1. Field
The present invention relates to a pump used for a liquid-cooling type cooling system for cooling a heat generating unit.
2. Description of the Related Art
In recent years, improvement of information processing speed of an electronic apparatus such as a personal computer is remarkable, and the clock rate processed by a CPU (Central Processing Unit) or peripheral semiconductor devices for implementing such information processing is significantly increased in comparison with the related art.
In association with such a tendency, the heat release value of the CPU or other semiconductor devices increases correspondingly. Consequently, there exist semiconductor devices which cannot accommodate such an increased heat release value necessarily with a system in which a heat sink is thermally connected to the heat generating unit such as the CPU for cooling the heat sink with cooling air.
In order to cope with this problem, a technology to apply a liquid cooling type cooling system to a compact electronic apparatus such as a personal computer, which utilizes liquid as liquid coolant to obtain higher specific heat capacity than air and hence provides higher cooling efficiency, is developed.
For example, Patent Documents Jpn Pat. No. 3431024, Jpn Pat. No. 3452059, and Jpn Pat Publication No. 2003-172286 disclose a cooling system including a closed circular path for allowing liquid coolant to circulate, a heat discharger for discharging heat from the liquid coolant, and a pump for cooling the heat generating unit by pressurizing the liquid coolant for circulating the same in the closed circulating path and causing heat exchange between the liquid coolant and the heat generating unit by bringing the same into thermal contact with each other.
In the related art, the pump included a heat-receiving body for receiving heat by being brought into contact with the heat generating unit and a pump for circulating the liquid coolant which has received heat from the heat-receiving body, as separate independent components. In contrast to it, in the pump of this type, the pump is slimmed and downsized, and a pump case is used as a heat-receiving body, so that integrity of these components is realized.
In order to cool the heat generating unit such as a CPU with high level of cooling efficiency by circulating the liquid coolant, it is essential to strengthen thermal coupling between the heat generating unit such as the CPU and the heat-receiving body on the cooling system.
Therefore, the primary key point is to enhance heat conduction from the heat generating unit to the heat-receiving body. Therefore, the heat-receiving body is formed of a metallic material having high coefficient of heat conductivity, such as copper or aluminum.
For example, according to Jpn Pat. No. 3452059, copper or aluminum is used as a material for the pump case of the pump. Also, when aluminum is employed as the material for the pump case, copper having higher coefficient of heat conductivity than aluminum as an auxiliary heat conducting member is preferably provided between the heat generating unit and the pump case.
In this manner, it is extremely important to enhance the coefficient of heat conductivity of the pump case or the auxiliary heat conducting member joined thereto.
However, above described measure is not sufficient yet.
In general, the upper surface of the high-heat-generating semiconductor such as the CPU includes a square base board, and a metal square-plate-shaped member referred to as a heat spreader, which is slightly smaller than the base board. The heat spreader is intended to receive heat generated by the electronic device in the CPU, and to spread the same over the entire square surface of the spreader.
The portion of the high heat-generating semiconductor of the CPU which requires to be cooled (hereinafter referred to as “portion to be cooled”) is the heat spreader, and the base board exposed around the heat spreader is not necessarily required to be cooled. Heat must be received efficiently only from the limited area, which corresponds to the heat spreader.
Therefore, the second key point for enhancing thermal coupling between the heat generating unit such as the CPU and the heat-receiving body on the cooling system is to position the heat-receiving body adequately at the portion to be cooled on the heat generating unit.
In the cooling pump which also serves as the heat-receiving body, the position of the cooling pump must adequately positioned with respect to the portion to be cooled on the heat generating unit.
Jpn Pat. No. 3452059 discloses a technology to form the contact surface of the pump case formed of highly heat conductive material with respect to the heat generating unit into a shape complementary to the three-dimensional shape of the heat generating unit. It also discloses a technology to form the contact surface of the auxiliary heat conducting member into a shape complementary to the three-dimensional shape of the heat generating unit when the auxiliary heat conducting member having a high coefficient of heat conductivity is provided.
These technologies are intended to enhance heat conduction with respect to the heat generating unit (the first key point described above), and are not intended for positioning of the heat generating unit and the pump.