2024/05/23

Nissan Motor Co., Ltd. (Headquarters: Nishi-ku, Yokohama-shi, Kanagawa-ken; President: Makoto Uchida) held the company's “high EGR” at the “74th Automotive Technology Association Awards” hosted by the Japan Society of Automotive Engineers on the 23rd^*1“Development of a high corrosion resistant low wear piston seal system for internal combustion engines” and “development of a braking force control system for electric motor four-wheel drive vehicles” received technology development awards, and “Modeling of Direct Cooling Method with Forced Convection Boiling Induced Liquid Phase of Liquid Gas Two- Phase Refrigerant for Vehicle Traction Application PMSM(Proposal of a direct forced boiling cooling performance prediction model considering gas-liquid two-phase behavior of automobile drive motors)It was announced that” won the paper award.

The technologies, engineers, and reasons for receiving this award are as follows.

●Technology Development Award

・Award theme: Development of high corrosion resistance and low wear piston seal systems for high EGR internal combustion engines

・Winner: Hayato Hirayama (Nissan Motor Co., Ltd.)
Kakuzou Kaneko (Nissan Motor Co., Ltd.)
Takagi Yusuke (Nissan Motor Co., Ltd.)
Naoya Tainaka (Nissan Motor Co., Ltd.)
Shinohara Akio (Riken NPR Co., Ltd.)

・Reason for the award:
Coating on the surface of the piston ring (DLC) against wear between the pistol/bore due to foreign matter, which is also an important issue in next-generation internal combustion engines^*2) It was discovered that softening the hardness is effective, and the problem was solved. This technology is EGR^*2It is an achievement that can be applied to achieving a rate of 30% or more and expanding carbon-neutral fuels such as biofuels with severe corrosive environments, CO₂A significant contribution to the reduction can be expected.

＜Development background＞
In order to improve engine fuel efficiency, an increase in the EGR ratio is effective, but there is an issue where exhaust gas condensate causes cylinder bore corrosion. In order to address this issue, a stainless steel spray bore with chromium added to an iron-based material was developed, but wear due to foreign matter entering the contact surface of the piston ring with DLC, which is a sliding partner material, and the spray bore is an issue. In this development, by softening the spray film, a surface with reduced pores is formed to suppress oil consumption, and by lowering DLC film hardness, the ability to deform along foreign matter shapes is enhanced, and high abrasion resistance is achieved. The findings in this development are results that can be applied to achieving an EGR ratio of 30% or more and expanding carbon-neutral fuels such as biofuels with severe corrosive environments, and CO₂It was highly praised because it can be expected to make a significant contribution to the reduction.

・Award theme: Development of a braking force control system for electric motor four-wheel drive vehicles

・Winner: Ryozo Hirako (Nissan Motor Co., Ltd.)
Hiroshi Tsunehara (Nissan Motor Co., Ltd.)
Eigo Sakagami (Nissan Motor Co., Ltd.)
Tatsuya Suzuki (Nissan Motor Co., Ltd.)
Takeshi Katakura (Nissan Motorsports & Customization Co., Ltd.)

・Reason for the award:
Electric AWD^*3We have developed a technology that draws out the potential of cars and allows them to enjoy value not only in limited scenes, but also in driving and driving scenes in everyday life.

＜Development background＞
This control system assumes an electric AWD system with 2 electric motors mounted on the front and rear, and controls the movement of the vehicle by focusing on how humans feel that it is easy to drive and is comfortable to ride. Thus, the aim was to provide not only performance in scenes expected from conventional four-wheel drive vehicles, but also value that can be experienced in everyday use. In swivel acceleration scenes aimed at ease of driving, the balance of front and rear lateral forces while maintaining required acceleration is controlled by integrated control of the front and rear electric motors and the 4-wheel brakes, and the yaw moment generated from lateral force is stabilized, thereby drastically reducing the driver's correction steering amount. In acceleration/deceleration scenes aimed at a comfortable ride, the dynamism (rate of change in acceleration) and pitch angle are independently controlled with high response/high accuracy without using a variable mechanism of a mechanical suspension, and comfortable acceleration and deceleration without impairing the sense of acceleration is achieved. This technology draws out the potential of electric AWD vehicles and is a technology that can enjoy value not only in limited scenes, but also in driving/driving scenes in everyday life, and is thought to be one of the technologies for evolving electric drive vehicles rather than the evolution of four-wheel drive vehicles.

●Paper Award

・Award themes:
Modeling of Direct Cooling Method with Forced Convection Boiling Induction Liquid Phase Behavior of Liquid Gas Two-Phase Refrigerant for Vehicle Traction Application PMSM(Proposal of a direct forced boiling cooling performance prediction model considering gas-liquid two-phase behavior of automobile drive motors)

・Winner: Tatsuya Morimoto (Nissan Motor Co., Ltd.)
Kensuke Sasaki (Nissan Motor Co., Ltd.)
Takashi Kato (Nissan Motor Co., Ltd.)

・Reason for the award:
The coil occupancy ratio, which is the main design parameter of the motor, is dry-out^*4By elucidating what is one of the factors that cause the phenomenon, we have discovered knowledge that is the foundation of the design guidelines for vehicle motor boiling and cooling systems.

＜Research Background＞
Demand for high output density of drive motors is increasing in anticipation of further expansion of electrification. Since heat generation density increases due to high output density, improving cooling performance is key. Boiling cooling is being focused on as a solution, and elucidation of the dryout generation mechanism is important for application. In this paper, a structure in which in-slot coil heat is extracted during forced convection boiling cooling was assumed, and the correlation between in-slot coil occupancy ratio and dry-out occurrence was experimentally clarified, and the mechanism was elucidated. In particular, with regard to the mechanism, the correlation between coil occupancy ratio and refrigerant filling ratio was explained from the surface tension of the refrigerant, and a model was constructed to estimate the occupancy rate conditions that serve as the dryout occurrence boundary, and it was shown that it is well consistent with the experimental results. The fact that coil occupancy ratio, which is the main design parameter of motors, is one of the factors causing the dryout phenomenon is thought to have obtained knowledge that is the foundation of design guidelines for vehicle motor boiling and cooling systems, and this is a useful result.

*1 Exhaust gas recirculation; exhaust gas recirculation mechanism

*2 Diamond like carbon; a very hard, highly lubricated carbon film having both graphite and diamond properties

*3 All wheel drive

*4 A phenomenon where the cooling surface (coil surface) is covered with refrigerant vapor and cooling performance deteriorates

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