EP0384612A2

EP0384612A2 - In tank oil cooler

Info

Publication number: EP0384612A2
Application number: EP90301265A
Authority: EP
Inventors: Allen K. So; Nicholas F. Avery; David B. Rowntree
Original assignee: Long Manufacturing Ltd
Current assignee: Dana Canada Corp
Priority date: 1989-02-24
Filing date: 1990-02-01
Publication date: 1990-08-29
Also published as: JPH081423U; CA1313182C; KR900013278A; KR0170392B1; KR900013279A; JP2590256Y2; KR960005784B1; JPH02242089A; EP0384612A3

Abstract

A heat exchanger and method of, making same is disclosed. The heat exchanger is particularly useful for cooling automotive engine oil or transmission fluid, the exchanger being located inside the radiator or other part of the engine cooling system. The heat exchanger is made from a plurality of stacked plates (24, 26), the plates being arranged into pre-assembled pairs (12), each pair having a turbulizer (38) located therein. The plates have peripheral tabs (40) which are crimped over to form plate pair sub-assemblies. The plates also have outwardly disposed dimples (36) which are in contact when the sub-assemblies are stacked together to maintain good contact between all heat transfer surfaces while the assembly is completed by brazing.

Description

This invention relates to heat exchangers, and in particular, to automotive oil coolers which are located inside other heat exchangers, such as automotive radiators.
In motor vehicles, it is common to provide heat exchangers for cooling engine oil or transmission fluid. Due to the heat transfer characteristics of oil, liquid cooled heat exchangers are normally used as opposed to air cooled exchangers. The most convenient way to do this is to mount the oil cooler or heat exchanger inside the cooling system of the motor vehicle, and in particular, inside the radiator.
In the past, the oil coolers of the type in question which have been mounted inside automotive radiators have consisted of concentric tubes closed at both ends to form an internal passage for the oil. The engine coolant flows around the outside tube and through the inside tube. A difficulty with this type of oil cooler, however, is that it has relatively low heat transfer efficiency. Also, the pressure drop of the oil flowing through the oil cooler is relatively high.
The present invention is a plate type heat exchanger which has higher efficiency and less pressure drop, and yet is strong enough to withstand the high oil pressures that are frequently encountered in such engine oil or transmission fluid cooling systems.
According to the invention, there is provided a heat exchanger comprising a plurality of stacked plates arranged in pairs, each of the pairs including first and second plates. The first plate has a planar central portion, a raised peripheral co-planar edge portion extending above the central portion, and opposed co-planar end bosses extending below the central portion. The second plate of each plate pair has a peripheral edge portion joined to the first plate peripheral edge portion and a central portion spaced from the first plate central portion. A planar turbulizer is located between the first and second plate central portions in contact therewith. The first plate central portion has a plurality of spaced-apart dimples formed therein, the dimples extending below the central portion equidistant with the end bosses. The first plates of two plate pairs are located back-to-back with the respective dimples and end bosses joined together. Also, each plate pair defines inlet and outlet openings for the flow of fluid through the plate pair past the turbulizer.
According to another aspect of the invention, there is provided a method of making a heat exchanger comprising the steps of providing a plurality of plates, each having a planar central portion with spaced-apart dimples formed therein, a raised peripheral edge portion with spaced-apart tabs projecting outwardly therefrom, and opposed bosses defining inlet and outlet openings at respective opposed plate end portions, said dimples and bosses being located in a common plane. The plates are arranged face-to-face in pairs having a hollow space therebetween. A turbulizer is inserted into the hollow space, the turbulizer being in contact with the planar central portions of each plate of a plate pair. The tabs of one plate are crimped over the peripheral edge portion of the other plate of each plate pair. A plurality of the crimped plate pairs is stacked so that the inlet and outlet openings are in registration and the bosses and dimples of adjacent plates are in contact. Also, the contacting areas of the plates and turbulizers are joined to form a fluid tight assembly.
According to yet another aspect of the invention, there is provided a heat exchanger comprising a plurality of stacked plates arranged in pairs, each of said pairs including first and second plates, the first plate having a planar central portion and a raised peripheral co-planar edge portion extending above the central portion. The second plate of each plate pair has a peripheral edge portion joined to the first plate peripheral edge portion and a central portion spaced from the first plate central portion. A planar turbulizer is located between the first and second plate central portions in contact therewith. The first and second plates each have two tabs, one tab being located at each of respectively diametrically opposed corners of the plate and being crimped over the peripheral edge portion of the respective other plate of each plate pair. The tabs on the first and second plates are located such that tabs are positioned at all four corners of the assembled plate pair. Also, each plate pair defines inlet and outlet openings for the flow of fluid through the plate pair past the turbulizer.
According to yet another aspect of the invention, there is provided a method of making a heat exchanger comprising the steps of providing a plurality of plates each having a planar central portion, a raised peripheral edge portion with spaced-apart tabs projecting outwardly therefrom and inlet and outlet openings formed therein. The plates are arranged face-to-face into pairs having a hollow space therebetween. A turbulizer is inserted into the hollow space, the turbulizer being in contact with the planar central portions of each plate of a plate pair. The tabs of one plate are crimped over the peripheral edge portion of the other plate of each plate pair. A plurality of said crimped plate pairs is stacked so that the inlet and outlet openings are in registration. Also, the contacting areas of the plates and turbulizers are joined to form a fluid tight assembly.
A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a preferred embodiment of an in tank oil cooler according to the present invention;
Figure 2 is an exploded perspective view of a plate pair sub-assembly;
Figure 3 is a sectional view taken along lines 3-3 of Figure 1; and
Figure 4 is a sectional view taken along lines 4-4 of Figure 1.

Referring to the drawings, an oil cooler or heat exchanger 10 is generally represented by reference numeral 10 in Figure 1. Heat exchanger 10 is formed of a plurality of plate pairs 12 as described in detail below with reference to Figure 2. A top plate pair 14 has a smooth top plate 16 and a bottom plate pair 18 has a smooth bottom plate 20, although top and bottom plates 16, 20 could be dimpled as shown in Figure 2 if desired. Heat exchanger 10 also had threaded nipples 22 swaged in place in suitable circular openings in top plate 16. One nipple 22 serves as an inlet and the other nipple 22 serves as an outlet for flow of oil, such as engine oil or transmission fluid through heat exchanger 10.
Referring in particular to Figure 2, a typical plate pair 12 is shown in an exploded perspective view. Plate pair 12 includes a first plate 24 and a second plate 26. First plate 24 has a planar central portion 28, a raised peripheral, co-planar edge portion 30 which extends above or is located in a plane above central portion 28. First plate 24 also includes opposed, co-planar end bosses 32 extending below or located at a lower level than central portion 28.
In the preferred embodiment, the first and second plates 24, 26 are identical, so the terms "below" and "above" with reference to the central portion 28 of first plate 24 would, of course, be reversed with reference to the central portion 28 of second plate 26 as seen in Figure 2.
The ends of plates 16, 20, 24 and 26 are rounded and end bosses 32 of plates 24, 26 are formed with "D"-shaped openings 34. As mentioned above, smooth top plate 16 has circular openings to accommodate nipples 22. The smooth bottom plate 20 has no openings formed therein.
First and second plates 24, 26 are formed with a plurality of spaced-apart dimples 36 formed therein. With reference to first plate 24, dimples 36 extend below the central portion 28 equidistant or to the same planar level as end bosses 32, so that when two of the plates 24, 26 are located back-to-back as seen best in Figure 3, the respective dimples 36 and end bosses 32 are joined together along a common plane.
A turbulizer 38 is located inside each plate pair, including top and bottom plate pairs 14, 18. Turbulizer 38 is a strip of expanded metal. The preferred configuration is parallel rows shaped in a sinusoidal configuration, although other configurations could be used as desired. The length of turbulizer 38 corresponds with the length of the plate central portions 28, and the width of turbulizer 38 corresponds with the distance between peripheral edge portions 30. The thickness of turbulizer 38 is such that after the plate pairs are assembled and heat exchanger 10 is joined together, such as by brazing, the plate central portions 28 are joined to and in good thermal contact with turbulizer 38, as discussed further below.
Dimples 36 are spaced uniformly over the plate central portions 28. One of the primary functions of dimples 36 is to support the plate central portions 28 and prevent these central portions from sagging when the plates are heated to brazing temperatures. Central portions 28 must be kept flat and in full contact with turbulizer 38 during the brazing process in order to obtain good thermal contact between the turbulizer and the plates.
Dimples 36 preferably are large enough to result in flat top surfaces to give a good joint between mating dimples 36. As seen best in Figures 3 and 4, the radius of the shoulders in the dimples should be such that sharp corners should be avoided or the dimples could break out as a result of high pressures in heat exchanger 10.
Dimples 36 should also not be too large in diameter, because the surface area of central portion 28 occupied by dimples 36 is area that is not in contact with turbulizer 38 and this detracts from the heat transfer efficiency of heat exchanger 10. It will be apparent to those skilled in the art that the number and size of the dimples 36 should be chosen so that sufficient strength and structural support for the plate central portions is provided during the brazing process, and that this must be balanced against loss of heat transfer efficiency by making the dimples too numerous or too large. It has been found that for plates with central portions 28 of approximately four centimetres in width, dimples that are 0.5 centimetres in diameter and spaced-apart longitudinally, about 2.5 centimetres and transversely about 2 centimetres provides a preferred balance where aluminum of 0.08 centimetres thickness is used for the plates.
Referring again to Figure 2, plates 24, 26 are formed with tabs 40 at opposed ends. Tabs 40 are located at respective diametrically opposed "corners" of each plate, so that upon assembly, the tabs 40 on one plate, such as first plate 24, are crimped over the peripheral edge portion 30 of the mating plate, such as second plate 26, as seen best in Figure 1. This prevents the plates of each plate pair from moving longitudinally or transversely relative to each other. The crimped plate pairs thus become sub-assemblies to be stacked to complete heat exchanger 10 as described next below.
The assembly of heat exchanger 10 starts by arranging the plates face-to-face into pairs, so that the respective peripheral edge portions 30 are in registration. A turbulizer 38 is then inserted in the hollow space between the central portions 28 of each plate pair. Tabs 40 are then crimped over the peripheral edge portions 30 of the respective mating plate. Several of these assembled plate pairs are then stacked so that the "D"-shaped openings 34 are in registration. The top plate pair 14 is formed by swaging nipples 22 onto smooth top plate 16 and assembling this to one of the plates as shown in Figure 2, again by crimping over tabs 40. Bottom plate pair 18 is then formed using a smooth bottom plate 20 mated to another of the plates as shown in Figure 2 and crimping over the respective tabs 40. The entire assembly is then placed in a brazing furnace to simultaneously braze together all mating surfaces.
In the preferred embodiment, aluminum is used for all of the components of heat exchanger 10. Nipples 22 and turbulizer 38 are formed of plain aluminum, and plates 16, 20, 24 and 26 are formed of self-brazing aluminum, which is aluminum that has a lower melting point cladding or aluminum brazing alloy layer on the outer surfaces which on each side is about 10% of the thickness of the plate. The thickness of turbulizer 38 is such that as this cladding layer melts during the brazing process, all of high areas of turbulizer 38 are brazed to the plate central portions 28 with good thermal heat transfer and minimum drag or pressure drop as the oil flows through or past turbulizers 38.
Having described preferred embodiments of the invention, it will be appreciated that various modifications may be made to the structures described. For example, heat exchange 10 can be made from other materials than aluminum, such as stainless steel or brass. In the case of stainless steel, copper would be used as the brazing cladding layer. Obviously, any number of plate pairs could be used. The length of the plates can be varied simply by repeating longitudinally the dimple diameter and spacing described above. If both the length and the width of the heat exchanger is to be varied, the diameter and spacing of the dimples may have to be varied slightly in keeping with the parameters discussed above.
From the above, it will be appreciated that the oil cooler of the present invention is a relatively high efficiency heat exchanger which is structurally strong with relatively low pressure drop.

Claims

1. A heat exchanger (10) comprising:
a plurality of stacked plates arranged in pairs (12), each of said pairs including first and second plates (24, 26), the first plate (24) having a planar central portion (28), a raised peripheral co-planar edge portion (30) extending above the central portion, and opposed co-planar end bosses (32) extending below the central portion;
the second plate (26) of each plate pair having a peripheral edge portion (30) joined to said first plate peripheral edge portion and a central portion (28) spaced from the first plate central portion;
a planar turbulizer (38) located between the first and second plate central portions (28) in contact therewith;
the first plate central portion having a plurality of spaced-apart dimples (36) formed therein, the dimples extending below the central portion (28) equidistant with the end bosses (30); the first plates (24) of two plate pairs being located back-to-back with the respective dimples (36) and end bosses (30) joined together; and
each plate pair (12) defining inlet and outlet openings (34) for the flow of fluid through the plate pair past the turbulizer.

2. A heat exchanger comprising:
a plurality of stacked plates arranged in pairs (12), each of said pairs including first and second plates (24, 26), the first plate (24) having a planar central portion (28) and a raised peripheral co-planar edge portion (30) extending above the central portion;
the second plate (26) of each plate pair having a peripheral edge portion (30) joined to said first plate peripheral edge portion (30) and a central portion (28) spaced from the first plate central portion;
a planar turbulizer (38) located between the first and second plate central portions (28) in contact therewith;
the first and second plates each having two tabs (40), one tab being located at each of respectively diametrically opposed corners of the plate and being crimped over the peripheral edge portion of the respective other plate of each plate pair, the tabs on the first and second plates being located such that tabs are positioned at all four corners of the assembled plate pair; and each plate pair defining inlet and outlet openings (34) for the flow of fluid through the plate pair past the turbulizer.

3. A heat exchanger as claimed in Claim 1 or Claim 2 wherein the first and second plates (24, 26) of each plate pair are identical.

4. A heat exchanger as claimed in any of Claims 1 to 3 wherein said inlet and outlet openings (34) are formed in the respective opposed bosses (30) of each plate, so that in a stack of plate pairs all inlet openings are in alignment and all outlet openings are in alignment.

5. A heat exchanger as claimed in any of Claims 1 to 4 wherein the plates have rounded ends, and wherein the inlet and outlet openings (34) are "D"-shaped.

6. A heat exchanger as claimed in any of Claims 1 to 5 wherein dimples (36) are spaced uniformly over the plate central portions (28).

7. A heat exchanger as claimed in any of claims 1 to 6 wherein dimples (36) are formed in the plate central portions (28) in a number such that these central portions will remain in full contact with the turbulizer (38) when the plates are heated to brazing temperatures.

8. A heat exchanger as claimed in Claim 6 or 7 wherein the dimples are dimensioaned such that the area of the dimples not in contact with the turbulizer is minimized so as not to detract materially from the heat transfer between the turbulizer and the plate central portions.

9. A heat exchanger as claimed in Claim 1 or any Claim dependent thereon wherein the dimples are formed with generally flat tops.

10. A heat exchanger as claimed in Claim 1 or any Claim dependent thereon wherein at least one of the first and second plates (24, 26) have tabs at opposed ends crimped over the peripheral edge portions of the respective other plate of each plate pair.

11. A heat exchanger as claimed in Claim 10 wherein each plate has two tabs (40), one tab being located at each of respective diametrically opposed corners of the plate.

12. A heat exchanger as claimed in any of Claims 1 to 11 wherein the turbulizer (38) is substantially the same transverse width as the spacing between the plate peripheral edge portions (30).

13. A method of making a heat exchanger comprising:
providing a plurality of plates (24, 26) each having a planar central portion (28), a raised peripheral edge portion (30) with spaced-apart tabs (40) projecting outwardly therefrom and inlet and outlet openings (34) formed therein;
inserting turbulizers (38) into the hollow spaces of between face to face pairs of plates, each turbulizer being in contact with the planar central portions of each plate of a plate pair;
crimping the tabs (40) of one plate over the peripheral edge portion of the other plate of each plate pair;
stacking a plurality of said crimped plate pairs (12) so that said inlet and outlet openings are in registration; and
joining the contacting areas of the plates and turbulizers to form a fluid tight assembly.

14. A method as claimed in Claim 13 wherein the plates and turbulizers are joined together by brazing.

15. A method according to Claim 13 or Claim 14 in which the central portion of each plate is formed with spaced apart dimples and the inlet and outlet openings are defined by bosses at opposed ends of the plates, and the method includes joining the bosses and dimples of adjacent pairs of plates.