert, Arndt ; et
al. |
September 23, 2004 |
Waste gas heat exchanger
Abstract
The invention relates to a heat exchanger, especially a heat
exchanger for motor vehicles, comprising a bank of tubes through
which a gaseous medium flows and around which a liquid coolant
flows. The ends of said tubes are received in tube plates and are
connected to the same in a material fit. The inventive heat
exchanger also comprises a housing jacket which surrounds the bank
of tubes and is connected, at the end thereof, to the tube plates.
A coolant flows through said housing jacket. The tubes (5), tube
plates (3, 7) and housing jacket (2) are produced from a
heat-resistant and corrosion-resistant metallic alloy. According to
the invention, the housing jacket (2) comprises at least one
surrounding expansion flange (4).
Inventors: |
Birkert, Arndt; (Bretzfeld,
DE) ; Glockl, Hans; (Stuttgart, DE) ;
Haarscheidt, Knut; (Stuttgart, DE) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Family ID: |
27634759 |
Appl. No.: |
10/476877 |
Filed: |
November 13, 2003 |
PCT Filed: |
January 21, 2003 |
PCT NO: |
PCT/EP03/00544 |
Current U.S.
Class: |
165/83 ;
165/158 |
Current CPC
Class: |
B21D 26/047 20130101;
Y10S 165/906 20130101; Y02T 10/20 20130101; F28F 2255/10 20130101;
F01N 3/0205 20130101; Y02T 10/16 20130101; F28D 21/0003 20130101;
Y10T 29/4935 20150115; F28D 7/16 20130101; F01N 3/043 20130101;
F02M 26/50 20160201; F02M 26/11 20160201; F01N 2470/10 20130101;
F01N 5/02 20130101; B21D 17/025 20130101; F28F 2265/26 20130101;
F01N 2530/04 20130101; F01N 2240/02 20130101; Y02T 10/12 20130101;
F01N 2260/10 20130101; F02M 26/32 20160201; F28F 9/0236 20130101;
F01N 13/1883 20130101 |
Class at
Publication: |
165/083 ;
165/158 |
International
Class: |
F28F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2002 |
DE |
102 04 107.5 |
Claims
1. A heat exchanger, in particular an exhaust gas heat exchanger
for motor vehicles, having a bank of tubes through which a gaseous
medium flows and around which a liquid coolant flows, and the tubes
of which are held by their tube ends in tube plates and are
connected thereto with a cohesive material joint, and having a
housing jacket which surrounds the bank of tubes and is connected
on the end side to the tube plates with a cohesive material joint
and through which the coolant flows, tubes (5), tube plates (3, 7)
and housing jacket (2) being produced from a heat-resistant and
corrosion-resistant metallic alloy, characterized in that the
housing jacket (2) has at least one encircling expansion bead
(4).
2. The heat exchanger as claimed in claim 1, characterized in that
the housing jacket (2) is of integral design.
3. The heat exchanger as claimed in claim 1 or 2, characterized in
that the housing jacket (2) is produced from a welded tube.
4. The heat exchanger as claimed in claim 1, 2 or 3, characterized
in that the housing jacket has a noncircular cross section (10, 11,
12, 13).
5. The heat exchanger as claimed in one of the preceding claims,
characterized in that the expansion bead (4) is produced by
internal high pressure forming (IHF) of the housing jacket (2).
6. The heat exchanger as claimed in one of the preceding claims,
characterized in that the expansion bead (4) is produced by axial
compression of the housing jacket (2).
7. The heat exchanger as claimed in one of the preceding claims,
characterized in that the housing jacket (2) has a wall thickness
of 0.5.ltoreq.s.ltoreq.2.5 mm, preferably of s.apprxeq.1.5 mm.
8. The heat exchanger as claimed in claim 7, characterized in that
the expansion bead (4) has a height h of 2.ltoreq.h.ltoreq.10 mm,
in particular of h.apprxeq.6 mm.
9. The heat exchanger as claimed in claim 7 or 8, characterized in
that the expansion bead (4) has a width b of 4.ltoreq.b.ltoreq.8
mm, in particular of b.apprxeq.6 mm.
10. The heat exchanger as claimed in one of claims 7, 8 or 9,
characterized in that the ratio of width to height, i.e. b:
h.apprxeq.1.
11. The heat exchanger as claimed in one of claims 7 to 10,
characterized in that the bead (4) has a bending radius of
R3.apprxeq.s.
12. A method for producing an expansion bead (4) in a tubular
housing jacket (2, 20), in particular having a noncircular cross
section, characterized by the following method steps: provision of
a housing jacket (2, 20) which is cut to size, insertion of the
housing jacket (2, 20) into an IHF mold (21, 22, 23) and closing
the mold, filling the mold and the housing jacket (2, 20) with a
liquid pressure medium, deformation of the housing jacket (2, 20)
by building up internal high pressure and producing a preliminary
form (24) of the bead (first deformation step), reduction of the
internal high pressure and production of the final form of the
expansion bead (4) by axial compression of the housing jacket (2,
20) in a second deformation step.
13. The method as claimed in claim 12, characterized in that the
first method step production of a preliminary form (24) of the
bead, and the second method step axial compression of the housing
jacket (2, 20) are carried out in a mold.
Description
[0001] The invention is concerned with a heat exchanger, in
particular an exhaust gas heat exchanger for motor vehicles, in
accordance with the precharacterizing clause of patent claim 1, as
disclosed by DE-A 199 07 163 of the co-applicant. The invention is
furthermore concerned with a method for producing a housing jacket
of an exhaust gas heat exchanger in accordance with the
precharacterizing clause of patent claim 12.
[0002] In the case of the exhaust gas heat exchanger disclosed by
DE-A 199 07 163, a bank of tubes has the exhaust gas of an internal
combustion engine of a motor vehicle flowing through it and is
cooled on the outside by a coolant which is taken from the coolant
circuit of the internal combustion engine. Exhaust gas heat
exchangers of this type, which are also called exhaust gas coolers,
are used nowadays in the exhaust gas recirculation system (EGR) to
cool the exhaust gas. In the case of the known exhaust gas cooler,
the tube ends of the bank of tubes are welded in each case into a
tube plate, i.e. are connected fixedly and tightly to these tube
plates. The tube plates themselves are welded in turn to a housing
jacket which surrounds the bank of tubes. The housing jacket has a
coolant inlet opening and a coolant outlet opening and has the
coolant flowing through it. During operation of an exhaust gas
cooler of this type, the exhaust gas tubes have the hot exhaust gas
flowing through them on the inside and have coolant washing around
them on the outside. This coolant also washes around the inside of
the housing jacket. The exhaust gas tubes therefore reach a
substantially higher temperature than the housing jacket, which
results in different expansions between the exhaust gas tubes and
housing jacket: this leads to thermal stresses, i.e. to compressive
stresses in the tubes and tensile stresses in the housing jacket.
The tubes press on the tube plates and cause deformation or even
damage to the tube/plate connections or the tube plate/housing
connections, i.e. the exhaust gas cooler can become leaky.
[0003] In similar exhaust gas coolers in EP-A 0 930 429 a "sliding
fit" has therefore already been proposed, i.e. the bank of tubes is
arranged in the housing of the exhaust gas cooler by means of a
fixed bearing and a movable bearing, i.e. the tubes can expand
unimpeded owing to the tube plate being mounted in a sliding manner
in the housing. Although thermal stresses are avoided as a result,
an increased structural outlay is required for a sliding fit of
this type; in addition, there is the risk that if the sliding fit
is insufficiently sealed, coolant will pass into the exhaust gas or
exhaust gas will pass into the coolant.
[0004] It is therefore the object of the present invention to
improve a heat exchanger of the type mentioned at the beginning to
the effect that the stresses caused by temperature are compensated
for by simple measures, i.e. impermissible loads on the material
are avoided.
[0005] This object is achieved for the heat exchanger according to
the generic type by the characterizing features of patent claim 1,
i.e. the housing jacket is provided with at least one encircling
expansion bead. This bead provides the housing jacket with
sufficient elasticity in the longitudinal direction of the tubes,
thus making it possible for the housing jacket to expand
elastically so as to follow the more pronounced expansion of the
exhaust gas tubes without in the process being deformed to an
impermissible extent or impairing the weld seam connections between
the tubes and plate and plate and housing. In addition, the
expansion bead can be produced in a simple manner, i.e. without
substantially greater costs, and does not involve any sort of
sealing problems. It is also possible--to increase the elasticity
or to enlarge the spring deflection--to provide a plurality of
extension bead in the manner of an expansion bellows.
[0006] According to one advantageous refinement of the invention,
the housing jacket is produced integrally, for example from a
welded tube, it also being possible for said tube to have a
noncircular cross section, for example a rectangular cross
section.
[0007] According to a further advantageous refinement of the
invention, the expansion bead is produced by "internal high
pressure forming" (IHF) of the housing jacket. The IHF, which is
also called hydroforming, is a process which is known per se and in
which closed housing parts are "inflated" by means of a liquid
pressure medium (water). The housings which are to be deformed are
placed into dies having the appropriate contour and are then acted
upon from the inside by means of a pressure fluid in such a manner
that the material of the housing is placed against the contour of
the mold.
[0008] According to a further advantageous refinement of the
invention, the expansion bead can additionally be produced by axial
compression, i.e. after a bead in preliminary form has been
produced in a first step by IHF.
[0009] In further advantageous refinements of the invention,
dimensions for the housing jacket, in particular the wall thickness
thereof, and the dimension of the expansion bead are specified,
said dimensions being particularly advantageous and resulting in
the desired elasticity of the housing jacket under the loads which
occur. In this case, it is also ensured that the material of the
housing jacket does not over-expand during production of the
expansion bead, but that the designated strength is achieved.
[0010] Finally, one advantageous refinement of the invention
provides a method which enables simple and cost-effective
production of the expansion bead in the housing jacket of the
exhaust gas heat exchanger. According to this method, the expansion
bead is produced in two stages, namely first of all by means of
internal high pressure forming to give a bead which is in a
preliminary form and is not yet in the final form, in particular
does not yet have the final height (external dimensions). In a
second method step, the housing jacket is compressed axially, thus
causing the material of the bead in preliminary form to flow
further outward, and the expansion bead then obtains its final
form. This two-stage method avoids overloading the material and, at
the same time, achieves a defined contour of the expansion bead
with a certain elasticity. This method can be used particularly
easily for the housing jacket and does not cause any change in the
construction of the exhaust gas heat exchanger.
[0011] An exemplary embodiment of the invention is illustrated in
the drawing and will be described in greater detail below. In the
drawing:
[0012] FIG. 1 shows a perspective illustration of part of the
exhaust gas heat exchanger,
[0013] FIG. 2 shows a longitudinal section through the exhaust gas
heat exchanger,
[0014] FIG. 3 shows a cross section through the housing jacket of
the exhaust gas heat exchanger,
[0015] FIG. 4 shows an illustration of a detail of the expansion
bead of the housing jacket,
[0016] FIG. 5 shows a first method step for producing the expansion
bead, and
[0017] FIG. 6 shows a second method step for producing the
expansion bead.
[0018] FIG. 1 shows, in a perspective illustration, part of an
exhaust gas heat exchanger 1 as used in the form of an exhaust gas
cooler for the exhaust gas recirculation system in diesel engines
for motor vehicles. The exhaust gas heat exchanger 1, only the
front half of which is illustrated, has a housing jacket 2 and a
tube plate 3 in which exhaust gas tubes (not illustrated) are
accommodated. An encircling expansion bead 4 is arranged in the
front region of the housing jacket 2, which has approximately a
rectangular cross section with beveled corners. This exhaust gas
heat exchanger 1 is described in greater detail below, the same
reference numbers being used for the same parts.
[0019] FIG. 2 shows the exhaust gas heat exchanger 1 in
longitudinal section in a schematic illustration. The housing
jacket 2 is produced from a closed, i.e. welded tube of stainless
steel. A bank of tubes comprising a multiplicity of exhaust gas
tubes 5 is arranged within this housing jacket 2. These exhaust gas
tubes 5 are likewise produced from a stainless steel alloy which
is, in particular, heat-resistant and corrosion-resistant. The
cross section of the exhaust gas tubes 5 is preferably
rectangular--as is apparent on the basis of the design of the tube
plate 3 in FIG. 1. The exhaust gas tubes 5 are arranged with
respect to one another in such a manner that they leave between
them equidistant gaps 6 through which a liquid coolant, i.e. the
coolant of the cooling circuit of an internal combustion engine
(not illustrated), flows. The ends 5a, 5b of the exhaust gas tubes
5 are held in the tube plate 3 and in a further tube plate 7 and
are welded tightly to these tube plates 3, 7. The tube plates 3, 7
are, for their part, welded in their circumferential regions 3a, 7a
to the housing jacket 2 to the housing jacket 2. The housing jacket
2, the tube plates 3, 7 and the exhaust gas tubes 5 therefore
delimit a defined space for the flow of the coolant. In its
end-side regions 2a and 2b, the housing jacket 2 is somewhat
expanded in terms of its cross section, so that it forms a
respective annular channel 8 and 9 around the bank of tubes at this
point. In this region, the coolant enters through a coolant inlet
(not illustrated), flows through the equidistant gap 6 between the
exhaust gas tubes 5, and passes to the second annular space 9, from
where the coolant leaves the exhaust gas heat exchanger through a
coolant outlet (not illustrated). To this extent, this exhaust gas
heat exchanger is known, for example through the co-applicant's
document which is mentioned at the beginning. The inflow and
outflow of the exhaust gas via a diffuser (not illustrated here) or
an outlet stub is also revealed in this document.
[0020] According to the invention, an expansion bead 4 is arranged
in the housing jacket 2. This expansion bead 4, which can also be
seen in FIG. 1 as the bead which encircles the entire
circumference, gives the housing jacket 2, which is not very
elastic in itself, an elasticity in the longitudinal direction of
the exhaust gas tubes 5, said elasticity permitting the housing
jacket 2 to follow the more pronounced expansion of the exhaust gas
tubes 5. The exhaust gas tubes 5, which have hot exhaust gas
flowing through them on their inside, absorb a higher temperature
during operation than the housing jacket 2, around which the
coolant washes, and therefore "grow" to a greater extent than the
housing jacket. Compressive stresses are therefore produced in the
exhaust gas tubes 5, these stresses continuing into the tube plates
3 and 7 and being transmitted by the latter via the weld seams to
the housing jacket 2, in which a tensile stress then builds up.
This tensile stress is intercepted owing to the elasticity of the
expansion bead 4, so that impermissible deformation or even damage
does not occur.
[0021] FIG. 3 shows a cross section through the housing jacket 2,
i.e. without the bank of tubes being illustrated. The housing
jacket 2 has an approximately rectangular cross section with in
each case two parallel longer side surfaces 10 and 11 and two
somewhat shorter side surfaces 12 and 13 lying opposite each other.
Longitudinal beads 14, 15, 16, 17 for stiffening the entire cross
section are formed in the transition regions of adjacent short and
long side surfaces 12/10, 10/13, 13/11 and 11/12. One of these
beads can also be seen clearly in FIG. 1--denoted by 14 there. The
expansion bead 4 is situated somewhat offset to the rear of the
plane of projection and surrounds the entire cross section of the
housing jacket 2, i.e. it is of encircling design.
[0022] The cross section and the dimensions of this expansion bead
4 are illustrated in FIG. 4. The wall thickness of the housing is
denoted by s and is s.apprxeq.1.5 mm. The bead 4 has a width of
b.apprxeq.6 mm and a height of h.apprxeq.6 mm. The bead is
furthermore characterized by two transition radii R1 and R2 which
correspond approximately to the wall thickness s, i.e. lie in the
region of 1.5 mm. The outermost section of the bead is
characterized by an inner radius of R3.apprxeq.1.5 mm, i.e.
approximately of the wall thickness S. These radii ensure that no
impermissible expansions or stress peaks occur either during
production or during operation.
[0023] FIG. 5 shows a first method step for producing the expansion
bead 4 in the housing jacket 2. The housing jacket 2 is illustrated
here only by a sector 20. The housing jacket 2 is placed into two
mold halves 21 and 22, between which a cavity 23 is provided which
is preferably closed to the outside by an insertable tool 23'. The
housing jacket 20 is acted upon from the inside, illustrated by an
arrow p, by hydroforming or by IHF, so that the housing jacket 20
is deformed in the region of the cavity 23 to the outside to height
h1 and takes on a bead-shaped preliminary form 24. This bead 24 in
preliminary form has a width b1 corresponding to the cavity 23
between the two mold halves 21 and 22.
[0024] FIG. 6 shows the second method step for producing the
expansion bead 4--in this case the housing jacket 20 is arranged
between two axially movable molds 25 and 26. After the hydroforming
according to FIG. 5, the housing jacket 20 is compressed by means
of the molds 25 and 26 in the axial direction, i.e. corresponding
to the arrows F, so that the width of the bead is reduced from b1
(FIG. 5) to b and the height h1 (FIG. 5) is increased to h. After
this method step of axial compression, the bead has obtained its
final form in respect of height and width, i.e. it is finished in
two consecutive different method steps.
[0025] The two method steps can be carried out in one mold, in
which case the insertable tool 23', if the operation is carried out
using an insertable tool of this type, has to be removed for the
second method step. However, it is also possible to carry out the
two method steps in a number of molds or in one follow-on mold.
* * * * *