JP2012017954A - Cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooler improved in loading performance to keep heat transferring performance even when a dimension is reduced, with respect to the cooler for cooling a heating element incorporated in a power control unit of a hybrid automobile.SOLUTION: In this cooler including a plurality of cooling tubes 6, refrigerant supply tubes 7 for supplying a cooling medium into the cooling tubes, and refrigerant discharge tubes 7' for discharging the cooling medium to the outside of the cooling tubes, the cooling tubes are respectively constituted of a partitioning plate 3, a pair of outer packaging members 2, 4 disposed in opposition to the partitioning plate, and a refrigerant flow channel 5 formed by disposing wave-like members 1 respectively between the partitioning plate and the outer packaging members, and at least the partitioning plate and the pair of outer packaging members are made of aluminized steel plate, and integrated by brazing.

Description

The present invention relates to a cooler for cooling a heating element used in a power control unit or the like mounted on a hybrid vehicle.

Automotive engines and precision equipment are equipped with coolers for cooling the engine and components that generate heat, and these coolers are used as an indirect cooling system that does not directly contact the refrigerant with the heating element. ing. The cooler incorporated in various apparatuses is indispensable for maintaining long-term performance stability of the apparatus. In the automotive field in particular, there is a strong tendency to switch from conventional gasoline-powered internal combustion engine-only systems to combined use with motors such as hybrid cars and electric cars, or motor-only engine systems as a countermeasure against global warming in recent years. It has become.

In a hybrid vehicle and an electric vehicle, a power control unit including a large-capacity inverter that performs bidirectional conversion between direct current power and alternating current power is installed to drive a motor. In this power control unit, since the semiconductor unit having the conversion function generates heat as shown in Patent Document 1, the semiconductor unit is indirectly cooled by installing and contacting cooling pipes on both sides of the semiconductor unit. It is a mechanism. This cooling pipe uses copper or aluminum as a material, and as shown in FIG. 1, a corrugated member 1, exterior members 2, 4 and a partition plate 3 obtained by processing these materials into a corrugated shape are brazed. This corrugated uneven portion serves as a flow path 5 through which the refrigerant body flows. Further, the refrigerant body is supplied from the refrigerant supply pipe 7 joined to both sides of the cooling pipe 6 and discharged from the refrigerant discharge pipe 7 ′ via the cooling pipe, The semiconductor unit is cooled by heat exchange.

Although it is a power control unit of such a mechanism, it is desired to reduce the size in order to further improve the mountability, and accordingly, the size of the cooler is also required to be reduced. As a method for reducing the size of the cooler, it can be considered to reduce the thickness of the partition plate forming the cooling pipe. However, when copper or aluminum, which is a material of the current product, is thinned, a problem occurs in brazing, which is a manufacturing process of a cooling pipe. As shown in FIG. 2, this brazing is performed by applying a brazing material 8 between the corrugated member 1, the exterior members 2, 4 and the partition plate 3, and between the partition plate 3 and the pair of exterior members 2, 4. In addition, two corrugated members 1 are installed, and heating and air cooling are performed in a state where the weight 9 is placed on the upper exterior member 2. In this brazing process, if copper or aluminum is thinned, the rigidity is lowered, and there is a concern that the partition plate 3 and the exterior members 2 and 4 are deformed during brazing. In addition, since copper is a rare metal, the price is likely to fluctuate and it is difficult to use in terms of cost.

JP 2009-261125 A

The present invention has been devised to solve such problems, and in the brazing process for manufacturing the cooler, the flow path is formed without deformation of the partition plate and the exterior member of the cooling pipe. An object is to provide a cooler using such a material.

In order to achieve the object of the cooler of the present invention, a plurality of cooling pipes, a refrigerant supply pipe for supplying a cooling medium to the inside of the cooling pipe, and the cooling medium are discharged to the outside of the cooling pipe. The cooling pipe includes a partition plate, a pair of exterior members disposed to face the partition plate, and a corrugated member between the partition plate and the exterior member. And at least the partition plate and the pair of exterior members are made of an aluminum-based plated steel plate and are integrated by brazing. Further, the aluminum-plated steel sheet may be obtained by performing aluminum-based plating on ordinary steel (SPCC or the like), or may be obtained by performing aluminum-based plating on stainless steel.

In the cooler of the present invention, aluminum-based plating obtained by performing aluminum-based plating on plain steel, stainless steel, or the like, which has higher yield stress at higher temperatures than copper or aluminum, on the constituent partition plate, exterior member, and corrugated member. Since a steel plate is used, the partition plate and the exterior member do not deform during brazing. In addition, it is possible to further prevent the partition plate from being deformed by using ordinary steel or stainless steel plated with aluminum as the corrugated member. In addition, because the surface is plated with aluminum, the same brazing material used for manufacturing coolers made of current aluminum can be used, so a special brazing material with no flowability can be used. Since there is no preparation, there is no increase in cost. From these effects, it is possible to secure a flow path of a predetermined dimension, and the cooler can be manufactured stably. The stainless steel used for the aluminum-based plated steel sheet may be an austenitic stainless steel or a ferritic stainless steel, but it is preferable to use a ferritic stainless steel that is excellent in cost. By using stainless steel, a cooler with excellent corrosion resistance can be obtained.

Concerning the cooler used in the power control unit, (a) overall configuration and (b) schematic diagram showing the structure of the flow path of the cooling pipe (cross section AA in (a)) The figure which shows the assembly process of the channel of a cooler Schematic of the channel structure of the cooler in the present embodiment

In order to reduce the size of the cooler, the present inventors have made various studies focusing on reducing the thickness of the partition plate, the exterior member, and the corrugated member. The partition plate, exterior member, and corrugated member of the current cooler are made of copper or aluminum, but when those parts are thinned, the partition plate, exterior member and It becomes difficult for the corrugated member to deform and to secure a flow path having a predetermined dimension. For this reason, the yield stress can be maintained at a relatively high level even under high temperatures of brazing, and the steel sheet is studied with a plated steel sheet in consideration of the bonding stability in brazing. Stainless steel was used. In this study, we proceeded in comparison with a material made of aluminum, which is relatively used as a cooler for power control units.

When brazing an aluminum-plated steel sheet, since the brazing material is an aluminum type, the melting point of the brazing material is about 600 ° C. Since plain steel and ferritic stainless steel, which are the base plates of aluminum-based plated steel sheets, maintain a yield stress of about 10 times or more compared to aluminum even at a high temperature of 600 ° C, if only rigidity is considered It is possible to reduce the thickness to about 1/10 of the thickness of the partition plate, exterior member, and corrugated member of the current cooler, and the thickness can be sufficiently reduced. However, in the case of ordinary steel and ferritic stainless steel, the heat conductivity of aluminum is about 1/3 and about 1/6 respectively, and considering the cooling capacity of the cooler, that is, heat transfer performance, It is necessary to reduce the thickness to about 1/3 or less of the aluminum plate thickness. Therefore, the limitation of thinning of ordinary steel and ferritic stainless steel depends on the heat transfer performance.

In order to examine the thickness of ordinary steel and stainless steel considering heat transfer performance, we compared the heat transfer performance by forming a channel with each material. Details will be described in the examples, but it has been found that the heat transfer performance is almost equivalent to 1/3 of ordinary steel and 1/6 of ferritic stainless steel with respect to the current thickness of aluminum. . Further, deformation during brazing did not occur, and a flow path with a predetermined dimension was secured.

When a cooler is manufactured using plain steel or stainless steel with aluminum plating on the surface, a partition plate, an exterior member, and a corrugated member are first prepared. The corrugated member 1 is cut into a required length after plastic processing of a plate-like or coil-like material into a corrugated shape of a predetermined size by pressing or rolling. The partition plate 3 and the exterior members 2 and 4 can also be obtained by forming a plate-shaped or coil-shaped material into a predetermined shape and size with a press or the like and cutting it into a predetermined length with a cutting machine or the like. Next, as shown in FIG. 2, a brazing material 8 is applied between the two corrugated members 1, the partition plate 3, and the exterior members 2, 4, and the weight 9 is placed on the upper exterior member 2 in this state. And fix. In that state, it can be produced by placing it in a heating furnace and heating and air cooling under predetermined brazing conditions.

The film thickness of the plating layer plated on the surface of the aluminum-based plated steel sheet is not particularly limited when the original plate is made of ordinary steel or stainless steel, but it can be used on one side in consideration of corrosion resistance and brazing. It is desirable to make it 5 μm or more.

In addition, the steel grades of ordinary steel and stainless steel, which are the base plates of the aluminum-based plated steel sheet, are not particularly limited, and any steel grade can be used as long as it has a deformation resistance component and mechanical properties that can be processed into a wave shape. be able to.

The test materials used were normal steel and ferritic stainless steel with aluminum plated on the surface, and the thickness of each plate was 0.1 mm and 0.07 mm. Thermal performance and deformation state during brazing were confirmed. The plating film thickness of the material is 5 μm on one side. As shown in FIG. 3, the flow path 5 of the cooling pipe 6 has a rectangular cross-sectional shape, a height Hp of 2 mm, and a width wp of 1 mm. Each material was pressed so as to have this flow path shape and dimensions, and cut into predetermined dimensions. The overall dimensions of the cooler are as shown in Table 1. Here, the length L is the distance between the centers of the refrigerant supply pipe 7 and the refrigerant discharge pipe 7 'as shown in FIG. The corrugated member 1, the partition plate 3, and the exterior members 2, 4 are joined by applying an Al—Si—Mg based brazing material to the partition plate 3, the exterior members 2, 4 to a thickness of 0.1 mm. A weight of 5 kg was placed on 2 and fixed. In this state, it was put into a vacuum heating furnace and brazed under the conditions shown in Table 2. Regarding the heat transfer performance of the cooler, water at a temperature of 20 ° C. is used as the coolant flowing in the cooler, and the water is supplied at a speed of 0.1 m / s, and from both sides of the partition plate 3 and the exterior members 2 and 4 to the entire surface. Heating was performed at a constant temperature of 100 ° C., and the temperature change of flowing water was measured to calculate the amount of heat removal. As a comparison, Al-Mn-based aluminum was used as an example of a material used in the current power control unit, and a cooler was also manufactured and evaluated for performance. The plate thickness was 0.4 mm and 0.1 mm, and the manufacturing method of the cooler and the evaluation of the heat transfer performance were the same as in the case of the aluminum plated steel plate.

As a result of manufacturing the cooler, when using an aluminum-plated steel sheet as a raw material, it is possible to obtain a flow path of a predetermined dimension without causing deformation during brazing, regardless of whether the original sheet is plain steel or ferritic stainless steel. did it. However, when Al—Mn-based aluminum is used as a raw material, deformation did not occur at the time of brazing at a plate thickness of 0.4 mm, but deformation occurred at a plate thickness of 0.1 mm to obtain a flow path of a predetermined dimension. I could not.

About heat transfer performance, the amount of heat removal is almost the same when using Al-Mn aluminum with a thickness of 0.4 mm and when using aluminum-plated steel sheet with plain steel or ferritic stainless steel as the raw material. It was also found that heat transfer performance can be maintained by reducing the plate thickness even when an aluminum-plated steel plate is used.

Claims (2)

In the cooler comprising a plurality of cooling pipes, a refrigerant supply pipe for supplying a cooling medium to the inside of the cooling pipe, and a refrigerant discharge pipe for discharging the cooling medium to the outside of the cooling pipe, the cooling pipe Is composed of a partition plate, a pair of exterior members disposed to face the partition plate, and a refrigerant flow path formed by arranging a wave-like member between the partition plate and the exterior member, and at least the partition The cooler, wherein the plate and the pair of exterior members are made of an aluminum-plated steel plate and are integrated by brazing. The cooler according to claim 1, wherein the aluminum-based plated steel sheet is obtained by performing aluminum-based plating on stainless steel.

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