Laminated core type heat sink

In a laminated core type heat sink in which a plate is formed by arranging a plurality of slits in parallel to a metal flat plate and by laminating the plate in large numbers, the thickness of a second plate positioned second in the lamination direction from an end lid to which a semiconductor is attached is made greater than thickness of a first plate other than the second plate.

BACKGROUND OF THE INVENTION

The present invention relates to a device that is a laminated core type heat sink having a core obtained by laminating a plurality of plates, each plate being a metal flat plate with a plurality of punched out slits and a rib formed in a portion other than the slits, with end lids arranged and joined to both upper and lower ends thereof, and an element of any of various circuit boards such as an inverter is arranged to the end lid to as an object to be cooled by circulating a refrigerant in a meandering way into a flow path formed by slits of each plate.

The present applicant has already proposed a laminated type heat sink described in Japanese Patent Laid-Open No. 2014-33063.

In the heat sink, as shown inFIG. 11, slits1in parallel to each other are punched out for each metal flat plate, and, between these, a plurality of long and thin longitudinal ribs2in parallel to each other and transverse ribs3orthogonal to these are formed. Then, plates4adjacent mutually are laminated so that the longitudinal ribs2overlap with each other and the transverse ribs3are situated so as not to overlap in a circulation direction of a refrigerant7, to thereby form a core. Then, the refrigerant7circulates in a meandering way escaping from each transverse rib3of adjacent plates. In this laminated type heat sink, each of the plates has identical thickness.

SUMMARY OF THE INVENTION

In order to further improve a heat release performance, the present inventor made the flow state of a refrigerant visible, and checked temperature distribution of respective parts which changed in accordance with the increase in distance from the surface of respective parts of plate.

FIG. 6illustrates a flow state in a conventional laminated type heat sink. In the drawing, it was known that, in a plate4that contacted to an end lid9and most contributed to heat exchange, a swirling current was generated on a downstream side of the transverse rib3thereof. Furthermore, at this time as shown inFIG. 8, it was known that, when temperature distribution near the transverse rib3was measured on a downstream side of the plate4, the temperature distribution was high in a backwater region where the swirling current was generated with respect to the transverse rib3.

In the experiment, water was utilized as a refrigerant, temperature and flow rate of the water at an inflow port were set, respectively, to 65° C. and 10 L/min, a semiconductor element was attached on the end lid9as an object to be cooled, heat generation of 300 W was performed, and temperature distribution near the surface of the plate4contacting to the end lid9was checked to know that distribution inFIG. 8was generated.

That is,FIG. 8illustrates a range having temperature difference of not less than 72.25° C. in cross-section part of the water shown dotted (not less than 74° C.) and in cross-section part of the water shown cross-hatched (72.25° C. to 74° C.). The position where the flow stagnated and a swirling current was present inFIG. 6showed distribution with high water temperature and large thickness of the range of not less than 72.25° C.

That is, inFIG. 8, the part shown by dots near the surface of the plate4is at not less than 74° C., and the range of the part shown cross-hatched is at 72.25° C. to 74° C.

As is clear from the drawing, it was known that a distribution range at relatively high temperatures was broad on a downstream side of the plate4.

Consequently, the present invention aims at eliminating a stagnant region10on the downstream side of the transverse rib3arranged first from the end lid9and thinning as far as possible a temperature distribution region at high temperatures generated therein to accelerate heat exchange as a whole.

A first aspect of the present invention is a laminated core type heat sink, in which:

a plurality of flat plates is included, each flat plate being a metal flat plate having a plurality of slits (1) punched out in parallel to each other, and a plurality of long and thin longitudinal ribs (2) in parallel to each other and transverse ribs (3) linking respective adjacent longitudinal ribs (2), formed between the slits (1);

a core is included in which respective plates (4) are laminated while the longitudinal rib (2) is matched mutually and a position of the transverse rib (3) is shifted mutually, an end lid (9) is arranged to both ends in a lamination direction, and each of plates (4) is joined; and

a refrigerant is circulated into each of the slits (1) of the core in a longitudinal rib (2) direction, and an object (6) to be cooled is joined to an outer surface of the end lid (9),

wherein a plurality of first plates (4a) that has identical thickness and is adjacent to each other in a lamination direction, and a second plate (4b) that is arranged on the second in the lamination direction from the end lid (9) and is thicker than the first plate (4a) are included as the core.

A second aspect of the present invention is the laminated core type heat sink according to claim1, wherein (thickness T2of second plate (4b))/(thickness T1of first plate (4a))≥1.2 is satisfied.

A third aspect of the present invention is the laminated core type heat sink according to the first aspect, wherein the plurality of first plates (4a) having an identical planar shape is piled up to form the second plate (4b).

A fourth aspect of the present invention is the laminated core type heat sink according to any of the first to third aspects, wherein:

each of the plates includes a pair of manifold parts (5) positioned at both ends in a long side direction of the longitudinal rib (2) in the core and a frame part (13) surrounding the core and the manifold part (5); and

These are formed integrally with the core.

A fifth aspect of the present invention is a laminated core type heat sink, comprising:

a plurality of flat plates (4), the flat plate being a metal flat plate having a plurality of slits (1) punched out in parallel to each other, and a plurality of long and thin longitudinal ribs (2) in parallel to each other and transverse ribs (3) linking respective adjacent longitudinal ribs (2) formed between the slits (1), laminated so that the longitudinal ribs (2) are matched with each other and positions of the transverse ribs (3) are shifted from each other; and

a core in which respective plates (4) are joined and a casing (11) in a dish-like shape at least on one side in an inside of which the core is housed so that a pair of manifold parts (5) are formed at both ends in a long side direction of the longitudinal rib (2), in which a refrigerant is circulated in a longitudinal rib (2) direction into the each slit (1) of the core via the manifold part (5) and an object (6) to be cooled is joined to an outer surface of the casing (11),

wherein the core has a plurality of first plates (4a) that have identical thickness and is adjacent in a lamination direction to each other and a second plate (4b) that is arranged on a second in the lamination direction from the casing (11) and has greater thickness than the first plate (4a).

The sixth aspect of the present invention is the laminated core type heat sink according to the fifth aspect, wherein (thickness T2of second plate (4b))/(thickness T1of first plate (4a))≥1.2 is satisfied.

The seventh aspect of the present invention is the laminated core type heat sink according to the fifth aspect, wherein the plurality of first plates (4a) having an identical planar shape is piled up to form the second plate (4b).

The laminated core type heat sink of the present invention is characterized in that the core thereof has a plurality of first plate4athat is adjacent in an lamination direction to each other and has identical thickness, and that the thickness of a second plate4bpositioned on the second in the lamination direction from the end lid9has greater thickness than the first plate4a.

Consequently, flow of a refrigerant around the first plate4acontacting to the end lid9having an object6to be cooled is improved (from a conventional state inFIG. 6, changes into the state of the present invention inFIG. 5), and, as the distance from the surface increases, temperature distribution of a refrigerant rapidly decreases (from a conventional state inFIG. 8, changes into the state of the present invention inFIG. 7) to improve heat exchange performance.

In the laminated core type heat sink of the second aspect, when (thickness T2of second plate4b)/(thickness T1of first plate4a)≥1.2 is satisfied, heat exchange performance can surly be improved.

In the laminated core type heat sink of the third aspect, the plurality of first plates4ahaving an identical planar shape is piled up to form the second plate4b, and, therefore, no separate plate is necessary as the second plate4bto suppress the production cost.

As fourth aspect of the invention, by forming integrally a frame part13around a periphery of the longitudinal rib and transverse rib of each plate and performing lamination via the frame part13thereof, a casing part of the heat sink can be formed.

Meanwhile, each of laminated core type heat sinks having a configuration in which a casing is fit onto a core as in fifth to seventh aspects also exerts the effects of the first to third aspects.

DETAILED DESCRIPTION OF THE INVENTION

Next, embodiments of the present invention will be explained on the basis of the drawings.

The structure of each plate in the core portion of the heat sink of the present invention is the same as that inFIG. 11illustrating a conventional type heat sink, except for the thickness thereof. That is, a plurality of slits1in parallel to each other is punched out in a metal flat plate, and, between these, a plurality of longitudinal ribs2in parallel to each other and transverse ribs3linking the longitudinal ribs2adjacent to each other are arranged.

Meanwhile, the transverse ribs3of plates adjacent to each other are shifted in a circulation direction of a refrigerant. Then, the core part, in which respective plates are laminated while the longitudinal ribs2of respective plates are matched with each other and positions of the transverse ribs3are shifted from each other, is included, and respective plates are brazed and joined. Further, with respect to the longitudinal rib2and transverse rib3of these respective plates4, a frame part13is formed integrally via a manifold part5on the outer side of a portion in which the core part is formed, and, by laminating these frame parts13in the thickness direction, the casing part of the heat sink is formed.

Then, to both ends in the lamination direction of respective plates, a pair of end lids9are arranged. In addition, in this example, inlet/output pipes8are attached to one of the end lids9, which are communicated with the manifold5of each plate. Then, in the example, objects6ato6fto be cooled are stuck to the surface of the end lid9on the upper end side via an insulating film not illustrated. As an example, the object to be cooled is a semiconductor element such as an inverter. The output thereof is frequently different mutually. Then, via one of the inlet/outlet pipes8and manifolds5, a refrigerant7is circulated in a meandering shape in a width direction of the core. Then, heat generated from each of the objects6ato6fto be cooled is absorbed via the refrigerant.

Here, the characteristic of the present invention lies in the core portion in which plates are laminated.

The core includes a laminated body of a plurality of first plates4ahaving identical thickness, a second plate4bthat is arranged on the second inFIG. 2and has different thickness, and the end lid9. The thickness T1of all the first plates4ais identical, and the thickness T2of the second plate4barranged on the second from the end lid9is greater than T1. That is, T2>T1is established.

The flow of a refrigerant at this time is illustrated inFIG. 5.

Regarding the flow inFIG. 5, as compared with a conventional type inFIG. 6, a backwater is absent on the downstream side of the first plate4athat contacts to the end lid9and has the highest heat release effect in the flow direction of a refrigerant. It is presumed that this is based on the correlation between thicknesses of the first plate4aand second plate4b.

On the basis of it, fromFIG. 7, it is shown that a high temperature region of a refrigerant generated on the downstream side of the first plate4adecreases in the width as compared with the high temperature region of the conventional type heat sink inFIG. 8. In other words, it is known that, inFIG. 7, thickness of a refrigerant having temperature not less than 72.25° C. on the downstream side of the first plate4ais remarkably narrow as compared with the width thereof inFIG. 8illustrating a conventional type.

Meanwhile, also in the example, water is used as a refrigerant and water temperature at an inflow port is 65° C. A flow rate was set to 10 L/min, an object to be cooled was stuck on the end lid9, which was caused to generate heat of 300 W, and temperature distribution near the surface of the first plate4acontacting to the end lid9was checked. Consequently, in the drawing, the cross-section portion of the refrigerant abutting the surface of the first plate4a, shown by dots, is at not less than 74° C., and the cross-section portion shown by cross-hatching is at 72.25° C. to 74° C.

The ratio T2/T1at this time is 2.0.

Next,FIG. 9illustrates examples of comparison in which heat resistance of a heat sink of the conventional article and heat resistance of the heat sink of the present invention were compared for the respective objects6ato6fto be cooled inFIG. 1when respective ratios of the second plate4b/first plate4aregarding thicknesses thereof were changed. Meanwhile, the heat resistance here is a value expressing difficulty of temperature transmission, and means temperature rise per unit time and per quantity of heat generation, with a unit of ° C./W.

As known from the drawing, in each of the objects6ato6fto be cooled, heat resistance is smaller in the heat sink of the present invention than in a conventional article.

In the Example, a plate in which a linear longitudinal rib and transverse rib are linked has been explained. However, the same is applied even to a plate in which a slit and rib have a wave-like shape in a plane (see, for example, Japanese Patent Laid-Open No. 2010-114174).

FIG. 4illustrates another Example of the present invention, in which two first plates4ahaving an identical planar shape are piled up to form the second plate4b. Also in this way, the laminated core type heat sink shown by Example inFIG. 3can be manufactured. In the Example, a separate plate is unnecessary as the second plate4b, and, therefore, production cost can be suppressed.

Meanwhile, in the example, cooling water for cooling an engine was cooled with a radiator, which was then used as the refrigerant7. Further, another liquid can also be used instead of it.

Next, in the example, the object to be cooled is arranged to the end lid9on the upper face side inFIG. 1, but it may be arranged to the end lid9on the lower face side. Alternatively, an object to be cooled can also be arranged to both end lids. In a case where an object to be cooled is to be arranged to both upper and lower end lids, thickness of plates each arranged on the second from each end lid may be set to greater than that of other plates.

Next,FIG. 10illustrates yet another Example of the present invention. Different points between the Example and the example inFIG. 1are shapes of the first plate4aand second plate4b, and a shape of the end lid9. In the first plate4aand second plate4bin Example inFIG. 10, a manifold does not exist, and instead, the end lid is formed by a pair of dish-like casing11, in the inside of which the laminated core is interposed and a space for the manifold5is formed. Consequently, the width of each of the first plates4aand the second plate4bis formed narrowly by the space for the manifold5.

The present invention can be utilized for a laminated type heat sink that cools a semiconductor such as an inverter with a refrigerant.