|Aisin Seki electric water cooling pump installed in engine (red circle). © Aisin Seiki. Click to enlarge.
Aisin Seki Co., Ltd has developed a smaller, cheaper electric cooling pump through some effective efficiency optimisations. Cars traditionally use mechanical water cooling pumps, which have a flow rate dependent on the engine speed. Electric cooling pumps offer greater control over the water flow allowing significant fuel economies. However, electric pumps are traditionally much larger than their mechanical counterparts.
Among other features, the Aisin electric pump uses a newly shaped impeller to improve performance. In addition, the design positions the components so that both the motor efficiency and the centrifugal pump mutually benefit. The pump also uses fewer components, allowing it to occupy less space.
|Aisin Seki electric water cooling pump (connecting side). © Aisin Seiki. Click to enlarge.
With the efficiency improvements less heat is generated. The pump design also incorporates an aluminium enclosure, which acts as a heat sink, further easing the heat resistance requirements. The cost of the electric pump was reduced by using an inexpensive and heat resistant printed circuit board.
Background. Controlling the water flow in engine cooling systems has been identified as an effective approach to contributing to reduced fuel consumption. Following work to develop electric pumps for cooling inverters, Aisin Seki has now focused on automobile cooling systems. Electric pumps run independently of the engine speed, which allows greater control over the water flow and consequently reductions in fuel consumption.
Electric pumps should operate in the same part of the engine as mechanical ones. The main issue in attempting to substitute mechanical pumps with electric ones is size. Electric pumps tend to be much larger in order to achieve the same discharge flow rate.
Aisin Seki tackled a number of factors that impinge on the efficiency of electric pumps. These efficiency enhancements mean that the size of their pumps can be decreased. Three elements affect the overall efficiency of the electric pump: the driver, the motor and the pump itself, which generally has a low efficiency.
Improving pump efficiency. Optimizations to the shape of the impeller enabled more effective pumping operation. In addition, an operation point that mutually benefits the efficiency of pump and motor was identified. The pump is centrifugal. The operation point that allows maximum efficiency for the motor and pump differs, but a compromise was found.
Economizing on component parts. Mechanical pumps harness the engine’s power through a pump pulley connected to the engine crank. The rotation of the crank then drives the pump, which is connected to the pulley by a shaft. Mechanical seals on the shaft prevent leaking of the cooling water. On the contrary, the electric pump which is driven directly by its motor so these seals could be eliminated. Resin protects the electric motor parts from rust.
Cutting costs. The opportunity to economize on costs was exploited with the use of a cheaper print board. Although the heat resistance may be lower for the cheaper print board, the optimized efficiency of the electric pump reduces the heat generated. An aluminum enclosure was also incorporated, which acts as a heat sink, further reducing the level of heat resistance needed in the print board.