Heat sink

A heat sink includes a pipe through which cooled fluid flows and a cooling block having a first face on which the pipe is placed and a second face to which a heat emitting element is attached. The cooling block has a contact region and a noncontact region at positions where the cooling block faces the pipe. In the contact region, the first face contacts the pipe. In the noncontact region, the first face faces the pipe with a gap therebetween. The contact region is included in a projection region defined by projecting a region of attachment of the heat emitting element onto the first face.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Application No. PCT/JP2017/024348, filed on Jul. 3, 2017, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a heat sink including a pipe through which cooled fluid flows.

BACKGROUND

Heat sinks to cool an electronic part are known in the art. Such heat sinks known in the art include a heat sink including a pipe through which cooled fluid flows and a cooling block made of a heat conductive material (refer to, for example, Patent Literature 1). As disclosed in Patent Literature 1, the heat sink includes the cooling block having a placement groove and the pipe pressed against the groove, plastically deformed, and fitted in the groove with no gap therebetween to increase thermal conductivity. A cooling range of the heat sink including the cooling block and the pipe typically depends on the size of the cooling block and the area of contact between the pipe and the cooling block.

The heat sinks known in the art further include a heat sink that is disposed in an air-conditioning apparatus including a refrigerant circuit and cools an electronic part included in a controller by using refrigerant flowing through a pipe included in the heat sink (refer to, for example, Patent Literature 2). In the heat sink disclosed in Patent Literature 2, the flow rate of the refrigerant is adjusted by opening or closing a solenoid valve included in the refrigerant circuit. The electronic part can be kept at a target temperature if the heat sink has a low heat capacity.

PATENT LITERATURE

In the configuration of the heat sink in Patent Literature 1, excessive cooling may cause condensation to form in the vicinity of a heat-generating electronic part (hereinafter, referred to as a “heat emitting element”). A low heat capacity of the heat sink, as in Patent Literature 2, results in an increase in temperature undershoot and overshoot. This makes it difficult to keep the heat emitting element at the target temperature.

SUMMARY

The present invention has been made to solve the above-described problem and aims to provide a heat sink that certainly achieves cooling while preventing the formation of condensation.

A heat sink according to an embodiment of the present invention includes a pipe through which cooled fluid flows and a cooling block having a first face on which the pipe is placed and a second face to which a heat emitting element is attached. The cooling block has a contact region and a noncontact region at positions where the cooling block faces the pipe. The first face contacts the pipe in the contact region and faces the pipe with a gap therebetween in the noncontact region. The contact region is located within a projection region defined by projecting a region of attachment of the heat emitting element onto the first face.

In the heat sink according to the embodiment of the present invention, the noncontact region is also located at a position where the cooling block faces the pipe. This arrangement allows the cooling block to have a sufficient heat capacity. Additionally, the contact region is located within the projection region of the region of attachment of the heat emitting element. This arrangement reduces or eliminates excessive cooling in peripheral part of the cooling block. The heat sink according to the embodiment of the present invention thus cools the heat emitting element with certainty while reducing or eliminating the formation of condensation.

DETAILED DESCRIPTION

FIG. 1is a circuit diagram illustrating a heat sink1according to Embodiment 1 of the present invention disposed in an air-conditioning apparatus400. The air-conditioning apparatus400includes a heat source unit200and a plurality of load units300. The heat source unit200includes a compressor211, a flow switching device212, and a heat source side heat exchanger213. The heat source unit200further includes a controller and a temperature sensor7disposed at the controller.

The compressor211compresses and discharges refrigerant. The flow switching device212, which includes a four-way valve, switches between a refrigerant passage for a cooling operation and a refrigerant passage for a heating operation. The heat source side heat exchanger213, which exchanges heat between the refrigerant discharged from the compressor211and air, functions as a condenser in the cooling operation and functions as an evaporator in the heating operation.

The load units300each include a load side expansion device301and a load side heat exchanger302. Although two load units300are connected to one heat source unit200inFIG. 1, one or three or more load units300may be connected to one heat source unit200. The load side expansion device301, which includes an electronic expansion valve or a capillary tube, reduces the pressure of the refrigerant flowing from the heat source side heat exchanger213to expand the refrigerant. The load side heat exchanger302, which exchanges heat between the refrigerant reduced in pressure by the load side expansion device301and air, functions as an evaporator in the cooling operation and functions as a condenser in the heating operation.

The compressor211, the flow switching device212, the heat source side heat exchanger213, the load side expansion devices301, and the load side heat exchangers302are connected by refrigerant pipes, thus forming a main circuit210of the refrigerant circuit. Examples of the refrigerant used herein include water, fluorocarbon, ammonia, and carbon dioxide.

The heat source unit200includes a bypass220to cool a heat emitting element6included in the controller with the refrigerant. The bypass220includes a precooling heat exchanger222, a flow control device223, and the heat sink1. The precooling heat exchanger222is integrated with the heat source side heat exchanger213. A portion of the heat source side heat exchanger213is used as the precooling heat exchanger222. The precooling heat exchanger222cools the refrigerant diverted from the main circuit210. The flow control device223, which includes an electronic expansion valve having a variable opening degree, reduces the pressure of the refrigerant cooled by the precooling heat exchanger222to expand the refrigerant. The heat sink1cools the heat emitting element6of the controller with cooling energy of the refrigerant reduced in pressure by the flow control device223. The term “heat emitting element6” as used herein refers to a heat-generating electronic part of electronic parts included in the controller.

In the bypass220, the precooling heat exchanger222, the flow control device223, and the heat sink1are connected by a bypass pipe221. The bypass pipe221branches off from a high-pressure pipe401extending between the compressor211and the flow switching device212and connects to a low-pressure pipe402on a suction side of the compressor211. Although the flow control device223is disposed on an inlet side of the heat sink1inFIG. 1, the flow control device223may be disposed on an outlet side of the heat sink1. In a case where the flow control device223is disposed on the inlet side of the heat sink1, the refrigerant cooled by the precooling heat exchanger222is reduced in pressure by the flow control device223, so that the temperature of the refrigerant is lowered. Then, the refrigerant flows into the heat sink1.

The controller controls, for example, a frequency of the compressor211, switching of the flow switching device212, and an opening degree of each load side expansion device301. The controller includes a cooling control unit230that controls the opening degree of the flow control device223on the basis of the temperature of the heat emitting element6detected by the temperature sensor7. Specifically, the cooling control unit230performs control to open the flow control device223when the temperature of the heat emitting element6is at or above an upper temperature limit and close the flow control device223when the temperature of the heat emitting element6is at or below a lower temperature limit. For example, the upper temperature limit is set based on a heat resistance temperature of the electronic parts and the lower temperature limit is set based on a temperature at which condensation forms on the heat emitting element6.

High-pressure gas refrigerant discharged from the compressor211flows through the main circuit210and exchanges heat with the air in the load units300, thereby performing cooling or heating. When the temperature of the heat emitting element6rises to or beyond the upper temperature limit, the cooling control unit230performs control to open the flow control device223, so that part of the high-pressure gas refrigerant discharged from the compressor211flows into the bypass pipe221.

The high-pressure gas refrigerant flowing through the bypass pipe221is cooled into liquid refrigerant by the precooling heat exchanger222and is reduced in pressure by the flow control device223. Then, the refrigerant flows into the heat sink1. The liquid refrigerant that has flowed into the heat sink1absorbs heat generated from the heat emitting element6and thus turns into gas refrigerant. Then, the refrigerant flows into the bypass pipe221. The gas refrigerant leaving the heat sink1passes through the bypass pipe221and is then sucked into the compressor211. In this case, when the temperature of the heat emitting element6is at or above the upper temperature limit, the cooling control unit230causes the refrigerant to flow into the bypass220, thereby cooling the heat emitting element6. When the temperature of the heat emitting element6is at or below the lower temperature limit, the cooling control unit230keeps the refrigerant from flowing into the bypass220.

FIG. 2is a plan view illustrating a schematic configuration of the heat sink1according to Embodiment 1 of the present invention.FIG. 3is a side view of the heat sink1according to Embodiment 1 of the present invention with the heat emitting element6attached thereto.FIG. 4is a cross-sectional view taken along line A-A inFIG. 2.FIG. 5is a cross-sectional view taken along line B-B inFIG. 2. The configuration of the heat sink1will now be described in detail with reference toFIGS. 2 to 5.

The heat sink1includes a pipe2and a cooling block3. The pipe2is made of a heat conductive material, such as aluminum or copper. The pipe2is a U-shaped cylindrical pipe having a bend23, and has an inlet port21at one end and an outlet port22at the other end. The refrigerant flows through the pipe2from the inlet port21to the outlet port22in a direction represented by arrows F. The shape of the pipe2is not limited to the above-described U-shape. The pipe2may be, for example, a straight pipe, a serpentine pipe having bends23, or a pipe having branches extending between the inlet port21and the outlet port22.

The cooling block3has a first face4on which the pipe2is placed and a second face5to which the heat emitting element6is attached. The heat emitting element6is attached to central part of the second face5. The cooling block3is a plate-like part made of a heat conductive material, such as aluminum or copper, and conducts heat between the pipe2and the heat emitting element6. The longitudinal and lateral dimensions of the cooling block3are set to maintain a required heat capacity. The longitudinal and lateral dimensions are set so that the number of times that the flow control device223can be opened and closed in the life span of the heat sink1is less than or equal to an allowable number of times and a lifetime temperature cycle of the heat emitting element6lies within the bounds of not reducing the life of the heat emitting element6.

The first face4of the cooling block3includes contact regions Rj and noncontact regions Rs at positions where the cooling block3faces the pipe2. The first face4contacts the pipe2in the contact regions Rj and faces the pipe2with a gap therebetween in the noncontact regions Rs. The contact regions Rj are located within a projection region Rh defined by projecting a region of attachment of the heat emitting element6to the second face5onto the first face4.

As illustrated inFIG. 4, the contact regions Rj each include a placement groove41in which the pipe2is placed. The placement groove41has a depth D1relative to the first face4of the cooling block3in an arrow Z direction. The depth D1is the same dimension as, for example, an outer radius of the pipe2. The placement groove41has an arc cross-sectional shape to provide a sufficient area of contact with the pipe2. Although two placement grooves41are arranged inFIG. 2, the number of placement grooves is set depending on the plan-view shape of the pipe2disposed on the cooling block3. In the use of, for example, a serpentine pipe, three or more placement grooves41are arranged. In the use of, for example, a pipe having branches, the placement grooves41equal in number to the branches are arranged.

As illustrated inFIG. 5, the noncontact regions Rs are included in each recess42. The recess42has a depth D2relative to the first face4of the cooling block3in the arrow Z direction. The depth D2of the recess42is set greater than the depth D1of the placement groove41by a depth ΔD so that the pipe2is apart from the cooling block3. Furthermore, the recess42extends from an edge3aof the cooling block3to a position next to the placement grooves41in a direction (arrow Y direction) from the inlet port21or the outlet port22to the bend23of the pipe2.

For the extent of formation of each recess42in a direction (arrow X direction) perpendicular to the arrow Y direction in the first face4, the recess42may be formed within a region where the pipe2is located or may extend across the first face4of the cooling block3in the arrow X direction. The extent of formation of the recess42may be appropriately determined based on, for example, the required heat capacity and the ease of formation. Although two recesses42are arranged in the above description, it is only required that at least one recess42is formed. The number of recesses42and the position of the recess42may be appropriately set based on the position of the heat emitting element6and the position of the pipe2.

When the refrigerant flows into the heat sink1, cooling energy of the refrigerant is not transmitted to the cooling block3in the noncontact regions Rs where the pipe2is apart from the recess42. In the contact regions Rj where the pipe2is in contact with the placement grooves41, the cooling energy of the refrigerant is transmitted to the heat emitting element6through the pipe2and the cooling block3, so that the heat emitting element6is cooled. In the contact regions Rj, which are located within the projection region Rh, a distance D3between the pipe2and the heat emitting element6is shorter than those in other regions. Consequently, most of the cooling energy of the refrigerant is transmitted to the heat emitting element6, thus sufficiently cooling the heat emitting element6. In peripheral part3xof the cooling block3, a distance D4from the pipe2is longer than the distance D3. This avoids excessive cooling of the second face5of the cooling block3in the peripheral part3xto which the heat emitting element6is not attached, thereby reducing or eliminating the formation of condensation.

As described above, in Embodiment 1, the contact regions Rj in which the first face4is in contact with the pipe2and the noncontact regions Rs are arranged at the positions where the cooling block3faces the pipe2. The contact regions Rj are located within the projection region Rh defined by projecting the region of attachment of the heat emitting element6onto the first face4.

This arrangement allows the cooling block3to have a capacity in the noncontact regions Rs, thus providing a heat capacity greater than or equal to the required heat capacity. Furthermore, the area of cooling is limited within the projection region Rh. This avoids excessive cooling of the surface of the cooling block3in a region other than the region of attachment of the heat emitting element6. Therefore, the heat sink1cools the heat emitting element6with certainty while reducing or eliminating the formation of condensation. If an electronic part that generates no heat is attached to the peripheral part3xof the cooling block3, reduction or elimination of the formation of condensation on the peripheral part3xprevents a short in the electronic part that generates no heat. Additionally, the provided heat capacity of the cooling block3makes it easy to keep the heat emitting element6at a target temperature, resulting in a reduction in temperature undershoot and overshoot. This reduces the number of times of opening and closing of the flow control device223and suppresses a reduction in life of the heat emitting element6.

The contact regions Rj each include the placement groove41in which the pipe2is placed, and the noncontact regions Rs are included in the recesses42each having the depth D2greater than the depth D1of the placement groove41. In this arrangement, placing the pipe2in the placement grooves41increases the area of contact between the cooling block3and the pipe2, leading to increased thermal conductivity in the contact regions Rj. Although the placement grooves41are arranged, the gap between the pipe2and the cooling block3is provided in the recesses42. This facilitates arrangement of the contact regions Rj and the noncontact regions Rs in the cooling block3.

Each contact region Rj may include a plurality of placement grooves41. This arrangement allows the heat sink1to have the area of cooling and the contact regions Rj best suited to the heat emitting element6as long as the shape of the pipe2and the number of placement grooves41are set based on, for example, the amount of heat generated from the heat emitting element6and the position at which the heat emitting element6is attached.

Each recess42extends from the edge3aof the cooling block3to the position next to the contact regions Rj. The recess42is easy to form because the recess42is formed by cutting away a portion of the cooling block3in one direction. For example, the cooling block3ofFIG. 2is formed by cutting away portions extending from the edges3aof the cooling block3in the arrow Y direction. In addition, the recess42extending across the face in the arrow X direction is formed by cutting away a portion of the cooling block3in the arrow X direction.

FIG. 6is a plan view illustrating a schematic configuration of a heat sink101according to Embodiment 2 of the present invention.FIG. 7is a side view of the heat sink101according to Embodiment 2 of the present invention with heat emitting elements6aand6battached thereto. The heat sink101according to Embodiment 2 will be described with reference toFIGS. 6 and 7. The heat sink1according to Embodiment 1 cools one heat emitting element6, whereas the heat sink101according to Embodiment 2 cools the heat emitting elements6aand6b. The same components as those in Embodiment 1 are designated by the same reference signs and a description of these components is omitted.

The heat sink101includes a cooling block103having a second face105to which the heat emitting elements6aand6bare attached. A projection region Rha is a region defined by projecting a region of attachment of the heat emitting element6aonto a first face104. A projection region Rhb is a region defined by projecting a region of attachment of the heat emitting element6bonto the first face104.

The projection region Rha of the region of attachment of the heat emitting element6aincludes contact regions Rja. The projection region Rhb of the region of attachment of the heat emitting element6bincludes contact regions Rjb. The contact regions Rja have two placement grooves141, and the contact regions Rjb have two placement grooves141. The cooling block103has four placement grooves141in total. The number of placement grooves141in the contact regions Rja and Rjb may be set based on the plan-view shape of the pipe2on the cooling block103.

The first face104of the cooling block103has three recesses142, each including noncontact regions Rs. The placement grooves141each have the depth D1. The recesses142each have the depth D2, which is set greater than the depth D1of the placement grooves141by the depth ΔD so that the pipe2is apart from the cooling block103. The recesses142are arranged on opposite ends of the contact regions Rja and/or Rjb arranged for the heat emitting elements6aand6bin the arrow Y direction such that each of the recesses142is disposed next to the contact regions Rja or the contact regions Rjb. Specifically, the recess142, the contact regions Rja, the recess142, the contact regions Rjb, and the recess142are arranged in that order in a direction from an edge103aadjacent to the bend23to an edge103aadjacent to the inlet port21and the outlet port22.

As described above, in Embodiment 2, the contact regions Rja and Rjb are included in the projection regions Rha and Rhb for the heat emitting elements6aand6b. This arrangement allows the cooling block103to have a capacity in the noncontact regions Rs, thus providing a sufficient heat capacity if the heat emitting elements6aand6bare attached to the cooling block103. Furthermore, the area of cooling is limited within the projection regions Rha and Rhb, thus reducing or eliminating excessive cooling of the peripheral part3x. Therefore, the heat sink101cools the heat emitting elements6aand6bwith certainty while reducing or eliminating the formation of condensation as in Embodiment 1.

Embodiments of the present invention are not limited to the above-described embodiments. Various modifications can be made. For example,FIG. 1illustrates the heat sink1disposed in the air-conditioning apparatus400. The heat sink1may be disposed in any apparatus including a heat emitting element6. In the above description, the heat emitting element6is cooled with the refrigerant in the refrigerant circuit. The heat emitting element6may be cooled with any substance other than the refrigerant, for example, cooled fluid.

In Embodiment 1 described above, the cooling block3has the placement grooves41. As long as the cooling block3is in contact with the pipe2in the contact regions Rj, the placement grooves41may be eliminated. Furthermore, the pipe2and the cooling block3may be joined together by brazing or may be coupled together by caulking.

In the above description, the electronic part (heat emitting element6) that generates heat is attached to the heat sink1. In addition to the heat emitting element6, an electronic part that generates a little or no heat may be attached to the heat sink1. In this case, the electronic part that generates a little or no heat is attached to a noncontact region Rs or the peripheral part3x.

In the above description, the pipe2is a cylindrical pipe. A flat pipe may be used. In this case, each placement groove41is shaped to fit the cross-sectional shape of the pipe2. In the above description, the heat emitting element6is attached to the central part of the cooling block3. The heat emitting element6may be attached to any position on the cooling block3. The positions of the contact regions Rj and the noncontact regions Rs are set based on the position where the heat emitting element6is attached.