Heat exchanger

- DENSO Corporation

A heat exchanger has tubes defining first fluid passages through which a first fluid flows therein, an inlet part and an outlet part. Each tube has a first main wall and a second main wall. At least one of the first main wall and the second main wall has a projection projecting outside of the tube along a peripheral end and a first recess and a second recess recessed from the projection. The tubes are stacked such that the first and second main walls are opposed to each other and spaces are provided between the adjacent tubes by the projections. The spaces define second fluid passages through which a second fluid flows. The inlet part is in communication with the second fluid passages through the first recesses and the outlet part is in communication with the second fluid passages through the second recesses.

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Description
CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-27277 filed on Feb. 3, 2006 and No. 2007-012991 filed on Jan. 23, 2007, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanger, which is for example used in an exhaust gas recirculation system (EGR) for performing heat exchange between an exhaust gas and a cooling water.

BACKGROUND OF THE INVENTION

Japanese Unexamined Patent Publication No. 2003-106790 (U.S. Pat. No. 6,595,274 B2) discloses an exhaust gas heat exchanger, which is for example used in an exhaust gas recirculation system. The exhaust gas heat exchanger performs heat exchange between a part of an exhaust gas that is discharged from an engine and returned to an air intake side of the engine and a cooling water, thereby to cool the exhaust gas.

In the exhaust gas heat exchanger, stacked tubes are housed in a tank, and bonnets are coupled to longitudinal ends of the tank. Also, core plates are provided at the longitudinal ends of the tank so as to separate the space inside of the tank from spaces of the bonnets. The longitudinal ends of the tubes are inserted to holes of the core plates. Further, a cooling water inlet pipe and a cooling water outlet pipe are coupled to the tank to make communication with the space defined in the tank.

The cooling water entering from the cooling water inlet pipe flows through spaces (water passages) defined outside of the tubes in the tank and flows out of the tank from the cooling water outlet pipe. On the other hand, the exhaust gas is introduced into gas passages defined inside of the tubes from one of the bonnets. The exhaust gas is collected in the other bonnet and discharged to be returned to the engine. Thus, the exhaust gas is cooled by the cooling water while flowing through the tubes.

In the exhaust gas heat exchanger, the core plates are provided to support the tubes such that the spaces for the water passages are provided between the adjacent tubes. Namely, the core plates will not contribute to heat exchanging performance. In manufacturing the exhaust gas heat exchanger, it is necessary to insert the longitudinal ends of the tubes into the holes of the core plates. Thus, steps increase in the manufacturing process, resulting in increase in manufacturing costs.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a heat exchanger having a structure capable of providing spaces between adjacent tubes without using a core plate.

According to an aspect of the present invention, a heat exchanger has a plurality of tubes, an inlet part and an outlet part. Each of the tubes defines a first fluid passage therein through which a first fluid flows. Each tube has a first main wall and a second main wall, and at least one of the first main wall and the second main wall has a projection projecting outside of the tube and along its peripheral end. A first recess and a second recess are formed on the projection at predetermined positions. The tubes are stacked such that the first main walls and the second main walls are opposed to each other and spaces are provided between the adjacent tubes by the projections. The spaces define second fluid passages through which a second fluid flows. Also, first openings are defined by the first recesses and second openings are defined by the second recesses. The inlet part is disposed in communication with the first openings for introducing the second fluid into the second fluid passages. The outlet part is disposed in communication with the second openings for discharging the second fluid from the second fluid passages.

In this construction, the spaces for the second fluid passages are provided between the adjacent tubes by the projections, without using core plates. Therefore, steps of manufacturing the heat exchanger reduces.

The inlet part is for example constructed of an inlet portion for introducing the second fluid and a distributing portion for distributing the second fluid flowing from the inlet portion into the second fluid passages. The outlet part is for example constructed of a collecting portion for collecting the second fluid having passed through the second fluid passages therein and an outlet portion for discharging the second fluid from the collecting portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a schematic plan view of an EGR gas cooler according to a first embodiment of the present invention;

FIG. 2 is a schematic side view of the EGR gas cooler according to the first embodiment;

FIG. 3 is a schematic side view of the EGR gas cooler when viewed along an arrow Al in FIG. 2;

FIG. 4 is an exploded perspective view of the EGR gas cooler according to the first embodiment;

FIG. 5A is a top view of a tube of the EGR gas cooler according to the first embodiment;

FIG. 5B is a side view of the tube according to the first embodiment;

FIG. 5C is a bottom view of the tube according to the first embodiment;

FIG. 6 is a schematic cross-sectional view of a part of the tube as an example according to the first embodiment;

FIG. 7 is a schematic cross-sectional view of a part of the tube as another example according to the first embodiment;

FIG. 8 is a schematic side view of a stack of tubes of the EGR gas cooler according to the first embodiment;

FIG. 9 is a schematic cross-sectional view of the EGR gas cooler taken along a line IX-IX in FIG. 1;

FIG. 10 is a cross-sectional view of the EGR gas cooler taken along a line X-X in FIG. 2;

FIG. 11 is a schematic cross-sectional view of a joining portion between a first tank member and a second tank member of the EGR gas cooler according to the first embodiment;

FIG. 12 is a schematic cross-sectional view of the EGR gas cooler taken along a line XII-XII in FIG. 9; and

FIG. 13 is a schematic cross-sectional view of an EGR gas cooler according to a second embodiment of the present invention.

 DETAILED DESCRIPTION OF EMBODIMENT

A first embodiment will be described with reference to FIGS. 1 to 12. A heat exchanger shown in FIG. 1 is for example used as an EGR gas cooler for an exhaust gas recirculation system (EGR) of a diesel engine.

As shown in FIGS. 1 to 4, an EGR gas cooler 100 performs heat exchange between an exhaust gas (first fluid) to be returned to an engine of a vehicle and an engine cooling water (second fluid), thereby cooling the exhaust gas. In the drawings, arrows CW denote flows of the cooling water, and arrows EG denote flows of the exhaust gas.

Components of the EGR gas cooler 100 are made of materials, such as stainless, having sufficient strength and sufficient resistance to corrosion. The respective components are joined by such as brazing or welding.

The EGR gas cooler 100 has a stack of tubes 110, a water tank 130, a first gas tank 151, and a second gas tank 152. As shown in FIGS. 5A to 9, each tube 110 has a substantially flat tubular shape and defines a gas passage (first fluid passage) 114 therein through which the exhaust gas flows. The tube 110 has a substantially rectangular-shaped cross-section.

For example, each tube 110 is constructed of a first tube plate (first tube member) 110a and a second tube plate (second tube member) 110b. Each of the first and second tube plates 110a, 110b is shaped from a flat plate member such as by pressing or rolling to have a substantially U-shaped cross-section. Specifically, the tube plate 110a, 110b has a main wall and side walls on opposite sides of the main wall.

As shown in FIG. 6, the first and second tube plates 110a, 110b are joined such that the respective side walls partly overlap with each other. FIG. 6 shows an example in which the side walls overlap at a substantially middle portion of a side of the tube 110. FIG. 7 shows another example in which the side walls overlap at a position close to the main wall of the second tube plate 110b. The main wall of each tube plate 110a, 110b provides a tube main wall (opposed wall) 111. The joined side walls of the tube plate 110a, 110b provide tube side walls 118.

The tube 110 has an inner fin 120 therein. The inner fin 120 is for example a corrugated fin and formed from a thin plate member by pressing. For example, the inner fin 120 is interposed between the first and second tube plates 110a, 110b and joined such as by brazing. As such, the inner fin 120 is joined to inner surfaces of the tube main walls 111.

The tubes 110 are stacked such that the tube main walls 111 are opposed to each other, as shown in FIGS. 4, 8 and 9. The gas passages 114 are formed within the tubes 110. On the other hand, water passages (second fluid passages) 115 through which the cooling water flows are provided by spaces defined between the adjacent tubes 110. The main walls 111 of the outermost tubes 110, which are disposed on outermost layers of the stack of the tubes 110, provide outermost tube walls 111a.

Each of the tube 110 has projections 112 and recesses 113 on its both main walls 111, as shown in FIGS. 5A to 5C. Here, all tubes 110 have the same structure. Thus, the outermost tubes 110 also have the projections 112 and the recesses 113 on the outermost tube walls 111a, as shown in FIG. 4.

The projection 112 projects outwardly from the tube main wall 111. The projection 112 is for example formed by pressing. The projection 112 is formed along a peripheral end of the tube main wall 111 like a continuous dam.

The recesses 113 are recessed from a top end of the projection 112 toward the tube main wall 111. Each recess 113 has a predetermined length in a longitudinal direction of the tube main wall 111. The dimension of the recess 113 is for example equal to the dimension (height) of the projection 112 in a direction perpendicular to the tube main wall 111. In other words, the projection 112 is not formed at a part corresponding to the recess 113.

Here, two recesses 113 are formed on each tube main wall 111. Also, the recesses 113 are located on diagonal positions and along longitudinal sides of the tube main wall 111.

Further, the tube 110 has first raised portions 116 on both tube main walls 111 thereof. The first raised portions 116 are arranged at predetermined intervals over the tube main wall 111. Each raised portion 116 projects outwardly from the tube main wall 111 in a form of tube and has the same dimension (height) as the projection 112 in a direction perpendicular to the tube main wall 111.

The tube 110 further has second raised portions 117 on both tube main walls 111 thereof as flow-adjusting portions for adjusting or arranging the flow of the cooling water. Each second raised portion 117 is located adjacent to one of the recesses 113 (left recess in FIGS. 5A and 5C, hereafter, referred to as a first recess 113), which is located upstream of the other recess 113 with respect to the flow of the cooling water.

The second raised portion 117 extends parallel to a short side of the tube main wall 111, i.e., extends perpendicular to a longitudinal direction of the tube 110. The second raised portion 117 has the same height as the projection 112. Further, the second raised portion 117 is located closer to a first end 112a of a first portion of the projection 112 than a second end 112b of the projection 112 with respect to the longitudinal direction of the tube main wall 111. The first portion extends along the longitudinal side of the tube main wall 111, and the second portion extends along the short side of the tube main wall 111.

Furthermore, the second raised portion 117 is located such that a distance between its first end (upstream end) 117a and the longitudinal side of the tube main wall 111 is smaller than a distance between its second end (downstream end) 117b and the opposite longitudinal side of the tube main wall 111, with respect to a direction perpendicular to the longitudinal direction of the tube 110.

As shown in FIG. 8, the tubes 110 having the above structure are stacked such that the respective projections 112 are opposed and in contact with each other. As such, the tubes 110 are joined to each other at the projections 112. In this case, the first raised portions 116 and the second raised portion 117 have the same height as the projection 112. Thus, the adjacent tubes 110 are also in contact with and are joined at the first raised portions 116 and the second raised portion 117. Further, the inner fins 120 are joined to the inner surfaces of the tubes 110. Accordingly, the strength of the stack of the tubes 110 improves.

In the stack of the tubes 110, spaces are provided between the adjacent tubes since the projections 112 are formed on the tube main walls 111. Each space is surrounded by the projections 112. As such, the cooling water passage 115 is defined by this space except for the first raised portions 116 and the second raised portions 117, as shown in FIGS. 9 and 12.

Further, openings 113a are provided by the recesses 113 of the adjacent tubes 110. Here, the openings 113a provided by the first recesses 113, which are adjacent to the second raised portions 117, define inlet opening 113a for introducing the cooling water into the cooling water passages 115. The openings 113b provided by the second recesses 113 (right recesses 113 in FIG. 5B), which are further from the second raised portion 117, define outlet openings 113b for discharging the cooling water from the cooling water passages 115.

The water tank 130 includes a first tank member 130a and a second tank member 130b, which are arranged in the longitudinal direction of the tubes 110. The first tank member 130a is disposed adjacent to the inlet openings 113a of the stack of the tubes 110, and the second tank member 130b is disposed adjacent to the outlet openings 113b of the stack of the tubes 110.

Each of the first and second tank members 130a, 130b has a substantially U-shape and includes outer walls 131 and a connecting wall 132 between the outer walls 131. The outer walls 131 are parallel to each other. The first and second tank members 130a, 130b are formed from plate members by bending, for example.

The first and second tank members 130a, 130b are coupled to the stack of the tubes 110 so as to substantially surround the stack of the tubes 110. Thus, the outer walls 131 are opposed to the outermost tube walls 111a and the connecting walls 132 are opposed to the tube side walls 118.

In this case, since the inlet openings 113a and the outlet openings 113b are located on diagonal positions of the stack of the tubes 110, the first and second tank members 130a, 130b are coupled from opposite sides of the stack of the tubes 110. Specifically, the connecting portion 132 of the first tank member 130a are opposed to the inlet openings 113a, and the connecting portion 132 of the second tank member 130b are opposed to the outlet openings 113b.

Further, as shown in FIG. 11, the first and second tank members 130a, 130b are engaged with each other at ends thereof such that the outer walls 131 thereof share a plane. Thus, the first and second tank members 130a, 130b are engaged at a substantially middle position of the stack of the tubes 110 in the longitudinal direction of the tubes 110. For example, the ends of the first and second tank members 130a, 130b overlap with each other.

Although the first and second tank members 130a, 130b are coupled to the stack of the tubes 110 in opposite directions, these have the same shape. Thus, the specific shape of the first and second tank members 130a, 130b is described hereafter about the first tank member 130a as an example.

As shown in FIGS. 1, 2 and 10, a peripheral end of each outer wall 131 is in contact with and joined to the projection 112 of the outermost tube wall 111a. A main portion of each outer wall 131, other than the peripheral end, is raised from the peripheral end in an outward direction of the U-shaped tank member 130a. Further, first recesses 135, a second recess 136, and reinforcement ribs 137 are formed on the raised main portion of each outer wall 131.

The first recesses 135 are recessed from the raised main portion so as to be in contact with and joined to the first raised portions 116 of the outermost tube wall 111a. The second recess 136 is recessed from the raised main portion so as to be in contact with and joined to the second raised portion 117 of the outermost tube wall 111a, as the flow-adjusting portion. The reinforcement ribs 137 are located between the first recesses 135 and project from the raised main wall, as shown in FIG. 2.

As shown in FIGS. 9 and 10, a space is provided between one outer wall 131 and the outermost tube wall 111a. The space is surrounded by the peripheral end of the outer wall 131 and the projection 112 of the outermost tube wall 111a. Thus, similar to the cooling water passages 115, an end water passage 115a is defined by this space except for the first raised portions 116, the first recesses 135 and the second raised portion 117 and the second recess 136.

Further, as shown in FIG. 8, an end opening 113c is formed between the outer wall 131 and the first recess 113 of the outermost tube 110 for introducing the cooling water into the end water passage 115a. Likewise, the end opening 113c is formed between the outer wall 131 and the second recess 113 of the outermost tube 110 for discharging the cooling water from the end water passage 115a.

The connecting wall 132 of the first tank member 130a is in contact with and joined to the side walls 118 on which the inlet openings 113a, 113c are formed. Likewise, the connecting wall 132 of the second tank member 130b is in contact with and joined to the side walls 118 on which the outlet openings 113a, 113c are formed.

The first tank member 130a is also formed with a bulge 133. The bulge 133 expands in an outward direction of the first tank member 130a and extends over the outer walls 131 and the connecting wall 132. In the connecting wall 132, the bulge 133 is opposed to the inlet openings 131a, 131c so as to cover or encases the inlet openings 131a, 131c, and a clearance 133a is defined between an inner surface of the bulge 133 and the inlet openings 113a, 113c of the tubes 110, as shown in FIG. 12. The clearance 133a is in communication with the water passages 115, 115a thorough the inlet openings 113a, 113c. Further, the end water passages 115a are partly expanded by the bulge 133 formed on the outer walls 131, as shown in FIG. 9.

As shown in FIGS. 4 and 12, a pipe hole 134 is formed on the bulge 133. A water inlet pipe (pipe member) 141 is coupled to the inlet hole 134. Thus, the water passages 115, 115a are in communication with an outside of the EGR gas cooler 100 through the inlet openings 113a, 113c, the clearance 133a, the pipe hole 134 and the water inlet pipe 141. Thus, an inlet part is provided by the water inlet pipe 141 and the bulge 133 (clearance 133a) of the first tank member 130a. The water inlet pipe 141 corresponds to an inlet portion for introducing the cooling water into the clearance 133a of the bulge 133, and the bulge 133 (clearance 133a) corresponds to a distribution portion for distributing the cooling water into the water passages 115, 115a.

Likewise, a water outlet pipe (pipe member) 142 is coupled to the bulge 133 of the second tank member 130b. The water passages 115, 115a are also in communication with the outside through the outlet openings 113b, 113c, the clearance 113a, the pipe hole 134 and the water outlet pipe 142. Thus, an outlet part is provided by the water outlet pipe 142 and the bulge 133 (clearance 133a) of the second tank member 130b. The bulge 133a (clearance 133a) corresponds to a collecting portion for collecting the cooling water discharged from the water passages 115, 115a and the water outlet pipe 142 corresponds to an outlet portion for discharging the cooling water from the collecting portion to the outside.

The first gas tank 151 and the second gas tank 152 are coupled to the longitudinal end of the stack of the tubes 110. For example, the first gas tank 151 is coupled to the first end adjacent to the inlet part, and the second gas tank 152 is coupled to the second end adjacent to the outlet part.

The first gas tank 151 has a cup shape for defining a tank space therein. The first gas tank 151 is coupled such that its end defining an opening is in contact with and joined to the peripheral portions of the first ends of the stacked tubes 110 and the end of the first tank member 130a. Thus, the tank space of the first gas tank 151 is in communication with the gas passages 114 defined inside of the tubes 110.

Further, a gas inlet pipe 151 a is coupled to a side wall of the first gas tank 151 to be in communication with the tank space. For example, the gas inlet pipe 151a and the water inlet pipe 141 are disposed on the same side of the EGR gas cooler 100. The gas inlet pipe 151a has a flange 151b to be coupled to the exhaust gas recirculation system. As such, the gas passages 141 are in communication with the exhaust gas recirculation system through the first gas tank 151 and the gas inlet pipe 151a.

The second gas tank 152 has the shape similar to the first gas tank 151. The second gas tank 152 is coupled such that its end defining an opening is in contact with and joined to the peripheral portions of the second ends of the stacked tubes 110 and the end of the second tank member 130b. Thus, a tank space defined in the second gas tank 152 is in communication with the gas passages 114.

Further, a gas outlet pipe 152a is coupled to a side wall of the second gas tank 152. For example, the gas outlet pipe 152a is disposed on the same side as the gas inlet pipe 151a and the water inlet pipe 141. The gas outlet pipe 152a has a flange 152b at its end. Thus, the exhaust gas having passed through the gas passages 114 is discharged from the EGR gas cooler 100 through the second gas tank 152 and the gas outlet pipe 152a.

In this EGR gas cooler 100, as shown by the arrows EG in FIG. 1, a part of the exhaust gas discharged from the engine flows in the gas passages 114 from the inlet gas pipe 151a, the first gas tank 151. The exhaust gas having passed through the gas passages 114 is discharged through the second gas tank 152 and the gas outlet pipe 152a and returned to the engine.

On the other hand, as shown by the arrows CW in FIG. 1, the engine cooling water flows in the water passages 115, 115a from the inlet part provided by the water inlet pipe 141, the clearance 133a and the inlet openings 113a, 113c. The cooling water having passed through the water passages 115, 115a are discharged from the inlet part provided by the outlet openings 113b, 113c, the clearance 133a, and the water outlet pipe 142.

As such, the heat exchange is performed between the exhaust gas flowing through the gas passages 114 and the cooling water flowing through the water passages 115, 115a. As a result, the exhaust gas is cooled.

In a general heat exchanger, tube holes are formed on core plates at predetermined intervals and ends of the tubes are inserted to tube holes of the core plates. That is, the tubes are held with predetermined spaces by the core plates so as to provide passages between the adjacent tubes.

In the EGR gas cooler 100, the projections 112 and the recesses 113 are formed on the tube main walls 111. Thus, the water passages 115 are defined by the spaces provided between the tube main walls 111 of the adjacent tubes 110, and the inlet and outlet openings 113a, 113b, 113c are provided by the recesses 113.

Accordingly, the gas passages 114 and the water passages 115 are separated without requiring core plates. That is, the water passages 115 are provided without using the core plates. Also, since the core plates are not required, a step of inserting the ends of the tubes into the holes of the core plates is not necessary in manufacturing the EGR gas cooler 100. Therefore, manufacturing cots of the EGR gas cooler 100 reduce.

In this embodiment, the dimension of the recesses 113 is equal to the height of the projections 112. Therefore, the size of the inlet and outlet openings 113a, 113b is increased. Thus, resistance of the cooling water to flow in and out of the water passages 115 reduces.

Also, the inlet openings 113a and the outlet openings 113b are located on diagonal positions of the tube main walls 111. Therefore, a region where the cooling water easily stagnate is reduced. Namely, it is less likely that the cooling water will stagnate in the water passage 115. Accordingly, heat exchange efficiency improves.

Further, the second raised portions 117 are formed on the tube main walls 111 as the flow-adjusting portions. Therefore, the cooling water entering from the inlet openings 113a, 113c can be directed toward the second ends 117b of the second raised portions 117 to flow further inside of the tubes 110, as shown by a dashed arrow CW1 in FIG. 5A. As such, the cooling water can be substantially uniformly introduced over the water passages 115. Namely, the heat exchange is performed by effectively using the tube main walls 111. Accordingly, the heat exchange efficiency improves.

In a case that the cooling water stagnates in the water passage 115 at a position corresponding to a portion where the high temperature exhaust gas flows, heat exchange is excessively performed, resulting in boiling of the cooling water. In the embodiment, however, the second raised portion 117 is formed at an upstream side of each tube main wall 111 with respect to the flow of the exhaust gas. Therefore, it is less likely that the cooling water will boil due to the excess heat exchange.

In the embodiment, each tube 110 is constructed by joining the first and second tube plates 110a, 110b. The first and second tube plates 110a, 110b are formed such as by bending, pressing, rolling and the like. Therefore, the tubes 110 are produced easily and with reduced costs, as compared with a case in which a tube is formed by shaping a cylindrical tube member into a flat tubular shape.

In addition, since the inner fins 120 are provided in the gas passages 114 of the tubes 110, turbulence effect is provided to the flow of the exhaust gas. As such, the heat exchange efficiency further improves.

The projections 112 and the recesses 113 are also formed on the outermost tube walls 111a of the outermost tubes 110, and the outer walls 131 of the tank members 130a, 130b are joined to the projections 112 of the outermost tube walls 111a. Therefore, the end water passages 115a with the end inlet and outlet openings 113c are formed between the outermost tube walls 111a and the outer walls 131. As such, since the heat exchange area increases, the heat exchange efficiency improves.

In each tank members 130a, 130b, the outer walls 131 are connected through the connecting wall 132. Namely, the outer walls 131 are integrally formed into the tank member 130a, 130b. Therefore, the tank member 130a, 130b is easily coupled to the stack of the tubes 110 by inserting the stack of the tubes 110 into the space defined between the outer walls 131.

The connecting walls 132 of the first and second tank members 130a, 130b are opposed to and joined to the side walls 118 of the tubes 110. The bulges 133 are formed on the connecting walls 132 at positions corresponding to the inlet and outlet openings 113a, 113b, 113c such that the clearances 133a are provided between the inner surfaces of the bulges 133 and the inlet and outlet openings 113a, 113b, 113c. Further, the water inlet pipe 141 and the water outlet pipe 142 are coupled to the pipe holes 134 formed on the bulges 133.

As such, the inlet part and the outlet part are provided by the bulges 133 and the water inlet and outlet pipes 141, 142. Namely, The inlet part and the outlet part are formed with simple structure. With this configuration, expansion loss or reduction loss while the cooling water flows into and out of the water passages 115, 115a reduces. That is, because pressure loss of the flow of the cooling water reduces, the heat exchange efficiency improves.

Second Embodiment

A second embodiment will be described with reference to FIG. 13. In the second embodiment, a EGR gas cooler 100A has bypass tubes 110A and a partition wall 160 in addition to the structure of the EGR gas cooler 100 of the first embodiment. In FIG. 13, the water inlet part is exemplary shown because a water inlet part and a water outlet part have the similar structure.

The bypass tubes 110A are stacked on one side (lower side in FIG. 13) of the stack of the tubes 110. The bypass tubes 110A define the gas passages 114 through which the exhaust gas flows, similar to the tubes 110. The partition wall 160 is interposed between the tube 110 and the bypass tube 110A. The partition wall 160 is for example made of stainless and has a rectangular shape. The stack of the tubes 110, partition wall 160 and bypass tubes 110A is disposed in the water tank 130.

Similar to the first embodiment, the water tank 130 includes the first tank member 130a and the second tank member 130b. The stack of the tubes 110, partition wall 160 and the bypass tubes 110A are located between the outer walls 131 of the tank members 130a, 130b.

An end tube 110s, which is one of the tubes 110 and is opposed to the partition wall 160, has a projection 112, similar to the other tubes 110. Thus, the end tube 110s is in contact with and joined to the partition wall 160 at the projection 112. An end water passage 115b is formed between the tube main wall 111 of the end tube 110s and the partition wall 160.

Further, the recesses 113 are formed on the end tube 110s. Thus, an inlet opening 113d is provided between the recess 113 of the end tube 110s and the partition wall 160. The end water passage 115b is in communication with the clearance 133a through the inlet opening 113d.

In the example of FIG. 13, the EGR gas cooler 100A has two bypass tubes 110A. Similar to the tubes 110, each of the bypass tubes 110A is constructed of a first tube plate and a second tube plate. The bypass tubes 110A define the gas passages 114 therein through which the exhaust gas flows. Although not illustrated, reinforcement plates are interposed between the first and second tube plates and joined to inner walls of the first and second tube plates. Each reinforcement plate has a crank shape in its cross-section with a pitch greater than that of the inner fin 120 of the first embodiment.

The bypass tubes 110A are formed with projections 112A, similar to the projections 112 of the tubes 110. Thus, the bypass tubes 110A are stacked such that the projections 112A are opposed to and joined to each other. Further, spaces are provided between the adjacent bypass tubes 110A as thermal insulation spaces.

A first end bypass tube 110A1, which is one of the bypass tubes 110A and is opposed to the partition wall 160, is joined to the partition wall 160 at the projection 112A thereof. Thus, the thermal insulation space 115c is also provided between the partition wall 160 and the tube main wall of the first end bypass tube 110A1.

A second end bypass tube 110A2, which is one of the bypass tubes 110A and is opposed to the outer wall 131, is joined to the outer wall 131 through the projection 112A thereof. Thus, the thermal insulation space 115c is also provided between the tube main wall of the second end bypass tube 110A2 and the outer wall 131.

A portion of the partition wall 160, which corresponds to the bulge 133, extends across the clearance 113a. The end of the portion of the partition wall 160 is in contact with and joined to an inner wall of the bulge 133. Therefore, the thermal insulation spaces 115c defined outside of the bypass tubes 110A are separated from the water passages 115, 115a, 115b defined outside of the tubes 110 and the clearance 113a by the partition wall 160. As such, the cooling water is not allowed to enter the thermal insulation spaces 115c.

In the EGR gas cooler 100A, the bypass tubes 110A are provided to allow the part of the exhaust gas to flow therein. On the other hand, since the cooling water is not introduced into the bypass tubes 110A, heat exchange with the cooling water is reduced in the bypass tubes 110A.

For example, a valve device is provided in the first gas tank 151 to control the volume of the exhaust gas to be introduced into the bypass tubes 110A. The valve device can be controlled to permit the exhaust gas to both of the tubes 110 and the bypass tubes 110A or only to the tubes 110. Because the volume ratio of the exhaust gas into the tubes 110 to the exhaust gas into the bypass tubes 110A can be controlled, a temperature of the exhaust gas is controlled.

Since the thermal insulation space 115c is provided between the first end bypass tube 110A1 and the partition wall 160, heat exchange between the exhaust gas flowing in the first end bypass tube 110A1 and the cooling water flowing in the end water passage 115b is reduced. On the other hand, since the end water passage 115b is provided between the partition wall 160 and the end tube 110s, cooling effect of the exhaust gas in the end tube 110s improves. Accordingly, heat exchange efficiency improves.

In the second embodiment, the bypass tubes 110A only have the projections 112 for providing thermal insulation spaces 115c. That is, the recesses 113 are not formed on the bypass tubes 110A. However, the bypass tubes 110A may have the recesses 113. Namely, the bypass tubes 110A can be constructed by using the tubes 110.

In the above description, the ERG gas cooler 100A has two bypass tubes 110A. However, the number of the bypass tubes 110A is not particularly limited to two. The number of the bypass tubes 110A can be changed in accordance with the required degree of change of the exhaust gas temperature.

Also, the reinforcement plates are provided and joined in the bypass tubes 110A. Instead of the reinforcement plates, recesses recessed from the tube main walls 111 toward the inside of the bypass tubes 110A can be formed, and the recesses of the opposed tube main walls are joined to each other inside of the bypass tubes 110A.

Other Embodiments

The shape and/or dimension of the recesses 113 can be modified. In the above embodiments, the dimension of the recesses 113 is equal to the height of the projections 112. However, the dimension of the recesses 113 may reduced depending on resistance of the cooling water to pass through the inlet openings 113a, 113c and the outlet openings 113b, 113c. Alternatively, the dimension of the recesses 113 may be larger than the height of the projections 112.

The positions of the recesses 113 can be modified. Instead of the diagonal positions, the recesses 113 may be formed on the same longitudinal side of the tubes 110. In this case, the water inlet pipe 141 and the water outlet pipe 142 are coupled to the same side of the stack of the tubes 110. Therefore, it is not necessary that the water tank 130 is constructed of two tank members 130a, 130b. Namely, the water tank 130 can be constructed of a single tank member.

In the above embodiments, the second raised portions 117 are formed parallel to the short side of the tubes 110. However, the second raised portions 117 may be modified in accordance with flow conditions of the cooling water. For example, the second raised portion 117 can be inclined relative to the short side of the tube 110 such that a distance between the longitudinal end of the tube 110 and the second raised portion 117 gradually increases with a distance from the inlet opening 113a. Alternatively, the second raised portion 117 may have a curved shape. Further, each of the flow-adjusting portion may be provided by a plurality of second raised portion 117. That is, the second raised portion 117 may be divided into plural portions. Furthermore, the second raised portions 117 may be eliminated.

Further, it is not always necessary that each tube 110 is constructed of the first and second tube plates 110a, 110b. For example, the tube 110 can be formed by a single pipe member.

In the above embodiments, the projections 112 are formed on both tube main walls 111 of each tube 110, 110A. However, the projections 112 may be formed on only one of the tube main walls of the tube 110, 110A. In this case, the tubes 110, 110A may be stacked such that the tube main wall 111 on which the projection 112 is formed is opposed to the tube main wall 111 of the adjacent tube 110, 110A on which the projection 112 is not formed. Also in this case, the spaces are provided between the adjacent tubes 110, 110A.

Also, the inner fins 120 may be eliminated in accordance with required heat exchange efficiency. Further, one of or both of the outer walls 131 of the water tank 130 may be eliminated in accordance with the required heat exchange efficiency of the exhaust gas.

Also, it is not always necessary that the water tank 130 has the bulges 133. For example, the pipe hole 134 can be enlarged over an area where the inlet openings 113a or the outlet openings 113b are formed, and a bore size of the end of the pipes 141, 142 can be increased so as to correspond to the size of the pipe hole 134. In this case, the bulge 133 can be eliminated. Thus, the end of the pipe 141a corresponds to the distributing portion of the inlet part and the end of the pipe 142 corresponds to the collecting portion of the outlet part.

Further, use of the present invention is not limited to the EGR gas cooler, but can be employed to any other heat exchangers. For example, the heat exchanger 100 can be used as an exhaust gas recovery heat exchanger that performs heat exchange between the exhaust gas, which is discharged to air, and the cooling water, thereby to heat the cooling water.

Also, the material of the components of the heat exchanger is not limited to stainless steel. The components can be made of other materials such as aluminum alloy, or copper alloy depending on conditions in use.

The example embodiments of the present invention are described above. However, the present invention is not limited to the above example embodiments, but may be implemented in other ways without departing from the spirit of the invention.

Claims

1. A heat exchanger for performing heat exchange between a first fluid and a second fluid, comprising:

a plurality of tubes, each of the tubes defining a first fluid passage therein through which the first fluid flows and having a first main wall and a second main wall, wherein at least one of the first main wall and the second main wall has a projection along its peripheral end, a first recess and a second recess, the projection projects outside of the tube, the first and second recesses are recessed from an end of the projection at predetermined positions, wherein the tubes are stacked such that the first main walls and the second main walls are opposed to each other, second fluid passages through which the second fluid flows are defined by spaces provided between opposed first and second main walls of the adjacent tubes and surrounded by the projections, first openings communicating with the second fluid passages are defined by the first recesses, and second openings communicating with the second fluid passages are defined by the second recesses;
a second fluid inlet part disposed in communication with the first openings for introducing the second fluid into the second fluid passages; and
a second fluid outlet part disposed in communication with the second openings for discharging the second fluid from the second fluid passages.

2. The heat exchanger according to claim 1, wherein

the second fluid inlet part includes an inlet portion for introducing the second fluid and a distributing portion disposed downstream of the inlet portion with respect to a flow of the second fluid for distributing the second fluid flowing from the inlet portion into the second fluid passages, and
the second fluid outlet part includes a collecting portion for collecting the second fluid having passed through the second fluid passages therein and an outlet portion for discharging the second fluid from the collecting portion.

3. The heat exchanger according to claim 1, wherein

both of the first and second main walls have the projections, the first recess and the second recess, and
the tubes are stacked such that the projections of the adjacent two tubes are opposed to and in contact with each other, the first recesses of the adjacent two tubes are opposed to each other to define the first opening and the second recesses of the adjacent two tubes are opposed to each other to define the second opening.

4. The heat exchanger according to claim 1, wherein each of the first and second recesses has a dimension equal to a dimension of the projection with respect to a direction perpendicular to the first and second main walls.

5. The heat exchanger according to claim 1, wherein

the first and second main walls have a substantially rectangular shape, and
the first and second recesses are located along longitudinal sides of the rectangular shape and on diagonal positions.

6. The heat exchanger according to claim 1, wherein

each of the tubes has a flow-adjusting portion on at least one of the first main wall and the second main wall at a position corresponding to an upstream location respect to a flow of the first fluid flowing in the first fluid passage, and
the flow-adjusting portion is configured such that the second fluid is spread throughout the second fluid passage.

7. The heat exchanger according to claim 1, wherein

each of the tubes is constructed of a first tube member and a second tube member, and
the first main wall and the second main wall are included in the first and second tube members, respectively.

8. The heat exchanger according to claim 1, wherein each of the tubes has an inner fin in the first fluid passage.

9. The heat exchanger according to claim 2, further comprising:

a side wall member attached to longitudinal sides of the plurality of tubes, wherein
the side wall member has a bulge at a position corresponding to the first openings,
the bulge provides a clearance therein and encases the first openings,
the distributing portion is defined by the bulge, and
the inlet portion has a pipe shape and is in communication with the clearance provided by the bulge.

10. The heat exchanger according to claim 2, further comprising:

a side wall member attached to longitudinal sides of the plurality of tubes, wherein
the side wall member has a bulge at a position corresponding to the second openings,
the bulge provides a clearance therein and encases the second openings,
the collecting portion is defined by the bulge, and
the outlet portion has a pipe shape and is in communication with the clearance provided by the bulge.

11. The heat exchanger according to claim 9, wherein

the plurality of tubes includes an outermost tube stacked at an outermost side, the outermost tube provides an outermost tube wall,
the outermost tube wall has an end projection along its peripheral end, a first end recess and a second end recess recessed from an end of the end projection, the heat exchanger further comprising:
an outer wall member disposed along the outermost tube wall such that an end passage is defined by a space provided between the outer wall member and the outermost tube wall and surrounded by the end projection, wherein
the end passage is in communication with the second fluid inlet part and the second fluid outlet part through the first end recess and the second end recess, respectively.

12. The heat exchanger according to claim 11, further comprising:

a tank having a connecting wall and outer walls extending from opposite sides of the connecting wall, wherein
the tank is coupled to the plurality of tubes such that the outer walls are disposed along outermost tubes that are stacked at outermost sides, wherein
the outer wall member is included in at least one of the outer walls of the tank, and the side wall member is included in the connecting wall of the tank.

13. The heat exchanger according to claim 12, wherein the bulge extends over the outer walls of the tank.

14. The heat exchanger according to claim 1, further comprising:

at least one bypass tube defining a first fluid passage therein through which the first fluid flows and a thermal insulation area on its outer periphery, the bypass tube disposed in parallel to the plurality of tubes; and
a partition wall disposed between the tubes and the bypass tube to separate the thermal insulation area from an area where the second fluid flows.

15. The heat exchanger according to claim 14, wherein

the bypass tube has a main wall opposed to the partition wall,
the main wall of the bypass tube has a projection that projects toward the partition wall on its peripheral end and contacts the partition wall such that at least a part of the thermal insulation area is defined by a space provided between the main wall of the bypass tube and the partition wall and surrounded by the projection of the bypass tube.

16. The heat exchanger according to claim 14, wherein

one of the plurality of tubes, which is opposed to the partition wall, provides an opposed main wall opposed to the partition wall,
the opposed main wall has the projection, the first recess and the second recess, the projection projects toward the partition wall and is in contact with the partition wall such that a space is provided between the opposed main wall of the tube and the partition wall and surrounded by the projection of the tube, and
the space is in communication with the second fluid inlet part and the second fluid outlet part through the first recess and the second recess of the opposed main wall, respectively.

17. The heat exchanger according to claim 1, further comprising:

a first fluid inlet tank defining a first tank space and having an opening, the first fluid inlet tank coupled to the tubes such that first ends of the tubes are disposed in the opening of the first fluid inlet tank and the first tank space is directly in communication with the first fluid passages defined inside of the tubes,
a first fluid outlet tank defining a second tank space and having an opening, the first fluid outlet tank coupled to the tubes such that second ends of the tubes are disposed in the opening of the first fluid outlet tank and the second tank space is directly in communication with the first fluid passages defined inside of the tubes.
Patent History
Publication number: 20070193732
Type: Application
Filed: Feb 1, 2007
Publication Date: Aug 23, 2007
Applicant: DENSO Corporation (Kariya-city)
Inventors: Yuu Oofune (Anjo-city), Takayuki Hayashi (Nagoya-city)
Application Number: 11/700,985
Classifications
Current U.S. Class: Flow Passages For Two Confined Fluids (165/164)
International Classification: F28D 7/02 (20060101);