US20060137855A1

US20060137855A1 - Brazed in place heat exchanger core window and method of making same

Info

Publication number: US20060137855A1
Application number: US11/021,683
Authority: US
Inventors: Thomas Daffron
Original assignee: Behr GmbH and Co KG
Current assignee: Mahle Behr GmbH and Co KG
Priority date: 2004-12-23
Filing date: 2004-12-23
Publication date: 2006-06-29
Also published as: EP1681529A3; EP1681529A2

Abstract

A brazed in place heat exchanger core window is provided comprising a pair of coolant redirection boxes with coolant redirection tubes disposed therebetween. The coolant redirection boxes include a header and a pan, which are press fit to each other via overlapping legs. The headers include guides and slots to facilitate a press fit mating between the core tubes and each header, whereas the pans include ferrules to facilitate a press fit mating between the coolant redirection tubes and each pan. The core window is press fit to the heat exchanger core prior to brazing, and the entire core assembly, including the core window, may be brazed in a single operation.

Description

FIELD OF THE INVENTION

The present invention relates to a heat exchanger core window, which is brazed in place with other heat exchanger core components, and a method for making such a core window in an efficient manner. A heat exchanger including a core window made according to the present invention may be particularly advantageous for use with vehicles employing a front-end power take off.

BACKGROUND OF THE INVENTION

Many industrial vehicles, such as municipal trucks, use mechanical power take off (“PTO”) devices for powering snow plows, refuse packers, cranes and utility equipment. A PTO apparatus typically uses a spinning shaft that is connected to the vehicle's powertrain in order to transfer mechanical power to a hydraulic pump, which in turn is used to control the auxiliary equipment. Front end (or front engine) power take-off (“FEPTO”) uses a shaft extending from the front of a vehicle's engine to power the hydraulic pump, whereas rear end (or rear engine) power take-off (“REPTO”) uses on a shaft emanating from the rear of the engine.
FEPTO is the lowest cost option for most PTO applications. Because of its location at the front of the engine, however, FEPTO shafts must be routed through or around a heat exchanger, such as a radiator, which also is generally located at the front of the engine. The heat exchanger may be raised so that the PTO shaft coming out of the engine runs under, rather than through, it. Alternatively, a modified hole, i.e., a “window,” may be created in the radiator cooling system through which a FEPTO shaft may pass.
The latter design, though commercially expensive, allows a larger sized cooling system to be installed with a FEPTO. Although the window reduces the overall efficiency of the heat exchanger, in some applications the additional size can create a higher performing cooling system than a system that is packaged above the FEPTO.
Prior to the present invention, creating a window for FEPTO in a heat exchanger's core was a time consuming task. First, it was necessary to weld, by hand, a separate box or boxes that redirected coolant into tubes that defined the window. This assembly was then fed into a brazing oven where the remainder of the core was attached. Because of variations in the hand welding process, the typical brazing operation did not result in a adequate seal of the window box(es) with the rest of the core. Consequently, heat exchangers manufactured to include windows for FEPTO shafts previously experienced a much higher failure rate than ordinary heat exchangers. Moreover, because each component of the window was custom made, the creation of a heat exchanger within a core window involved substantially higher costs when compared with windowless cores.

SUMMARY OF THE INVENTION

A brazed in place heat exchanger core window, suitable for use with a motor vehicle, is provided. The core window is defined by a pair of coolant redirection boxes that that are connected by coolant redirection tubes. Each of the redirection boxes includes a header and a pan. These components are press fit to each other and to a conventional heat exchanger core. The components of the coolant boxes are desirably fabricated of the same or similar types of metal as the remainder of the core assembly in order to permit the core window to be brazed in the appropriate location along with the remainder of the heat exchanger components.
In a preferred embodiment, each header of each coolant redirection box includes vertical legs that tightly overlap similar, but oppositely directed, vertical legs on each pan, and each pan further includes at least one opening that allows coolant to flow into and out of each box via redirection tubes. The boxes are press fit to each other and to the heat exchanger core, and the entire heat exchanger, including the assembled core window, is brazed in place in a single process.
This arrangement has the particular advantage that no welding of redirection boxes is required. In addition, the press fit design of the header, pan and redirection tubes, ensure that a conventional brazing process will result in an adequate seal at all junction points.
In a further embodiment, the headers include slots and guides in order to facilitate the quick and proper alignment of the core tubing to the coolant redirection boxes. By maintaining appropriate spacing between the slots and guides, the header, and therefore the entire coolant redirection box, may be quickly assembled to the remainder of the core.
In yet a further embodiment, the pan includes ferrules at each opening. The ferrules insure that the pan, when assembled to the redirection tubes, results in a tight press fit. The ferrules on the pan may overlap the redirection tubes, or, in the alternative, the ferrules may fit within the redirection tubes.
Further objects, features and advantages of the invention, will become apparent from the detailed description of the preferred embodiments that follows, when considered in conjunction with the attached figures of drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are given below with reference to the drawing, in which:
FIG. 1 is an illustration of a heat exchanger that includes a core window;
FIG. 2 is a perspective view of a core window assembly according to an embodiment of the present invention;
FIG. 3 is a top view of a header used in a core window a core window assembly according to an embodiment of the present invention;
FIG. 4 is a section of the header of FIG. 3 taken along the line 4-4;
FIG. 5 is a side view of a header used in a core window a core window assembly according to an embodiment of the present invention;
FIG. 6 is a top view of a pan used in a core window a core window assembly according to an embodiment of the present invention;
FIG. 7 is a section of the pan of FIG. 6 taken along the line 7-7; and
FIG. 8 is a side view of a pan used in a core window assembly according to an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a heat exchanger that is useful in a motor vehicle for cooling engine components. The heat exchanger 1 includes a heat exchanger core 2, which is comprised of core tubes 3 through which coolant passes, and a pair of coolant boxes 4, which direct the passage of coolant through the core tubes. Heat exchanger 1 further includes a window 5, which permits a FEPTO shaft to pass through the core. As discussed above, prior to the present invention, the creation of window 5 was a difficult and time consuming process. The window 5 previously was manually welded and then attached to the core in separate steps. Because of this process, the window could not be efficiently brazed in place along with the remainder of the heat exchanger core. The present invention addresses this problem as is discussed in detail below in conjunction with preferred embodiments.
FIG. 2 shows a perspective view of a preferred embodiment of the present invention. A core window is defined by a first coolant redirection box 6, a first coolant redirection tube 9, a second coolant redirection tube 10, and a second coolant redirection box 11. The first coolant box 6 is comprised of a first header 7 and a first pan 8, and the second coolant box is likewise comprised of a second header 12 and a second pan 13. The components, as described in more detail below, are press fit with each other as illustrated in FIG. 2.
FIG. 3 shows a top view of a preferred embodiment of a header 7 made according to the present invention. Header 7 includes raised guide surfaces 14 and slots 15 into which the heat exchanger core tubes 3 (FIG. 1) may be placed. The header further includes legs 16, 17 that extend perpendicularly from a plane defined by the top surface of the header. Legs 16 and 17 thus extend in the same direction as coolant redirection tubes 9, 10 and heat exchanger core tubes 3.
Because the heat exchanger core 1 is generally placed in an upright position with respect to the vehicle into which it is placed, coolant redirection tubes 9, 10 and heat exchanger core tubes 3 are typically disposed in a “vertical” direction, whereas the tops of coolant boxes 4 and redirection boxes 6 and 12 are typically disposed in a “horizontal” direction. Legs 15 and 16 of header 7 thus may be expressed as also extending in a “vertical” direction. It will be understood by persons of skill in the art, however, that the terms “vertical” and “horizontal” are used to facilitate an explanation of the various embodiments disclosed, and should not be understood as requiring a particular orientation of any component unless expressly so required by an attached claim.
FIG. 4 shows a section through line 4-4 of header 7. This section illustrates end leg 16, which extends in a vertical direction, guide surfaces 14 and slots 15. The raised guide surface 14 facilitates the entry of core tubes 3 into a redirection box.
FIG. 5 is a side elevation of a preferred embodiment of a header 7 made according to the present invention. In this view, legs 16, 17 of header 7 are shown in a vertical orientation. Likewise, guide surfaces 14 extend in a vertical direction. Slots 15 are visible in FIG. 5 and indicated by vertical reference lines. In addition, FIG. 5 illustrates a portion of leg 16, which is designated by reference numeral 18. This leg portion 18 mates, in a press fit arrangement, with a corresponding leg portion of a pan.
FIG. 6 illustrates a top view of a preferred embodiment of a pan 8 made according to the present invention. Pan 8 includes a pair of openings 19, 20, which are maintained in fluid communication with redirection tubes 9, 10 after the core window is assembled. Similar to legs 16, 17 of header 7, pan 8 also includes legs 21, 22. FIG. 7 illustrates a section of pan 8 along the line 7-7. The vertical orientation of leg 22 is visible in FIG. 7. FIG. 7 further illustrates a ferrule 23 on pan 8, which is defined as the opening formed by protruding elements 24 and 25.
Protruding element 24, as illustrated in FIG. 7, is formed as an extension to leg 22. Likewise, protruding element 25 is formed as a bend in pan floor 26. Persons of skill in the art will appreciate variations in the formation of ferrule 23, however. For example, ferrule 23 may be formed by separate components, rather than by bending leg 22 and floor 26. The embodiment as illustrated in FIG. 7, however, is advantageous in that fewer components are required for creation of ferrule 23.
FIG. 8 is a side elevation of a preferred embodiment of pan 8 made according to the present invention. This figure shows the location of ferrule 23 for opening 19 and a corresponding ferrule 27 for opening 20. In addition, pan floor 26 and legs 21, 22 are illustrated. Legs 21 and 22, similar to legs 16 and 17 of header 7, are oriented in a vertical direction to pan floor 26. The size of the opening of ferrules 23 and 27 is determined and controlled in order to insure a snug press fit when the pan is assembled to coolant redirection tubes 9, 10.
In a preferred embodiment, as illustrated in FIGS. 3 through 8, legs 16 and 17 of header 7 overlap legs 21 and 22 of pan 8. The width and depth of header 7 is selected such that these dimensions are marginally greater than the width and depth of pan 8. The margin is determined and controlled in order to insure a snug press fit when the header is assembled to the pan. Persons of skill in the art will appreciate, however, that the press fit arrangement could be reversed, i.e., the width and depth of pan 8 can be selected and controlled to be marginally greater than the width and depth of header 7.
The assembly of a single header 7 with a single pan 8 creates one of the pair of coolant redirection boxes, e.g., box 6, that comprise a window to be placed in the heat exchanger core assembly 2. A second assembly of a header 12 and pan 13 creates a second coolant redirection box, e.g., box 11. In a highly preferred embodiment, the second box is thus identical to the first box. The window is defined by the interconnection of the first coolant redirection box 6 to the second coolant redirection box 11 via coolant tubes 9 and 10. In this arrangement, the second coolant box 11 is oriented in an opposite direction, i.e., flipped, from the orientation of the first coolant box 6.
In order to manufacture a brazed in place heat exchanger core assembly according to a preferred embodiment of the invention, the core window is first assembled by press fitting two headers with two pans to form the needed pair of coolant redirection boxes. In this embodiment, the coolant redirection tubes are thereafter assembled to the coolant redirection boxes via the ferrules located on the pan. The core window is then press fit into the core by inserting the coolant tubes into slots on the redirection box headers. The core window thus may be set in place within the heat exchanger core prior to a brazing operation. As is known in the art, flux may be applied to the joints and the entire assembly may be placed into a brazing oven for brazing.
The foregoing described process of brazing the core window in place is particularly advantageous for assembling heat exchanger cores made of materials that may be difficult to join, e.g., aluminum. In the present invention, the core window components may be selected from any material for which a known brazing or other joining operation exists. In addition, the press fit design of the invention reduces or entirely eliminates the need for separate welding of the coolant redirection boxes, which in turn ensures that the core window will remain tightly sealed with the core when assembled.
While this invention has been described with an emphasis upon particular embodiments, it should be understood that the foregoing description has been limited to the presently contemplated best modes for practicing the invention. For example, the number of coolant redirection tubes described in the foregoing embodiments may be increased or reduced. In other words, a single coolant redirection tube could be employed to interconnect the pair of coolant redirection box. Likewise, three or more coolant tubes could be employed. In this variation, fewer or additional ferrules in the pan would be required to accommodate the lower or higher number of coolant redirection tubes.
It will be apparent that further modifications may be made to the invention, and that some or all of the advantages of the invention may be obtained. Also, the invention is not intended to require each of the above-described features and aspects or combinations thereof. In many instances, certain features and aspects are not essential for practicing other features and aspects. The invention should only be limited by the appended claims and equivalents thereof, since the claims are intended to cover other variations and modifications even though not within their literal scope.

Claims

1. A heat exchanger core window located within a heat exchanger core comprising:

a first coolant redirection box for redirecting coolant within a heat exchanger core, the first coolant redirection box including a header and a pan;

a second coolant redirection box for redirecting coolant within a heat exchanger core, the second coolant redirection box including a header and a pan; and

a first coolant redirection tube disposed between the first and second coolant redirection boxes, wherein each header includes at least one leg that mates in a press fit relationship with at least one corresponding leg on each pan and wherein each pan includes at least one ferrule that mates in a press fit relationship with the first coolant redirected tube.

2. The heat exchanger core window of claim 1 further comprising a second coolant redirection tube disposed between the first and second coolant redirection boxes.

3. The heat exchanger core window of claim 2 wherein each header further includes a plurality of tube slots into which tubes of the heat exchanger core are inserted in a press fit relationship.

4. The heat exchanger core window of claim 3 wherein each header further includes a plurality of tube guides located between the plurality of tube slots.

5. The heat exchanger core window of claim 4 wherein each header further includes a plurality of tube guides located between the plurality of tube slots.

6. The heat exchanger core window of claim 1 wherein each header and each pan has the same number of legs.

7. A heat exchanger core window located within a heat exchanger core comprising:

a first coolant redirection tube disposed between the first and second coolant redirection boxes, wherein each header further includes at least one leg that mates in a press fit relationship with at least one corresponding leg on each pan and each header further includes a plurality of tube slots into which tubes of the heat exchanger core are inserted in a press fit relationship.

8. The heat exchanger core window of claim 7 wherein each header further includes a plurality of tube guides located between the plurality of tube slots.

9. The heat exchanger core window of claim 7 further comprising a second coolant redirection tube disposed between the first and second coolant redirection boxes.

10. The heat exchanger core window of claim 7 wherein each pan includes at least one ferrule that mates in a press fit relationship with the first coolant redirected tube.

11. The heat exchanger core window of claim 10 further comprising a second coolant redirection tube disposed between the first and second coolant redirection boxes.

12. The heat exchanger core window of claim 11 wherein each pan includes a first ferrule that mates in a press fit relationship with the first coolant redirected tube and a second ferrule that mates in a press fit relationship with the second coolant redirected tube.

13. The heat exchanger core window of claim 7 wherein each header and each pan has the same number of legs.

14. A method for making a heat exchanger for use in a motor vehicle, the heat exchanger including a core window fabricated from a pair of headers, a pair of pans and at least one coolant redirection tube, the method comprising:

press fitting each header to each pan to form a pair of coolant redirection boxes;

press fitting a first coolant redirection tube to each of the coolant redirection boxes to define a core window;

press fitting the core window into the core of the heat exchanger; and

brazing the core window in place to the heat exchanger core.

15. The method of claim 14 wherein the step of brazing the core window is conducted simultaneously with brazing the heat exchanger core.

16. The method of claim 15 wherein brazing is conducted in a brazing oven.

17. The method of claim 14 wherein the core window is press fit into the core of the heat exchanger by press fitting coolant tubes of the core into tube slots on each header of each coolant redirection box.

18. The method of claim 14 wherein the first coolant redirection tube is press fit to each of the coolant redirection boxes by press fitting the ends of the first coolant redirection tubes into at least one ferrule located on each pan.

19. The method of claim 18 further comprising the step of press fitting a second coolant redirection tube to each of the coolant redirection boxes.

20. The method of claim 19 wherein the second coolant redirection tube is press fit to each of the coolant redirection boxes by press fitting the ends of the second coolant redirection tubes into a second ferrule located on each pan.