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Aisin Seki develops new economic electric water cooling pump for automobiles

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.

  1. 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.

  2. 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.

  3. 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.



The gain in efficiency will benefit ICEVs, HEVs and PHEVs. Any mini step in increased efficiency is welcomed.

Roger Pham

The most important improvement is the elimination of the shaft seal of the conventional pulley-driven pump. The shaft seal is the weak link that usually fails at or even before 100,000 miles, require expensive repair job that involves removing the timing belt as well. With reliable electric components, the electric pump can be designed to last for the life of the engine and makes the engine more reliable.

However, electric pump requires a robust electrical system that typically is reserved for HEV's. Another advantage of an HEV is the lack of more weak links such as starter, alternator, failure-prone lead-acid battery, transmission, and mechanical brakes. Thus the increase in reliability of an HEV alone and the money saved in the repairs of all above weak links would justify the price premium. The saving in fuel cost of above $10,000-15,000 during the life of the HEV is pure bonus.

Roger Pham

Another weak link that I did not mentioned above would be the shaft seal of the typically pulley-drive A/C compressor in non-HEV that allows gradually leakage of Freon that eventually leads to the seizure of the A/C compressor. A HEV has an electric motor-driven A/C compressor that is hermetically sealed and thus Freon leakage thru the shaft is prevented. Expect the A/C compressor of an HEV to last the life of the car. Another huge potential saving in repair cost and maintenance cost.


All very good points RP. As more and more manufacturers shy/go away from mechanically driven accessories in favor of independent electric units, owners will gain in reliability and repair cost. That alone justifies electrified vehicles.

Will the old Lead battery have to be updated?


So now that the pump is no longer engine, why is it still mounted on the engine? Seems like they could take advantage and mount it somewhere more convenient and also de-clutter the engine which should make working on the engine easier

Roger Pham

If the electric water pump is to be mounted away from the engine, then there will need be 2-way piping running from the pump to the engine and then from the engine to the pump. THis will increase clutter, increase cost, and increase chance of leakage and failure, since the piping must be made from rubber to absorb the vibration from the engine. The pump could be mounted integrated with the radiator to reduce piping requirement, but then you will still need power cord to and from. Furthermore, the radiator is very thin, leaving you no with good location to mount the pump integrated with the radiator.

Thus, when the water pump is integrated with the engine, it does not require any extra piping, and can receive power directly from the alternator or generator, hence no extra wiring to and from the engine.


@ Roger,

it says "... the electric pump which is driven directly by its motor so these seals could be eliminated. Resin protects the electric motor parts from rust."

Does it mean that coolant, and not air, is between rotor and stator of the pump e-motor?
So it's not air-gap, but "water gap".

If it is the case, then it assumes smooth perimeter of rotor, i.e. without protruding pieces, like in switched reluctance motors, which are cheaper and more heat tolerant than PM motors.

What about bearings, are they also lubricated by the coolant (if there are no seals, coolant goes anywhere around moving parts)?

BTW, any idea how powerful those e-motors need to be for passenger cars.

Roger Pham

Current pulley-powered water pump including bearing is already lubricated by coolant.
The motors range from 100-300 watts of peak power. Actual power consumption during cruise will be a lot less. Electric pumps only run on-demand and not all the time like current pulley-powered water pump, so consume only a small fraction of engine's power devoted to pulley-powered pumps. A few percent gain in fuel economy is achieved with electric pump running on-demand basis, including faster warm-up.


I suppose the main thing is that you reduce the power on the ICE and move it to the battery.
This can be charged from deceleration etc, increasing the "electrification" of the car, without the need to go to a full hybrid.
Ideally, you could remove all the loads from the ICE except the motive power and alternator. And as much of the charging as possible could be done from deceleration/ braking, and when the engine is running in an efficient zone.

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