A semiconductor module has been extensively used in a power converter, such as an electrical system of a hybrid vehicle or an electrical vehicle. The semiconductor module configuring an energy-saving controller has a power semiconductor element for controlling a high current.
The heat generated by such a power semiconductor element when controlling a high current tends to increase especially as miniaturization and power boosting of the power semiconductor element advance. Therefore, a major problem is to cool a semiconductor module having a plurality of power semiconductor elements.
A liquid cooling cooler has conventionally been used in such a semiconductor module. The power semiconductor elements need to be cooled efficiently in order to improve the cooling efficiency of the semiconductor module. The liquid cooling cooler is designed in various ways to improve its cooling efficiency thereof, by increasing the flow rate of its refrigerant, shaping heat radiating fins (cooling body) into a shape to provide good heat-transfer efficiency, and increasing heat-transfer efficiency of materials configuring the fins.
Increasing the flow rate of refrigerant supplied to the cooler or adopting the fin structures providing good heat-transfer efficiency can easily increase a pressure loss of the refrigerant inside the cooler. Especially in a cooler that uses a plurality of heat sinks to cool a large number of power semiconductor elements, the pressure loss of the refrigerant is significant in a passage structure where refrigerant passages are connected in series. To reduce the pressure loss of the refrigerant, it is ideal to construct a cooler in which its cooling efficiency can be enhanced with a low refrigerant flow rate. However, adopting a new fin material for improving the heat-transfer efficiency of the fin material configuring the cooler can lead to increases in costs of the entire cooler.
In a recent cooler, a refrigerant introducing passage for introducing a refrigerant and a refrigerant discharge passage for discharging the refrigerant are arranged parallel to each other, and a plurality of heat sinks are disposed therebetween in a refrigerant circulation direction so as to be substantially perpendicular to the abovementioned passages (for example, Japanese Patent Application Publication No. 2001-35981, Japanese Patent Application Publication No. 2007-12722, Japanese Patent Application Publication No. 2008-205371, Japanese Patent Application Publication No. 2008-251932, Japanese Patent Application Publication No. 2006-80211, Japanese Patent Application Publication No. 2009-231677, Japanese Patent Application Publication No. 2006-295178). In this case, the refrigerant can flow parallel between fins configuring each heat sink, increasing the cooling performance per pressure loss and reducing the pressure loss of the refrigerant inside the passages, as shown in Japanese Patent Application Publication No. 2006-80211.
Japanese Patent Application Publication No. 2009-231677 describes a liquid cooling cooler in which the entire rear-side wall of the casing is smoothly inclined forward from the right-side wall toward the left-side wall and in which the cross-sectional area of the passage of the entrance header part decreases gradually from the cooling liquid entrance side toward the left-side wall (see the paragraphs [0024] and [0031] and FIG. 2). Japanese Patent Application Publication No. 2008-205371 describes a liquid cooling cooler in which the connection water paths for introducing and discharging a refrigerant are disposed on the same side surface of the module and in which each of the paths is disposed in a direction perpendicular to the fins without changing the cross-sectional areas thereof (see FIG. 1).
Japanese Patent Application Publication No. 2006-295178 describes a heat sink apparatus for use in a computer electronic device and the like. In this heat sink apparatus, the shape of the inflow guide plate extending toward the plurality of passages is configured so as to be inclined into the shape of a curve of a convex surface toward the plurality of passages, as it moves away from the inflow port. In addition, the cross-sectional area of the inflow guide part becomes small gradually from the inflow port. Moreover, the shape of the inflow guide plate is same as that of the inflow guide plate (see the paragraph [0030] and FIG. 6).
In the conventional cooling technologies, however, a drift distribution in which the refrigerant drifts away occurs due to the shapes of the heat sinks and refrigerant passages, the method for disposing the heater elements, or the shapes of the refrigerant introduction/discharge ports, etc. Such drift distribution caused in the conventional coolers disturbs the balance of the cooling performance. Therefore, a uniform and stable cooling performance cannot be accomplished. Another problem is that only the temperatures of heat generated in the semiconductor elements disposed opposing the refrigerant discharge port increase significantly, reducing the lives of the elements or damaging the elements.
As in the coolers disclosed in Patent Documents 6 and 7 in which the cross-sectional areas of the entrance header parts decrease gradually in a direction in which the entrance header parts extend, their flow rate distributions are improving, but the increase in the temperatures of the sections near the refrigerant introduction ports cannot be prevented.