Casing structure innovation provides quiet and comfortable driving experience – Automotive seat ventilation blower motor

“What is the best blower motor for a seat ventilation system?” This was the question ASPINA’s CM-BU (Car Mechatronics Business Unit) Research and Development Department set out to answer when they started developing their new product.

Until around 2018, most automotive seat air conditioning systems blew out warm or cold air from the seat surface, by using a peltier element temperature control mechanism attached to the end of a blower motor. Initially, these seat air conditioning systems were mainly installed in luxury cars, but gradually they began to be installed in middle class cars as well, leading to intensified cost competition. Around the same time, the need to reduce electricity consumption increased due to the shift to EVs. In response to these changes, the method of blowing out warm air from the seat was replaced by the heated seat which warms the seat surface with electric heating wires, and instead of blowing out cold air, ventilation by drawing in the cold air from the air conditioner became increasingly popular.

For a blower motor to draw air in from the seat surface, it must have enough static pressure to overcome its flow resistance. In particular, flow resistance increases when a passenger sits on the seat, so a blower motor with low static pressure would not be able to draw air in from the seat surface and ventilate, and thus would not function as a seat air conditioner. Looking at the trends in the automotive industry, we know it has become essential for vehicles to be quieter for improved passenger comfort. At the same time, the space available for installing blower motors is decreasing as seats become more multifunctional and slimmer. In other words, there is a need for a quieter, more low-profile and compact blower motor while also maintaining its air flow.

Most conventional blower motors for seat ventilation are the single outlet type, which ASPINA also manufactures. However, one time, when testing our conventional model mounted on a seat, the CM-BU Research and Development Department chief engineer noticed a slight noise. Although it was at a level that would not cause any problems as a product, he thought “we can do better”. And so, the R&D chief engineer and his team decided to improve their seat ventilation blower motor, with the concept of making it quieter, more low-profile, more compact, while maintaining flow rate.

What the R&D chief engineer and his team developed, was a blower motor that reduces noise by blowing air out the back of the casing and has boosted static pressure from an added diffuser.

ASPINA's back outlet blower motor for automotive seat ventilation blows air out the back of the casing

After examining conventional products, the team found that the loudest noise generated by the blower motor was the wind noise emitted from the blower outlet. The most effective shape of the casing to reduce this wind noise, while simultaneously making the unit low-profile and compact, was to blow air out from the back. Noise measurements of this back outlet blower motor showed that it reduced noise by 7dB without passengers and 9dB with passengers, compared to the conventional single outlet type.

Noise measurement comparison of ASPINA's conventional and back outlet blower motor

However, although this back outlet structure is effective in reducing noise, it has the disadvantage that it does not generate enough static pressure due to P-Q characteristics, compared to the conventional sirocco fan + side outlet casing products. As mentioned above, static pressure is essential to draw air from the seat surface. The R&D team decided to make improvements to boost static pressure.

According to Bernoulli's principle, the energy of a fluid in steady flow can be expressed by 1. speed, 2. pressure, and 3. height, the sum of which is constant. In other words, the key to increasing the static pressure of a blower motor, is to slow down the air flow. Based on this principle, a diffuser was added to the casing to slow down the air that blows out. By converting part of the air speed into pressure, the R&D chief engineer and his team was able to close in on to the ideal P-Q characteristics for seat ventilation systems.

P-Q characteristics of a blower with and without a diffuser

When developing this blower motor, it was difficult to achieve low noise, low-profile, and compactness; all the while maintaining output. Generally speaking, there is a trade-off between low noise and small size and is difficult to achieve both. As EVs are expected to become increasingly popular, and since they carry a large number of batteries in the chassis section, the space under the seats tend to become smaller. Furthermore, seats have become multifunctional in recent years to improve passenger comfort, so the internal structure has become more complex, thus again, space within the seat is limited. ASPINA’s R&D team knew that it was essential for automotive OEMs and tier-1 companies that the blower motors they use are low-profile and compact.

ASPINA’s blower motor for seat ventilation systems was developed to achieve low noise with its back outlet structure, boosted pressure from its diffuser, and a low-profile, compact casing. All of this was made possible in a single product by thorough examination of various design parameters. As a result, our back outlet blower motors for seat ventilation systems are 15mm smaller in size compared to our conventional single outlet product, while maintaining static pressure.

Size comparison of ASPINA's conventional and back outlet blower motor